Alternative splicing of the neurotrophin-3 gene gives rise to different transcripts in a number of human and rat tissues

The mouse neurotrophin-3 (NT-3) gene has been shown to contain two exons (e xon 1A and exon 1B) upstream of the single coding exon (exon 2). These upst ream exons are alternatively spliced to the coding exon, generating two dif ferent NT-3 transcripts. We investigated whether alternative splicing of tw o upstream exons also occurs in the human and rat NT-3 gene. It was found t hat the human and rat NT-3 gene also contains two exons upstream of the mai n coding exon and that alternative splicing of these upstream exons generat es two different NT-3 transcripts: transcript 1A and transcript 1B (TR1B). These two transcripts were widely expressed in several human and rat tissue s. Also, a third transcript, transcript 1A1C, derived from splicing of exon 1A to exon 1B before splicing to the coding exon was seen in a small numbe r of rat tissues. Previous quantification of neurotrophin-3 mRNA has not be en transcript-specific. Here we describe a transcript-specific semiquantita tive RT-PCR method allowing the quantification of TR1B in human tissues. We show that this is the major NT-3 transcript and that expression of this tr anscript was much higher in the adult when compared with the corresponding fetal tissues.