Increased Diagnostic Yield of Array Comparative Genomic Hybridization for Autism Spectrum Disorder in One Institution in Taiwan

Background and Objectives: Chromosomal microarray offers superior sensitivity for identification of submicroscopic copy number variants (CNVs) and is recommended for the initial genetic testing of patients with autism spectrum disorder (ASD). This study aims to determine the diagnostic yield of array comparative genomic hybridization (array-CGH) in ASD patients from a cohort of Chinese patients in Taiwan. Materials and Methods: Enrolled in this study were 80 ASD children (49 males and 31 females; 2–16 years old) followed up at Taipei MacKay Memorial Hospital between January 2010 and December 2020. The genomic DNA extracted from blood samples was analyzed by array-CGH via the Affymetrix GeneChip Genome-Wide Human single nucleotide polymorphism (SNP) and NimbleGen International Standards for Cytogenomic Arrays (ISCA) Plus Cytogenetic Arrays. The CNVs were classified into five groups: pathogenic (pathologic variant), likely pathogenic (potential pathologic variant), likely benign (potential normal genomic variant), benign (normal genomic variant), and uncertain clinical significance (variance of uncertain significance), according to the American College of Medical Genetics (ACMG) guidelines. Results: We identified 47 CNVs, 31 of which in 27 patients were clinically significant. The overall diagnostic yield was 33.8%. The most frequently clinically significant CNV was 15q11.2 deletion, which was present in 4 (5.0%) patients. Conclusion: In this study, a satisfactory diagnostic yield of array-CGH was demonstrated in a Taiwanese ASD patient cohort, supporting the clinical usefulness of array-CGH as the first-line testing of ASD in Taiwan.

A Novel 4q32.3 Deletion in a Boy: Additional Signs and the Role of MARCH1

The 4q deletion syndrome is an uncommon condition manifesting with broad clinical expression and phenotypic variability. We report a 5-year-old boy affected by 4q deletion syndrome who showed minor craniofacial features, growth failure, mild developmental delay, severe speech delay, and marked irascibility and aggressivity. Moreover, he showed precocious and crowded primary dentition, digital hyperlaxity, and congenital bilateral adducted thumbs, signs which were previously unreported in the syndrome. The array comparative genomic hybridization analysis revealed a 4q partial terminal deletion of ∼329.6 kb extending from 164.703.186 to 165.032.803 nt, which includes part of MARCH1 (membrane associated ring-CH-type finger 1) gene (OMIM#613331). Same rearrangement was found in his healthy mother. Clinical phenotype of the child and its relationship to the deleted region is presented with a revision of the cases having the same copy number losses from the literature and genomic variant databases.

Scalable Newborn Screening Solutions: Bioinformatics and Next-Generation Sequencing

Expansion of the newborn disorder panel requires the incorporation of new testing modalities. This is especially true for disorders lacking robust biomarkers for detection in primary screening methods and for disorders requiring genotyping or sequencing as a second-tier and/or diagnostic test. In this commentary, we discuss how next-generation sequencing (NGS) methods can be used as a secondary testing method in NBS. Additionally, we elaborate on the importance of genomic variant repositories for the annotation and interpretation of variants. Barriers to the incorporation of NGS and bioinformatics within NBS are discussed, and ideas for a regional bioinformatics model and shared variant repository are presented as potential solutions.

VariantStore: an index for large-scale genomic variant search

Efficiently scaling genomic variant search indexes to thousands of samples is computationally challenging due to the presence of multiple coordinate systems to avoid reference biases. We present VariantStore, a system that indexes genomic variants from multiple samples using a variation graph and enables variant queries across any sample-specific coordinate system. We show the scalability of VariantStore by indexing genomic variants from the TCGA project in 4 h and the 1000 Genomes project in 3 h. Querying for variants in a gene takes between 0.002 and 3 seconds using memory only 10% of the size of the full representation.

Quantifying the impact of data sharing on variant classification

Healthcare is increasingly leveraging genomic data to inform diagnosis, monitoring, and treatment of certain diseases with genetic predisposition. Associating patient data such as family history and de novo status with a genomic variant helps classify that variant as being pathogenic or benign. Indeed, many variants are already classified by experts, but the majority of variants are very rare, have no associated patient data, and are therefore of uncertain significance. This research models the hypothetical sharing of patient data across institutions in order to accelerate the time it takes to classify a variant. Using conservative assumptions described in the paper, we found that the probability of classifying a pathogenic variant which occurs at the rate of 1 in 100,000 people increases from less than 25% to nearly 80% after just one year when sequencing centers share their clinical data. After 5 years, the probability of classifying such a variant is nearly 100%.

Accurate genomic variant detection in single cells with primary template-directed amplification

Improvements in whole genome amplification (WGA) would enable new types of basic and applied biomedical research, including studies of intratissue genetic diversity that require more accurate single-cell genotyping. Here, we present primary template-directed amplification (PTA), an isothermal WGA method that reproducibly captures >95% of the genomes of single cells in a more uniform and accurate manner than existing approaches, resulting in significantly improved variant calling sensitivity and precision. To illustrate the types of studies that are enabled by PTA, we developed direct measurement of environmental mutagenicity (DMEM), a tool for mapping genome-wide interactions of mutagens with single living human cells at base-pair resolution. In addition, we utilized PTA for genome-wide off-target indel and structural variant detection in cells that had undergone CRISPR-mediated genome editing, establishing the feasibility for performing single-cell evaluations of biopsies from edited tissues. The improved precision and accuracy of variant detection with PTA overcomes the current limitations of accurate WGA, which is the major obstacle to studying genetic diversity and evolution at cellular resolution.

First report of X-linked hypohidrotic ectodermal dysplasia with a hemizygous c.1142G > C in the EDA gene: variant of uncertain significance or new pathogenic variant?

Background Hypohidrotic Ectodermal Dysplasia (HED) is a genetic disorder which affects structures of ectodermal origin. X-linked hypohidrotic ectodermal dysplasia (XLHED) is the most common form of disease. XLHED is characterized by hypotrichosis, hypohydrosis and hypodontia. The cardinal features of classic HED become obvious during childhood. Identification of a hemizygous EDA pathogenic variant in an affected male confirms the diagnosis. Case presentation We report on a male newborn with the main clinical characteristics of the X-linked HED including hypotrichosis, hypodontia and hypohidrosis. Gene panel sequencing identified a new hemizygous missense variant of uncertain significance (VUS) c.1142G > C (p.Gly381Ala) in the EDA gene, located on the X chromosome and inherited from the healthy mother. Conclusion Despite the potential functional impact of VUS remains uncharacterized, our goal is to evaluate the clinical potential consequences of missense VUS on EDA gene. Even if the proband’s phenotype is characteristic for classic HED, further reports of patients with same clinical phenotype and the same genomic variant are needed to consider this novel VUS as responsible for the development of HED.