Dinucleotide repeat polymorphisms of RAD51, BRCA1, BRCA2 gene regions in breast cancer

Recent studies suggest that genetic polymorphisms of the DNA repair genes have been implicated in breast cancer risk. BRCA1 and BRCA2 , two breast cancer susceptibility genes, are essential to maintain chromosomal integrity. This is mediated via regulation of RAD51 during homologous recombination. Dinucleotide polymorphism repeats in the 15q14–21, 17q21 and 13q12–13 regions, where the RAD51 , BRCA1 and BRCA2 genes are located, respectively, have been evaluated. The polymorphism was determined using the following microsatellite markers: D15S118, D15S214, D15S1006, D17S855, D17S1323, D13S260 and D13S290. Genotypes containing the (CA)₁₇ or (CA)₁₉ alleles in the RAD51 region were found to be associated with a decreased breast cancer risk. Genotype containing the (CA)₁₇ allele in the 13q12–13 region was found to be associated with an increased breast cancer risk. The results indicate that dinucleotide CA repeat polymorphism at RAD51 and BRCA2 gene regions might be associated with genetic susceptibility to breast cancer.     

German family study on hereditary breast and/or ovarian cancer: Germline mutation analysis of the BRCA1 gene

Women harboring BRCA1 germline mutations carry an 85% lifetime risk of developing breast cancer and a 63% risk of ovarian cancer. In this first systematic study of familial breast and/or ovarian cancer in Germany we investigated 29 families for germline mutations in the BRCA1 gene. We identified mutations in three breast cancer families and in four breast-ovarian cancer families. The mutations include one missense mutation, one frameshift mutation, one splice mutation, and four nonsense mutations cosegregating with breast and/or ovarian susceptibility in five of ten (50%) families showing positive evidence of linkage to chromosome band 17q21 and in two of 19 (11%) families where linkage data was not available. Two apparently unrelated families carried the same nonsense mutation at codon 1835 and three families harbored a C to T transition at nucleotide 49 of the untranslated exon 4. Allelotyping of the markers D17S855, D17S1322, D17S1323, and D17S1327 located within or near BRCA1 revealed that all affected individuals in the two families harboring the mutation at codon 1835 shared at least one allele indicating a founder mutation. With respect to the overall mutation spectrum, no mutations were identified in exon 11 (0/7) in this set of German families. These findings differed significant from those in British (17/32)(P = 0.012) and Southern Swedish (13/15) (P < 0.001) families. The lack of BRCA1 mutations in exon 11 which represents 61% of the entire coding sequence may provide additional insight into BRCA1 associated breast and ovarian tumor development. Genes Chromosom. Cancer 18:126–132, 1997. © 1997 Wiley-Liss, Inc.     

中国早发性乳腺癌患者中BRCA1基因突变分析

目的研究中国早发性乳腺癌患者中BRCA1基因致病性突变的发生情况以及家族史在突变携带者识别中的作用。方法研究对象为来自中国4个乳腺癌临床医疗中心的188例早发性乳腺癌病例(发病年龄≤40岁),其中39例(20.1%)有乳腺/卵巢癌家族史。从外周静脉血提取基因组DNA,对BRCA1基因的全部编码区和外显子/内含子拼接区进行PCR扩增。其中22例通过单链构象多态方法进行突变初筛,166例用变性高效液相色谱分析进行初筛;对发现的异常片段通过DNA直接测序的方法进行确认。对发现重复出现突变的样本,选取5个与BRCA1基因连锁的标记(D17S855、D17S1322、D17S1323、D17S1326和D17S1327)进行等位基因型分析。结果在15例(8.0%)患者中发现有12个BRCA1基因的致病性突变,其中BRCA11100delAT和5589del8突变分别在3个和2个患者中发现。在39例同时伴有乳腺/卵巢癌家族史的病例中共发现有9例(23.1%)携带突变。有(无)乳腺癌家族史的早发性乳腺癌病例间BRCA1基因的突变率的差异有统计学意义(P=0.001)。重复出现的突变在所有检测病例中出现的频率为2.7%,在所有检测到的突变中占33.3%。两个来自中国北方的BRCA11100delAT突变携带病例有相同的等位基因型,而与来自上海地区的此突变携带者的等位基因型在D17S1322位点上有所差异。两例5589del8突变携带者在所检测的5个STR位点上有完全相同的等位基因型。结论这是到目前为止较大规模的关于中国早发性乳腺癌人群的BRCA1基因突变的研究,有助于增加对中国早发性乳腺癌人群中BRCA1基因致病性突变分布的全面认识。在中国早发性乳腺癌人群中,BRCA1基因致病性突变在肿瘤的发生中有比较重要的意义,尤其在伴有乳腺/卵巢癌家族史病例中该基因突变的意义尤为突出。两个重复出现的突变可能在中国人群中有始祖效应,在进行全基因检测前对其先进行检测可能非常合算。     

Founder mutation in the BRCA1 gene in Malay breast cancer patients from Singapore

The mutation spectrum of the BRCA1 gene among ethnic groups from Asia has not been well studied. We investigated the frequency of mutations in the BRCA1 gene among Malay breast cancer patients from Singapore, independent of family history. By using the protein truncation test (PTT) and direct sequencing, BRCA1 mutations were detected in 6 of 49 (12.2%) unrelated patients. Four novel missense mutations in exon 11, T557A (1788A>G), T582A (1863A>G), N656S (2086A>G) and P684S (2169C>T) were identified in one patient. Two patients had missense mutations in exon 23, V1809A (5545T>C), which has been previously detected in individuals from Central and Eastern Europe. Three unrelated patients had the deleterious 2846insA frameshift mutation in exon 11. Methylation specific PCR (MSP) of the promoter region of the BRCA1 gene detected hypermethylation of tumor DNA in an additional 2 patients. Haplotype analysis using the microsatellite markers D17S855, D17S1323 and D17S1325 revealed a common haplotype for the three unrelated patients and their three relatives with the 2846insA mutation. These findings strongly suggest that the 2846insA mutation, the most common deleterious mutation in this study, may possibly be a founder mutation in breast cancer patients of Malay ethnic background.     

Patterns of allelic loss at the BRCA1 locus in Arabic women with breast cancer

Loss of heterozygosity (LOH) of BRCA1, a tumor suppressor gene, is one mechanism of genetic inactivation in both sporadic and familial forms of breast cancer. Studies reported in breast cancers from women of Northern European descent have shown LOH in 30-50% of sporadic tumors. Microsatellite instability (MSI) has served as evidence for involvement of DNA repair genes. This study investigates the extent of allelic imbalance at the BRCA1 region in Arabic women with breast cancer. Paired normal and tumor tissue were available for DNA analysis in 13 cases. Results using fluorescent tagged primers to microsatellite markers D17S1323, D17S1325 and D17S855 intragenic to BRCA1 were analyzed using an ABI 310 DNA sequencer. As compared to normal DNA, MSI and LOH were recognized as a gain and a loss, respectively, of one signal in one allele in the tumor DNA. Microsatellite analyses showed 12 of 13 (92%) cases with LOH or MSI or both. Three cases demonstrated LOH alone, 3 cases with MSI alone. Six cases indicated both LOH and MSI; 2 cases with either LOH or MSI in separate markers. The combined finding of LOH and MSI in the same marker was detected only with D17S1325 in 4/6 cases. The proportion of aberrant findings of the BRCA1 locus in breast cancer appears to be higher in Arabic women than in other populations studied to date.     

Genetic analysis of the BRCA1 region in a large breast/ovarian family: refinement of the minimal region containing BRCA1

We have analyzed a single multi-affected breast/ovarian cancerpedigree (BOV3) and have shown consistent inheritance of markerson chromosome 17q with the disease confirming that this familyis due to the BRCA1 gene. Analysis of 17q hapiotypes shows arecombination event in a bilateral breast cancer case whichsuggests that the BRCA1 gene lies distal to D17S857; D17S857is thus the new proximal boundary for the region containingBRCA1. Combining this information with previously publishedmapping information suggests that BRCA1 is contained in a regionestimated at 1 – 1 .5 Mb in length. All seven breast tumour/bloodpairs examined from this family show loss of heterozygosityin the tumours. The allele retained in each tumour was fromthe disease-bearing chromosome implicating BRCA1 as a tumoursuppressor gene. We have sequenced the 17ß-oestradioldehydrogenase genes (EDH17B1 and EDH17B2) which have been suggestedas candidate genes for BRCA1 in four members of this family.No germline mutations were detected.     

Over-representation of two specific haplotypes among chromosomes harbouring BRCA1 mutations

The BRCA1 gene is included in a 200-400 kb region that is subjected to a recombination suppression mechanism; this region shows nearly complete linkage disequilibrium for a series of common biallelic polymorphisms, all of them with rarer allele frequency close to 0.4. These series of SNPs define two major haplotypes designated as class I and class II. In the present study, we have determined haplotype classes in the index case of 106 breast/ovarian cancer families previously screened for mutations in the BRCA genes and we have found that haplotype II (the less frequent in the control population) is over-represented among chromosomes harbouring mutations in BRCA1. In addition, we have defined a subtype of chromosomes characterized by haplotype I and one specific allele for the microsatellite marker D17S855, which are also more frequently associated with BRCA1 mutations. These findings may have important consequences for the selection of families with higher probabilities of carrying mutations in the BRCA1 gene.     

Comparison of BRCA1 polymorphisms, rare sequence variants and/or missense mutations in unaffected and breast/ovarian cancer populations

Inherited mutations in the BRCA1 gene are known to confer a predisposition to breast and ovarian cancer. We have first characterized 19 sequence variants in the BRCA1 gene during mutation screening by direct sequencing using DNA samples from breast/ovarian cancer patients or obligate carriers. The frequencies of these sequence variants were then compared with those found in control populations of women. Among the 10 sequence variants showing an estimated frequency of the less common allele above 0.05, Q/R356, L/P871, E/G1038, K/R1183 and S/G1613 result in a change of amino acids, 2201C/T, 2430T/C and 4427C/T are silent mutations and the two others, 4209-141C/A and 5272 + 66A/G, are intronic polymorphisms. These frequent polymorphisms, with the exception of Q/R356, were in complete or significant pairwise linkage disequilibrium as evaluated in our control populations. With one exception (L/P871), none of these variants had statistically significant (P < 0.05) differences in allele frequency between breast/ovarian cancer patients or obligate carriers and our control populations. Four rare sequence variants designated 710C-->T, D693N, R841W and S1040N were found in both unaffected and breast/ovarian cancer populations, while the missense mutations M1008I, E1219D, R1347G, T1561I and M1628V were detected only once in our patient population. When a functional test is available, it will be important to determine the consequence on the BRCA1 activity of these rare sequence variants and missense mutations.      

Association of interferon-γ and interferon regulatory factor 1 polymorphisms with asthma in a family-based association study in Taiwan

BACKGROUND: Asthma is a multi-factorial disorder caused by complex interactions between genetic and environmental factors. IFN-gamma and IFN regulatory factor 1 (IRF-1) affect Th1/Th2 cytokine balance, and influence the differentiation of Th2 cells, which influence the development of asthma. OBJECTIVE: This study investigated CA repeats polymorphism of the IFN-gamma gene and GT repeats polymorphism of the IRF-1 gene, which may predispose individuals to asthma pathogenesis. METHODS: In the present study, we used the transmission/disequilibrium test (TDT) to investigate the relationship between asthma and the IFN-gamma and IRF-1 polymorphisms by studying 348 subjects composed of 232 parents and 116 asthmatic children. RESULTS: For global TDT test, IFN-gamma CA repeats and IRF-1 GT repeat polymorphisms showed a significant association with asthma in children (P=0.009 and 0.017, respectively). We demonstrated that 13 CA repeats (138 bp) of IFN-gamma gene and 11 GT repeats (306 bp) of IRF-1 gene are significantly preferentially transmitted to asthmatic children (T/NT=89/61, chi2=8.43, P<0.005 and T/NT=75/49, chi2=8.18, P<0.005, respectively). The offspring will have an increased risk of asthma when their parents transmit IFN-gamma 13 CA repeats (OR=1.83, P=0.009) and IRF1 11 GT repeats (OR=1.88, P=0.007) to them. But we observed that the IFN-gamma and IRF-1 polymorphisms are not associated with IgE concentrations. CONCLUSION: These findings provide strong evidence of which IFN-gamma CA repeat and IRF-1 GT repeat polymorphisms influence the risk of asthma for children in Taiwan.     

The serotonin 5-HT1D receptor gene and attention-deficit hyperactivity disorder in Chinese Han subjects.

Attention-deficit/hyperactivity disorder (ADHD) is a heritable disease. Serotonin is one of the neurotransmitters involved in the etiology of ADHD. Serotonin-1D receptors are autoreceptors which can regulate the release of serotonin in brain, so the HTR1D gene may be predisposing. The current study genotyped two variants of HTR1D gene in 272 ADHD trios of Chinese ethnicity, that is 1350T > C in the coding region and 1236A > G in 3'-UTR by the use of transmission disequilibrium test (TDT). The A allele of the 1236A > G polymorphism exhibited both a trend toward preferential transmission to ADHD probands (chi2 = 3.815, P = 0.051) and a significant preferential transmission to probands of ADHDC (chi2 = 4.198, P = 0.040). Additional polymorphisms in this gene need to be studied further.     

先天性髋脱位与HOXB9基因或COL1A1基因传递不平衡研究

目的 探讨先天性髋脱位(congenital dislocation of the hip，CDH)与HOXB9基因或COL1Al基因是否存在相关性。方法 在胚胎肢体发育调控相关的HOXB9基因和COL1A1基因共同所在的染色体区域17q21内选择微卫星DNA标记D17S1820，应用聚合醇链反应及变性聚丙烯酰胺凝胶电泳技术，对101个CDH核心家系的303名成员进行基因型分析，并进行传递不平衡检验(transmission disequilibrium test,TDT)。结果 在D17S1820多态性标记位点上共检测到12个等位基因。TDT分析显示，CDH与D17S1820遗传标记位点的第4个等位基因存在传递不平衡(x^2＝6．025，P＝0．014)。结论 CDH与HOXB9基因和COLlAl基因共同所在的染色体区域17q21有关联，HOXB9基因和(或)COLlAl基因可能是CDH的易感基因。     

染色体17q21区域发育性髋关节发育不良易感基因的定位

目的 在染色体17q21区域的D17S1820附近定位发育性髋关节发育不良(developmental dysplasia of the hip,DDH)的易感基因.方法 根据等位基因的数目(≥5)、杂合度(≥0.70)及多态信息含量(≥0.5),在D17S1820附近选择了11个短串联重复序列(short tandem repeat,STR)位点,采用PCR-毛细管电泳的方法,对103个DDH核心家系的309名成员进行基因分型,并进行传递不平衡检验(transmission disequilib rium test,TDT).结果 D17S810和D17S931因不能提供充足的多态信息,未进行TDT检验.其余9个STR多态位点在103个核心家系中的基因型分析结果符合孟德尔遗传模式.TDT检验结果显示,位于两端的D17S1787和D17S787与DDH不存在传递不平衡,而D17S855、D17S858、D17S806、D17S1877、D17S941、D17S752及D17S790与DDH均存在传递不平衡.将DDH易感基因的区域初步定位于D17S855～D17S790之间约11.70 cM的范围内.结论 17号染色体D17S855～D17S790之间约11.70 cM的区域与DDH有关联,在该区域可能存在DDH的易感基因.     

Promotor genotype of the platelet-derived growth factor receptor-alpha gene shows population stratification but not association with spina bifida meningomyelocele

Neural tube defects (NTDs) constitute a major group of congenital malformations with an overall incidence of approximately 1-2 in 1,000 live births in the United States. Hispanic Americans have a 2.5 times higher risk than the Caucasian population. Spina bifida meningomyelocele (SBMM) is a major clinical presentation of NTDs resulting from lack of closure of the spinal cord caudal to the head. In a previous study of spina bifida (SB) patients of European Caucasian descent, it was suggested that specific haplotypes of the platelet-derived growth factor receptor-alpha (PDGFRA) gene P1 promoter strongly affected the rate of NTD genesis. In our study, we evaluated the association of PDGFRA P1 in a group of 407 parent-child triads (167 Caucasian, 240 Hispanics) and 164 unrelated controls (89 Caucasian, 75 Hispanic). To fully evaluate the association of PDGFRA P1, we performed both transmission-disequilibrium test (TDT) and association analyses to test the hypotheses that PDGFRA P1 was (1) transmitted preferentially in SBMM affected children and (2) associated with the condition of SBMM comparing affected children to unaffected controls. We did find that there was a different allelic and genotypic distribution of PDGFRA P1 when comparing Hispanics and Caucasians. However, neither ethnic group showed strong association between SBMM and the PDGFRA P1 region. These findings suggest that PDGFRA P1 does not have a major role in the development of SBMM.     

Isolation of a diverged homeobox gene, M0X1, from the BRCA1 region on 17q21 by solution hybrid capture

Using the technique of solution hybridization coupled with magneticbead capture, we have isolated a novel homeobox-containing genefrom the BRCA1 region of 17q21. This gene is the human homologueof the mouse Mox1 gene previously localized to a syntenic regionof mouse chromosome 11. Multiple overlapping cDNAs of humanM0X1 were Identified using both a cosmid and a P1 genomic clonecontaining the microsatellite markers D17S750 and D17S858 whichmap within the BRCA1 region defined by D17S776 and D17S78. M0X1expression was observed In a variety of normal tissues examined,Including breast and ovary. Given that the gene contains a homeoboxdomain and has the potential to regulate growth and differentiation,M0X1 represents an attractive candidate for the BRCA1 gene.This possibility was Investigated in a series of BRCA1 kindredsand primary sporadic breast tumors. No evidence for mutationwas found In the coding sequence, making It unlikely that M0X1Is the BRCA1 gene. However, the widespread expression of M0X1in non-embryonal tissues suggests a role In normal cell biologywhich warrants further study.     

中国汉族和维吾尔族MRC1基因多态性与肺结核病的相关性

目的 探讨中国汉族和维吾尔族人群MRC1基因多态性与肺结核病易感性的联系. 方法 应用PCR和DNA测序技术,对中国汉族454例和维吾尔族595例人群的MRC1基因的第7号外显子6个SNPs(G1186A、G1195A、T1212C、C1221G、C1303T和C1323T)基因型及基因频率分布进行检测,并进行连锁不平衡分析. 结果 中国汉族人群中G1186A位点等位基因G型分布频率在肺结核病组和正常健康组之间存在显著差异(P =0.037;OR =0.76;95％ CI:0.58～0.98);AG基因型在两组之间存在显著性差异(P ＜0.01;OR=0.57;95％ CI:0.37 ～0.87).在年龄和性别校正后,G1186A位点在显性(P＜0.01;OR=0.59;95％ CI:0.40～0.87)、超显性(P =0.045;OR =0.69;95％ CI:0.47～0.99)和加性模式(P =0.041;OR=0.76;95％ CI:0.59 ～0.99)时,与肺结核病存在显著相关性.在维吾尔族人群中G1186A位点的等位基因G的分布频率在两组之间的分布具有显著性差异(P =0.031;OR=1.29;95％CI:1.02 ～ 1.62);基因型分析发现AA基因型在两组之间也存在显著性差异(P=0.033;OR=1.64;95％ CI:1.04～2.60);在年龄和性别校正后,G1186A位点在加性模式下与肺结核病存在相关性(P=0.033;OR=1.28;95％ CI:1.02～1.61).连锁不平衡分析发现,构建的单体型GGTCCT(P=0.032;OR =0.75;95％ CI:0.57 ～0.97)和GGTCCC(P=0.044;OR=0.57;95％ CI:0.33 ～0.99)与肺结核病存在显著的相关性. 结论 MRC1基因G1186A位点与中国人群肺结核病相关.     

Association between 7q31 markers and Tourette syndrome

Tourette syndrome (TS) is a complex neuropychiatric disorder with a strong genetic basis. Although no specific susceptibility genes have been identified for TS, cytogenetic studies in selected cases suggest the existence of a predisposing gene located in the 7q31 chromosomal region. In order to test the hypothesis of a possible relationship between this region and TS at the population level, we undertook a family based association study in a sample of French Canadian patients from Quebec. For this purpose, markers D7S522, D7S523, and D7S1516 were tested using the extended transmission disequilibrium test (e-TDT). Marker D7S522 showed a biased transmission of alleles from heterozygote parents to their TS offsprings (allele-wise TDT chi(2) = 12.61, 4 df, P = 0.013, genotype-wise TDT chi(2) = 15.49, 7 df, P = 0.030). When the analysis was restricted to patients without ADHD or OCD comorbidity, similar results were observed both allele and genotype-wise (chi(2) = 10.68, 4 df, P = 0.03 and chi(2) = 12.55, 5 df, P = 0.028, respectively). In addition, marker D7S523 was also associated (allele-wise TDT chi(2) = 18.37, 7 df, P = 0.01 and genotype-wise TDT chi(2) = 46.26, 17 df, P = 0.00016), and showed a tendency for association in the comorbidity-free subgroup (genotype-wise TDT chi(2) = 18.7, 10 df, P = 0.044). Finally, marker D7S1516, contained in the inner mitochondrial membrane peptidase 2 like (IMMP2L) gene, also showed a tendency for association (genotype-wise TDT chi(2) = 32.87, 21 df, P = 0.048). These results may reflect the proximity of markers D7S522, D7S523, and possibly D7S1516 to a gene or regulatory region relevant to TS predisposition.     

NRAMP1 (SLC11A1) gene polymorphisms that correlate with autoimmune versus infectious disease susceptibility in tuberculosis and rheumatoid arthritis

NRAMP1 gene has multiple pleiotropic effects on macrophage activation pathways. These pleiotropic effects may increase resistance to infections such as tuberculosis (TB), but may also lead to susceptibility of autoimmune diseases such as rheumatoid arthritis (RA). It has been hypothesized that allele 3 would be associated with autoimmune diseases, whereas allele 2 would be associated with infectious diseases, and genetic factors that enhanced survival in the epidemics of TB might have led to susceptibility for the development of RA. We analysed four NRAMP1 gene polymorphisms including 5′ promoter (GT)_n (rs34448891), INT4 (469 + 14G/C) (rs3731865), 3′UTR (1729 + 55del4) (rs17235416) and D543N (codon 543, Asp to Asn) (rs17235409) in 112 patients with TB, 98 patients with RA, 80 healthy controls for TB and 122 healthy controls for RA using ARMS‐PCR and PCR‐RFLP. We found a significant association between INT4 and RA (P = 0.004, odds ratio: 2.06, 95% CI: 1.24–3.41), but no significant differences between 5′ promoter, D543N, 3′UTR polymorphisms and RA. There were no associations between NRAMP1 gene polymorphisms and TB. Similarly, no significant differences were observed between NRAMP1 polymorphisms and rheumatoid factor positivity and erosive disease in RA and localization of TB. INT4 polymorphism may be associated with RA in Turkish patients.     

Loss of p53 partially rescues embryonic development of Palb2 knockout mice but does not foster haploinsufficiency of Palb2 in tumour suppression

PALB2 interacts with BRCA1 and BRCA2 in supercomplexes involved in DNA repair via homologous recombination. Heterozygous germline mutations in PALB2 confer a moderate risk of breast cancer, while biallelic PALB2 mutations are linked to a severe form of Fanconi anaemia characterized by early childhood solid tumours and severe chromosomal instability. In contrast to BRCA1- or BRCA2-associated cancers, breast tumours in heterozygous PALB2 mutation carriers do not show loss of the wild-type allele, suggesting PALB2 might be haploinsufficient for tumour suppression. To study the role of PALB2 in development and tumourigenesis, we have generated Palb2(GT) mouse mutants using a gene trap approach. Whereas Palb2(GT/GT) homozygous mutant embryos died at mid-gestation due to massive apoptosis, Palb2(GT/+) heterozygous mice were viable and did not show any obvious abnormalities. Deletion of p53 alleviated the phenotype of Palb2(GT/GT) embryos, but did not rescue embryonic lethality. In addition, loss of p53 did not significantly collaborate with Palb2 heterozygosity in tumourigenesis in heterozygous or homozygous p53 knockout mice. Tumours arising in Palb2(GT/+) ;p53(+/-) or Palb2(GT/+) ;p53(-/-) compound mutant mice retained the wild-type Palb2 allele and did not display increased genomic instability.