- Allelic heterogeneity in the COH1 gene explains clinical variability in Cohen syndrome. Hennies, H.C., Rauch, A., Seifert, W., Schumi, C., Moser, E., Al-Taji, E., Tariverdian, G., Chrzanowska, K.H., Krajewska-Walasek, M., Rajab, A., Giugliani, R., Neumann, T.E., Eckl, K.M., Karbasiyan, M., Reis, A., Horn, D. Am. J. Hum. Genet. (2004)