Exome sequencing

Exome sequencing, also known as whole exome sequencing (WES), is a genomic technique for sequencing all of the protein-coding regions of genes in a genome (known as the exome). It consists of two steps: the first step is to select only the subset of DNA that encodes proteins. These regions are known as exons—humans have about 180,000 exons, constituting about 1% of the human genome, or approximately 30 million base pairs. The second step is to sequence the exonic DNA using any high-throughput DNA sequencing technology. The goal of this approach is to identify genetic variants that alter protein sequences, and to do this at a much lower cost than whole-genome sequencing. Since these variants can be responsible for both Mendelian and common polygenic diseases, such as Alzheimer's disease, whole exome sequencing has been applied both in academic research and as a clinical diagnostic. Motivation and comparison to other approaches Exome sequencing is espe

Host genetic predictors of the kynurenine pathway of tryptophan catabolism among treated HIV-infected Ugandans

Yunfei Huang

Objective: Plasma kynurenine/tryptophan ratio, a biomarker of indoleamine 2,3-dioxygenase-1 (IDO) activity, is a strong independent predictor of mortality in HIV-infected Ugandans initiating antiretroviral therapy (ART) and may play a key role in HIV pathogenesis. We performed a genome-wide study to identify potential host genetic determinants of kynurenine/tryptophan ratio in HIV-infected ART-suppressed Ugandans. Design/methods: We performed genome-wide and exome array genotyping and measured plasma kynurenine/tryptophan ratio during the initial 6-12 months of suppressive ART in Ugandans. We evaluated more than 16 million single nucleotide polymorphisms in association with log(10) kynurenine/tryptophan ratio using linear mixed models adjusted for cohort, sex, pregnancy, and ancestry. Results: Among 597 Ugandans, 62% were woman, median age was 35, median baseline CD4(+) cell count was 135 cells/mu l, and median baseline HIV-1 RNA was 5.1 log(10) copies/ml. Several polymorphisms in candidate genes TNF, IFNGR1, and TLR4 were associated with log(10) kynurenine/tryptophan ratio (P < 5.0 x 10(-5)). An intergenic polymorphism between CSPG5 and ELP6 was genome-wide significant, whereas several others exhibited suggestive associations (P < 5.0 x 10(-7)), including genes encoding protein tyrosine phosphatases (PTPRM and PTPRN2) and the vitamin D metabolism gene, CYP24A1. Several of these single nucleotide polymorphisms were associated with markers of inflammation, coagulation, and monocyte activation, but did not replicate in a small US cohort (N = 262; 33% African-American). Conclusion: Our findings highlight a potentially important role of IFN-gamma, TNF-alpha, and Toll-like receptor signaling in determining IDO activity and subsequent mortality risk in HIV-infected ART-suppressed Ugandans. These results also identify potential novel pathways involved in IDO immunoregulation. Further studies are needed to confirm these findings in treated HIV-infected populations. Copyright (C) 2016 Wolters Kluwer Health, Inc. All rights reserved.

Lippincott Williams & Wilkins2016

Genomic Instability Profiles at the Single Cell Level in Mouse Colorectal Cancers of Defined Genotypes

Maxim Norkin, Paloma Ordonez Moran

The genomes of many human CRCs have been sequenced, revealing a large number of genetic alterations. However, the molecular mechanisms underlying the accumulation of these alterations are still being debated. In this study, we examined colorectal tumours that developed in mice with Apclox/lox, LSL-KrasG12D, and Tp53lox/lox targetable alleles. Organoids were derived from single cells and the spectrum of mutations was determined by exome sequencing. The number of single nucleotide substitutions (SNSs) correlated with the age of the tumour, but was unaffected by the number of targeted cancer-driver genes. Thus, tumours that expressed mutant Apc, Kras, and Tp53 alleles had as many SNSs as tumours that expressed only mutant Apc. In contrast, the presence of large-scale (>10 Mb) copy number alterations (CNAs) correlated strongly with Tp53 inactivation. Comparison of the SNSs and CNAs present in organoids derived from the same tumour revealed intratumoural heterogeneity consistent with genomic lesions accumulating at significantly higher rates in tumour cells compared to normal cells. The rate of acquisition of SNSs increased from the early stages of cancer development, whereas large-scale CNAs accumulated later, after Tp53 inactivation. Thus, a significant fraction of the genomic instability present in cancer cells cannot be explained by aging processes occurring in normal cells before oncogenic transformation.

2021

Host genetic predictors of the kynurenine pathway of tryptophan catabolism among treated HIV-infected Ugandans

Yunfei Huang

Lippincott Williams & Wilkins2016

Host genetic predictors of the kynurenine pathway of tryptophan catabolism among treated HIV-infected Ugandans

Whole Exome Sequencing and Extended Thrombophilia Testing in Patients with Venous Thromboembolism

Genomic Instability Profiles at the Single Cell Level in Mouse Colorectal Cancers of Defined Genotypes

Host genetic predictors of the kynurenine pathway of tryptophan catabolism among treated HIV-infected Ugandans

Whole Exome Sequencing and Extended Thrombophilia Testing in Patients with Venous Thromboembolism

Genomic Instability Profiles at the Single Cell Level in Mouse Colorectal Cancers of Defined Genotypes