Cloning of the cDNA encoding the urotensin II precursor in frog and human reveals intense expression of the urotensin II gene in motoneurons of the spinal cord

Urotensin II (UH) is a cyclic peptide initially isolated from the caudal ne urosecretory system of teleost fish. Subsequently, UII has been characteriz ed from a frog brain extract, indicating that a gene encoding a UH precurso r is also present in the genome of a tetrapod, Here, we report the characte rization of the cDNAs encoding frog and human UII precursors and the locali zation of the corresponding mRNAs. In both frog and human, the UII sequence is located at the C-terminal position of the precursor, Human UII is compo sed of only 11 amino acid residues, while fish and frog UII possess 12 and 13 amino acid residues, respectively. The cyclic region of UII, which is re sponsible for the biological activity of the peptide, has been fully conser ved from fish to human. Northern blot and dot blot analysis revealed that U II precursor mRNAs are found predominantly in the frog and human spinal cor d. In situ hybridization studies showed that the UII precursor gene is acti vely expressed in motoneurons. The present study demonstrates that UII, whi ch has long been regarded as a peptide exclusively produced by the urophysi s of teleost fish, is actually present in the brain of amphibians and mamma ls. The fact that evolutionary pressure has acted to conserve fully the bio logically active sequence of UH suggests that the peptide may exert importa nt physiological functions in humans.