Cloning and tissue distribution of a novel isoform of the rat GABA(B)RI receptor subunit

We have identified a novel splice variant of the metabotropic GABA(B) recep tor (R) subunit I, designated GABA(B)R1f, from a rat hippocampus cDNA libra ry screen. GABA(B)R1f shares sequence homology with rat GABA(B)R1a, with th e exception of an in-frame deletion of exon 4, resulting in a 21 bp deletio n in the coding sequence of the N-terminal extracellular domain. In additio n, GABA(B)R1f also contains a 93 bp in-frame insertion in a region of the s equence corresponding to the second extracellular loop and the fifth transm embrane domain, similar to that found in rat GABA(B)R1c. While being ubiqui tously (but variably) expressed, reverse-transcription polymerase chain rea ction analysis revealed the GABA(B)R1f isoform to be most prevalent in peri pheral vs central tissues, suggesting a potential role for this novel isofo rm in either the mediation of inhibitory transmission in these various tiss ues, or in as yet defined actions unrelated to central synaptic regulatory mechanisms attributable to GABA(B)R. NeuroReport 12:833-837 (C) 2001 Lippin cott Williams & Wilkins.