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Abstract

Cloning and characterization of rat spermatid protein SSP411: A thioredoxin-like protein 
Shi,Hui-Juan; Wu,Ai Zhen; Santos,Michelle; Feng,Zong-Ming; Huang,Li; Chen,Yong-Mei; Zhu,Kai; Chen,Ching-Ling C.
Journal of Andrology 25(4): 479-493
Publication date: 2004


In an attempt to identify new sperm-specific genes that areinvolved in sperm maturation, fertilization, and embryo development,such as the mammalian ortholog of the sperm-supplied proteingene, spe-11, in Caenorhabditis elegans, we cloned and characterizeda new spermatid-specific protein gene, ssp411, from adult rattestes. The ssp411 cDNA shared >85% sequence identity withan unnamed human protein, FLJ21347, and an uncharacterizedmouse testicular protein called transcript increased in spermiogenesis78 (TISP78). A 2.8-kb ssp411 mRNA was expressed in a testis-specificand age-dependent manner; the mRNA was evident at 28 days andremained at high levels throughout adulthood. An SSP411 proteinof molecular weight 88 000 was detected in testicular extractsby Western blot analysis. Ssp411 mRNA and SSP411 protein, asanalyzed by in situ hybridization and immunohistochemistry,were both expressed in a stage-dependent fashion during thecycle of the seminiferous epithelium. The ssp411 mRNA was predominantlylocalized to round and elongated spermatids, with maximal expressionat stages VII-XII. The SSP411 protein was mainly observedin elongated spermatids and reached its highest levels duringstages V-VI. A conserved thioredoxin-like domain was detectedin the N-terminal region of SSP411 and its orthologs. An analysisof the predicted 3-dimensional structural modeling and foldingpattern further suggested that SSP411 is identifiable as amember of thioredoxin family. In summary, we have identifieda new rat spermatid protein gene, ssp411, and its orthologsin human and mouse and demonstrated that SSP411 might belongto a testis-specific thioredoxin family. This suggests thatSSP411 may play a role in sperm maturation, fertilization,and/or embryo development, as has been shown in thioredoxinfamily.