MicroRNA profiling during germline differentiation of mouse embryonic stem cells.

MicroRNAs are new classes of small non—coding regulatory RNAs which control degradation or suppress translation of its target mRNAs by sequence complementarity. Mature microRNAs are enriched in embryonic stem cells and play important roles in controlling stem cell self—renewal as well as control of differentiation. There is significant evidence that microRNAs are involved in the regulation of stem cell differentiation. The male mouse Embryonic Stem Cell line C57BL6/J with normal karyotype 46, XY was used for profiling microRNA expression in undifferentiated mouse embryonic stem cells (mESCs) and mESCs which were differentiated to germ line cells to determine and compare differences in microRNA expression before and after differentiation. Also, testis tissue samples of a 5—day—old mouse and a mature mouse was used as in vivo control. Profiling was performed by quantitative real—time PCR using locked nucleic acid microRNA—specific LNATM—enhanced primers. After data analysis and comparison of results profiled microRNAs expression, three microRNAs, mmu—miR—21, mmu—miR—21* and mmu—miR—16 showed 50.31, 43.76 and 46.77—fold change increase of expression, respectively, in differentiated mESCs in comparison with undifferentiated state with significant p—value (Average p—value p<0.001 for each members of microRNAs). Expression of Let—7 microRNA family increased in differentiated state when compared with undifferentiated mESCs (Average p—value<0.0001 for each members of family). The levels of expression all other profiled microRNAs were significantly higher in undifferentiated in comparison with differentiated mESCs and their expression was down regulated after differentiation. (Average p—value <0.003 for each members of microRNAs).

Overexpression of Lis1 in different stages of spermatogenesis does not result in an aberrant phenotype.

Previous studies showed that in the mouse mutant Lis1(GT/GT) gene trap integration in intron 2 of Lis1 gene leads to male infertility in homozygous Lis1(GT/GT) mice. We further analyzed this line and could confirm the suggested downregulation of a testis-specific Lis1 transcript in mutant animals in a quantitative manner. Moreover, we analyzed the gene trap mutation on different genetic backgrounds in incipient congenic animals and could exclude a genetic background effect. To gain further insights into the role and requirement of LIS1 in spermatogenesis, 3 transgenic lines were generated, that overexpress Lis1 under control of the testis-specific promoters hEF-1α, which is exclusively active in spermatogonial cells, PGK2, which is active in pachytene spermatocytes and following stages of spermatogenesis, and Tnp2 which is active in round spermatids and following stages of spermatogenesis, respectively. All 3 transgenic lines remained fertile and testis sections displayed no abnormalities. To overcome the infertility of Lis1(GT/GT) males, these transgenic Lis1-overexpressing animals were mated with Lis1(GT/GT) mice to generate 'rescued' Lis1(GT/GT)/Lis1(Tpos) males. 'Rescued' animals from all transgenic lines remained infertile, thus overexpression of Lis1 in different stages of spermatogenesis could not rescue the infertility phenotype of homozygous gene trap males.

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.

Failure of phospholipid hydroperoxide glutathione peroxidase expression in oligoasthenozoospermia and mutations in the PHGPx gene.

Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is a selenoprotein belonging to the family of glutathione peroxidases. PHGPx has long been considered a major antioxidant that, in cooperation with vitamin E, protects biomembranes. To determine the expression pattern of PHGPx mRNA in human, quantitative RT-polymerase chain reaction (PCR) analyses using RNA from different embryonal and adult tissues were performed. A predominant expression was found in testes. In spermatozoa, PHGPx was found to be localized in the mid-piece of spermatozoa. We studied the relationship between spermatozoa PHGPx expression, mutations in PHGPx gene and human oligoasthenozoospermia, a defect in which both the number and the motility of spermatozoa are significantly below normal. Spermatozoa specimens from 45 infertile males were analysed for fertility-related parameters according to World Health Organisation and were classified as suffering from oligoasthenozoospermia. Two patients (4.44%) showed no expression of PHGPx and in nine patients (20.00%), a reduced expression of the enzyme was observed. DNA sequences of various regions of the PHGPx gene (coding, 5'flanking region and intron 1) from these patients and 58 fertile volunteers were analysed for mutations by PCR amplification and direct sequencing. Sequence data revealed no cause/effect relationship for any of the variants. From these data it can be concluded that oligoasthenozoospermia is associated with a decrease in the level of expression of PHGPx in the spermatozoa of some infertile men (24.44%), but is not linked to mutations in PHGPx gene.

Mutation analysis in hereditary haemorrhagic telangiectasia in Germany reveals 11 novel ENG and 12 novel ACVRL1/ALK1 mutations.

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal-dominant disease characterized by recurrent epistaxis, mucocutaneous telangiectasias and visceral arteriovenous malformations. Mutations in endoglin (ENG) and activin A receptor type II-like kinase 1 (ACVRL1 or ALK1) have been found in patients with HHT. We have screened a total of 51 unselected German index cases with the suspected diagnosis of HHT. We identified 30 different mutations in 32 cases (62.7%) by direct sequencing. Among these mutations, 11 of 13 ENG mutations and 12 of 17 ACVRL1 mutations were not previously reported in the literature. Two of the ACVRL1 mutations were each shared by two families. An analysis of the genotype-phenotype correlation is consistent with a more common frequency of pulmonary arteriovenous malformations in patients with ENG mutations than in patients with ACVRL1 mutations in our collective.

[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.

Generation and characterization of a transgenic mouse with a functional human TSPY.

To generate an animal model that is suitable for the analysis of regulation and expression of human testis-specific protein, Y-encoded TSPY, a transgenic mouse line, TgTSPY9, harboring a complete structural human TSPY gene was generated. Fluorescence in situ hybridization and Southern analyses show that approximately 50 copies of the human TSPY transgene are integrated at a single chromosomal site that maps to the distal long arm of the Y chromosome. The transgene is correctly transcribed and spliced according to the human pattern and is mainly expressed in testicular tissue, with spermatogonia and early primary spermatocytes (leptotene and zygotene) as expressing germ cells. TSPY transgenic mice are phenotypically normal, and spermatogenesis is neither impaired nor enhanced by the human transgene. The present study shows that a human TSPY gene integrated into the mouse genome follows the human expression pattern although murine tspy had lost its function in rodent evolution millions of years ago.

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.

Targeted expression of SV40 large tumour antigen (TAg) induces a transient enhancement of spermatocyte proliferation and apoptosis.

In an attempt to determine the susceptibility of spermatocytes to malignant transformation by simian virus 40 (SV40) large tumour antigen (TAg), transgenic mice harbouring a chimeric gene composed of the SV40 TAg gene fused to the 1.4 kb promoter sequence of the human phosphoglycerate kinase 2 (PGK2) gene were generated. Northern blot analysis on RNA from different tissues indicated a specific transcription of TAg in the testis of PGK2-TAg transgenic mice. Reverse transcription-polymerase chain reaction and Western blot analysis on testes at different stages of development revealed that transcription and translation of the TAg gene starts in 12-day-old testis, which coincides with the appearance of pre-leptotene spermatocytes. Germ cells of transgenic mice showed no tendency toward transformation, but in testes of both 18- and 25-day-old transgenic mice, a significantly enhanced number of spermatocytes was found. In contrast, in 42-day-old transgenic mice no differences in the number of spermatocytes and spermatids were observed. The number of Sertoli cells was determined to be equal in transgenic and wild type mice. In-situ end labelling of fragmented DNA revealed a higher rate of apoptosis in testes of 18-day-old transgenic mice as compared with wild type mice. These results indicate that germ cell homeostasis in transgenic mice is maintained by an apoptotic mechanism.

A 74-bp promoter of the Tnp2 gene confers testis- and spermatid-specific expression in transgenic mice.

During the final stages of spermatogenesis, round spermatids undergo several morphological, biochemical, and physiological modifications which result in the formation of mature spermatozoa. One of these is the nuclear condensation, achieved by the replacement of somatic-type and testis-specific histones by transition proteins and protamines leading to cessation of transcription several days before the completion of spermiogenesis. Therefore, a strict temporal and stage-specific gene expression is necessary for the correct differentiation of round spermatids into mature spermatozoa. In this study, the 5' regulatory region of rat Tnp2 gene was investigated by primer extension analysis and transgenic mice study. Primer extension analysis revealed a transcription start site which lies 70 bp upstream of the translation start codon. By transgenic mice studies, we demonstrated that a 147-bp 5' untranslated region corresponding to the region -74 to +73 is sufficient to confer testis- and spermatid-specific expression of rat Tnp2 gene.

Assessment of promoter elements of the germ cell-specific proacrosin gene.

The testis-specific proacrosin gene encodes for a fertilization-promoting protein. In mouse and rat it is first transcribed in late pachytene spermatocytes and revealed to be translationally regulated. Former proacrosin promoter studies demonstrated that elements necessary for conducting a stage and temporal-specific expression of the gene are located within 0.9 kb upstream of the translational start codon. In the present study we analyzed putative cis-acting elements located in this promoter region for their specific binding properties to nuclear factors assumed to be involved in proacrosin gene regulation. Supplement of specific antibodies in electrophoretic mobility shift assays (EMSA) revealed that two Y-box proteins and the transcription factors CREM and YY1 interact with proacrosin promoter elements. The Y-box proteins, antigenically related to the frog Y-box proteins FRGY1 and FRGY2, bound to the Y-box (55-66 bp upstream of the ATG initiation codon) in brain and testis nuclear extracts, respectively. CREM bound to three elements (30-37, 252-259, and 717-724 bp upstream of ATG). The ubiquitous transcription factor YY1 bound to a conserved element in the central proacrosin promoter (457-473 bp upstream of ATG) and showed almost germ cell-specific truncates in EMSA. These results suggest that the identified factors are involved in proacrosin gene regulation.

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.

Mice deficient for spermatid perinuclear RNA-binding protein show neurologic, spermatogenic, and sperm morphological abnormalities.

Spermatid perinuclear RNA-binding protein (SPNR) is a microtubule-associated RNA-binding protein that localizes to the manchette in developing spermatids. The Spnr mRNA is expressed at high levels in testis, ovary, and brain and is present in these tissues in multiple forms. We have generated a gene trap allele of the murine Spnr, named Spnr(+/GT). Spnr(GT/GT) mutants show a high rate of mortality, reduced weight, and an abnormal clutching reflex. In addition to minor anatomical abnormalities in the brain, males exhibit defects in spermatogenesis that include a thin seminiferous epithelium and disorganization of spermatogenesis. Most of the sperm from mutant males display defects in the flagellum and consequently show decreased motility and transport within the oviducts. Furthermore, sperm from mutant males achieve in vitro fertilization less frequently. Our findings suggest that SPNR plays an important role in normal spermatogenesis and sperm function. Thus, the Spnr(GT/GT) mutant male mouse provides a unique model for some human male infertility cases.

Rat transition nuclear protein 2 regulatory region directs haploid expression of reporter gene in male germ cells of transgenic mice.

During spermiogenesis, the successive replacement of somatic histones by basic proteins, the transition nuclear proteins and protamines, allows normal sperm condensation. Transition nuclear protein 2 (TNP2) is transcribed postmeiotically in round spermatids. In order to determine regulatory flanking sequences responsible for stage specific expression of TNP2 gene, different transgenic mice were generated by microinjection of fertilized eggs. We demonstrate here that 525 bp of 5'- and 920 bp of 3'-flanking sequences of rat TNP2 gene could properly and efficiently direct chloramphenicol acetyltransferase gene expression to the postmeiotic male germ cells of transgenic mice. During male germ cell differentiation the first transgene transcripts were observed in round spermatids and translation started 6 days later in elongating spermatids, which is an evidence for posttranscriptional regulation of transgene expression. In contrast, transgenic mice bearing only the 525 bp 5'-flanking sequences of rat transition protein 2 gene and 3'-flanking sequences of the simian virus 40 large T antigen showed low levels of transgene expression in testis. From these results, it can be concluded that the 525 bp 5'-flanking sequences regulate the cell specific expression and the sequences located in 920 bp 3'-flanking region either enhance the transgene expression in the male germ cells or may have a posttranscriptional role in stabilizing the mRNA in addition to its function in delaying the mRNA translation. Using comparative alignment of 5'-flanking of TNP2 genes from different species, the putative regulatory sequences are identified.

Isolation and characterization of differentially expressed genes in invasive and non-invasive immortalized murine male germ cells in vitro.

In an attempt to elucidate the potential of premeiotic male germ cells to malignant transformation both the invasiveness and the differential gene expression of several putative tumor markers of the spermatogonia-derived cell line GC-1spg and the spermatocyte-derived cell line GC-4spc were analyzed. Studies, using RT-PCR analysis, of the expression pattern of the alkaline phosphatase isoenzymes which serve as markers for testicular germ cell tumors demonstrated that the expression of the endogenous mouse embryonic alkaline phosphatase (EAP) is upregulated in the GC-1spg cell line. Additionally, after transfection of GC-1spg cells and GC-4spc cells with a GCAP-CAT construct, an increased promoter activity of the human germ cell alkaline phosphatase (GCAP), the equivalent human isoenzyme of EAP, was shown in GC-1spg. Furthermore, an in vitro Matrigel invasion assay revealed a significant higher invasive potential of GC-1spg cells as compared to GC-4spc cells. Finally, a suppression subtractive hybridization on RNA of invasive GC-1spg cells and non-invasive GC-4spc cells was performed. In total, 31 cDNA sequences were isolated and further analyzed. Among these, 18 known sequences and 13 unknown sequences were determined. Northern blot analysis revealed that one unknown gene and eight known genes, namely integrin alpha 6, L6 antigen, annexin VIII, BVL-1 retrotransposon, protective protein, replacement variant histone 3.3, alpha-catenin and LPS-binding protein, are over-expressed in invasive GC-1spg cells. Taken together, both the enhanced invasive activity of GC-1spg cells and the upregulated expression of genes involved in the process of tumor progression suggest that the immortalized spermatogonia-derived cell line GC-1spg does have a higher potential to malignant transformation than the immortalized spermatocyte-derived cell line GC-4spc.

Isolation and characterization of a novel human gene, NIF3L1, and its mouse ortholog, Nif3l1, highly conserved from bacteria to mammals.

We report the cloning and characterization of novel human and murine genes NIF3L1 and Nif3l1 which are strongly homologous to the yeast Ngg1-interacting factor 3 homolog. Mouse Nif3l1 and human NIF3L1 encode predicted proteins of 376 amino acids and 377 amino acids, respectively. Northern blot analysis on RNA from different postnatal murine tissues showed a ubiquitous expression pattern of mouse Nif3l1 with a transcript of approximately 1.85 kb. RT-PCR analysis on prenatal mouse RNA and embryonic stem cell RNA demonstrated expression of Nif3l1 throughout embryonic development. Additionally, expression analysis on cell lines revealed strong overexpression of Nif3l1 in the spermatogonia-derived cell line GC-1 spg and in the teratocarcinoma cell line F9. The mouse gene was mapped to chromosome 1, region C. Human NIF3L1 consists of seven exons spanning 14.5 kb of genomic DNA and is located on chromosome 2q33. A fusion protein consisting of the GFP (green fluorescent protein) and the ORF of human NIF3L1 showed a localization of the predicted protein in the cytoplasm. In the N-terminal and C-terminal region, mouse Nif3l1 and human NIF3L1 are strongly homologous to proteins of other species, e.g. the recently cloned Drosophila symbol=anon-35F/36F gene with 41% amino acid identity and several proteins from yeast including the yeast Ngg1-interacting factor 3 homolog with 46% amino acid identity, the hypothetical protein YGL221c and yeast Ngg1-interacting factor 3 (Nif3) with 37% amino acid identity. Other proteins from lower organisms, e.g a conserved hypothetical protein from Ureaplasma urealyticum or a hypothetical protein SCC30.09c from Streptomyces coelicolor show approximately 25-30% amino acid identity in the two flanking regions of the protein. These similarities indicate a high degree of conservation of mouse Nif3l1 and human NIF3L1 from bacteria to mammals.

Immortalization of murine male germ cells at a discrete stage of differentiation by a novel directed promoter-based selection strategy.

We developed a novel promoter-based selection strategy that could be used to produce cell lines representing sequential stages of spermatogenesis. The method is based on immortalization and subsequent targeted selection by using differentiation-specific promoter regions. As an example for this approach, a new murine germ cell line (GC-4spc) was established using a vector construct that contains the SV40 large T antigen and the neomycin phosphotransferase II gene under the control of the SV40 early promoter and a spermatocyte-specific promoter for human phosphoglycerate kinase 2, respectively. The GC-4spc was characterized as a cell line at the stage between preleptotene and early pachytene spermatocytes. Transcription of three germ cell-specific expressed genes, Pgk2, proacrosin, and the A-myb proto-oncogene, were detected in the GC-4spc cell line using reverse transcription-polymerase chain reaction. Furthermore, TSPY (human testis-specific protein, Y-encoded) and PGK2 (human phosphoglycerate kinase 2) promoter regions showed different transcriptional activities in the GC-4spc cell line compared with the spermatogonia-derived cell line GC-1spg. Thus, our strategy could be used for immortalization of cells at specific stages of differentiation, allowing production of a series of cultured cell lines representing sequential stages of differentiation in given cell lineages.

Refinement of the expression pattern of a mouse homologue of the porcine 135-kDa alpha-d-mannosidase (MAN2B2).

In the article by Hiramoto et al. (1997) (Stage-specific expression of a mouse homologue of the porcine 135 kDa alpha-d-mannosidase (MAN2B2) in type A spermatogonia, Biochem. Biophys. Res. Commun. 241, 439-445) a new homologue to the porcine epididymis-specific 135 kDa alpha-d-mannosidase (MAN2B2) was cloned from a mouse testis cDNA library. Northern blot analysis with RNA of different tissues showed a testis-specific expression by using a mouse MAN2B2 oligonucleotide. In situ hybridization revealed that the mouse MAN2B2 transcript is localized exclusively in spermatogonia. In consequence to this it was proposed by Hiramoto et al. that the mouse MAN2B2 homologue could serve as a marker for spermatogonia. By repeating the published experiments we observed a different expression pattern of the mouse MAN2B2 gene. Northern blot analysis with either testicular RNA from prepubertal males or with testicular RNA from the W/W(v)-mutant mouse which lacks germ cells showed an expression of the MAN2B2 gene. Furthermore, Northern blot analysis with RNA from different somatic tissues revealed that the gene is ubiquitously expressed. Therefore, our refinement clearly demonstrates that the MAN2B2 mouse homologue is not specifically expressed in spermatogonia.

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.