- A missense mutation (I278T) in the cystathionine beta-synthase gene prevalent in pyridoxine-responsive homocystinuria and associated with mild clinical phenotype. Shih, V.E., Fringer, J.M., Mandell, R., Kraus, J.P., Berry, G.T., Heidenreich, R.A., Korson, M.S., Levy, H.L., Ramesh, V. Am. J. Hum. Genet. (1995)