AOA2 is a rare progressive adolescent-onset disease characterised by cerebellar vermis atrophy, peripheral neuropathy and elevated serum alpha-fetoprotein (AFP) caused by pathogenic bi-allelic variants in SETX, encoding senataxin, involved in DNA repair and RNA maturation. Sanger sequencing of genomic DNA, co-segregation and oxidative stress functional studies were performed in Family 1. Trio whole-exome sequencing (WES), followed by SETX RNA and qRT-PCR analysis, were performed in Family 2. Sanger sequencing in Family 1 revealed two novel in-frame SETX deletion and duplication variants in trans (c.7009_7011del; p.Val2337del and c.7369_7371dup; p.His2457dup). Patients had increased induced chromosomal aberrations at baseline and following exposure to higher mitomycin-C concentration and increased sensitivity to oxidative stress at the lower mitomycin-C concentration in cell viability test. Trio WES in Family 2 revealed two novel SETX variants in trans, a nonsense variant (c.568C > T; p.Gln190*), and a deep intronic variant (c.5549-107A > G). Intronic variant analysis and SETX mRNA expression revealed activation of a cryptic exon introducing a premature stop codon (p.Met1850Lysfs*18) and resulting in aberrant splicing, as shown by qRT-PCR analysis, thus leading to higher levels of cryptic exon activation. Along with a second deleterious allele, this variant leads to low levels of SETX mRNA and disease manifestations. Our report expands the phenotypic spectrum of AOA2. Results provide initial support for the hypomorphic nature of the novel in-frame deletion and duplication variants in Family 1. Deep-intronic variant analysis of Family 2 variants potentially reveals a previously undescribed poison exon in the SETX gene, which may contribute to tailored therapy development.

Purpose:Usher syndrome (USH) is the most common cause for deaf-blindness. It is genetically and clinically heterogeneous and prevalent in populations with high consanguinity rate. We aim to characterize the set of genes and mutations that cause USH in the Israeli and Palestinian populations.Methods:Seventy-four families with USH were recruited (23 with USH type 1 [USH1], 33 with USH2, seven with USH3, four with atypical USH, and seven families with an undetermined USH type). All affected subjects underwent a full ocular evaluation. A comprehensive genetic analysis, including Sanger sequencing for the detection of founder mutations, homozygosity mapping, and whole exome sequencing in large families was performed.Results:In 79% of the families (59 out of 74), an autosomal recessive inheritance pattern could be determined. Mutation detection analysis led to the identification of biallelic causative mutations in 51 (69%) of the families, including 21 families with mutations in USH2A, 17 in MYO7A, and seven in CLRN1. Our analysis revealed 28 mutations, 11 of which are novel (including c.802G>A, c.8558+1G>T, c.10211del, and c.14023A>T in USH2A; c.285+2T>G, c.2187+1G>T, c.3892G>A, c.5069_5070insC, c.5101C>T, and c.6196C>T in MYO7A; and c.15494del in GPR98).Conclusions:We report here novel homozygous mutations in various genes causing USH, extending the spectrum of causative mutations. We also prove combined sequencing techniques as useful tools to identify novel disease-causing mutations. To the best of our knowledge, this is the largest report of a genetic analysis of Israeli and Palestinian families (n = 74) with different USH subtypes.

What's already known about this topic? ROH mapping is a diagnostic tool in the investigation of genetic disease within consanguineous families; however, in isolated populations, no consanguinity is required as a result of long‐term ancestral isolation. What does this study add? Known founder mutations within isolated populations together with SNP array in the prenatal testing, and with corresponding ultrasound abnormalities assist in achieving an accurate prenatal diagnosis in a tight schedule.

The traditional timing for amniocentesis is between 17-23 weeks of pregnancy. This timing enables decisions related to the pregnancy to be made before viability. Less frequently, third trimester amniocentesis is performed. Advanced genomic technologies introduce far more detailed information about the fetus compared to traditional G-banded chromosomal analysis. Not much is known about the indications, safety and CMA yield of this procedure. We aimed to assess the indications for late amniocentesis, safety, genetic test results (especially chromosomal microarray) and pregnancy outcome. The medical records regarding all late amniocentesis procedures performed at gestational age 24+0 to 38+6 weeks, during the period June 2013 to March 2017, were included. The indications for the procedure, any complications, CMA results and pregnancy outcome were recorded and analysed. 291 women (303 fetuses, 277 singleton pregnancies, 10 twin pregnancies) underwent late amniocentesis during the study period. CMA was performed for all indications. Main indication was abnormal sonographic finding/s (204/303 fetuses, 67%). Preterm delivery rate was 2% and 5.3% within one week and one month from the procedure, respectively. Nine fetuses were diagnosed with aneuploidy (3%) and another nine had a pathogenic copy number variation (3%) suggesting that CMA doubled the diagnostic yield of chromosomal analysis. Maximal diagnostic yield (17.5%) was achieved for the sub-group of fetuses with sonographic findings in two or more organ systems. Variants of uncertain significance and copy number variations of susceptibility loci were found in another 10 (3.3%) fetuses. The increased detection rates and shorter turnaround time of CMA may make late amniocentesis a helpful tool for detecting abnormalities or reassuring parents following late appearing abnormal sonographic findings. However, CMA may also create uncertainties for which the couple should be prepared. The procedure appears to be safe. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Hereditary mixed polyposis syndrome is a rare colon cancer predisposition syndrome caused by a duplication of a noncoding sequence near the gremlin 1, DAN family BMP antagonist gene (GREM1) originally described in Ashkenazi Jews. Few families with GREM1 duplications have been described, so there are many questions about detection and management. We report 4 extended families with the duplication near GREM1 previously found in Ashkenazi Jews; 3 families were identified at cancer genetic clinics in Israel and 1 family was identified in a cohort of patients with familial colorectal cancer. Their clinical features include extracolonic tumors, onset of polyps in adolescence, and rapid progression of some polyps to advanced adenomas. One family met diagnostic criteria for Lynch syndrome. Expansion of the hereditary mixed polyposis syndrome phenotype can inform surveillance strategies for carriers of GREM1 duplications.

Chromosomal microarray (CMA) analysis is effectively applied prenatally to detect copy number changes. SNP probes included on the microarray platform can detect regions of excessive homozygosity (ROH) and identical-by-descent genomic stretches. The utility of the latter in prenatal diagnosis is not well established. Recessive founder mutations have been identified within distinct ethnic groups. Combining these data with prenatal sonography provides accurate molecular diagnoses quickly. Three gravidae presenting with specific fetal sonographic findings: 1) ventriculomegaly with encephalocele; 2) severe polyhydramnion, and 3) enlarged echogenic kidneys, underwent amniocentesis for CMA, and Genome-Wide Human SNP array was used to analyse DNA from amniocytes. The Genomic Oligoarray and SNP array evaluation tool v3.0 was used to detect recessive loci associated with the reported clinical findings. Candidate regions were further interrogated using the National Genetic Database. Three fetuses from three distinct nuclear families in which the parents shared a similar ethnicity (either Ashkenazi or Bukharan Jews) but no reported consanguinity, were assessed. No copy number changes were observed, however evaluation of regions of homozygosity revealed a relevant candidate gene for the specific phenotype for each fetus. Using the National Genetic Database a specific mutation was examined in both parents (c.1167dupA mutation in the FKTN gene, c.167ins6[TTTCCC] mutation in the BSND gene and c.3761_3762delCCinsG in the PKHD1 gene, respectively). Both parents were found to be carriers and the fetuses homozygotes to the mutation. For the first time, specific sonographic pathology, data from ROH extracted from CMA results, and information regarding common founder mutations in distinct ethnic subgroups were combined to create a comprehensive streamlined approach to provide effective genetic diagnosis and counselling within the time constraints of ongoing pregnancy.

Amniocentesis, usually performed at 17–23 weeks' gestation, may be performed in the 3rd trimester on diagnosis of late-onset U/S anomaly. Advanced genomic technologies reveal more detailed information than traditional karyotyping. We aimed to assess indications for late amniocentesis, complication rates, genetic results and pregnancy outcome. The medical records of 185 pregnant women (188 fetuses) who underwent 3rd trimester amniocentesis (28+3–38+3 wks) from 6/2013–3/2016 were reviewed; details of indications, array-CGH results, complications, and pregnancy outcomes were analysed. Genetic testing in all cases was chromosomal microarray analysis (CMA). Indications included late abnormal U/S findings (151 fetuses, 80%), 11 suspected CMV and toxoplasma infections (6%), 4 soft markers (2%) and 5 abnormal biochemical screening (3%). U/S findings included CHD, IUGR, macro/microcephaly, poly/oligohydramnion or a combination. No chorioamnionitis or IUFD were reported. Twenty fetuses (10%) had abnormal results: 6 trisomy 21, 1 trisomy 18; 13 fetuses had copy number changes which could not have been identified using traditional karyotyping, including 15q microdeletion (Prader Willi/ Angelman syndrome), 1q21 microdeletion, 1q41 microdeletion, and Xq23 microduplication. In 4 cases (2%) findings were of unknown significance; one of these was paternally inherited. There were 13 terminations: 5 trisomy 21; 4 “likely pathogenic” CMA result; 1 IUGR with variant of unknown significance; 1 severe polyhydramnios with Bartter syndrome; 1 10-MB deletion on the short arm of chromosome 11; and 1 for worsening cardiovascular findings with normal CMA. To the best of our knowledge this is the largest series to date of late amniocentesis with array-CGH. This approach has an important role in detection of genetic abnormalities, which would not be diagnosed by traditional karyotyping, as well as providing reassurance in cases of late-onset U/S anomalies. Pre-test counselling is key, as results of unknown significance may also create uncertainties, for which the parents should be prepared.

Diagnosis of Lynch syndrome (LS) may be complex. Knowledge of mutation spectrum and founder mutations in specific populations facilitates the diagnostic process. Aim of the study is to describe genetic features of LS in the Israeli population and report novel and founder mutations. Patients were studied at high‐risk clinics. Diagnostics followed a multi‐step process, including tumor testing, gene analysis and testing for founder mutations. LS was defined by positive mutation testing. We diagnosed LS in 242 subjects from 113 families coming from different ethnicities. We identified 54 different mutations; 13 of them are novel. Sixty‐seven (59%) families had mutations in MSH2 , 20 (18%) in MSH6 , 19 (17%) in MLH1 and 7 (6%) in PMS2 ; 27% of the MSH2 mutations were large deletions. Seven founder mutations were detected in 61/113 (54%) families. Constitutional mismatch repair deficiency ( CMMR ‐D) was identified in five families. Gene distribution in the Israeli population is unique, with relatively high incidence of mutations in MSH2 and MSH6 . The mutation spectrum is wide; however, 54% of cases are caused by one of seven founder mutations. CMMR ‐D occurs in the context of founder mutations and consanguinity. These features should guide the diagnostic process, risk estimation, and genetic counseling.

OBJECTIVE:To present the clinical, molecular, and cell biological findings in a family with an autosomal recessive form of hereditary spastic paraplegia characterized by a combination of spastic paraplegia, optic atrophy, and peripheral neuropathy (SPOAN). METHODS:We used a combination of whole-genome linkage analysis and exome sequencing to map the disease locus and to identify the responsible gene. To analyze the physiologic consequences of the disease, we used biochemical and cell biological methods. RESULTS:Ten members of a highly consanguineous family manifested a childhood-onset SPOAN-like phenotype with slow progression into late adulthood. We mapped this disorder to a locus on chromosome 1q and identified a homozygous donor splice-site mutation in the IBA57 gene, previously implicated in 2 infants with lethal perinatal encephalomyopathy. This gene encodes the mitochondrial iron-sulfur (Fe/S) protein assembly factor IBA57. In addition to a severely decreased amount of normal IBA57 messenger RNA, a patient's cells expressed an aberrantly spliced messenger RNA with a premature stop codon. Lymphoblasts contained 10-fold-lower levels of wild-type, but no signs of truncated IBA57 protein. The decrease in functional IBA57 resulted in reduced levels and activities of several mitochondrial [4Fe-4S] proteins, including complexes I and II, while mitochondrial [2Fe-2S] proteins remained normal. CONCLUSIONS:Our findings reinforce the suggested specific function of IBA57 in mitochondrial [4Fe-4S] protein maturation and provide additional evidence for its role in human disease. The less decreased IBA57 protein level in this family explains phenotypic differences compared with the previously described lethal encephalomyopathy with no functional IBA57.

IMPORTANCE We describe a deep intronic mutation in adult polyglucosan body disease. Similar mechanisms can also explain manifesting heterozygous cases in other inborn metabolic diseases.OBJECTIVE To explain the genetic change consistently associated with manifesting heterozygous patients with adult polyglucosan body disease.DESIGN, SETTING, AND PARTICIPANTS This retrospective study took place from November 8, 2012, to November 7, 2014. We studied 35 typical patients with adult polyglucosan body disease, of whom 16 were heterozygous for the well-known c.986A>C mutation in the glycogen branching enzyme gene (GBE1) but harbored no other known mutation in 16 exons.MAIN OUTCOMES AND MEASURES All 16 manifesting heterozygous patients had lower glycogen branching activity compared with homozygous patients, which showed inactivation of the apparently normal allele. We studied the messenger ribonucleic acid (mRNA) structure and the genetic change due to the elusive second mutation.RESULTS When we reverse transcribed and sequenced the mRNA of GBE1, we found that all manifesting heterozygous patients had the c.986A>C mutant mRNA and complete lack of mRNA encoded by the second allele. We identified a deep intronic mutation in this allele, GBE1-IVS15 + 5289_5297delGTGTGGTGGinsTGTTTTTTACATGACAGGT, which acts as a gene trap, creating an ectopic last exon. The mRNA transcript from this allele missed the exon 16 and 3'UTR and encoded abnormal GBE causing further decrease of enzyme activity from 18% to 8%.CONCLUSIONS AND RELEVANCE We identified the deep intronic mutation, which acts as a gene trap. This second-most common adult polyglucosan body disease mutation explains another founder effect in all Ashkenazi-Jewish cases.

OBJECTIVE: Identify the underlying genetic cause of glycogen branching enzyme (GBE) deficiency in manifesting heterozygous patients of adult polyglucosan body disease (APBD). BACKGROUND: APBD is an autosomal recessive leukodystrophy caused by mutations in glycogen branching enzyme (GBE1). It is a late onset variant of glycogen storage disorder type-IV. Most patients are Ashkenazi-Jewish descendants, 70[percnt] of whom have homozygous GBE1 mutations. The remaining 30[percnt] are heterozygous for the p.Y329S mutation. The second mutation was not found until now in those patients in spite of whole-genome sequencing. This had raised the possibility that p.Y329S heterozygous cases were somehow ‘manifesting heterozygotes’. DESIGN/METHODS: We studied 16 APBD patients who are heterozygous for p.Y329S mutation in GBE1 with yet have unlikely low GBE activity with no other known mutation in 16 exons. RESULTS: GBE1 mRNA has been reverse transcribed and sequenced, all manifesting heterozygous patients were homozygous for c.986A>C mutation substituting tyrosine with serine. The mRNA transcript from the other allele was missing the exon 16 and 3’UTR. GBE encoded by this copy was degraded in the cell causing the further decrease of enzyme activity from 18[percnt] to 8[percnt]. Sequencing of polyA tailed mRNA revealed an exon splice site that changes last exon and 3’UTR. CONCLUSIONS: We now identified this deep-intronic mutation, which acts as a gene-trap, creating an ectopic last-exon, 3’UTR and degraded protein. This second-most common APBD mutation now explains all Ashkenazi-Jewish cases and a molecular mechanism for manifesting heterozygosis. Disclosure: Dr. Akman has nothing to disclose. Dr. Kakhlon has nothing to disclose. Dr. Coku has nothing to disclose. Dr. Peverelli has nothing to disclose. Dr. Rosenmann has nothing to disclose. Dr. ROZENSTEIN-TSALKOVICH has nothing to disclose. Dr. Turnbull has nothing to disclose. Dr. MEINER has nothing to disclose. Dr. Chama has nothing to disclose. Dr. Lerer has nothing to disclose. Dr. SHPITZEN has nothing to disclose. Dr. LEITERSDORF has nothing to disclose. Dr. Paradas Lopez has nothing to disclose. Dr. Wallace has nothing to disclose. Dr. Schiffmann has received personal compensation for activities with Amicus Therapeutics and Shire Human Genetic Therapies as a speaker. Dr. DiMauro has received personal compensation in an editorial capacity for MedLink Neurology. Dr. Lossos has nothing to disclose. Dr. Minassian has nothing to disclose.

Background Heterozygous germline mutations in any of the mismatch repair (MMR) genes, MLH1, MSH2, MSH6, and PMS2, cause Lynch syndrome (LS), an autosomal dominant cancer predisposition syndrome conferring a high risk of colorectal, endometrial, and other cancers in adulthood. Offspring of couples where both spouses have LS have a 1:4 risk of inheriting biallelic MMR gene mutations. These cause constitutional MMR deficiency (CMMRD) syndrome, a severe recessively inherited cancer syndrome with a broad tumor spectrum including mainly hematological malignancies, brain tumors, and colon cancer in childhood and adolescence. Many CMMRD children also present with café au lait spots and axillary freckling mimicking neurofibromatosis type 1. Procedure We describe our experience in seven CMMRD families demonstrating the role and importance of founder mutations and consanguinity on its prevalence. Clinical presentations included brain tumors, colon cancer, lymphoma, and small bowel cancer. Results In children from two nonconsanguineous Ashkenazi Jewish (AJ) families, the common Ashkenazi founder mutations were detected; these were homozygous in one family and compound heterozygous in the other. In four consanguineous families of various ancestries, different homozygous mutations were identified. In a nonconsanguineous Caucasus/AJ family, lack of PMS2 was demonstrated in tumor and normal tissues; however, mutations were not identified. Conclusions CMMRD is rare, but, especially in areas where founder mutations for LS and consanguinity are common, pediatricians should be aware of it since they are the first to encounter these children. Early diagnosis will enable tailored cancer surveillance in the entire family and a discussion regarding prenatal genetic diagnosis.

Amniocentesis is a conventional tool for obtaining fetal genetic information. The traditional timing for amniocentesis is between 17–23 week, allowing sufficient time for decisions related to pregnancy continuation before viability. Third trimester amniocentesis can be performed in cases of late presentation of abnormal sonographic findings. Genomic technologies provide far more detailed information about the fetus compared to traditional karyotyping. We aimed to assess the indications for late amniocentesis, complications, genetic results and decision making process of couples undergoing such procedures. The medical records and pregnancy and newborn outcomes of 67 pregnant women who underwent third trimester amniocentesis from June 2013–September 2014 were analysed. 67 women (68 fetuses) underwent late (28 + 3 till 38 + 3 weeks) amniocentesis and chromosomal microarray analysis (CMA). Main indications included newly-appearing abnormal sonographic findings (51 pregnancies, 76%), 5 suspected CMV infections (7%), 2 cases with soft markers (3%) and 2 cases with abnormal biochemical screening (3%). Complications included 4 (6%) preterm deliveries; no cases of chorioamnionitis or IUFD were reported. 54 women (78%) had normal CMA results; 14 fetuses (20%) had abnormal CMA result: 6 had trisomy 21; 8 had copy number changes which could not have been identified using traditional karyotyping (including 15q (Prader Willi/Angelman syndrome), 1q21 microdeletion syndrome, 1q41 microdeletion syndrome and Xq23 microduplication). In 2 cases (3%) the significance of the finding was unknown (VOUS), one of which was paternally inherited from a healthy parent. Late amniocenteses is safe, but poses challenges for physicians and patients. CMA's higher detection and shorter turnaround time make late amniocentesis in the era of genomic technology a helpful tool for detecting abnormalities and reassuring parents when late appearing sonographic findings are encountered, yet may create uncertainties for which the couple should be prepared through comprehensive pre-test counselling.

Retinoblastoma (Rb) is a childhood tumor (~1 in 20,000 live births) developing in the retina due to mutations in the RB1 gene. Identification of the oncogenic mutations in the RB1 gene is important for the clinical management and for genetic counseling to families with a child or a parent affected with the tumor. Here we present our experience in detecting the pathogenic mutations in blood samples, from 150 unrelated Rb patients and highlight the relevant counseling issues. Mutation screening in the RB1 gene was based on Sanger sequencing, mosaicism of recurrent CpG transition mutations was detected by allele specific PCR and multiplex ligation dependent probe amplification for detecting of large deletions/duplications. The overall detection rate of mutations in our cohort was 55 % (82/150). In the familial cases it was 100 % (17/17), in bilateral and unilateral-multifocal sporadic cases 91 % (50/55), and in the unilateral sporadic cases 19 % (15/78). Nonsense mutations and small deletions or insertions that results in transcripts with premature termination codons that are subject to nonsense mediated decay were the most frequent, detected in 50/82 (61 %) of the patients. The rest were large deletions detected in 14/82 (17 %), splice site mutations detected in 11/82 (13 %), missense mutations in four patients and mutations in the promoter sequence in three patients. Mutation mosaicism ranging from 10 to 30 % was detected by allele specific PCR in ten patients, 9 % (5/55) of patients with bilateral tumor and 33 % (5/15) of the patients with unilateral tumor. In three patients rare variants were detected as the only finding which was also detected in other healthy family members. Allele specific amplification of recurrent mutations raises in our cohort the identification rate from 82 to 91 % in the sporadic bilateral cases and from 13 to 19 % in the unilateral sporadic cases. Most mosaic cases could not be identified by Sanger sequencing and therefore screening for recurrent CpG transition mutations by allele specific amplification is of utmost importance. Molecular screening is important for the genetic counseling regarding the risk for tumor development and the relevance for prenatal diagnosis but in several families is accompanied by detecting rare variants that might be rare polymorphisms or low penetrant mutations.

Autosomal recessive polycystic kidney disease (ARPKD) is usually detected late in pregnancies in embryos with large echogenic kidneys accompanied by oligohydramnios. Hundreds of private pathogenic variants have been identified in the large PKHD1 gene in various populations. Yet, because of the large size of the gene, segregation analysis of microsatellite polymorphic markers residing in the PKDH1 locus has commonly been utilized for prenatal diagnosis. Keeping in mind the limitations of this strategy, we utilized it for testing 7 families with affected fetuses or newborns, of which in 5 at least one parent was Ashkenazi, and identified that the same haplotype was shared by the majority of the Ashkenazi parents (7/9). This led us to suspect that they carry the same founder mutation. Whole Exome analysis of DNA from a fetus of one of the families detected an already known pathogenic variant c.3761_3762delCCinsG, an indel variant resulting in frameshift (p.Ala1254GlyfsX49). This variant was detected in 9 parents (5 families), of them 7 individuals were Ashkenazi and one Moroccan Jew who shared the same haplotype, and one Ashkenazi, who carried the same variant on a recombinant haplotype. Screening for this variant in 364 Ashkenazi individuals detected 2 carriers. These findings suggest that although c.3761_3762delCCinsG is considered one of the frequent variants detected in unrelated individuals, and was thought to have occurred independently on various haplotypes, it is in fact a founder mutation in the Ashkenazi population.

Pelizaeus-Merzbacher disease is an X-linked hypomyelinating leukodystrophy caused by mutations or rearrangements in PLP1. It presents in infancy with nystagmus, jerky head movements, hypotonia and developmental delay evolving into spastic tetraplegia with optic atrophy and variable movement disorders. A clinically similar phenotype caused by recessive mutations in GJC2 is known as Pelizaeus-Merzbacher-like disease. Both genes encode proteins associated with myelin. We describe three siblings of a consanguineous family manifesting the typical infantile-onset Pelizaeus-Merzbacher disease-like phenotype slowly evolving into a form of complicated hereditary spastic paraplegia with mental retardation, dysarthria, optic atrophy and peripheral neuropathy in adulthood. Magnetic resonance imaging and spectroscopy were consistent with a demyelinating leukodystrophy. Using genetic linkage and exome sequencing, we identified a homozygous missense c.399C>G; p.S133R mutation in MAG. This gene, previously associated with hereditary spastic paraplegia, encodes myelin-associated glycoprotein, which is involved in myelin maintenance and glia-axon interaction. This mutation is predicted to destabilize the protein and affect its tertiary structure. Examination of the sural nerve biopsy sample obtained in childhood in the oldest sibling revealed complete absence of myelin-associated glycoprotein accompanied by ill-formed onion-bulb structures and a relatively thin myelin sheath of the affected axons. Immunofluorescence, cell surface labelling, biochemical analysis and mass spectrometry-based proteomics studies in a variety of cell types demonstrated a devastating effect of the mutation on post-translational processing, steady state expression and subcellular localization of myelin-associated glycoprotein. In contrast to the wild-type protein, the p.S133R mutant was retained in the endoplasmic reticulum and was subjected to endoplasmic reticulum-associated protein degradation by the proteasome. Our findings identify involvement of myelin-associated glycoprotein in this family with a disorder affecting the central and peripheral nervous system, and suggest that loss of the protein function is responsible for the unique clinical phenotype.

We describe two pairs of siblings from a consanguineous family manifesting autosomal recessive hereditary spastic paraplegia caused by a novel mutation in the EXOSC3 gene, previously reported in pontocerebellar hypoplasia type 1. Clinical findings included delayed motor milestones, early-onset spastic paraplegia, variable cognitive disability, and cerebellar signs. Cerebral imaging demonstrated enlarged cisterna magna and mild hypoplasia and atrophy of the lower vermis with a normal pons. Genetic analysis using homozygosity mapping followed by whole exome sequencing identified homozygous c.571G > T; p.G191C mutation in the EXOSC3 gene. We suggest that EXOSC3 mutations may present not only as pontocerebellar hypoplasia type 1, but also as a complicated form of hereditary spastic paraplegia without pontine hypoplasia or atrophy.

Lynch Syndrome is caused by mutations in DNA mismatch repair genes. Diagnosis is not always trivial and may be costly. Information regarding incidence, genotype-phenotype correlation, spectrum of mutations and genes involved in specific populations facilitate the diagnostic process and contribute to clinical work-up. To report gene distribution, mutations detected and co-occurrence of related syndromes in a cohort of Ashkenazi Jews in Israel. Patients were identified in dedicated high risk clinics in 3 medical centers in Israel. Diagnostic process followed a multi-step scheme. It included testing for founder mutations, tumor testing, gene sequencing and MLPA. Lynch Syndrome was defined either by positive mutation testing, or by clinical criteria and positive tumor analysis. We report a cohort of 75 Ashkenazi families suspected of Lynch Syndrome. Mutations were identified in 51/75 (68 %) families: 38 in MSH2 , 9 in MSH6 , and 4 in MLH1 . 37/51 (73 %) of these families carried one of the 3 ‘Ashkenazi’ founder mutations in MSH2 or MSH6 . Each of the other 14 families carried a private mutation. 3 (6 %) were large deletions. Only 20/51 (39 %) families were Amsterdam Criteria positive; 42 (82 %) were positive for the Bethesda guidelines and 9 (18 %) did not fulfill any Lynch Syndrome criteria. We report C-MMRD and co-occurrence of BRCA and Lynch Syndrome in our cohort. Mutation spectra and gene distribution among Ashkenazi Jews are unique. Three founder Lynch Syndrome mutations are found in 73 % families with known mutations. Among the three, MSH2 and MSH6 are the most common. These features affect the phenotype, the diagnostic process, risk estimation, and genetic counseling.

The estimated incidence of radiation-associated sarcoma (RAS) is 0.03–0.2 % in 5 years post treatment. Most cancer predisposing genes are involved in DNA repair; therefore, elevated RAS risk in these patients is plausible. Cases of angiosarcoma post breast cancer treatment were reported in BRCA1 and BRCA2 carriers. We report the genetic evaluation of seven cases with suspected RAS from patients counseled in our cancer-genetic clinic. Of 2,885 breast cancer patient, 470 were BRCA1 or two mutation carriers and three were p53 mutation carriers. Of them seven developed sarcoma in the field of irradiation; five in the chest wall and two in other sites. Genetic evaluation revealed BRCA1 mutation in two, BRCA2 mutation in additional patient and a carrier of p53 mutation. The estimation of risk for RAS in patients with genetic predisposition is limited due to the rarity of this event, and the bias in referral to the clinic toward younger age. With these limitations the rate of RAS is 0.43 % (2/470, 95 % CI −0.17 to 1.02, SE = 0.3) in this group in a median follow-up of 8.2 years (range 1 month to 51 years). If we assume irradiation for the breast in 80 % of the patients than rate of RAS in group is proximately 0.53 % (2/376, 95 % CI −0.21 to 1.26, SE = 0.37). A BRCA1 carrier which had sarcoma after irradiation to head and neck carcinoma was not included in these analyses. In conclusion, we found a high frequency of BRCA1/2 mutation among our patients diagnosed with RAS. However, we estimated approximately twofold increase in the risk of RAS in BRCA1/2 carriers which was not significant compared to reports in general population. Therefore, RAS is a rare event in BRCA carriers as in the general population, and should not be considered in the decision regarding irradiation treatment in this population.