oa Identifying Novel Mutations In Familial Myeloproliferative Neoplasms Patients In The State Of Qatar Via Targeted Exome Sequencing Approach

Background: Polycythemia Vera (PV), Essential Thrombocytosis (ET) & Primary Myelofibrosis (PMF) are Philadelphia negative Myeloproliferative Neoplasms (MPNs) characterized by overproduction of one or more myeloid cell lineages. MPNs are associated with the presence JAK2 V617F mutation in 95% of PV & 50% of ET & PMF patients. Several molecular methods such as RQ-PCR, HRM & Sequencing are currently used to detect common mutations. However, there are still significant numbers of MPNs are negative to the most common genetic anomalies. The advent of Next Generation Sequencing (NGS) gives the opportunity to study relevant mutations in several genes. Aim: Utilizing NGS to identify potential genetic anomalies causing familial MPNs patients in Qatar. Methods: 6 MPNs patients from consanguineous families & 5 healthy individuals were consented into the study gDNA was extracted & used for multiplex amplification of amplicons targeting cancer associated mutations in 28 key genes using the Ion AmpliSeq Kit. NGS was performed via the Ion Torrent using the 318 chip & data was analyzed with the Torrent Suite. The confirmation of NGS data was done by RQ-PCR or Sequencing. Results: NGS identified novel deleterious mutations in MPNs patients. Out of 6 familial cases, 5 patients (P1- P5) were ET & 1 patient (P6) was PV. P1 had JAK2 V617F, ASXL1 T600P, CBFB G180S, THPO S184R & ITGA2 R76Q, P2 had JAK2 V617F, MPL A554G & ATM F582L, the other three Patients (P3, P4 & P5) had CLAR K385fs*47 & one PV patient (P6) had TYK2 E1163G, ASXL1 P808H, PDGFRB P4L TERT G300fs. In patients & healthy individuals, mutations/SNVs such as MPL P106L, K553N, SH2B3 L476F, ATM F1036F KIT N564S & TET2 T730R were also found Discussion & conclusion: In this study, several deleterious somatic/germ-line mutations/SNVs were identified using Targeted Exome Sequencing approach. A complex combination of mutations occurred in ET patients & coexistence of several oncogenic events occurred in PV patient. This finding may also suggest that the MPNs phenotype may depend on presence of other mutations. It is worth to mention that the presence of ATM variant in P2 is associated with increased risk of CLL. Somatic CALR type-2 mutation was identified in 3 ET (nonmutated JAK2 or MPL) patients. This mutation is 5-bp TTGTC insertion in exon 9 that generates a mutant protein with a novel C-terminal (p.K385fs*47). In patients & healthy individuals, a heterozygous germ-line mutation in exon 3 of the MPL gene (MPL P106L) has been observed and previously described as a rare autosomal-dominant disorder. However, this mutation is considered to be frequent in Arabic populations also several unreported variants of uncertain significance were identified. Our finding suggested that familial MPNs patients in Qatari tribes have several potential disease- associated variants/mutations which represent a unique interest for the scientific community worldwide and present an unprecedented opportunity for local and international collaborations to carry out WES in society with its unique coherence and genetic pool (founder effect), this would offer invaluable resources to unravel the genetic etiology and pathogenesis, delineate the mechanisms behind MPNs phenotypic diversity.