HOXD13 and polydactyly: Various exome sequencing and targeted gene studies have implicated several genes in congenital limb defects, including polydactyly (e.g., GLI3, TWIST1, HOXD13, etc.), syndactyly (FGFR2, GLI3, HOXD13, GJA1, etc.), and ectrodactyly, e.g., TP6315,24.