Heterogeneous isoactin gene expression in the adult rat gastrointestinal tract

Abstract

Background: Normal gastrointestinal development is a complex process involving the precise integration of multiple cell types. To gain a better understanding of these processes, the present study examined isoactin gene expression in the adult rat gastrointestinal tract. Methods: Northern blot analysis was performed on specified segments of the adult rat esophagus, stomach, small intestine, cecum, colon, rectum, and anus using actin isoform-specific complementary DNAs for all six vertebrate isoactins. Results: Smooth muscle and cytoplasmic isoactins were heterogeneously coexpressed in a segment-specific manner throughout the gastrointestinal tract. In addition, striated muscle isoactin expression was also detected in segments of the adult rat esophagus, stomach, colon, cecum, rectum, and anus. Histological analysis indicated that the adult rat esophagus, stomach, and anus contained significant quantities of skeletal muscle, providing a source for the striated muscle isoactins detected in these gut segments. A similar source of striated muscle isoactin expression in the cecum, colon, and rectum was not identified. Both coordinate and independent regulation of isoactin gene expression was observed in the gastrointestinal tract, although distinct patterns of autoregulation were absent. Conclusions: This study represents the first complete analysis of isoactin gene expression in the adult rat gastrointestinal tract and provides the basis for future studies designed to investigate the factors responsible for these processes.