Expression of the SmN Splicing Protein Is Developmentally Regulated in the Rodent Brain but Not in the Rodent Heart

The SmN protein is a tissue-specific splicing factor which is closely related to the ubiquitous SmB splicing protein but which is expressed only in the adult brain and heart. SmN is also detectable albeit at a low level in both the embryonic brain and heart. During heart development, SmN levels remain constant while during rodent brain development the levels of SmN rise such that SmN replaces SmB as the predominant protein in adult brain. This increase in SmN levels is dependent upon a corresponding increase in the SmN mRNA which is detectable by in situ hybridization within neurons in virtually all areas of the adult brain.