Carrier detection of deletions of the Hunter gene by in situ hybridization

Deficiency of the lysosomal enzyme alpha-iduronate sulphate sulphatase (IDS) causes the clinical manifestations of Hunter syndrome, an X-linked condition. In about 30% of male patients, the disease is due to a major deletion. Using a non-isotopic in situ hybridization (NISH) method, and a yeast artificial chromosome (YAC) probe, the Hunter gene was mapped to the terminal region of the human X chromosome, close to the Xq28 band. The NISH procedure was then applied to investigate the carrier status of female relatives of a Hunter patient known to have a deletion of the IDS gene. Unequivocal evidence that two female relatives were carriers of the deletion was obtained, demonstrating that the NISH method is a valuable diagnostic tool in genetic counselling of families with Hunter patients.