Intestinal dysmotility in a zebrafish () mutant model of autism.

Background And Aims: Autism spectrum disorder (ASD) is currently estimated to affect more than 1% of the world population. For people with ASD, gastrointestinal (GI) distress is a commonly reported but a poorly understood co-occurring symptom. Here, we investigate the physiological basis for GI distress in ASD by studying gut function in a zebrafish model of Phelan-McDermid syndrome (PMS), a condition caused by mutations in the gene.

Methods: To generate a zebrafish model of PMS, we used CRISPR/Cas9 to introduce clinically related C-terminal frameshift mutations in and zebrafish paralogues (). Because PMS is caused by haploinsufficiency, we assessed the digestive tract (DT) structure and function in zebrafish heterozygotes. Human mRNA was then used to rescue DT phenotypes in larval zebrafish.

Results: Significantly slower rates of DT peristaltic contractions ( < 0.001) with correspondingly prolonged passage time ( < 0.004) occurred in mutants. Rescue injections of mRNA encoding the longest human isoform into mutants produced larvae with intestinal bulb emptying similar to wild type (WT), but still deficits in posterior intestinal motility. Serotonin-positive enteroendocrine cells (EECs) were significantly reduced in both and mutants ( < 0.05) while enteric neuron counts and overall structure of the DT epithelium, including goblet cell number, were unaffected in larvae.

Conclusions: Our data and rescue experiments support mutations in as causal for GI transit and motility abnormalities. Reductions in serotonin-positive EECs and serotonin-filled ENS boutons suggest an endocrine/neural component to this dysmotility. This is the first study to date demonstrating DT dysmotility in a zebrafish single gene mutant model of ASD.