Incidental prenatal detection of an Xp deletion using an anonymous primer pair for fetal sexing

We report on the incidental prenatal detection of an interstitial X-chromos omal deletion in a male fetus and his mother by fetal sexing with a primer pair recognizing an X-Y homologous locus (DXYS19), formerly unassigned on t he X chromosome. The proband asked for prenatal diagnosis because of her el evated age and risk of Duchenne muscular dystrophy (DMD). Prior to molecula r genetic testing for DMD, fetal sexing was carried out on DNA prepared fro m cultured amniocytes. PCR analysis revealed the expected Y-chromosomal pro duct, but did not show the constitutive X-chromosomal fragment. The absence of the X-chromosomal fragment in the fetus and on one X chromosome of the mother was confirmed by Southern hybridization of HindIII restricted DNA wi th probe pJA1165 (DXYS19). DXYS19X was mapped to Xp22.3 by combining severa l approaches, including: (1) analysis of somatic cell hybrid lines containi ng different fragments of the human X chromosome; (2) Southern hybridizatio n of a yeast artificial chromosome (YAC)-filter panel provided by the Resou rce Center/Primary Database (RZPD); (3) FISH analysis; and (4) re-evaluatio n of two patients with interstitial deletions in Xp22.3. The extent of the deletion in the fetus was estimated by further markers from Xp22.3 and foun d to include the STS gene. Mental retardation could not be excluded since s ome mentally retarded patients exhibited overlapping deletions. Copyright ( C) 2000 John Wiley & Sons, Ltd.