Israel Medical Association Journal

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: 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: The etiology of chest pain with normal epicardial coronary arteries (cardiac syndrome X) seems to be related to endothelial cell dysfunction. Multiple factors are implicated in the pathophysiology, including evelated levels of homocysteine in the blood. Mutations in the MTHFR gene are associated with evelated levels of homocysteine.

Objectives: To test whether abnormal homocysteine metabolism is associated with syndrome X.

Methods: Forty-two women with chest pain, positive stress test and normal coronary arteries (syndrome X) and 100 asymptomatic women (controls) were studied for the C677T mutation. Vitamin B12, folic acid, and plasma levels of homocysteine were also measured. Endothelial cell function was studied in 10 patients with syndrome X and homozygosity for C677T mutation, and in 10 matched healthy controls. Folic acid (5 mg daily) was prescribed to syndrome X patients after initial measurements of ECF[1]. Following 13 weeks of treatment, ECF and blood tests were repeated and compared to baseline measurements.

Results: Homozygosity for C677T mutation was doubled in syndrome X vs. control (33%, 14/42 vs. 16%, 16/100, P < 0.02), and homocysteine levels were increased (9.16 ± 2.4 vs. 8.06 ± 2.6 μmol/L, P = 0.02). In the 10 homozygous patients, homocysteine levels decreased significantly after treatment with 5 mg/day folic acid (10 ± 3.3 vs. 5.4 ± 1.1 µmol/L, P = 0.004). Abnormal baseline ECF improved after treatment with folic acid: flow-mediated dilatation was greater (11.3 ± 7.9% vs. 0.7 ± 4.5%, P < 0.002), as was nitroglycerin-mediated dilatation (15.2 ± 9.0% vs. 5.6 ± 6.4%, P < 0.003). Frequency of chest pain episodes was significantly reduced after 13 weeks of folic acid treatment.

Conclusion: Our findings establish the association between the C677T mutation, endothelial cell dysfunction and cardiac syndrome X, and provide a novel and simple therapy for a subset of patients with syndrome X and homozygosity for the C677T mutation.

At the WHO meeting on primary immunodeficiency held in Orvetto, Italy in 1994, mutations in the genes involved in the classical PID disorders, such as X-linked agammaglobulinemia (Bruton).

Background: Laron Syndrome, first described in Israel, is a form of dwarfism similar to isolated growth hormone deficiency caused by molecular defects in the GH[1] receptor gene.

Objective: To characterize the molecular defects of the GH-R[2] in Laron syndrome patients followed in our clinic.

Methods: Of the 63 patients in the cohort, we investigated 31 patients and 32 relatives belonging to several ethnic origins. Molecular analysis of the GH-R gene was performed using the single strand conformation polymorphism and DNA sequencing techniques.

Results: Eleven molecular defects including a novel mutation were found. Twenty-two patients carried mutations in the extracellular domain, one in the transmembrane domain, and 3 siblings with typical Laron syndrome presented a normal GH-R. Of interest are, on one hand, different mutations within the same ethnic groups: W-15X and 5, 6 exon deletion in Jewish-Iraqis, and E180 splice and 5, 6 exon deletion in Jewish-Moroccans; and on the other hand, identical findings in patients from distinct regions: the 785-1 G to T mutation in an Israeli-Druze and a Peruvian patient. A polymorphism in exon 6, Gly168Gly, was found in 15 probands. One typical Laron patient from Greece was heterozygous for R43X in exon 4 and heterozygous for Gly168Gly. In addition, a novel mutation in exon 5: substitution of T to G replacing tyrosine 86 for aspartic acid (Y86D) is described.

Conclusions: This study demonstrates: a) an increased focal incidence of Laron syndrome in different ethnic groups from our area with a high incidence of consanguinity; and b) a relationship between molecular defects of the GH-R, ethnic group and geographic area.

Background: Primary pulmonary hypertension is a rare disorder, characterized by progressive pulmonary hypertension and right heart failure. It may be familial or sporadic. Mutations in bone morphogenetic protein receptor II (BMPR2), a member of the transforming growth factor-beta receptor superfamily of receptors, underlie many cases of the disorder.

Objectives: To perform molecular analysis of a patient with familial PPH[1] and provide her and her family with suitable genetic counseling.

Methods: DNA was extracted from 10 ml whole blood, and the BMPR2 gene was screened for mutations. Individual exons were amplified by polymerase chain reaction and sequenced. Mutation confirmation and molecular characterization of additional family members was performed using restriction enzyme analysis followed by appropriate genetic counseling.

Results: We identified a novel T to C missense mutation expected to result in substitution of arginine for a conserved cysteine in the ligand-binding domain of BMPR2. Screening of family members demonstrated the presence of the mutation in the father and a younger asymptomatic sister of the index patient.

Conclusions: Molecular diagnosis in PPH allows for identification of at-risk family members and raises the option of earlier diagnosis and possibly instituting earlier treatment in affected individuals. However, molecular screening of asymptomatic family members raises difficult ethical questions that can only be resolved by conducting large multicenter prospective studies in BMPR2 carriers.

Background: Gaucher disease results from the accumulation of glucosylceramide (glucocerebroside) in tissues of affected persons. Patients sharing the same genotype present with widely varying degrees of lipid storage and of clinical manifestations.

Objectives: To determine whether variation in the glucosylceramide synthase (UDPGlucose ceramide glucosyltransferase) gene, which encodes the enzyme that regulates the synthesis of glucocerebroside, could account for the variability and clinical manifestations.

Methods: Patients homozygous for the 1226G (N370S) mutation, the most common in the Ashkenazi Jewish population, were investigated. The exons and flanking sequences of the gene were sequenced using DNA derived from five very mild Gaucher disease patients and four patients with relatively severe Gaucher disease. Results: One polymorphism was found in the coding region, but this did not change any amino acids. Seven other polymorphisms were found in introns and in the 5' untranslated region. Some of these were single nucleotide polymorphisms; others were insertions. The mutations appear to be in linkage equilibrium and none were found with a significantly higher frequency in either severe or mildly affected individuals.

Conclusions: Mutations in the glucosylceramide synthase gene do not appear to count for the variability in expression of the common Jewish Gaucher disease mutation.