Challenges imposed by minor reference alleles on the identification and reporting of clinical variants from exome data

• Published in: BMC genomics Vol. 19; no. 1; p. 46
• Main Authors: Koko, Mahmoud, Abdallah, Mohammed O E, Amin, Mutaz, Ibrahim, Muntaser
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 15.01.2018; BioMed Central; BMC
• Subjects: Alleles; Exome sequencing; Gene Frequency; Genetic Variation; Genome, Human; Human exome; Humans; Minor reference alleles; Next generation sequencing; Reference Standards; Variant calling; Venous Thrombosis - genetics; Whole Exome Sequencing - standards; Human exome; Minor reference alleles; Next generation sequencing; Variant calling
• ISSN: 1471-2164; 1471-2164
• DOI: 10.1186/s12864-018-4433-3

The conventional variant calling of pathogenic alleles in exome and genome sequencing requires the presence of the non-pathogenic alleles as genome references. This hinders the correct identification of variants with minor and/or pathogenic reference alleles warranting additional approaches for variant calling. More than 26,000 Exome Aggregation Consortium (ExAC) variants have a minor reference allele including variants with known ClinVar disease alleles. For instance, in a number of variants related to clotting disorders, the phenotype-associated allele is a human genome reference allele (rs6025, rs6003, rs1799983, and rs2227564 using the assembly hg19). We highlighted how the current variant calling standards miss homozygous reference disease variants in these sites and provided a bioinformatic panel that can be used to screen these variants using commonly available variant callers. We present exome sequencing results from an individual with venous thrombosis to emphasize how pathogenic alleles in clinically relevant variants escape variant calling while non-pathogenic alleles are detected. This article highlights the importance of specialized variant calling strategies in clinical variants with minor reference alleles especially in the context of personal genomes and exomes. We provide here a simple strategy to screen potential disease-causing variants when present in homozygous reference state.