Increased Fibronectin Impairs the Function of Excitatory/Inhibitory Synapses in Hirschsprung Disease

Although approximately 50% of cases have a known genetic defect, the precise pathogenesis of Hirschsprung disease (HSCR) is still unclear. We recently reported that expression of fibronectin (FN), which is involved in the migration, colonization, and differentiation of enteric neural crest cells (ENCCs), is increased in aganglionic colonic segments obtained from patients. We hypothesized that abnormally high levels of FN might play a role in the etiology of HSCR. Here, to test this hypothesis, we investigated aganglionic, transitional, and ganglionic colon segments from 63 children with HSCR and distal colon from thirty healthy Wistar rats at embryonic day 20, in addition to in vitro studies with PC12 Adh neural crest cells. We measured the protein and mRNA expression levels of FN, together with a panel of excitatory (VGLUT1, GluA1, GluN1, PSD-95, and NL-1) and inhibitory (GAD67, GABA AR-α1, NL-2, and SLC32) synaptic markers. Expression of all these synaptic markers was significantly decreased in aganglionic colon, compared to ganglionic colon, whereas expression of FN was significantly increased. In a neural crest cell line, PC12 Adh, knockdown of FN with small-interfering RNA increased the expression of synaptic markers. Co-culture of colons from embryonic day 20 rats with RGD recombinant protein, which contains the RGD motif of FN, reduced the expression of excitatory and inhibitory synaptic markers. These results are consistent with the idea that the etiology of HSCR involves aberrant overexpression of FN, which may impair synaptic function and enteric nervous system development, leading to motor dysfunction of intestinal muscles.