JAK2 mutations to the fore in hereditary thrombocythemia

JAK2 p.R564 germ line variants associated with hereditary thrombocythemia and hematologic neoplasms

ABSTRACT

The Janus kinase 2 (JAK2) V617F mutation activates the transcription pathway and has been well characterized as a driver of myeloproliferative neoplasms (MPNs). Recently, there has been a heightened interest in understanding germ line predisposition to hematologic malignancies such as MPN, including several reports of familial MPN. Here, we retrospectively analyzed medical records and data from genetic testing to describe 12 patients with germ line variants at amino acid position 564 of JAK2. This includes 3 supportive cases adding to prior literature regarding the germ line JAK2 R564Q association with hereditary thrombocythemia, as well as confirmation of JAK2 R564L as a germ line variant associated with MPN. Importantly, the symptomatic burden for many of the individuals in this series is comparable with that of individuals with the canonical V617F mutation profile. In the JAK2 R564Q cases, we noted a pattern of familial aggregation, presence of congenital thrombocythemia, and co-occurrence with hematologic neoplasms. Identification of germ line predisposition is essential for understanding the pathogenesis of disease, impact on families, and opportunities for preventive care. Continued research is essential to further characterize the penetrance of these conditions and how best to monitor, treat, and optimize management for these families.

Risk assessment and genetic counseling for hematologic malignancies-Practice resource of the National Society of Genetic Counselors

Hematologic malignancies (HMs) are a heterogeneous group of cancers impacting individuals of all ages that have been increasingly recognized in association with various germline predisposition syndromes. Given the myriad of malignancy subtypes, expanding differential diagnoses, and unique sample selection requirements, evaluation for hereditary predisposition to HM presents both challenges as well as exciting opportunities in the ever-evolving field of genetic counseling. This practice resource has been developed as a foundational resource for genetic counseling approaches to hereditary HMs and aims to empower genetic counselors who encounter individuals and families with HMs in their practice.

NGS Evaluation of a Bernese Cohort of Unexplained Erythrocytosis Patients

(1) Background: Clinical and molecular data on patients with unexplained erythrocyto-sis is sparse. We aimed to analyze the clinical and molecular features of patients with congenital erythrocytosis in our tertiary reference center. (2) Methods: In 34 patients with unexplained erythrocytosis, a 13-gene Next-Generation Sequencing erythrocytosis panel developed at our center was conducted. (3) Results: In 6/34 (18%) patients, eight different heterozygous gene variants were found. These patients were, therefore, diagnosed with congenital erythrocytosis. Two patients had two different gene variants each. All variants were characterized as variants of unknown significance as they had not previously been described in the literature. The rest of the patients (28/34, 82%) had no detected gene variants. (4) Conclusions: Our experience shows that the NGS panel can be helpful in determining the reasons for persistent, unexplained erythrocytosis. In our cohort of patients with erythrocytosis, we identified some, thus far unknown, gene variants which may explain the clinical picture. However, further investigations are needed to determine the relationship between the molecular findings and the phenotype.

Characteristics of myeloproliferative neoplasms in patients exposed to ionizing radiation following the Chernobyl nuclear accident

Myeloproliferative neoplasms (MPNs) driver mutations are usually found in JAK2, MPL, and CALR genes; however, 10%-15% of cases are triple negative (TN). A previous study showed lower rate of JAK2 V617F in primary myelofibrosis patients exposed to low doses of ionizing radiation (IR) from Chernobyl accident. To examine distinct driver mutations, we enrolled 281 Ukrainian IR-exposed and unexposed MPN patients. Genomic DNA was obtained from peripheral blood leukocytes. JAK2 V617F, MPL W515, types 1- and 2-like CALR mutations were identified by Sanger Sequencing and real time polymerase chain reaction. Chromosomal alterations were assessed by oligo-SNP microarray platform. Additional genetic variants were identified by whole exome and targeted sequencing. Statistical significance was evaluated by Fisher's exact test and Wilcoxon's rank sum test (R, version 3.4.2). IR-exposed MPN patients exhibited a different genetic profile vs unexposed: lower rate of JAK2 V617F (58.4% vs 75.4%, P = .0077), higher rate of type 1-like CALR mutation (12.2% vs 3.1%, P = .0056), higher rate of TN cases (27.8% vs 16.2%, P = .0366), higher rate of potentially pathogenic sequence variants (mean numbers: 4.8 vs 3.1, P = .0242). Furthermore, we identified several potential drivers specific to IR-exposed TN MPN patients: ATM p.S1691R with copy-neutral loss of heterozygosity at 11q; EZH2 p.D659G at 7q and SUZ12 p.V71 M at 17q with copy number loss. Thus, IR-exposed MPN patients represent a group with distinct genomic characteristics worthy of further study.