PIK3R1 and obesity due to melanocortin 4 receptor deficiency: The LASSO regression models were built from data from obese and normal tissues, and the λ analysis indicated that the model achieved optimal predictive accuracy for obesity at λ = 4, leading to the identification of 4 core diagnostic genes, including HSD11B1, RXRG, G6PD and PIK3R1 (Fig 6A-B).