Molecular cytogenetic analysis of a de novo balanced X;autosome translocation: Evidence for predominant inactivation of the derivative X chromosome in a girl with multiple malformations

We report on the characterization of a de novo , apparently balanced translocation t(X;15)(p11.3;q26) detected in a girl with multiple congenital malformations. Replication banding studies on Epstein–Barr virus transformed peripheral blood lymphocytes revealed non‐random X chromosome inactivation with predominant inactivation of the derivative X chromosome. Using chromosomal fluorescence in situ hybridization (FISH), we located the breakpoints to a 30 kb region on the short arm of the X chromosome band p11.3 and to a 160 kb region defined by BAC RP11‐89K11 on the long arm of chromosome 15. Our data suggest that the disruption/disturbance of plant homeo domain (PHD) zinc finger gene KIAA0215 or of another gene ( RGN , RNU12 , P17.3 , or RBM10 ) in the breakpoint region on the X chromosome is not well tolerated and leads to the selection of cells with an active non‐rearranged X chromosome. © 2003 Wiley‐Liss, Inc.