Homologous genes for X-linked chondrodysplasia punctata in man and mouse.

X-linked dominant chondrodysplasia punctata is a human gene defect characterized by punctate foci of epiphyseal calcification, cataracts, ichthyosis, and systematized atrophoderma. In a comparative study, the murine X-linked mutant 'bare patches' was found to display strikingly similar skeletal, ocular, and cutaneous anomalies. The human as well as the murine phenotypes occur exclusively in the female sex, apparently because the underlying mutations are lethal for male embryos. In both traits, the cutaneous lesions are arranged in a linear and blotchy pattern reflecting lyonization. The observed similarities constitute strong evidence that the two genes are homologous. The proposed homology is a further example of the evolutionary conservatism of the X-chromosome in mammals.