Identification of a new RTN3 transcript, RTN3-A1, and its distribution in adult mouse brain.

The Reticulon (RTN) family of proteins is thought to play important roles in the regulation of neuronal regeneration. In this study, we have identified a novel alternative splicing isoform of the RTN gene family, RTN3-A1, which contains an additional 2.3-kb exon. The transcripts of human and mouse RTN3-A1 (about 5.0 kb) were first discovered by database sequence mining and analysis, and verified by cloning and sequencing. Northern blot analysis of 16 human tissues with a common probe of RTN3 transcripts and a specific probe for RTN3-A1 demonstrated that human RTN3-A1 is expressed mainly in brain tissues with a weak expression in the skeletal muscle. With Western blot analysis, the expected 100-kDa RTN3-A1 protein was detected in mouse brain. In situ hybridization with a mouse RTN3-A1-specific cRNA probe revealed that the mouse RTN3-A1 mRNA was regionally expressed in the neurons of the cerebral cortex, hippocampus, hypothalamus, and cerebellum of the adult mouse brain. In contrast to the transcripts of RTN1 and RTN2, RTN3-A1 shares some significant similarity with RTN4-A in exon structure, tissue distribution, and brain expression profile. Since other reports have shown that RTN4-A inhibits neuronal outgrowth and restricts the plasticity of the central nervous system, we speculate that RTN3-A1 might play certain roles in the central nervous system.