TBL1XR1 and autism spectrum disorder: Mutations in the TBL1XR1 gene lead to a reduction in the ability of this pathway to recruit Wnt reaction element chromatin.[3,6,7] These mutations cause a variety of clinical phenotypes, including speech and motor delays, mental retardation, facial dysmorphism, hypotonia, microcephaly, hearing impairment, Pierpont syndrome, and autism spectrum disorder.[6,8]