Biomedical subjects

Nazneen Rahman

Publications and source records attributed to Nazneen Rahman.

At least 19 recordsLinked to original sources

PubMed2006

Biallelic mutations in PALB2 cause Fanconi anemia subtype FA-N and predispose to childhood cancer.

PALB2 was recently identified as a nuclear binding partner of BRCA2. Biallelic BRCA2 mutations cause Fanconi anemia subtype FA-D1 and predispose to childhood malignancies. We identified pathogenic mutations in PALB2 (also known as FANCN) in seven families affected with Fanconi anemia and cancer in early childhood, demonstrating that biallelic PALB2 mutations cause a new subtype of Fanconi anemia, FA-N, and, similar to biallelic BRCA2 mutations, confer a high risk of childhood cancer.

Alleles↗

PubMed2006

PALB2, which encodes a BRCA2-interacting protein, is a breast cancer susceptibility gene.

PALB2 interacts with BRCA2, and biallelic mutations in PALB2 (also known as FANCN), similar to biallelic BRCA2 mutations, cause Fanconi anemia. We identified monoallelic truncating PALB2 mutations in 10/923 individuals with familial breast cancer compared with 0/1,084 controls (P = 0.0004) and show that such mutations confer a 2.3-fold higher risk of breast cancer (95% confidence interval (c.i.) = 1.4-3.9, P = 0.0025). The results show that PALB2 is a breast cancer susceptibility gene and further demonstrate the close relationship of the Fanconi anemia-DNA repair pathway and breast cancer predisposition.

Adult↗

PubMed2006

Truncating mutations in the Fanconi anemia J gene BRIP1 are low-penetrance breast cancer susceptibility alleles.

We identified constitutional truncating mutations of the BRCA1-interacting helicase BRIP1 in 9/1,212 individuals with breast cancer from BRCA1/BRCA2 mutation-negative families but in only 2/2,081 controls (P = 0.0030), and we estimate that BRIP1 mutations confer a relative risk of breast cancer of 2.0 (95% confidence interval = 1.2-3.2, P = 0.012). Biallelic BRIP1 mutations were recently shown to cause Fanconi anemia complementation group J. Thus, inactivating truncating mutations of BRIP1, similar to those in BRCA2, cause Fanconi anemia in biallelic carriers and confer susceptibility to breast cancer in monoallelic carriers.

Adult↗

PubMed2006

Sotos syndrome.

Sotos syndrome is an autosomal dominant condition characterised by a distinctive facial appearance, learning disability and overgrowth resulting in tall stature and macrocephaly. In 2002, Sotos syndrome was shown to be caused by mutations and deletions of NSD1, which encodes a histone methyltransferase implicated in chromatin regulation. More recently, the NSD1 mutational spectrum has been defined, the phenotype of Sotos syndrome clarified and diagnostic and management guidelines developed.

Body Height↗

PubMed2006

ATM mutations that cause ataxia-telangiectasia are breast cancer susceptibility alleles.

We screened individuals from 443 familial breast cancer pedigrees and 521 controls for ATM sequence variants and identified 12 mutations in affected individuals and two in controls (P = 0.0047). The results demonstrate that ATM mutations that cause ataxia-telangiectasia in biallelic carriers are breast cancer susceptibility alleles in monoallelic carriers, with an estimated relative risk of 2.37 (95% confidence interval (c.i.) = 1.51-3.78, P = 0.0003). There was no evidence that other classes of ATM variant confer a risk of breast cancer.

Alleles↗

PubMed2006

PHOX2B analysis in non-syndromic neuroblastoma cases shows novel mutations and genotype-phenotype associations.

Neuroblastoma (NB) is an embryonal tumor originating from neural crest cells and is one of the most common solid tumors of childhood. Recently, constitutional mutations in PHOX2B have been shown to confer an increased risk of NB. To date, mutations predisposing to neural crest tumors have been reported in 20 individuals from 16 families. These families included additional clinical features such as Hirschsprung (HSCR) disease or congenital central hypoventilation syndrome, either in the index case or relatives. The contribution of PHOX2B mutations to NB cases without additional features is unclear. To address this we sequenced PHOX2B in constitutional DNA from 86 individuals with non-syndromic NB (4 cases had a family history of NB). We identified two mutations, 600delC, a frameshift mutation in an individual with isolated, unifocal NB and G197D, a missense mutation that was present in a family with multiple individuals with NB but no evidence of autonomic dysfunction. These data demonstrate that PHOX2B mutations are a rare cause of non-syndromic NB. The mutations we identified are outside the domains typically mutated in PHOX2B syndromes. This provides further evidence that the underlying PHOX2B mutational mechanism influences tumor risk and suggests that the position of missense mutations may influence the resulting phenotype.

Amino Acid Sequence↗

PubMed2006

Evaluation of RAD50 in familial breast cancer predisposition.

The genes predisposing to familial breast cancer are largely unknown, but 5 of the 6 known genes are involved in DNA damage repair. RAD50 is part of a highly conserved complex important in recognising, signalling and repairing DNA double-strand breaks. Recently, a truncating mutation in the RAD50 gene, 687delT, was identified in 2 Finnish breast cancer families. To evaluate the contribution of RAD50 to familial breast cancer, we screened the whole coding region for mutations in 435 UK and 46 Finnish familial breast cancer cases. We identified one truncating mutation, Q350X, in one UK family. We screened a further 544 Finnish familial breast cancer cases and 560 controls for the 687delT mutation, which was present in 3 cases (0.5%) and 1 control (0.2%). Neither Q350X nor 687delT segregated with cancer in the families in which they were identified. Functional analyses suggested that RAD50 687delT is a null allele as there was no detectable expression of the mutant protein. However, the wild-type allele was retained and expressed in breast tumors from mutation carriers. The abundance of the full-length RAD50 protein was reduced in carrier lymphoblastoid cells, suggesting a possible haploinsufficiency mechanism. These data indicate that RAD50 mutations are rare in familial breast cancer and either carry no, or a very small, increased risk of cancer. Altogether, these results suggest RAD50 can only be making a very minor contribution to familial breast cancer predisposition in UK and Finland.

Acid Anhydride Hydrolases↗

PubMed2006

A genome wide linkage search for breast cancer susceptibility genes.

Mutations in known breast cancer susceptibility genes account for a minority of the familial aggregation of the disease. To search for further breast cancer susceptibility genes, we performed a combined analysis of four genome-wide linkage screens, which included a total of 149 multiple case breast cancer families. All families included at least three cases of breast cancer diagnosed below age 60 years, at least one of whom had been tested and found not to carry a BRCA1 or BRCA2 mutation. Evidence for linkage was assessed using parametric linkage analysis, assuming both a dominant and a recessive mode of inheritance, and using nonparametric methods. The highest LOD score obtained in any analysis of the combined data was 1.80 under the dominant model, in a region on chromosome 4 close to marker D4S392. Three further LOD scores over 1 were identified in the parametric analyses and two in the nonparametric analyses. A maximum LOD score of 2.40 was found on chromosome arm 2p in families with four or more cases of breast cancer diagnosed below age 50 years. The number of linkage peaks did not differ from the number expected by chance. These results suggest regions that may harbor novel breast cancer susceptibility genes. They also indicate that no single gene is likely to account for a large fraction of the familial aggregation of breast cancer that is not due to mutations in BRCA1 or BRCA2.

Breast Neoplasms↗

PubMed2006

A multicenter study of cancer incidence in CHEK2 1100delC mutation carriers.

The CHEK2 1100delC protein-truncating mutation has a carrier frequency of approximately 0.7% in Northern and Western European populations and confers an approximately 2-fold increased risk of breast cancer. It has also been suggested to increase risks of colorectal and prostate cancer, but its involvement with these or other types of cancer has not been confirmed. The incidence of cancer other than breast cancer in 11,116 individuals from 734 non-BRCA1/2 breast cancer families from the United Kingdom, Germany, Netherlands, and the United States was compared with that predicted by population rates. Relative risks (RR) to carriers and noncarriers were estimated by maximum likelihood, via the expectation-maximization algorithm to allow for unknown genotypes. Sixty-seven families contained at least one tested CHEK2 1100delC mutation carrier. There was evidence of underreporting of cancers in male relatives (422 cancers observed, 860 expected) but not in females (322 observed, 335 expected); hence, we focused on cancer risks in female carriers. The risk of cancers other than breast cancer in female carriers was not significantly elevated, although a modest increase in risk could not be excluded (RR, 1.18; 95% confidence interval, 0.64-2.17). The carrier risk was not significantly raised for any individual cancer site, including colorectal cancer (RR, 1.60; 95% confidence interval, 0.54-4.71). However, between ages 20 to 50 years, the risks of colorectal and lung cancer were both higher in female carriers than noncarriers (P = 0.041 and 0.0001, respectively). There was no evidence of a higher prostate cancer risk in carriers than noncarriers (P = 0.26), although underreporting of male cancers limited our power to detect such a difference. Our results suggest that the risk of cancer associated with CHEK2 1100delC mutations is restricted to breast cancer, although we cannot rule out a small increase in overall cancer risk.

Breast Neoplasms↗

PubMed2005

Familial gigantism caused by an NSD1 mutation.

A three-generation family with autosomal dominant segregation of a novel NSD1 mutation (6605G --> A, resulting in Cys2202Tyr) is reported. Haploinsufficiency of NSD1 has been identified as the major cause of Sotos syndrome. The overgrowth condition (MIM 117550) is characterized by facial anomalies, macrocephaly, advanced bone age, and learning disabilities. Manifestations in the present family include dramatically increased height, weight, and head circumference together with a long face, large mandible, and large ears, but mental deficiency was absent.

Abnormalities, Multiple↗

PubMed2005

Comparative genomic hybridization and BUB1B mutation analyses in childhood cancers associated with mosaic variegated aneuploidy syndrome.

We previously demonstrated that constitutional BUB1B mutations cause mosaic variegated aneuploidy, a condition characterized by constitutional aneuploidies and childhood cancer predisposition. To further investigate the role of BUB1B in cancer predisposition we performed comparative genomic hybridization analysis in an embryonal rhabdomyosarcoma from an MVA case with biallelic BUB1B mutations, revealing aneuploidies typical of sporadic E-RMS, with gain of chromosomes 3, 8, 13 and loss of chromosomes 9, 14, X. To investigate whether somatic BUB1B mutations occur in sporadic childhood cancers we screened 30 Wilms tumours, 10 acute lymphoblastic leukemias, nine rhabdomyosarcomas and 11 rhabdomyosarcoma cell lines for BUB1B mutations. We identified seven exonic and six intronic variants. Six of the exonic variants were synonymous and one resulted in a non-synonymous conservative missense alteration that was also present in a control. These data suggest that the genetic progression in rhabdomyosarcoma from MVA and non-MVA cases may be similar, but that somatic BUB1B mutations are unlikely to be common in sporadic childhood cancers known to be associated with MVA.

Aneuploidy↗

PubMed2005

Distinct genomic profiles in hereditary breast tumors identified by array-based comparative genomic hybridization.

Mutations in BRCA1 and BRCA2 account for a significant proportion of hereditary breast cancers. Earlier studies have shown that inherited and sporadic tumors progress along different somatic genetic pathways and that global gene expression profiles distinguish between these groups. To determine whether genomic profiles similarly discriminate among BRCA1, BRCA2, and sporadic tumors, we established DNA copy number profiles using comparative genomic hybridization to BAC-clone microarrays providing <1 Mb resolution. Tumor DNA was obtained from BRCA1 (n = 14) and BRCA2 (n = 12) mutation carriers, as well as sporadic cases (n = 26). Overall, BRCA1 tumors had a higher frequency of copy number alterations than sporadic breast cancers (P = 0.00078). In particular, frequent losses on 4p, 4q, and 5q in BRCA1 tumors and frequent gains on 7p and 17q24 in BRCA2 tumors distinguish these from sporadic tumors. Distinct amplicons at 3q27.1-q27.3 were identified in BRCA1 tumors and at 17q23.3-q24.2 in BRCA2 tumors. A homozygous deletion on 5q12.1 was found in a BRCA1 tumor. Using a set of 169 BAC clones that detect significantly (P < 0.001) different frequencies of copy number changes in inherited and sporadic tumors, these could be discriminated into separate groups using hierarchical clustering. By comparing DNA copy number and RNA expression for genes in these regions, several candidate genes affected by up- or down-regulation were identified. Moreover, using support vector machines, we correctly classified BRCA1 and BRCA2 tumors (P < 0.0000004 and 0.00005, respectively). Further validation may prove this tumor classifier to be useful for selecting familial breast cancer cases for further mutation screening, particularly, as these data can be obtained using archival tissue.

Breast Neoplasms↗

PubMed2005

Genotype-phenotype associations in Sotos syndrome: an analysis of 266 individuals with NSD1 aberrations.

We identified 266 individuals with intragenic NSD1 mutations or 5q35 microdeletions encompassing NSD1 (referred to as "NSD1-positive individuals"), through analyses of 530 subjects with diverse phenotypes. Truncating NSD1 mutations occurred throughout the gene, but pathogenic missense mutations occurred only in functional domains (P < 2 x 10(-16)). Sotos syndrome was clinically diagnosed in 99% of NSD1-positive individuals, independent of the molecular analyses, indicating that NSD1 aberrations are essentially specific to this condition. Furthermore, our data suggest that 93% of patients who have been clinically diagnosed with Sotos syndrome have identifiable NSD1 abnormalities, of which 83% are intragenic mutations and 10% are 5q35 microdeletions. We reviewed the clinical phenotypes of 239 NSD1-positive individuals. Facial dysmorphism, learning disability, and childhood overgrowth were present in 90% of the individuals. However, both the height and head circumference of 10% of the individuals were within the normal range, indicating that overgrowth is not obligatory for the diagnosis of Sotos syndrome. A broad spectrum of associated clinical features was also present, the occurrence of which was largely independent of genotype, since individuals with identical mutations had different phenotypes. We compared the phenotypes of patients with intragenic NSD1 mutations with those of patients with 5q35 microdeletions. Patients with microdeletions had less-prominent overgrowth (P = .0003) and more-severe learning disability (P = 3 x 10(-9)) than patients with mutations. However, all features present in patients with microdeletions were also observed in patients with mutations, and there was no correlation between deletion size and the clinical phenotype, suggesting that the deletion of additional genes in patients with 5q35 microdeletions has little specific effect on phenotype. We identified only 13 familial cases. The reasons for the low vertical transmission rate are unclear, although familial cases were more likely than nonfamilial cases (P = .005) to carry missense mutations, suggesting that the underlying NSD1 mutational mechanism in Sotos syndrome may influence reproductive fitness.

Amino Acid Sequence↗

PubMed2005

Aneuploidy-cancer predisposition syndromes: a new link between the mitotic spindle checkpoint and cancer.

Genetic cancer predisposition syndromes have been crucial to the identification of genes and pathways involved in carcinogenesis. Constitutional gene mutations segregating with distinctive cancer phenotypes provide unequivocal evidence of a gene's causal role in cancer. This type of evidence has been central in proving that oncogenes and tumor suppressor genes can cause human cancers, but has been lacking for genes implicated in generating aneuploidy. However, recently we identified mutations in the mitotic checkpoint gene BUB1B in an autosomal recessive condition characterized by mosaic aneuploidies and childhood cancers. This finding strongly suggests that aneuploidy is causally related to cancer development.

Aneuploidy↗

PubMed2005

Confirmation of a hereditary motor and sensory neuropathy IIC locus at chromosome 12q23-q24.

Hereditary motor and sensory neuropathy type IIC (HMSN IIC) is an autosomal dominant axonal neuropathy. The cardinal features include distal muscle wasting and weakness, vocal cord paralysis, and mild sensory impairment. Recently, HMSN IIC locus was mapped to chromosome 12q23-24. Two families affected by HMSN IIC were identified and evaluated for linkage to this region. Segregation analysis in both families was consistent with linkage to chromosome 12q23-24. Combined analysis generated a multipoint LOD score of 2.1 at marker D12S1583 and refined the HMSN IIC gene interval to The clinical and molecular findings are discussed.

Adolescent↗

PubMed2005

Mechanisms predisposing to childhood overgrowth and cancer.

Several overgrowth conditions are believed to be associated with elevated risks of cancer, particularly in childhood. Beckwith-Wiedemann syndrome and Sotos syndrome are the most common overgrowth conditions, and both carry increased risks of certain tumors. In recent years, the identification of both the gene causing Sotos syndrome and the epigenetic subgroups underlying Beckwith-Wiedemann syndrome have enabled clarification of the cancer types and risks associated with these conditions. This has revealed striking differences in the cancer phenotypes associated with different molecular abnormalities. Elucidation of the mechanisms underlying cancer in overgrowth syndromes might yield important insights into the molecular basis of childhood tumors.

Beckwith-Wiedemann Syndrome↗

PubMed2005

Evaluation of NSD2 and NSD3 in overgrowth syndromes.

Sotos syndrome is an overgrowth condition predominantly caused by truncating mutations, missense mutations restricted to functional domains, or deletions of NSD1. NSD1 is a member of a protein family that includes NSD2 and NSD3, both of which show 70-75% sequence identity with NSD1. This strong sequence similarity suggests that abrogation of NSD2 or NSD3 function may cause non-NSD1 Sotos cases or other overgrowth phenotypes. To evaluate this hypothesis, we mutationally screened NSD2 and NSD3 in 78 overgrowth syndrome cases in which NSD1 mutations and deletions had been excluded. Additionally, we used microsatellite markers within the vicinity of the genes to look for whole gene deletions. No truncating mutations or gene deletions were identified in either gene. We identified two conservative missense NSD2 alterations in two non-Sotos overgrowth cases but neither was within a functional domain. We identified three synonymous and two intronic variants in NSD2 and two synonymous base substitutions in NSD3. Our results suggest that despite strong sequence similarity between NSD1, NSD2 and NSD3, the latter genes are unlikely to be making a substantial contribution to overgrowth phenotypes and thus may operate in distinct functional pathways from NSD1.

Carrier Proteins↗

PubMed2005

Periodontal treatment of two siblings with juvenile hyaline fibromatosis.

BACKGROUND AND AIM: Juvenile hyaline fibromatosis (JHF) is an autosomal recessive disease that presents with multiple subcutaneous nodular tumours, gingival fibromatosis, flexion contractures of the joint and hyaline material accumulation in extracellular area. Recently, the causative gene for JHF, capillary morphogenesis protein 2 (CMG2) was identified. In this case report, periodontal status, treatment and follow-up together with histopathologic evaluation of gingival tissue specimens and mutation screening of two JHF cases are presented. CASE REPORTS: A 10-year-old female (case 1) and her 3-year-old brother (case 2) were first examined in our department with a complaint of gingival hyperplasia in 1991. Symptoms of the disease were detected in two of four siblings in the family. Several gingivectomy operations were carried out over 11 years with hygiene motivation and initial phase therapy. After the last gingivectomy operation in 2002, the patients were reviewed frequently. RESULTS AND CONCLUSIONS: Although there was linear marginal gingival inflammation, no remarkable enlargement was noted at last appointment. Histopathological findings showed increased amounts of subepithelial nodular connective tissue, thinned epithelial mucosa, separated inter-cellular bridges and decreased numbers of connective tissue cells in gingival tissue samples. Electron microscopic examinations supported the histopathological findings. Mutation screening of CMG2 demonstrated that the siblings were homozygous for a pathogenic missense mutation, V386F. Our clinical findings demonstrate that gingivectomy is useful and frequent periodontal visits are important for maintaining oral hygiene and decreasing growth rate of gingiva in JHF.

Child↗