Increased complexity of Tmem16a/Anoctamin 1 transcript alternative splicing

We identified Tmem16a transcript variants consisting of alternative exons 6b, 10, 13, 14, 15 and 18. Our findings indicate that many of these exons are expressed in various combinations and that these splicing events are mostly conserved between mouse and human. In addition, we confirmed the expression of these exon variants in other mouse tissues. Additional splicing events were identified including a novel conserved exon 13b, tandem splice sites of exon 1 and 21 and two intron retention events.Our results suggest that Tmem16a gene is significantly more complex than previously described. The complexity is especially evident in the region spanning exons 6 through 16 where a number of the alternative splicing events are thought to affect calcium sensitivity, voltage dependence and the kinetics of activation and deactivation of this calcium-activated chloride channel. The identification of multiple Tmem16a splice variants suggests that alternative splicing is an exquisite mechanism that operates to diversify TMEM16A channel function in both physiological and pathophysiological conditions.Alternative splicing of pre-mRNAs is a powerful regulatory mechanism that can increase mRNA transcript variety and effect functional diversification of proteins [1]. Within the cardiovascular system, alternative splicing affects cardiac function by regulating proteins involved in cellular excitation, including ion channels [2-8].Calcium-activated chloride currents have been recorded in cardiac muscle cells from various species including mouse [9], and play an important role in the cardiac action potential [10-12]. In 2008, three independent groups identified Tmem16a as a strong candidate gene to encode (or at least a major component of) a calcium-activated chloride channel [13-15]. Tmem16a belongs to a family of ten mammalian paralogs (Tmem16 (a-h, j-k)) that are highly conserved membrane spanning proteins. In recombinant expression systems, Tmem16a (or Ano1) and Tmem16b (or Ano2) gen