PORCINE SRY GENE LOCUS AND GENITAL RIDGE EXPRESSION

Porcine SRY gene locus was cloned through use of a strategy of anchore d polymerase chain reaction (PCR) amplification from a male pig genomi c DNA size-selected library constructed in a plasmid vector as well as 3' reverse transcription (RT)-PCR amplification of porcine genital ri dge SRY transcripts. In total, 1664 bp of genomic DNA and 106 bp of 3' cDNA are presented. The open reading frame of porcine SRY consists of 624 bp representing 208 amino acids (aa) with a centrally located HMG box domain of 79 aa, an amino-terminal region of 59 aa, and a carboxy terminal of 70 aa. Structurally, porcine SRY resembles human and bovi ne SRY more closely than it does mouse Sry, and it lacks the carboxy-t erminal activation domain seen in the mouse Sry molecule. Similar to h uman and bovine testicular SRY transcripts, the porcine SRY genital ri dge transcript has a relatively short 3' untranslated region (UTR), in contrast to the extended UTR of the mouse genital ridge Sry transcrip t. The porcine SRY gene is expressed within the cells of the genital r idge of the developing male pig embryo between Days 21 and 26 (e21-e26 ) of gestation, during which time the primitive gonads are bipotential , but not on Day e31, by which time male testis determination is histo logically evident.