ABSTRACT
We have analyzed the expression profiles of ten genes in terms of testis development and organ specificity in rat, which were selected from 215 round spermatid-specific transcripts listed in a database. Out of the ten genes, we directed our attention to one gene, a germ cell-less like-2 gene (gcl-2), a homolog of Drosophila gcl gene (gcl), which is a component of the germ plasma and required for primordial germ cell formation. Rat genome contains duplicate rat gcl-2 (rgcl-2) genes, rgcl-2A and rgcl-2B, both of which are located at Xq13. RT-PCR analysis showed that the expression of the two genes was up-regulated during testis development and that they were predominantly expressed in the testis. Both rgcl-2A and rgcl-2B encode a protein of 498 amino acid residues, showing 90.56% identity at the amino acid level. Confocal laser scanning microscopy revealed that rgcl-2 protein was synthesized in the cytoplasm of elongating spermatids and at least a part of it was integrated into the middle piece of spermatozoa during spermiogenesis. Immunogold electron microscopy uncovered that rgcl-2 was localized at the abaxial (convex) surface of outer dense fibers (ODF) of rat sperm flagella. Therefore, we concluded that rgcl-2 is a new component of ODF in sperm flagella.