| Research Abstract |
Spermiogenesis involves nuclear condensation, the elimination of most of the spermatid cytoplasm, and the formation of the tail and acrosome. We cloned haploid-specific cDNAs from a subtracted cDNA library that was generated by subtracting the mRNA of 17-day-old mouse testis from the cDNA of 35-day-old mouse testis. In this phase, more haploid-cell-specific genes are actively transcribed than was expected ; the expression pattern of each gene with various putative functions is strictly regulated. Elucidating the roles of haploid-germ-cell-specific genes will facilitate understanding of not only spermiogenesis but also of the differences between haploid and diploid cells. To identify the regulatory elements in haploid-specific genes, we isolated genomic DNA. One motif, the cyclic AMP response element (CRE), was present in the promoter regions of various specific genes and is functionally important, as reported previously. However, other genes did not contain CRE motifs. This suggests th
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e existence of different haploid-specific regulatory proteins that regulate the specific expression of these genes. Since many haploid-specific genes are CpG rich, epigenetic regulation via methylation might also contribute to the regulation of their expression. An interesting feature of haploid-specific genes is that a surprisingly high frequency lack introns. The intronless genes may be produced by specific mechanisms that exist in germ cells.
More than one tenth of human couples suffer from infertility, and half of these cases are attributable to deficient spermatogenesis in males. Although the molecular basis of most disorders of human spermatogenesis remains unclear, we hypothesized that deterioration in the effect of male germ-cell-specific genes gives rise to male infertility. Our new strategy is to compare the DNA sequences of fertile and infertile men. Since some germ cell-specific genes are intronless, it is easier to examine SNPs or detect mutations by direct DNA sequencing of the PCR-amplified products of chromosomal DNA from blood samples. Less
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