Hemostatic phenotypes and genetic disorders

Abstract

This review is focused on genetic regulators of bleeding and thrombosis with a focus on next-generation sequencing (NGS) technologies for diagnosis and research of patients with inherited disorders. The molecular diagnosis of hemostatic phenotypes relies on the detection of genetic variants in the 99 curated disease-causing genes implicated for bleeding, platelet, and thrombotic disorders through the use of multigene panel tests. In this review, we will provide an overview of the advantages and disadvantages of using such multigene panel tests for diagnostics. During the past decade, NGS technologies have also been used for the gene discovery of 32 novel genes involved in inherited hemostatic phenotypes. We will provide a brief overview of these genes and discuss what information (eg, linkage, consanguinity, multiple index cases with similar phenotypes, mouse models, and more) was used to support the gene discovery process. Next, we provide examples on how RNA sequencing is useful to explore disease mechanisms of novel and often unexpected genes. This review will summarize the important findings concerning NGS technologies for diagnostics and gene discovery that were presented at the ISTH 2021 conference. Finally, future perspectives in our field mainly deal with finding the needle in the haystack for some still unexplained patients and the need for exploring the noncoding gene space and rapid disease validation models.

FIGURE 1

Overview of TIER1 genes and their respective roles in platelet formation and function, and the coagulation cascade. Top: identified TIER1 genes with a role in platelet formation and function, ordered by the molecular pathway in which they function. Bottom: TIER1 genes related to the coagulation cascade, coagulation inhibition, production of coagulation factors, and fibrinolysis. vWF, von Willebrand factor. Figure created with Biorender.com

FIGURE 2

Standard workflow for NGS approaches in the diagnosis of inherited bleeding and thrombotic disorders. The standard diagnostics workflow using NGS approaches consists of several steps. After informed consent is obtained through clinical consultations, patient blood samples are submitted to multigene panel testing. After data QC, processing, and variant prioritization, candidate variants are selected in multidisciplinary meetings. PVs and LPVs in TIER1 genes are reported to the clinician, while VUSs in TIER1 genes can be further investigated using functional assays or cosegregation analysis for variant reclassification. If a virtual multigene panel was used based on WES or WGS data, these data can further be used for gene discovery using RNA sequencing, functional assays, and family recall studies. LPV, likely pathogenic variant; PV, pathogenic variant; QC, quality control; VUS, variant of unknown significance; WES, whole‐exome sequencing; WGS, whole‐genome sequencing. Figure created with Biorender.com