Behavior of transgenic mouse spermatozoa with galline protamine

Male reproductive phenotypes of genetically altered laboratory mice (Mus musculus): a review based on pertinent literature from the last three decades

Laboratory mice (Mus musculus) are preferred animals for biomedical research due to the close relationship with humans in several aspects. Therefore, mice with diverse genetic traits have been generated to mimic human characteristics of interest. Some genetically altered mouse strains, on purpose or by accident, have reproductive phenotypes and/or fertility deviating from wild-type mice. The distinct reproductive phenotypes of genetically altered male mice mentioned in this paper are grouped based on reproductive organs, beginning with the brain (i.e., the hypothalamus and anterior pituitary) that regulates sexual maturity and development, the testis where male gametes and sex steroid hormones are produced, the epididymis, the accessory sex glands, and the penis which involve in sperm maturation, storage, and ejaculation. Also, distinct characteristics of mature sperm from genetically altered mice are described here. This repository will hopefully be a valuable resource for both humans, in terms of future biomedical research, and mice, in the aspect of the establishment of optimal sperm preservation protocols for individual mouse strains.

Interspecific ICSI for the Assessment of Sperm DNA Damage: Technology Report

Xenogenic mammalian sperm heads injected into mouse ovulated oocytes decondense and form pronuclei in which sperm DNA parameters can be evaluated. We suggest that this approach can be used for the assessment of sperm DNA damage level and the evaluation of how certain sperm treatments (freezing, lyophilization, etc.) influence the quality of spermatozoa.

Growth and reproductive traits of F1-generation transgenic goats for human granulocyte-colony stimulating factor

To ensure that animal welfare requirements and phenotypic characteristics of the newly produced transgenic lines are not compromised, an evaluation of all individuals is necessary. This can be inferred by the analysis of the growth and reproduction parameters. The present study was designed to determine the impact of the insertion of human granulocyte-colony stimulating factor (hG-CSF) transgene on growth and reproductive characteristics in first-generation (F1) goats from two transgenic lines. Bodyweight (BW) development (BW at birth, mean BW gain before weaning, BW at weaning, mean BW gain after weaning, BW at puberty), as well as reproductive parameters (age at puberty, ejaculate volume, concentration, total sperm per ejaculate, massal motility, progressive individual motility, major and minor defects) were similar (P > 0.05) between transgenic (T) and non-transgenic (NT) goats. Significant (P < 0.05) differences in mean (±s.d.) white blood cell count were observed between T and NT in first day of life (174.6 ± 14.7 × 103 and 15.0 ± 4.0 × 103 cells/µL), and during (66.8 ± 21.1 × 103 and 17.0 ± 4.6 × 103 cells/µL) and after (36.6 ± 4.0 × 103 and 15.5 ± 2.2 × 103 cells/µL) suckling, even though hG-CSF has not been detected in blood serum in any analysis. Although other cell counts were occasionally higher in T animals, differential counts showed that this difference was mainly due to an increased number of neutrophils, which represents 84.6%, 67.2% and 56.8% of total white blood cell count respectively, in the three time periods. Kidney and liver biochemical analyses indicated that all goats were healthy. Thus, it is possible to assume that all animals are normal and had no deleterious effects on either growth or reproductive parameters by the presence of transgene or as a consequence of leukocyte profile alteration.

Growth performance, reproductive traits and offspring survivability of genetically modified rams overexpressing toll-like receptor 4

Genetic modification provides a means to enhancing disease resistance in animals. Toll-like receptor 4 (TLR4), a member of the TLR family, is critical for the recognition of lipopolysaccharide (LPS)/endotoxin from Gram-negative bacteria by host immune cells, which initiates cell activation and subsequently triggers a proinflammatory response to the invading pathogens. In this study, the first generation of genetically modified (GM) sheep overexpressing TLR4 was produced by microinjection for better disease resistance. Compared with wild-type (WT) rams, the GM rams have similar growth performance, basic semen quality and spermatozoon ultrastructure. The offspring birth rates after cervical artificial insemination were also similar between GM (90.32%) and WT (92.38%) rams. Overall, the presence and expression of the TLR4 transgene in the genome did not appear to interfere with normal semen production, reproductive traits and the ability of transgene transmission to offspring. The expression levels of TLR4, tumor necrosis factor and interferon gamma genes in monocyte/macrophages from GM sheep were significantly higher than that from WT sheep at early stages after LPS stimulation. The GM offspring born from the founder transgenic ram inseminated ewes had similar survival rate with WT offspring (88.89% vs 84.86%) at weaning. The TLR4 transgene showed no deleterious effects on growth performance, reproductive traits and offspring survivability of GM rams. Therefore, the GM sheep overexpressing TLR4 provide a powerful experimental model for analyzing function of TLR4 in vivo during infection and inflammation.

Effect of semen quality in transgenic boars on the developmental competence of preimplantation embryos

The aim of this study was to compare the fertilising capacity of sperm from 6 transgenic (TG) and 6 non-transgenic (NTG) boars based on analyses of embryos resulting from insemination with sperm from these particular boars. Expanded blastocysts were collected from five groups of synchronised gilts (six gilts per group) inseminated by TG boars bearing a gene construct containing the human alpha1,2-fucosyltransferase gene and by NTG boars. The ejaculates used for insemination were analysed to detect apoptotic changes using two fluorescence methods: an assay to assess early changes in the membrane integrity of the sperm using the YO-PRO-1 fluorophore and an assay for phosphatidylserine (PS) translocation across the plasma membranes using fluorescein-labelled Annexin-V. Our results, using a combination of YO-PRO-1 and PI fluorophores, revealed no significant differences in the percentage of sperm subpopulations between non-transgenic and transgenic boars (P<0.01). Moreover, the second fluorescent probe also revealed no significant differences between the average values of live (Ann-V(-)/PI(-)), early apoptotic (Ann-V(+)/PI(-)), and late apoptotic/early necrotic sperm (Ann-V(+)/PI(+)) as calculated for TG and NTG boars. Only the percentage of necrotic sperm (Ann-V(-)/PI(+)) was significantly different (P<0.05) between transgenic and non-transgenic boars (3.4%+/-2.7; 7.2%+/-2.1, respectively). The quality of the preimplantation embryos at the blastocyst stage was determined by counting the number of cells, observing a TUNEL-positive reaction and by caspase-3 labelling. We found that expanded blastocysts that were derived from gilts inseminated with TG and NTG boar semen showed almost no DNA fragmentation (80%) and 70% caspase-3 activity. The expanded blastocysts that were derived from gilts inseminated with TG and NTG boar semen did not differ significantly in their DNA fragmentation, and there were no differences in caspase-3 activity. These results revealed a positive correlation between the percentage of blastocysts with TUNEL-positive nuclei and the percentage of blastocysts with caspase-3 activity (r=0.9787; P<0.0001).

Assessment of plasma membrane and chromatin structure of sperm from transgenic and non-transgenic boars

The aim of this study was to determine the apoptotic changes and chromatin damage in non-transgenic and transgenic boars carrying the human alpha1,2-fucosyltransferase gene. Five ejaculates were collected from six transgenic (TG) and six non-transgenic (NTG) boars. Five ejaculates were collected from six transgenic (TG) and six non-transgenic (NTG) boars both crossbreds of Polish Landrace and Large White. Two fluorescence methods were employed to measure apoptosis: an assay to assess the early changes in sperm membrane integrity using fluorophore YO-PRO-1 and an assay for phosphatidylserine (PS) translocation across the plasma membrane using fluorescein-labeled Annexin-V. The chromatin damage was assessed based on the sperm chromatin structure assay method. No significant differences in the proportion of all detected subpopulations of spermatozoa were found between TG and NTG boars. Similarly, the analysis of the chromatin structure revealed no statistical differences in the sperm chromatin damage between TG and NTG boars. In conclusion, the presence of the human alpha1,2-fucosyltransferase gene in the genome of TG boars did not cause any spermatogenesis process disturbances leading to the increased production of apoptotic spermatozoa. Moreover, the low level of sperm with damaged chromatin in TG boars confirms the high stability of the spermatogenesis process in the TG boars analyzed.

Role of mammalian sperm nuclear structure in fertilization and embryo development

Although intact spermatozoon is successfully collected from infertile patients, repeated implantation failure or pregnancy loss are often experienced. Sperm nuclear defects have been thought to be one of the most important reasons for repeated assisted reproductive technology failure. In comparison with other mammalians, characteristic heterogeneity has been found in each mature human sperm nuclei, therefore it is necessary to investigate the significance between fertilization failure, developmental disability and structural abnormality of human sperm nuclei. Furthermore, if close relationships between the heterogeneity of human ejaculated sperm nuclei and DNA fragmentation are defined by analyzing sperm nucleoproteins, it would be clearly shown that impaired sperm chromatin leads to failure of embryo development in vitro or in vivo, so called late paternal effect on embryo development. It will be necessary in the near future to study the strategy for more novel methodology than those previously reported in terms of sperm selection. The present report reviews the roles of mammalian sperm nuclear structure, especially in humans, in fertilization and embryo development after the insemination procedure. (Reprod Med Biol 2006; 5: 161-168).

Protamines and male infertility

Protamines are the major nuclear sperm proteins. The human sperm nucleus contains two types of protamine: protamine 1 (P1) encoded by a single-copy gene and the family of protamine 2 (P2) proteins (P2, P3 and P4), all also encoded by a single gene that is transcribed and translated into a precursor protein. The protamines were discovered more than a century ago, but their function is not yet fully understood. In fact, different hypotheses have been proposed: condensation of the sperm nucleus into a compact hydrodynamic shape, protection of the genetic message delivered by the spermatozoa, involvement in the processes maintaining the integrity and repair of DNA during or after the nucleohistone-nucleoprotamine transition and involvement in the epigenetic imprinting of the spermatozoa. Protamines are also one of the most variable proteins found in nature, with data supporting a positive Darwinian selection. Changes in the expression of P1 and P2 protamines have been found to be associated with infertility in man. Mutations in the protamine genes have also been found in some infertile patients. Transgenic mice defective in the expression of protamines also present several structural defects in the sperm nucleus and have variable degrees of infertility. There is also evidence that altered levels of protamines may result in an increased susceptibility to injury in the spermatozoan DNA causing infertility or poor outcomes in assisted reproduction. The present work reviews the articles published to date on the relationship between protamines and infertility.

Transgene transmission to progeny by oMt1a-oGH transgenic mice

Most studies utilizing transgenic technology focus on the impact to traits of interest, rather than propagation of the transgene to offspring. In animals containing growth hormone constructs, transgene transmission to progeny follows a Mendelian pattern of inheritance in the first few generations following generation of a founder animal, but decreases in subsequent generations. In the present study, the ovine metallothionein 1a-ovine growth hormone (oMt1a-oGH) transgenic mouse was used to determine whether transgene transmission rate to progeny was affected by overexpression of ovine growth hormone in the transgenic parent. The oMt1a-oGH mouse is a useful model for assessing transgene transmission, as the construct is easily regulatable and transgene inactivation results in a return of plasma GH to basal levels. Male and female hemizygous oMt1a-oGH mice were assigned to 1 of 3 treatment groups: (1) mice never actively expressing the transgene, (2) mice actively expressing the transgene from 3 weeks of age, and (3) mice actively expressing the transgene from 3 to 11 (males) or 3 to 8 (females) weeks of age. Transgenic mice were mated to wild type animals and the resulting progeny were genotyped. Males never actively expressing the transgene passed on the transgene to progeny in a Mendelian fashion, while males actively expressing the transgene transmitted the transgene to a smaller than expected number of progeny. However, following inactivation of the oMt1a-oGH construct in transgenic males, subsequent offspring demonstrated Mendelian inheritance of the transgene. In contrast, females expressing the transgene from 3 to 8 weeks of age were able to pass on the oMt1a-oGH construct in a Mendelian fashion, but females from other treatment groups were not. In oMt1a-oGH males, reduced transgene transmission appears to be due to selection against transgenic gametes. In females, however, selection against the transgenic genotype likely occurs at the embryonic level.

A walk though vertebrate and invertebrate protamines

An updated comparative analysis of protamines and their corresponding genes is presented, including representative organisms from each of the vertebrate classes and one invertebrate (squid, Loligo opalescens). Special emphasis is placed on the implications for sperm chromatin organization and the evolutionary significance. The review is based on some of the most recent publications in the field and builds upon previously published reviews on this topic.

Chromosomal proteins in the spermatogenesis of Drosophila

Chromatin constitution in the male germ line of Drosophila is discussed with respect to the substitution of somatic histones by protamines or other basic proteins. The specific properties of germ line chromatin include the initiation and completion of the spermatogenic pathway and the reprogramming of the genome for embryonic development. During meiotic prophase cell cycle-regulated H3 histones appear to a large extent to be substituted by the histone H3.3 replacement variant protein, which is generally found associated with transcriptionally active chromatin. Condensation of the chromosomes during meiosis and the subsequent compaction for packaging in the sperm head require suitable proteins, but the cell cycle-regulated histones are not available as their expression is limited to S-phase. It is, therefore, proposed that any basic protein with a limited range of sequence requirements may take over this packaging function. Suitable proteins may have evolved by divergence from histone variants not restricted in their expression to S-phase, similar to the testes-predominant histone H3.3A of Drosophila.

Sperm chromatin integrity of bucks transgenic for the WAP bGH gene

The aim of the study was to compare sperm chromatin structure of transgenic and non-transgenic rabbits. In addition, the effect of chromatin structure on semen fertility was determined. Twenty male rabbits transgenic (TG) for WAP bGH gene (Edison Biotechnology Institute Ohio University, USA) and nine non-transgenic (NTG) males were used. Both TG and NTG rabbits were 13-18 months old. Semen was collected at 1-week intervals and 3-7 ejaculates from each rabbit were examined in total. Sperm chromatin abnormalities were measured flow cytometrically according to the Sperm Chromatin Structure Assay method: after chromatin denaturation by low pH, sperm cells were stained with metachromatic fluorochrome acridine orange. Spermatozoa with abnormal chromatin structure and, subsequently, higher degree of denaturation, showed a shift in red fluorescence. Two different methods of semen fertility estimation were used: (1) for TG rabbits, AI of superovulated does and calculation of percentages of fertilised eggs and embryos developing in vitro to the blastocyst stage; (2) for NTG rabbits, AI of non-stimulated does and calculation of percentages of pregnant does and mean litter sizes. The mean value of COMPalpha(t) was 3.71 for TG rabbits and 2.89 for NTG rabbits (no significant difference, t-test). The mean values of S.D.alpha(t) for the TG and NTG rabbits were 10.94 and 10.40 (no significant difference, t-test), respectively. There were no significant correlations between sperm chromatin structure of TG males and the percentages of fertilised eggs or embryos developing to the blastocyst stage. A statistically significant correlation (-0.68, P<0.05) was found between S.D.alpha(t) of NTG males and percentages of pregnant does. The results showed chromatin stability was not different for sperm obtained from TG versus NTG bucks. The presence of WAP bGH gene construct in the genome of transgenic rabbits did not cause any spermatogenesis process disturbances leading to the production of spermatozoa with damaged chromatin structure. This suggests that the mere presence of the introduced gene construct does not lead to any abnormalities in DNA and chromatin proteins interaction. The possible chromatin damages in transgenic animals should be attributed to the activity of the introduced gene. The relationships between chromatin structure and fertility are only significant for sperm from NTG bucks.

The correlation of sperm chromatin decondensation following in vitro exposure to heparin and sperm penetration rates

PURPOSE

The aim of this study was to evaluate the possible correlation of low-dose heparin-induced decondensation of sperm chromatin with sperm concentration, motility, morphology, membrane hypoosmotic response, ejaculate volume, and the ability of sperm to penetrate zona-free hamster oocytes.

METHODS

Twenty-two donors of known fertility and 105 patients undergoing evaluation at an andrology laboratory were evaluated by standard World Health Organization semen analysis techniques and a modified sperm penetration assay (SPA). An aliquot was also incubated for 60 min and Ham's F10 medium containing 50 USP/ml heparin. The percentage of sperm undergoing chromatin decondensation was evaluated and correlated to SPA rates and semen quality parameters.

RESULTS

No significant correlation was observed between semen parameters and decondensation rates. A nonsignificant (P = 0.11) inverse correlation (P = -0.21) was observed between SPA rates and chromatin decondensation. Significant (P < 0.001) differences were observed in the decondensation rate of donors (3.7 +/- 0.6), patients with normal SPA rates (7.8 +/- 1.5), and patients with decreased SPA rates (21.7 +/- 1.8). The decondensation rates were significantly different (P < 0.01) between patients with a normal SPA rate and patients with a decreased SPA rate.

CONCLUSIONS

These data indicate a significant inverse relationship between the SPA rate, which has previously been shown to correlate highly with fertilization ability and heparin-induced sperm chromatin decondensation.