Idax is a 198 amino acid cytoplasmic protein that functions as a negative regulator of the Wnt signaling pathway through its interaction with the PDZ domain of Dvl-1. Containing one CXXC-type zinc finger, Idax is expressed at high levels in brain, with lower levels in testis and thymus. The gene encoding Idax maps to human chromosome 4, which represents approximately 6% of the human genome and contains nearly 900 genes. Notably, the Huntingtin gene, which is found to encode an expanded glutamine tract in cases of Huntington's disease, is on chromosome 4. FGFR-3 is also encoded on chromosome 4 and has been associated with thanatophoric dwarfism, achondroplasia, Muenke syndrome and bladder cancer. Chromosome 4 is also tied to Ellis-van Creveld syndrome, methylmalonic acidemia and polycystic kidney disease.