TCN2 and obesity due to melanocortin 4 receptor deficiency: Among 10 maternal SNPs with a significant gene × obesity interaction, three SNPs are in the GCLC gene, three SNPs are in the O-6-methylguanine-DNA methyltransferase (MGMT) gene, and the remaining four SNPs are in the glutathione S-transferase mu 2 (GSTM2), transcobalamin II (TCN2), cystathionine-beta-synthase (CBS), and DNA (cytosine-5-)-methyltransferase 3-like (DNMT3L) genes respectively.