Clinical and molecular characterization of overlapping interstitial Xp21-p22 duplications in two unrelated individuals.

Development and implementation of high-density DNA arrays demonstrated the important role of copy number changes on the X chromosome in the etiology of developmental delay and mental retardation (MR). We describe two unrelated patients with developmental delay due to similar interstitial duplications at Xp21-p22. The first patient is a 6-month-old male with multiple affected family members including many females. The second patient is a 5-year-old adopted female. In both patients, chromosome analysis and array comparative genomic hybridization (aCGH) showed duplications of overlapping regions at Xp21-p22. The duplicated segments contain numerous genes associated with MR, including AP1S2, NHS, CDKL5, RPS6KA3, SMS, and ARX. Except for developmental delay, there is little phenotypic overlap between the male and the female patient. Additionally, the female patient and affected female relatives of the male patient have variable severities of cognitive impairment, likely due to different X-inactivation patterns and effects of other, nonduplicated genes important for normal development. These cases illustrate that increased gene dosage of X-linked MR genes lead to cognitive impairment. Precise delineation of chromosome rearrangements by aCGH and identification of genes within duplicated segments helped in establishing genotype-phenotype correlations for each of our patients, in comparing them to each other, as well as with previously reported cases of Xp21-p22 duplications. However, we show that even with detailed molecular characterization, phenotype prediction remains challenging in patients with structural abnormalities of the X chromosome.

Array-based comparative genomic hybridization (aCGH) in the genetic evaluation of stillbirth.

This study examined the utility of array-based comparative genomic hybridization (aCGH) in detecting genetic abnormalities associated with late pregnancy loss. Comparisons were made with classic cytogenetics to test whether aCGH represents a superior methodology for the clinical evaluation of stillbirth. Stillborn infants were selected for aCGH testing from the Wisconsin Stillbirth Service Program (WiSSP) database and tissue bank, based on abnormal clinical findings (presence of at least two abnormalities of two different organs or parts of the body). aCGH analysis was successfully completed in 15 cases which met the clinical criteria and for which sufficient amount of high quality DNA was recovered from archival material. The testing was performed using commercially available 1 Mb BAC arrays. Among 15 tested stillborns, aCGH detected two abnormalities (trisomy 21 and an unbalanced translocation between chromosomes 3 and 10), for an overall detection rate of 13% in stillborns with malformations who had normal or unobtainable cytogenetic results. This preliminary study supports the clinical value of aCGH testing in diagnostic evaluation of stillborns with congenital anomalies.