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Can one switch the DNA present in a sperm cell?

Can one switch the DNA present in a sperm cell?


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Can a donated sperm cell be stripped of its original owners DNA and be replaced with DNA of another person to make a biological child of a man who has low production in sperm?


Not with present technology. There is next to no cytoplasm in a sperm cell. You cannot suck out its nucleus. If your remove its nucleus, the whole thing will just collapses on itself.

As for you question of replacing nucleus?. One current technique (Intra-cytoplasmic sperm injection - ICSI) is to inject a single sperm of a man with low sperm count with minimal mobility directly into an oocyte. (Ie sperm that is so bad that they effectively cannot swim on their own)

Unfortunately there is some indication, that this technology has made an entire generation of sons, who have also inherited their father's low sperm count and limited mobility. And now have a higher than average chance of needing IVF assistance. https://www.newscientist.com/article/2108218-male-fertility-treatment-seems-to-pass-infertility-on-to-sons/


Can you fertilize one egg with 2 different men's sperm?

Also know, what happens when two sperm fertilize the same egg?

Fraternal twins are formed when two eggs meet two sperm in the womb. Each is fertilized independently, and each becomes an embryo. With identical twins, one egg is fertilized by one sperm, and the embryo splits at some later stage to become two.

Also Know, can two eggs fertilize each other? For two females to reproduce, taking the haploid DNA from one egg and using it to fertilize the other would seem like the most straightforward approach. Of course, with two females only female offspring would be possible (at least in the case of humans).

Keeping this in consideration, what happens when two sperm cells fuse with single ovum?

Answer: If two sperm cells are fused with the single ovum there will be a double fertilization Or Twins are born.

Can a baby have DNA from 2 fathers?

Superfecundation is the fertilization of two or more ova from the same cycle by sperm from separate acts of sexual intercourse, which can lead to twin babies from two separate biological fathers. The term superfecundation is derived from fecund, meaning the ability to produce offspring.


Sperm or egg? 'Genetic switch' determines germ cell fate


In a first, Japanese researchers have found a genetic switch in vertebrates that determines whether germ cells become sperm or eggs.

The gene is named foxl3, and has been identified in a small fish called medaka (Oryzias latipes).

Dr Toshiya Nishimura, Associate Professor Minoru Tanaka from the National Institute for Basic Biology, National Institutes of Natural Sciences in Japan and colleagues found that the foxl3 gene works in the germ cells of females "to suppress differentiation into sperm."

In females lacking functional foxl3 genes, the small fish's body appearance is still totally female, however a large number of sperm are formed in the ovaries, and a small number of eggs are formed at the same time.

"In spite of the environment surrounding the germ cells being female, the fact that functional sperm has been made surprised me greatly," Nishimura said.

"That this sexual switch present in the germ cells is independent of the body's sex is an entirely new finding," Nishimura said.

"While germ cells can become either sperm or eggs, nobody knew that in vertebrates the germ cells have a switch mechanism to decide their own sperm or egg fate," Tanaka said.

"Our result indicates that once the decision is made the germ cells have the ability to go all the way to the end. I believe it is of very large significance that this mechanism has been found," Tanaka said.


Materials and Methods

Reagents and Media

Unless otherwise stated, all chemicals and media were purchased from Sigma Chemical Co.

Animals, Gamete Collection, and Sperm Freezing

CD1 and B6D2F1 (C57BL/6 x DBA/2) mice (Harlan Iberica SL) were used as oocyte and sperm donors. Females were 6–8 wk old at the time of the experiments, and males were at least 3 mo old. CD1 females mated with vasectomized males were used as surrogate mothers for embryo-transfer experiments. Mice were fed ad libitum with a standard diet and maintained in a temperature- and light-controlled room (23°C, 14L:10D). In all experiments, pregnant dams were allowed to deliver spontaneously. The pups were nursed by their natural dams until weaning. To ensure standardized nutrition and maternal care, all litters were redistributed (or augmented with additional pups) on the day after birth to have litter sizes of six to eight pups. All animal experiments were performed in accordance with Institutional Animal Care and Use Committee guidelines and in adherence with guidelines established in the Guide for Care and Use of Laboratory Animals as adopted and promulgated by the Society for the Study of Reproduction.

Metaphase II oocytes were collected from the oviducts of 6- to 8-wk-old female mice superovulated with 7.5 IU of eCG and, 48 h later, with an equivalent dose of hCG. Briefly, at 14 h post-hCG administration, oviducts were removed from superovulated female mice and placed in an M2-containing Petri dish at room temperature. After washing, collected oviducts were placed in fresh M2 medium, and cumulus-oocyte complexes were released from the ampulla with the aid of Dumont #55 forceps. Cumulus-oocyte complexes were then moved either into a fertilization drop (for in vitro fertilization [IVF] experiments) or into a dispersion drop (for ICSI experiments). In ICSI experiments, cumulus cells were dispersed by a 3- to 5-min incubation in M2 medium containing 350 IU/ml of hyaluronidase after washing, oocytes were maintained in KSOM medium [ 26] at 37°C in an atmosphere of 5% CO2 in air until use. Fresh and frozen-thawed sperm were prepared essentially as described previously [ 26] with minor differences. Briefly, epididymal sperm from mature (3–6 mo old) males was collected in M2 medium by excising with a pair of fine scissors and compressing with forceps blood-free and adipose tissue-free epididymal cauda. Sperm cells collected in a minimal volume, to be frozen-thawed, were placed in the bottom of a 1.5-ml polypropylene centrifuge tube and overlaid with the volume of fresh medium necessary to obtain the final concentration of 2.5 million cells/ml. The sperm extender used did not contain cryoprotecting agents, such as EDTA or EGTA. Sperm samples were frozen in liquid nitrogen and stored for periods ranging from 1 day to 4 wk at −80°C. Asepsis was maintained throughout the procedure. Both fresh and frozen-thawed sperm were mixed with 40–50 μl of a 10% polyvinyl-pyrrolidone (PVP-360) in M2 solution before being placed in the culture dish for microinjection.

ICSI with Fresh and Frozen-Thawed Sperm

The ICSI with fresh and frozen-thawed spermatozoa was performed in M2 medium at room temperature [ 27]. One volume of sperm was mixed with five volumes of M2 medium containing 10% PVP to decrease stickiness. The ICSI dish contained a manipulation drop (M2 medium), a sperm drop (sperm solution in M2/10% PVP), and an M2/10% PVP needle-cleaning drop. Injections were performed with a PMM-150 FU piezo-impact unit (Prime Tech) and Eppendorf micromanipulators using a blunt-ended, mercury-containing pipette (inner diameter, 6–7 μm). Individual sperm heads either mechanically decapitated with the piezo unit (for fresh sperm) or by the freezing-thawing procedure were injected into oocytes. Oocytes were injected in groups of 10. After 15 min of recovery at room temperature in M2 medium, surviving oocytes were returned to mineral oil-covered KSOM and cultured at 37°C in an atmosphere of 5% CO2 air for up to 96 h. For embryo culture, 50-μl drops of KSOMaa medium were set up in a plastic culture dish, overlaid with mineral oil, and equilibrated overnight at 37°C in a humidified atmosphere of 5% CO2 in air. Oocytes were scored for male and female pronucleus formation (fertilization) at 6 h after the initiation of culture, and the number of 2-cell embryos was scored after 24 h in culture. For full term development, 2-cell embryos were transferred into oviducts of recipient pseudopregnant females. Embryo transfer was performed as described previously [ 26].

For the IVF experiments, oocytes were obtained from superovulated female mice as above. The methodology used has been described elsewhere [ 28]. In the IVF assays, 2.5–10.0 μl of fresh epididymal sperm was added to each fertilization drop to achieve a final concentration of ∼1–2 × 10 6 spermatozoa/ml. Four hours after oocyte and sperm coincubation at 37°C in a humidified atmosphere of 5% CO2 in air, oocytes were washed and cultured in KSOM.

Evaluation of Sperm DNA Fragmentation by TUNEL

An aliquot of each sperm sample was diluted to 10 6 cells per ml in PBS. Gelled aliquots of 0.8% low-melting-point agarose were aliquoted in Eppendorf tubes. Each Eppendorf tube was placed in a water bath at 90–100°C for 5 min to fuse the agarose and then maintained in a water bath at 37°C. After a 5-min incubation for temperature equilibration at 37°C, 60 μl of the diluted semen sample were added to the Eppendorf tube and mixed with the fused agarose. Twenty microliters of the semen-agarose mix were pipetted onto an agarose-precoated slide and then covered with a 22- × 22-mm coverslip. The slide was placed on a cold plate in the refrigerator at 4°C for 5 min to allow the agarose to produce a microgel with the sperm cells trapped within. Three different microgels, each corresponding to a sample from a different treatment, were simultaneously prepared and processed on the same slide. Fragmented DNA was nick-end-labeled with fluorescein isothiocyanate-conjugated dUTP using a terminal transferase (In situ Cell Death Detection Kit Roche Molecular Biochemicals) for 1 h at 37°C in the dark following the vendor's instructions. Positive controls were incubated in DNase I at 50 μg/ml for 20 min at 37°C and washed in PBS before TUNEL. Negative controls were incubated in fluorescein-conjugated dUTP in the absence of enzyme terminal transferase. After TUNEL, sperm cells were washed in PBS and treated with RNase (50 μg/ml) for 1 h at room temperature. Subsequently, the sperm cells were washed in PBS and nuclear stained by a 10-min incubation in PBS containing 20 μg/ml of propidium iodine. In the end of this incubation period, sperm cells were washed again in PBS, mounted on a glass slide with Vectashield (Vector), and examined under a fluorescence microscope. A total of 400 cells/sample were randomly analyzed. The proportion of sperm cells with fragmented DNA (labeled with an intense green nuclear fluorescence) was referred to as TUNEL (%).

Evaluation of Sperm DNA Fragmentation by Comet Assay

The DNA damage of spermatozoa was assessed by single-cell gel electrophoresis (comet assay). Analysis of the shape and length of “comet” tail, just like the DNA content in the tail, gives an assessment of DNA damage. Sperm suspension (30 μl) was diluted in low-melting-point agarose (70 μl, 1% w/v LMagarose). A 100-μl mixture of sperm-agarose was immediately pipetted onto agarose-coated slides (1% w/v normal-melting-point agarose). Samples were immersed in ice-cold lysing solution (Trevigen) supplemented with 40 mM dithiotreitol and proteinase K (200 μg/ml). Incubation was performed during 1 h at 37°C. After this step, slides were rinsed in distilled water three times (5 min each time) and incubated in electrophoresis neutral buffer (Tris-borate-EDTA, pH 8) for 20 min. Electrophoresis was then performed at 25 V and 300 mA for 7 min. Following electrophoresis, the slides were neutralized with Tris-HCl buffer (pH 7.4) for 5 min and rinsed in distilled water. Samples were stained with SYBR Green (Trevigen) and analyzed under an epifluorescence microscope (Optiphot-2 Nikon). Comets were analyzed using specialized SCG analysis software (CometScore, freeware version TriTek Corp). Tail length (μm), tail DNA (%), and tail moment were recorded for 100 cells/animal. The parameter that allowed us to describe extension of DNA damage was the tail moment, defined in this software as the product of the tail length and the fraction of DNA in the tail.

Embryo Gene Transcription Analysis

The quantitative RT-PCR methodology used the present study has been described elsewhere [ 29]. Briefly, poly(adenylate) RNA was extracted from four to five pools of 10 embryos using Dynabeads mRNA Direct Extraction KIT (Dynal Biotech) following manufacturer's instructions. After reverse transcription, the quantification of all gene transcripts was carried out by real-time quantitative RT-PCR. Experiments were conducted to contrast relative levels of each transcript and mouse histone H2afz in every sample. Genes analyzed were two retrotransposons (intracisternal-A particle [Iap] and murine endogenous retrovirus-L [Erv4]), an X-linked gene (hypoxanthine-guanine phosphoribosyltransferase [Hprt]), and six imprinting genes (CD 81 antigen [Cd81] solute carrier family 38, member 4 [Slc38a4] insulin-like growth factor 2 [Igf2], H19 mesoderm specific transcript/paternally expressed gene 1 [Mest], and the growth factor receptor-bound protein 10/maternally expressed gene 1 [Meig1]) [ 29]. The PCR quantification was performed using a Rotorgene 2000 Real Time Cycler (Corbett Research) and SYBR Green (Molecular Probes) as a double-stranded DNA-specific fluorescent dye. The method used for quantification of expression was the relative standard curve method [ 29]. Experiments were conducted to contrast relative levels of each transcript and mouse histone H2afz in every sample.

Quantification of Telomere Length

Average telomere length was measured from mouse sperm DNA using a real-time quantitative PCR method described previously [ 30]. Each of the epididymal sperm samples collected from 10 male mice (five CD1 and five B6D2F1) was divided in two aliquots: One was kept fresh, and the second was frozen without cryoprotectant directly in liquid nitrogen. Fresh and frozen-thawed samples were subjected to an osmotic stress by adding three volumes of H2O, and then samples were centrifuged for 10 min at 9000 × g to eliminate the pellet of spermatozoa. The supernatants were used for quantification of telomere length by real-time PCR performed a minimum of three times for each sample. The assay measures an average telomere length ratio by quantifying telomeric DNA with specially designed primer sequences and then dividing that amount by the quantity of a single-copy gene (Rplp0). The average of these ratios was reported as the average telomere length ratio. The primers used for RT-PCR are listed in Supplemental Table 1 (available online at www.biolreprod.org).

Percentage of fragmentation and mouse embryo development obtained with fresh and frozen-thawed sperm for the CD1 and B6D2F1 strains.

Strain cross . Percentage of TUNEL+ (5 replicates) * . Comet tail length (μM) * . Surviving oocytes/ injected (%) . Two-cell embryos transferred (%) . Live pups (% from transferred) . Surviving after 25 weeks (%) .
CD1 × CD1 (frozen) 24 ± 3 a 50.73 ± 9 a 501/772 (69) a 432 (86) 54 (13) a 46 (85) a
CD1 × CD1 (fresh) 7 ± 4 bc 33.54 ± 8 b 101/111 (91) b 72 (71) 19 (26) b 19 (100) b
B6D2 × B6D2 (frozen) 16 ± 6 ab 48.03 ± 7 a 327/396 (83) ab 274 (84) 52 (19) ab 47 (90) ab
B6D2 × B6D2 (fresh) 4 ± 4 c 27.9 ± 8 b 73/104 (70) a 60 (82) 16 (27) b 16 (100) b
Strain cross . Percentage of TUNEL+ (5 replicates) * . Comet tail length (μM) * . Surviving oocytes/ injected (%) . Two-cell embryos transferred (%) . Live pups (% from transferred) . Surviving after 25 weeks (%) .
CD1 × CD1 (frozen) 24 ± 3 a 50.73 ± 9 a 501/772 (69) a 432 (86) 54 (13) a 46 (85) a
CD1 × CD1 (fresh) 7 ± 4 bc 33.54 ± 8 b 101/111 (91) b 72 (71) 19 (26) b 19 (100) b
B6D2 × B6D2 (frozen) 16 ± 6 ab 48.03 ± 7 a 327/396 (83) ab 274 (84) 52 (19) ab 47 (90) ab
B6D2 × B6D2 (fresh) 4 ± 4 c 27.9 ± 8 b 73/104 (70) a 60 (82) 16 (27) b 16 (100) b

Different superscript letters indicate significant differences within a column (P < 0.05), One-way Anova.

Percentage of fragmentation and mouse embryo development obtained with fresh and frozen-thawed sperm for the CD1 and B6D2F1 strains.

Strain cross . Percentage of TUNEL+ (5 replicates) * . Comet tail length (μM) * . Surviving oocytes/ injected (%) . Two-cell embryos transferred (%) . Live pups (% from transferred) . Surviving after 25 weeks (%) .
CD1 × CD1 (frozen) 24 ± 3 a 50.73 ± 9 a 501/772 (69) a 432 (86) 54 (13) a 46 (85) a
CD1 × CD1 (fresh) 7 ± 4 bc 33.54 ± 8 b 101/111 (91) b 72 (71) 19 (26) b 19 (100) b
B6D2 × B6D2 (frozen) 16 ± 6 ab 48.03 ± 7 a 327/396 (83) ab 274 (84) 52 (19) ab 47 (90) ab
B6D2 × B6D2 (fresh) 4 ± 4 c 27.9 ± 8 b 73/104 (70) a 60 (82) 16 (27) b 16 (100) b
Strain cross . Percentage of TUNEL+ (5 replicates) * . Comet tail length (μM) * . Surviving oocytes/ injected (%) . Two-cell embryos transferred (%) . Live pups (% from transferred) . Surviving after 25 weeks (%) .
CD1 × CD1 (frozen) 24 ± 3 a 50.73 ± 9 a 501/772 (69) a 432 (86) 54 (13) a 46 (85) a
CD1 × CD1 (fresh) 7 ± 4 bc 33.54 ± 8 b 101/111 (91) b 72 (71) 19 (26) b 19 (100) b
B6D2 × B6D2 (frozen) 16 ± 6 ab 48.03 ± 7 a 327/396 (83) ab 274 (84) 52 (19) ab 47 (90) ab
B6D2 × B6D2 (fresh) 4 ± 4 c 27.9 ± 8 b 73/104 (70) a 60 (82) 16 (27) b 16 (100) b

Different superscript letters indicate significant differences within a column (P < 0.05), One-way Anova.

Embryo Epigenetic Analysis by 5-Methylcytosine Immunodetection and Methylation-Specific PCR by Bisulfite Analysis

Three hours after ICSI or IVF, five fertilized oocytes were processed every hour for 5-methylcytosine immunodetection. Fertilized oocytes were washed in PBS, fixed for 15 min in 4% paraformaldehyde in PBS, and permeated with 0.2% Triton X-100 in PBS for 15 min at room temperature. Subsequently, oocytes were treated with a 2 M HCl solution at room temperature for 30 min and later neutralized for 10 min with 100 mM Tris-HCl buffer (pH 8.5). After several washes with 0.05% Tween 20, embryos were placed for 1 h in a blocking solution containing 2% BSA/0.05% PBS-Tween 20. Methylated DNA was visualized with a mouse monoclonal antibody against 5-methylcytosine (Calbiochem NA81). Samples were incubated with this antibody at 37°C for 1 h (1:100 dilution in PBS-2% BSA) and washed with 0.05% PBS-Tween 20 for 30 min. Subsequently, samples were incubated for 1 h at room temperature with a fluorescein isothiocyanate- or sulfonated indocyanine dye three-conjugated anti-rabbit secondary antibody (Jackson ImmunoResearch). After several washes in 0.05% PBS-Tween 20, samples were chromatin-labeled for 30 min with 20 μg/ml of propidium iodine, submitted to ribonuclease A treatment (1 mg/ml at 37°C for 1 h), and washed again with 0.05% PBS-Tween 20. Samples were mounted in 50% glycerol in PBS. Image analysis was carried out by measuring the level of fluorescence under a Nikon epifluorescence microscope (Optiphot-3). Images were recorded digitally with a high-resolution camera and were processed and analyzed using the Adobe Photoshop plug-in Image Processing Tool Kit 5.0 (Reindeer Games).

For the methylation-specific PCR by bisulfite analysis, the isolated DNA was treated with sodium bisulfite using the EZ DNA Methylation Kit (Zymo Research). Bisulfite-modified DNA was amplified by PCR. The methylated status of Iap long-terminal repeats (LTRs GenBank accession no. M17551) was examined using the following primers: IAP-F1, 5′-TTGATAGTTGTGTTTTAAGTGGTAAATAAA IAP-R1, 5′-CAAAAAAAACACCACAAACCAAAAT IAP-F2, 5′-TTGTGTTTTAAGTGGTAAATAAATAATTTG and IAP-R2, 5′-AAAACACCACAAACCAAAATCTTCTAC. The methylated status of Erv4 LTRs (GenBank accession no. Y12713) was examined using the following primers: RVL-F1, 5′-GTTATTATGTGATTTGAATTA RVL-R1, 5′-ACATACAAAACCATCAATAAAC RVL-F2, 5′-TTTATTATGAGTTGGGTAT and RVL-R2, 5′-ATAAACCAAACTCTAATCTTC. The methylated status of H19 (GenBank accession no. U19619) was examined using the following primers: H19-F1, 5′-GAGTATTTAGGAGGTATAAGAATT H19-R1, 5′-ATCAAAAACTAACATAAACCCCT H19-F2, 5′-GTAAGGAGATTATGTTTATTTTTGG and H19-R2, 5′-CCTCATTAATCCCATAACTAT. The PCR conditions for the three markers were as follows: first PCR (30 cycles), F1/R1 second PCR (30 cycles), F2/R2. Temperature conditions for the first PCR were as follows: 94°C for 3 min, 94°C for 20 sec, and 53°C for 30 sec. Temperature conditions for the second PCR were as follows: 94°C for 3 min, 94°C for 20 sec, 60°C for 30 sec, 72°C for 30 sec, and 72°C for 5 min. The PCR products were purified from agarose gels using ELU-QUIK DNA purification kit (Schleicher & Schuell) and transformed into XL1 Escherichia coli cells. Positive clones were verified by restriction enzyme analysis, and their products were sequenced using standard methods.

Behavioral Studies

Particular aspects of the behavior of adult CD1 and B6D2f1 mice generated by ICSI with frozen-thawed sperm and controls were evaluated with the open-field test, the elevated plus maze paradigm, and the free-choice exploration paradigm in Y maze as described previously [ 29] and in Supplemental Table 2 (available online at www.biolreprod.org). They were measured at both 3–4 and 13–15 mo of age. Particular attention was taken to analyze habituation responses, as previously described. [ 29]. All tests were performed by trained technicians in blind trials. The devices used for all behavioral studies were carefully cleaned with a diluted acetic acid solution between animals to prevent olfactory cues.

Postnatal Growth and Histological Analysis of Aged Animals

After weaning, mice were weighed weekly until 10 wk of age and then biweekly thereafter. Twenty months after birth, some viscera, including liver, lung, heart, kidney, spleen, and testes, were excised, and body/organ weights were measured. In addition, histopathological analysis was done. Samples (of liver, lung, heart, kidney, and spleen) were fixed in 10% buffered formalin and embedded in paraffin wax. Sections (thickness, 4 μm) were stained with hematoxylin-eosin and Congo red and then examined under the microscope. Stained sections of each tissue were reviewed by an experienced pathologist. Systolic blood pressure was determined at 12 mo of age by tail-cuff plethysmography using an NIPREM model 546 blood pressure monitor (Cibertec) after 1 h of acclimatization using data-acquisition software and hardware (Powerlab AD Instruments) following the manufacturer's instructions. Recordings (n = 3 on average) were blind to animal code.

Data Analysis

The mean telomere lengths were compared using an independent samples t-test. Data regarding postnatal growth and organ weight were analyzed using the SigmaStat software package (Jandel Scientific). One-way repeated-measures ANOVA (followed by multiple pair-wise comparisons using the Student-Newman-Keuls method) was used for the analysis of differences in weight. Differences of P < 0.05 were considered to be significant. Significance of the effects of behavioral analysis was assessed by a one-way ANOVA or a multivariate ANOVA with a Bonferroni or Newman-Keul test for post-hoc analysis. Factor analysis included culture conditions, sex, novelty/familiarity, and time points. The Student t-test was used for comparisons between two groups. Nonparametric data were analyzed by chi-square test. Behavioral analysis was processed by using the SPSS v.12 program.


Abstract

Epigenetic alterations in the germline can be triggered by a number of different environmental factors from diet to toxicants. These environmentally induced germline changes can promote the epigenetic transgenerational inheritance of disease and phenotypic variation. In previous studies, the pesticide DDT was shown to promote the transgenerational inheritance of sperm differential DNA methylation regions (DMRs), also called epimutations, which can in part mediate this epigenetic inheritance. In the current study, the developmental origins of the transgenerational DMRs during gametogenesis have been investigated. Male control and DDT lineage F3 generation rats were used to isolate embryonic day 16 (E16) prospermatogonia, postnatal day 10 (P10) spermatogonia, adult pachytene spermatocytes, round spermatids, caput epididymal spermatozoa, and caudal sperm. The DMRs between the control versus DDT lineage samples were determined at each developmental stage. The top 100 statistically significant DMRs at each stage were compared and the developmental origins of the caudal epididymal sperm DMRs were assessed. The chromosomal locations and genomic features of the different stage DMRs were analyzed. Although previous studies have demonstrated alterations in the DMRs of primordial germ cells (PGCs), the majority of the DMRs identified in the caudal sperm originated during the spermatogonia stages in the testis. Interestingly, a cascade of epigenetic alterations initiated in the PGCs is required to alter the epigenetic programming during spermatogenesis to obtain the sperm epigenetics involved in the epigenetic transgenerational inheritance phenomenon.


Can one switch the DNA present in a sperm cell? - Biology

On one hand, this is an important step forward in genetic engineering that will make it easier to develop farmed organs for transplant.

On the other hand, it’s fairly creepy as a technology and making genetic hybrids with farm animals is likely to ‘have issues’ such as moving animal diseases into human hosts.

On the third hand (hey, it could happen, and sooner than you think…) it shows a potential way for mammalian cells to do what bacterial cells do: swap DNA around.

Perhaps even ‘by accident’ in nature. In short, not all interspecies ‘hybrids’ need to be 50-50 mixes from two parents. Unlikely? Certainly. Impossible? Well… that remains to be seen.

Human genes in pig sperm for organ donors
Oct. 21, 2002 at 5:30 PM

MILAN, Italy, Oct. 21 (UPI) — Italian scientists said Monday by piggybacking human genes in pig sperm they have created swine that someday might help serve as life-saving donors for organ transplants to humans.
These new pigs have tissues better able to resist the human body’s immune rejection system. The research team hopes this will help improve “xenotransplantation,” or organ transfer across species.

Not a new release as it is dated 2002, but this is the first I’ve seen of it.

For the most part, scientists genetically modify animals by injecting DNA into eggs right after they are fertilized, a tricky and expensive operation. While this “microinjection” technique is fairly successful for mice, “it’s about 10 times less effective for livestock than mice,” Wall said. He suspects one reason is because scientists have bred lab mice to produce hardier eggs on average than livestock.

Since sperm are designed to deliver their DNA into eggs, Lavitrano and colleagues tried using sperm as gene carriers. In 1989, they reported sperm could absorb foreign DNA into specific places in their chromosomes.

I note that there is significant differences in how a given technique works between species, such as those mice being easier for the microinjection standard technique. This implies that any given species might have an easier time with any particular form of gene mixing.

But some other folks had trouble with reproducing their work, so they continued to work on the technique.

After much tinkering, Lavitrano said her team has now optimized the technique. “We’ve discovered what to do — how much DNA to use, when to give it, for how long, and in what condition,” she explained. “We do not need any of the expensive equipment, microscopes or anything, that you need with microinjection.”

Instead of extracting sperm cells from pigs or using frozen sperm, Lavitrano’s team coaxed two male pigs with healthy sperm to ejaculate. Such sperm are more mature, she said, and frozen sperm cell membranes are damaged. Unlike sperm extraction techniques, where pigs are then killed, Lavitrano added “we can use ejaculate for a long time.”

The semen fluid was washed off the sperm, since it protects them from absorbing DNA. The bottles of cleaned sperm then simply had DNA mixed with them for two hours, with scientists flipping the flasks upside-down every 20 minutes to keep the sperm from settling.

So the seminal fluid is the ‘barrier’ between a sperm cell and DNA absorption. Are all animal seminal fluids equally effective? Do all sperm react the same, even to other species seminal mix? Where I’m going with this is pretty simple. In many cases ‘in the wild’ there are cross species matings. Now mostly those do not produce viable offspring, some often they do. A genetic 50:50 mix of the nuclear DNA of the two species. But this method raises another potential pathway. DNA absorption.

So lets say a hypothetical rabbit hops onto an interested cat ( happens rather often… and perhaps occasionally with some result… look up cabbits ) and goes for it. Now even if nothing happens, lets say the sperm hang around for ‘a while’ and during that time a tomcat mates as well. Now there is the potential for some of the DNA from the rabbit to be absorbed into the cat sperm. Likely? Absolutely not or we would be up to our eyes in a variety of bizarre critters. But not impossible either. And that which is very unlikely but not impossible will happen with enough trials…

Perhaps this is how some of the unexpected bits of one type of DNA end up in seemingly too distant other species. As I’ve pointed out many times, the “species barrier” is more of a “species strong suggestion” and this shows that DNA absorption can happen at different points in the process. Not just via a virus picking up some environmental DNA and hauling it along ( known to happen ) but also potentially via other cells ‘sharing’ more than we expect from a perfect world ( as the world is not perfect ).

The scientists used the gene for human decay accelerating factor, or hDAF, a protein found on cell surfaces that protects cells from their body’s at-times misguided immune system. When eggs were fertilized with these modified sperm in vitro and implanted into mothers, 57 percent of the 93 piglets born had hDAF in their hearts, lungs, kidneys, ears and tails. DNA injection would have only led to a 0.5 to 4 percent success rate, Lavitrano said.

So with a wash, the rate of absorption is 57/93 or 61%. That’s impressively high. So if things are not ideal, does that drop to 1/1000 or 1/10000 or 1/1,000,000?

I strongly doubt it is perfect at 0/100,ooo,ooo …

In related news, we have somatic cells swapping DNA around.

Pig-human chimeras contain cell surprise

13:42 13 January 2004 by Gaia Vince

Pigs grown from fetuses into which human stem cells were injected have surprised scientists by having cells in which the DNA from the two species is mixed at the most intimate level.

It is the first time such fused cells have been seen in living creatures. The discovery could have serious implications for xenotransplantation – the use of animal tissue and organs in humans – and even the origin of diseases such as HIV.

The adult pigs that had received human stem cells as fetuses were found to have pig cells, human cells and the hybrid cells in their blood and organs.

“What we found was completely unexpected. We found that the human and pig cells had totally fused in the animals’ bodies,” said Jeffrey Platt, director of the Mayo Clinic Transplantation Biology Program.

A bit vague on some points, then again they likely don’t know what all happened. What was the chromosome number of the mixed cells? Was it a 50:50 mix, or just a few genes jumped over the fence?

The hybrid cells had both human and pig surface markers. But, most surprisingly, the hybrid cell nuclei were found to have chromosomal DNA that contained both human and pig genes. The researchers found that about 60 per cent of the animals’ non-pig cells were hybrids, with the remainder being fully human.

Importantly, the team also found that porcine endogenous retrovirus (PERV), which is present in almost all pigs, was also present in the hybrid cells. Previous laboratory work has shown that while PERVs in pig cells cannot infect human cells, those in hybrid cells can. The discovery therefore suggests a serious potential problem for xenotransplantation.

So in over 1/2 the cases of non-pig cells, the human line had fully blended with the pig line and made hybrid cells. (At least for the particular genetic marker they measured.) That’s a rather high rate. Also consider that many twins are from one fertilized egg splitting into two at an early stage of division. It is quite possible for one of those ‘hybrid cell’ clusters to be split off into a distinct embryo and not just a minor part of a chimera blend of cells. Can you say “That’s gonna be a problem”?

There is also that ‘issue’ with a pig-only virus making the leap to the hybrid cells (and then to human cells after a bit of mutation?)

This sort of thing is also why I’m against broad introduction of GMO foods. The GMO is typically made using techniques that can cause a variety of unexpected genetic changes, then ‘survivors’ are propagated (baggage and all). They use a virus genome to drag the DNA into the cells, so that package is floating around in the mix. Then there’s a ‘locked on’ codon to make sure the trait is expressed no matter what. My question has just been “What happens when digestion breaks down parts of those cells, and all those bits of GMO Machinery are sloshing around in the gut?” What bacteria or other cells does it start changing and inserting things into? No, not 100% of the time. Maybe only 1 in 100,000. But if 1,000,000,000 people are eating that stuff, you have 10,000 ‘with issues’… We simply do not know what will happen. (There have been some changes shown in bacteria and in some gut linings some times, so something happens.) Personally, I’d rather not have bits of ‘BTtoxin making genes’ floating around in my gut for bacteria or my gut lining cells to pick up, since it is shown to be an allergen.

In Conclusion

Nature is not very ‘tidy’ about genetic material. At the bacterial level, it’s a flat out free for all with plasmids moving chunks of DNA around between all sorts of species. Now we’re seeing that even at the level of mammal cells some amount of DNA swapping happens, and in a variety of contexts.

In some ways we really “are what we eat” and it really is true that all life is connected. I’d just rather not be too connected to things without my approval.

Nature. 2014 Oct 9514(7521):181-6. doi: 10.1038/nature13793. Epub 2014 Sep 17.

Artificial sweeteners induce glucose intolerance by altering the gut microbiota.

Suez J1, Korem T2, Zeevi D2, Zilberman-Schapira G3, Thaiss CA1, Maza O1, Israeli D4, Zmora N5, Gilad S6, Weinberger A7, Kuperman Y8, Harmelin A8, Kolodkin-Gal I9, Shapiro H1, Halpern Z10, Segal E7, Elinav E1.
Author information

Abstract
Non-caloric artificial sweeteners (NAS) are among the most widely used food additives worldwide, regularly consumed by lean and obese individuals alike. NAS consumption is considered safe and beneficial owing to their low caloric content, yet supporting scientific data remain sparse and controversial. Here we demonstrate that consumption of commonly used NAS formulations drives the development of glucose intolerance through induction of compositional and functional alterations to the intestinal microbiota. These NAS-mediated deleterious metabolic effects are abrogated by antibiotic treatment, and are fully transferrable to germ-free mice upon faecal transplantation of microbiota configurations from NAS-consuming mice, or of microbiota anaerobically incubated in the presence of NAS. We identify NAS-altered microbial metabolic pathways that are linked to host susceptibility to metabolic disease, and demonstrate similar NAS-induced dysbiosis and glucose intolerance in healthy human subjects. Collectively, our results link NAS consumption, dysbiosis and metabolic abnormalities, thereby calling for a reassessment of massive NAS usage.

So here we have artificial sweeteners changing our gut bacteria in such a way that they induce us to become fatter (and drink more artificial sweetener soda…) and transferring those bacteria to a new host makes it fatter too.

So why the “obesity epidemic” and the “diabetes epidemic”? Perhaps the millions of tons of artificial sweetener used in this country and the way it changes our metabolism and that of our bacterial content. (Burger and fries not so much the problem.)

Is this via a genetic mechanism? Well, likely not via any direct DNA change, but epigenetics might well enter into it. At some point all life chemical actions are genetic driven via protein & RNA synthesis, so it will be turning on some genes or turning off others. Then that pattern can be transplanted with the bacterial population.

The point of all this isn’t just that you ought to drop the artificial sweeteners from your diet. It is to point out that life adapts. In many ways, and often. Any change you make has a large potential impact, so watch such changes closely and do not accept them lightly. Also realize that in the wild, all sorts of changes are going on all the time, and life adapts. Not just by point mutations in a DNA strand (that are actually one of the slower ways to adapt) but via many kinds of DNA swapping ( the fastest being that every species with two sexes swaps DNA at every new individual. We are all a ‘new mix’ so that diseases have trouble ‘locking on’ to how to make us sick.) In that context, the idea that some DNA might move between species via sperm picking it up after a cross species dalliance, or via interspecies hybrids, is not “alien” or “against nature”. It is right in line with the desire of cells to ‘mix up the genes’ and see what happens or see if they can find a ‘new mix’ that stops some infections or parasites.

So be careful what you eat and who you hang around with… ( Gee, I think my Mom said that…) there’s a whole lot of ‘sharing’ going on.


2 Answers 2

I am not sure where these numbers come from and the answer depends on how you encode the genome data and if you define all the redundancy (unnecessary, repetitive data) as "information".

First of all, the humane genome contains somewhere around 3.1 (men) to 3.2 (women) billion base pairs. Since the X chromosome is three times longer than the Y chromosome, women have a higher total genome length than men.

A base pair is made of two of the four nucleobases adenine, cytosine, guanine and thymine, but only the four combinations AT, TA, CG and GC are possible as the A and T nucleobases won't bond with the C and G nucleobases and vice versa. These four combinations can be encoded with two bits, so that 6.2-6.4 gigabits or about 750 megabytes are required to store an exact copy of the genome.

Now, even if you need 750 megabytes to store the "raw data" from a human genome, at least a computer scientist will have a hard time defining all of this as "information". E.g. if you record 74 Minutes of complete silence on a CD, the disc contains roughly 750 megabytes of "data" as well, but actually no "information". Large parts of the human genome are repetitive, only a very small part actually differ between different individuals and from the difference, several base pair sequences only occur in a few well-defined varieties.

There is actually some research in the field "how to store a human genome as compact as possible", since genome databases most likely are going to expand rapidly and scientists need efficient ways to share data. Some tools are available for this purpose, e.g. DNAzip, which using a

5 gigabyte dictionary (permanent data) can compress a human genome down to roughly 4 megabytes.


Abstract

The incidence of Chlamydia infection, in both females and males, is increasing worldwide. Male infections have been associated clinically with urethritis, epididymitis, and orchitis, believed to be caused by ascending infection, although the impact of infection on male fertility remains controversial. Using a mouse model of male chlamydial infection, we show that all the major testicular cell populations, germ cells, Sertoli cells, Leydig cells, and testicular macrophages can be productively infected. Furthermore, sperm isolated from vas deferens of infected mice also had increased levels of DNA damage as early as 4 weeks post-infection. Bilateral vasectomy, prior to infection, did not affect the chlamydial load recovered from testes at 2, 4, and 8 weeks post-infection, and Chlamydia-infected macrophages were detectable in blood and the testes as soon as 3 days post-infection. Partial depletion of macrophages with clodronate liposomes significantly reduced the testicular chlamydial burden, consistent with a hematogenous route of infection, with Chlamydia transported to the testes in infected macrophages. These data suggest that macrophages serve as Trojan horses, transporting Chlamydia from the penile urethra to the testes within 3 days of infection, bypassing the entire male reproductive tract. In the testes, infected macrophages likely transfer infection to Leydig, Sertoli, and germ cells, causing sperm DNA damage and impaired spermatogenesis.


Measures of DNA content and chromosome content

The amount of DNA within a cell changes following each of the following events: fertilization, DNA synthesis, mitosis, and meiosis (Fig 2.14). We use &ldquoc&rdquo to represent the DNA content in a cell, and &ldquon&rdquo to represent the number of complete sets of chromosomes. In a gamete (i.e. sperm or egg), the amount of DNA is 1c, and the number of chromosomes is 1n. Upon fertilization, both the DNA content and the number of chromosomes doubles to 2c and 2n, respectively. Following DNA replication, the DNA content doubles again to 4c, but each pair of sister chromatids is still counted as a single chromosome (a replicated chromosome), so the number of chromosomes remains unchanged at 2n. If the cell undergoes mitosis, each daughter cell will return to 2c and 2n, because it will receive half of the DNA, and one of each pair of sister chromatids. In contrast, the 4 cells that come from meiosis of a 2n, 4c cell are each 1c and 1n, since each pair of sister chromatids, and each pair of homologous chromosomes, divides during meiosis.

Figure (PageIndex<14>): Changes in DNA and chromosome content during the cell cycle. For simplicity, nuclear membranes are not shown, and all chromosomes are represented in a similar stage of condensation.(Original-Deyholos-CC:AN)



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