CCNA2 and obesity due to melanocortin 4 receptor deficiency: Based on the findings regarding the role of WTAP in cultured adipocytes, to assess its role in the development of obesity, we investigated the effect of WTAP reduction in vivo using Wtap+/− mice, since Wtap−/− mice are embryonically lethal at embryonic day 6.5, causing defective formation of endoderm and ectoderm (17, 29), the etiology of which is quite similar to that of cyclin A2-null mice (30).