Sperm parameters in Israeli transgender women before and after cryopreservation

BACKGROUND

The application of fertility preservation, initially intended for oncological patients prior to gonadotoxic treatment, has extended in recent years to transgender and gender-non-conforming individuals undergoing therapy for gender compatibility.

OBJECTIVES

To examine semen quality and survival in transgender women pursuing semen cryopreservation in the presence or absence of gender-affirming hormonal medication.

MATERIALS AND METHODS

In this retrospective cohort study, we reviewed data of 74 consecutive transgender women presenting for semen cryopreservation at a single center between 2000 and 2019. Semen parameters before and after cryopreservation were compared to a control group composed of 100 consecutive sperm bank donor candidates. A subgroup analysis of subjects who had used gender-affirming hormonal treatment was also performed.

RESULTS

Compared to the control group, transgender women had lower total sperm count (144.0 vs. 54.5 million, respectively, p < 0.001), lower sperm motility percentage (65.0% vs. 51.0%, respectively, p < 0.001), and lower total motile sperm count (94.0 vs. 27.0 million, respectively, p < 0.001). Values were further decreased in transgender women who had received hormonal treatment before sperm cryopreservation. Post-thawing motility rate remained lower in the transgender group compared to the control group (20.0% vs. 45.0%, respectively, p < 0.001), and the total motile count remained lower as well (2.7 vs. 9.0 million, respectively, p < 0.001). Following sperm cryopreservation, the post-thaw decreases in total motile sperm count were higher in the transgender group compared with the control group (91.5% vs. 90.0%). Further subdivision in the transgender group showed that the decrease in total motile sperm count was lower for transgender women who did not use gender-affirming hormonal treatment compared to those who did (-89.7% vs. -92.6%, respectively, p < 0.01).

DISCUSSION AND CONCLUSION

Sperm parameters in transgender women are poor compared to candidates for sperm donation representing the general population. Specimens collected after discontinuation of gender-affirming hormone treatments were further impaired. Moreover, post-thawing sperm total motile count, motility, and overall sperm survival were reduced in transgender women.

A pathogenic variant in the uncharacterized RNF212B gene results in severe aneuploidy male infertility and repeated IVF failure

Quantitative and qualitative spermatogenic impairments are major causes of men's infertility. Although in vitro fertilization (IVF) is effective, some couples persistently fail to conceive. To identify causal variants in patients with severe male infertility factor and repeated IVF failures, we sequenced the exome of two consanguineous family members who underwent several failed IVF cycles and were diagnosed with low sperm count and motility. We identified a rare homozygous nonsense mutation in a previously uncharacterized gene, RNF212B, as the causative variant. Recurrence was identified in another unrelated, infertile patient who also faced repeated failed IVF treatments. scRNA-seq demonstrated meiosis-specific expression of RNF212B. Sequence analysis located a protein domain known to be associated with aneuploidy, which can explain multiple IVF failures. Accordingly, FISH analysis revealed a high aneuploidy rate in the patients' sperm cells and their IVF embryos. Finally, inactivation of the Drosophila orthologs significantly reduced male fertility. Given that members of the evolutionary conserved RNF212 gene family are involved in meiotic recombination and crossover maturation, our findings indicate a critical role of RNF212B in meiosis, genome stability, and in human fertility. Since recombination is completely absent in Drosophila males, our findings may indicate an additional unrelated role for the RNF212-like paralogs in spermatogenesis.

MicroRNAs expression in semen and testis of azoospermic men

BACKGROUND

MicroRNAs are involved in the regulation of spermatogenesis, are detected in semen and may be useful as molecular markers for predicting residual complete spermatogenesis in azoospermic men.

OBJECTIVES

To study the biomarker potential of microRNAs that are detected in semen and testicular tissue.

MATERIALS AND METHODS

MicroRNA profiles were analyzed in semen fractions of normozoospermic (n = 3) and azoospermic (n = 6) men by small RNA deep sequencing. Specific microRNAs were further analyzed by reverse transcription and quantitative polymerase chain reaction in eight testicular samples and 46 semen supernatants. The semen supernatant samples included 18 normozoospermic and 28 azoospermic men with various pathologies.

RESULTS

The sequenced microRNA profiles of semen supernatant fraction samples were distinct from the other fractions. Significant expression differences were observed between the semen supernatant of normozoospermic and azoospermic men. Further analysis by reverse transcription and quantitative polymerase chain reaction revealed that expression of miR-202-3p was considerably reduced (undetectable in most samples) in the azoospermic semen supernatants. The expression of miR-202-3p was significantly lower in the azoospermic specimens than in the normozoospermic specimens and a trend was observed for miR-629-5p (p = 0.03 and 0.06, respectively). Differences in expression levels in the semen supernatant were observed among the various pathologies but not to a level of significance, possibly because of the small subgroups. miRNA-370-3p was significantly higher in semen supernatant samples from azoospermic men without sperm cells in testis (p = 0.05). In testes, the three microRNAs were expressed at higher levels in the obstructive and spermatocyte maturation arrest pathologies than in mixed atrophy and Sertoli cell only. miR-202-3p was detected in all testicular samples.

CONCLUSIONS

MicroRNA expression profiles in semen were distinguishable between azoospermic and normozoospermic men. The microRNA profile also diverged among azoospermic men subdivided according to their testicular pathologies. The levels of specific microRNAs in testis and in the semen supernatant were not directly correlated.

Determining the expression levels of CSF-1 and OCT4, CREM-1, and protamine in testicular biopsies of adult Klinefelter patients: Their possible correlation with spermatogenesis

Klinefelter syndrome (KS) is the most prevalent genetic disorder of infertile males. This study aimed to determine in Klinefelter patients (KS) the expression levels of spermatogenic markers and testicular growth factors that might predict spermatogenesis based on conventional testicular sperm extraction (TESE). The expression levels of the pre-meiotic (OCT4, CD9, GFR-α1, α-6-INTEGRIN, SALL4, C-KIT), meiotic (CREM-1), and post-meiotic (protamine) markers, as well as the colony stimulating factor-1 (CSF-1) were examined in testicular biopsies with and without mature sperm of KS and normal karyotype of azoospermic patients (AZO) with complete spermatogenesis. In the biopsies of AZO, the expression levels (fold of expression compared to the PPI of the same sample) of OCT4 were 9.68± 7.93, CREM 42.78± 28.22, CSF-1 3.07 ± 3.19, and protamine 78498.12 ± 73214.40. Biopsies from KS included 7 with sperm and 17 without sperm. Among the biopsies with sperm, the expression levels of OCT4 were 7.27± 9.29, CREM 3.13± 7.89, CSF-1 35.5 ± 48.01, and protamine 902.97 ± 2365.92. In 14 biopsies without sperm, we found low expression levels of OCT4, CREM and CSF-1, and no expression of protamine. However, in three of the biopsies without sperm that highly expressed OCT4 and CSF-1, the expression levels of CREM-1 and protamine were high. These results may be used for further consulting with patients considering repeating conventional TESE or micro TESE and cryopreservation for possible future in-vitro spermatogenesis.

The impact of COVID-19 vaccine on sperm quality

Objective

To examine the effect of the BNT162b, mRNA, SARS‐CoV‐2 virus vaccine on sperm quality.

Methods

This was a prospective cohort study conducted on sperm donors at the sperm bank of a tertiary, university affiliated medical center. All sperm donors donated sperm repeatedly and the average sperm parameters of all available samples were compared before and after receiving the SARS‐CoV‐2 vaccine. Each donor served as his own control. For all participants, at‐least one sperm sample was received 72 days after completing the second vaccine. Main outcome measures included total sperm count, total motile count and percent of motile sperm.

Results

A total of 898 sperm samples from 33 sperm donors that were vaccinated with the Pfizer BNT162b, mRNA, SARS‐CoV‐2 virus vaccine were analyzed, 425 samples were received before the vaccine, while 473 samples were received after vaccination. Total sperm count and total motile count increased after the second vaccine compared to samples before vaccination. Percent of motile sperm did not change after vaccine.

Conclusion

The Pfizer BNT162b, SARS‐CoV‐2 vaccine has no deleterious effect on sperm quality. Patients and physicians should be counseled accordingly.

The Pfizer BNT162b, SARS‐CoV‐2 vaccine has no deleterious effect on sperm quality.

Testicular microlithiasis defines a subgroup of azoospermic men with low rates of sperm retrieval

OBJECTIVE

To investigate the prevalence of testicular microlithiasis and its association with sperm retrieval rates and histopathology in men with non-obstructive azoospermia.

METHODS

A total of 120 men underwent scrotal ultrasonography prior to microsurgical testicular sperm extraction. Sperm retrieval rate, testicular histopathology, testicular size, reproductive hormones, karyotyping, Y chromosome microdeletion analyses, and presence of varicoceles and hydroceles were compared between men with and without testicular microlithiasis.

RESULTS

The total sperm retrieval rate was 40%. Ten men with normal spermatogenesis were excluded. The remaining 110 men with non-obstructive azoospermia were analyzed and testicular microlithiasis was detected in 16 of them (14.5%). The sperm retrieval rate in that subgroup was only 6.2% (1/16) as opposed to 39.4% (37/94) in men with non-obstructive azoospermia and no evidence of microlithiasis (P = 0.009). The mean right and left testicular diameters were significantly lower in the microlithiasis group (P = 0.04). On multivariate logistic regression analysis, the presence of mictolithiasis (odds ratio 7.4, 95% confidence interval 2.3, 12.2; P = 0.01) was the only independent predictor of unsuccessful sperm retrieval. The 15 patients with microlithiasis and without successful sperm extraction were diagnosed by histopathology as having Sertoli cells only. The 16th patient with successful sperm retrieval had a histopathology of mixed atrophy and was diagnosed with Klinefelter syndrome.

CONCLUSION

The presence of testicular microlithiasis is associated with low sperm retrieval rates among our cohort of men with non-obstructive azoospermia undergoing scrotal ultrasonography prior to microsurgical testicular sperm extraction. Larger, prospective studies should be conducted to confirm these findings.

P–441 Semen quality and cryopreservation in adolescent transgender females

Study question

What are the semen quality and cryopreservation outcomes among adolescent transgender females at the time of fertility preservation (FP) before initiating gender-affirming hormone (GAH) treatment?

Summary answer

Semen quality is strongly reduced among adolescent transgender females before hormone therapy and their stored sperm samples are suitable for intracytoplasmic sperm injection (ICSI).

What is known already

The age of individuals seeking treatment for gender affirmation has fallen sharply in recent years and many of them are adolescents. Estrogen, the primary treatment for transgender women, is known to impair semen quality and fertility potential. Sperm cryopreservation enables young transgender females to circumvent GAH therapy-related fertility impairment and have genetically related children. There are recent data on semen quality among adult transgender women who preserve fertility before exposure to GAH therapy, but little is known about pubertal transgender female adolescents.

Study design, size, duration

This retrospective cohort study included 26 adolescent transgender females who underwent FP between June 2013 and October 2020.

Participants/materials, setting, methods

Before initiating gonadotropin-releasing hormone agonists solely or with GAH treatment, 25 adolescent transgender females were referred to FP in our Fertility Institute of a tertiary university-affiliated medical center. Pre-freezing semen parameters were compared to WHO 2010 reference values. Post-thaw semen parameters were used to determine adequate assisted reproductive technology (ART). A multivariate linear regression analysis was performed to assess the impact of selected medical and lifestyle factors on the semen quality of our study participants.

Main results and the role of chance

The mean age at which adolescent transgender females underwent sperm cryopreservation was 16.2 ± 1.38 years. The median values of all semen parameters in our study group were significantly lower compared to the WHO data on semen quality in the general population of unscreened men, including volume (1.46 ml vs 3.2 ml, respectively, P = 0.001 ), sperm concertation (28*106/ml vs 64*106/ml, P &lt; 0.001), total sperm number (28.2*106 vs 196*106, P &lt; 0.001), total motility (51.6% vs 62%, P &lt; 0.001), and normal morphology (2% vs 14%, P &lt; 0.001). The frequency of semen abnormalities was teratozoospermia 72%, hypospermia 52%, oligozoospermia 28%, and azoospermia 4%. The median post-thaw total motile count was 0.17*106 per vial, and the quality was adequate only for ICSI in 87.7% of the thawed semen samples. Attention-deficit/hyperactivity disorder (ADHD) diagnosis, history of depression/anxiety, medication for ADHD, and antidepressant drugs were found to correlate with hypospermia. No correlation was found between the time of FP, body mass index, autistic spectrum disorder diagnosis, cannabis use, testis tucking, or the levels of follicle-stimulating hormone, estradiol, and testosterone on the semen parameters.

Limitations, reasons for caution

Because no normal values of semen in adolescents are available and the absence of a matched control group, we used WHO 2010 semen data as reference values, and they may not be representative of the adolescent population.

Wider implications of the findings: Although adolescent transgender females have poor semen quality and limited stored semen samples suitable for advanced ART interventions, even before starting GAH therapy, we highly recommend sperm cryopreservation before initiating GAH treatment and thereby prevent further impairment of sperm quality associated with the hormonal treatment.

Trial registration number

Not applicable

Questioning the utility of round spermatid injections in men with non-obstructive azoospermia

BACKGROUND

Data on who among the infertile male population may benefit from round spermatid injections (ROSI) are lacking.

OBJECTIVE

To determine the probability of finding round spermatids suitable for ROSI in men with non-obstructive azoospermia (NOA) in whom no spermatozoa were retrieved at testicular sperm extraction.

MATERIALS AND METHODS

Four-hundred fifty-seven consecutive men with azoospermia underwent testicular sperm extraction. Clinical examination included age, secondary sexual characteristics, testicular size, reproductive hormone estimation, karyotyping, and Y chromosome microdeletion analyses. Histologic examination was performed, and histologic classification was determined by the most advanced spermatogenetic cell identified in the combined histologic and cytologic examination.

RESULTS

Of the 457 azoospermic men, 342 were diagnosed with NOA, and 148 (148/342, 43%) had mixed atrophy on histopathology and retrievable spermatozoa. No spermatozoa were found in 194/342 men with NOA (57%). Histopathology diagnosed 145/194 (75%) of them with Sertoli cell only, 45/194 (23%) with spermatocyte maturation arrest, and 4/194 (2%) with spermatid maturation arrest.

CONCLUSIONS

Histopathologically identified round spermatids without spermatozoa were rare in men with NOA. Only very few of them are likely to reap the benefits of ROSI, thus presenting the need to reconsider its actual clinical value.

Adolescent Transgender Females Present Impaired Semen Quality That Is Suitable for Intracytoplasmic Sperm Injection Even Before Initiating Gender-Affirming Hormone Treatment

The present study aimed to determine the semen quality and cryopreservation outcomes among adolescent transgender females at the time of fertility preservation (FP) before initiating gender-affirming hormone (GAH) treatment. This retrospective cohort study included 26 adolescent transgender females who underwent FP in our Fertility Institute between 06/2013 and 10/2020. Pre-freezing semen parameters were compared to WHO 2010 reference values. Post-thaw semen parameters were used to determine the adequate assisted reproductive technology (ART). A multivariate linear regression analysis was performed to assess the impact of medical and lifestyle factors on semen quality. The mean age at which adolescent transgender females underwent FP was 16.2 ± 1.38 years. The median values of all semen parameters in our study group were significantly lower compared to the WHO data, including volume (1.46 mL vs 3.2 mL, respectively, P = 0.001 ), sperm concentration (28 × 10⁶/mL vs 64 × 10⁶/mL, P < 0.001), total sperm number (28.2 × 10⁶ vs 196 × 10⁶, P < 0.001), total motility (51.6% vs 62%, P < 0.001), and normal morphology (2% vs 14%, P < 0.001). The frequency of semen abnormalities was teratozoospermia 72%, hypospermia 52%, oligozoospermia 28%, and azoospermia 4%. The median post-thaw total motile count was 0.17 × 10⁶/vial, and the quality was adequate only for ICSI in 87.7% of the thawed semen samples. No correlation was found between selected medical and lifestyle factors and poor semen parameters. Semen quality is strongly reduced among adolescent transgender females before hormone therapy and their stored sperm samples are suitable for intracytoplasmic sperm injection (ICSI) rather than conventional IVF/intrauterine insemination (IUI).

A new MEIOB mutation is a recurrent cause for azoospermia and testicular meiotic arrest

STUDY QUESTION

Are there genetic variants that can be used for the clinical evaluation of azoospermic men?

SUMMARY ANSWER

A novel homozygous frame-shift mutation in the MEIOB gene was identified in three azoospermic patients from two different families.

WHAT IS KNOWN ALREADY

Up to 1% of all men have complete absence of sperm in the semen, a condition known as azoospermia. There are very few tools for determining the etiology of azoospermia and the likelihood of sperm cells in the testis. The MEIOB gene codes for a single-strand DNA binding protein required for DNA double-strand breaks repair during meiosis. MEIOB appears to be exclusively expressed in human and mouse testis, and MeioB knockout mice are azoospermic due to meiotic arrest.

STUDY DESIGN, SIZE, DURATION

Two brothers with non-obstructive azoospermia (NOA) underwent whole-exome sequencing followed by comprehensive bioinformatics analyses. Candidate variations were further screened in infertile and fertile men, as well as in public and local reference databases.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study included 159 infertile and 77 fertile men. The exomes of two Arab men were completely sequenced. In addition, 213 other men of the same Arab ethnicity (136 infertile and 77 fertile men) underwent restriction fragment length polymorphism (RFLP) screening, as did 21 NOA men, of other ethnicities, with testicular impairment of spermatocyte arrest. All of the infertile men underwent Y-chromosome microdeletion and CFTR gene mutation assessments. Comprehensive bioinformatics analyses were designed to uncover candidate mutations associated with azoospermia.

MAIN RESULTS AND THE ROLE OF CHANCE

A novel homozygous frame-shift mutation in the MEIOB gene was identified in two brothers of Arab ethnicity. This frame-shift is predicted to result in a truncated MEIOB protein, which lacks the conserved C-terminal DNA binding domain. RFLP screening of the mutation in 157 infertile men, including 112 NOA patients of Arab ethnicity, identified an additional unrelated NOA patient with the same homozygous mutation and a similar testicular impairment. This mutation was not found in available public databases (n > 160 000), nor in the 77 proven fertile men, nor in our database of local Israeli population variations derived from exome and genome sequencing data (n = 500).

LIMITATIONS, REASONS FOR CAUTION

We have thus far screened for only two specific MEIOB probable pathogenic mutations in a relatively small local cohort. Therefore, the relative incidence of MEIOB mutations in azoospermia should be further assessed in larger and diverse cohorts in order to determine the efficiency of MEIOB sequence screening for clinical evaluations.

WIDER IMPLICATIONS OF THE FINDINGS

The relatively high incidence of likely NOA-causing mutations in MEIOB that was found in our cohort supports the idea that a complete screening of this gene might be beneficial for clinical evaluation of NOA patients.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported in part by a grant to EA from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC grant agreement (616088). There are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Impact of time between repeated sperm freezing cycles on sperm quality

Refreezing of sperm samples would provide the possibility of performing more cycles of fertility treatments. Although the effect of repeated cycles of freezing on sperm quality was studied, the effect of the length of the time interval between each freeze-thaw cycle has not been reported. Hence, we assessed the effect of incubation time on the sperm quality of thawed sperm after repeated freezing. One-hundred samples of potential sperm donations with normal sperm quality were evaluated. The fresh semen samples were analyzed and cryopreserved in liquid nitrogen until use. After thawing, the samples were divided randomly to two groups and reanalyzed for motility, vitality, and DNA fragmentation. They were incubated at room temperature and reanalyzed after either 90 min (group A) or 180 min (group B) of incubation, and once again after a repeated cycle of freezing and thawing. Our results showed that the sperm parameters of fresh samples of both groups were similar. After one freeze-thaw cycle, both groups still had comparable values. At the end of their respective incubation time periods, however, there was a significant difference in the mean values of the assessed parameters between the two groups (p < 0.01). An additional freeze-thaw cycle further exacerbated those differences, with group B undergoing an even more substantial decline (p < 0.001). Our data suggest that thawed human spermatozoa sustain a significant decline in sperm parameters in association with longer incubation time, which is further exacerbated by an additional freeze-thaw cycle.

Changes of Sperm Parameters Along Time Among Groups of Different Qualities

BACKGROUND

Male infertility is solely responsible for approximately 20% of all infertility in couples. Various factors have been proposed as having a negative effect on sperm quality; however, the reasons for the global decline in sperm parameters during the last few decades are still controversial.

OBJECTIVES

To investigate the fluctuations of semen parameters (sperm concentration, motility, and morphology) in three sperm quality groups and to examine the trends of those parameters in the same men over time.

RESULTS

Our data showed deterioration in all semen parameters assessed in the group of men originally considered as having normal semen values according to the 2010 criteria of the World Health Organization. In contrast, we found significant improvement over time in all semen parameters in the group of men with severe oligo-terato-asthenozoospermia.

CONCLUSIONS

Our results suggest that, although there were changes in sperm quality over time in the groups assessed, the clinical significance is negligible and does not necessarily justify a change in the therapeutic approach to infertility or sperm cryopreservation.

Improving preimplantation genetic diagnosis (PGD) reliability by selection of sperm donor with the most informative haplotype

BACKGROUND

The study is aimed to describe a novel strategy that increases the accuracy and reliability of PGD in patients using sperm donation by pre-selecting the donor whose haplotype does not overlap the carrier's one.

METHODS

A panel of 4-9 informative polymorphic markers, flanking the mutation in carriers of autosomal dominant/X-linked disorders, was tested in DNA of sperm donors before PGD. Whenever the lengths of donors' repeats overlapped those of the women, additional donors' DNA samples were analyzed. The donor that demonstrated the minimal overlapping with the patient was selected for IVF.

RESULTS

In 8 out of 17 carriers the markers of the initially chosen donors overlapped the patients' alleles and 2-8 additional sperm donors for each patient were haplotyped. The selection of additional sperm donors increased the number of informative markers and reduced misdiagnosis risk from 6.00% ± 7.48 to 0.48% ±0.68. The PGD results were confirmed and no misdiagnosis was detected.

CONCLUSIONS

Our study demonstrates that pre-selecting a sperm donor whose haplotype has minimal overlapping with the female's haplotype, is critical for reducing the misdiagnosis risk and ensuring a reliable PGD. This strategy may contribute to prevent the transmission of affected IVF-PGD embryos using a simple and economical procedure.

TRIAL REGISTRATION

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. DNA testing of donors was approved by the institutional Helsinki committee (registration number 319-08TLV, 2008). The present study was approved by the institutional Helsinki committee (registration number 0385-13TLV, 2013).

BRDT gene sequence in human testicular pathologies and the implication of its single nucleotide polymorphism (rs3088232) on fertility

Bromodomain testis-specific (BRDT) protein is essential for the normal process of spermatogenesis. Mutant mice that expressed truncated BRDT had impaired testicular histology with severely reduced sperm concentration and abnormal sperm morphology, while a model of knockout Brdt mice with no BRDT protein had complete meiotic arrest. A BRDT single nucleotide polymorphism (SNP) (rs3088232) was reported as being associated with infertility in men. We assessed testicular specimens of 276 azoospermic men who underwent testicular sperm extraction to search for specimens that showed spermatogenic impairments similar to those of mutant BRDT mice. Ten similar specimens were selected for BRDT gene sequencing and they revealed three NCBI-reported SNPs (rs10783071, rs3088232 and rs10747493) variously distributed among them. Bioinformatics analysis predicted that they would not affect protein activity. Further assessment of rs3088232 frequency in a large group of non-obstructive azoospermia men and fertile controls demonstrated no significant difference between them (27.2 and 21.7% respectively; p = 0.122, Fisher's exact test). We conclude that the testicular impairments observed in the 10 specimens were not a consequence of BRDT gene mutation. The association between BRDT rs3088232 and infertility that had been reported in other studies was not supported.

Involvement of the prostate and testis expression (PATE)-like proteins in sperm-oocyte interaction

BACKGROUND

The prostate and testis expression (PATE)-like family of proteins are expressed mainly in the male genital tract. They are localized in the sperm head and are homologous to SP-10, the acrosomal vesicle protein also named ACRV1. Our aim was to characterize the expression and functional role of three PATE-like proteins in the testis and ejaculated sperm.

METHODS

The expression and localization of PATE-like proteins in human testis biopsies (n= 95) and sperm cells were assessed by RT-PCR, immunohistochemistry and immunofluorescence staining (at least 600 sperm cells per specimen). The function of the PATE protein was tested by the hemizona assay and hamster egg penetration test (HEPT).

RESULTS

PATE and PATE-M genes and proteins were present almost exclusively in germ cells in the testis: immunoflourescence showed that the percentage of germ cells positive for PATE, PATE-M and PATE-B was 85, 50 and 2%, respectively. PATE and PATE-M proteins were localized in the equatorial segment of the sperm head, while PATE-B protein was localized in the post-acrosomal region. A polyclonal antibody (Ab, at 1:50 and 1:200 dilutions) against the PATE protein did not inhibit sperm-zona binding in the hemizona assay (hemizona index of 89.6 ± 10 and 87 ± 36%, respectively). However, there was inhibition of sperm-oolemma fusion and penetration in the HEPT (penetration index: without Ab 7 ± 3.9; Ab dilution of 1:100, 4 ± 3.5; Ab dilution of 1:20, 0.6 ± 1.2, P < 0.001).

CONCLUSIONS

Our data suggest that PATE protein is involved in sperm-oolemma fusion and penetration but not sperm-zona binding.