SCG5 and obesity due to melanocortin 4 receptor deficiency: Additionally, if differential expression of Scg5 is causal for Wg5 (in HG2DF2 mice) and Wg2b (in B62D-3 mice), then its expression must correlate with growth traits and indeed its expression was significantly negatively correlated (P < 0.01) with body weight and obesity in both crosses (Table 2).