GNAS and Obesity: For example, allele-specific deficiency of imprinted guanine nucleotide-binding protein, α-stimulating (GNAS) gene products led to various metabolic phenotypes: obesity and hypometabolic states (in maternal knockout of Gsα, or Gnas) and leanness with increased metabolic rate (in paternal knockout of XLαs, or Gnasxl) [5,6,7].