OB-R map: (OB-R_l), long form of leptin receptor; (OB-R_s), short (6.4 variant) form. The short form of the receptor represents a splice variant of the receptor, which has a unique cytoplasmic domain following the lysine residue at position 891 (stops 5 amino acids after Lys⁸⁹¹). The reverse primers for the long and short isoforms of the receptor were designed to anneal to the unique sequences in the cytoplasmic portion of the receptor. → forward primer; ← reverse primer; SF, short form; LF, long form; ECD, extracellular domain; TM, transmembrane domain.