This article presents some of the earliest evidence of visuospatial and numerical cognitive deficits in children with the chromosome 22q11.2 deletion syndrome; a common but ill-understood genetic disorder resulting in medical complications, cognitive impairment, and brain morphologic changes. Relative to a group of typically developing controls, deleted children performed more poorly on tests of visual attentional orienting, visual enumeration and relative numerical magnitude judgment. Results showed that performance deficits in children with the deletion could not be explained by a global deficit in psychomotor speed. Instead, our findings are supportive of the hypothesis that visuospatial and numerical deficits in children with the chromosome 22q11.2 deletion are due, at least in part, to posterior parietal dysfunction.

Velo-cardio-facial syndrome/DiGeorge syndrome, also known as 22q11.2 deletion syndrome (22q11DS) is the most common microdeletion syndrome, with an estimated incidence of 1/2,000 – 1/4,000 live births. Approximately 9–11% of patients with this disorder have an overt cleft palate (CP), but the genetic factors responsible for CP in the 22q11DS subset are unknown. The TBX1 gene, a member of the T-box transcription factor gene family, lies within the 22q11.2 region that is hemizygous in patients with 22q11DS. Inactivation of one allele of Tbx1 in the mouse does not result in CP, but inactivation of both alleles does. Based on these data, we hypothesized that DNA variants in the remaining allele of TBX1 may confer risk to CP in patients with 22q11DS. To test the hypothesis, we evaluated TBX1 exon sequencing (n = 360) and genotyping data (n = 737) with respect to presence (n = 54) or absence (n = 683) of CP in patients with 22q11DS. Two upstream SNPs (rs4819835 and rs5748410) showed individual evidence for association but they were not significant after correction for multiple testing. Associations were not identified between DNA variants and haplotypes in 22q11DS patients with CP. Overall, this study indicates that common DNA variants in TBX1 may be nominally causative for CP in patients with 22q11DS. This raises the possibility that genes elsewhere on the remaining allele of 22q11.2 or in the genome could be relevant.

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