Impairment of gastric acid secretion and increase of embryonic lethality in Foxq1-deficient mice.

The mouse Foxq1 gene, also known as Hfh1, encodes a winged helix/forkhead transcription factor. In adult mice, Foxq1 is highly expressed in kidney and stomach. Here, we report that Foxq1 is expressed during prenatal and postnatal stomach development and the transcripts are restricted to acid secreting parietal cells. Mice homozygous for a deletion of the Foxq1 locus on a 129/Sv x C57BL/6J hybrid genetic background display variable phenotypes consistent with requirement of the gene during embryogenesis. Approximately 50% of Foxq1-/- embryos die in utero. Surviving homozygous mutants are normal and fertile, and have a silky shiny coat. Although the parietal cell development is not affected in the absence of Foxq1, there is a lack of gastric acid secretion in response to various secretagogue stimuli. Ultrastructural analysis suggests that the gastric acid secretion defect in Foxq1-deficient mice might be due to impairment in the fusion of cytoplasmic tubulovesicles to the apical membrane of secretory canaliculi.

Asthenoteratozoospermia in mice lacking testis expressed gene 18 (Tex18).

Testis expressed gene 18 (Tex18) is a small gene with one exon of 240 bp, which is specifically expressed in male germ cells. The gene encodes for a protein of 80 amino acids with unknown domain. To investigate the function of (Tex18) gene, we generated mice with targeted disruption of the (Tex18) gene by homologous recombination. Homozygous mutant males on a mixed genetic background (C57BL/6J x 129/Sv) are fertile, while they are subfertile on the 129/Sv background, although mating is normal. We showed that Tex18(-/-) males are subfertile because of abnormal sperm morphology and reduced motility, which is called asthenoteratozoospermia, suggesting that (Tex18) affects sperm characteristics. Maturation of spermatids is unsynchronized and partially impaired in seminiferous tubules of Tex18(-/-) mice. Electron microscopical examination demonstrated abnormal structures of sperm head. In vivo experiments with sperm of Tex18(-/-) 129/Sv mice revealed that the migration of spermatozoa from the uterus into the oviduct is reduced. This result is supported by the observation that sperm motility, as determined by the computer-assisted semen analysis system, is significantly affected, compared to wild-type spermatozoa. Generation of transgenic mice containing Tex18-EGFP fusion construct revealed a high transcriptional activity of (Tex18) during spermiogenesis, a process with morphological changes of haploid germ cells and development to mature spermatozoa. These results indicate that (Tex18) is expressed predominantly during spermatid differentiation and subfertility of the male Tex18(-/-) mice on the 129/Sv background is due to the differentiation arrest, abnormal sperm morphology and reduced sperm motility.

The scoliosis (sco) mouse: a new allele of Pax1.

We describe the spontaneous mutant mouse scoliosis (sco) that carries a new allele of Pax1 (un-i, undulated intermediate). The Pax1(un-i) allele is lacking the 5'-flanking region and exon 1 to 4 which is mapped to nt -2636 to -640 and -272 to 4271 of the Pax1 gene. Homozygous mice show a mild form of the known phenotypes of other Pax1 mutants. Adult mice have a lumbar scoliosis and kinky tails. In homozygous embryos the skeleton ossifies early, ossification centers of the vertebral bodies are fused with the ossification centers of the pedicles. Neural arches and spinous processes are underdeveloped but the pedicles and transverse processes are overdeveloped which is in contrast to other Pax1 mutants. In the scapula, the acromion is missing and the deltoid tuberosity of the proximal humerus is shortened and thickened. Among the inner organs the thymus development is affected. In late embryos, the thymus is small and thymocyte numbers are reduced. T-cell development from CD4- and CD8- double negative (DN) to CD4+ and CD8+ double positive (DP) is decelerated. The percentage of CD90+ cells is also reduced but in contrast to other Pax1 mutants no alteration of the expression level of the CD90 (Thy-1) could be found.

[Genetic causes of male infertility]. / Genetische Ursachen der männlichen Infertilität.

7% of all human males suffer from infertility. In at least 10% of these males infertility is due to genetic causes. Because modern reproduction techniques like ICSI (intracytoplasmic sperm injection) can help the couples to overcome infertility, it is mandatory to analyze underlying genetic causes of male infertility. If infertility in a male is due to a genetic defect, the risk of the respective couple for abortuses or malformed children is increased. The main and relevant causes for male infertility known to day are: numerical and structural chromosomal aberrations, meiotic defects, microdeletions in the region q11.21-23 of the Y-chromosome, mutations in the gene for cystic fibrosis and genetically determined syndromes in which infertility is a symptom. The present knowledge concerning these genetic causes of male infertility is pointed out.

Characterization, expression pattern and chromosomal localization of the spermatogenesis associated 6 gene (Spata6).

We report the cloning and characterization of the spermatogenesis associated 6 gene (Spata6) encoding a predicted protein of 488 amino acids. It exhibits similarity with the motor domain of kinesin related proteins and with the Caenorhabditis elegans neural calcium sensor protein (NCS-2). The gene encodes three mRNAs of approximately 2.6, approximately 1.8 and approximately 1.2 kb. The expression of the 2.6 kb mRNA is detected at low levels in testis, ovary, thymus and placenta, while the 1.8 and 1.2 kb transcripts are exclusively expressed in testis. The 1.8 and 1.2 kb transcripts are specifically expressed in haploid germ cells. Data from in situ hybridization experiments suggested that mRNA expression of Spata6 in spermatids is higher than in spermatocytes and spermatogonia. RT-PCR analysis and whole mount in situ hybridization demonstrate that the Spata6 transcript is expressed during embryonic development and is localized in neural tube, somites and limb buds of mouse embryo. The Spata6 gene consists of 15 exons ranging in size between 40 and 596 bp. The 2.6 and 1.8 kb transcripts have different 5' untranslated sequences but have the same translational initiation site and therefore may encode the same protein with a predicted molecular weight of 49.7 kDa. The 1.2 kb transcript is derived from a proximal promoter between exons 7 and 8, and contains a translation initiation codon AUG, which is in frame with initiator AUG codon of the 2.6 and 1.8 kb transcripts. Therefore, the 1.2 kb transcript may code for a truncated protein of 32 kDa. Western blot analysis with the antiserum raised against a synthetic peptide from the C-terminal of the deduced Spata6 protein detects only a single protein of 53 kDa in all tissues studied. The Spata6 gene was localized to chromosome 5, region q34-35 in the rat and to chromosome 1, region p32-35 in the human. In an effort to determine the function of Spata6, we inactivated the mouse gene in embryonic stem cells through homologous recombination. Although the heterozygous mutant cells were able to generate low coat colour chimeric mice, all chimeras did not transmit the targeted allele to their progeny suggesting that a high contribution of Spata6(+/-) cells lead to the lethality of the chimeric embryos.

Synergistic effects of germ cell expressed genes on male fertility in mice.

Over 200 genes have been shown to be associated with infertility in mouse models. However, knockout mice reveal unexpected functional redundancy of some germ cell expressed genes. Single null mutations in mouse genes encoding four male germ cell proteins, transition protein 2 (Tnp2), proacrosin (Acr), histone H1.1 (H1.1), histone H1t (H1t) and sperm mitochondria-associated cysteine-rich protein (Smcp) have been generated and analysed. Tnp2 is believed to participate in the removal of the nuclear histones and initial condensation of the spermatid nucleus. Proacrosin is an acrosomal protease synthesized as a proenzyme and activated into acrosin during the acrosome reaction. The linker histone subtype H1.1 belongs to the group of main-type histones and is synthesized in somatic tissues as well as in germ cells during the S-phase of the cell cycle. The histone gene Hist1h1t is expressed exclusively in spermatocytes and may have a function in establishing an open chromatin structure for the replacement of histones by transition proteins and protamines. Sperm mitochondria-associated cysteine-rich protein (Smcp) is a major structural element of the mitochondria in the midpiece of the sperm tail. Male mutant mice lacking any of these proteins show no apparent defects in spermatogenesis or fertility. To examine the synergistic effects of these proteins in spermatogenesis and during fertilization four lines of double knockout mice Hist1h1a/Mcsp, Hist1h1t/Mcsp, Tnp2/Mcsp and Acr/Mcsp were established. It was found that even when knockout mice are heterozygous for one allele (-/+) and homozygous for the other allele (-/-), mice were subfertile. Homozygous double knockout mice of all four lines are nearly infertile. However, in the four homozygous double knockout mouse lines, different characteristic abnormalities are prominently manifested: In Hist1h1a-/-/Mcsp-/- the migration of spermatozoa is disturbed in female genital tract, in Hist1h1t-/-/Mcsp-/- spermatozoa show morphological head abnormalities, in Tnp2-/-/Mcsp-/- the motility of sperm is affected, and in Acr-/-/Mcsp-/- the sperm-oocyte interaction is impaired. These findings indicate strongly that male germ cell expressed genes have synergistic effects on male fertility.

Mouse pelota gene (Pelo): cDNA cloning, genomic structure, and chromosomal localization.

The pelota gene of Drosophila melanogaster encodes a protein which is included in cell cycle regulation. Mutations were found to result in spermatogenic arrest, female sterility and disturbances in the patterning of the eye. We have recently isolated and characterized cDNA clones coding for the human pelota gene (PELO). Here we describe the cloning of the murine pelota cDNA and gene (Pelo) that encodes a 385-amino-acid protein. The exon-intron structure of the gene, which contains three exons, was determined. Comparison of the mouse amino acid sequences with the human and Drosophila sequences revealed an overall high identity (96% and 70%, respectively). Northern blot analysis detected a 1.7-kb transcript in all tissues studied. Southern blot analyses revealed that the pelota gene is present as a single copy in the mouse genome. The mouse pelota gene (Pelo) was mapped to the distal end of chromosome 13, in a region that is homologous with a segment of human chromosome 5q11 containing the orthologous human gene. Cloning of the mouse gene is an important step to study the function of the pelota gene in mammals and to create a mouse model for this evolutionarily conserved gene.

Human cyritestin genes (CYRN1 and CYRN2) are non-functional.

The mouse cyritestin gene is a member of the ADAM (a disintegrin and metalloprotease) gene family and codes for a membrane-anchored sperm protein. Recently, it was shown that cyritestin is critical for male fertility in the mouse. Spermatozoa of cyritestin-deficient mice are not able to bind to the zona pellucida of the oocyte and therefore unable to fertilize the egg. However, zona-free oocytes can be fertilized and the resulting embryos show normal development. In contrast to the mouse, where only one gene for cyritestin (Cyrn) is reported, two cyritestin genes (CYRN1 and CYRN2) are known in humans. The human CYRN1 and CYRN2 genes are located on chromosomes 8 and 16, respectively. We report that 27% of fertile men are deficient for the CYRN1 gene but that all have a CYRN2 gene, suggesting that the CYRN2 gene is the orthologous mouse cyritestin gene in humans and might be involved in sperm-egg interactions. However, the characterization of CYRN2 transcripts from testicular RNA of CYRN1-deficient men demonstrated many termination codons in the synthesized cyritestin cDNA. Furthermore, Western-blot analysis with human testicular protein extracts using an anti-cyritestin antibody failed to detect any cyritestin protein. These results demonstrate clearly that both cyritestin genes are non-functional in humans.

Teratozoospermia in mice lacking the transition protein 2 (Tnp2).

It is believed that the transition proteins (Tnp1 and Tnp2) participate in the removal of the nucleohistones and in the initial condensation of the spermatid nucleus. Later in spermatogenesis, Tnp1 and Tnp2 are replaced by the protamines 1 and 2. In an effort to elucidate the physiological role of Tnp2, we have disrupted its locus by homologous recombination. Breeding of the Tnp2(-/-) males on different genetic backgrounds revealed normal fertility on the mixed background C57BL/6Jx129/Sv, but total infertility on the inbred 129/Sv background. Light and electron microscopy showed that the germ cells were capable of undergoing chromatin condensation, although many spermatozoa exhibited head abnormalities with acrosomes not attached to the nuclear envelope. Furthermore, migration of Tnp2(-/-) spermatozoa from the uterus into the oviduct was reduced. These results suggest that male infertility of the Tnp2(-/-) mice is a result of sperm head abnormalities and reduced sperm motility. The increased level of the Tnp1 transcript in testes of the Tnp2-deficient mice raises the possibility that a deficiency created through the disruption of the Tnp2 gene can be compensated for by recruitment of the Tnp1.

Increase in final stages of follicular atresia and premature decay of corpora lutea in Insl3-deficient mice.

The insulin-like factor 3 (Insl3), a member of the insulin-like hormone family, is exclusively synthesized in gonads. Our recent analysis of Insl3-deficient mice revealed the regulating role of the Insl3 factor on the gubernaculum development during the transabdominal descent of the testis. Here we define the role of the Insl3 factor by histometric analysis of wild-type and Insl3(-/-) ovaries. Ovaries from 40-day-old- and 6-month-old Insl3(-/-) mice as well as from wild-type littermates were serially sectioned. Sections were stained with periodic acid Schiff reaction (PAS) for counting the number of zonae pellucidae which indicated the final stages of follicular atresia. Corpora lutea were also determined. Some sections were processed using either a modified TUNEL method for in situ detection of apoptosis or a lectin labelling technique with Griffonia simplicifolia I agglutinin (GS I) for endothelial cell occurrence. The number of zonae pellucidae was higher in Insl3-deficient ovaries of both ages than in ovaries of wild-type sisters (P < 0.05 for 40-day-old ovaries; P < 0.01 for 6-month-old ovaries). Additionally, the wild-type mice of both ages possessed threefold more corpora lutea than their Insl3 littermates (P < 0.01 for 40-day-old; P < 0.001 for 6-month-old). In general, wild-type corpora lutea looked healthy, showed GS I-positive endothelial cells and no apoptotic cells. Corpora lutea from mutants were rich in regressing GS I luteal cells, and apoptotic cells appeared. We conclude: Follicular atresia and luteolysis are accelerated in ovaries of Insl3-deficient mice probably because of increased apoptosis. The Insl3 function thus appears to rescue endocrine cells from the apoptotic pathway.

Hormonal control of gubernaculum development during testis descent: gubernaculum outgrowth in vitro requires both insulin-like factor and androgen.

The gubernaculum connects the gonad to the inguinoscrotal region and is involved in testis descent. It rapidly develops in the male fetus, whereas development in the female fetus is lacking. Possible factors involved in gubernaculum development are androgens, anti-Müllerian hormone (AMH), and insulin-like factor (Insl3). Sexual dimorphism in gubernaculum development correlated with the mitotic activity of cells in the gubernacular bulbs from male and female fetuses. Androgen receptor expression was restricted to the mesenchymal core of the gubernacular bulb, whereas skeletal muscle was detected in its outer layer. In an organ culture system devised to further study gubernaculum development in vitro, morphology of gubernacular explants grown in the presence of testes was comparable with that of gubernacula developed in vivo. Testicular tissue or medium containing R1881, a synthetic androgen, had a growth stimulatory effect on gubernacular explants compared with ovarian tissue or basal medium only. Moreover, Amh-/-, Amh+/-, and Insl3+/- testes stimulated the growth of gubernacular explants to the same extent as control testes. Insl3-/- testes, however, did not produce such an activity. This study reveals an essential role for both androgen and Insl3 in the gubernaculum outgrowth during transabdominal testis descent.

Molecular cloning, expression and chromosome location of the human pelota gene PELO.

The pelota gene of Drosophila melanogaster encodes a protein that was found to be included in cell cycle regulation. Mutations were found to result in spermatogenic arrest, female sterility and disturbances in the patterning of the eye. Here we describe the cloning of the human pelota cDNA (PELO) that encodes a 385-amino-acid protein. Southern blot and fluorescence in situ hybridization analyses revealed that PELO is present as a single copy gene in the human genome and is localized on chromosome 5q11.2. Northern blot analysis revealed the presence of a 1.6-kb transcript in all tissues studied and an additional 2.0-kb transcript in testis.

The role of the testicular factor INSL3 in establishing the gonadal position.

INSL3, also designated Leydig insulin-like (Ley I-L) or relaxin-like factor (RLF), belongs to the insulin-like hormone superfamily. It is expressed in pre- and postnatal Leydig cells of the testis and in postnatal theca cells of the ovary. This sexual dimorphic pattern of INSL3 expression during development led us to suggest that the INSL3 factor could play an essential role in sexual differentiation, gonadal function and germ cell development. Key insights into the role of INSL3 came from analyses of INSL3 knockout mice. These mice showed impaired development of the gubernaculum ligament, a structure that is believed to mediate transabdominal descent of the testis during male embryogenesis. In double mutant XY-mice lacking INSL3 and a functional androgen receptor, it was demonstrated that both are essential for establishment of the sexual dimorphic position of the gonads through regulation of gubernaculum development and regression of the cranial suspensory ligament (CSL) during fetal life. Defects in this developmental process can cause cryptorchidism in the male, which is a most common disorder of sexual differentiation in human.

Involvement of insulin-like factor 3 (Insl3) in diethylstilbestrol-induced cryptorchidism.

Recently, it has been shown that targeted inactivation of the Insl3 gene in male mice results in cryptorchidism. The Insl3 gene encodes insulin-like factor 3 (Insl3), which is expressed in fetal Leydig cells. The testicular factor Insl3 appears to play an important role in the transabdominal phase of testis descent, which involves development of the gubernaculum. Other studies have demonstrated that in utero exposure to diethylstilbestrol (DES), a synthetic estrogen, can lead to cryptorchidism both in humans and in animal models. The present study was undertaken to investigate whether prenatal DES-exposure might interfere with testicular Insl3 mRNA expression. Furthermore, the effect of DES on steroidogenic factor 1 (SF-1) mRNA expression level was determined, since it has been shown that SF-1 plays an essential role in transcriptional activation of the Insl3 gene promoter. Timed pregnant mice were treated with DES (100 microg/kg body weight) or vehicle alone on days E9 (gestational day 9) through E17. Control and DES-exposed mouse fetuses were collected at E16, E17 and E18, when transabdominal testis descent is taking place. Lack of gubernaculum development in DES-exposed animals was confirmed by histological analyses at E17. Expression of Insl3 and SF-1 mRNAs was studied in testes of control and DES-exposed fetuses at E16 and E18 by RNase protection assay. Prenatal DES-exposure resulted in a three-fold decrease in Insl3 mRNA expression level (P<0.005), at both E16 and E18. In contrast, DES treatment had no effect on the expression of SF-1 mRNA. These results support our hypothesis that DES may interfere with gubernaculum development by altering Insl3 mRNA expression, providing a possible mechanism by which DES may cause cryptorchidism.

Male mice deficient for germ-cell cyritestin are infertile.

Cyritestin is a membrane-anchored sperm protein belonging to the ADAM (f1.gif" BORDER="0"> f2.gif" BORDER="0">isintegrin and f1.gif" BORDER="0"> f3.gif" BORDER="0">etalloprotease) family of proteins, which are proposed to be involved in cell-cell adhesion through binding to integrin receptors. Several lines of evidence support a role of cyritestin and other members of this protein family in the fusion of sperm and the egg plasma membrane. In an effort to elucidate the physiological function of cyritestin, we have disrupted its locus by homologous recombination. Male homozygous null mutants are infertile, even though spermatogenesis, mating, and migration of sperm from the uterus into the oviduct are normal. In vitro experiments showed that infertility is due to the inability of the cyritestin-deficient sperm to bind to the zona pellucida. However, after removal of the zona pellucida, sperm-egg membrane fusion monitored by the presence of pronuclei and generation of 2- and 4-cell embryos did not reveal any differences from the wild-type situation. These results demonstrate that cyritestin is crucial in the fertilization process at the level of the sperm-zona pellucida interaction.

Targeted disruption of the Insl3 gene causes bilateral cryptorchidism.

The sexual dimorphic position of the gonads in mammals is dependent on differential development of two ligaments, the cranial suspensory ligament (CSL) and the gubernaculum. During male embryogenesis, outgrowth of the gubernaculum and regression of the CSL result in transabdominal descent of the testes, whereas in the female, development of the CSL in conjunction with failure of the gubernaculum development holds the ovaries in a position lateral to the kidneys. Several lines of evidence suggest that regression of the CSL and induction of gubernaculum development are mediated by testosterone and a yet unidentified testicular factor, respectively. The Insl3 gene (originally designated Ley I-L), a member of the insulin-like superfamily, is specifically expressed in Leydig cells of the fetal and postnatal testis and in theca cells of the postnatal ovary. Here we show that male mice homozygous for a targeted deletion of the Insl3 locus exhibit bilateral cryptorchidism with free moving testes and genital ducts. These malformations are due to failure of gubernaculum development during embryogenesis. In double-mutant male mice for Insl3 and androgen receptor genes, testes are positioned adjacent to the kidneys and steadied in the abdomen by the CSL. These findings demonstrate, that the Insl3 induces gubernaculum development in an androgen-independent way, while androgen-mediated regression of the CSL occurs independently from Insl3.

Transcription of the Leydig insulin-like gene is mediated by steroidogenic factor-1.

The Leydig insulin-like gene (Ley I-L), a member of the insulin-related gene family, is specifically expressed in pre- and postnatal Leydig cells of the testis and in postnatal theca cells of the ovary. To determine the functional region of the mouse Ley I-L promoter and factors controlling the Ley I-L gene expression, we used 2.1 kb of the 5'-flanking region of the mouse Ley I-L gene to generate chimeric constructs with the chloramphenicol acetyltransferase gene (CAT). Transient transfections of MA10 Leydig cells, LTK- fibroblasts, and F9 embryonic cells by a series of 5'-deleted mouse Ley I-L promoter-CAT constructs revealed that the sequence between nucleotides -157 to +4 directs the transcription of the reporter gene in MA10 but not in LTK- and F9 cells, indicating that the determinants of Leydig cell-specific expression reside within this region. Deoxyribonuclease I (DNase I) footprint analysis revealed that the sequences designated SF-1/1, SF-1/2, and SF-1/3 within three DNase I-protected regions are homologous to the consensus binding site of the steroidogenic factor-1 (SF-1). Competition and antibody studies showed that the three SF-1-binding sites in the Ley I-L promoter have similar binding affinities for SF-1. Furthermore, transient transfections of MA10 cells with mutant reporter constructs, in which SF-1/1 or both SF-1/2 and SF-1/3 were deleted, demonstrated that all three SF-1-binding sites are required for SF-1-mediated stimulation of Ley I-L transcription. Cotransfection of an SF-1-containing expression vector together with a Ley I-L promoter-CAT construct into HeLa cells, which lack the endogenous SF-1 protein, resulted in CAT gene transcription, which indicated that SF-1 can transactivate the Ley I-L promoter. These data demonstrate an essential role of SF-1 in transcriptional activation of the Ley I-L promoter.

Molecular cloning, chromosomal localization, and expression analysis of CYRN1 and CYRN2, two human genes coding for cyritestin, a sperm protein involved in gamete interaction.

Germ cell cyritestin is a membrane-anchored protein belonging to the ADAM family of proteins. Sequencing of eight human cyritestin cDNA clones revealed that they are identical at their 5' and 3' ends but differ from each other in the length of an internal deletion, suggesting that the human cyritestin mRNA is alternatively spliced. Internal deletions that are present in some cDNA isoforms do not cause a frameshift in the C-terminal coding region. Analysis of the predicted amino acid sequences demonstrated that the human cyritestin is a polymorphic protein that could include membrane-anchored and soluble forms. Southern blot analysis and characterization of human cyritestin genomic fragments revealed that the human genome contains two copies of the cyritestin gene instead of one as in the mouse. The human CYRN1 and CYRN2 genes were assigned to the region p12-21 of chromosome 8 and q12 of chromosome 16, respectively. Northern blot and RT-PCR analyses revealed that both human genes are expressed in the testis. Amino acid sequence comparisons between cyritestin and other members of the metalloprotease-disintegrin family of proteins suggested that human and mouse cyritestin and monkey tMDCI are homologous molecules.

Mouse Leydig insulin-like (Ley I-L) gene: structure and expression during testis and ovary development.

Leydig insulin-like protein (Ley I-L) is a novel member of the insulin-like hormone superfamily. We report here the isolation and expression of the mouse Ley I-L gene. The gene encodes a polypeptide of 122 amino acids that shows a relatively weak homology (54%) to human and porcine prepro-Ley I-L. However, the predicted B and A chain of the mature mouse Ley I-L exhibit similarities of 73% and 71% with human and porcine Ley I-L, respectively. Alignment of the 5' flanking region of the mouse gene with those of human and porcine did not exhibit any significant sequence homology. However, it contains the conserved sequence of the Ad4 binding site that is present in all promoter regions of steroidogenic P-450 genes and the Müllerian inhibitor substance gene and is recognized by steroidogenic factor 1. The Ley I-L gene is expressed at a high level in the testis and at a much lower level in the ovary. No transcripts could be detected in placenta prepared between days 10 and 19 of pregnancy. Ley I-L transcripts were first detected in fetal testis at 13.5 dpc. After birth, transcript levels remain constant during the following 3 weeks, increasing at the stage in which the first wave of round spermatids undergo spermiogenesis suggesting a functional role of the Ley I-L in early stages of spermatogenesis and germ-cell maturation. In the ovary, the expression of Ley I-L was first detected at day 6 after birth. The pattern of Ley I-L expression at various stages of the estrous cycle and during pregnancy showed a correlation with follicle development.

Spermatozoa lacking acrosin protein show delayed fertilization.

Acrosin (ACR), a serine proteinase located in the acrosome of the sperm, has been presumed to be involved in the recognition and binding of the sperm to the zona pellucida of the ovum and the sperm penetration through the zona pellucida. To examine the function of acrosin in vivo, we have generated mice carrying a mutation at the acrosin locus (Acr) through targeted disruption in embryonic stem (ES) cells. One chimeric male and female transmitted the targeted gene through their germ line. Homozygous Acr-/- mice are fertile and yield litters comparable in number and size to those of Acr+/+ mice. These data show that sperm of the homozygous Acr-/- mice are able to penetrate the zona pellucida, fertilize the ovum, and produce viable offspring. However, spermatozoa lacking acrosin protein show a delayed fertilization. One chimeric male which contained the targeted gene in 20% of its sperm transmitted only the Acr+ allele to its progeny. Furthermore, in vitro fertilization with equally mixed sperm cells of Acr+/+ and Acr-/- mice resulted in fertilization only with the Acr+ sperm cells. Incubation of oocytes with Acr+ or Acr- sperm show that the Acr+ sperm are faster to fertilize the oocytes than the Acr- sperm cells. These results suggest that Acr- sperm have a selective disadvantage when they are in competition with Acr+ sperm.