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Genetic modifiers of the physical malformations in velo-cardio-facial syndrome/DiGeorge syndrome.

ABSTRACT: Velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS), the most common micro-deletion disorder in humans, is characterized by craniofacial, parathyroid, and thymic defects as well as cardiac outflow tract malformations. Most patients have a similar hemizygous 3 million base pair deletion on 22q11.2. Studies in mouse have shown that Tbx1, a T-box containing transcription factor present on the deleted region, is likely responsible for the etiology of the syndrome. Furthermore, mutations in TBX1 have been found in rare non-deleted patients. Despite having the same sized deletion, most VCFS/DGS patients exhibit significant clinical variability. Stochastic, environmental and genetic factors likely modify the phenotype of patients with the disorder. Here, we review mouse genetics studies, which may help identify possible genetic modifiers for the physical malformations in VCFS/DGS.

SUBMITTER: Aggarwal VS

PROVIDER: S-EPMC2818567 | biostudies-literature | 2008 00

REPOSITORIES: biostudies-literature

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Genetic modifiers of the physical malformations in velo-cardio-facial syndrome/DiGeorge syndrome.

Aggarwal Vimla S VS Morrow Bernice E BE

Developmental disabilities research reviews 20080101 1

Velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS), the most common micro-deletion disorder in humans, is characterized by craniofacial, parathyroid, and thymic defects as well as cardiac outflow tract malformations. Most patients have a similar hemizygous 3 million base pair deletion on 22q11.2. Studies in mouse have shown that Tbx1, a T-box containing transcription factor present on the deleted region, is likely responsible for the etiology of the syndrome. Furthermore, mutations in TBX1 ...[more]

PMID: 18636633

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Project description:Velo-cardio-facial syndrome (VCFS, MIM#192430, 22q11.2 Deletion Syndrome) is a genetic disorder caused by a deletion of about 40 genes at the q11.2 band of one copy of chromosome 22. Individuals with VCFS present with deficits in cognition and social functioning, high risk of psychiatric disorders, volumetric reductions in gray and white matter (WM) and some alterations of the WM microstructure. The goal of the current study was to characterize the WM microstructural differences in individuals with VCFS and unaffected siblings, and the correlation of WM microstructure with neuropsychological performance. We hypothesized that individuals with VCFS would have decreased indices of WM microstructure (fractional anisotropy (FA), axial diffusivity (AD) and radial diffusivity (RD)), particularly in WM tracts to the frontal lobe, and that these measures would be correlated with cognitive functioning.Thirty-three individuals with VCFS (21 female) and 16 unaffected siblings (8 female) participated in DTI scanning and neuropsychological testing. We performed an atlas-based analysis, extracted FA, AD, and RD measures for 54 WM tracts (27 in each hemisphere) for each participant, and used MANOVAs to compare individuals with VCFS to siblings. For WM tracts that were statistically significantly different between VCFS and siblings (pFDR?<0.05), we assessed the correlations between DTI and neuropsychological measures.In VCFS individuals as compared to unaffected siblings, we found decreased FA in the uncinate fasciculus, and decreased AD in multiple WM tracts (bilateral superior and posterior corona radiata, dorsal cingulum, inferior fronto-occipital fasciculus, superior longitudinal fasciculus, superior cerebellar peduncle, posterior thalamic radiation, and left anterior corona radiata, retrolenticular part of the internal capsule, external capsule, sagittal stratum). We also found significant correlations of AD with measures of executive function, IQ, working memory, and/or social cognition.Our results suggest that individuals with VCFS display abnormal WM connectivity in a widespread cerebro-anatomical network, involving tracts from/to all cerebral lobes and the cerebellum. Future studies could focus on the WM developmental trajectory in VCFS, the association of WM alterations with psychiatric disorders, and the effects of candidate 22q11.2 genes on WM anomalies.

Project description:Velo-cardio-facial syndrome (VCFS) is caused by a microdeletion of approximately 40 genes from one copy of chromosome 22. Expression of the syndrome is a variable combination of over 190 phenotypic characteristics. As of yet, little is known about how these phenotypes correlate with one another or whether there are predictable patterns of expression. Two of the most common phenotypic categories, congenital heart disease and cleft palate, have been proposed to have a common genetic relationship to the deleted T-box 1 gene (TBX1). The purpose of this study is to determine if congenital heart disease and cleft palate are correlated in a large cohort of human subjects with VCFS.This study is a retrospective chart review including 316 Caucasian non-Hispanic subjects with FISH or CGH microarray confirmed chromosome 22q11.2 deletions. All subjects were evaluated by the interdisciplinary team at the Velo-Cardio-Facial Syndrome International Center at Upstate Medical University, Syracuse, NY. Each combination of congenital heart disease, cleft palates, and retrognathia was analyzed by Chi square or Fisher exact test.For all categories of congenital heart disease and cleft palate or retrognathia no significant associations were found, with the exception of submucous cleft palate and retrognathia (nominal p=0.0325) and occult submucous cleft palate and retrognathia (nominal p=0.000013).Congenital heart disease and cleft palate do not appear to be correlated in human subjects with VCFS despite earlier suggestions from animal models. Possible explanations include modification of the effect of TBX1 by genes outside of the 22q11.2 region that may further influence the formation of the palate or heart, or the presence of epigenetic factors that may effect genes within the deleted region, modifying genes elsewhere, or polymorphisms on the normal copy of chromosome 22. Lastly, it is possible that TBX1 plays a role in palate formation in some species, but not in humans. In VCFS, retrognathia is caused by an obtuse angulation of the skull base. It is unknown if the correlation between retrognathia and cleft palate in VCFS indicates a developmental sequence related to skull morphology, or direct gene effects of both anomalies. Much work remains to be done to fully understand the complex relationships between phenotypic characteristics in VCFS.

Dataset Information

Genetic modifiers of the physical malformations in velo-cardio-facial syndrome/DiGeorge syndrome.

Publications

Genetic modifiers of the physical malformations in velo-cardio-facial syndrome/DiGeorge syndrome.

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