Consistent with this finding, maternal exon A/B is unmethylated and the maternal A/B promoter is derepressed in patients with pseudohypoparathyroidism type-Ib [63, 89, 90], who are thought to have a lack of Gsα expression in the proximal tubule due to silencing of the maternal Gsα promoter (in addition to the silencing of the paternal Gsα promoter that occurs normally in the same tissue; see below for further discussion). Here, GNAS is linked to pseudohypoparathyroidism type 1B.