TAF1 and X-linked intellectual disability - psychosis - macroorchidism: In 2015, O’Rawe et al. (2015) found mutations in TAF1 were associated with X-linked syndromic mental retardation-33 (MRXS33), and knockdown of this gene in zebrafish resulted in a 10% reduction in the relative area of the optic tectum, suggesting a neuronal defect.