The most prominent molecular alterations were identified for Ifi202b and Lefty1. Ifi202b which was recently identified as an obesity gene in our group by positional cloning carries a microdeletion that includes the promoter and the first exon of Ifi202b and results in a loss of Ifi202b expression in most tissues from B6 mice such as white adipose tissue, liver, and skeletal muscle [5], and as shown here, also in islets. This evidence concerns the gene LEFTY1 and obesity due to melanocortin 4 receptor deficiency.