These 20 genes are 4930441H08Rik, 4930595O18Rik, Aff3, Angpt1, Atpsckmt, Cpped1, Erc2, Gfra1, Gm17131, Gm36633, Fam237b, Mast4, Or56b2j, Pced1a, Prr5l, Serpine2, Tecrl, Tmem132d, Trim24, and Zfp536. Of these, only four have been annotated with obesity-related ontologies: Gfra1, Or56b2j, Serpine2, and Tecrl. The remaining 16 might represent novel obesity candidates, especially 4930441H08Rik, Aff3, Fam237b, Gm36633, Pced1a, and Zfp536 with alleles differing between fat (our Fat line and NZO/HlLtJ) and lean lines (our Lean line and A/J). The gene discussed is MAST4; the disease is obesity due to melanocortin 4 receptor deficiency.