OVEREXPRESSION OF BETA-SUBUNIT OF THYROID-STIMULATING HORMONE IN MEISHAN SWINE IDENTIFIED BY DIFFERENTIAL DISPLAY

Anterior pituitary gland RNA isolated from Meishan (MS) and White Comp osite (WC) sexually mature boars was compared by a newly developed met hod of differential expression cloning called differential display. A number of cDNAs were identified that differed distinctly in expression between these breeds. The gene for beta-subunit of thyroid-stimulatin g hormone (TSH-beta) was initially identified as more highly expressed in MS than in WC boars. Subsequently, RNase protection assays and TSH RIA were used to quantify the magnitude of differences in transcripti on and translation in both males and females. Mature MS pigs had three fold greater expression of TSH-beta (P < .05) and greater plasma TSH c oncentrations than mature WC pigs (P < .01). The cDNA cloning and sequ ence analyses indicated identity in TSH-beta mRNA between MS and WC ma les. Elevated plasma TSH concentration may contribute to MS pigs reach ing sexual maturity earlier than WC or other European breeds. The meth od used in this study provides a useful molecular tool 1) to detect di fferentially expressed genes, 2) to study genetic variation that occur s at the transcriptional level between individuals, populations, or br eeds; and additionally, 3) to identify candidate genes that control ec onomically important quantitative traits in livestock.