Developmental regulation of elastin gene expression.

Developmental regulation of elastin gene expression appears to be exerted primarily at the transcriptional level. Although the elastin gene promoter possesses features of "housekeeping" genes, these characteristics do not preclude transcriptional regulation as shown with a number of other gene promoters of this class. Direct evidence for transcriptional regulation has been obtained by nuclear run-on analysis of nuclei isolated from developing lung and aortic tissues and indirectly through elastin promoter activity in transgenic mice and transient tissue transfections of embryonic lung and aortic tissues. Although several different modulators have been proposed to control the developmental activation of elastin gene expression, only insulin-like growth factor I has been experimentally linked to increased transcription by in vivo studies. This link is specific for aortic smooth muscle cells in which cell cycle control appears intimately associated with elastogenesis. Recent studies suggest that progress in understanding developmental activation of the elastin gene lies in transgenic models and organ transfection assays that assess the direct relevancy of the modulators and cis- and trans-acting factors involved.