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L C Brody

Publications and source records attributed to L C Brody.

At least 37 records · Page 2Linked to original sources
PubMed1998

The APCI1307K allele and cancer risk in a community-based study of Ashkenazi Jews.

Mutations in APC are classically associated with familial adenomatous polyposis (FAP), a highly penetrant autosomal dominant disorder characterized by multiple intestinal polyps and, without surgical intervention, the development of colorectal cancer (CRC). APC is a tumour-suppressor gene, and somatic loss occurs in tumours. The germline T-to-A transversion responsible for the APC I1307K allele converts the wild-type sequence to a homopolymer tract (A8) that is genetically unstable and prone to somatic mutation. The I1307K allele was found in 6.1% of unselected Ashkenazi Jews and higher proportions of Ashkenazim with family or personal histories of CRC (ref. 2). To evaluate the role of I1307K in cancer, we genotyped 5,081 Ashkenazi volunteers in a community survey. Risk of developing colorectal, breast and other cancers were compared between genotyped I1307K carriers and non-carriers and their first-degree relatives.

Adenomatous Polyposis Coli Protein↗
PubMed1998

Evolutionary sequence comparisons using high-density oligonucleotide arrays.

We explored the utility of high-density oligonucleotide arrays (DNA chips) for obtaining sequence information from homologous genes in closely related species. Orthologues of the human BRCA1 exon 11, all approximately 3.4 kb in length and ranging from 98.2% to 83.5% nucleotide identity, were subjected to hybridization-based and conventional dideoxysequencing analysis. Retrospective guidelines for identifying high-fidelity hybridization-based sequence calls were formulated based upon dideoxysequencing results. Prospective application of these rules yielded base-calling with at least 98.8% accuracy over orthologous sequence tracts shown to have approximately 99% identity. For higher primate sequences with greater than 97% nucleotide identity, base-calling was made with at least 99.91% accuracy covering a minimum of 97% of the sequence. Using a second-tier confirmatory hybridization chip strategy, shown in several cases to confirm the identity of predicted sequence changes, the complete sequence of the chimpanzee, gorilla and orangutan orthologues should be deducible solely through hybridization-based methodologies. Analysis of less highly conserved orthologues can still identify conserved nucleotide tracts of at least 15 nucleotides and can provide useful information for designing primers. DNA-chip based assays can be a valuable new technology for obtaining high-throughput cost-effective sequence information from related genomes.

Alouatta↗
PubMed1998

Applications of DNA chips for genomic analysis.

A major frontier in medical genetics is the definition of the molecular basis of multifactorial diseases. This is especially relevant in the field of clinical psychiatry where the majority of common disorders display complex inheritance patterns, and are further influenced by environmental interactions. New technologies are needed to help address the pressing needs for discovering and deciphering the nature of such disease-associated genes. One such technology which has emerged within the past 3 years involves hybridization-based nucleic acid array (DNA chip) analysis. This technology has the potential to have a lasting impact on diverse genomic-based applications such as large-scale gene mapping studies, mutational analysis, and global expression level monitoring of all human genes. In this review we will describe the fundamental principles behind nucleic acid array-based assays, while focusing on their applications towards genome-wide DNA and RNA analysis. The current capabilities and limitations of these technologies will be discussed, with a focus on areas where future development will be needed for DNA chip-based assays to achieve their full potential.

Chromosome Mapping↗
PubMed1998

Breast cancer susceptibility genes. BRCA1 and BRCA2.

Mutations in the BRCA1 and BRCA2 genes lead to an increased susceptibility to breast, ovarian, and other cancers. It is estimated that 3%-8% of all women with breast cancer will be found to carry a mutation in 1 of these genes. Families with multiple affected first-degree relatives and patients with early-onset disease have been found to harbor mutations at a higher frequency. The BRCA1 and BRCA2 genes code for large proteins that bear no resemblance to other known genes. In the cell, they appear to act as tumor suppressor genes and play a role in the maintenance of genome integrity, although the precise function of these genes has yet to be discovered. A large number of distinct mutations have been found in cancer families around the world. The majority of the defined pathologic mutations result in premature truncation of the protein (frameshift and nonsense mutations). These mutations may substantially increase the risk for breast and ovarian cancer, but a precise risk estimate for each different mutation cannot be determined. Depending on the familial context, the risk of breast cancer associated with carrying a mutation has been estimated to range from 50% to 85%. The role of these genes in sporadic cancer remains unknown. Patients and physicians considering BRCA1 and BRCA2 genetic testing are faced with a difficult decision. The diversity of mutations and lack of general population data prevent accurate risk prediction. This is further complicated by the paucity of data on effective prevention strategies for those identified at higher risk. Thus, the nature of clinical testing for BRCA1 and BRCA2 continues to present challenges that reinforce the necessity of personal choice within the context of thorough genetic counseling.

Aged↗
PubMed1998

New approaches to BRCA1 mutation detection.

The development of technologies to identify quickly, efficiently, and inexpensively all possible heterozygous mutations and sequence variants in patient samples will play a crucial role in the future of medical genetics. In addition to the continued refinement of more established mutation detection protocols, several innovative methodologies recently have emerged with the potential to increase sample throughput as well as decrease the cost of mutational analysis. The allelic heterogeneity of BRCA1 mutations serves as an example of the considerable technical challenge in developing diagnostic tests for all possible sequence variants in large genes. We describe recent advances in methologies that have previously been or could be readily adapted for use in BRCA1 mutation detection. Special emphasis is placed on the use of high density oligonucleotide arrays (DNA chips) as tools for detecting sequence variations in BRCA1.

Journal Article↗
PubMed1997

Breast cancer: the high-risk mutations.

Mutations in the two known BRCA genes account for only 5% to 10% of breast cancer. The genes may play a role in genomic stability; their role in sporadic cancer remains unknown. Hence, genetic testing has created clinical dilemmas. Some pertain to women whose family history suggests inherited risk. Others, including the false reassurance that may be conferred by a negative finding, apply throughout the general population.

BRCA1 Protein↗
PubMed1997

Defects in auxiliary redox proteins lead to functional methionine synthase deficiency.

Methionine synthase catalyzes a methyl transfer reaction from methyltetrahydrofolate to homocysteine to form methionine and tetrahydrofolate and is dependent on methylcobalamin, a derivative of vitamin B12, for activity. Due to the lability of the intermediate, cob(I)alamin, the activity of methionine synthase is additionally dependent on a redox activation system. In bacteria, two flavoproteins, NADPH-flavodoxin reductase and flavodoxin, shuttle electrons from NADPH to methionine synthase. Their mammalian counterparts are unknown, and a putative intrinsic thiol oxidase activity of the mammalian methionine synthase has been proposed to be involved. We demonstrate that the mammalian methionine synthase can be activated in an NADPH-dependent reaction and requires a minimum of two redox proteins. This model is consistent with our results from biochemical complementation studies between cblG and cblE cell lines and mutation detection analysis in cblG cell lines. These demonstrate that the cblG cell line has defects affecting methionine synthase directly, whereas the cblE cell line has defects in the redox proteins. We have also identified a P1173L mutation in the activation domain of methionine synthase in the cblG cell line WG1505.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1997

Human BRCA1 inhibits growth in yeast: potential use in diagnostic testing.

Germline-inactivating mutations of BRCA1 result in a hereditary predisposition to breast and ovarian cancer. Truncating mutations of BRCA1 predispose to cancer and can be ascertained by protein truncation testing or sequencing. However, cancer-predisposing missense mutations of BRCA1 are difficult to distinguish from polymorphisms by genetic testing methods currently used. Here we show that expression of BRCA1 or BRCA1 fused to a GAL4 activation domain in Saccharomyces cerevesiae inhibits growth, resulting in small colonies easily distinguishable from vector-transformed controls. The growth inhibitory effect can be localized to sequences encoding the recently described BRCA1 C-terminal domains. Growth suppression by a BRCA1 fusion protein is not influenced by introduction of neutral polymorphisms but is diminished or abolished by frameshift, nonsense, or disease-associated missense mutations located in the C-terminal 305 amino acids of BRCA1. These observations may permit the functional significance of many BRCA1 sequence changes to be assessed in yeast. Additionally, the correlation of growth suppression with wild-type forms of BRCA1 suggests that the assay may be capable of detecting functionally conserved interactions between the evolutionarily conserved BRCA1 C-terminal domains and cellular elements found in both human and yeast cells.

BRCA1 Protein↗
PubMed1997

The risk of cancer associated with specific mutations of BRCA1 and BRCA2 among Ashkenazi Jews.

BACKGROUND: Carriers of germ-line mutations in BRCA1 and BRCA2 from families at high risk for cancer have been estimated to have an 85 percent risk of breast cancer. Since the combined frequency of BRCA1 and BRCA2 mutations exceeds 2 percent among Ashkenazi Jews, we were able to estimate the risk of cancer in a large group of Jewish men and women from the Washington, D.C., area. METHODS: We collected blood samples from 5318 Jewish subjects who had filled out epidemiologic questionnaires. Carriers of the 185delAG and 5382insC mutations in BRCA1 and the 6174delT mutation in BRCA2 were identified with assays based on the polymerase chain reaction. We estimated the risks of breast and other cancers by comparing the cancer histories of relatives of carriers of the mutations and noncarriers. RESULTS: One hundred twenty carriers of a BRCA1 or BRCA2 mutation were identified. By the age of 70, the estimated risk of breast cancer among carriers was 56 percent (95 percent confidence interval, 40 to 73 percent); of ovarian cancer, 16 percent (95 percent confidence interval, 6 to 28 percent); and of prostate cancer, 16 percent (95 percent confidence interval, 4 to 30 percent). There were no significant differences in the risk of breast cancer between carriers of BRCA1 mutations and carriers of BRCA2 mutations, and the incidence of colon cancer among the relatives of carriers was not elevated. CONCLUSIONS: Over 2 percent of Ashkenazi Jews carry mutations in BRCA1 or BRCA2 that confer increased risks of breast, ovarian, and prostate cancer. The risks of breast cancer may be overestimated, but they fall well below previous estimates based on subjects from high-risk families.

Adult↗
PubMed1997

Genetic susceptibility testing for breast and ovarian cancer: a progress report.

The recent identification of genes that predispose their carriers to breast and ovarian cancer promises to shed light on the biology of cancer susceptibility. Individuals with mutations in the BRCA1 gene on chromosome 17 and the BRCA2 gene on chromosome 13 have four to eight times the risk of developing breast cancer as women in the general population. The many mutations that have been identified in both genes are predicted to produce a truncated, presumably nonfunctional, protein. Individuals of Ashkenazi Jewish decent have been found to carry specific BRCA1 and BRCA2 mutations. The sequences of BRCA1 and BRCA2 are not similar to any other previously cloned genes. Investigations are underway to elucidate the biological function of these genes. In the meantime, these genes offer the opportunity for members of high incidence cancer families to decide whether to undergo predisposition testing. There is a paucity of data to guide physicians in making follow-up recommendations to those who are found to be carrying a mutation. Thus, decisions about testing are personal and demand pretest education and counseling about the risks, benefits, and limitations. Further research into testing decisions and their outcome is greatly needed.

Breast Neoplasms↗
PubMed1996

Characterization of EZH1, a human homolog of Drosophila Enhancer of zeste near BRCA1.

Recent transcription mapping efforts within chromosome 17q21 have led to the identification of a human homolog of the Drosophila gene Enhancer of zeste, E(z). A member of the Polycomb group (Pc-G) of proteins, Drosophila E(z) acts as a negative regulator of the segment identity genes of the Antennapedia and Bithorax complexes. Here we report the full-length protein coding sequence of human EZH1 (Enhancer of zeste homolog 1) and compare the respective protein sequences in both species. EZH1 encodes a protein of 747 amino acids that displays 55% amino acid identity overall (70% similarity) with Drosophila E(z). The strongest homology was noted (79% identity, 89% similarity) within the carboxy-terminal 245 amino acids, including the SET domain, a region of E(z) also conserved in other Drosophila proteins with roles in development and/or chromatin structure. A large Cysrich region with a novel spatial pattern of cysteine residues was also conserved in both EZH1 and E(z). The strong sequence conservation suggest potential roles for EZH1 in human development as a transcriptional regulator and as a component of protein complexes that stably maintain heterochromatin. EZH1 is expressed as two major transcripts in all adult and fetal human tissues surveyed; comparison of cloned cDNAs suggests that alternative splicing may account for at least part of the transcript size difference. Analysis of one cDNA revealed an unusual splicing event involving EZH1 and a tandemly linked gene GPR2 and suggests a potential mechanism for modifying the EZH1 protein in the conserved C-terminal domain. The sequence and isolated cDNAs will provide useful reagents for determining the function of EZH1 and the importance of the evolutionarily conserved domains.

Adult↗
PubMed1996

A 500-kb physical map and contig from the Harvey ras-1 gene to the 11p telomere.

A contiguous physical map was constructed from the Harvey ras-1 (HRAS1) gene to the 11p telomere. The contig spans approximately 500 kb and is minimally composed of a telomere-containing YAC and P1 and cosmid clones. Included in the contig are 11 sequence-tagged sites derived from P1 and cosmid ends. Three genes were placed on the contig in the following order: telomere-ribonuclease/angiogenin inhibitor (RNH)-Harvey ras-1 (HRAS1)-HRAS1-related complex (HRC). Two novel tetranucleotide repeats (heterozygosity of 66 and 68%) and a complex CA repeat (heterozygosity of 78%) were isolated and characterized.

Base Sequence↗
PubMed1996

Chromosomal localization of 15 ion channel genes.

Several human Mendelian diseases, including the long-QT syndrome, malignant hyperthermia, and episodic ataxia/myokymia syndrome, have recently been demonstrated to be due to mutations in ion channel genes. Systematic mapping of ion channel genes may therefore reveal candidates for other heritable disorders. In this study, the GenBank and dbEST databases were used to identify members of several ion channel families (voltage-gated calcium and sodium, cardiac chloride, and all classes of potassium channels). Genes and ESTs without prior map localization were identified based on GDB and OWL database information and 15 genes and ESTs were selected for mapping. Of these 15, only the serotonin receptor 5HT3R had been previously mapped to a chromosome. A somatic cell hybrid panel (SCH) was screened with an STS from each gene and, if necessary the results verified by a second SCH panel. For three ESTs, rodent derived PCR products of the same size as the human STS precluded SCH mapping. For these three, human P1 clones were isolated and the genomic location was determined by metaphase FISH. These genes and ESTs can now be further evaluated as candidate genes for inherited cardiac, neuromuscular and psychiatric disorders mapped to these chromosomes. Furthermore, the ESTs developed in this study can be used to isolate genomic clones, enabling the determination of each transcript's genomic structure and physical map location. This approach may also be applicable to other gene families and may aid in the identification of candidate genes for groups of related heritable disorders.

Animals↗
PubMed1996

The carrier frequency of the BRCA2 6174delT mutation among Ashkenazi Jewish individuals is approximately 1%.

Certain germline mutations in either BRCA1 or BRCA2 confer a lifetime risk of developing breast cancer that may approach 90%. The BRCA1 185delAG mutation was found in 20% and the BRCA2 6174delT mutation in 8% of Ashkenazi Jewish women with early-onset breast cancer. The 185delAG mutation was observed in 0.9% of 858 Ashkenazi Jews unselected for a personal or family history of cancer. Assuming comparable age-specific penetrances, a carrier frequency of 0.3% was estimated for the 6174delT BRCA2 mutation. To test this hypothesis, we performed a population survey of 1,255 Jewish individuals. In two independent groups, a prevalence of approximately 1% (C.I. 0.6-1.5) was observed for the 6174delT mutation. The relative risk of developing breast cancer by age 42 was estimated to be 9.3 (C.I. 2.5-22.5) for 6174delT, compared to 31 (C.I. 11-77) for 185delAG. Analysis of 107 Ashkenazi Jewish women with breast cancer and a family history of breast or ovarian cancer confirmed a four-fold greater prevalence for the BRCA1 185delAG mutation compared to the BRCA2 6174delT mutation. Our findings suggest a difference in cumulative life-time penetrance for the two mutations. Genetic counseling for the one in 50 Ashkenazi Jewish individuals harbouring specific germline mutations in BRCA1 or BRCA2 must be tailored to reflect the different risks associated with the two mutations.

Adult↗
PubMed1996

Detection of heterozygous mutations in BRCA1 using high density oligonucleotide arrays and two-colour fluorescence analysis.

The ability to scan a large gene rapidly and accurately for all possible heterozygous mutations in large numbers of patient samples will be critical for the future of medicine. We have designed high-density arrays consisting of over 96,600 oligonucleotides 20-nucleotides (nt) in length to screen for a wide range of heterozygous mutations in the 3.45-kilobases (kb) exon 11 of the hereditary breast and ovarian cancer gene BRCA1. Reference and test samples were co-hybridized to these arrays and differences in hybridization patterns quantitated by two-colour analysis. Fourteen of fifteen patient samples with known mutations were accurately diagnosed, and no false positive mutations were identified in 20 control samples. Eight single nucleotide polymorphisms were also readily detected. DNA chip-based assays may provide a valuable new technology for high-throughput cost-efficient detection of genetic alterations.

BRCA1 Protein↗
PubMed1996

Cloning, mapping and RNA analysis of the human methionine synthase gene.

Elevated levels of plasma homocysteine is a risk factor in both birth defects and vascular disease. Methionine synthase (MS) is a cobalamin dependent enzyme which catalyzes methylation of homocysteine to methionine. Impaired MS activity is expected to lead to increased levels of plasma homocysteine. In addition, defects in this gene may underlie the methionine-dependence observed in a number of human tumor cell lines. We describe here the isolation and characterization of the human MS cDNA. It contains an open reading frame of 3798 nucleotides encoding a protein of 1265 amino acids with a predicted molecular mass of 140 kDa. The amino acid sequence of the human MS is 55% identical with that of the Escherichia coli enzyme (METH) and 64% identical with the predicted Caenorhabditis elegans enzyme. Seven peptide sequences derived from purified porcine MS have substantial similarity to the human protein. Northern analysis indicates that the MS RNA is present in a wide variety of tissues. We have mapped the human gene to chromosomal location 1q43, a region found monosomic in individuals with deletion 1q syndrome. The isolation of the MS cDNA will now allow the direct determination of whether mutations in this gene contribute to folate-related neural tube defects, cardiovascular diseases, and birth defects.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗