Isolation and characterisation of a testis-expressed developmentally regulated gene from the distal inversion of the mouse t-complex

First messenger regulation of mammalian sperm function via adenylyl cyclase/cAMP

When released into an appropriate environment, mammalian spermatozoa begin to capacitate and then continue until fully capacitated and able to fertilize. During capacitation in vitro, some cells 'over-capacitate' and undergo spontaneous acrosome reactions; this would be highly undesirable in vivo since already acrosome-reacted spermatozoa are non-fertilizing. Recent studies have revealed that seminal plasma contains several small molecules that bind to specific receptors on the sperm plasma membrane and act as 'first messengers', causing biologically important changes in availability of the 'second messenger' cAMP. Fertilization promoting peptide (FPP), calcitonin and adenosine all regulate cAMP production, stimulating it in uncapacitated spermatozoa and then inhibiting it in capacitated cells; in contrast, angiotensin II stimulates cAMP throughout capacitation. The molecules that regulate cAMP appear to do so via G protein-modulated changes in membrane associated adenylyl cyclases (mACs). Both mouse and human spermatozoa have been shown to have Galphas and Galphai2, as well as several isoforms of mAC, located in the same regions as the specific receptors. Thus spermatozoa possess the required elements for several separate signal transduction pathways, many of which regulate mAC/cAMP and so maintain sperm fertilizing ability. In vivo, such responses could increase the chances of successful fertilization.

Susceptibility gene for non-obstructive azoospermia in the HLA class II region: correlations with Y chromosome microdeletion and spermatogenesis

We previously reported an association between the human leukocyte antigen (HLA) haplotype DRB1*1302-DQB1*0604 in the HLA class II region and non-obstructive azoospermia in Japanese men. To identify possible associations between the HLA-DRB1*1302-DQB1*0604 allele in the HLA class II region and azoospermia factor (AZF) deletion in the Y chromosome, we performed genomic polymerase chain reaction (PCR) analysis of the AZF region. We then determined spermatogenic impairment (Johnsen score) in testicular biopsy specimens from patients with or without the DRB1*1302-DQB1*0604 haplotype. The AZF microdeletion rate in patients with this haplotype was 3.85%, compared with 11.8% in others (no correlation). However, Johnsen scores in patients with the DRB1*1302-DQB1*0604 haplotype were 3.13 +/- 1.34 (mean +/- SD), compared with 3.70 +/- 1.51 in others (p < 0.05). While the DRB1*1302-DQB1*0604 haplotype acts independently from Y chromosome deletion, the haplotype might either act directly, or be functionally related to an unknown autosomal gene. In either case, this haplotype showed association with severe spermatogenic impairment.

Transmission Ratio Distortion in Mice

The most studied example of transmission ratio distortion (TRD) in mice is that of the t-complex. This is a variant region of Chromosome 17 which exists as a polymorphism in wild mice. Males heterozygous for a t-haplotype and a normal Chr 17 transmit the t-haplotype to >50% of their young, up to 99%. Homozygous males are sterile. The TRD produced by the t-complex is due to the action of three or more distorter genes (Tcd) on a responder gene (Tcr). t-Haplotypes are maintained intact by crossover suppression induced by four neighboring inversions, the Tcd and Tcr loci lying in different inversions. Sperm formation is normal in t/t males, but sperm function is impaired through gross defects in sperm motility. The responder gene has been identified as a fusion gene formed from a sperm motility kinase and a ribosomal S6 kinase. Three candidate distorter genes have also been identified as genes coding for dynein chains, and thus possibly involved in sperm flagellar function.

Calcitonin acts as a first messenger to regulate adenylyl cyclase/cAMP and mammalian sperm function

Calcitonin stimulates capacitation in uncapacitated mouse spermatozoa and then inhibits spontaneous acrosome loss in capacitated cells, responses similar to those elicited by fertilization promoting peptide (FPP), a peptide known to regulate the adenylyl cyclase/cAMP pathway. This study investigated the hypothesis that calcitonin also modulates this pathway. Calcitonin significantly stimulated cAMP production in uncapacitated spermatozoa and then inhibited it in capacitated cells; the magnitude of both stimulatory and inhibitory changes was similar to that obtained with FPP but the inhibitory responses to FPP preceded those of calcitonin. This possibly reflects the involvement of two different adenosine receptors in response to FPP compared with one calcitonin receptor. Calcitonin receptors were located on the acrosomal cap and the flagellum, the midpiece having a greater abundance than the principal piece. Although both calcitonin and adenosine receptors are found in the head and flagellum, there was no evidence for cross-talk between them. Chlortetracycline investigations to determine the minimum extracellular Ca(2+) requirement for responses to calcitonin revealed that calcitonin significantly stimulated capacitation in Ca(2+)-deficient medium but FPP did not. Calcitonin also significantly stimulated cAMP production under these conditions, and similarly preincubated suspensions, when diluted into +Ca(2+) medium, were significantly more fertile in vitro than untreated controls. These results indicate that calcitonin, like FPP, acts as a first messenger to regulate the production of cAMP and mammalian sperm function, but the differences in Ca(2+) requirements suggest that calcitonin and FPP may regulate different isoforms of adenylyl cyclase.

Native tesmin is a 60-kilodalton protein that undergoes dynamic changes in its localization during spermatogenesis in mice

Tesmin is a testis-specific protein. Four mouse tesmin cDNAs so far reported encode a testis-specific, metallothionein-like, 30-kDa protein (tesmin-30). An antibody against tesmin-30, however, detected a protein of 60 kDa (tesmin-60) from the mouse testis. To resolve the relationship between the two, the immunoprecipitated native tesmin-60 was sequenced. The result indicated that tesmin-30 is not full-length but is part of the C-terminal half of tesmin-60. The full-length cDNA (2.2 kilobases [kb]) encoding tesmin-60 (475 amino acid residues) and its genomic DNA (23 kb) were cloned and sequenced. A search of databases indicated that tesmin is a member of the CXC-hinge-CXC family. Immunohistochemistry indicated that tesmin exhibits dynamic subcellular localization changes during spermatogenesis. Before meiosis, it was localized in the cytoplasm of early to late spermatocytes and then translocated into the nucleus just before meiotic division. After meiosis, it appeared in spermatids, starting from the acrosomal vesicles, moving to the nuclear membrane and then to the caudal end as the spermatids elongated, and finally relocating into the cytoplasm. Oxidative stress by cobalt chloride, as well as by diethylmaleate, induced both premature translocation of tesmin from the cytoplasm to the nucleus and apoptotic signals in spermatocytes. The persistent existence of tesmin and its temporally and spatially dynamic localization suggest that tesmin is involved in multiple stages of spermatogenesis and spermiogenesis, possibly during sperm maturation and/or morphogenesis.

Capacitation state-dependent changes in adenosine receptors and their regulation of adenylyl cyclase/cAMP

This study was designed to localize adenosine receptors and to provide evidence that specific receptors are active only in either uncapacitated or capacitated mouse spermatozoa, where they play a role in regulating cAMP production. Using specific antibodies, stimulatory A(2A) receptors were localized primarily on the acrosomal cap region and the flagellar principal piece. Interestingly, the staining was much more pronounced in uncapacitated than in capacitated spermatozoa, suggesting capacitation-dependent changes in epitope accessibility. A(1) receptors showed a very similar distribution, but the staining was markedly greater in capacitated than in uncapacitated cells. After addition of purified decapacitation factor (DF) to capacitated cells, strong staining for A(2A) was regained, suggesting reversibility in epitope accessibility. Chlortetracycline analysis revealed that an agonist specific for A(2A) receptors had no detectable effect on capacitated cells, but after DF-induced decapacitation, the agonist then stimulated capacitation. That agonist also significantly stimulated cAMP production in uncapacitated cells, had no effect on capacitated cells, but regained the ability to stimulate cAMP in the latter following DF treatment. In contrast, an A(1) agonist inhibited cAMP in capacitated cells. These results indicate that specific adenosine receptors function in a reversible manner in one or other capacitation state, resulting in regulation of cAMP.

Fertilization promoting peptide — A possible regulator of sperm function in vivo

Fertilization promoting peptide (FPP), a tripeptide related to thyrotrophin releasing hormone (TRH), is found in seminal plasma. Recent evidence obtained in vitro suggests that FPP may play an important role in regulating sperm fertility in vivo. Specifically, FPP initially stimulates nonfertilizing (uncapacitated) spermatozoa to "switch on" and become fertile more quickly, but then arrests capacitation so that spermatozoa do not undergo spontaneous acrosome loss and therefore do not lose fertilizing potential. These responses are mimicked, and indeed augmented, by adenosine, known to regulate the adenylyl cyclase (AC)/cAMP signal transduction pathway. Both FPP and adenosine have been shown to stimulate cAMP production in uncapacitated cells but inhibit it in capacitated cells, with FPP receptors somehow interacting with adenosine receptors and G proteins to achieve regulation of AC. These events affect the tyrosine phosphorylation state of various proteins, some being important in the initial "switching on," others possibly being involved in the acrosome reaction itself. Calcitonin and angiotensin II, also found in seminal plasma, have similar effects in vitro on uncapacitated spermatozoa and can augment responses to FPP, suggesting that all four molecules may be involved in regulating availability of cAMP. It is plausible that these molecules have similar effects in vivo, affecting fertility by stimulating and then maintaining fertilizing potential. Either reductions in the availability of FPP, adenosine, calcitonin, and angiotensin II or defects in their receptors could contribute to male infertility. These exciting results may provide new approaches for diagnostic tests and treatments of certain categories of male infertility.

Fertilization promoting peptide and adenosine, acting as first messengers, regulate cAMP production and consequent protein tyrosine phosphorylation in a capacitation-dependent manner

Fertilization promoting peptide (FPP) and adenosine have been shown to act as first messengers, regulating availability of the second messenger cAMP by initially stimulating cAMP production in uncapacitated spermatozoa and then inhibiting it in capacitated cells. This study investigated possible capacitation-related changes in protein tyrosine phosphorylation in response to FPP and adenosine. Time-dependent changes in phosphorylation of proteins of approximately 30-140 kDa were observed in both uncapacitated and capacitated suspensions, the general level of phosphorylation being markedly greater in capacitated cells. In the presence of FPP, phosphorylation was stimulated in uncapacitated but inhibited in capacitated spermatozoa, compared with untreated control samples. Adenosine, cholera toxin, and CGS-21680, a stimulatory A(2a) adenosine receptor agonist, also stimulated phosphorylation in uncapacitated spermatozoa, while Gln-FPP, a competitive inhibitor of FPP, blocked responses to FPP. In capacitated cells, FPP's inhibition of phosphorylation was abolished when cells were treated with FPP in the presence of pertussis toxin. Consistent with the capacitation-dependent effects of FPP and adenosine on cAMP production, these results support the hypothesis that FPP and adenosine modulate sperm function by regulating the AC/cAMP signaling pathway and, consequently, protein tyrosine phosphorylation. Of particular significance is the identification of several phosphoproteins showing FPP-induced alterations in phosphorylation. In uncapacitated spermatozoa, proteins of approximately 116, 95, 82, 75, 66, 56, and 42 kDa showed increased phosphorylation, while in capacitated cells, phosphoproteins of approximately 116, 95, 82, 75, 70, 66, 56, and 50 kDa showed decreased phosphorylation. This suggests that these particular proteins may be involved in stimulation and arrest of capacitation, respectively.

Physical mapping of male fertility and meiotic drive quantitative trait loci in the mouse t complex using chromosome deficiencies

The t complex spans 20 cM of the proximal region of mouse chromosome 17. A variant form, the t haplotype (t), exists at significant frequencies in wild mouse populations and is characterized by the presence of inversions that suppress recombination with wild-type (+) chromosomes. Transmission ratio distortion and sterility are associated with t and affect males only. It is hypothesized that these phenomena are caused by trans-acting distorter/sterility factors that interact with a responder locus (Tcr(t)) and that the distorter and sterility factors are the same because homozygosity of the distorters causes male sterility. One factor, Tcd1, was previously shown to be amorphic using a chromosome deletion. To overcome limitations imposed by recombination suppression, we used a series of deletions within the t complex in trans to t chromosomes to characterize the Tcd1 region. We find that the distorter activity of Tcd1 is distinct from a linked sterility factor, originally called tcs1. YACs mapped with respect to deletion breakpoints localize tcs1 to a 1.1-Mb interval flanked by D17Aus9 and Tctex1. We present evidence for the existence of multiple proximal t complex regions that exhibit distorter activity. These studies demonstrate the utility of chromosome deletions for complex trait analysis.

Evidence for major histocompatibility complex-mediated effects on spermatogenesis in humans

Studies in fertile and infertile populations suggest an influence of genes of the major histocompatibility complex (MHC) on reproduction, although it remains unresolved if MHC-mediated effects on fertility are based on direct immunological or non-immunological effects of human leukocyte antigen (HLA) genes or rather on defects in MHC-associated non-HLA genes which affect gamete quality and embryonic development. We analysed allele frequencies for HLA class II loci DQA1, DQB1 and DRB1 and HLA class II haplotype frequencies in couples with tubal and andrological infertility who were treated with assisted reproductive techniques. Males with severe andrological infertility had significantly different allele frequencies for all three HLA loci when compared to males with normozoospermia, whereas no difference was found in the females. Differences in allele frequencies were stronger when only males whose partners achieved pregnancies after assisted reproduction treatment were compared. In those subgroups, we could also observe significant differences in three locus HLA class II haplotype frequencies. In summary, patients with male factor infertility differ in their HLA class II allele constitution from males with normozoospermia, which suggests that genes identical to or located in close vicinity to HLA class II genes may influence spermatogenesis and male gamete function.

Both fertilization promoting peptide and adenosine stimulate capacitation but inhibit spontaneous acrosome loss in ejaculated boar spermatozoa in vitro

Both fertilization promoting peptide (FPP) and adenosine stimulate capacitation and inhibit spontaneous acrosome loss in epididymal mouse spermatozoa; these responses involve modulation of the adenylyl cyclase (AC)/cAMP signal transduction pathway. However, it was unclear whether these responses were restricted to the mouse or possibly common to many mammalian species. To address this question, the response of boar spermatozoa to FPP and/or adenosine was evaluated. FPP is found in nanomolar concentrations in seminal plasma of several mammals, but not the pig. When cultured in caffeine-containing Medium 199 for 2 hr, chlortetracycline fluorescence evaluation indicated that neither FPP nor adenosine stimulated boar sperm capacitation per se but did inhibit spontaneous acrosome loss. However, in caffeine-free medium, FPP and adenosine both stimulated capacitation and inhibited spontaneous acrosome loss, suggesting that boar spermatozoa have receptors for both FPP and adenosine. Gln-FPP, a competitive inhibitor of FPP in mouse spermatozoa, has recently been shown to inhibit mouse sperm responses to adenosine as well, suggesting that FPP receptors and adenosine receptors interact in some way. Used with boar spermatozoa, Gln-FPP also significantly inhibited responses to both FPP and adenosine. These responses suggest that mechanisms whereby FPP and adenosine can regulate sperm function, via AC/cAMP, are of considerable physiological significance. Mouse, human, and now boar spermatozoa have been shown to respond to FPP, suggesting that these mechanisms may be common to many mammalian species. We also suggest that the effects of FPP and adenosine could also be exploited to maximize monospermic fertilization in porcine in vitro fertilization.

A protein kinase encoded by the t complex responder gene causes non-mendelian inheritance

Males heterozygous for the t-haplotype form of mouse chromosome 17 preferentially transmit the t-chromosome to their progeny. Several distorter/sterility loci carried on the t-haplotype together impair flagellar function in all spermatozoa whereas the responder, Tcr, rescues t-sperm but not wild-type sperm. Thus, t-sperm have an advantage over wild-type sperm in fertilizing egg cells. We have isolated Tcr by positional cloning and show that it is a member of a novel protein kinase gene family, designated Smok, which is expressed late during spermiogenesis. Smok kinases are components of a signal cascade which may control sperm motility. Tcr has a reduced kinase activity, which may allow it to counterbalance a signalling impairment caused by the distorter/sterility loci. Tcr transgene constructs cause non-mendelian transmission of chromosomes on which they are carried, which leads to sex-ratio distortion when Tcr cosegregates with the Y chromosome.

Modulation of mammalian sperm function by fertilization promoting peptide (FPP)

Fertilization promoting peptide (FPP; pGlu-Glu-ProNH2) is produced by the prostate gland and secreted into seminal plasma. When added to uncapacitated mouse and human sperm suspensions, it stimulates capacitation as demonstrated by both cytological changes and increased fertilizing ability in vitro. When added to capacitated suspensions, FPP inhibits spontaneous acrosome loss but cells retain high fertility in vitro. Adenosine elicits similar responses to FPP in both uncapacitated and capacitated cells and FPP + adenosine has a greater effect on uncapacitated cells than either used individually. We have proposed that these two molecules modulate the same pathway (adenylate cyclase/cAMP) but act via different receptors. The structure of FPP is crucial for bioactivity: loss of the terminal amide group abolishes activity and substitution of the central glutamic acid can markedly alter activity. Most recently we have found that stimulation of TCP-11, the product of the mouse t-complex gene Tcp-11, elicits responses indistinguishable from those obtained with FPP and we have hypothesized that the protein TCP-11 is the receptor for FPP. The existence of a human homologue for Tcp-11 suggests that the gene product, in conjunction with FPP, could play an important role in human fertility.

Identification of human testis-specific transcripts and analysis of their expression in tumor cells

Tumor-specific antigens recognized by autologous T lymphocytes are encoded by genes, including those of the MAGE, BAGE, and GAGE gene families, that are expressed in a significant fraction of tumors of various types, but not in normal adult tissues, except for testis where they appear to be expressed in germ cells. Because male germ cells are known to express many genes that are not expressed in other normal adult tissues, we wished to determine whether most of these genes are occasionally activated in tumor cells. Representational difference analysis was used to obtain testis-specific transcripts. The expression of 15 testis-specific cDNA sequences was tested by RT-PCR in a series of tumor cell lines. Only one cDNA sequence showed a significant level of expression in some tumor cell lines. Remarkably, this cDNA clone proved to be a new gene of the MAGE family. These results suggest that MAGE, BAGE, and GAGE genes belong to a minor subset of testis-specific genes that is often activated in tumors of various types, whereas most testis-specific genes are either never or very rarely activated in tumors.

TCP-11, the product of a mouse t-complex gene, plays a role in stimulation of capacitation and inhibition of the spontaneous acrosome reaction

Tcp-11 is a candidate for a distorter gene within the t-complex on mouse chromosome 17; although t-complex genes appear to affect sperm function, relatively little is known about mechanisms whereby these genes might play a specific physiological role. We present evidence that the protein TCP-11 is found on the surface of mature epididymal spermatozoa. Although detected on both the acrosomal cap region of the head and the flagellum of acrosome-intact cells, it is absent from the heads of acrosome-reacted cells. When epididymal spermatozoa were incubated in the presence of anti-TCP-11 IgG Fab fragments for a total of 120 min and assessed using chlortetracycline fluorescence, we observed a stimulation of capacitation and an inhibition of spontaneous acrosome loss, suggestive of enhanced fertility compared with untreated suspensions. In vitro fertilization experiments confirmed that Fab-treated suspensions became fertile more quickly and then maintained high fertility. Because these responses were remarkably similar to those obtained using the TRH-related peptide FPP (fertilization promoting peptide; pGlu-Glu-ProNH2) and adenosine, we investigated responses to Fab fragments, FPP, and adenosine. Results indicated that the Fab fragments appear to work at the same extracellular site as FPP, one that is distinct from the adenosine site of action. Further evidence for this conclusion was obtained using pGlu-Gln-ProNH2, an FPP-related tripeptide known to competitively inhibit responses to FPP; as with FPP, pGlu-Glu-ProNH2 inhibited the stimulatory effect of Fab fragments in a concentration-dependent manner. From these results we suggest that TCP-11 may be the receptor for FPP and that the adenylate clyclase/cyclic AMP pathway may be the signal transduction pathway activated by interactions between extracellular effector molecules (e.g., Fab fragments or FPP acting as an agonist) and TCP-11. A mechanism such as this that promotes capacitation but inhibits spontaneous acrosome loss in vivo would play a very important role by helping to maximize the fertilizing potential of the few spermatozoa that reach the site of fertilization. The fact that there is a human homolog of Tcp-11 suggests that this gene could play an important role in regulation of human, as well as mouse, sperm function.

Identification of a male meiosis-specific gene, Tcte2, which is differentially spliced in species that form sterile hybrids with laboratory mice and deleted in t chromosomes showing meiotic drive

Tcte2 (t complex testes expressed 2) is a male meiosis-specific gene that maps to band 3.3 of mouse chromosome 17. Two distinct male fertility defects, hybrid sterility and transmission ratio distortion, have previously been mapped to this region. Hybrid sterility arises in crosses between different mouse species and the F1 generation males have defects in the first meiotic division and are sterile. Transmission ratio distortion is shown by males heterozygous for the t haplotype form of chromosome 17 and is a type of meiotic drive in which male gametes function unequally at fertilization. The Tcte2 gene expresses a coding mRNA and a number of putative non-ORF transcripts in meiosis I. A deletion of the 5' part of the locus abolishes Tcte2 expression on the t haplotype form of chromosome 17. Additionally, the series of putative non-ORF RNAs at the Tcte2 locus are differentially spliced in species that show hybrid sterility when crossed to laboratory mice. The identification of polymorphisms in t haplotypes and in different mouse species allows alleles of Tcte2 to be proposed as candidates for loci which contribute to both meiotic drive and hybrid sterility phenotypes. While theoretical considerations have previously been used to propose that speciation and meiotic drive involve alleles of the same genes, Tcte2 is the first cloned candidate gene to support this link at a molecular level.

An additional type of male sterility and inherited urinary obstruction in mice with the t-haplotype th7

The t-complex on mouse chromosome 17 results in transmission ratio distortion in males heterozygous for complete haplotypes, and sterility in those homozygous for semi-lethal or doubly heterozygous for complementing lethal haplotypes. This sterility is due to inability of spermatozoa to fertilize. The haplotype th7 is an unusual laboratory-derived haplotype, postulated to carry a small duplication of t chromatin. Males heterozygous for th7 show a new form of sterility, apparently due to failure to form copulation plugs during mating. This is accompanied by a strong propensity to acute urinary obstruction. It is suggested that both the failure to form copulation plugs and the urinary obstruction are due to some abnormality in function of the accessory sex glands, and are the result of incorrect dosage of a gene in the postulated duplication. The symbol Msu for male sterility and urinary obstruction is suggested for the locus concerned. Previously a recessive form of abnormal behaviour had also been attributed to this duplication.

Sperm from mice carrying two t haplotypes do not possess a tyrosine phosphorylated form of hexokinase

Mouse sperm contain a tyrosine phosphorylated form of hexokinase type 1 (HK1; Kalab et al., 1994: J Biol Chem 269:3810-3817) that has properties consistent with an integral plasma membrane protein. Furthermore, this tyrosine phosphorylated form of HK1 has an extracellular domain and HK1 is localized to both the head and flagellum of nonpermeabilized cells (Visconti et al., 1995c). We have characterized HK1 in mature sperm from sterile tw32/tw5 mice (mutant sperm) that have defects in motility and sperm-egg interaction (Johnson et al., 1995: Dev Biol 168:138-149). Immunoprecipitation of mouse sperm extracts with an antiserum made against purified rat brain HK1 demonstrates the presence of HK1 in mutant sperm. Various biochemical and immunofluorescence assays indicate that at least a portion of the HK1 present in these cells is an integral membrane protein with an extracellular domain located on the sperm head and flagellum. However, immunoblot analysis with anti-phoshotyrosine antibodies demonstrates that HK1 in mutant sperm is not tyrosine phosphorylated. Northern blot and RT-PCR analysis does not indicate any obvious abnormalities in the transcription of somatic or germ cell-specific HK1 isoforms in mutant testes, and RFLP analysis of recombinant mice indicates that no genes specifying HK1 isoforms are located on chromosome 17. We have mapped the locus responsible for the lack of tyrosine phosphorylation of HK1 mutant sperm to the most proximal (to the centromere) of the four inversions within the t haplotype. A male sterility factor is located in this same inversion (Lyon, 1986: Cell 44:357-363). Since the mutant sperm are unable to complete fertilization, there could be a relationship between sterility and the lack of tyrosine phosphorylation of HK1 in these mutant sperm.

Characterization of the testis-specific gene 'calmegin' promoter sequence and its activity defined by transgenic mouse experiments

We have cloned the genomic DNA of calmegin [(1992) J. Biol. Chem. 269, 7744-7749] and analyzed its promoter region. It contained GC-rich sequences and potential binding sites for AP 2 and Sp 1, but lacked the TATA sequence. The 330 bp 5' flanking sequence of calmegin genomic DNA fused with the CAT gene was used for the study of promoter activity in transgenic mice. The CAT gene activity was detected exclusively in testes, indicating that the 330 bp calmegin 5' sequence was sufficient for the testis-specific expression. The existence of testicular nuclear factors specifically bound to the putative promoter sequence was also demonstrated.

The mouse t-complex gene, Tcp-11, is under translational control

The mouse t-complex is known to harbour genes which affect male fertility. Tcp-11 is a t-complex gene which is only expressed in male germ cells and from its position is a candidate for a distorter, one of the two types of genetic element involved in transmission ratio distortion. Antibodies raised to TCP-11 protein made in E. Coli were used on thin sections of testis and shown to recognise late spermatids. On Western blots the antibodies bound to a 68-kD protein present in protein extracts from testis. No specific signal could be detected using the antibody on protein extracts from other mouse tissues. Following gentle lysis of the germ cells and fractionation on sucrose gradients, all the material recognised by the anti-Tcp-11 antibody was found to be soluble and unassociated with any membrane fraction or organelle. A comparison of the time course of expression of the Tcp-11 mRNA and the TCP-11 protein revealed that expression of this gene is under translational control.

High-level expression in male germ cells of murine P68 RNA helicase mRNA

The complete cDNA coding for mouse P68 RNA helicase was cloned and its nucleotide sequence was determined. The sequence is about 95% identical to the human equivalent. Whereas the 5'-untranslated region is less conserved (71%), the 3'-ends of mouse and human mRNAs are nearly identical. Between stop codon and poly(A)-tail both sequences are 97% conserved. At the level of amino acid sequence, the similarity of both, mouse and human, DEAD box family proteins is as high as 98%. In situ hybridizations using cDNA subfragments as probes revealed a testis-selective expression of P68 RNA helicase mRNA. The signal was restricted to late pachytene spermatocytes and haploid spermatids. Northern blot analyses corroborated these results but suggested that expression of related mRNA species occurs in a variety of other tissues.

A testis-expressed Zn finger gene (ZNF76) in human 6p21.3 centromeric to the MHC is closely linked to the human homolog of the t-complex gene tcp-11

A novel testis-expressed Zn finger gene (ZNF76) was identified by screening cDNA libraries with cosmids derived from 6p21. ZNF76 is a member of the GLI-Krüppel family of DNA binding proteins. It is conserved in mouse where transcription in testis is initiated at Day 20 after birth. The mouse tcp-11 gene is located in the distal inversion of the t-complex and is developmentally regulated in the same manner as ZNF76. The human homolog of tcp-11 was isolated to allow a precise chromosomal localization. By using a combination of somatic cell hybrids, radiation hybrids, metaphase and interphase fluorescent in situ hybridization, and pulsed-field gel electrophoresis, we mapped the two genes to the 6p21.2 to 6p21.3 region and linked them to each other within 300 kb of DNA, approximately 2 Mb centromeric to the major histocompatibility complex.

Deletion of mouse t-complex distorter-1 produces an effect like that of the t-form of the distorter

An allele of the mouse brachyury locus, T22H, had been shown previously to involve a deletion of several markers in the proximal part of chromosome 17, and almost certainly includes deletion of the t-complex distorter gene Tcd-1. The effects of T22H on transmission ratio distortion and male sterility caused by the t-complex were compared with those of a partial t-haplotype th51, which carries the t-form of the distorter Tcd-1t. In combination with the complete haplotype tw32, T22H caused severe impairment of male fertility, but males of genotype T22H/t6 or T22H/th51 were normally fertile. These results were very similar to those obtained when th51 was in combination with the same haplotypes. In effect on transmission ratio T22H was again similar to th51, in that it produced a marked increase in the transmission of the haplotype t6. To test whether the effects of T22H were due to deletion of elements other than Tcd-1, the effect of T22H on transmission of the partial haplotype th2 was compared with that of the deletion Thp. Again T22H markedly increased transmission of the t-haplotype and the effect was significantly greater than the small effect produced by Thp. It is concluded that deletion of the distorter Tcd-1 has an effect like that of the t-form of this distorter, Tcd-1t, and hence that Tcd-1t must be an amorph or hypomorph. It is speculated that other t-complex distorters, Tcd-2t and Tcd-3t, may also be amorphs or hypomorphs.(ABSTRACT TRUNCATED AT 250 WORDS)