Overexpression of the obese gene in the genetically obese JCR:LA-corpulent rat.

Expression of the obese (ob) gene in JCR:LA-cp rats was examined. A 360 bp fragment of the conserved region of the gene was obtained by RT-PCR using total RNA isolated from adipose tissues of Sprague-Dawley (SD), JCR:LA-cp obese and lean rats. The three gene fragments were sequenced and shown to be identical. They were over 90% identical to the mouse ob gene sequence. The amplified fragments encode for 120 amino acids and have a glutamine residue at position +49. The gene was shown to be expressed only in adipose tissues, both white and brown. A ten-fold increase in ob mRNA was detected in white adipose tissues of obese animals compared to the lean ones of the JCR-LA:cp strain of rat. Ob gene was expressed in adipocytes and preadipocytes from the obese rat whereas in the lean and SD rats, ob gene expression was found in adipocytes only. No ob mRNA was detected in preadipocytes from the lean or SD rats, indicating a differentiation or maturation-dependent expression in normal rats.