Abstract
A set of mouse lines expressing mCitrine via a piggyBac-derived enhancer trap were previously constructed to visualize different cell types in the nervous system, and it was found that mCitrine fluorescence in these lines changes in a tissue-specific manner with increasing age. This study found that mCitrine mRNA abundance in tissues of mice of different ages follows the same pattern as levels of fluorescence in the tissues examined, suggesting that modulation of mRNA transcripts causes alterations in fluorescence. mCitrine transcript abundance also exhibited sexual dimorphism in some tissues of mice shortly before sexual maturity, and neocortical and hippocampal mCitrine levels attained their lowest, final value at that age. These findings identify sexual maturation as a key regulator of mCitrine expression in these lines; this regulation may occur through the regulatory mechanisms normally operating on the locus of insertion or a novel mechanism for transposon regulation in postnatal brains.