Israel Medical Association Journal

Background: Gaucher disease is the most prevalent inherited disorder among Ashkenazi Jews (carrier frequency of about 6%) and six mutations account for about 96% of their mutant alleles. Two mutations, N370S and R496H, have been reported only in mildly affected or asymptomatic patients, Due to the rarity of R496H, it was recommended that it be excluded from screening programs. 

Objectives: To verify the frequency and trace the origin of Gaucher mutations in screened individuals whose Ashkenazi ethnicity was confirmed by the birthplace of their grandparents.

Methods: We conducted a retrospective analysis of the screened results for the period 2006–2011. Mutations were identified by restriction analysis, Tag-It^TM detection system, Pronto® diagnostic kit and Nanogen technology (NanoChip® 400).

Results: The heterozygote frequency of eight mutations was estimated in a cohort of 16,910 alleles. Two mutations, N370S and R496H, were the most frequent in our population. However, while the occurrence of N370S carriers was similar to other reports (1:19.4), that of R496H carriers was considerably elevated (1:207). Examination of the screened individuals' ethnicity showed a significant difference in the distribution pattern of the country of origin between the carriers of these two mutations.

Conclusions: The origin pattern differences between the two groups of heterozygotes might reflect a separate geographic region of introduction for various mutations. As a result, secondary subgroups could be formed within the Ashkenazi population. This might clarify the dissimilarities in the occurrence of R496H mutation reported by various centers. 

Background: Janus kinase-2 (JAK2) is mutated in a high proportion of patients with polycythemia vera and in a smaller number with essential thrombocythemia and primary myelofibrosis. Mutated JAK2 is an important diagnostic marker for myeloproliferative neoplasm (MPN) and may also play a major role in the pathogenesis of MPN.

Objectives: To evaluate the prevalence of mutated JAK2 (JAK2-V617F) among patients with major intraabdominal vein thrombosis who had normal blood counts at diagnosis of the initial event.

Methods: The medical records of patients who presented with a major intraabdominal venous thrombosis and normal peripheral blood counts were obtained. JAK2-V617F mutation status was determined by real-time polymerase chain reaction.

Results: Twenty-two patients were available for this analysis and 9 (41%) were found to have JAK2-V617F. Patients with positive JAK2-V617F were younger and had more frequent clinical splenomegaly than those with wild-type JAK2.

Conclusions: A high proportion of patients presenting with “idiopathic” major intraabdominal vein thrombosis and normal blood counts carry JAK2-V617F. We recommend searching for the mutation in this clinical setting to detect patients with occult MPN.

Background: Familial Mediterranean fever (FMF) is a recessively inherited disease with a variety of clinical presentations. The disease is associated with mutations in the FMF gene (MEFV), which encodes for the pyrin protein. The role of the E148Q pyrin mutation in the FMF phenotype remains inconclusive, and some authors even view it as a disease-insignificant polymorphism. The calculated change, imposed by this mutation on pyrin structure, may help to understand the role of this mutation

Objectives: To calculate the relative electrochemical effect of the E148Q mutation on the structure of pyrin protein.

Methods: The electronic properties of the wild-type pyrin molecule and its common mutated forms were computed for the full-length molecule and its segments, encoded by exons 2 and 10, using the HyperChem 7.5 program with one of the molecular mechanical methods (MM+). The change in the structure of the molecule, expressed as a change in energy gain, conferred by the mutations was determined.

Results: The E148Q mutation caused deviation from the wild-type pyrin segment encoded by exon 2 by 1.15% and from the whole pyrin molecule by 0.75%, comparable to the R202Q mutation and less than the M694V mutation which caused a deviation from the wild-type structure of the whole pyrin molecule by 1.5%.

Conclusions: A quantum-chemistry based model suggests that the structural effect of the E148Q mutation is indeed low, but not zero. 
 

Background: Since the identification of the MEFV gene 198 mutations have been identified, not all of which are pathologic. The screening methods used in Israel to test patients suspected of having FMF include a kit that tests for the five main mutations (M694V, V726A, M680Ic/g, M694I, E148Q), and the sequencing of MEFV exon 10 in combination with restriction analysis for detecting additional mutations.

Objectives: To determine the contribution of testing for five additional mutations – A744S, K695R, M680Ic/t, R761H and P369S – to the molecular diagnosis of patients clinically suspected of having FMF.

Methods: A total of 1637 patients were tested for FMF mutations by sequencing exon 10 and performing restriction analysis for mutations E148Q and P369S.

Results: Nearly half the patients (812, 49.6%) did not have any detectable mutations, 581 (35.5%) had one mutation, 241 (14.7%) had two mutations, of whom 122 were homozygous and 119 compound heterozygous, and 3 had three mutations. Testing for the additional five mutations enabled us to identify 46 patients who would have been missed by the molecular diagnosis kit and 22 patients who would have been found to have only one mutation. Altogether, 4.3% of the patients would not have been diagnosed correctly by using only the kit that tests for the five main mutations.

Conclusions: This study suggests that testing for the additional five mutations as well as the five main mutations in patients with a clinical presentation of FMF adds significantly to the molecular diagnosis of FMF in the Israeli population.
 

Background: Patients with multiple (< 100) colorectal adenomatous polyps are at increased risk for colorectal cancer. Genetic evaluation of those patients who test negative for APC gene mutation is both a clinical and economic burden but is critical for counseling and surveillance. In Israel, this is confounded by the fact that national health insurance does not fully cover genetic evaluation of APC gene exon 16.

Objectives: To perform a comprehensive genetic evaluation of APC gene mutation-negative polyposis patients with the aim of developing a future evaluation protocol.

Methods: Genetic analyses were performed in 29 APC gene mutation-negative Jewish individuals with 5 to ≥ 40 colonic adenomas who did not fulfill Amsterdam (clinical) criteria for Lynch syndrome. Analyses included completion of APC gene exon 16 sequencing, analysis for APC gene copy number variations (deletions or duplications), MUTYH gene sequencing, and microsatellite instability in CRC[1] patients fulfilling “Bethesda” (laboratory investigation) criteria for Lynch syndrome.

Results: Completion of APC gene exon 16 sequencing revealed one patient with the E1317Q polymorphism. All were normal by APC multiplex ligation-dependent probe amplification analysis. Pathogenic MUTYH mutations were found in three patients, all of North African origin; two additional patients had variants of unknown significance. One of six patients with Bethesda-positive criteria was MSI²-High with immunohistology consistent with MLH1 mutation.

Conclusions: Based on this small but well-characterized cohort with multiple colorectal adenomas, Lynch syndrome needs to be excluded if there are compatible criteria; otherwise MUTYH sequencing is probably the first step in evaluating APC-negative patients, especially for Jews of North African descent. Completing APC exon 16 sequencing and copy number variations analysis should probably be the last evaluations.

Background: Germline mutations in BRCA1 and BRCA2 genes account for only 20–40% of familial breast cancer cases. The CHEK2 gene encodes a checkpoint kinase, involved in response to DNA damage, and hence is a candidate gene for breast cancer susceptibility. Indeed, the CHEK2*1100delC truncating mutation was reported in a subset of mostly North European breast cancer families. The rate of the CHEK2*1100delC variant in the Ashkenazi* Jewish population was reported to be 0.3%.

Objectives: To evaluate whether CHEK2 germline mutations contribute to a breast cancer predisposition in Ashkenazi-Jewish high risk families.

Methods: High risk Ashkenazi Jewish women, none of whom was a carrier of the predominant Jewish mutations in BRCA1/BRCA2, were genotyped for germline mutations in the CHEK2 gene by exon-specific polymerase chain reaction followed by denaturing gradient gel electrophoresis and sequencing of abnormally migrating fragments.

Results: Overall, 172 high risk women were genotyped: 75 (43.6%) with breast cancer (average age at diagnosis 49.6 ± 9.6 years, mean ± SD) and 97 asymptomatic individuals (age at counseling 48.3 ± 8.2 years). No truncating mutations were noted and four previously described missense mutations were detected (R3W 1.2%, I157T 1.2%, R180C 0.6% and S428F 5%), one silent polymorphism (E84E 20.5%) and one novel missense mutation (Y424H 1.2%). Segregation analysis of the I157T and S428F mutations (shown to affect protein function) with the cancer phenotype showed concordance for the CHK2*I157T mutation, as did two of three families with the CHK2*S428F mutation.

Conclusions: CHEK2 missense mutations may contribute to breast cancer susceptibility in Ashkenazi Jews.