The mouse obese (ob) gene product (leptin), expressed specifically in adipose cells, regulates energy balance in mice. Both mouse diabetes (db) and rat fatty (fa) gene products are thought to play major roles in leptin signaling pathways in the hypothalamic area. Mutations of these genes in murines result in marked obesity and type II diabetes as part of a syndrome that resembles morbid obesity in humans. Reported herein are the cloning and sequencing of one of spliced variant forms of rat leptin receptor (OB-R) cDNA with a short intracellular domain. In the Zucker (fa/fa) rat, no changes in either the gene structure or the expression levels were observed. However phenotype-linked nucleotide alteration exists in the cDNA from Zucker (fa/fa) rat, which results in an amino acid substitution.