Figure 1A.Leptin receptor isoforms. Lepr-a (Ra) encodes the short form of the leptin receptor, and Lepr-b (Rb), encodes the long form. Exon 17 contains a Jak docking site (BOX1) common to Ra, Rb and Rc, while exon 18b contains additional motifs (BOX2 and STAT) required for STAT3 signaling. Soluble LEPR isoform Re lacks a transmembrane domain.