Generation and analysis of Elf5-LacZ mouse: unique and dynamic expression of Elf5 (ESE-2) in the inner root sheath of cycling hair follicles.

The Elf5/ESE-2 transcription factor is a member of the Epithelium Specific Ets subfamily of Ets transcription factors. Expression of Elf5 has been known to be restricted to organs and tissues rich in glandular or secretory epithelial cells such as kidney and mammary gland as well as differentiated keratinocytes of the skin. We have engineered an Elf5-LacZ mouse strain in which the bulk of the coding region of the Elf5 gene has been replaced by the beta-galactosidase (LacZ) reporter gene and the neomycin resistance cassette. We show here that LacZ gene expression in Elf5-LacZ mice occurs in spatial and temporal patterns that mimic endogenous Elf5 expression as observed by strong X-Gal staining in the mammary luminal epithelial cells of heterozygous Elf5-LacZ animals. Our analysis also reveals previously undiscovered expression site for Elf5 in the differentiated cells of the inner root sheath of hair follicle. The generation of a novel Elf5 gene targeted mouse model harboring a LacZ reporter gene provides an advantage for in vivo studies of Elf5 due to the highly sensitive and easy in situ detection of LacZ gene expression through histochemical staining with X-Gal. Taken together, this study brings new insights into novel patterns of Elf5 expression likely correlating with functionally important control in hair follicle cycle.