DiGeorge syndrome (DGS), or velocardiofacial syndrome, is a relatively frequent genetic disorder (it affects 1 in 4,000 live births), and is usually due to a deleted region of chromosome 22. People with DGS therefore typically lack one copy of each of several genes, the number of which depends on the size of the deletion. But the identification of the minimal deletion that causes DGS has not led to the unambiguous identification of the gene(s) that are critical to the disease. Several laboratories have tried to identify the relevant human genes by producing mice that lack functional copies of the mouse counterparts of the chromosome-22 genes that are typically deleted in people with DGS-with the hope that such mice will mimic features of DGS. These include developmental defects in the thyroid and parathyroid glands, heart defects, cleft palate and other facial malformations.
This strategy has now borne fruit; two genes are now implicated in some if not all aspects of the DGS (Nature Genetics, Vol. 27, No. 3, 02 Mar 2001). Akira Imamoto and colleagues (of the University of Chicago, Illinois) report that mice with mutations in a gene called Crkol develop the cranio-facial, heart and glandular aberrations characteristic of DGS. And, Loydie Jerome and Virginia Papaioannou (of Columbia University, New York) have discovered that mice lacking the Tbx1 gene, which normally controls development, have almost all the features of human DGS. But, as emphasized by Martina Schinke and Seigo Izumo (of Harvard University, Massachusetts) in an accompanying News & Views article, whereas people with DGS retain one intact copy of each gene, mice mimic the features of DGS-in a robust manner-only when lacking both functional copies of either gene. This may reflect a difference between the mouse and human; mice may be less sensitive to disruption of Tbx1 and Crkol than people who lack the counterparts of these genes. Alternatively, it indicates that DGS requires the simultaneous mutation of two genes. One way to explore this possibility would be to cross a mouse lacking a functional copy of Tbx and a mouse lacking a functional copy of Crkol-and to analyze the progeny that lack functional copies of both genes.
A related paper, by Antonio Baldini (of the Baylor College of Medicine, Texas) was published by Nature on 1st March.
Dr. Akira Imamoto
The University of Chicago
Chicago, Illinois - USA
Telephone: +1 (773) 834 1258
Fax: +1 (773) 702 4394
Dr. Virginia Papaioannou
College of Physicians and Surgeons Columbia University
New York, New York - USA
Telephone: +1 (212) 305 4753
Fax: +1 (212) 305 5484
Dr. Seigo Izumo
Harvard Medical School
Boston, Massachusetts, USA
Telephone: +1 (617) 667 4858
Fax: +1 (617) 975 5268
Dr. Antonio Baldini
Department of Pediatrics
Baylor College of Medicine
Houston, Texas, USA
Telephone +1 (713) 798-6519
Fax : +1 713 798 1483
Email Address: firstname.lastname@example.org
(C) Nature Genetics press release.
Message posted by: Trevor M. D'Souza
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