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Genomic regions associated with microdeletion/microduplication syndromes exhibit extreme diversity of structural variation.

ABSTRACT: Segmental duplications (SDs) are a class of long, repetitive DNA elements whose paralogs share a high level of sequence similarity with each other. SDs mediate chromosomal rearrangements that lead to structural variation in the general population as well as genomic disorders associated with multiple congenital anomalies, including the 7q11.23 (Williams-Beuren Syndrome, WBS), 15q13.3, and 16p12.2 microdeletion syndromes. Population-level characterization of SDs has generally been lacking because most techniques used for analyzing these complex regions are both labor and cost intensive. In this study, we have used a high-throughput technique to genotype complex structural variation with a single molecule, long-range optical mapping approach. We characterized SDs and identified novel structural variants (SVs) at 7q11.23, 15q13.3, and 16p12.2 using optical mapping data from 154 phenotypically normal individuals from 26 populations comprising five super-populations. We detected several novel SVs for each locus, some of which had significantly different prevalence between populations. Additionally, we localized the microdeletion breakpoints to specific paralogous duplicons located within complex SDs in two patients with WBS, one patient with 15q13.3, and one patient with 16p12.2 microdeletion syndromes. The population-level data presented here highlights the extreme diversity of large and complex SVs within SD-containing regions. The approach we outline will greatly facilitate the investigation of the role of inter-SD structural variation as a driver of chromosomal rearrangements and genomic disorders.

SUBMITTER: Mostovoy Y

PROVIDER: S-EPMC8045732 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background: Chromosomal 16p11.2 deletions and duplications are genomic disorders which are characterized by neurobehavioral abnormalities, obesity, congenital abnormalities and so on. However, the prenatal phenotypes of 16p11.2 copy number variations (CNVs) are still not well described till now. This study aimed to provide an elaborate summary of intrauterine phenotypic features for such genomic disorders. Methods: Twenty prenatal amniotic fluid samples diagnosed with 16p11.2 microdeletions/microduplications were obtained from pregnant women who opted for invasive prenatal testing. Karyotypic analysis and chromosomal microarray analysis (CMA) were performed in parallel. The pregnancy outcomes and health conditions after birth for all cases were followed up. Meanwhile, we made a pooled analysis on the prenatal phenotypes for the published cases carrying 16p11.2 CNVs. Results: 20 fetuses (20/20884, 0.10%) with 16p11.2 CNVs were identified: five 16p11.2 BP2-BP3 deletion, ten 16p11.2 BP4-BP5 deletion and five 16p11.2 BP4-BP5 duplication. Abnormal ultrasound findings were recorded in ten participants with 16p11.2 deletions.Various degrees of intrauterine phenotypic features, ranging from normal to abnormal, were observed. No ultrasound abnormalities were observed for all 16p11.2 duplication cases during the pregnancy period. For 16p11.2 deletions, eleven cases terminated their pregnancies. For 16p11.2 duplications, four cases gave birth to healthy neonates except one was lost to follow up. Conclusions: Diverse prenatal phenotypes were presented in 16p11.2 CNVs, ranging from normal to abnormal. For 16p11.2 BP4-BP5 deletion, the most common structural and non-structural abnormalities were the abnormality of the vertebral column or rib and thickened nuchal translucency, respectively. 16p11.2 BP2-BP3 deletion might be closely associated with fetal growth restriction and single umbilical artery. No representative ultrasound findings for 16p11.2 duplication were observed till now. Considering the variable expressivity and incomplete penetrance of 16p11.2 CNVs, long term follow up after birth should be carried out for these cases. We identified 20 fetuses carrying the 16p11.2 microdeletions and microduplications using chromosomal microarray analysis. And diverse prenatal phenotypes and the critical genes involved in the deleted/duplicated regions were described in this study.

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Genomic regions associated with microdeletion/microduplication syndromes exhibit extreme diversity of structural variation.

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