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1 May 2004 Rosbin: A Novel Homeobox-Like Protein Gene Expressed Exclusively in Round Spermatids
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Mammalian spermiogenesis is a complex process occurring in a highly coordinated fashion within the seminiferous tubules. To elucidate the molecular mechanisms controlling haploid germ cell differentiation, we have isolated haploid germ cell- specific cDNA clones from a subtracted cDNA library of mouse testis. One of these cDNAs, Rosbin, is 3.2 kilobases (kb) long and has an open reading frame of 2385 nucleotides encoding a putative protein of 795 amino acid residues. A computer-mediated homology search revealed that it contained a domain similar to that of homeobox genes. Northern blot analysis revealed a 3.2-kb mRNA expressed exclusively in male germ cells. Transcription of the Rosbin gene was not observed in prepubertal testis but became detectable after Day 23. By Western blot analysis the protein encoded by this gene had a molecular mass of 89 kDa, expressing specifically in the testis and localized to the nucleus of stages IV–VIII haploid round spermatids, predominantly at stages VII–VIII of spermatogenesis. ROSBIN is associated with and is most likely phosphorylated by protein kinase A. We suggest that it plays an important role in transcriptional regulation in haploid germ cells.

Tohru Takahashi, Hiromitsu Tanaka, Naoko Iguchi, Kouichi Kitamura, Yily Chen, Mamiko Maekawa, Hiromi Nishimura, Hiroshi Ohta, Yasushi Miyagawa, Kiyomi Matsumiya, Akihiko Okuyama, and Yoshitake Nishimune "Rosbin: A Novel Homeobox-Like Protein Gene Expressed Exclusively in Round Spermatids," Biology of Reproduction 70(5), 1485-1492, (1 May 2004).
Received: 2 December 2003; Accepted: 1 January 2004; Published: 1 May 2004

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