Chromosome 7q11.23 deletions and duplications cause different symptoms.
Segment 7q11.23 contains 25-27 genes. Both deletions and duplications of this segment are known to cause different disorders. Deletions of 7q11.23 cause (a well-recognized) Williams syndrome; duplication of 7q11.23 cause a wide range of clinical manifestations that are hard to recognize before cytogenetic examination. Both del 7q11.23 and dup 7q11.23 cause decreased intellectual ability, developmental coordination disorder and hypotonia. Both conditions are predisposed to autism, which may be found in ~1/5 of carriers. However, patients with del 7q11.23 are socially disinhibited, while patients with dup 7q11.23 are shy and socially anxious. Del 7q11.23 leads to narrowing of the ascending aorta, while dup 7q11.23 causes aortic dilation. Aortic abnormalities are caused by deletions/duplications of the ELN gene. However, it is not clear which gene(s) cause functional disturbances of the brain. Typical cases of Williams syndrome are caused by a ~1.55 Mb deletion in 7q11.23. Sometimes there are atypical cases when only a part of the “classic” 1.55 Mb segment is deleted. Comparison of these cases with typical cases allows the link of present (or absent) genes to some manifestations of the syndrome. Such analysis showed that the BAZ1B gene may be critical for facial features of Williams syndrome patients. The GTF2I genes (including GTF2IRD2) are likely to be linked to the social behavior of these patients. Restoration of GTF2I levels via drug or gene therapy may improve this condition in Williams syndrome patients (at least it was shown using mice models). From the standpoint of evolution, genes GFT2I and GTF2IRD2 have been proposed as key elements in human (and dog) domestication, and their disturbance may cause specific behavioral characteristics.
Osborne L.R. and Mervis C.B. “7q11.23 deletion and duplication”. “Current Opinion in Genetics & Development“ 2021, v. 68, 41-48.
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