22q11.2 deletion syndrome causes
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ayushi Jain, M.B.B.S[2]
Overview
Most cases are linked to microdeletion of chromosome 22, at the long arm (q) at the 11.2 locus.Failure in embryologic development of the pharyngeal pouches, which is driven by TBX1, leads to absence or hypoplasia of the thymus and parathyroid glands.
Causes
Approximately 90% of DGS cases are due to deletion in chromosome 22, more specifically on the long arm (q) at the 11.2 locus (22q11.2). Most of these mutations arise de novo with no genetic abnormalities noted in the genome of the parents of children with DGS. Researchers have identified over 90 different genes at this locus, some of which they have studied in mouse models. T-box transcription factor 1 (TBX1) is the most studied gene , which correlates with severity of DGS such as defects in the development of the heart, thymus, and parathyroid glands of mouse models.
Failure in embryologic development of the pharyngeal pouches, which is driven by TBX1, leads to absence or hypoplasia of the thymus and parathyroid glands.
Mouse and zebrafish TBX1 knockout models have been studied to understand the embryologic basis of this disease. In mice, for instance, the absence of TBX1 causes severe pharyngeal, cardiac, thymic, and parathyroid defects as well as a behavioral disturbance.[1] Moreover, zebrafish knockouts have demonstrated defects in the thymus and pharyngeal arches as well as malformation of the ears and thymus.[2]
TBX1 also correlates with neuromicrovascular anomalies, which may be responsible for the behavioral and developmental abnormalities seen in DGS.[3][4]
References
- ↑ Zhang Z, Huynh T, Baldini A. Mesodermal expression of Tbx1 is necessary and sufficient for pharyngeal arch and cardiac outflow tract development. Development. 2006 Sep;133(18):3587-95.
- ↑ Guner-Ataman B, González-Rosa JM, Shah HN, Butty VL, Jeffrey S, Abrial M, Boyer LA, Burns CG, Burns CE. Failed Progenitor Specification Underlies the Cardiopharyngeal Phenotypes in a Zebrafish Model of 22q11.2 Deletion Syndrome. Cell Rep. 2018 Jul 31;24(5):1342-1354.e5.
- ↑ Cioffi S, Martucciello S, Fulcoli FG, Bilio M, Ferrentino R, Nusco E, Illingworth E. Tbx1 regulates brain vascularization. Hum. Mol. Genet. 2014 Jan 01;23(1):78-89.
- ↑ Paylor R, Glaser B, Mupo A, Ataliotis P, Spencer C, Sobotka A, Sparks C, Choi CH, Oghalai J, Curran S, Murphy KC, Monks S, Williams N, O'Donovan MC, Owen MJ, Scambler PJ, Lindsay E. Tbx1 haploinsufficiency is linked to behavioral disorders in mice and humans: implications for 22q11 deletion syndrome. Proc. Natl. Acad. Sci. U.S.A. 2006 May 16;103(20):7729-34.