Notably, a variant altering this residue (E421K) was described and characterised in TUBB2B. 11 Interestingly, this variant in TUBB2B is associated with CFEOM and polymicrogyria, while most TUBB2B mutations are associated with polymicrogyria without CFEOM (OMIM 610031). The gene discussed is TUBB2B; the disease is congenital fibrosis of the extraocular muscles.