MBD2 and obesity due to melanocortin 4 receptor deficiency: Both belong to the ALKB family of non-heme Fe(II)dioxygenases, and the former is not only involved in removing m6A modification but also contributes to human obesity (22), whereas the latter is a crucial demethylase located in nuclear-nascent RNAs, with maximal expression in the testis, heart, and kidney (23).