Numerous enzymes associated with H3K9me3, the mark associated with heterochromatin, including acetyltransferases (SRC‐1/Ncoa1), deacetylases (Hdac3), methyltransferases (Suv39 h1 and G9a/Ehmt2), and demethylases (Jhmdh2a/Kdm3a, Jmjd2c/Kdm4c), have been linked to fatty liver, diabetes, and obesity (Picard et al., 2002; Sun et al., 2012; Tateishi et al., 2009; Wang et al., 2013). The gene discussed is HDAC3; the disease is obesity due to melanocortin 4 receptor deficiency.