Dataset Information

Long contiguous stretches of homozygosity detected by chromosomal microarrays (CMA) in patients with neurodevelopmental disorders in the South of Brazil.

ABSTRACT: BACKGROUND:Currently, chromosomal microarrays (CMA) are recommended as first-tier test in the investigation of developmental disorders to examine copy number variations. The modern platforms also include probes for single nucleotide polymorphisms (SNPs) that detect homozygous regions in the genome, such as long contiguous stretches of homozygosity (LCSH) also named runs of homozygosity (ROH). LCHS are chromosomal segments resulting from complete or segmental chromosomal homozygosity, which may be indicative of uniparental disomy (UPD), consanguinity, as well as replicative DNA repair events, however also are common findings in normal populations. Knowing common LCSH of a population, which probably represent ancestral haplotypes of low-recombination regions in the genome, facilitates the interpretation of LCSH found in patients, allowing to prioritize those with possible clinical significance. However, population records of ancestral haplotype derived LCSH by SNP arrays are still scarce, particularly for countries such as Brazil where even for the clinic, microarrays that include SNPs are difficult to request due to their high cost. METHODS:In this study, we evaluate the frequencies and implications of LCSH detected by Affymetrix CytoScan® HD or 750?K platforms in 430 patients with neurodevelopmental disorders in southern Brazil. LCSH were analyzed in the context of pathogenic significance and also explored to identify ancestral haplotype derived LCSH. The criteria for considering a region as LCSH was homozygosis ?3 Mbp on an autosome. RESULTS:In 95% of the patients, at least one LCSH was detected, a total of 1478 LCSH in 407 patients. In 2.6%, the findings were suggestive of UPD. For about 8.5% LCSH suggest offspring from first to fifth grade, more likely to have a clinical impact. Considering recurrent LCSH found at a frequency of 5% or more, we outline 11 regions as potentially representing ancestral haplotypes in our population. The region most involved with homozygosity was 16p11.2p11.1 (49%), followed by 1q21.2q21.3 (21%), 11p11.2p11.12 (19%), 3p21.31p21.2 (16%), 15q15 1q33p32.3 (12%), 2q11.1q12.1 (9%), 1p33p32.3 (6%), 20q11.21q11.23 (6%), 10q22.1q23.31 (5%), 6p22.2p22 (5%), and 7q11.22q11.23 (5%). CONCLUSIONS:In this work, we show the importance and usefulness of interpreting LCSH in the results of CMA wich incorporate SNPs.

SUBMITTER: Chaves TF

PROVIDER: S-EPMC6417136 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Long contiguous stretches of homozygosity detected by chromosomal microarrays (CMA) in patients with neurodevelopmental disorders in the South of Brazil.

Chaves Tiago Fernando TF Oliveira Luan Freitas LF Ocampos Maristela M Barbato Ingrid Tremel IT de Luca Gisele Rozone GR Barbato Filho Jorge Humbeto JH de Camargo Pinto Louise Lapagesse LL Bernardi Pricila P Maris Angelica Francesca AF

BMC medical genomics 20190312 1

<h4>Background</h4>Currently, chromosomal microarrays (CMA) are recommended as first-tier test in the investigation of developmental disorders to examine copy number variations. The modern platforms also include probes for single nucleotide polymorphisms (SNPs) that detect homozygous regions in the genome, such as long contiguous stretches of homozygosity (LCSH) also named runs of homozygosity (ROH). LCHS are chromosomal segments resulting from complete or segmental chromosomal homozygosity, whi ...[more]

PMID: 30866944

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Project description:Chromosomal microarray (CMA) is now recommended as first tier for the evaluation in individuals with unexplained neurodevelopmental disorders (ND). However, in developing countries such as Brazil, classical cytogenetic tests are still the most used in clinical practice, as reflected by the scarcity of publications of microarray investigation in larger cohorts. This is a retrospective study which analyses the reading files of CMA and available clinical data from 420 patients from the south of Brazil, mostly children, with neurodevelopmental disorders requested by medical geneticists and neurologists for diagnostic purpose. Previous karyotyping was reported for 138 and includes 17 with abnormal results. The platforms used for CMA were CYTOSCAN 750K (75%) and CYTOSCAN HD (25%). The sex ratio of the patients was 1.625 males :1 female and the mean age was 9.5 years. A total of 96 pathogenic copy number variations (CNVs), 58 deletions and 38 duplications, were found in 18% of the patients and in all chromosomes, except chromosome 11. For 12% of the patients only variants of uncertain clinical significance were found. No clinically relevant CNV was found in 70%. The main referrals for chromosomal microarrays (CMA) were developmental delay (DD), intellectual disability (ID), facial dysmorphism and autism spectrum disorder (ASD). DD/ID were present in 80%, facial dysmorphism in 52% and ASD in 32%. Some phenotypes in this population could be predictive of a higher probability to carry a pathogenic CNV, as follows: dysmorphic facial features (p-value?=?<?0.0001, OR?=?0.32), obesity (p-value?=?0.006, OR?=?0.20), short stature (p-value?=?0.032, OR?=?0.44), genitourinary anomalies (p-value?=?0.032, OR?=?0.63) and ASD (p-value?=?0.039, OR?=?1.94). The diagnostic rate for CMA in this study was 18%. We present the largest report of CMA data in a cohort with ND in Brazil. We characterize the rare CNVs found together with the main phenotypes presented by each patient, list phenotypes which could predict a higher diagnostic probability by CMA in patients with a neurodevelopmental disorder and show how CMA and classical karyotyping results are complementary.

Dataset Information

Long contiguous stretches of homozygosity detected by chromosomal microarrays (CMA) in patients with neurodevelopmental disorders in the South of Brazil.

Publications

Long contiguous stretches of homozygosity detected by chromosomal microarrays (CMA) in patients with neurodevelopmental disorders in the South of Brazil.

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