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Researchers at Signature Characterize Previously Unreported Microduplication

SPOKANE, Wash.--(BUSINESS WIRE)--Jun 2, 2008 - Microscopic deletions of chromosome 3q29 have been described recently in individuals with mental retardation and highly variable clinical features. All individuals reported to date have the same-sized deletion. Because this region of chromosome 3 is thought to be caused by recombination between flanking segments of highly repetitive DNA sequences, duplications of 3q29 should occur with the same frequency as deletions. However, with the exception of one three-generation family, no individuals with microduplications of 3q29 have been reported. Researchers at Signature Genomic Laboratories recently characterized 19 individuals with 3q29 microduplications and suggest that duplication alone may not account for the clinical features in those individuals.

In the study, published in the journal Molecular Cytogenetics, researchers identified 19 individuals with microduplications of 3q29 in almost 20,000 individuals with unexplained mental retardation and congenital anomalies referred to the laboratory for microarray testing. The clinical features of the individuals varied widely, with mental retardation the only feature common to all patients. Surprisingly, only five individuals had reciprocal duplications that were the same size and location as the 3q29 microdeletion; the remaining 14 duplications flank, span, or partially overlap the common deletion region. This suggests other factors besides the segmental duplications that cause the common-sized 3q29 deletions play a role in rearrangements of this region. Because some of the duplications were inherited from a clinically normal parent, the clinical significance of these duplications is unclear and may require an as-yet unidentified genetic modifier for medical problems to occur.

"Although further studies are required to determine what role, if any, these duplications play in the patients' clinical features, microarray analysis was essential for identifying this novel chromosome abnormality. Their highly variable clinical features -- and the lack of similar patients reported in the literature -- would have prevented their identification without this technology," said Dr. Blake C. Ballif, Ph.D., Director of Product Development and Research at Signature and lead author of the study. "These cases are an excellent example of how microarray technology can provide answers that traditional methods cannot."

About Signature Genomic Laboratories

Signature Genomic Laboratories, founded in 2003, was the first laboratory to provide microarray-based cytogenetic diagnostics with its proprietary SignatureChip(R) and is the leader in providing microarray-based chromosome analysis. Signature's worldwide client base includes clinical geneticists, neurologists, pediatricians, neonatologists, obstetricians, and the research community. Signature is CAP accredited, CLIA certified, and has clinical licenses from California, Rhode Island and Florida. Additional information about Signature Genomic Laboratories is available at


For press inquiries:
Signature Genomic Laboratories
Blake C. Ballif, Ph.D., 509-474-6841

Posted: June 2008