The KCTD15 gene has no current link to Mendelian disease, although flanking non-coding SNPs have been associated with obesity.1 2 Knockdown of the zebrafish orthologues kctd15a and kctd15b has demonstrated a role for KCTD15 in the development of the neural crest3 4 and for nephron segmentation in the kidney,5 and overexpression was associated with an attenuation of Wnt/beta-catenin signalling and repression of transactivation by the transcription factor TFAP2 (AP-2). Here, KCTD15 is linked to obesity due to melanocortin 4 receptor deficiency.