Comprehensive Brain Malformations Panel

Most brain malformations have onset before birth and often lead to severe intellectual disability. A variety of genetic factors can cause brain malformations. This panel covers a broad spectrum of brain malformations. Identification of a genetic cause may help with diagnosis and prognosis and provide information to family members. 

Sequencing is performed on genomic DNA using an Agilent targeted sequence capture method to enrich for the genes on this panel. Direct sequencing of the amplified captured regions was performed using 2X100bp reads on Illumina next-generation sequencing (NGS) systems. A base is considered to have sufficient coverage at 20X, and an exon is considered fully covered if all coding bases plus three nucleotides of flanking sequence on either side are covered at 20X or more. Low coverage regions, if any, are limited to ~1% or less of the nucleotides in the test unless a pathogenic variant explaining the phenotype is discovered. A list of these regions is available upon request. Alignment to the human reference genome (hg19) is performed, and annotated variants are identified in the targeted region. Variants are called at a minimum coverage of 8X and an alternate allele frequency of 20% or higher. Single nucleotide variants (SNVs) meeting internal quality assessment guidelines are confirmed by Sanger sequence analysis for records after results are reported. Indels and SNVs are confirmed by Sanger sequence analysis before reporting at the director's discretion. This assay cannot detect variants in regions of the exome that are not covered, such as deep intronic, promoter, and enhancer regions, areas containing large numbers of tandem repeats, and variants in mitochondrial DNA. Copy number variation (CNV) analysis detects deletions and duplications; in some instances, due to the size of the exons, sequencing complexity, or other factors, not all CNVs may be analyzed and/or may be difficult to detect. This assay is not designed to detect mosaicism; possible cases of mosaicism may be investigated at the discretion of the laboratory director. Primary data analysis is performed using Illumina DRAGEN Bio-IT Platform v.3.4.12. Secondary and tertiary data analysis is performed using PerkinElmer’s internal ODIN v.1.01 software for SNVs and Biodiscovery’s NxClinical v.6.1 or Illumina DRAGEN Bio-IT Platform v.3.4.12 for CNV and the absence of heterozygosity (AOH). Genes and/or exons located in pseudogene regions are not covered in this assay.