Four different ways of alternative transcripts generation mechanism in ADRA1A gene.

The ADRA1A (Alpha-1-adrenergic receptor) gene is one of the members of G protein-coupled receptor superfamily. Alternative splicing of this gene was known to generate four transcript variants which code four isoforms with various C-terminal regions. In this study, we conducted expression analysis and evolutionary characterization of alternative transcripts of the ADRA1A gene. In total, 10 alternative transcripts were identified using experimental approaches and in silico analysis. Among them, 6 alternative transcripts (T1, T2, T3, T4, T4-1, and T8) were validated by RT-PCR approaches and sequencing procedures. From the alternative splicing analysis, it could be assumed that there were three different alternative transcripts generation mechanisms and unknown mechanism. First one is the integration event of three different TEs (AluSc, L1MC5, and MIR3) as seen on the last exons of T3, T4, T4-1, T5, T6, and T7 transcripts. The second mechanism is a differential promoter usage on T8. The third one is a substitution event of the 3' splicing site during the primate evolution on T3. The last one is an unknown mechanism which was identified in the T4-1 transcript. Therefore, alternative transcripts of human ADRA1A gene occurred by four different ways, such as integration of TEs, differential promoter usage, substitution of splicing sites, and unknown mechanism.