Ethnic effect on FMR1 carrier rate and AGG repeat interruptions among Ashkenazi women

PURPOSE

Fragile X syndrome, a common cause of intellectual disability, is usually caused by CGG trinucleotide expansion in the FMR1 gene. CGG repeat size correlates with expansion risk. Premutation alleles (55-200 repeats) may expand to full mutations in female meiosis. Interspersed AGG repeats decrease allele instability and expansion risk. The carrier rate and stability of FMR1 alleles were evaluated in large cohorts of Ashkenazi and non-Ashkenazi women.

METHODS

A total of 4,344 Ashkenazi and 4,985 non-Ashkenazi cases were analyzed using Southern blotting and polymerase chain reaction between 2004 and 2011. In addition, AGG interruptions were evaluated in 326 Ashkenazi and 298 non-Ashkenazi women who were recruited during 2011.

RESULTS

Both groups had major peaks of 30 and 29 repeats. Ashkenazi women had a higher frequency of 30 repeats and a lower frequency of other peaks (P < 0.0001). A higher rate of premutations in the 55-59 repeats range (1:114 vs. 1:277) was detected among the Ashkenazi women. Loss of AGG interruptions (<2) was significantly less common among Ashkenazi women (9 vs. 19.5% for non-Ashkenazi women, P = 0.0002).

CONCLUSION

Ashkenazi women have a high fragile X syndrome carrier rate and mostly lower-range premutations, and carry a low risk for expansion to a full mutation. Normal-sized alleles in Ashkenazi women have higher average number of AGG interruptions that may increase stability. These factors may decrease the risk for fragile X syndrome offspring among Ashkenazi women.

Predictive value of TP53 fluorescence in situ hybridization in cytogenetic subgroups of acute myeloid leukemia

Acute myeloid leukemia (AML) with a complex karyotype (CK) has frequent alterations in TP53 and a very poor prognosis. We examined whether a prompt and simple fluorescence in situ hybridization (FISH) analysis for 17p13 deletion at diagnosis has a predictive value for response to therapy and overall survival in subgroups of AML. In 15 patients with a normal karyotype the TP53 FISH analysis was normal, whereas in 16 patients with CK 75% had only one copy of the TP53 allele. The deletion was also detected in 33% of six patients with monosomy or partial monosomy of chromosome 5, 7, 9, or 12. This loss of TP53 correlated significantly with a poor response to chemotherapy, and the median survival time of these patients was shorter. TP53 FISH analysis carried out at diagnosis has a predictive value with respect to chemotherapy response and can therefore facilitate a rapid decision on treatment strategies.

Clinical and genetic heterogeneity of congenital adrenal hypoplasia due to NR0B1 gene mutations

INTRODUCTION

X-linked adrenal hypoplasia congenita (AHC) is a rare disorder caused by mutations or complete deletion of the NR0B1 gene that encodes the DAX-1 protein, an orphan member of the nuclear receptor superfamily. AHC is characterized by adrenal insufficiency in infancy and early childhood. Later, hypogonadotropic hypogonadism (HH) manifests as pubertal failure.

PATIENTS AND METHODS

We evaluated the clinical, endocrine and molecular characteristics of 12 AHC patients from 5 families diagnosed between 1984 and 2007 in Israel.

RESULTS

Most of the boys (10/12) presented with signs of adrenal insufficiency such as salt wasting and failure to thrive during the neonatal period. Aldosterone deficiency usually preceded cortisol deficiency requiring early mineralocorticoid therapy. Serum cortisol levels in the first weeks of life varied from very low to high levels (<2.76 to >1776 nmol/l). Five boys showed signs of precocious sexual development during infancy and childhood, including enlargement of the penis and testes. In four patients the initial diagnoses were erroneous. Molecular analysis of the NR0B1 gene identified point mutations in six patients including a novel splice site mutation in one patient and his family (IVS1-1G-->C). Contiguous gene deletion was found in six patients from two families who manifested impaired mental development.

CONCLUSIONS

In X-linked AHC caused by different molecular defects in NR0B1 gene, the clinical spectrum of the disease is quite variable and precocious sexual development is a prominent feature. Genetic testing is indicated in boys presenting with salt-wasting with or without cortisol deficiency if congenital adrenal hyperplasia has been ruled out.

Cytogenetic analysis of sinonasal carcinomas

BACKGROUND

Sinonasal carcinomas, including nonkeratinizing (NK) squamous cell carcinoma (SCC) and sinonasal undifferentiated carcinoma (SNUC), are uncommon malignant neoplasms arising from the Schneiderian respiratory epithelium of the nasal cavity and paranasal sinuses. Due to their low frequency, the cytogenetic data on these tumors is limited.

METHODS

Seventeen patients who were operated on in our institution for extirpation of paranasal carcinomas were enrolled in this study. Fourteen pathologically confirmed samples of sinonasal carcinomas were cytogenetically analyzed using G-banding techniques after short-term culture. Three samples did not grow on culture.

RESULTS

Five of the 14 sinonasal carcinomas had an abnormal karyotype (36%). Of the 9 NK SCCs, 3 had abnormal karyotypes with numerical and structural chromosomal anomalies. Of the 5 patients with SNUC, 2 had an abnormal karyotype. One case of SNUC had a diploid complex karyotype. Another case of SNUC had a near triploid composite karyotype with 60-69 chromosomes. The chromosome arms that involved frequent breakpoint and rearrangements were: 1p, 6p, 7p, and 12q. We found that 3 of the 3 patients who died of disease displayed an abnormal karyotype, whereas 2 of the 11 patients who are alive displayed an abnormal karyotype (P = 0.027).

CONCLUSIONS

The study revealed that more than a third of the paranasal carcinomas carry an abnormal karyotype. No specific common aberrations were found in these tumors. To our knowledge this is the first attempt to investigate sinonasal squamous and undifferentiated carcinomas on a genetic level using G-banding technique. Additional studies are required in order to determine whether cytogenetic data may serve as an adjunct to conventional pathology for the diagnosis and prognosis assessment of these rare and highly aggressive tumors.

Multiplex nested PCR for preimplantation genetic diagnosis of spinal muscular atrophy

OBJECTIVE

Spinal muscular atrophy (SMA) is a common autosomal recessive neuromuscular disorder caused in most patients by homozygous deletion of the SMN1 gene. For a carrier couple at a 25% risk of affected offspring, preimplantation genetic diagnosis (PGD) offers an alternative to prenatal diagnosis and termination of affected pregnancies. Our objective was to develop an accurate and reliable single-cell multiplex nested PCR analysis for PGD of SMA.

METHODS

The method was developed on single blood leukocytes, obtained from healthy controls and an adult SMA type III patient with a known homozygous deletion of SMN1 exon 7 and 8. Multiplex nested PCR on single cells was used to co-amplify exons 7 and 8 of SMN. Additional multiplexing was performed with the ZFX/ZFY gene for sexing. Following successful establishment of the multiplex nested PCR protocol in single leukocytes, the technique was employed for PGD in 4 patients for a total of 7 cycles. In 2 patients, sexing was simultaneously performed using ZFX/ZFY.

RESULTS

220 single leukocytes from a normal individual and 220 from an SMA patient were analyzed. Exon 7 of SMN1 was amplified in 99% of normal single leukocytes and in none of the SMA-affected leukocytes. Exon 7 of SMN2 was amplified in 100% of both normal and SMA-affected leukocytes. Exon 8 of SMN1 was amplified in 98% of normal cells and in none of the SMA-affected leukocytes. Exon 8 of SMN2 was amplified in 96% of both normal and SMA-affected leukocytes. Amplification efficiency was 99% for ZFX/ZFY. There were no false-negative results and no contamination was detected in all wash-drop blanks tested. Seven PGD cycles were performed in 4 SMA-carrier couples with successful molecular analysis of 34 embryos and a total of 15 normal embryos transferred in 7 cycles. One clinical pregnancy has resulted in the delivery of a healthy male. Amniocentesis performed at 17 weeks confirmed the correct diagnosis for both SMA and sexing.

CONCLUSIONS

These results suggest that our multiplex nested PCR protocol offers an efficient and accurate method for PGD of SMA while enabling the simultaneous analysis of an additional loci.

Screening for familial dysautonomia in Israel: evidence for higher carrier rate among Polish Ashkenazi Jews

Familial dysautonomia (FD) is an autosomal recessive disorder characterized by hereditary sensory and autonomic neuropathies. Although extremely rare in most populations, FD is common among Ashkenazi Jews (AJ), with a calculated carrier frequency of 1 in 30, based on disease prevalence. The gene for FD was recently identified as IKBKAP. One major mutation (IVS2 + 6T --> C) is responsible in >99.5% of cases among AJ. The purpose of this study was to determine the actual frequency of FD carriers in the AJ population in Israel and to determine whether carriers are more frequent among a subpopulation of AJ from Poland. The study group included 1267 Jews of Ashkenazi origin who were referred for routine DNA screening tests. These included 1100 individuals who were full AJ and 167 who were part AJ. None had a family history of FD. Mutation analysis for (IVS2 + 6T --> C) was performed by PCR amplification followed by restriction enzyme analysis. All positive cases were confirmed by DHPLC WAVE( trade mark ). Among the 1100 full AJ tested, 34 were found to be FD carriers (1:32). The incidence of mutation carriers was significantly higher in AJ of Polish descent (1:18) compared to AJ of non-Polish descent (1:99). Among the 167 individuals who were part AJ, there were 3 carriers (1:56). The incidence of FD among AJ, particularly those of Polish background, warrants population screening. Population screening may be performed by denaturing high-performance liquid chromatography.

Familial adenomatous polyposis at the Tel Aviv Medical Center: demographic and clinical features

Familial adenomatous polyposis (FAP) is an uncommon, but widespread genetic disorder that develops multiple colonic adenomatous polyps and, if untreated, can lead to large bowel cancer. Little is known about its occurrence and characteristics in the Israeli population.

AIMS

To evaluate FAP prevalence, phenotypic manifestations and compliance for diagnosis and follow-up in our registry.

METHODS

Since 1993 approximately one-half of FAP patients in Israel have been seen and followed-up by us before and/or after colectomy. They and their families were encouraged to have mutation analysis, genetic and/or endoscopic screening.

RESULTS

37 pedigrees were identified, including 2 non-Jewish. The Jewish ethnic distribution was similar to that of the general population and the point prevalence rate estimated as 28.4/one million Jewish inhabitants. There were 461 first-degree relatives at-risk for FAP. Genetic screening was completed and successful in 28 pedigrees (87.5%), and 73 FAP patients entered the registry. Marked intra- familial phenotypic variations with minimal disease manifestation were noted in 11 patients belonging to 4 pedigrees. Cancer occurred in 15.1% (11 patients), in 10 before FAP diagnosis or during follow- up elsewhere, but one non-compliant patient developed duodenal cancer. One other patient died from a massive, neglected, intra- abdominal desmoid. Compliance for evaluation and follow-up of pedigree members and individual FAP patients was inadequate in 29% and 27%, respectively.

CONCLUSIONS

FAP occurs in the Israeli Jewish population at the expected rate, but is inadequately recognized in non-Jews. The inadequate compliance for screening and post-surgical follow-up needs to be addressed by educating the public, health care workers and Health Insurers.

MECP2 mutations in Israel: implications for molecular analysis, genetic counseling, and prenatal diagnosis in Rett syndrome

This report describes molecular analysis of the MECP2 gene in 37 Israeli patients suspected of having Rett syndrome (RTT). The patients were from various Jewish ethnic groups and from Arabic origin. Of the 17 patients with classical RTT, bi-directional sequencing of the coding exons revealed MECP2 mutations in 14 patients. About 66% of the mutations were located in previously described hot-spots. One case presented a novel mutation (141insA). Mutation-negative patients were further analyzed by Southern blot, which detected a novel gross rearrangement in another classical case. Altogether, detection rate in classical cases was 88%. In a non-classical case, a novel missense mutation (1451G>C) was detected in an affected girl and in her normal father, suggesting that this is a non-pathogenic alteration. Another variant (1461 + 96insA) was detected in an affected girl and in her healthy mother and also in another affected girl and her healthy father, suggesting that this variant too, is non-pathogenic. No significant difference in mutation type was noted among the different ethnic groups. In one familial case, the same mutation was detected in two sibs but not in their mother, suggesting germ-line mosaicism. Our results suggest that mutation-negative cases should be further assessed for gross rearrangements and that molecular analysis of the parents is often required when previously undescribed sequence alterations are detected.

Adrenal hypoplasia congenita with multiple pituitary hormone deficiency without documented mutation in DAX1 or SF1 gene

A boy with adrenal hypoplasia congenita (AHC) and multiple pituitary hormone deficiency (MPHD), without mutations in the DAX1 or SF1 genes, is described. The association of AHC and MPHD has not been previously reported.

Molecular analysis of the APC gene in 71 Israeli families: 17 novel mutations

Familial adenomatous polyposis (FAP) is caused by germline mutations in the APC gene. This study included 71 Israeli families referred for molecular analysis of the APC gene. Analysis was performed by the protein truncation test (PTT) of exon 15, and if negative, by direct sequencing of exon 1 to 14. Mutations were found in 36 (50.7%) probands. Mutation detection rates depended on the pattern of referral, such that among the 40 probands referred from the Service for Hereditary Cancer the mutation detection rate was 70%, whereas among the 31 probands referred by other gastroenterologists detection rate was significantly lower (25.8%). Of the 36 mutations detected, 21 were within exon 15, 13 within exons 1 to 14 and 2 were newly-described splicing mutations in introns 9 and 14. A relatively high proportion of the mutations was detected in exon 9 (6/36), five of them newly described. Altogether, we describe here 17 new mutations. Within the two major ethnic groups in Israel, patients of Ashkenazi and non-Ashkenazi origin, there was no significant differences in the mutation detection rate or the distribution of mutations within the APC gene. No founder mutation was detected in any of these populations. Our data confirm that higher detection rates may be expected in patients referred by clinical services specializing in hereditary colon cancer. These results further underscore the importance of complete analysis of all exons and exon/intron boundaries, in order to achieve maximal detection rate in patients suspected of FAP.

Clinical and screening implications of the I1307K adenomatous polyposis coli gene variant in Israeli Ashkenazi Jews with familial colorectal neoplasia. Evidence for a founder effect

BACKGROUND

The authors previously found the I1307K adenomatous polyposis coli (APC) gene variant in 5% of Ashkenazi control participants, in 15.4% of those who had familial colorectal neoplasia, but also in 1.6% of non-Ashkenazi control participants. In this study, they evaluated its use in a screening program for familial colorectal neoplasia and examined for a founder effect.

METHODS

Consecutive Ashkenazim with a personal and/or family history of colorectal neoplasia had the DNA test. Markers flanking the APC gene were examined in Ashkenazi and non-Ashkenazi I1307K carriers and noncarriers.

RESULTS

Among 718 persons, I1307K occurred in 6.2% of Ashkenazi participants, in 1.5% of non-Ashkenazi control participants (P = 0.02), and in 10.7% of Ashkenazim with familial neoplasia (relative risk, 1.73 [not significant compared with controls]; 95% confidence interval, 0.7-3.2). Colorectal neoplasia was detected in carriers at a younger age (P < 0.05) without excess risk for multiple colorectal neoplasia or noncolorectal neoplasia. I1307K attributable risk for colorectal neoplasia was 0.5-0.6%. Compared with noncarriers, both Ashkenazi and non-Ashkenazi I1307K carriers had similar flanking polymorphic alleles (P < 0.01).

CONCLUSIONS

I1307K is a low-penetrance genetic variant that indicates a 1.7 relative risk for neoplasia in carriers who have familial carcinoma, clinically equivalent to obtaining a family history of sporadic colorectal neoplasia and promoting early screening. I1307K is a founder genetic variant in Jews of different ethnic origin, mainly Ashkenazim, but it explains only partially their higher incidence of colorectal carcinoma.

Rett syndrome: clinical manifestations in males with MECP2 mutations

Rett syndrome is a neurodevelopmental disorder characterized by cognitive and adaptive regression with autistic features, loss of acquired skills, and stereotypic hand movements that almost exclusively affects females. It is an X-linked dominant disorder, with presumed lethality in males. Nonetheless, there are a few descriptions of males suspected of having Rett syndrome. With the recent discovery that the MECP2 gene is responsible for most cases of Rett syndrome, it is possible to molecularly assess cases of affected males by direct sequencing analysis. We describe an Israeli family consisting of a female having classic Rett syndrome and a male sibling with severe neonatal encephalopathy. Molecular analysis revealed that both sister and brother have the same MECP2 gene mutation; however, their mother does not. This case, as well as other published studies of males with MECP2 mutations, reveals that the clinical manifestations in viable males vary from neonates with severe encephalopathy to adults with mental retardation and demonstrate genotype-phenotype correlations.

Novel mutations in the emerin gene in Israeli families

Emery-Dreifuss Muscular Dystrophy (EMD or EDMD) is a rare X-linked recessive disorder, characterized by progressive muscle wasting and weakness, contractures, and cardiomyopathy, manifesting as heart block. Mutation analysis at the EMD gene locus was performed in 4 unrelated Israeli families with X-linked EMD and in one sporadic case. In the 4 families 4 different mutations were found, 3 of which were novel. These included two frame shift mutations in exon 2 (333delT and 412insA) and one base pair substitution at the consensus +1 donor splice in intron 5 (1429G-->A). The fourth mutation in exon 6 (1675-1678delTCCG) has been previously described. No mutations were identified in the one sporadic case. Two of the three novel mutations were found in exon 2. A summary of the previously published mutations described in the EMD Mutation Database (http://www.path.cam.ac.uk/emd/) as well as the mutations described in our study suggest that the distribution of mutations in EMD gene is not entirely random and that exon 2 is prone to mutations. Hum Mutat 17:522, 2001.

The risk of fragile X premutation expansion is lower in carriers detected by general prenatal screening than in carriers from known fragile X families

The Fragile X syndrome is the most common cause of inherited mental retardation. For a female premutation carrier, the risk of having a child with a full mutation is positively correlated with the size of the premutation. The current study was performed to evaluate the risk of premutation expansion in the offspring of average-risk carriers detected by general prenatal screening. Over a 4-year period, 9,660 women underwent DNA screening for FMR1 mutation/premutation at the Tel Aviv Sourasky Medical Center. A premutation was defined as a CGG repeat number >50 in the 5' untranslated region (UTR) of exon 1 in the FMR1 gene. The study included only individuals with no family history of X-linked mental retardation or known FMR1 mutations. A premutation was found in 85 women (1 in 114), 68 of whom consented to have prenatal diagnoses in 74 pregnancies. The abnormal allele was transmitted to the offspring in 44 pregnancies. Of these, no change in allele size was noted in 35 pregnancies (79.6%), and expansion within premutation range was evident in 4 pregnancies (9%). In 5 pregnancies (11.4%), expansion to the full mutation was noted. This occurred only in carriers having more than 90 repeats. We conclude that the likelihood of Fragile X premutation expansion to full mutation is significantly lower in individuals ascertained by general prenatal carrier testing than in those from known Fragile X families.

Prevalence of glucocerebrosidase mutations in the Israeli Ashkenazi Jewish population

Gaucher disease is the most prevalent inherited disease among Ashkenazi Jews. It is very heterogeneous due to a large number of mutations within the glucocerebrosidase gene, whose impaired activity is the cause for this disease. Aiming at determining Gaucher carrier frequency among the Ashkenazi Jewish population in Israel, 1,208 individuals were molecularly diagnosed for six mutations known to occur among Ashkenazi Jewish Gaucher patients, using the newly developed Pronto Gaucher kit. The following mutations were tested: N370S, 84GG, IVS2+1, D409H, L444P, and V394L. Molecular testing of these mutations also allows identification of the recTL allele. The results indicated that Gaucher carrier frequency is 1:17 within the tested population. The prevalence of N370S carriers is 1:17.5. This implies that approximately 1:1225 Ashkenazi Jews will be homozygous for the N370S mutation. Actually, in our study of 1,208 individuals one was found to be homozygous for the N370S mutation. The actual number of known Ashkenazi Jewish Gaucher patients with this genotype is much lower than that expected according to the frequency of the N370S mutation, suggesting a low penetrance of this mutation. Results of loading experiments in cells homozygous for the N370S mutation, as well as cells homozygous for the L444P and the D409H mutations, exemplified this phenomenon.

Notable intrafamilial phenotypic variability in a kindred with familial adenomatous polyposis and an APC mutation in exon 9

BACKGROUND

The phenotypic spectrum of familial adenomatous polyposis (FAP) varies from the classic appearance of hundreds of adenomatous colonic polyps in the young adult and early onset colorectal cancer, to the occurrence of sparse adenomas in the older adult, "attenuated" FAP, due to mutations at the 5' or 3' ends of the APC gene.

AIMS

To investigate marked intrafamilial phenotypic variation occurring in a family with an APC gene mutation in exon 9.

PATIENTS

An extended kindred of 22 people of whom 16 had colorectal neoplasia and/or were APC mutation carriers.

RESULTS

Phenotypic manifestation varied from classic FAP to a complete lack of clinical or endoscopic, or bioptic disease in five people in three different generations. This occurred in four of them over two generations, in spite of having a confirmed 11 bp insertion causing a frame shift and stop codon (363) in exon 9 of the APC gene.

CONCLUSIONS

At present, it is assumed that in this family there is alternative splicing of the APC gene, and/or unidentified modifying genetic factors. The family illustrates the importance of genetic testing in evaluating carrier status and not just clinical examination. This clinical observation also high- lights the dilemma in recognising the possible contribution of low penetrance germline APC mutations to what has been considered "sporadic" colorectal neoplasia.

Fetal muscle biopsy as a diagnostic tool in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a relentless progressive disorder, leading to severe disability during childhood and death in adolescence or early adulthood. In most families, prenatal diagnosis is readily achieved by molecular detection of DNA deletions using chorionic villi or amniocytes, or by linkage analysis. In some cases, however, molecular methods fail to provide a definitive diagnosis and in such cases in utero fetal muscle biopsy may serve as a diagnostic option. We describe three families in whom fetal muscle biopsy was performed, focusing on the prenatal diagnostic dilemmas, the indications and timing for in utero fetal muscle biopsy, and the difficulties encountered.

High frequency of a common Bloom syndrome Ashkenazi mutation among Jews of Polish origin

Bloom syndrome (BS) is an autosomal recessive disorder characterized by small stature, immunodeficiency, chromosomal instability, and a predisposition to different types of cancer. Although extremely rare in the general population, BS is seen in about 1 in 48,000 Ashkenazi Jews. Mutation analysis of seven Ashkenazi BS probands has shown that all were homozygous for the same mutation in the BLM gene: 2281delATCTGAinsTAGATTC, also known as blmAsh. This finding, along with the increased incidence of BS among Ashkenazi Jews, suggests a founder effect for BS in this population. The purpose of this study was to determine the frequency of blmAsh mutation carriers in a randomly sampled Ashkenazi Jewish population in Israel. The initial study group included 1,613 Ashkenazi Jews who were referred for routine DNA screening tests (cystic fibrosis, Gaucher, Canavan, fragile X). None had a family history of BS. A group of 552 non-Ashkenazi Jews served as controls. Mutation analysis was performed by PCR amplification followed by analysis of a specific BstN1 restriction site, created by the blmAsh mutation. All positive carriers were confirmed by direct sequencing. Sixteen blmAsh carriers were detected among 1,613 Ashkenazi Jews (1 in 101), compared to none among 552 non-Ashkenazi individuals. In this study, Ashkenazi Jews of biparental Polish descent had a significantly higher proportion of the blmAsh mutation (1 in 37) compared to Ashkenazi Jews of non-Polish descent. These results provide further evidence that a founder effect is responsible for the increased incidence of Bloom syndrome among Ashkenazi Jews, particularly those of Polish descent.

[Muir-Torre syndrome and HNPCC: importance of clinical diagnosis and genetic investigation in family members]

Muir-Torre syndrome is a relatively rare cutaneous manifestation of hereditary nonpolypous colorectal cancer (HNPCC). This autosomal dominant syndrome is characterized by a combination of sebaceous gland and malignant visceral tumors. The common sites of internal malignancies are the gastrointestinal tract and urinary system. It appears in early adult life and its clinical course is relatively slow. In some families genetic diagnosis can identify asymptomatic carriers of the mutation. All first-degree relatives, especially mutation carriers, should be referred from the age of 20 years for routine follow-up and early treatment, as it has been proven to decrease morbidity and mortality. We present a 51-year-old man with Muir-Torre syndrome diagnosed by the presence of multiple adenomas of sebaceous glands, colonic adenoma and adenocarcinoma of the duodenum. The family history was typical for HNPCC. A mutation in the hMSH2 gene on chromosome 2p was found in the patient and in several asymptomatic family members. The aim of this report is to increase awareness of this syndrome and emphasize the importance of referring patients and their families for clinical and genetic counseling and diagnosis.

Prevalence of the I1307K APC gene variant in Israeli Jews of differing ethnic origin and risk for colorectal cancer

BACKGROUND & AIMS

Israeli Jews of European birth, i.e., Ashkenazim, have the highest colorectal cancer incidence of any Israeli ethnic group. The I1307K APC gene variant was found in 6.1% of American Jews, 28% of their familial colorectal cancer cases, but not in non-Jews. We assessed the I1307K prevalence in Israeli Jews of differing ethnic origin and risk for colorectal cancer.

METHODS

DNA samples from 500 unrelated Jews of European or non-European origin, with or without a personal and/or family history of neoplasia, were examined for the I1307K variant by the allele-specific oligonucleotide (ASO) method.

RESULTS

In persons at average risk for colorectal cancer, I1307K was found in 5.0% of 120 European and 1.6% of 188 non-European Jews (P = 0.08). It occurred in 15.4% of 52 Ashkenazi Israelis with familial cancer (P = 0.02) and was not detected in 51 non-European Jews at increased cancer risk. Colorectal neoplasia occurred personally or in the families of 13 of 20 Ashkenazi I1307K carriers, 8 of whom also had a personal or family history of noncolonic neoplasia.

CONCLUSIONS

The I1307K APC variant may represent a susceptibility gene for colorectal, or other, cancers in Ashkenazi Jews, and partially explains the higher incidence of colorectal cancer in European Israelis.

Mutations of the adenomatous polyposis coli and p53 genes in a child with Turcot's syndrome

Turcot's syndrome is a rare heritable complex that is characterized by an association between a primary neuroepithelial tumor of the central nervous system and multiple colonic polyps. The aim of this study was to analyze genetic alterations in a case of Turcot's syndrome in a 10.5-year-old boy in whom a colorectal tumor developed 3.5 years following astrocytoma. An APC germline non-sense mutation at codon 1284 leading to a truncated protein was identified, as was a somatic p53 mutation in the colorectal carcinoma in exon 7, codon 244. The latter was not identified in the primary astrocytoma. However, immunohistochemistry revealed high p53 protein expression in both tumors, suggesting an additional p53 mutation in the primary astrocytic tumor. The diverse p53 mutations observed in this unique syndrome in two different sites and stages of the disease may shed light on the multistep progression of the malignant events.

SMA type 2 unrelated to chromosome 5q13

We describe two brothers with clinical and histological findings of type 2 spinal muscular atrophy (SMA) associated with small head circumference (<2%) and normal cognitive development. No survival motor neuron (SMN) or neuronal apoptosis-inhibitory protein (NAIP) deletions were detected in these sibs, and they were discordant for the haplotypes determined by DNA markers flanking the 5q13 SMA locus. These findings support the presence of a distinct anterior horn disease unrelated to 5q13. This entity may have either autosomal recessive or X-linked inheritance.

[Familial adenomatous polyposis: establishing a registry and genetic and molecular analysis]

Familial adenomatous polyposis (FAP), a dominantly inherited disease, is caused by a mutation in the adenomatous polyposis coli gene in chromosome 5q21. The gene has 15 exons, a physical length of 10 Kb and an open reading frame of 8.5 Kb. Exon 15 codes 66% of the mRNA and has a mutation cluster region which accounts for over 50% of mutations. The disease usually leads to the appearance of hundreds of adenomatous polyps in the transverse and descending colon between puberty and age 20 years and to colon cancer before the age of 40. Early detection is essential to prevent the development of metastasizing cancer. Since 1994 we have recruited 23 families for genetic counseling. DNA was obtained from 19 unrelated FAP patients and 219 high risk relatives in 19 unrelated families following confirmation of the diagnosis. In addition to linkage studies, direct mutational analysis was performed using the protein truncation test for most of exon 15 and single strand conformation polymorphism analysis for the other exons. These exons account for most of the mutations identified to date. Of 19 unrelated probands, 14 had detectable mutations. Exon 15 accounted for 6 families, exons 5, 7 and 14 for 1 each, exon 9 for 3, and exon 8 for 2. Combined mutational and linkage analysis identified 18 presymptomatic carriers who received genetic and clinical counseling. Our FAP patients did not differ significantly from those of larger studies in other countries with regard to the distribution of the mutations, gender and genotype-phenotype correlation, or ethnic distribution.

Duchenne muscular dystrophy and idiopathic hyperCKemia segregating in a family

A 7-month-old boy with gross motor delay and failure to thrive presented with rhabdomyolysis following an acute asthmatic episode. During hospitalization an electrocardiographic conversion to a Wolff-Parkinson-White type 1 (WPW) pattern took place. Duchenne muscular dystrophy (DMD) was suspected based on elevated creatine kinase (CK) serum levels, muscle biopsy, and family history. The diagnosis was confirmed by molecular analysis, which documented a deletion corresponding to cDNA probe 1-2a in the dystrophin gene, in the propositus and in an affected male cousin of his mother. "Idiopathic" hyperCKemia was found in the propositus, his father, and 5 of his relatives. We suggest that the unusually early and severe manifestations of DMD in this patient may be related to the coincidental inheritance of the maternal DMD gene and of a paternal gene, causing hyperCKemia.

Relatively low proportion of dystrophin gene deletions in Israeli Duchenne and Becker muscular dystrophy patients

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are allelic disorders caused by mutations in the X-linked dystrophin gene. The most common mutations in western populations are deletions that are spread non-randomly throughout the gene. Molecular analysis of the dystrophin gene structure by hybridization of the full length cDNA to Southern blots and by PCR in 62 unrelated Israeli male DMD/BMD patients showed deletions in 23 (37%). This proportion is significantly lower than that found in European and North American populations (55-65%). Seventy-eight percent of the deletions were confined to exons 44-52, half of these to exons 44-45, and the remaining 22% to exons 1 and 19. There was no correlation between the size of the deletion and the severity of the disease. All the deletions causing frameshift resulted in the DMD phenotypes.

A molecular survey of Israeli Duchenne and Becker muscular dystrophy patients

Duchenne (DMD) and Becker (BMD) muscular dystrophy are allelic X-linked recessive diseases caused by a mutation in the dystrophin gene located on the short arm of chromosome X (Xp21). The dystrophin gene is the largest gene known in humans, extending over 2300 kb and containing more than 70 exons coding for a 420 KD protein comprising 3685 amino acids. The gene is highly unstable, with a high percentage of deletions and rearrangements. A third of dystrophin mutations are new mutations. The frequency of DMD is 1:3500 liveborn males, and that of BMD 1:10000. These dystrophies are severe, progressive, and lethal. BMD/DMD patients and 2/3 of female carriers have high levels of creatine phosphokinase (CK). During the past 5 years, 169 families with patients affected by progressive muscular dystrophy were examined and counselled. We were able to exclude the diagnosis of DMD/BMD in 49 families on the basis of clinical symptoms and signs, normal dystrophin on biopsy (11 families) and/or the absence of linkage to chromosome X by analysis of RFLP derived haplotypes. Molecular analysis was performed on 111 DMD/BMD families (five BMD and 106 DMD) with 81 available probands. This study resulted in the establishment in Israel of an integrated diagnostic protocol for DMD/BMD, employing genetic, biochemical and molecular techniques. Molecular analysis provided most of the families with new and essential information.

Detection of Duchenne muscular dystrophy gene products in amniotic fluid and chorionic villus sampling cells

We have examined the expression of several Duchenne muscular dystrophy (DMD) gene products in amniotic fluid (AF) and chorionic villus sampling (CVS) cells. Variable amounts of dystrophin could be detected in most CVS and AF samples by immunoprecipitation followed by Western blot analysis. PCR analysis demonstrated the presence of the muscle type dystrophin mRNA in all AF cell cultures. The brain type dystrophin mRNA was also detected in some of these cultures. These DMD gene transcripts are of fetal origin and are produced by most or all clonable AF cells. The results may facilitate the development of a method for prenatal diagnosis of DMD, based on the expression of the gene in AF and CVS cells.

Use of dystrophin genomic and cDNA probes for solving difficulties in carrier detection and prenatal diagnosis of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) results from mutations in the X-linked gene coding for the muscular protein dystrophin. The isolation of genomic and cDNA probes for this gene has greatly facilitated the detection of DMD carriers, which previously relied mainly on measurements of serum creatine kinase (CK), and has enabled prenatal diagnosis of this disease. However, the relatively large size of the gene and the high frequency of recombination and mutation events within the dystrophin locus continue to pose difficulties in the genetic counselling and prenatal diagnosis of DMD, and render the conclusions of molecular analysis less clear cut. This communication presents examples of two such difficulties: the distinction between sporadic and inherited cases in families with a single patient and normal CK levels in all females, and the distinction between mutant and normal dystrophin alleles in families in which the patients have died. The combined use of genomic and cDNA probes allows one to make these distinctions. An additional complicating factor, gonadal mosaicism, is demonstrated.

Early pregnancy screening for neural tube defects in Israel

A pilot project to detect neural tube defects (NTD) of the fetus by maternal serum alpha-fetoprotein (MSAFP) screening of women in early pregnancy was initiated in Tel Aviv in 1982 at the instigation of the Israel Ministry of Health. The program was designed to be an extension of routine pregnancy care, which in this city is provided in municipal family clinics that are attended by about 50% of pregnant women before the 20th week of pregnancy. Of these women, 89% complied with the program. Women with a MSAFP level above a cutoff point of 2.4 multiples of the median (MOM) were invited for an ultrasound examination of the fetus, without having to repeat the MSAFP test, thereby reducing maternal anxiety. This deviation from the usual test system protocol did not impair sensitivity (87%), or specificity of the test on its own (95.6%), or in combination with ultrasound examination of the fetus and alpha-fetoprotein and acetylcholinesterase testing of the amniotic fluid (99.9%). The program detected 13 fetuses with an NTD; there were two false-negative results and one false-positive. The predictive value of a positive test was 93%. Its effectiveness as a preventive measure was impaired by the fact that 50% of pregnant women did not attend the family clinic before the 20th gestational week. An educational program for professionals and for the public is contemplated in order to reduce this proportion. Only 50% of normal twin pregnancies had an elevated MSAFP. A check on compliance with other screening systems during the interview for MSAFP screening led to the detection and elective abortion of two fetuses with Tay-Sachs disease. MSAFP screening in Israel is cost-effective rather than cost-beneficial.

Diminished capping of lymphocytes from pregnant women

The capping of lymphocytes from normal pregnant women is diminished. Decreased capping is observed for both anti-Ig and for Con A receptors. The altered capping response appears between the tenth and the twelfth week of pregnancy. The diminution in capping persists until about 2 weeks after delivery. The possible association between the decreased capping response and the altered immune responses known to occur during pregnancy is discussed. The factors underlying the altered capping response in pregnancy may be related to the factors responsible for the parallel phenomenon in pathological conditions.

Dynamic changes of red cell membrane thiol groups followed by bimane fluorescent labeling

Monobromobimane labels red cell membrane protein thiol groups; bands exhibit fluorescence after sodium dodecyl sulfate acrylamide gel electrophoresis and correspond to almost all of those staining with Coomassie blue. The response of membrane protein thiol groups to oxidative challenge and the dynamics of recovery of the thiol groups may be followed. Diminished labeling is found after oxidation with diamide, with both intrachain and interchain disulfide bond formation demonstrated by sodium dodecyl sulfate acrylamide gel electrophoresis. Regeneration of thiol groups under physiological conditions (incubation with glucose) after a moderate degree of diamide oxidation is shown to be complete (with respect to thiol group content and degree and distribution of bimane label) in normal human red blood cell membranes. Even after oxidation of almost half of the membrane protein thio groups (maximum degree of oxidation achieved), regeneration of thiol groups is almost complete; a minor fraction resides in the form of disulfide-linked high molecular weight proteins (demonstrated by the electrophoretic profile) which may be reduced completely with dithiothreitol. Bimane fluorescent labeling provides a convenient and sensitive method for following membrane thiol group status under physiological conditions.

Ultrastructure of the conjunctiva, skin, and gingiva: a case of Sandhoff's disease in a Jewish patient

Pleomorphic membranous cytoplasmic bodies that indicated glycolipid storage were found in the conjunctiva, skin, and gingiva of a Jewish patient with Sandhoff's disease. The clinical symptoms were typical of GM2 gangliosidosis. Both hexosaminidase A and hexosaminidase B activities were deficient in the leukocytes and serum. Glycosaminoglycan levels in cultured fibroblasts were elevated. Membranous cytoplasmic bodies were observed in high concentrations in a large proportion of the vascular endothelial cells, pericytes, and Schwann cells and to a somewhat lesser extent in the fibrocytes of all tissues studied. Ultrastructural analysis of the conjunctiva, skin, and gingiva as an aid for the diagnosis of Sandhoff's disease is suggested.