Hirschsprung DiseaseProto-Oncogene Proteins c-retEnteric Nervous SystemSOXE Transcription FactorsGlial Cell Line-Derived Neurotrophic Factor ReceptorsReceptor, Endothelin BWaardenburg SyndromeEndothelin-3Receptor Protein-Tyrosine KinasesMicrocephalyGlial Cell Line-Derived Neurotrophic FactorNeural CrestMultiple Endocrine Neoplasia Type 2aReceptors, EndothelinMutationFaciesPenetranceCarcinoma, MedullaryHigh Mobility Group ProteinsConsanguinityRectumAbnormalities, MultipleIntellectual DisabilityDrosophila ProteinsHaplotypesProto-Oncogene ProteinsGerm-Line MutationNerve Growth FactorsSyndromePedigreePolymorphism, Single-Stranded ConformationalDNA Mutational Analysis