CTDP1

This gene encodes a phosphatase that dephosphorylates the C-terminal domain of RNA polymerase II to promote transcription initiation and also dephosphorylates key substrates required for mitotic exit. Mutations cause congenital cataracts, facial dysmorphism, and neuropathy (CCFDN), an autosomal recessive disorder with early-onset features affecting the eyes, craniofacial development, and peripheral nervous system. The gene is highly intolerant to loss-of-function variants (LOEUF 0.529), indicating strong selective pressure against haploinsufficiency.