On The Spot e-News
Volume 4, Issue 1 | January 2009
In this issue:
- Expanded Prenatal Service
- Prenatal Clinical Vignette
- Characterization of Complex Chromosome Rearrangements
Signature Introduces Expanded Prenatal Service
Signature has released an enhanced microarray for the prenatal detection of chromosome abnormalities.
The enhanced PrenatalChip® targets over 100 discrete chromosomal regions, the gain or loss of which results in a genetic disorder, while minimizing coverage of regions of unknown clinical significance. The first of three testing options in Signature’ Prenatal Service, the PrenatalChip is recommended for pregnancies in which the suspicion of a chromosome abnormality is relatively low—for example, parental anxiety or advanced maternal age. Signature’s whole-genome BAC microarray, the SignatureChipWG , can be ordered if more coverage is required, especially in cases with abnormal findings by ultrasound. For pregnancies with an abnormal karyotype or suspicion of imbalance of a specific gene region, the SignatureChipOS® may be recommended.
"Pregnancy can be a time of great anxiety, particularly if a genetic disorder is suspected," said Justine Coppinger, Certified Genetic Counselor at Signature. "We approach prenatal diagnosis responsibly, balancing timely, comprehensive diagnoses with the desire to minimize anxiety over unclear results. We encourage physicians to discuss the most appropriate test for their patients with our certified genetic counselors."
Please visit our Prenatal Diagnosis Services page or visit our booth (#213) at the Society for Maternal-Fetal Medicine Annual Meeting Jan. 29th and 30th to learn more about Signature’s Prenatal Service.
Prenatal Clinical Vignette
The following vignette illustrates the utility of microarray-based comparative genomic hybridization (aCGH) for clinical management of a pregnancy and estimation of recurrence risks.
A 21-year-old woman was referred at 16 weeks’ gestation because alobar holoprosencephaly (HPE) was observed on ultrasound examination. The woman’s obstetrical history revealed one spontaneous abortion and one pregnancy terminated at 15 weeks’ gestation following detection of alobar HPE. Family history showed that the father’s brother had failure to thrive and autistic features. Karyotype analysis on the mother and fetus was normal.
Please visit our Clinical Vignettes page to see how aCGH effectively diagnosed the chromosome abnormality in this pregnancy.
Characterization of Complex Chromosome Rearrangements
A recent study by Signature demonstrates the importance of integrating multiple technologies—aCGH, FISH, and banding--for the characterization of complex chromosome rearrangements.
In the study, reported in Molecular Cytogenetics, researchers characterized a complex three-way unbalanced translocation (5;20;8)(q13;p11.2;p21) resulting in microdeletions on 5q31.2, 5q31.3, and 8p23.2 in a female with hearing loss and global developmental delay. Because of its complexity, the complex rearrangement could not be confirmed by traditional cytogenetic analysis, microarray analysis nor FISH independently. Two of the microdeletions initially went undetected by traditional cytogenetic analysis. Only after identification of the approximate breakpoints by microarray analysis was it possible to determine the location and order of the rearrangement within the patient’s genome using the appropriate FISH probes to locate the translocated sections of chromosomes 8p and 5q. These results demonstrate the successful integration of multiple cytogenetic techniques--karyotype, microarray, and FISH--is necessary in the diagnostic laboratory for the characterization of complex chromosomal rearrangements.