A very short segment of the murine Ret promoter contains elements sensitive to in vitro neural cell differentiation.

Regulation of the murine Ret gene has only been partially studied, specifically cis-acting promoter elements and related transcription factors, although in vivo experiments have shown the ability of Ret 5' flanking sequences to drive expression of transgenic reporter genes. This work describes the characterization of a 387-bp fragment of the Ret 5' flanking sequence with the ability to activate expression of the LacZ gene in transfected cells, in which SP1 recognition elements played a fundamental role. Using P19 teratocarcinoma cells differentiated by retinoic acid treatment, we observed an induction of Ret mRNA accompanied by a decrease of SP1 binding due to its proteolytic cleavage.