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GENOMIC ORGANIZATION OF THE SP22 GENE AND A UNIQUE PATTERN OF EXPRESSION IN SPERMATOGENIC CELLS
Citation:
WELCH, J. E., R. R. BARBEE, J. D. SUAREZ, N. L. ROBERTS, AND G. R. KLINEFELTER. GENOMIC ORGANIZATION OF THE SP22 GENE AND A UNIQUE PATTERN OF EXPRESSION IN SPERMATOGENIC CELLS. Presented at International Congress of Andrology, Montreal, Quebec, Canada, June 15-19, 2001.
Description:
GENOMIC ORGANIZATION OF THE SP22 GENE AND A UNIQUE PATTERN OF EXPRESSION IN SPERMATOGENIC CELLS.
JE Welch*, RR Barbee*, JD Suarez*, NL Roberts*, and GR Klinefelter. Reproductive Toxicology Division, NHEERL, U.S. EPA, Research Triangle Park, NC, USA.
Our laboratory has reported earlier that the amount of SP22 protein present on spermatozoa closely parallels the fertilizing ability of these cells. We have previously identified and sequenced two SP22 transcripts and demonstrated that expression of the rat SP22 gene produces a single 1.0 kb mRNA in somatic cells while both a 1.5 kb (SP22A) and a 1.0 kb (SP22b) transcripts are present in the rat testis. Northern blotting of total RNA from the prepubertal rat testis indicated that while the 1.0 kb SP22B mRNA was expressed throughout development, the 1.5 kb SP22A transcript appeared coincident with spermatocyte differentiation. Analysis of RNA from isolated spermatogenic cells confirmed that SP22A is expressed in pachytene spermatocytes and round spermatids. No SP22A transcript was detected in RNA samples from Leydig cells. SP22 has also been described as a contraceptive associated protein (CAP1) encoded by a single transcript of 1.6 kb. A close examination of the CAP1 sequence (Genbank #AJ007291) suggests that this discrepancy is due to a fusion of SP22 and hepatoma derived growth factor transcripts within the CAP1 sequence. The SP22 segment of the CAP1 cDNA also contains a deletion of 51 bp in the 5' untranslated region not found in the five SP22 clones sequenced. It is possible that this deletion indicates the presence of an alternatively spliced SP22 sequence. Products of the SP22 gene have been also been described in mammals by as a putative oncogene (DJ-1) and as an inhibitor of an RNA-binding complex (RS). An initial characterization of the human SP22 gene has identified 7 exons spanning 23,594 bp on chromosome 1. This abstract does not necessarily represent U.S. EPA policy.