The
earlier a gene acts in development, the more massive
the defect that follows its deletion
•Genes that lead to complete aganglionosis
when knocked
out
–Phox2b
–Sox10
–Ret/GDNF;GFRa1 (below esophagus)
•Genes that lead to limited lesions when
knocked out
–Mash-1
–Edn3/Ednrb
–NTN/GFRa2
–NT-3/TrkC