Krit1/cerebral cavernous malformation 1 mRNA is preferentially expressed in neurons and epithelial cells in embryo and adult

Abstract

Cavernous malformations are capillaro-venous lesions mostly located within the central nervous system (CCM/OMIM#116860) and occasionally within the skin and/or retina. They occur as a sporadic or hereditary condition. Three CCM loci have been mapped, and the sole gene identified so far, CCM1, has been shown to encode KRIT1, a protein of unknown function. In an attempt to get some insight on the relationship between KRIT1 mutations and CCM lesions, we investigated Krit1 mRNA expression during mouse development from E7.5 to E20.5 and in adult tissues, of both mouse and human origin. A ubiquitous Krit1 mRNA expression was detected from E7.5 up to E9.5. Then, it became progressively restricted from E10.5 to E12.5, to become detectable later essentially in the nervous system and various epithelia. Strong labelling was observed in neurons in the brain, cerebellum, spinal cord, retina and dorsal root ganglia. In epithelia, Krit1 mRNA expression was detected in differentiating epidermal, digestive, respiratory, uterine and urinary epithelia. A similar pattern of expression persisted in mouse and man adult nervous system and epithelia. Unexpectedly, in vascular tissues, expression of Krit1 was detected only in large blood vessels of the embryo.