Cell-Specific Regulatory Modules Control Expression of Genes in Vascular and Visceral Smooth Muscle Tissues

Abstract

Abstract-A novel approach with chimeric SM22␣/telokin promoters was used to identify gene regulatory modules that are required for regulating the expression of genes in distinct smooth muscle tissues. Conventional deletion or mutation analysis of promoters does not readily distinguish regulatory elements that are required for basal gene expression from those required for expression in specific smooth muscle tissues. In the present study, the mouse telokin gene was isolated, and a 370-bp (Ϫ190 to 180) minimal promoter was identified that directs visceral smooth muscle-specific expression in vivo in transgenic mice. The visceral smooth muscle-specific expression of the telokin promoter transgene is in marked contrast to the reported arterial smooth muscle-specific expression of a 536-bp minimal SM22␣ (Ϫ475 to 61) promoter transgene. To begin to identify regulatory elements that are responsible for the distinct tissue-specific expression of these promoters, a chimeric promoter in which a 172-bp SM22␣ gene fragment (Ϫ288 to Ϫ116) was fused to the minimal telokin promoter was generated and characterized. The Ϫ288 to Ϫ116 SM22␣ gene fragment significantly increased telokin promoter activity in vascular smooth muscle cells in vitro and in vivo. Conversely, a fragment of the telokin promoter (Ϫ94 to Ϫ49) increased the activity of the SM22␣ promoter in visceral smooth muscle cells of the bladder. Together, these data demonstrate that both vascular-and visceral smooth muscle-specific regulatory modules direct gene expression in subsets of smooth muscle tissues. Key Words: SM22␣ Ⅲ telokin Ⅲ gene regulation S mooth muscle cells arise from diverse populations of precursor cells during embryonic development, and the mechanisms that specify the smooth muscle cell phenotype in each of these populations of cells are largely unknown. All differentiated smooth muscle is characterized by the presence of unique isoforms of contractile proteins (such as smooth muscle ␣-and ␥-actin, myosin heavy chain, caldesmon, SM22␣, telokin, and calponin) that are not expressed in other tissue types. Analysis of the spatial and temporal pattern of expression of several smooth muscle proteins has revealed distinct patterns of expression of these proteins in different smooth muscle tissues during development. [1][2][3][4][5][6] This suggests that it is likely that distinct and overlapping mechanisms control the expression of genes in different smooth muscle tissues. The heterogeneity of regulatory mechanisms likely reflects the diverse embryological origins of smooth muscle cells in these different tissues.The cis-acting regulatory elements of the SM22␣, telokin, smooth muscle myosin heavy chain, smooth muscle ␣-and ␥-actin, and desmin genes have been shown to direct reporter gene expression to smooth muscle tissues in transgenic mice. [7][8][9][10][11][12][13][14] However, each of these promoters mediates a distinct pattern of transgene expression. For example a 2.4-kb fragment of the rabbit telokin promoter directs high levels of transgene express...

Proteomic Investigation on Chronic Bladder Irritation in the Rat

“…Transgelin is an actin cross-linking/gelling protein found in fibroblasts and smooth muscle and it plays a role in contractility, possibly by affecting actin filament organization 18 . Decreased transgelin expression was also observed in proteomic investigation of bladder outlet obstruction in rat 19 .…”

Mechanisms Responsible for the Promoter-specific Effects of Myocardin

“…The Ϫ55 to ϩ82 region in the telokin gene is highly conserved between species being 90% identical between mouse, rabbit, and human genes also suggesting that this region contains important regulatory elements (26). The identity of the key regulatory factors is currently unknown; however, it is tempting to speculate that these factors may comprise part of the transcription initiation complex that forms on each gene.…”

Hprt-targeted transgenes provide new insights into smooth muscle-restricted promoter activity

“…One of the limitations of this approach is that the site of integration of the transgene and the transgene copy number can greatly affect both the pattern and level of transgene expression. For example, in our analysis of telokin promoter transgenes, we observed that the majority of transgenic lines exhibited no detectable transgene expression (17). In addition, the pattern of transgene expression driven by an SM22␣ promoter was distinct in different transgenic lines, with most lines exhibiting artery-specific expression, whereas some showed additional expression in veins and in heart (17).…”

“…visceral smooth muscle; development; myosin light chain kinase; embryos; CArG element ANALYSIS OF TRANSGENE EXPRESSION driven by various fragments of smooth muscle-specific promoters has suggested that distinct cis-acting regulatory elements are required to direct expression of genes in different smooth muscle tissues (17,19,23,25,26,28). It is thus likely that distinct transcription regulatory pathways control the expression of genes in different smooth muscle tissues.…”