A novel transgenic marker for migrating limb muscle precursors and for vascular smooth muscle cells

A unique pattern of LacZ expression was found in a transgenic mouse line, l ikely due to regulatory elements at the site of integration. Two new genes flanking the transgene were identified. At early stages of development, the transgene is transiently expressed in ventro-lateral demomyotomal cells mi grating from the somites into the limb buds. At late developmental stages a nd in the adult, lacZ staining marks vascular smooth muscle cells throughou t the vascular bed, with the exception of the major elastic arteries, and i n pericytes. No expression was detected in skeletal and smooth muscles. Dif ferent patterns of expression in vascular smooth muscles was observed at di stinct levels of the vascular tree, in arteries as well as in veins. Vessel injury, resulting in stimulation of smooth muscle cells proliferation and migration, is associated with transgene down-regulation. After the formatio n of neointima thickening, it is reactivated. This transgenic insertion may therefore be used as a useful marker to identify novel physiological cues or genetic elements involved in the regulation of the vascular smooth muscl e phenotype(s). It may also provide an experimental, tool for studying vasc ulature and the involvement of pericytes in regulating microvascular homeos tasis. (C) 2001 Wiley-Liss, Inc.