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Martijn H Breuning

Publications and source records attributed to Martijn H Breuning.

At least 19 recordsLinked to original sources
PubMed2005

Genetic heterogeneity in Rubinstein-Taybi syndrome: mutations in both the CBP and EP300 genes cause disease.

CREB-binding protein and p300 function as transcriptional coactivators in the regulation of gene expression through various signal-transduction pathways. Both are potent histone acetyl transferases. A certain level of CREB-binding protein is essential for normal development, since inactivation of one allele causes Rubinstein-Taybi syndrome (RSTS). There is a direct link between loss of acetyl transferase activity and RSTS, which indicates that the disorder is caused by aberrant chromatin regulation. We screened the entire CREB-binding protein gene (CBP) for mutations in patients with RSTS by using methods that find point mutations and larger rearrangements. In 92 patients, we were able to identify a total of 36 mutations in CBP. By using multiple ligation-dependent probe amplification, we found not only several deletions but also the first reported intragenic duplication in a patient with RSTS. We extended the search for mutations to the EP300 gene and showed that mutations in EP300 also cause this disorder. These are the first mutations identified in EP300 for a congenital disorder.

Acetyltransferases↗
PubMed2005

Mutation screening of EXT1 and EXT2 by direct sequence analysis and MLPA in patients with multiple osteochondromas: splice site mutations and exonic deletions account for more than half of the mutations.

Multiple osteochondromas (MO) is an autosomal dominant condition, caused by mutations in either the EXT1 or the EXT2 gene. The DNA of a cohort of 35 patients, clinically suspected to be affected with MO, was screened for mutations by a combination of direct sequence analysis and multiplex ligation-dependent probe amplification (MLPA). In this cohort, 26 pathogenic gene alterations were found (74%). With sequence analysis mutations were detected in 22 patients (63%). In total, 10 mutations were detected in the EXT1 and 12 in the EXT2 gene. The number of the splice site mutations detected was larger than expected from the literature. In addition, with the MLPA four deletions of one or more exons were found in this cohort. Two patients, of whom one had a negative family history, showed deletions of exon 1 of the EXT1 gene, which is possibly a deletion hot spot. In patients suspected to be affected by MO, we recommend a quantitative analysis such as MLPA, followed by direct sequence analysis for the screening of the EXT1 and EXT2 genes.

Cohort Studies↗
PubMed2004

Three new families with arterial tortuosity syndrome.

Arterial tortuosity syndrome (ATS) is a rare condition with autosomal recessive inheritance characterized by connective tissue abnormalities. The most specific clinical findings are cardiovascular anomalies including tortuosity, lengthening, aneurysm, and stenosis formation of major arteries. Also ventricular hypertrophy is frequently present. Other anomalies are skin hyperextensibility and cutis laxa, joint laxity or contractures of the joints, and inguinal herniae. Histology shows disruption of elastic fibers of the media. These features suggest that ATS is a connective tissue disorder. A biochemical or molecular defect has not yet been identified. We describe here nine additional ATS patients from three consanguineous Moroccan families and review a total of 35 patients with this uncommon condition.

Abnormalities, Multiple↗
PubMed2004

Feeling at risk: how women interpret their familial breast cancer risk.

Women's inaccuracy in recalling their breast cancer risk, even immediately after genetic counseling, has received much attention. However, scarce data are available about how women describe their risk in their own words and about what the risk information actually means to them. The present study aims to address interpretations questions and to assess whether these are congruent with the objective risk. Face-to-face interviews were conducted with 123 women immediately after their (initial) counseling session. N-Vivo software was used to describe the data. The level of accuracy of recall depended strongly on the leniency of the criterion applied. For example, the level of verbal accuracy ranged from 25.8% (an exact match with the verbal label) to 98.4% (a more global awareness of having a high versus a low risk). In assessing the significance of personal risk information, we identified a wide variety of risk beliefs, and stress and coping responses. In general, women associated their risk with the medical options, for example, breast screening, that were available for them given their risk status. The results indicate that the accuracy of recall might be a limited outcome measure for the effectiveness of genetic counseling. First, this is because the level of accuracy of recall depends on how rigorously accuracy is defined. Secondly, because the probability of occurrence is just one of the elements comprising perceived risk, accuracy might rather apply to the distress, and to risk management behaviors that are elicited by the risk information. These beliefs that women hold about their risk status, and concomitant levels of stress should play a prominent role in genetic counseling.

Adaptation, Psychological↗
PubMed2004

Lowering of Pkd1 expression is sufficient to cause polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a major cause of renal failure and is characterized by the formation of many fluid-filled cysts in the kidneys. It is a systemic disorder that is caused by mutations in PKD1 or PKD2. Homozygous inactivation of these genes at the cellular level, by a 'two-hit' mechanism, has been implicated in cyst formation but does not seem to be the sole mechanism for cystogenesis. We have generated a novel mouse model with a hypomorphic Pkd1 allele, Pkd1(nl), harbouring an intronic neomycin-selectable marker. This selection cassette causes aberrant splicing of intron 1, yielding only 13-20% normally spliced Pkd1 transcripts in the majority of homozygous Pkd1(nl) mice. Homozygous Pkd1(nl) mice are viable, showing bilaterally enlarged polycystic kidneys. This is in contrast to homozygous knock-out mice, which are embryonic lethal, and heterozygous knock-out mice that show only a very mild cystic phenotype. In addition, homozygous Pkd1(nl) mice showed dilatations of pancreatic and liver bile ducts, and the mice had cardiovascular abnormalities, pathogenic features similar to the human ADPKD phenotype. Removal of the neomycin selection-cassette restored the phenotype of wild-type mice. These results show that a reduced dosage of Pkd1 is sufficient to initiate cystogenesis and vascular defects and indicate that low Pkd1 gene expression levels can overcome the embryonic lethality seen in Pkd1 knock-out mice. We propose that in patients reduced PKD1 expression of the normal allele below a critical level, due to genetic, environmental or stochastic factors, may lead to cyst formation in the kidneys and other clinical features of ADPKD.

Alternative Splicing↗
PubMed2004

Genotype-phenotype correlation in patients suspected of having Sotos syndrome.

BACKGROUND: Deletions and mutations in the NSD1 gene are the major cause of Sotos syndrome. We wanted to evaluate the genotype-phenotype correlation in patients suspected of having Sotos syndrome and determine the best discriminating parameters for the presence of a NSD1 gene alteration. METHODS: Mutation and fluorescence in situ hybridization analysis was performed on blood samples of 59 patients who were clinically scored into 3 groups. Clinical data were compared between patients with and without NSD1 alterations. With logistic regression analysis the best combination of predictive variables was obtained. RESULTS: In the groups of typical, dubious and atypical Sotos syndrome, 81, 36 and 0% of the patients, respectively, showed NSD1 gene alterations. Four deletions were detected. In 23 patients (2 families) 19 mutations were detected (1 splicing defect, 3 non-sense, 7 frameshift and 8 missense mutations). The best predictive parameters for a NSD1 gene alteration were frontal bossing, down-slanted palpebral fissures, pointed chin and overgrowth. Higher incidences of feeding problems and cardiac anomalies were found. The parameters, delayed development and advanced bone age, did not differ between the 2 subgroups. CONCLUSIONS: In our patients suspected of having Sotos syndrome, facial features and overgrowth were highly predictive of a NSD1 gene aberration, whereas developmental delay and advanced bone age were not.

Abnormalities, Multiple↗
PubMed2004

Aberrant polycystin-1 expression results in modification of activator protein-1 activity, whereas Wnt signaling remains unaffected.

Polycystin-1, the polycystic kidney disease 1 gene product, has been implicated in several signaling complexes that are known to regulate essential cellular functions. We investigated the role of polycystin-1 in Wnt signaling and activator protein-1 (AP-1) activation. To this aim, a membrane-targeted construct encoding the conserved C-terminal region of mouse polycystin-1 reported to mediate signal transduction activity was expressed in human embryonic and renal epithelial cells. To ensure specificity and minimal cotransfection effects, we focused our study on the endogenous proteins that actually transduce the signals, beta-catenin and T-cell factor/lymphoid-enhancing factor for Wnt signaling and (phosphorylated) c-Jun, ATF2, and c-Fos for AP-1. Our data indicate that the C-terminal region of polycystin-1 activates AP-1 by inducing phosphorylation and expression of at least c-Jun and ATF2, whereas c-Fos was not affected. Under our experimental conditions, polycystin-1 did not modulate Wnt signaling. AP-1 activity was aberrant in human autosomal dominant polycystic kidney disease (ADPKD) renal cystic epithelial cells and in renal epithelial cells expressing transgenic full-length polycystin-1, resulting in decreased Jun-ATF and increased Jun-Fos activity, whereas Wnt signaling remained unaffected. Since our data indicate that aberrant polycystin-1 expression results in altered AP-1 activity, polycystin-1 may be required for adequate AP-1 activity.

Activating Transcription Factor 2↗
PubMed2004

Altered distribution and co-localization of polycystin-2 with polycystin-1 in MDCK cells after wounding stress.

Polycystin-1 and -2 are integral membrane glycoproteins defective in autosomal dominant polycystic kidney disease (ADPKD). Recent studies showed a coupled polycystin-1 and -2 action in cell signaling and channel activation suggesting an important biological role for the two proteins at the plasma membrane. To gain a better understanding about the (co)-distribution and dynamics of the polycystin-1 and -2 complex under stress conditions, we used a wound-healing model of Madine Darby canine kidney (MDCK) renal epithelial cells. In this model, cells near the wound edge undergo a process of reorganization to active migration, while cells further from the edge are unaffected and remain confluent. For the first time, endogenous polycystin-1 and -2 were found to partly co-localize in the plasma membrane of confluent monolayers, and both proteins co-localized in the primary cilium. Upon wound healing, the association of polycystin-2 to the membrane was greatly reduced at the wound edge and the submarginal cells. Polycystin-1 remained incorporated to the membrane at the edge of the cell sheet at all time points, although strongly reduced in lamellipodia-forming cells. Adherens junctions and desmosomes, and respective connected actin and keratin cytoskeleton were also disturbed in lamellipodia-forming cells. We propose that altered subcellular localization of polycystin-1 and -2 as a result of stress will affect signaling and other cellular processes mediated by these proteins.

Animals↗
PubMed2004

Abnormal hepatocystin caused by truncating PRKCSH mutations leads to autosomal dominant polycystic liver disease.

Mutations in protein kinase C substrate 80K-H (PRKCSH), encoding for the protein hepatocystin, cause autosomal dominant polycystic liver disease (PCLD), which is clinically characterized by the presence of multiple liver cysts. PCLD has been documented in families from Europe (Netherlands, Belgium, Finland) as well as from the United States. In this article, we report results from extensive mutational analysis of the PRKCSH gene in a group of 14 PCLD families and 65 singleton cases of Dutch and Finnish descent with multiple simple liver cysts. We identified PRKCSH mutations in 12 families and in 3 sporadic cases. In 8 of 10 Finnish families we detected the 1437+2delTG splice-site mutation. In Dutch families, we found 2 other mutations that affect correct splicing of PRKCSH: 292+1 G>C (2 families) and 1338-2 A>G (1 family). In another Dutch family, we detected a novel deletion (374-375delAG) in exon 6, predicting an abnormal shortened protein. Investigation of the carrier haplotypes identified a common founder chromosome in unrelated individuals in each of the 3 identified splice-site mutations. In 2 Finnish families with dominantly inherited PCLD, and in 62 of 65 sporadic cases with multiple simple liver cysts, we failed to demonstrate any PRKCSH mutation. This corroborates the notion that autosomal dominant PCLD is genetically heterogeneous. In conclusion, we propose that, on the basis of our results, genetic screening for PRKCSH gene mutations should be limited to patients either with a positive family history for PCLD or who have severe polycystic liver disease.

Calcium-Binding Proteins↗
PubMed2004

Two-color multiplex ligation-dependent probe amplification: detecting genomic rearrangements in hereditary multiple exostoses.

Genomic deletions and duplications play an important role in the etiology of human disease. Versatile tests are required to detect these rearrangements, both in research and diagnostic settings. Multiplex ligation-dependent probe amplification (MLPA) is such a technique, allowing the rapid and precise quantification of up to 40 sequences within a nucleic acid sample using a one-tube assay. Current MLPA probe design, however, involves time-consuming and costly steps for probe generation. To bypass these limitations we set out to use chemically synthesized oligonucleotide probes only. The inherent limitations of this approach are related to oligonucleotide length, and thus the number of probes that can be combined in one assay is also limited. This problem was tackled by designing a two-color assay, combining two sets of probes, each amplified by primers labeled with a different fluorophore. In this way we successfully combined 28 probes in a single reaction. The assay designed was used to screen for the presence of deletions and duplications in patients with hereditary multiple exostoses (HME). Screening 18 patients without detectable point mutations in the EXT1 and EXT2 genes revealed five cases with deletions of one or more exons: four in EXT1 and one in EXT2. Our results show that a two-color MLPA assay using only synthetic oligonucleotides provides an attractive alternative for probe design. The approach is especially suited for cases in which the number of patients to be tested is limited, making it financially unattractive to invest in cloning.

Chromosome Aberrations↗
PubMed2004

Large deletions in the polycystic kidney disease 1 (PKD1) gene.

Since identification of the genes mutated in patients with Autosomal Dominant Polycystic Kidney Disease, PKD1 and PKD2, a large number of different germ line mutations in both genes have been found by conventional PCR-based mutation detection methods. Nevertheless, in approximately 40% of the PKD1 families the disease-causing mutation remains to be elucidated. Complex germ line rearrangements are often not detectable by these standard diagnostic techniques. To detect large deletions in the PKD1 gene we performed Field Inversion Gel Electrophoresis (FIGE) followed by Southern blot analysis with probes selected in the unique and in the reiterated region of this gene. Our analysis revealed 4 deletions in 125 patients, indicating that large deletions in PKD1 are rare. Likely, patients with a deletion that also affects the neighbouring Tuberous Sclerosis Complex 2 (TSC2) gene will be diagnosed as patients with tuberous sclerosis. It was speculated that the exceptional polypyrimidine tract located in intron 21 and the small tract in intron 22, might play a role in the pathogenesis of ADPKD. Since this region is extremely difficult to amplify by PCR, we analysed the 5.8 kb BamHI fragment that contains the polypyrimidine tracts. We did not observe a disease-linked alteration although we detected two different rare variants either in PKD1 or in one of its homologues.

DNA Mutational Analysis↗
PubMed2004

Cancer risk in hereditary nonpolyposis colorectal cancer due to MSH6 mutations: impact on counseling and surveillance.

BACKGROUND & AIMS: Hereditary nonpolyposis colorectal carcinoma (HNPCC) is caused by a mutated mismatch repair (MMR) gene. The aim of our study was to determine the cumulative risk of developing cancer in a large series of MSH6 mutation carriers. METHODS: Mutation analysis was performed in 20 families with a germline mutation in MSH6. We compared the cancer risks between MSH6 and MLH1/MSH2 mutation carriers. Microsatellite instability (MSI) analysis and immunohistochemistry (IHC) were performed in the available tumors. RESULTS: A total of 146 MSH6 mutation carriers were identified. In these carriers, the cumulative risk for colorectal carcinoma was 69% for men, 30% for women, and 71% for endometrial carcinoma at 70 years of age. The risk for all HNPCC-related tumors was significantly lower in MSH6 than in MLH1 or MSH2 mutation carriers (P = 0.002). In female MSH6 mutation carriers, the risk for colorectal cancer was significantly lower (P = 0.0049) and the risk for endometrial cancer significantly higher (P = 0.02) than in MLH1 and MSH2 mutation carriers. In male carriers, the risk for colorectal cancer was lower in MSH6 mutation carriers, but the difference was not significant (P = 0.0854). MSI analysis in colorectal tumors had a sensitivity of 86% in predicting a MMR defect. IHC in all tumors had a sensitivity of 90% in predicting a mutation in MSH6. CONCLUSIONS: We recommend starting colonoscopic surveillance in female MSH6 mutation carriers from age 30 years. Prophylactic hysterectomy might be considered in carriers older than 50 years. MSI and IHC analysis are sensitive tools to identify families eligible for MSH6 mutation analysis.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Comparison between siblings and twins supports a role for modifier genes in ADPKD.

BACKGROUND: Autosomal-dominant polycystic kidney disease (ADPKD) is characterized by intrafamilial variability in renal disease progression, which could result from a combination of environmental and genetic factors. Although a role for modifier genes has been evidenced in mouse models, direct evidence in ADPKD patients is lacking. The analysis of variability in affected siblings and monozygotic (MZ) twins would help evaluate the relative contribution of environment and genetic factors on renal disease progression in ADPKD. METHODS: The difference in the age at end-stage renal disease (ESRD) and the intraclass correlation coefficient (ICC) were quantified in a large series of ADPKD siblings from western Europe and compared with the values obtained in a series of MZ ADPKD twins from the same geographic area. RESULTS: Fifty-six sibships (including 129 patients) and nine pairs of MZ twins were included. The difference in the age at ESRD was significantly higher in siblings (6.9 +/- 6.0 years, range 2 months to 23 years) than in MZ twins (2.1 +/- 1.9 years, range 1 month to 6 years; P = 0.02). Furthermore, the intraclass correlation coefficient was significantly lower in siblings than in MZ twins (0.49 vs. 0.92, respectively; P = 0.003). The intrafamilial difference in the age at ESRD was not influenced by gender. CONCLUSION: These data substantiate the existence of a large intrafamilial variability in renal disease progression in ADPKD siblings. The fact that the variability in siblings is in a significant excess of that found in MZ twins strongly suggests that modifier genes account for a significant part of this variability.

Adult↗
PubMed2003

Evaluation of diagnostic NOTCH3 immunostaining in CADASIL.

CADASIL is caused by mutations in the NOTCH3 gene. Although increasingly recognized as a disease entity, the diagnostic confirmation can be lengthy or inconclusive. Recently, NOTCH3 immunostaining of skin biopsy specimens has been introduced as a new diagnostic test. The aim of this study was to independently assess the diagnostic value of NOTCH3 immunostaining, and determine whether the degree of immunostaining correlates with other disease parameters. We determined NOTCH3 mutation carrier status in 62 symptomatic and asymptomatic individuals from 15 CADASIL families. Skin biopsy specimens of these individuals, as well as of a disease control group, were immunostained with NOTCH3 antibody and blindly analyzed by two independent observers to determine sensitivity and specificity. A semiquantitative NOTCH3 immunostaining score was correlated with clinical, genetic and MRI parameters. The sensitivity was 90.2% and 85.4%, respectively, for the two observers, the specificity 95.2% and 100%; both lower than previously reported. Certain NOTCH3 mutations may underlie false-negative results. False-positive results were found in a non-mutated control, and also in one disease control. There was no difference in immunostaining between symptomatic and asymptomatic NOTCH3 mutated individuals. Furthermore, the NOTCH3 immunostaining score did not correlate with clinical or MRI parameters. NOTCH3 immunostaining is a supportive, but not definitive, CADASIL diagnostic test, and should be interpreted in the context of clinical and radiological data. Confirmation by DNA analysis is requisite for positive results, and when there exists high clinical suspicion, also for negative results.

Adult↗
PubMed2003

Loss of CBP acetyltransferase activity by PHD finger mutations in Rubinstein-Taybi syndrome.

Disruption of one copy of the human CREB binding protein (CBP or CREBBP) gene leads to the Rubinstein-Taybi syndrome (RTS), a developmental disorder characterized by retarded growth and mental functions, broad thumbs, broad big toes and typical facial abnormalities. The CREB binding protein (CBP) is an essential transcriptional coactivator for many different transcription factors. CBP has the intrinsic ability to acetylate histones and other proteins, which is regarded as an important step in transcription activation. In vitro studies have shown that this enzymatic activity critically depends on the integrity of a plant homeodomain (PHD)-type zinc finger in the HAT domain of CBP. We therefore investigated whether PHD finger mutations are present in RTS patients. Mutational analysis of 39 patients revealed eight novel heterozygous mutations in the HAT domain of CBP, one of which alters a conserved PHD finger amino acid (E1278K), while a second mutation deletes exon 22, which encodes the central region of the PHD finger. Functional analysis of these RTS-associated PHD finger mutants showed that they lacked in vitro acetyltransferase activity towards histones and CBP itself and displayed reduced coactivator function for the transcription factor CREB. Importantly, in EBV-transformed lymphoblastoid cells from the exon 22 deletion patient we found approximately 50% less endogenous CBP HAT activity. These findings therefore underscore the functional importance of the PHD finger in vivo and imply that reduction of CBP HAT activity, as exemplified here by disruption of the PHD finger, is sufficient to cause RTS.

Acetyltransferases↗
PubMed2003

Incipient CADASIL.

BACKGROUND: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is caused by mutations in the NOTCH3 gene. Knowledge of disease expression in young adult NOTCH3 mutation carriers (MCs) is limited. OBJECTIVE: To characterize clinical, neuropsychological, and radiological status in NOTCH3 MCs younger than 35 years. DESIGN: Clinical characterization and blinded survey comparing MCs with non-MCs. SETTING: Referral center. PARTICIPANTS: Individuals younger than 35 years who were at a 50% risk of a NOTCH3 mutation, from our CADASIL database. Thirteen individuals, from 8 families, met the criteria. METHODS: Comprehensive clinical, genetic, neuropsychological, and radiological investigations. Magnetic resonance images were scored according to a standardized white matter hyperintensities rating scale. RESULTS: Six individuals, from 5 families, were MCs. Clinical symptoms consisted of migraine (with aura), stroke, and stroke-like episodes. We did not find evidence for psychiatric disturbances, functional disability, or cognitive dysfunction, compared with non-MCs. Radiologically, a characteristic magnetic resonance imaging lesion pattern emerged for all MCs. This comprised white matter hyperintensities in the anterior temporal lobes, the frontal lobes, and the periventricular frontal caps. CONCLUSIONS: Migraine (with aura) and stroke can present in NOTCH3 MCs younger than 35 years; however, more importantly, physical function and cognition are intact. Possible subtle cognitive dysfunction needs to be assessed in a larger study. White matter hyperintensities on magnetic resonance imaging are characteristic, and are consistently visualized from the age of 21 years and onward. Awareness of the clinical and radiological features of CADASIL in those younger than 35 years should increase early diagnosis and allow for customized counseling of young adults from families with CADASIL.

Adult↗
PubMed2003

Testing the test--why pursue a better test for Huntington disease?

In 1993, the gene mutation for Huntington disease (HD) was identified and testing became possible with a reliability of >99%, without the need for co-operation of relatives. In 1997, a systematic information program offered the mutation retest to individuals who had earlier received a linkage test result for HD, which has a residual uncertainty of 1-9%. The characteristics of 129 individuals tested by linkage analysis for HD are reported on, as well as the reasons for their reassessment by mutation testing. Three groups were compared: (1) people who were retested between 1993 and 1997, before this study had started, (2) people who were retested after we provided information, and (3) persons who refrained from retesting. Nearly half of the linkage-tested individuals were retested, with the exception of noncarriers with a residual risk of 1 or 2%. Of them, less than one out of five were retested. Carriers with a hopeful view on the future (BHS) and a better sense of well-being (GHQ) were more likely to have the retest. Female carriers were also more likely to have the retest before we contacted them. Noncarriers who were retested were more anxious (HADS) than noncarriers who refrained from the retest. Retestees were younger at the time of testing. No risk reversals were revealed by this study.

Adult↗