GDNF and Hirschsprung disease: Several genes have been implicated in the development of HSCR, including the RET proto-oncogene [7]–[9], endothelin receptor B gene (EDNRB) [10]–[17], endothelin-3 gene (EDN3) [18], [19], glial-cell-line-derived neurotrophic factor (GDNF) [20]–[22], SOX10[23], [24], NRTN[25], ECE1[26], ZFHX1B[27], PHOX2B[28], KIAA1279[29], TCF4[26].