Conditional Ptc1 knockout in vagal neural crest cells causes a reduced proliferation of enteric nervous system progenitors and intestinal hypoganglionosis

Abstract

In vertebrates, vagal NCC colonize the developing gut rostro-caudally giving rise to the neuron and glia progenitors of the enteric nervous system (ENS).Hh-/- mice showed patterning defects and reduction of neurons of the ENS. However, the molecular mechanisms by which Hh regulate ENS development are unclear. To investigate the cell-autonomous functions of Ptc1 on vagal NCC/ENS progenitors, we generated mouse strains with Ptc1 deleted in vagal NCC, and analyzed the ENS development in embryos and adults. Mice with homozygous knockout of Ptc1 in vagal NCC were generated by intercrossing of floxed Ptc1 mice with vagal NCC cre expressing mouse lines. In these conditional Ptc1 knockout mice, Ptc1-/- ENS progenitors colonized the gut normally, suggesting the ENS patterning defects in Hh-/- mice was attributed to the abnormal gut mesenchyme. Instead,we found reduced proliferative ENS progenitors, and reduced enteric neurons in mutant guts. Gli1 expression was not upregulated in Ptc1-/- ENS progenitors. Ptc2 was not upregulated in Ptc1-/- ENS progenitors, indicating that loss of Ptc1 activity in vagal NCC/ENS progenitors was not compensated by Ptc2 upregulation. Ptc1 siRNA treatment of cultured vagal NCC reduced the percentage of proliferative NCC,and Ptc1 knockdown in NCC did not induce Gli1 over-expression. Our data indicated that a deletion of Ptc1 in vagal NCC resulted in a reduced proliferation of the ENS progenitors giving rise to hypoganglionosis in adult mice, suggesting a specific cell-autonomous regulatory function of Ptc1 on the proliferation of ENS progenitors.