Expression of the calpastatin gene segment during spermiogenesis in human testis: an in situ hybridization study

Serum obtained from an infertile woman contained antibodies that agglutinate human sperm. The antibodies interacted with a sperm protein with an estimated M(r) of 17.5 kD. The cDNA coding the 17.5-kD protein was isolated from a human testis lambda gt11 expression library and identified as a segment of the calpastatin gene. Single-stranded 35S-labeled RNA probes were prepared from the calpastatin cDNA segment. Using the techniques of in situ hybridization, the calpastatin mRNA was located in spermatids of human testis. The results support a previous observation that the calpastatin segment is produced during spermiogenesis and suggest that transcription of the calpastatin gene occurred during the postmeiotic haploid stage of spermatogenesis.