Submitted October 27, 2003
Returned for revision November 17, 2003
Accepted January 30, 2004
Gamete Biology
Identification and Characterization of Evolutionarily Conserved Pufferfish, Zebrafish, and Frog Orthologs of GASZ
Wei Yan ,
Lang Ma ,
Carolyn A Zilinski ,
and
Martin M Matzuk *
* To whom correspondence should be addressed. E-mail: mmatzuk{at}bcm.tmc.edu.
Abstract
We previously identified Gasz (a germ cell-specific gene encoding a protein containing four ankyrin repeats, a sterile-
motif, and a basic leucine zipper) in six mammalian species. Here, we report GASZ orthologs in pufferfish (Fugu rubripes), zebrafish (Danio verio), and frog (Xenopus laevis). Sequences of the three Gasz cDNAs were determined by database mining and 5'- and 3'-RACE followed by sequencing. The three orthologous vertebrate genes encode proteins structurally similar to mammalian GASZ, and contain the characteristic four ankyrin repeats (ANKs) and sterile- motif (SAM). Their ANK and SAM domains share 55%-74% and 38%-55% amino acid identity with those in human GASZ, respectively. Similar to human and mouse Gasz genes, pufferfish Gasz is composed of 13 exons, spanning approximately 12 kb, and flanked by Cftr at its 5'-end and Wnt2 at its 3'-end. Northern and Western blot analyses detect frog Gasz only in testis and ovary. In situ hybridization and immunohistochemical analyses show that frog Gasz mRNA and protein expression is confined to pachytene spermatocytes in the testis and to oocytes in the ovary. In frog oocytes, GASZ protein appears to localize to a cytoplasmic structure resembling the Balbiani body, a postulated mRNA transport organizer in the cytoplasm. The high evolutionary conservation and germ-cell specificity suggest that GASZ plays an essential role in gametogenesis. The data presented here are important for future studies of the physiological roles of GASZ using fish and amphibians as
animal models.
Key words:
Gamete Biology •
Meiosis •
Oocyte development •
Spermatogenesis
