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Deciphering the spectrum and founder disease-causing variants (DCVs) in specific populations can shape and facilitate the diagnostic process of Lynch Syndrome (LS). The aim of this report was to comprehensively update on the genetic landscape of LS in the ethnically diverse Israeli-Jewish population. The cohort included 1080 carriers from 588 families; some from underrepresented, understudied Israeli ethnic groups recruited from 8 genetic institutes and high-risk clinics throughout the country. Variant classification was performed according to the American College of Medical Genetics criteria. A total of 157 DCVs were identified, 12 are reported here for the first time, and 9 reclassified. MSH2 DCVs were identified in 286 families (49%). Most DCVs (125/157, 80%) were noted in one or two families only. Sixteen DCVs, each detected in ≥ 5 families, and accounted for LS in 378/588 (64%) families. Constitutional mismatch repair deficiency (CMMRD) was diagnosed in 7 families. Twenty-five carriers (2.3%) had an additional DCV or risk alleles in another cancer susceptibility gene. In conclusion, MMR gene variant distribution in Israel is diverse. MSH2 is most commonly mutated due to founder DCVs. Though the 16 prevalent LS-associated DCVs were frequently detected in our cohort, none of them is frequently reported in the general population. These data should facilitate variant interpretation, spouse and cascade testing., Competing Interests: Declarations Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Background: Autosomal recessive conditions are common in consanguineous populations. Since consanguinity is common in the Israeli Arab population, we evaluated the rate of MUTYH polyposis (MAP) among polyposis patients in this population and studied Pathogenic Variants (PVs) spectrum., Methods: We reviewed health records of all Arab and Druze polyposis patients referred for counseling during 2013-2020 who fulfilled the Israeli Genetic Society criteria for MUTYH/APC testing, in a tertiary center in Northern Israel and four additional gastro-genetic clinics in Israel., Results: The Northern cohort included 37 patients from 30 unrelated families; 8(26.6%) carried bi-allelic MUTYH PVs. The major variant p.Glu452del was detected in 6/8 Druze and Muslim families who shared the same haplotype. Other PVs detected in both cohorts included p.Tyr56Ter, p.His57Arg, c.849+3A>C, p.Ala357fs, and p.Tyr151Cys. Among bi-allelic carriers, 88% reported consanguinity, and 100% had positive family history for polyposis or colorectal cancer (CRC). Generally, the age of CRC was 10 years younger than reported in the general MAP population., Conclusions: MAP accounted for 27% of polyposis cases in the Arab population of Northern Israel. PVs spectrum is unique, with high frequency of the founder variant p.Glu452del. Our results may inform the genetic testing strategy in the Israeli Arab population., Competing Interests: Conflict of interest No conflict of interest declared by the authors., (Copyright © 2023. Published by Elsevier Ltd.)

Introduction: Hereditary breast and ovarian cancer (HBOC) is predominantly accounted for by pathogenic variants (PVs) in BRCA1/BRCA2 genes. Population screening for recurring PVs in Ashkenazi Jews (AJ) was incorporated into the Israeli health basket in 2020, increasing the identification of BRCA carriers. Information on cancer risks for each PV in Israel is limited., Aims: To assess genotype phenotype correlations of recurring BRCA PVs in Israeli carriers., Methods: A retrospective cohort of 3,478 BRCA carriers followed-up in 12 medical centers, comprising the HBOC Consortium, formed the basis of the study. Data were collected using the electronic database, and analyzed by Chi square, t-tests and Kaplan-Meier survival analysis., Results: Overall, 2145 BRCA1, 1131 BRCA2, and 22 double heterozygote PV carriers were analyzed. BRCA1 carriers had more cases of cancer (53.1% vs. 44.8%, p<0.001), ovarian cancer (OC) (17.1% vs. 10.6%, p<0.001), younger age at breast cancer (BC) (45.4 ±11.6SD years vs. 49.1 ±11.1SD years, p<0.001) and OC diagnosis (52.8 ±10.1SD yrs. vs. 61±10.6SD yrs. p<0.001), and more family history of BC (64.5% vs. 59.0%, p<0.001) and OC (36.7% vs. 27.3%, p<0.001) compared with BRCA2 carriers. Carriers of BRCA15382insC had more BC and less OC than BRCA1185delAG: 46.4% vs. 38.6% and 12.9% vs. 17.6% (p<0.04), respectively., Conclusions: In our population, similar to others, BRCA1 carriers have higher cancer rates and earlier age at diagnosis compared with BRCA2 carriers. The two recurring BRCA1 PVs have different risks: 5382insC carriers had more BC; 185delAG carriers had more OC. Risk-reducing measures should be based on variant-specific cancer risk.

Germline pathogenic sequence variants (PSVs) in BRCA1 substantially increase risk for developing breast (BC) and ovarian cancer (OvC). Yet, incomplete penetrance suggests that modifier factors affect phenotypic expression of mutant BRCA1 alleles. Analysis of identical BRCA1 PSV carriers of diverse ethnicities may provide further evidence for modifier factors. Female carriers of the 185delAG BRCA1 PSV identified through high-risk clinics in Israel, and Manchester England from 1998-2018 were eligible. Data were retrieved from patients records and confirmed (in Israel) by cross referencing with the Israeli National Cancer Registry. Overall, 2503 female carriers were included: 1715 (71.4%) Ashkenazi Jews (AJ), 201 (8.3%) Iraqi Jews and 383 (15.9%) of mixed ethnicity. In 102 (4.2%) cases ethnicity could not be ascertained. Of Israeli AJ carriers 649 (37.8%), 256 (14.9%) and 62 (3.6%) were diagnosed with BC, OvC or both cancers, respectively. For the Iraqi Jews these frequencies were 76 (37.8%), 43 (21.4%), and 8 (3.98%), respectively. Age at diagnosis of BC in AJ and Iraqi Jews was 46.7 ± 12.3 years and 52.8 ± 12.2 years, respectively (p = 0.001). For OvC age at diagnosis for AJ was 53.5 ± 10.7 years and for Iraqi Jews 50.1 ± 8.8 years (p = 0.0027). No differences in these parameters were noted between English Jews (n = 110) and non-Jews (n = 32). Age at diagnosis of BC and OvC differs between AJ and Iraqi Jews who carry an identical BRCA1 PSV. This finding supports the existence of modifier factors that may be ethnic specific.

Background: Carriers of pathogenic variants (PVs) in moderate-high-penetrance cancer susceptibility genes are offered tailored surveillance schemes for early cancer diagnosis. The clinical implications of low-penetrance variant carriers are less clear., Methods: Clinical and demographic data were retrieved for a cohort of Israeli individuals who underwent oncogenetic testing by the 30-gene cancer panel at Color Genomics laboratory, between 04/2013 and 12/2018., Results: Of 758 genotyped individuals, 504 had been diagnosed with cancer prior to testing: 283 (56%) had breast cancer and 106 (21%) colorectal cancer. Pathogenic or likely pathogenic (P/LP) variants were detected in 123 (16%) individuals. Overall, 44 different P/LP variants were detected in 18/30 cancer susceptibility genes; 20 of them were founder/recurrent mutations. Of the carriers, 39 (32%), 10 (8%), and 74 (60%) carried high-, moderate-, or low-penetrance variants, respectively. After excluding low-penetrance variants, 7% (33/504) of all cancer patients, 6% of breast or ovarian cancer patients were found to be carriers, as well as 7% (14/203) of individuals with colonic polyps, and 4% (11/254) of cancer-free individuals., Conclusions: The diagnostic yield of moderate- and high-penetrance PVs using multigene panel testing was 6%, with 3.7% carriers of non-recurrent PVs. This yield should be discussed during pre-test counseling, and emphasizes the need for harmonized recommendations regarding clinical implications of low-penetrance variants.

Objectives: Loss-of-function mutations of BMPR1A cause juvenile polyposis syndrome (JPS), but large genomic deletions in BMPR1A are rare, reported in few families only, and data regarding the associated phenotype are limited., Methods: We investigated clinical features and genomic data of 7 extended seemingly unrelated families with a genomic deletion of the entire coding region of BMPR1A. We defined mutation size, mutation prevalence, and tumor pathogenesis using whole-genome sequencing, targeted genotyping, and haplotype analysis., Results: Patients with JPS from 7 families of Bukharin Jewish ancestry carried a deletion of 429 kb, encompassing the BMPR1A coding sequence and 8 downstream genes. Haplotype analysis and testing controls identified this as a common founder mutation occurring in 1/124 individuals of Bukharin origin. Tumor testing did not demonstrate loss of heterozygosity. Among carriers, JPS was almost fully penetrant, but clinical features varied widely, ranging from mild to very severe, including pan-enteric polyps, gastritis, and colorectal, esophageal, and testicular cancer, and carriers with phenotypes, which would not have raised suspicion of JPS., Discussion: The phenotype in this large cohort was extremely variable, although all carriers shared the same variant and the same genetic background. New observations include a preponderance of adenomatous rather than juvenile polyps, possible association with testicular cancer, and unexpected upper gastrointestinal involvement.

Hereditary non-polyposis colon cancer is caused by mutations in DNA mismatch repair genes. The mutation spectrum in the Israeli population is poorly documented except for the c.1906G>C Ashkenazi founder mutation in the hMSH2 gene. To report our experience in HNPCC screening, the mutations detected and the clinical features among a cohort of Israeli patients. Diagnostic work-up was done in a multi-step process guided by clinical and ethnic information. Tumors of suspected patients were tested for microsatellite instability and immunohistochemistry. Based on tumor analyses, we proceeded to mutation screening by DHPLC followed by sequence analysis and multiplex ligase dependent probe amplification. Ashkenazi Jews were first tested for the c.1906G>C founder mutation. Of the 240 families, 24, including Arabs and Jews from different ethnic origins, were tested positive. All tumors that lost expression of mismatch repair proteins also showed microsatellite instability. There was evidence for involvement of hMSH2 (15) hMLH1 (6) and hMSH6 (3) genes. Mutations were identified in 17/24 (71%) patients: 6 Ashkenazi families harbored the c.1906G>C mutation. Eleven other mutations (2 nonsense, 3 splice site and 6 small deletions) were detected. Three of the mutations are novel. No gross deletions or insertions were detected. This is the first report that characterizes the profile of HNPCC in a cohort of patients in Israel. Tumor testing indicated that the 3 main MMR genes are involved, and that mutation spectrum is broad.

Background: Fanconi anemia complementation group C and Bloom syndrome, rare autosomal recessive disorders marked by chromosome instability, are especially prevalent in the Ashkenazi* Jewish community. A single predominant mutation for each has been reported in Ahshkenazi Jews: c.711+4A-->T (IVS4 +4 A-->T) in FACC and BLM(Ash) in Bloom syndrome. Individuals affected by either of these syndromes are characterized by susceptibility for developing malignancies, and we questioned whether heterozygote carriers have a similarly increased risk., Objectives: To estimate the cancer rate among FACC and BLM(Ash) carriers and their families over three previous generations in unselected Ashkenazi Jewish individuals., Methods: We studied 42 FACC carriers, 28 BLM(Ash) carriers and 43 controls. The control subjects were Ashkenazi Jews participating in our prenatal genetic screening program who tested negative for FACC and BLM(Ash). All subjects filled out a questionnaire regarding their own and a three-generation family history of cancer. The prevalence rates of cancer among relatives of FACC, BLM(Ash) and controls were computed and compared using the chi-square test., Results: In 463 relatives of FACC carriers, 45 malignancies were reported (9.7%) including 10 breast (2.2%) and 13 colon cancers (2.8%). Among 326 relatives of BLM(Ash) carriers there were 30 malignancies (9.2%) including 7 breast (2.1%) and 4 colon cancers (1.2%). Controls consisted of 503 family members with 63 reported malignancies (12.5%) including 11 breast (2.2%) and 11 colon cancers (2.2%)., Conclusions: We found no significantly increased prevalence of malignancies among carriers in at least three generations compared to the controls.

Inherited mutations in BRCA1 and BRCA2 lead to significantly increased risks of breast and ovarian cancer. We used epidemiologic methods to evaluate the relative risks of breast cancer vs. ovarian cancer among women of Ashkenazi Jewish ancestry with inherited mutations in BRCA1 or BRCA2. The cancer of a family's index case (i.e., breast cancer vs. ovarian cancer) was significantly associated with site-specific risks of cancer in relatives known to carry mutations in BRCA1 or BRCA2. Specifically, breast cancer risks were higher among relatives of breast cancer index cases compared with relatives of ovarian cancer index cases [hazard ratio (HR) = 3.0, P < 0.001 for BRCA1 carriers and HR = 4.8, P = 0.017 for BRCA2 carriers], and ovarian cancer risks were higher among relatives of ovarian cancer index cases compared with relatives of breast cancer index cases (HR = 7.2, P = 0.001 for BRCA1 carriers and HR = 15.8, P = 0.018 for BRCA2 carriers). Breast and ovarian cancer risks also increased with more recent year of birth. For each later decade of birth, risk increased 1.2-fold (P = 0.03). Effects of cancer site of the index case and of birth cohort were independent. These results suggest that both genetic and nongenetic factors modify cancer risks among BRCA1 and BRCA2 mutation carriers, and that genetic modifiers and other familial factors may influence risk specifically for either breast or ovarian cancer.

The Jews are an ancient and unique group of people linked by language, religion and customs in spite of their major geographical shifts, expulsions, forced conversions and massacres throughout their entire history. As a result of these historical events that led to repeated migration, the Jewish people became dispersed into various ethnic sub-groups. Between these ethnic groups exists heterogeneity, as well as some similarities, to the populations amongst whom they lived. Rare genetic diseases have been reported to be prevalent among the different groups of Jews, which for the most part can be explained by random genetic drift together with intra-familial marriages. In this publication, we will briefly discuss the origin of the various ethnic groups and some of the genetic diseases commonly found in them, with emphasis on the Ashkenazim, their prevalent genetic diseases and cancer susceptibility.