Characterization of a novel mRNA expressed by neurons in mature brain

In previous studies, differential hybridization screening of an activated murine T-lymphocyte cDNA library identified an interleukin 2-responsive mRNA, designated F5, expressed in lymphoid tissues and brain only. We now report characterization of a full-length clone isolated from an adult mouse brain cDNA library. Neither the nucleic acid nor amino acid sequences demonstrated similarity to reported sequences. On Southern blotting, the protein coding sequence hybridized to genomic DNA from a variety of species. On Northern blotting, F5 mRNA was expressed in adult mouse brain, spinal cord, eye, and dorsal root ganglia but not in peripheral nerve. In situ hybridization studies demonstrated prominent expression by neurons in brain. F5 mRNA expression was undetectable in embryonic rat cerebral hemisphere and low until postnatal day 21. F5 is a novel mRNA selectively expressed by proliferating lymphocytes and mature neurons.