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Differences in regulation of testis specifc lactate dehydrogenase in rat and mouse occur at multiple levels.

The testis specific form of lactate dehydrogenase (LDH-C4) is encoded by a single locus, Ldh-c, and is tightly regulated in a tissue specific manner. Here we show differences in expression of Ldh-c between rat and mouse, and describe the levels at which regulation of this gene differs in the two species. Our results demonstrate that the Ldh-c message level is nearly nine fold greater in mouse testis and remains high post-meiotically. In contrast, rat Ldh-c mRNA is highest in primary spermatocytes and reduced in spermatids. The results of nuclear run-on assays indicate that the transcription rate of Ldh-c is only moderately higher in mouse than rat, and cannot account for a significant portion of the observed differences. Similar decay rates for both rat and mouse Ldh-c mRNA in actinomycin-D clearance assays indicate comparable cytoplasmic stabilities for the two messages. From these results we infer that nuclear prostranscriptional events contribute to the differences in Ldh-c message levels.

Animals↗

A functional truncated form of c-kit tyrosine kinase is produced specifically in the testis of the mouse but not the rat, pig, or human.

The complete nucleotide sequence of mouse-truncated mRNA of c-kit, tr-kit, has been determined using the CD1 strain. In this study, the nucleotide sequences of tr-kit from AKR/N, C57BL/6, and ICR strains of mice were determined and found to be identical, although many silent variations were found compared with the sequence in a database for CD1. Tr-kit protein consists of 12 amino acids encoded by the 16th intron and the following 190 amino acids of c-kit. In the sequences of tr-kit encoding 12 specific amino acids, no substitution was detected among the three strains and CD1. Furthermore, RT-PCR analysis clearly showed that tr-kit mRNA expression was present only in testis. No nucleotide mutation in two important regions of the presumptive promoter for tr-kit mRNA was detected within the 16th intron of the mouse strains examined. However, no functional form of tr-kit was found in the rat, pig, or human by sequence analysis and homology testing.

Amino Acid Sequence↗

Developmental distribution of the polyadenylation protein CstF-64 and the variant tauCstF-64 in mouse and rat testis.

Messenger RNA polyadenylation is one of the processes that control gene expression in all eukaryotic cells and tissues. In mice, two forms of the regulatory polyadenylation protein CstF-64 are found. The gene Cstf2 on the X chromosome encodes this form, and it is expressed in all somatic tissues. The second form, tauCstF-64 (encoded by the autosomal gene Cstf2t), is expressed in a more limited set of tissues and cell types, largely in meiotic and postmeiotic male germ cells and, to a smaller extent, in brain. We report here that whereas CstF-64 and tauCstF-64 expression in rat tissues resembles their expression in mouse tissues, significant differences also are found. First, unlike in mice, in which CstF-64 was expressed in postmeiotic round and elongating spermatids, rat CstF-64 was absent in those cell types. Second, unlike in mice, tauCstF-64 was expressed at significant levels in rat liver. These differences in expression suggest interesting differences in X-chromosomal gene expression between these two rodent species.

Aging↗

Insulin-like growth factor I (IGF-I) regulates endocrine activity of the embryonic testis in the mouse.

Insulin-like growth factor I (IGF-I) is important for gonadal and reproductive functions in mammals, although the physiological role of this growth factor during gonadal development in rodents remains largely unknown. Here, we examined the steady-state levels of IGF-I mRNA by the reverse transcriptase polymerase chain reaction (RT-PCR). IGF-I protein expression was also detected by Western blot. The effect of IGF-I as promoter of 17alpha-hydroxylase/C17-20 lyase and 17beta-hydroxysteroid dehydrogenase enzyme activity in vitro was evaluated by radioimmunoassay. Onset of IGF-I gene expression was on day E10 (urogenital ridge stage). IGF-I mRNA expression was markedly reduced on days E12 and E13 (testicular differentiation stage). IGF-I transcripts increased on day E14 and their transcription levels were maintained throughout the stages analyzed. Several IGF-I protein bands of 31-100 kDa were observed. Culture experiments demonstrated that 17alpha-hydroxyprogesterone and testosterone (T) secretion levels increased in the presence of IGF-I on days E11-E17. Additive effects of IGF-I plus (Bu)2cAMP were also seen during testicular development. It is proposed that IGF-I regulates the expression of key steroidogenic enzymes important for endocrine activity of the testis during prenatal development leading to establishment of the male phenotype and fertility.

17-Hydroxysteroid Dehydrogenases↗

A dual-function palindromic sequence regulates testis-specific transcription of the mouse lactate dehydrogenase c gene in vitro.

The promoter of the mouse lactate dehydrogenase c (Ldh-c) gene was assayed in an in vitro transcription system. Of the nuclear extracts isolated from several mouse tissues, only testis supported transcription from a 710 Ldh-c promoter fragment. Mutation analysis indicated that a canonical TATA box and a 30-bp palindromic sequence are both required for promoter activity. Liver nuclear extract (LN) can reduce transcriptional activity significantly when added to testis nuclear extract (TN). Deletion of the 3' palindromic sequence resulted in a low level of transcriptional activity in LN. Competition with a double-stranded synthetic palindromic oligonucleotide inhibited transcription in TN and rescued a low level of transcription in LN. Our results strongly indicate that the palindromic sequence contains both a negative element for repression in somatic tissues and a positive element for activation of the Ldh-c gene in testis.

Animals↗

The cellular distribution and kinase activity of the Cdk family member Pctaire1 in the adult mouse brain and testis suggest functions in differentiation.

Pctaire1, a member of the family of cyclin-dependent kinases, has been shown to be particularly abundantly expressed in differentiated tissues such as testis and brain. However, very little is known about the cellular and subcellular distribution and function of Pctaire1 protein(s), which is the focus of this study. We show that Pctaire1 encoded two major proteins of M(r) approximately 62,000 and approximately 68,000, found predominantly in testis and brain. Within these two tissues, Pctaire1 was most abundant in the cytoplasm of terminally differentiated cells, notably, the pyramidal neurons in brain and elongated spermatids in testis. Immunoprecipitation experiments further showed that a kinase activity toward myelin basic protein was associated with Pctaire1 in the adult testis and brain and that its activity was potentially regulated through association with regulatory partner(s). These results suggest that Pctaire1 kinase might have an important role in differentiated cells such as postmitotic neurons and spermatogenic cells.

Animals↗

Mapping of eight testis-specific genes to mouse chromosomes.

We previously identified eight testis-specific genes using antibodies raised against testicular germ cells. They are expressed during spermatogenesis and are presumed to be involved in testicular germ cell differentiation and sperm formation. We have mapped the genomic loci for these testis-specific genes using restriction fragment length variants in interspecific backcross mice. The calmegin gene (Clgn) was mapped to Chr 8. The synaptonemal complex protein gene 1 (Sycp1) probe hybridized with two sequences on different chromosomes; Sycp1-rs2 was mapped to Chr 3, whereas Sycp1-rs3 was mapped to Chr 7. The relaxin-like factor gene (Rlnl) was mapped to Chr 8, and collapsin response mediator protein 1 (Crmp1) was mapped to Chr 5. Three novel genes encoding testis-specific proteins A2 (Tsga2), A8 (Tsga8), and A12 (Tsga12) were mapped to chromosomes 3, X, and 10, respectively.

Animals↗

Structure and expression of the mouse testicular H1 histone gene (H1t).

A mouse genomic library was screened with a human testicular H1 (H1t) gene fragment. One phage containing the testis specific mouse H1t histone gene and its flanking regions was isolated. Northern blot analysis showed that the mouse H1t gene is expressed only in mouse testis at the stage of pachytene spermatocytes and that the H1t mRNA is not polyadenylated. This mouse H1t gene encodes a protein which differs from the somatic mouse H1 proteins, but is similar to the known H1t proteins from rat, and man.

Amino Acid Sequence↗

Expression of testicular germ cell genes identified by differential display analysis.

Using differential display reverse transcriptase-polymerase chain reaction (DDRT-PCR) we identified transcripts encoding for the RNA helicase mDEAH9, Ran binding protein 5 (RanBP5), and 3 novel complementary DNAs designated GC3, GC12, and GC14 in developing testicular germ cells. Sources of RNA for the initial DDRT-PCR screen were purified mouse type A spermatogonia, adult mouse wild-type testis, and W/W(v) mutant mouse testis. We identified cDNA fragments for mDEAH9, RanBP5, GC3, GC12, and GC14 in testis and type A spermatogonia samples from wild-type mice, but not in samples from the W/W(v) mouse testis. These same transcripts were absent in Northern blots of testis RNA from mice treated with busulfan 30 days prior, but were present in testis RNA from wild-type mice at 5, 15, 25, and 40 days of age. The mDEAH9 gene was expressed in many tissues, whereas RanBP5 and GC12 genes were expressed predominantly in the testis with much lower expression in other tissues. The expression of GC3 and GC14 were limited to the testis as evidenced by Northern blot and RT-PCR analyses. The mDEAH9 transcript was not detected in cultured interstitial cells but was found at low levels in cultured immature Sertoli cells, whereas the RanBP5, GC3, GC12, and GC14 transcripts were not detected in either cultured testicular interstitial cells or cultured Sertoli cells. RT-PCR analyses of isolated spermatogonia, pachytene spermatocytes, and round spermatids revealed that mDEAH9, RanBP5, GC3, GC12, and GC14 genes were expressed in all 3 cellular populations. In situ hybridization analyses of testis samples from 40-day-old mice localized expression of mDEAH9, RanBP5, GC3, GC12, and GC14 to the seminiferous tubules. RanBP5 expression appeared to be regulated during the cycle of the seminiferous epithelium, with the highest expression in stages III through VII. Expression of GC14 was greatest in the meiotic germ cell populations.

Animals↗

Sertoli cell junctions in the germ cell-free testis of the congenic mouse.

Intercellular junctions between the Sertoli cells in the germ cell-free testis of the congenic mouse were studied during ontogeny. In freeze-fracture replicas, these junctions are characterized by a great number of parallel occluding junctions, in which the particles are preferentially located in the center of the grooves in the E face. These particles appear to be arranged in discrete rows in both P and E fracture faces. In the initial stages of junction formation, large gap junctions with hexagonally packed particle aggregates and particle-free regions are observed. In the later stages, short segments of the occluding junctions are found associated with gap junctions. In later stages, the gap junctions diminish in size and number. These junctions are quite similar to those between Sertoli cells in the normal mouse and rat reported previously. The Sertoli cell junctions develop in the absence of the spermatogenic cells of this congenic mouse.

Age Factors↗

A transgenic analysis of mouse lactate dehydrogenase C promoter activity in the testis.

Transcription of the mouse testis-specific lactate dehydrogenase c (mldhc) gene is limited to cells of the germinal epithelium. Cloning and analysis of the mldhc promoter revealed that a 100-bp core promoter was able to regulate testis-specific transcription in vitro and in transgenic mice. Surprisingly, expression of the reporter in transgenic testes was limited to pachytene spermatocytes, whereas native LDH-C(4) was detected in pachytene and all later germ cells. To locate additional regulatory sequence that could recapitulate the native LDH-C(4) distribution pattern, we investigated the contribution of 5' and 3' flanking sequences to the regulation of LDH-C(4) expression. We found that transcription factor YY1 binds to the mldhc promoter, that the mldhc 3' untranslated sequence does not permit a postmeiotic expression of a beta-galactosidase reporter in transgenic mice, and that native mldhc mRNA is predominately meiotic, with only a low level of postmeiotic distribution. Our results suggest that the high level of LDH-C(4) in postmeiotic cells results from mRNA and protein stability.

3' Flanking Region↗

Normal testis determination in the mouse depends on genetic interaction of a locus on chromosome 17 and the Y chromosome.

We previously described a locus on chromosome (Chr) 17 of the mouse that is critical for normal testis development. This locus was designated "T-associated sex reversal" (Tas) because it segregated with the dominant brachyury allele hairpin tail (Thp) and caused gonads of C57BL/6J XY, Thp/+ individuals to develop as ovaries or ovotestes rather than as testes. To clarify the inheritance of Tas, we investigated the effects of T-Orleans (TOrl), another brachyury mutation, on gonad development. We found that gonads of C57BL/6J XY, Thp/+ and TOrl/+ mice develop ovarian tissue if the Y chromosome is derived from the AKR/J inbred strain, whereas normal testicular development occurs in the presence of a Y chromosome derived from the C57BL/6J inbred strain. From these observations we conclude that: (1) Tas is located in a region on Chr 17 common to the deletions associated with Thp, and TOrl, and (2) the Y-linked testis determining gene, Tdy, carried by the AKR/J inbred strain differs from that of the C57BL/6J inbred strain. We suggest that in mammals Tdy is not the sole testis determinant because autosomal loci must be genetically compatible with Tdy for normal testicular development.

Animals↗

Gene expression in mouse spermatogenesis during ontogenesis.

In this study, we evaluated the expression of genes probably involved in spermatogenesis in the mouse. We examined cytosolic chaperonin theta subunit (CCTtheta), Ngg1 interacting factor 3 like 1 binding protein 1 (NIF3L1 BP1) and apolipoprotein H (ApoH) expression during mouse onto-geny using RT-PCR. Testicular tissue was obtained from mice 3, 6, 8, 10, 12, 14, 18, 20 and 40 (adult) days after birth. For each mouse, one testis was used for histological examination, whereas RNA was extracted from the controlateral testis for expression analysis. RT-PCR analysis showed that CCTtheta gene expression was low until day 10, but increased drastically afterwards. At this age, spermatocytes started to be present in the mouse testis. Therefore, CCT protein could be involved in chromatin packaging and remodeling during spermiogenesis, as also suggested by other studies. NIF3L1 BP1 expression increased steadily during ontogenesis reaching maximum levels in the adult mouse when all germ cell stages are present. This finding suggests that NIF3L1 BP1 is a gene not expressed by a specific germ cell type. ApoH expression was very low or absent during prepuberal stages, whereas it was detectable in the adult testis when spermatogenesis was completed. This suggests that ApoH may be involved in clearing apoptotic bodies during spermatogenesis since apoptotic events increase during spermatogenesis. This study contributes to understanding the role played by genes important for spermatogenesis.

Animals↗

Identification of a novel testis-specific gene mtLR1, which is expressed at specific stages of mouse spermatogenesis.

A novel testis-specific gene termed mtLR1 was identified by digital differential display. Sequence analyses revealed that mtLR1 protein contains an amino terminus leucine-rich repeat domain and shows 33% similarities to PIDD which functions in p53-mediated apoptosis. Northern blot analysis showed that mtLR1 mRNA was specifically expressed in adult mouse testis, and RT-PCR results also showed that mtLR1 was exclusively expressed in adult testis and not in spermatogonial cells. The expression of mtLR1 mRNA was developmentally upregulated in the testes during sexual maturation and was, conversely, downregulated by experimental cryptorchidism in vivo. We also showed that the expression of mtLR1 mRNA was relatively highly sensitive to heat stress in vitro. The green fluorescent protein produced by pEGFP-C3/mtLR1 was only detected in the cytoplasm of spermatogonia cell line GC-1 after 24 h posttransfection. Immunohistochemical analysis revealed that the protein is most abundant in the cytoplasm of spermatocytes and round spermatids within seminiferous tubules of the adult testis. The time-dependent expression pattern of mtLR1 in postnatal mouse testes suggested that mtLR1 gene might be involved in the regulation of spermatogenesis and sperm maturation.

Aging↗

Radiosensitivity of testicular cells in the prepubertal mouse.

The effects of total-body X irradiation on the prepubertal testis of the CBA/P mouse have been studied. At either day 14 or day 29 post partum male mice were exposed to single doses of X rays ranging from 1.5-6.0 Gy. At 1 week after irradiation the repopulation index method was used to study the radiosensitivity of the spermatogonial stem cells. A D0 value of 1.8 Gy was determined for the stem cells at day 14 post partum as well as for the stem cells at day 29 post partum, indicating that the radiosensitivity of the spermatogonial stem cells in the prepubertal mouse testis is already comparable to that observed in the adult mouse. One, 2 or 3 weeks after irradiation total cell numbers per testis of Sertoli cells, Leydig cells, mesenchymal cells, macrophages, myoid cells, lymphatic endothelial cells, endothelium and perivascular cells were determined using the disector method. The Sertoli cells and interstitial cell types appeared to be relatively radioresistant during the prepubertal period. No significant changes in plasma testosterone levels were found, indicating that there is no Leydig cell dysfunction after exposure to doses up to 6 Gy during the prepubertal period. Taken together, the radioresponse of the prepubertal mouse testis is comparable to that of the adult mouse testis.

Age Factors↗

Comparison of lectin-staining pattern in testis and epididymis of gerbil, guinea pig, mouse, and nutria.

The testis and epididymis of gerbil, guinea pig, nutria, and mouse were studied after staining with seven rhodamine-conjugated lectins to disclose the distribution of glycoproteins with different sugar residues. In the testis, the lectins showed a variable affinity for Leydig cells, tubular basement membrane, cytoplasm, acrosome, and plasma membrane of maturing spermatids as well as for Sertoli cell extensions. During acrosomal development, the staining pattern showed characteristic changes with different lectins indicating a gradual processing of the glycoprotein components. The staining in the Sertoli cell extensions displayed a cyclic change linked with the release of spermatozoa. A nuclear staining was prominent in zygotene and pachytene spermatocytes in the mouse, weak in the nutria, but absent in gerbil and guinea pig. The principal cells of epididymis showed a lectin-stained Golgi region as well as a similar staining in the apical surface, microvilli, and tubular contents. This staining was most prominent in the caput/corpus regions with some interspecies differences indicating the epididymal areas active in secretion. Narrow cells active in absorption of testis-derived material were lectin-positive in the initial segment of mouse, gerbil, and nutria epididymis. Large light cells with a strong affinity for some lectins were found in the proximal cauda of gerbil and guinea-pig epididymis. In the nutria, corresponding cells were arranged as islands within the low epithelium. The distal cauda of mouse, gerbil, and nutria was the site for lectin-stained light cells interspersed among the low principal cells. It is concluded that the high and low light cells may be active in the absorption and phagocytosis of residual bodies/cytoplasmic droplets and surplus epididymal secretory material, respectively. Thus, labeled lectins formed a useful tool in the analysis of glycoprotein distribution, processing, secretion, absorption, and degradation in the male reproductive tissues.

Animals↗

A novel chimeric mitochondrial RNA localized in the nucleus of mouse sperm.

Six identical cDNA clones corresponding to an RNA of 1685 nucleotides that is enriched in mouse sperm compared with testis were isolated from a mouse testis cDNA library. The sequence of these clones corresponds to the 16S mitochondrial RNA plus an inverted repeat of 120 bp covalently joined to the 5' end of the RNA. By RT-PCR, it was demonstrated that this transcript, referred to as chimeric RNA, was present in mouse sperm, testis, liver, kidney, brain, and spleen. The absence of an equivalent sequence in mitochondrial DNA or as a mitochondrial pseudogene in total DNA extracted from sperm, testis, and somatic tissues suggests that the chimeric RNA is a post-transcriptional product, maybe resulting from a trans splicing reaction. The chimeric RNA was found by RT-PCR in total RNA extracted from purified sperm heads. This result was confirmed by in situ hybridization, which showed clear staining of the sperm nucleus with probes corresponding to sequences of the mitochondrial 16S RNA and the inverted repeat.

Animals↗