Association of PHB 1630 C>T and MTHFR 677 C>T polymorphisms with breast and ovarian cancer risk in BRCA1/2 mutation carriers: results from a multicenter study.

BACKGROUND: The variable penetrance of breast cancer in BRCA1/2 mutation carriers suggests that other genetic or environmental factors modify breast cancer risk. Two genes of special interest are prohibitin (PHB) and methylene-tetrahydrofolate reductase (MTHFR), both of which are important either directly or indirectly in maintaining genomic integrity. METHODS: To evaluate the potential role of genetic variants within PHB and MTHFR in breast and ovarian cancer risk, 4102 BRCA1 and 2093 BRCA2 mutation carriers, and 6211 BRCA1 and 2902 BRCA2 carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2 (CIMBA) were genotyped for the PHB 1630 C>T (rs6917) polymorphism and the MTHFR 677 C>T (rs1801133) polymorphism, respectively. RESULTS: There was no evidence of association between the PHB 1630 C>T and MTHFR 677 C>T polymorphisms with either disease for BRCA1 or BRCA2 mutation carriers when breast and ovarian cancer associations were evaluated separately. Analysis that evaluated associations for breast and ovarian cancer simultaneously showed some evidence that BRCA1 mutation carriers who had the rare homozygote genotype (TT) of the PHB 1630 C>T polymorphism were at increased risk of both breast and ovarian cancer (HR 1.50, 95%CI 1.10-2.04 and HR 2.16, 95%CI 1.24-3.76, respectively). However, there was no evidence of association under a multiplicative model for the effect of each minor allele. CONCLUSION: The PHB 1630TT genotype may modify breast and ovarian cancer risks in BRCA1 mutation carriers. This association need to be evaluated in larger series of BRCA1 mutation carriers.

PTEN mutation analysis in two genetic subtypes of high-grade oligodendroglial tumors. PTEN is only occasionally mutated in one of the two genetic subtypes.

We recently identified two genetic subtypes of high-grade oligodendroglial tumors (HG-OT): 1p-/19q- HG-OT are characterized by a loss of chromosome 1p32-36 (del(1)(p32-p36) and/or a del(19)(q13. 3); whereas +7/-10 HG-OT harbor a gain of chromosome 7 (+7) and/or a -10 without a loss of 1p32-36 and 19q13.3. Because a -10 and a +7 are most frequently detected in glioblastomas (GBM), the genotype of +7/-10 HG-OT suggests that these tumors are GBM with a prominent oligodendroglial phenotype rather than anaplastic oligodendrogliomas. PTEN is a tumor suppressor gene, located at 10q23.3, which is involved in tumor progression of GBM and other neoplasms. In this study, we screened for PTEN mutations in six low-grade oligodendroglial tumors (LG-OT), five 1p-/19q- HG-OT, seven +7/-10 HG-OT, and nine xenografted GBM. PTEN mutations were detected in none of the LG-OT and 1p-/19q- HG-OT, once in +7/-10 HG-OT, and frequently in GBM. As one of the +7/-10 HG-OT harbored a PTEN mutation, this demonstrates that PTEN can be involved in the oncogenesis of this genetic subtype of HG-OT. The lower frequency of PTEN mutations in +7/-10 HG-OT compared to GBM suggests that these tumors are of a distinct tumor type rather than GBM. Published by Elsevier Science Inc.

Novel PTEN mutations in patients with Cowden disease: absence of clear genotype-phenotype correlations.

Cowden disease (CD) is characterised by multiple hamartomas in a variety of tissues. The pathological hallmark is the presence of a number of trichilemmomas. Several neurological symptoms are also part of CD with megalencephaly and Lhermitte-Duclos disease (LDD) as the most important features. Early recognition of CD patients is important because of the increased risk of developing malignancies. Breast cancer is the most frequent malignancy, but also urogenital, digestive tract, and thyroid cancers are found with higher frequencies. CD was localised to chromosome 10q23 and the PTEN gene (also known as MMAC1 or TEP1) was shown to be involved. Germline mutations were identified in both familial and sporadic CD patients. We identified eight PTEN mutations, of which seven were novel, in 13 CD patients. Combined with previous data we have identified 17 independent CD mutations. Gross DNA alterations in CD patients were not detected. Genotype-phenotype relations are discussed. The only correlation suggested to exist is that missense mutations are not detected in LDD patients. However, larger numbers are needed to confirm this. Association of PTEN mutations and the occurrence of malignant breast disease found in an earlier study cannot be confirmed. Clinical features of five CD patients without a PTEN mutation in the coding sequence do not differ from CD patients with a PTEN mutation. Furthermore, it is likely that we have identified the majority of CD patients in the Netherlands. From this we estimate that CD has a prevalence of about 1 in 250,000 in the Dutch population with a low mutation frequency.

Lhermitte-Duclos disease as a component of Cowden's syndrome. Case report and review of the literature.

In recent years, 16 cases involving the association between Lhermitte-Duclos disease (LDD), which is a hamartomatous overgrowth of cerebellar tissue, and Cowden's syndrome (CS), an autosomal-dominant condition characterized by multiple hamartomas and neoplasias, have been reported. LDD may be one of the manifestations of CS. Recently, mutations of the PTEN/MMAC 1 gene, a tumor suppressor gene, have been found in families with CS, including four patients in whom LDD was diagnosed. The authors present a case of LDD in a 53-year-old woman who also had the typical mucocutaneous lesions found in CS, as well as goiter and intestinal polyposis. In this case, CS had never been suspected until the diagnosis of LDD was made. The mutation detected in the PTEN/MMAC 1 gene as well as neuropathological results are described.

Germline mutations in the PTEN/MMAC1 gene in patients with Cowden disease.

Cowden disease, also known as multiple hamartoma syndrome, is an autosomal dominant cancer syndrome with a high risk of breast and thyroid cancer. The gene involved has been localized to chromosome 10q22-23. Recently, the tumour suppressor gene PTEN/MMAC1, encoding a putative protein tyrosine or dual-specificity phosphatase, was cloned from that region and three mutations were detected in patients with Cowden disease. We confirmed that the PTEN/MMAC1 gene is indeed the gene for Cowden disease by a refined localization of the gene to the interval between D10S1761 and D10S541, which contains the PTEN/MMAC1 gene and, by mutation analysis in eight unrelated familial and 11 sporadic patients with Cowden disease. Eight different mutations were detected in various regions of the PTEN/MMAC1 gene. One mutation was detected twice. All detected changes in the gene can be predicted to have a very deleterious effect on the putative protein. Five of the nine patients have a mutation in exon 5 coding for the putative active site and flanking amino acids. Evaluation of the clinical data of the patients in which a mutation could be detected gives no clear indications for a correlation between the genotype and phenotype. In 10 patients no mutation could be detected so far. In support of the linkage data, no evidence has emerged from the phenotype of these patients suggestive for genetic heterogeneity.

Localization of the gene for Cowden disease to chromosome 10q22-23.

Cowden disease (CD) (MIM 158350), or multiple hamartoma syndrome, is a rare autosomal dominant familial cancer syndrome with a high risk of breast cancer. Its clinical features include a wide array of abnormalities but the main characteristics are hamartomas of the skin, breast, thyroid, oral mucosa and intestinal epithelium. The pathognomonic hamartomatous features of CD include multiple smooth facial papules, acral keratosis and multiple oral papillomas. The pathological hallmark of the facial papules are multiple trichilemmomas. Expression of the disease is variable and penetrance of the dermatological lesions is assumed to be virtually complete by the age of twenty. Central nervous system manifestations of CD were emphasized only recently and include megalencephaly, epilepsy and dysplastic gangliocytomas of the cerebellum (Lhermitte-Duclos disease, LDD). Early diagnosis is important since female patients with CD are at risk of developing breast cancer. Other lesions include benign and malignant disease of the thyroid, intestinal polyps and genitourinary abnormalities. To localize the gene for CD, an autosomal genome scan was performed. A total of 12 families were examined, resulting in a maximum lod score of 8.92 at theta = 0.02 with the marker D10S573 located on chromosome 10q22-23.

In organello footprint analysis of human mitochondrial DNA: human mitochondrial transcription factor A interactions at the origin of replication.

Using in organello footprint analysis, we demonstrate that within human placental mitochondria there is a high level of protein-DNA binding at regularly phased intervals throughout a 500-bp region encompassing the D-loop DNA origins and two promoter regions. Comparison with in vitro DNase I protection studies indicates that this protein-DNA interaction is due to non-sequence-specific binding by human mitochondrial transcription factor A (h-mtTFA). Since h-mtTFA can bend and wrap DNA, like its yeast counterpart ABF2, a primary function of h-mtTFA appears to be specific packaging of the mitochondrial DNA control region in vivo. Intervals of protein binding coincide with the spacing of the RNA start sites and prominent D-loop DNA 5' ends, suggesting a role for phased h-mtTFA binding in defining transcription and H-strand DNA replication origins. Significant protein-DNA interaction was also observed within the human homolog of conserved sequence block 1, both in organello and in vitro, using purified h-mtTFA.

Familial Angelman syndrome with a crossover in the critical deletion region.

More than two thirds of the patients with Angelman syndrome (AS) carry a deletion or other chromosomal abnormality in the 15q11-13 region. A much less frequent cause (4%) is paternal uniparental disomy of the entire chromosome. In general no abnormalities are detectable in familial cases and an inherited submicroscopic deletion was described only once. Here a familial case of 2 sibs with AS is reported. No major cytogenetic or molecular abnormality was identified, but a recombination event had occurred in the AS critical region. The AS locus, D15S113, D15S10, D15S11, and D15S18 mapped proximal and the GABRB3 gene, D15S97, the GABRA5 gene, and D15S12 distal to the crossover site. This recombination within the AS critical region confirmed the exclusion of GABRB3 as a candidate gene for AS. Other markers and candidate genes can be tested genetically as well for a possible role in AS.

Identification of four novel mutations in the COL4A5 gene of patients with Alport syndrome.

The type IV collagen alpha 5 chain (COL4A5) genes of patients with Alport syndrome were tested for major gene rearrangements by Southern blot analysis, using COL4A5 cDNA clones as probes. In addition, individual exons were screened for small mutations by single-strand conformation polymorphism (SSCP) analysis. Four new COL4A5 mutations were detected. A duplication of the nine most 3' located nucleotides of exon 49 and the first nucleotide of intron 49 was identified in the COL4A5 gene of one patient. Two patients displayed single base substitutions leading to, respectively, a proline to threonine and an arginine to glutamine substitution in the C-terminal end. Both substitutions involve amino acids conserved through evolution. In COL4A5 intron 41 a mutation changing the splice acceptor site from AG to AA was identified. All mutations cosegregate with the clinical phenotype of Alport syndrome in affected family members. In a control population of 50 individuals tested by PCR-SSCP these mutations were never identified. Together with two mutations reported previously, a total of six mutations were found in 26 patients with Alport syndrome (23%) after systematic screening of about 30% of the COL4A5 coding region. The clinical features of these six patients are described in detail.

X-linked borderline mental retardation with prominent behavioral disturbance: phenotype, genetic localization, and evidence for disturbed monoamine metabolism.

We have identified a large Dutch kindred with a new form of X-linked nondysmorphic mild mental retardation. All affected males in this family show very characteristic abnormal behavior, in particular aggressive and sometimes violent behavior. Other types of impulsive behavior include arson, attempted rape, and exhibitionism. Attempted suicide has been reported in a single case. The locus for this disorder could be assigned to the Xp11-21 interval between DXS7 and DXS77 by linkage analysis using markers spanning the X chromosome. A maximal multipoint lod score of 3.69 was obtained at the monoamine oxidase type A (MAOA) locus in Xp11.23-11.4. Results of 24-h urine analysis in three affected males indicated a marked disturbance of monoamine metabolism. These data are compatible with a primary defect in the structural gene for MAOA and/or monoamine oxidase type B (MAOB). Normal platelet MAOB activity suggests that the unusual behavior pattern in this family may be caused by isolated MAOA deficiency.

Linkage analysis with chromosome 15q11-13 markers shows genomic imprinting in familial Angelman syndrome.

Angelman syndrome (AS) and Prader-Willi syndrome (PWS) have become the classical examples of genomic imprinting in man, as completely different phenotypes are generated by the absence of maternal (AS) or paternal (PWS) contributions to the q11-13 region of chromosome 15 as a result of deletion or uniparental disomy. Apparently, most patients are sporadic cases. The genetic mechanism underlying familial AS has remained enigmatic for a long time. Recently, evidence has been emerging suggesting autosomal dominant inheritance of a detectable or undetectable defect in a gene or genes at 15q11-13, subject to genomic imprinting. The present report describes an unusually large pedigree with segregation of AS through maternal inheritance and apparent asymptomatic transmission through several male ancestors. Deletion and paternal disomy at 15q11-13 were excluded. However, the genetic defect is still located in this region, as we obtained a maximum lod score of 5.40 for linkage to the GABA receptor locus GABRB3 and the anonymous DNA marker D15S10, which have been mapped within or adjacent to the AS critical region at 15q11-13. The size of the pedigree allowed calculation of an odds ratio in favour of genomic imprinting of 9.25 x 10(5). This family illustrates the necessity of extensive pedigree analysis when considering recurrence risks for relatives of AS patients, those without detectable deletion or disomy in particular.

Different mutations in the COL4A5 collagen gene in two patients with different features of Alport syndrome.

Alport syndrome is a hereditary renal disease in which progressive renal failure is often accompanied by sensorineural deafness and ocular abnormalities. Recently, mutations were detected in the type IV collagen alpha 5 chain gene in Alport syndrome patients. We searched for mutations in this gene in 18 unrelated patients, and in two patients abnormalities were detected. In the gene of patient BB we identified a complex deletion, which included the exons encoding the non-collagenous domain and part of the collagenous region. This patient showed early onset nephritis (end-stage renal disease at 17 years) with deafness. Within a year after receiving a kidney from an unrelated donor, he developed an antiglomerular basement membrane nephritis. In patient WJ a point-mutation was detected, changing a tryptophane into a serine in the non-collagenous domain. His clinical features are milder (renal failure at 33 years, no hearing loss), and a recent renal allograft did not provoke antiglomerular basement membrane disease. These initial data suggest that differences in the extent of disruption of the non-collagenous domain may correlate with the severity and/or heterogeneity of Alport syndrome and with the development of nephritis in renal allografts.

Exclusion of the dysplastic nevus syndrome (DNS) locus from the short arm of chromosome 1 by linkage studies in Dutch families.

Familial dysplastic nevus syndrome (DNS) is an autosomal dominant premalignant condition characterized by multiple large moles of variable size and color and a strongly increased risk for cutaneous malignant melanoma. In order to determine the chromosomal localization of the DNS gene, linkage studies were initiated in six large Dutch families. No support was obtained for linkage between the loci for DNS and the rhesus blood group on chromosome 1. Data from additional markers (DNF15S1, D1Z2, FUCA1, D1S17, D1S57, and PGM1) make it possible to exclude the DNS gene from the short arm of chromosome 1 in these Dutch families.