Altered expression of ano1 variants in human diabetic gastroparesis

Diabetes affects many organs including the stomach. Altered number and function of interstitial cells of Cajal (ICC), the gastrointestinal pacemaker cells, underlie a number of gastrointestinal motility disorders, including diabetic gastroparesis. In the muscle layers, ICC selectively express Ano1, thought to underlie classical Ca²⁺-activated Cl^- currents. Mice homozygous for Anol knock-out exhibit abnormal ICC function and motility. Several transcripts for Anol are generated by alternative splicing of four exons. Here, we report expression levels of transcripts encoded by alternative splicing of Anol gene in gastric muscles of patients with diabetic gastroparesis and nondiabetic control tissues. Expression of mRNA from two alternatively transcribed exons are significantly different between patients and controls. Furthermore, patients with diabetic gastroparesis express mRNA for a previously unknown variant of Anol. The 5' end of this novel variant lacks exons 1 and 2 and part of exon 3. Expression of this variant in HEK cells produces a decreased density of Ca²⁺-activated Cl^- currents that exhibit slower kinetics compared with the full-length Anol. These results identify important changes in expression and splicing of Anol in patients with diabetic gastroparesis that alter the electrophysiological properties of the channel. Changes in Anol expression in ICC may directly contribute to diabetic gastroparesis.