Cloning and characterization of the human GFRA2 locus and investigation ofthe gene in Hirschsprung disease

The glial-cell-line-derived neurotrophic factor (GDNF) family receptors alp ha (GFR alpha) are cell surface bound glycoproteins that mediate interactio ns of the GDNF ligand family with the RET receptor. These interactions are crucial to the development of the kidney and some peripheral nerve lineages . In humans, mutations of RET or RET ligands are associated with the congen ital abnormality Hirschsprung disease (HSCR) in which nerves and ganglia of the hind gut are absent. As the GFR alpha family are required for normal a ctivation of the RET receptor, they are also candidates for a role in HSCR. The GFRA2 gene, which is required for the development of the myenteric ner ve plexus, is an excellent candidate gene for HSCR. In this study, we clone d the human GFRA2 locus, characterized the gene structure, and compared it with other GFRA family members. We further investigated the GFRA2 gene for mutations in a panel of HSCR patients. GFRA2 has nine coding exons that are similar in size and organization to those of other GFRA family genes. We i dentified six sequence variants of GFRA2, four of which did not affect the amino acid sequence of the GFR alpha -2 protein. Two further changes that r esulted in amino acid substitutions were found in exon 9 and were predicted to lie in the amino acid sequence encoding the glycosylphosphatidylinosito l-linkage signal of GFR alpha -2. There was no difference in frequency of a ny of the sequence variants between control and HSCR populations. Our data indicate that members of the GFRA gene family are closely related in intron /exon structure and in sequence. We have not detected any correlation betwe en sequence variants of GFRA2 and the HSCR phenotype.