Phenotypic heterogeneity in 22q11.2 deletion syndrome: Copy Number Variants as genetic modifiers for congenital heart disease in a Brazilian cohort.

The clinical heterogeneity in 22q11.2 deletion syndrome (22q11.2DS) underlies complex genetic mechanisms including variants in other regions of the genome, known as genetic modifiers. Congenital heart disease (CHD) is one of the most relevant phenotypes in the syndrome and copy number variants (CNVs) outside the 22q11.2 region could play a role in its variable expressivity. Since those described loci account for a small proportion of the variability, the CNV analysis in new cohorts from different ancestry-based populations constitutes a valuable resource to identify a wider range of modifiers. We performed SNP-array in 117 Brazilian patients with 22q11.2DS, with and without CHD, and leveraged genome-wide CNV analysis. After quality control, we selected 50 CNVs in 38 patients for downstream analysis. CNVs' genetic content and implicated biological pathways were compared between patients with and without CHD. CNV-affected genes in patients with CHD were enriched for several functional terms related to ubiquitination, transcription factor binding sites and miRNA targets, highlighting the complexity of the phenotype's expressivity. Cardiac-related genes were identified in both groups of patients suggesting that increasing risk and protective mechanisms could be involved. These genes and enriched pathways could indicate new modifiers to the cardiac phenotype in 22q11.2DS patients.

Phenotype comparison among individuals with developmental delay/intellectual disability with or without genomic imbalances.

BACKGROUND: The chromosomal microarray analysis (CMA) is recommended as a first-tier test for individuals with developmental delay (DD)/intellectual disability (ID) and/or multiple congenital anomalies. However, owing to high costs, this technique is not widely performed for diagnostic purposes in several countries. The aim of this study was to identify clinical features that could favour the hypothesis of genomic imbalances (GIs) in individuals with DD/ID. METHODS: The sample consisted of 63 individuals, and all of them underwent a detailed evaluation by a clinical geneticist and were investigated by the CMA. They were divided into two groups. Group A composed of 20 individuals with pathogenic copy number variants (CNVs); and group B composed of 43 individuals with normal CMA results or variants of uncertain clinical significance (VUS). RESULTS: Pathogenic GIs were found in 20 cases (32%), including 11 individuals with an abnormal karyotype, VUS was found in five individuals (8%) and the results were normal in 38 individuals (60%). Major anomalies were found in 15/20 (75%) individuals in group A against 35/43 (81%) in group B. Dysmorphisms (≥5) were found in 17/20 (85%) in group A and 41/43 (95%) in group B. The most frequent major anomalies detected in group A were congenital heart disease, epilepsy and renal malformation; and in group B, they were malformations of central nervous system, congenital heart disease, microcephaly, epilepsy and hearing impairment. There was no significant statistical difference among the frequencies in groups A and B. CONCLUSIONS: Evidences point that every individual with DD/ID, with no specific clinical suspicion, should have screening for GIs as a first-tier test, regardless of the presence or absence of additional major anomalies or dysmorphisms. Future studies with a similar design would be helpful, especially in countries where the access to new technologies is still limited.