Ashkenazi Jewish Descent Research Articles

Bloom syndrome

Bloom Syndrome (BS, MIM #210900) is an autosomal recessive genetic disorder caused by a mutation in the BLM gene, which codes for the DNA repair enzyme RecQL3 helicase. Without proper DNA repair mechanisms, abnormal DNA exchange takes place between sister chromatids and results in genetic instability that may lead to cancer, especially lymphoma and acute myelogenous leukemia, lower and upper gastrointestinal tract neoplasias, cutaneous tumors, and neoplasias in the genitalia and urinary tract. BS patients are usually of Ashkenazi Jewish descent and exhibit narrow facial features, elongated limbs, and several dermatologic complications including photosensitivity, poikiloderma, and telangiectatic erythema. The most concerning manifestation of BS is multiple malignancies, which require frequent screenings and strict vigilance by the physician. Therefore, distinguishing between BS and other dermatologic syndromes of similar presentation such as Rothmund-Thomson Syndrome, Erythropoietic Protoporphyria, and Cockayne Syndrome is paramount to disease management and to prolonging life. BS can be diagnosed through a variety of DNA sequencing methods, and genetic testing is available for high-risk populations. This review consolidates several sources on BS sequelae and aims to suggest the importance of differentiating BS from other dermatologic conditions. This paper also elucidates the recently discovered BRAFT and FANCM protein complexes that link BS and Fanconi anemia.

Validation for Clinical Use of, and Initial Clinical Experience with, a Novel Approach to Population-Based Carrier Screening using High-Throughput, Next-Generation DNA Sequencing

Traditional carrier screening assays are designed to look for only the most common mutations within a gene owing to cost considerations. Although this can yield high detection rates in specific populations for specific genes (such as cystic fibrosis in Caucasians), they are suboptimal for other ethnicities or for patients of mixed or unknown ethnic background. Next-generation DNA sequencing provides an opportunity to provide carrier screening using more comprehensive mutation panels that are limited primarily by information about the clinical impact of detected sequence changes. We describe a next-generation DNA sequencing-based assay capable of reliably screening patient samples in a timely and comprehensive manner. The analytic accuracy in a research setting has been documented. Here, we describe the additional studies performed to ensure the accuracy (analytic validity) and robustness of our assay for use in clinical practice and provide data from our experience offering this testing. Our clinical experience using this approach to screen 11,691 invitro fertilization patients has identified 449 mutant alleles: 447 in carriers and 2 in an affected individual. In total, we found 87 distinct mutations in 14 different genes. Approximately one quarter of the mutations found are not included in traditional, limited, mutation panels, including 16 known mutations unique to our panel, and novel truncating mutations in several genes.

Experience of BRCA1/2 mutation-negative young women from families with hereditary breast and ovarian cancer: a qualitative study.

BackgroundLittle is known about the experience of young women who become aware of their parent’s BRCA1 or BRCA2 (BRCA) mutation status as adolescents or young adults. There is also currently a gap in the literature pertaining to those who are found to be negative for their familial mutation. We aimed to investigate the experience of these mutation-negative young women from hereditary breast and ovarian cancer (HBOC) families.MethodsUsing a semi-structured questionnaire we interviewed 8 women. All of the women were non-carriers of their familial mutation and had learned of the mutation in their family as adolescents or young adults at least 6 months prior to undergoing genetic testing. All interviews were audio recorded, transcribed, and independently analyzed by the investigators. This was followed by an in-depth cross-case analysis, enabling the formulation of emergent themes.ResultsThe women’s age ranged from 22 to 37 years old and all were of Ashkenazi Jewish descent. Prominent emergent themes from the interviews included the impact of how and when the familial mutation status was disclosed, the factors influencing when a young woman chooses to undergo predictive genetic testing, the predictors of post-test adjustment and risk perception, as well as the impact of familial cancer experience versus the familial mutation.ConclusionsBy eliciting detailed patient narratives we have begun to show that this generation of BRCA mutation-negative young women is likely still affected by the degree of cancer history in their family, even with their understanding of the genetic contribution to disease. Larger studies with tightened participant characteristics, as well as studies involving women from different cultural backgrounds, are needed to further define the experience and needs of true negative young women from HBOC families.

Carrier frequency of two BBS2 mutations in the Ashkenazi population

Bardet-Biedl syndrome (BBS) is known to be caused by numerous mutations that occur in at least 15 of the BBS genes. As the disease follows an autosomal recessive pattern of inheritance, carrier screening can be performed for at-risk couples, but the number of potential mutation sites to screen can be daunting. Ethnic studies can help to narrow this range by highlighting mutations that are present at higher percentages in certain populations. In this article, the carrier frequency for two mutations that occur in the BBS2 gene, c.311A>C and c.1895G>C were studied in individuals of Ashkenazi Jewish descent in order to advise on including them in existing mutation panels for this population. Carrier screenings were performed on individuals from the Ashkenazi Jewish population using a combination of TaqMan genotyping assays followed by real-time polymerase chain reaction (PCR) and allelic discrimination, and allele-specific PCR confirmed by restriction analysis. The combined results indicated carrier frequencies of 0.473% (±0.0071%) for the c.311A>C mutation and 0.261% (±0.0064%) for the c.1895G>C mutation. On the basis of these frequencies, we believe that the two mutations should be considered for inclusion in screening panels for the Ashkenazi population.

High mammographic density in women of Ashkenazi Jewish descent

IntroductionPercent mammographic density (PMD) adjusted for age and body mass index is one of the strongest risk factors for breast cancer and is known to be approximately 60% heritable. Here we report a finding of an association between genetic ancestry and adjusted PMD.MethodsWe selected self-identified Caucasian women in the California Pacific Medical Center Research Institute Cohort whose screening mammograms placed them in the top or bottom quintiles of age-adjusted and body mass index-adjusted PMD. Our final dataset included 474 women with the highest adjusted PMD and 469 with the lowest genotyped on the Illumina 1 M platform. Principal component analysis (PCA) and identity-by-descent analyses allowed us to infer the women's genetic ancestry and correlate it with adjusted PMD.ResultsWomen of Ashkenazi Jewish ancestry, as defined by the first principal component of PCA and identity-by-descent analyses, represented approximately 15% of the sample. Ashkenazi Jewish ancestry, defined by the first principal component of PCA, was associated with higher adjusted PMD (P = 0.004). Using multivariate regression to adjust for epidemiologic factors associated with PMD, including age at parity and use of postmenopausal hormone therapy, did not attenuate the association.ConclusionsWomen of Ashkenazi Jewish ancestry, based on genetic analysis, are more likely to have high age-adjusted and body mass index-adjusted PMD. Ashkenazi Jews may have a unique set of genetic variants or environmental risk factors that increase mammographic density.

A deleterious mutation in thePEX2gene causes Zellweger syndrome in individuals of Ashkenazi Jewish descent

Zellweger syndrome is known to be caused by numerous mutations that occur in at least 12 of the PEX genes. While phenotypes vary, many are severely debilitating, and death can result in affected newborns. Since the disease follows an autosomal recessive pattern of inheritance, carrier screening can be done for at-risk couples, but the number of potential mutations sites to screen can be daunting. Ethnicity-specific studies can help narrow this range by highlighting mutations that are present at higher percentages in certain populations. In this article, the carrier frequencies for two mutations causative of the severe Zellweger syndrome spectrum phenotype that occur in the PEX2 gene, c.355C>T and c.550del, were studied in individuals of Ashkenazi Jewish descent in order to advise on inclusion in existing carrier screening mutation panels for this population. The screening was performed for 2093 individuals through the use of TaqMan genotyping assays, real-time PCR, and allelic discrimination. Results indicated a carrier frequency of 0.813% (±0.385%) for the c.355C>T mutation and a carrier frequency of 0.00% (±0.00%) for the c.550del mutation. On the basis of these frequencies, we believe that the c.355C>T mutation should be considered for inclusion in carrier screening panels for the Ashkenazi population.

Implication of a rare deletion at distal 16p11.2 in schizophrenia.

Large genomic copy number variations have been implicated as strong risk factors for schizophrenia. However, the rarity of these events has created challenges for the identification of further pathogenic loci, and extremely large samples are required to provide convincing replication. To detect novel copy number variations that increase the susceptibility to schizophrenia by using 2 ethnically homogeneous discovery cohorts and replication in large samples. Genetic association study of microarray data. Samples of DNA were collected at 9 sites from different countries. Two discovery cohorts consisted of 790 cases with schizophrenia and schizoaffective disorder and 1347 controls of Ashkenazi Jewish descent and 662 parent-offspring trios from Bulgaria, of which the offspring had schizophrenia or schizoaffective disorder. Replication data sets consisted of 12,398 cases and 17,945 controls. Statistically increased rate of specific copy number variations in cases vs controls. One novel locus was implicated: a deletion at distal 16p11.2, which does not overlap the proximal 16p11.2 locus previously reported in schizophrenia and autism. Deletions at this locus were found in 13 of 13,850 cases (0.094%) and 3 of 19,954 controls (0.015%) (odds ratio, 6.25 [95% CI, 1.78-21.93]; P = .001, Fisher exact test). Deletions at distal 16p11.2 have been previously implicated in developmental delay and obesity. The region contains 9 genes, several of which are implicated in neurological diseases, regulation of body weight, and glucose homeostasis. A telomeric extension of the deletion, observed in about half the cases but no controls, potentially implicates an additional 8 genes. Our findings add a new locus to the list of copy number variations that increase the risk for development of schizophrenia.

Case Scenario

Cook-Sather, Scott D.*; Viola, Luigi†; Zur, Karen B.‡; Rubin, Berish Y.§ Author Information

DGAT1 mutation is linked to a congenital diarrheal disorder

Congenital diarrheal disorders (CDDs) are a collection of rare, heterogeneous enteropathies with early onset and often severe outcomes. Here, we report a family of Ashkenazi Jewish descent, with 2 out of 3 children affected by CDD. Both affected children presented 3 days after birth with severe, intractable diarrhea. One child died from complications at age 17 months. The second child showed marked improvement, with resolution of most symptoms at 10 to 12 months of age. Using exome sequencing, we identified a rare splice site mutation in the DGAT1 gene and found that both affected children were homozygous carriers. Molecular analysis of the mutant allele indicated a total loss of function, with no detectable DGAT1 protein or activity produced. The precise cause of diarrhea is unknown, but we speculate that it relates to abnormal fat absorption and buildup of DGAT substrates in the intestinal mucosa. Our results identify DGAT1 loss-of-function mutations as a rare cause of CDDs. These findings prompt concern for DGAT1 inhibition in humans, which is being assessed for treating metabolic and other diseases.

Case Scenario

F AMILIAL dysautonomia (FD, also known as Riley-Day syndrome) is a rare (1:3,700 live births) autosomal recessive disorder, largely afflicting those of Ashkenazi Jewish descent. One of five hereditary sensory and autonomic neuropathies (HSAN, type III) influencing the development and survival of varied sensory, sympathetic, and parasympathetic neurons, FD is characterized by profound autonomic dysfunction resulting in sudden hypertension, orthostatic hypotension, vomiting, and/or abnormal sweating. Autonomic instability may result in significant morbidity and mortality in the perioperative period. Recent discoveries in disease genetics and pathophysiology have lead to improved treatments for FD patients, greatly reducing the incidence of dysautonomic crises and diminishing symptoms overall. Mutations in the gene for inhibitor of light polypeptide gene enhancer in B-cells, kinase complex-associated protein (IKBKAP), causing reductions in the cellular protein IKAP, have been linked to FD. In addition, tissue concentrations of monoamine oxidase A, an enzyme involved in the metabolic transformation of norepinephrine and dopamine, are low in FD. Both tocotrienols (vitamin E family) and epigallocatechin-3-gallate (a flavonoid found in green tea) increase its cellular concentration (fig. 1). Oral tocotrienols also increase monoamine oxidase A levels in FD patients. We describe the management of a child with FD scheduled for adenoidectomy and the impact of maintaining her long-term treatment with tocotrienols and green tea extract (GTE) on her perioperative course.

Secondary Variants in Individuals Undergoing Exome Sequencing: Screening of 572 Individuals Identifies High-Penetrance Mutations in Cancer-Susceptibility Genes

Genome- and exome-sequencing costs are continuing to fall, and many individuals are undergoing these assessments as research participants and patients. The issue of secondary (so-called incidental) findings in exome analysis is controversial, and data are needed on methods of detection and their frequency. We piloted secondary variant detection by analyzing exomes for mutations in cancer-susceptibility syndromes in subjects ascertained for atherosclerosis phenotypes. We performed exome sequencing on 572 ClinSeq participants, and in 37 genes, we interpreted variants that cause high-penetrance cancer syndromes by using an algorithm that filtered results on the basis of mutation type, quality, and frequency and that filtered mutation-database entries on the basis of defined categories of causation. We identified 454 sequence variants that differed from the human reference. Exclusions were made on the basis of sequence quality (26 variants) and high frequency in the cohort (77 variants) or dbSNP (17 variants), leaving 334 variants of potential clinical importance. These were further filtered on the basis of curation of literature reports. Seven participants, four of whom were of Ashkenazi Jewish descent and three of whom did not meet family-history-based referral criteria, had deleterious BRCA1 or BRCA2 mutations. One participant had a deleterious SDHC mutation, which causes paragangliomas. Exome sequencing, coupled with multidisciplinary interpretation, detected clinically important mutations in cancer-susceptibility genes; four of such mutations were in individuals without a significant family history of disease. We conclude that secondary variants of high clinical importance will be detected at an appreciable frequency in exomes, and we suggest that priority be given to the development of more efficient modes of interpretation with trials in larger patient groups.

A Genome-Wide Scan of Ashkenazi Jewish Crohn's Disease Suggests Novel Susceptibility Loci

Crohn's disease (CD) is a complex disorder resulting from the interaction of intestinal microbiota with the host immune system in genetically susceptible individuals. The largest meta-analysis of genome-wide association to date identified 71 CD–susceptibility loci in individuals of European ancestry. An important epidemiological feature of CD is that it is 2–4 times more prevalent among individuals of Ashkenazi Jewish (AJ) descent compared to non-Jewish Europeans (NJ). To explore genetic variation associated with CD in AJs, we conducted a genome-wide association study (GWAS) by combining raw genotype data across 10 AJ cohorts consisting of 907 cases and 2,345 controls in the discovery stage, followed up by a replication study in 971 cases and 2,124 controls. We confirmed genome-wide significant associations of 9 known CD loci in AJs and replicated 3 additional loci with strong signal (p<5×10−6). Novel signals detected among AJs were mapped to chromosomes 5q21.1 (rs7705924, combined p = 2×10−8; combined odds ratio OR = 1.48), 2p15 (rs6545946, p = 7×10−9; OR = 1.16), 8q21.11 (rs12677663, p = 2×10−8; OR = 1.15), 10q26.3 (rs10734105, p = 3×10−8; OR = 1.27), and 11q12.1 (rs11229030, p = 8×10−9; OR = 1.15), implicating biologically plausible candidate genes, including RPL7, CPAMD8, PRG2, and PRG3. In all, the 16 replicated and newly discovered loci, in addition to the three coding NOD2 variants, accounted for 11.2% of the total genetic variance for CD risk in the AJ population. This study demonstrates the complementary value of genetic studies in the Ashkenazim.

Camptocormia: don’t forget muscle disease in the movement disorder clinic

The cause of isolated camptocormia or ‘bent spine syndrome’ is various and often difficult to establish [1]. Patients may present to neurologists or musculoskeletal specialists but many remain without diagnosis. We recently reported a patient with camptocormia due to facioscapulohumeral dystrophy (FSHD) that had been initially diagnosed as idiopathic axial dystonia in a movement disorder clinic [2]. A second case of muscle disease masquerading as dystonia has now come to light. In this report we provide helpful diagnostic pointers that may help neurologists to pick up these cases and avoid inappropriate treatment. The patient was of non-consanguineous Ashkenazi Jewish descent. She first presented to a neurologist at the age of 66 with a 9-year history of involuntary bending of her spine when walking. Any attempt to overcome the forward flexion led to shortness of breath and increased difficulty walking. Pushing a shopping trolley caused significant improvement in her posture. She also complained of a tight band sensation around her upper abdomen. She had a past history of rheumatic fever at 8 years of age (no history of chorea) with subsequent mitral valve disease necessitating replacement with a prosthetic metal valve at the age of 46. Six years before presentation she had an episode of presumed polymyalgia rheumatica (based on symptoms of pain and stiffness around her neck, shoulders and upper arms and an elevated ESR—between 40–50 mm/h), which settled with a short course of steroids. She also had an 8-year history of deafness in the left ear. Her medications included warfarin, digoxin, bisoprolol, losartan, furosemide, spironolactone and quinine sulphate. She had never been exposed to dopamine blocking drugs. Her mother had a similar posture in her later years. On examination she had spontaneous flexion of the trunk, which worsened the further she walked. Using a rollator or placing her hands on her thighs enabled her to straighten her trunk (video). There was no fixed deformity when lying supine, and spinal imaging revealed multi-level degenerative changes but no spinal cord compression or radiculopathy. She was diagnosed with camptocormia due to idiopathic axial dystonia. DYT1 testing was negative. Focal myopathy was considered a possible cause but electromyography was felt to be contraindicated due to her treatment with warfarin. L-dopa (150 mg/day), anticholinergic drugs (trihexyphenidyl 6 mg/day and tetrabenazine 12.5 mg/day) Electronic supplementary material The online version of this article (doi:10.1007/s00415-012-6448-z) contains supplementary material, which is available to authorized users.

P442 Replication of susceptibility loci identified by genome-wide association studies for ulcerative colitis in Japanese population

clinic at UCLH. The family was of Ashkenazi Jewish descent and comprised 800 individuals across 4 generations living in 7 cities on 3 continents. DNA was collected from 160 members including all 40 affecteds. Microarray transcriptomics was performed on cultured monocyte-derived macrophages (n = 8) and histologically non-inflamed rectal biopsies (n = 4). 38 IBD-associated single nucleotide polymorphisms (SNPs) were genotyped in 160 individuals and simulations were conducted to assess the contribution of these to the disease prevalence. 300,000 SNPs were genotyped in 40 affecteds and 60 unaffecteds and a novel parallel method was developed to reconstruct haplotype flow within the family. The exomes (n = 6) and whole-genomes (n = 8) were sequenced. Results: The affected family members displayed phenotypic heterogeneity with ~80% having a diagnosis of classical Crohn’s disease. All affecteds were non-smokers. The average age at diagnosis was 18 years (95% CI 15 21) and a quarter had undergone surgical resections. Although affecteds had a significant enrichment for IBD-associated SNPs, simulations demonstrated a significant excess of disease cases beyond that expected. Consistent with a complex disease and the presence of a number of sporadic cases, no genome-wide significant linkage was found and there was no gross transcriptomic abnormality shared by all affected individuals studied. Highthroughput sequencing identified a number of candidate variants on commonly shared haplotypes and these are currently undergoing bioinformatic prioritisation. Conclusions: Known IBD-associated SNPs are unable to account for the high degree of familial aggregation observed in this family, the largest IBD pedigree identified to date. Linkage analysis suggests the aetiology of IBD in this family is complex. An integrated approach employing the use of linkage, nextgeneration sequencing and transcriptomics is being used in ongoing studies to identify rare disease-causing variants and to understand their role in the pathogenesis of IBD in this family.

Gender differences in the IL6 −174G>C and ESR2 1730G>A polymorphisms and the risk of Parkinson's disease

The −174G>C (rs1800795) single nucleotide polymorphism (SNP) in the promoter of the interleukin-6 (IL6) gene and the 1730G>A (rs4986938) SNP in the estrogen receptor beta (ESR2) may influence the risk of Parkinson's disease (PD). We investigated these SNPs in 380 unrelated US Caucasian PD cases and 522 controls, including 452 individuals of Ashkenazi Jewish (AJ) origin (260 PD, 192 controls). The G allele of the −174G>C SNP was more common in AJ PD cases (p=0.033) as well as in Non-Jewish (NJ) men with PD (p=0.022). The GG genotype increased the risk of PD by over two fold in NJ men (OR=2.11, 95%CI: 1.14–3.89, p=0.017), and approached significance in the total AJ group with PD (OR=1.42, 95%CI: 0.97–2.06, p=0.067). The A allele of the ESR2 1730G>A SNP was associated with a decreased risk for PD in AJ women, and in this group, having the AA genotype decreased the risk of PD by half (OR=0.45, 95%CI: 0.22–0.92, p=0.029). Our data supports a role for the IL6 −174G>C G allele in AJ individuals overall. In NJ Caucasians, this role appears to be gender mediated. In both groups, the effect is independent from ESR2 1730G>A. A separate association for the ESR2 1730G>A SNP was found exclusively in women of AJ descent. Other polymorphisms in tight linkage disequilibrium with the SNP differentially influencing expression, ethnic differences in allele distribution, and gender differences in genetic load related to PD, may underlie our findings. Larger studies in diverse populations, including analysis of surrounding regions are recommended.

The glucokinase mutation p.T206P is common among MODY patients of Jewish Ashkenazi descent

Maturity-onset diabetes of the young (MODY) is characterized by an autosomal dominant mode of inheritance; a primary defect in insulin secretion with non-ketotic hyperglycemia, age of onset under 25 yr; and lack of autoantibodies. Heterozygous mutations in glucokinase (GCK) are associated with mild fasting hyperglycemia and gestational diabetes mellitus while homozygous or compound heterozygous GCK mutations result in permanent neonatal diabetes mellitus. Given that both the Israeli-Arabic and the various Israeli-Jewish communities tend to maintain ethnic seclusion, we speculated that it would be possible to identify a relatively narrow spectrum of mutations in the Israeli population. To characterize the genetic basis of GCK-MODY in the different ethnic groups of the Israeli population. Patients with clinically identified GCK-MODY and their first degree family members. Molecular analysis of GCK was performed on genomic DNA using polymerase chain reaction, denaturing gradient gel electrophoresis (DGGE), and sequencing. Bioinformatic model was preformed using the NEST program. Mutations in GCK were identified in 25 families and were all family-specific, except c.616A>C. p.T206P. This mutation was identified in six unrelated families, all patients from a Jewish-Ashkenazi descent, thus indicating an ethno-genetic correlation. A simple, fast, and relatively cheap DGGE/restriction-digestion assay was developed. The high incidence of the mutant allele in GCK-MODY patients of Jewish-Ashkenazi descent suggests a founder effect. We propose that clinically identified GCK-MODY patients of Jewish-Ashkenazi origin be first tested for this mutation.

Canavan Disease: A Novel Mutation

Canavan disease, an autosomal recessive inherited leukodystrophy caused by an aspartoacylase deficiency, is common among children of Ashkenazi Jewish descent. We report on a non-Jewish female infant who presented at age 6 months with progressive macrocephaly and developmental delay. A sequence analysis of the aspartoacylase gene revealed compound heterozygosity for a known mutation and for the mutation c.432G>A in exon 2, which has not yet been described in Canavan disease.

Adiponectin gene and risk of colorectal cancer

Background:Genes of the adiponectin pathway are interesting candidates for colorectal cancer risk based on the potential association between colorectal cancer and obesity. However, variants of the adiponectin gene (ADIPOQ) have been demonstrated to be inconsistently associated with risk of colorectal cancer.Methods:The current study attempted to evaluate these findings by examining several single nucleotide polymorphisms (SNPs) that were previously genotyped as part of a genome-wide association study in the ADIPOQ gene. Genotyping was also performed for a previously reported risk variant, rs266729, in 1062 individuals with a diagnosis of colorectal cancer and 1062 controls matched on age, gender and ethnicity (Jewish or not Jewish) as part of a population-based case–control study in Israel.Results:No evidence was found for an association between ADIPOQ and risk of colorectal cancer. The single nucleotide variant previously associated with decreased risk of colorectal cancer, rs266729, revealed an adjusted odds ratio of 1.04; 95% confidence interval, 0.88–1.23.Conclusion:The SNP, rs266729, was not strongly associated with colorectal cancer in patients of Ashkenazi Jewish descent or other ethnic groups in Israel.

Evaluation of 22 genetic variants with Crohn's Disease risk in the Ashkenazi Jewish population: a case-control study

BackgroundCrohn's disease (CD) has the highest prevalence among individuals of Ashkenazi Jewish (AJ) descent compared to non-Jewish Caucasian populations (NJ). We evaluated a set of well-established CD-susceptibility variants to determine if they can explain the increased CD risk in the AJ population.MethodsWe recruited 369 AJ CD patients and 503 AJ controls, genotyped 22 single nucleotide polymorphisms (SNPs) at or near 10 CD-associated genes, NOD2, IL23R, IRGM, ATG16L1, PTGER4, NKX2-3, IL12B, PTPN2, TNFSF15 and STAT3, and assessed their association with CD status. We generated genetic scores based on the risk allele count alone and the risk allele count weighed by the effect size, and evaluated their predictive value.ResultsThree NOD2 SNPs, two IL23R SNPs, and one SNP each at IRGM and PTGER4 were independently associated with CD risk. Carriage of 7 or more copies of these risk alleles or the weighted genetic risk score of 7 or greater correctly classified 92% (allelic count score) and 83% (weighted score) of the controls; however, only 29% and 47% of the cases were identified as having the disease, respectively. This cutoff was associated with a >4-fold increased disease risk (p < 10e-16).ConclusionsCD-associated genetic risks were similar to those reported in NJ population and are unlikely to explain the excess prevalence of the disease in AJ individuals. These results support the existence of novel, yet unidentified, genetic variants unique to this population. Understanding of ethnic and racial differences in disease susceptibility may help unravel the pathogenesis of CD leading to new personalized diagnostic and therapeutic approaches.

A founder mutation in the MPL gene causes congenital amegakaryocytic thrombocytopenia (CAMT) in the Ashkenazi Jewish population

Congenital amegakaryocytic thrombocytopenia (MIM # 604498) (CAMT) is a rare inherited disease presenting as severe thrombocytopenia in infancy. Untreated, many CAMT patients develop aplastic anemia within the first decade of life; the only effective treatment of CAMT is bone marrow transplantation. CAMT is the result of the presence of homozygous or compound heterozygous mutations in the thrombopoietin receptor-encoding gene, MPL. We report here the identification and characterization of a founder mutation in MPL in the Ashkenazi Jewish (AJ) population. This mutation, termed c.79 + 2T > A, is a T to A transversion in the invariant second base of the intron 1 donor splice site. Analysis of a random sample of 2018 individuals of AJ descent revealed a carrier frequency of approximately 1 in 75. Genotyping of six loci adjacent to the MPL gene in the proband and in the 27 individuals identified as carriers of the c.79 + 2T > A mutation revealed that the presence of this mutation in the AJ population is due to a single founder. The observed carrier frequency predicts an incidence of CAMT in the AJ population of approximately 1 in 22,500 pregnancies. The identification of this mutation will enable population carrier testing and will facilitate the identification and treatment of individuals homozygous for this mutation.