Identification of alternatively spliced multiple transcripts of 5-hydroxytryptamine receptor in mouse

5-Hydroxytryptamine receptors (HTRs) are coded by seventeen different genes in mouse. One of them is htr4 that codes for the HTR4 receptor, a G-protein coupled receptor containing seven transmembrane domains. In mouse, the gene is reported to contain 6 exons and 5 introns. Our present study reports the presence of four transcript variants of this gene encoding different N-termini. These transcripts are expressed in neuronal as well as non-neuronal tissues of mouse. We have identified five novel coding exons present at the 5' end of the gene which splice with the published internal exon in an alternative manner making a total of five transcripts, four new transcript variants (T1, T2l, T2s and T3) and one published earlier. All five transcripts encoding different N-termini were expressed in mouse brain. It was interesting to note the expression of only T3 transcript that was also detected in heart muscle and is the only htr4 transcript expressed in heart. For the first time a transcript of htr4 gene was detected in the heart of the mouse which might help us to make use of small laboratory animals to study HTR4 in heart. As this transcript is unique to the heart it can serve as potential therapeutic target for various cardiovascular disorders and dysregulation of heart rate, atrial contraction and atrial relaxation. These variants display heterogeneous properties in terms of the presence of signal peptide, acetylation, phosphorylation and glycosylation. Thus alternative splicing of htr4 producing heterogeneous N-termini increases the diversity of the receptor.