Differential isoactin gene expression in the sphincteric and nonsphincteric gastrointestinal smooth muscles of the...

The sphincteric smooth muscle tissues of the gastrointestinal tract have been shown to possess mechanical properties distinct from the surrounding nonsphincteric smooth muscle tissues. Little is currently known regarding the molecular basis of this differential smooth muscle development and function. Actin is an important contractile protein whose expression has been linked to the normal development and function of smooth muscle tissues. The purpose of this study was to characterize isoactin gene expression in the sphincteric versus nonsphincteric smooth muscle tissues of the gastrointestinal tract. Northern blot analysis was performed on manometrically identified sphincteric and the flanking nonsphincteric smooth muscle tissues of the adult opossum. Quantitative analysis revealed a distinct pattern of isoactin gene expression in the sphincteric versus nonsphincteric smooth muscle tissues of the gut. The sphincteric smooth muscle tissues expressed significantly lower total quantities of isoactin mRNA than their surrounding nonsphincteric smooth muscle tissues. It is hypothesized that these differential patterns of isoactin gene expression may play a significant role in establishing the myogenic potential of the functionally distinct sphincteric and nonsphincteric smooth muscle tissues of the gut.