ABSTRACT
We have identified integrin beta 6 (Itgb6) as a transcript highly enriched in skeletal muscle. This finding is unexpected because Itgb6 is typically associated with epithelial expression domains in normal tissue. Further we find that ITGB6 protein expression in muscle is post-transcriptionally regulated. Uninjured muscle expresses Itgb6 RNA but no ITGB6 protein is detectable. Muscle injury induces ITGB6 protein accumulation rapidly post-injury in myofibers adjacent to the site of injury. As regeneration of the injured muscle tissue progresses ITGB6 protein is found in newly formed fibers up to at least 15 days post-injury.
Subject(s)
Gene Expression Regulation , Integrin beta Chains/genetics , Integrin beta Chains/metabolism , Muscle, Skeletal/metabolism , RNA Processing, Post-Transcriptional , Animals , Gene Expression Profiling , Immunohistochemistry , Male , Mice , Muscle, Skeletal/injuries , Muscle, Skeletal/pathology , Muscular Diseases/genetics , Muscular Diseases/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Signal Transduction , Transforming Growth Factor beta/metabolismABSTRACT
Asthma is a multifactorial disease, in which the intricate interplay between genetic and environmental factors underlies the overall phenotype of the disease. Using a genome-wide scan for linkage in a population comprising of Danish families, we identified a novel linked locus on chromosome 1qter (LOD 3.6, asthma) and supporting evidence for this locus was identified for both asthma and atopic-asthma phenotypes in the GAIN (Genetics of Asthma International Network) families. The putative susceptibility gene was progressively localized to a 4.5 Mb region on chromosome 1q adjacent to the telomere, through a series of genotyping screens. Further screening using the pedigree-based association test (PBAT) identified polymorphisms in the OPN3 and CHML genes as being associated with asthma and atopic asthma after correcting for multiple comparisons. We observed that polymorphisms flanking the OPN3 and CHML genes wholly accounted for the original linkage in the Danish population and the genetic association was also confirmed in two separate studies involving the GAIN families. OPN3 and CHML are unique genes with no known function that are related to the pathophysiology of asthma. Significantly, analysis of gene expression at both RNA and protein levels, clearly demonstrated OPN3 expression in lung bronchial epithelia as well as immune cells, while CHML expression appeared minimal. Moreover, OPN3 down-regulation by siRNA knock-down in Jurkat cells suggested a possible role for OPN3 in modulation of T-cell responses. Collectively, these data suggest that OPN3 is an asthma susceptibility gene on 1qter, which unexpectedly may play a role in immune modulation.
