PUBLICATIONS 2009

 

Bhuiyan ZA, Jongbloed JD, van der Smagt J, Lombardi PM, Wiesfeld AC, Nelen M, Schouten M, Jongbloed R, Cox MG, van Wolferen M, Rodriguez LM, van Gelder IC, Bikker H, Suurmeijer AJ, van den Berg MP, Mannens MM, Hauer RN, Wilde AA, van Tintelen JP. Desmoglein-2 and Desmocollin-2 Mutations in Dutch Arrhythmogenic Right Ventricular Dysplasia/Cardiomypathy Patients: Results From a Multicenter Study. Circ Cardiovasc Genet. 2009 Oct 1;2(5):418-427.  IF 4.930.     

Blok MJ, Van den Bosch BJ, Jongen E, Hendrickx A, de Die-Smulders CE, Hoogendijk JE, Brusse E, de Visser M, Poll-The BT, Bierau J, de Coo IF, Smeets HJ.  The unfolding clinical spectrum of POLG mutations. J Med Genet. 2009 Nov;46(11):776-85. IF 5.535.

Bredenoord Annelien, Wybo Dondorp, Guido Pennings, Christine de Die-Smulders, Bert Smeets and Guido de Wert. Preimplantation genetic diagnosis for mitochondrial DNA disorders: ethical guidance for clinical practice. Eur J Hum Genet 2009 17:1550-1559. IF  4.003.

Gomez Garcia EB, Oosterwijk JC, Timmermans M, van Asperen CJ, Hogervorst FB, Hoogerbrugge N, Oldenburg R, Verhoef S, Dommering CJ, Ausems MG, van Os TA, van der Hout AH, Ligtenberg M, van den Ouweland A, van der Luijt RB, Wijnen JT, Gille JJ, Lindsey PJ, Devilee P, Blok MJ, Vreeswijk MP. A method to assess the clinical significance of unclassified variants (UVs) in the BRCA1 and BRCA2 genes based on cancer family history. Breast Cancer Res. 2009 Feb 6;11(1):R8. if 5.052

Hellebrekers DM, Lentjes MH, van den Bosch SM, Melotte V, Wouters KA, Daenen KL, Smits KM, Akiyama Y, Yuasa Y, Sanduleanu S, Khalid-de Bakker CA, Jonkers D, Weijenberg MP, Louwagie J, van Criekinge W, Carvalho B, Meijer GA, Baylin SB, Herman JG, de Bruïne AP, van Engeland M. GATA4 and GATA5 are Potential Tumor Suppressors and Biomarkers in Colorectal Cancer. Clin Cancer Res. 2009 Jun 15;15(12):3990-7. IF 6.250.

Kurey I, Kobets T, Havelková H, Slapnicková M, Quan L, Trtková K, Grekov I, Svobodová M, Stassen AP, Hutson A, Demant P, Lipoldová M.  Distinct genetic control of parasite elimination, dissemination, and disease after Leishmania major infection. Immunogenetics 2009 Sep;61(9):619-33. IF 2.793.

Lacbawan F, Solomon BD, Roessler E, El-Jaick K, Domené S, Velez JI, Zhou N, Hadley D, Balog JZ, Long R, Fryer A, Smith W, Omar S, McLean SD, Clarkson K, Lichty A, Clegg NJ, Delgado MR, Levey E, Stashinko E, Potocki L, Van Allen MI, Clayton-Smith J, Donnai D, Bianchi DW, Juliusson PB, Njølstad PR, Brunner HG, Carey JC, Hehr U, Müsebeck J, Wieacker PF, Polstra A, Hennekam RC, van den Boogaard MJ, van Haeringen A, Paulussen A, Herbergs J, Schrander-Stumpel CT, Janecke AR, Chitayat D, Hahn J, McDonald-McGinn DM, Zackai EH, Dobyns WB, Muenke M. Clinical Spectrum of SIX3-Associated Mutations in Holoprosencephaly: Correlation between Genotype, Phenotype, and Function. J Med Genet. 2009 Jun;46(6):389-98. IF 5.535.

Meex SJ, Weissglas-Volkov D, van der Kallen CJ, Thuerauf DJ, van Greevenbroek MM, Schalkwijk CG, Stehouwer CD, Feskens EJ, Heldens L, Ayoubi TA, Hofker MH, Wouters BG, Vlietinck R, Sinsheimer JS, Taskinen MR, Kuusisto J, Laakso M, de Bruin TW, Pajukanta P, Glembotski CC. The ATF6-Met[67]Val Substitution Is Associated With Increased Plasma Cholesterol Levels. Arterioscler Thromb Vasc Biol. 2009 Sep;29(9):1322-7. IF 6.858.

Melotte V, Lentjes MH, van den Bosch SM, Hellebrekers DM, de Hoon JP, Wouters KA, Daenen KL, Partouns-Hendriks IE, Stessels F, Louwagie J, Smits KM, Weijenberg MP, Sanduleanu S, Khalid-de Bakker CA, Oort FA, Meijer GA, Jonkers DM, Herman JG, de Bruïne AP, van Engeland M.  N-Myc Downstream-Regulated Gene 4 (NDRG4): A Candidate Tumor Suppressor Gene and Potential Biomarker for Colorectal Cancer. J Natl Cancer Inst. 2009  Jul 1;101(13):916-27. IF 14.933.

Mosterd K, Sommer A, van Marion A, Lacko M, Herbergs J, de Bondt BJ, van Steensel MA, Kelleners-Smeets NW. Destructive basal cell carcinoma in a patient with basal cell nevus syndrome and an interstitial deletion of chromosome 9q22. Dermatol Surg. 2009 Dec;35(12):2051-3. IF 2.102.

Nemes A, Geleijnse ML, Sluiter W, Vydt TC, Soliman OI, van Dalen BM, Vletter WB, ten Cate FJ, Smeets HJ, de Coo RF. Aortic distensibility alterations in adults with m.3243A>G MELAS gene mutation. Swiss Med Wkly. 2009 Feb 21;139(7-8):117-20. IF 1.310.

Poelmans G, Engelen JJ, Van Lent-Albrechts J, Smeets HJ, Schoenmakers E, Franke B, Buitelaar JK, Wuisman-Frerker M, Erens W, Steyaert J, Schrander-Stumpel C. Identification of novel dyslexia candidate genes through the analysis of a chromosomal deletion. Am J Med Genet B Neuropsychiatr Genet. 2009 Jan 5;150B(1):140-7.  IF 4.224     

van Rijsingen Ingrid A.W. van, Johanna F. Hermans-van Ast, Yvonne H.J.M. Arens, Simon M. Schalla, Christine E.M de Die-Smulders, Arthur van den Wijngaard and Yigal M. Pinto. Hypertrophic cardiomyopathy family with double-heterozygous mutations; does disease severity suggest double-heterozygosity? Neth Heart J 2009 dec;17(12). IF nog niet bekend (jong tijdschrift)

Roessler E, Lacbawan F, Dubourg C, Paulussen A, Herbergs J, Hehr U, Bendavid C, Zhou N, Ouspenskaia M, Bale S, Odent S, David V, Muenke M The full spectrum of holoprosencephaly-associated mutations within the ZIC2 gene in humans predicts loss-of-function as the predominant disease mechanism. Hum Mutat. 2009 Apr;30(4):E541-54. IF 6.273.   

Roessler E, El-Jaick KB, Dubourg C, Vélez JI, Solomon BD, Pineda-Alvarez DE, Lacbawan F, Zhou N, Ouspenskaia M, Paulussen A, Smeets HJ, Hehr U, Bendavid C, Bale S, Odent S, David V, Muenke M. The mutational spectrum of holoprosencephaly-associated changes within the SHH gene in humans predicts loss-of-function through either key structural alterations of the ligand or its altered synthesis. Hum Mutat. 2009 Oct;30(10):E921-35. IF 6.273.

Souren NY, Paulussen AD, Steyls A, Loos RJ, Brandão RD, Gielen M, Smeets HJ, Beunen G, Fagard R, Derom C, Vlietinck R, Geraedts JP, Zeegers MP. Parent-of-origin specific linkage and association of the IGF2 gene region with birth weight and adult metabolic risk factors. Int J Obes (Lond). 2009;33(9):962-70. IF 3.640

Spaans F, Faber CG, Smeets HJ, Hofman PA, Braida C, Monckton DG, de Die CE. Encephalopathic attacks in a family co-segregating myotonic dystrophy type 1, an intermediate Charcot-Marie-Tooth neuropathy and early hearing loss.  J Neurol Neurosurg Psychiatry. 2009 Sep;80(9):1029-35. IF 3.857. 

Stevens SJ, Smeets EE, Blom E, van Uum CM, Albrechts JC, Herbergs J, Janssen JW, Engelen JJ. Identical cryptic partial monosomy 20pter and trisomy 20qter in three adult siblings due to a large maternal pericentric inversion: Detection by MLPA and breakpoint mapping by SNP array analysis. Am J Med Genet A. 2009 Sep 1; 149A(10):2226-2230. IF 2.555

Tienen FH van, Laeremans H, van der Kallen CJ, Smeets HJ.Wnt5b stimulates adipogenesis by activating PPARgamma, and inhibiting the beta-catenin dependent Wnt signaling pathway together with Wnt5a. Biochem Biophys Res Commun. 2009 Sep 11;387(1):207-11. IF 2.648.

van Tintelen JP, Van Gelder IC, Asimaki A, Suurmeijer AJ, Wiesfeld AC, Jongbloed JD, van den Wijngaard A, Kuks JB, van Spaendonck-Zwarts KY, Notermans N, Boven L, van den Heuvel F, Veenstra-Knol HE, Saffitz JE, Hofstra RM, van den Berg MP. Severe cardiac phenotype with right ventricular predominance in a large cohort of patients with a single missense mutation in the DES gene. Heart Rhythm. 2009 Nov;6(11):1574-83. IF 4.444.

Vanhoutvin SA, Troost FJ, Kilkens TO, Lindsey PJ, Hamer HM, Jonkers DM, Venema K, Brummer RJ. The effects of butyrate enemas on visceral perception in healthy volunteers. Neurogastroenterol Motil. 2009 Sep;21(9):952-e76. IF 3.364.

Vanhoutvin SA, Troost FJ, Hamer HM, Lindsey PJ, Koek GH, Jonkers DM, Kodde A, Venema K, Brummer RJ. Butyrate-induced transcriptional changes in human colonic mucosa. PLoS One. 2009 Aug 25;4(8):e6759. IF ?

Verstraeten VL, Caputo S, van Steensel MA, Duband-Goulet I, Zinn-Justin S, Kamps M, Kuijpers HJ, Ostlund C, Worman HJ, Briedé JJ, Le Dour C, Marcelis CL, van Geel M, Steijlen PM, van den Wijngaard A, Ramaekers FC, Broers JL. The R439C mutation in LMNA causes lamin oligomerisation and susceptibility to oxidative stress. J Cell Mol Med. 2009 May;13(5):959-71. IF 6.807

van der Zwaag PA, Jongbloed JD, van den Berg MP, van der Smagt JJ, Jongbloed R, Bikker H, Hofstra RM, van Tintelen JP. A genetic variants database for arrhythmogenic right ventricular dysplasia/cardiomyopathy. Hum Mutat. 2009 Sep;30(9):1278-83. IF 7.033 .

 

POSTERS

ESHG

 Myotonic dystrophy: Complex repeats in a complex disorder
C. Braida1, J. Couto1, F. Morales1,2, P. Cuenca2, T. Ashizawa3, A. Wilcox4, D. E. Wilcox4, J. Mandel5, H. Radvanyi6, F. Niel7, M. Koening5, C. Lagier-Touren5, C. Faber8, H. J. M. Smeets9, P. A. Hofman10, C. E. M. de Die-Smulders11, F. Spaans8, D. G. Monckton12; 1University of Glasgow, Faculty of Biomedical and Life Sciences, Glasgow, United Kingdom, 2Instituto de Investigaciones en Salud, Universidad de Costa Rica, San José, Costa Rica, 3Department of Neurology, University of Texas Medical Branch, Galveston, TX, United States, 4Scottish Muscle Network, Ferguson- Smith Center for Clinical Genetics, Yorkhill Hospital, Glasgow, United Kingdom, 5Institut de Génétique et de Biologie Moléculaire et Cellulaire, Strasbourg, France, 6Laboratoire de Biochimie et Génétique Moléculaire, Hôpital Ambroise Paré, Boulogne, France, 7CHU Bordeaux, Fédération des Neurosciences  Cliniques, Hôpital Pellegrin, Bordeaux, France, 8Department of Clinical Neurophysiology, University Hospital Maastricht, Maastricht, The Netherlands, 9Department of Genetics and Cell Biology, Maastricht University, Maastricht, The Netherlands, 10Department of Radiology, University Hospital Maastricht, Maastricht, The Netherlands, 11Department of Clinical Genetics, University Hospital Maastricht, Maastricht, The Netherlands, 12Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
Myotonic dystrophy is an extremely variable disorder. Ages of onset vary from birth to old age and the symptoms range from mild to severely debilitating and life threatening. Although primarily neuromuscular, the precise array of symptoms observed in any one patient varies dramatically. Myotonic dystrophy type 1 is caused by the expansion of an unstable CTG repeat with patients typically inheriting from 50 to several thousand copies of the repeat. In general, longer alleles are associated with more severe symptoms and an earlier age of onset. However, explanations for the additional symptomatic variability not accounted for by repeat length have remained enigmatic. In order to try and understand symptomatic variation in myotonic dystrophy we have been analysing an unusual family in which the typical myotonic dystrophy symptoms are accompanied by an intermediate Charcot- Marie-Tooth peripheral neuropathy, acute encephalopathic attacks and deafness. We have determined that in addition to the typical CTG repeat expansion, this family has a complex repeat expansion at the 3’ end of the array comprised of CGG, CCG and CTG repeats These variant repeats presumably mediate the additional symptoms by anRNA gain of function analogous to that observed in fragile-X associated remor ataxia syndrome. We have also determined that similar uch variant repeats are observed in other myotonic dystrophy families and appear to be associated with decreased genetic instability and less severe symptoms. Notably, variant repeats are clustered at the 3’ end of the array and have not been detected at the 5’ end of the array. More bizarrely, variant repeats in some families appear to have arisen de novo. The occurrence of such de novo base substitutions reveals a mutation frequency several orders of magnitude greater than previously observed at any human loci and further extends our knowledge of the unusual sequence properties of expanded repeats.

The challenge of prenatal and preimplantation genetic diagnosis of mitochondrial disorders

C. de Die-Smulders, H. Smeets; University Hospital Maastricht, Department of Clinical Genetics, Maastricht, The Netherlands.
Mitochondrial diseases are caused by defects in the oxidative phosphorylation. They can be caused by mutations in nuclear or mitochondrial DNA (mtDNA) encoded genes. Mutation analysis of nuclear genes in prenatal (PND) or preimplantation genetic diagnosis (PGD) is routine. Pitfalls do occur in biochemical analysis in PND. Mutations inthe mtDNA lead to a wide spectrum of diseases with very variable clinical expression. They are transmitted exclusively maternally and are usually heteroplasmic. Severity of symptoms is partially determined by mutation load. PND or PGD for mtDNA mutations is complex and experience is limited. Prerequisites for reliable PND of mtDNA mutations have been formulated by Poulton and Turnbull (2000) and include: 1. a close correlation between mutation load and disease manifestation 2. no significant time-dependent changes in mutation load 3. a uniform distribution of mutation load in different tissues. These criteria also apply for PGD. For genetic counseling one may subdivide the mitochondrial mutations in 5 categories: 1 de novo mutations. Recurrence risk is low and PND or PGD can be offered for reassurance. 2. Inherited stable mutations, such as the m.8993T>G/C mutations (leading to NARP/Leigh syndrome). Outcome is favourable for this mutation when the mutation load is < 60%, while mutation load >90% is associated with a bad prognosis. Prediction of severity in the grey zone (60-90%) is difficult, but a tendency for percentages at the extremes has been observed in oocytes, which would favour conclusive results. PND was offered more than 10 times. PGD for the m.8993T>G mutation has been reported once. 3. Inherited unstable mutations. The classical example is the m.3243A>G (MELAS) mutation. There is a certain correlation between mutation load and clinical severity but individual exceptions exist. It is impossible to define a completely safe lower threshold. A limited number of PNDs have been carried out. Mutant load was found to be fairly stable in CVS and amniotic cells. Oocytes and foetuses of carrier women can be without mutant load, the number dependent on the mutation load of the carrier. PGD for the 3243A>G mutation was carried out by our group (unpublished results). Mutation load showed a broad range between embryos, but was equal in the blastocysts of one embryo. Some embryos had a fairly low mutation load. 4. Rare mutations with unknown outcome. Insufficient information is available for reliable predictions. 5. Homoplastic mutations. PND or PGD is useless as 100% of the mtDNA is mutated. In conclusion, assessment of mtDNA mutation load in chorionic villi, amniotic cells or blastocysts is quite accurate nowadays and prelimi nary data show that the mutation percentage is stable at different time points in pregnancy or in different cells of one embryo. However, PND for mitochondrial mutations is complicated by interpretation of test results, particularly in case of intermediate results. PGD is probably a more acceptable option to exclude or reduce the risk of a severely affected child, but experience is still very limited.  

Paternal repeat length instability of myotonic dystrophy type 1pre- and protomutations
M. M. Gerrits
1, C. E. M. de Die - Smulders1,2, C. G. Faber1, M. J. Blok1,2, H. J. M. Smeets1,2; 1Academic Hospital Maastricht, Maastricht, The Netherlands, 2Research Institute GROW, Maastricht University, Maastricht, The Netherlands. Myotonic dystrophy type 1 (DM1) is an autosomal dominant disorder, and the most common form of muscular dystrophy in adults. The molecular basis of DM1 lies in the instability of a CTG repeat in the 3’ UTR of the DM1 protein kinase gene. Small expanded DM1 alleles are usually unstable and often increase in number in successive generations. Here we evaluated the risk onexpansion of an additional 22 pre- (37-50 CTG repeats) and 41 protomutation (50-80 repeats) in relation to sex and repeat length in DM1 transmitting parents for 63 DM1 parent-child pairs (33 males, 30 females). CTG-repeat lengths in the parents and children were determined by PCR and Genescan analysis. For the transmitting males, 23/33 (70%) repeats expanded to a full mutation upon transmission, whereas 5/33 (15%) repeats were stable and 5/33 (15%) slightly increased. For the transmitting females, these values were 5/30 (17%), 17/30 (57%) and 6/30 (20%), respectively. When the results were subdivided by repeat length, only one (1/8, 13%) transmitting male gave rise to a full mutation in the offspring in the premutation range, and 9/11 (82%), 6/6 (100%) and 7/8 (86%) in the protomutation ranges, 51-60, 61-70 and 71-80 repeats, respectively. For the transmitting females, full mutations were only seen in the 71-80 repeat range, and in 5/6 (83%) offspring. In conclusion, paternal repeat length instability occurs frequently and mainly between 51-80 repeats, while maternal repeat length instability occurs infrequently and only above 70 repeats. This observation has implications for genetic counseling.  

A possible new Dutch founder in three families with hypertrophic cardiomyopathy, a more malignant phenotype of the MYL2 mutation E22K
Y. Arens1, M. Schouten1, W. Hermans-van Ast1, D. Huveners1, D. Dooijes2, J  Sels3, D. Donker1, Y. Pinto4, P. Helderman1, A. van den Wijngaard1; 1Maastricht Medical Center, Maastricht, Theetherlands, 2Erasmus University Medical Center, Rotterdam, The Netherlands, 3Catharina Ziekenhuis, Eindhoven, The Netherlands, 4Amsterdam Medical Center, Amsterdam, The
Netherlands.
Familial hypertrophic cardiomyopathy (HCM) is a genetic cardiac disorder, which affects 1 in 500 subjects. HCM is characterized by left ventricular hypertrophy, arrhythmias and sudden death. Mutations in the Myosin Light Chain 2 gene (MYL2) are rare ( 4%) and disease phenotype is described as mild. We present three large Dutch families with MYL2 mutation E22K to demonstrate that the phenotype does also include severe hypertrophy and sudden death at a young age. DNAanalysis in 11 siblings of family 1, 11 siblings of family 2, and 2 of family 3 showed an E22K mutation (c.64G>A) in MYL2. Other sarcomeric genes were analysed and no mutations were found. There were 2 sudden deaths in family 1. In family 2 the index person had severe HCM and ICD. In family 3 sudden death was reported. The families reported in literature with the MYL2 mutation E22K showed late onset moderate septal hypertrophy with benign disease course and good prognosis. Our families the disease showed a far more malignant character. Because of the rarity of MYL2 mutations, haplotype analysis of the MYL2 region was performed to link the three families. The families shared a similar haplotype implying they are related. E22K might therefore be a founder mutation. We’ll perform genealogy to establish the relationship between the three families to calculate the family tree mortality ratio of this mutation. These findings are relevant in the counseling and treatment of other patients carrying this mutation.  

Recurrent progressive non-immune hydrops foetalis: better think of mucopolysaccharidoses type VII/ beta-glucuronidase deficiency/ GUSB gene defect
S. G. M. Frints1,2, Y. Arens1,2, J. Bakker3, J. Huijmans4, S. Stevens5, J. Engelen5, R. Blok2,6, J. Nijhuis7, C. Willekes7, A. ten Haaft8, Y. Henskens8, A. Cleven9, M. Baldewijns9, W. Lissens10, C. E. M. de Die-Smulders1,2;
1Prenatal Diagnosis and Therapy, Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands, 2School for Oncology and Developmental Biology, GROW, University of Maastricht, Maastricht, The Netherlands, 3Laboratory for Inherited Metabolic Disorders, Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands, 4Department of Clinical Genetics, Erasmus University Medical Center, Rotterdam, The Netherlands, 5Cytogenetic Laboratory, Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands, 6DNA laboratory, Department of Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands, 7Prenatal Diagnosis and Therapy, Department of Obstetrics & Gynaecology, Maastricht University Medical Center, Maastricht, The Netherlands, 8Department of Hematology, Maastricht University Medical Center, Maastricht, The Netherlands, 9Department of Pathology, Maastricht University Medical Center, Maastricht, The Netherlands, 10Center of Medical Genetics, University Hospital Brussels, Brussels, Belgium.
Mucopolysaccharidosis type VII/ beta-glucuronidase is an autosomal recessive lysosomal storage disease. The phenotype is highly variable, ranging from severe lethal non-immune hydrops foetalis to mild forms with survival into adulthood. We describe a non-consanguineous couple, first presented with non-immune hydrops foetalis, ascites and clubfeet in the fourth pregnancy at 20 weeks of gestation. They had one early miscarriage and two healthy children. Prenatal diagnosis showed (familial) 45,XX, der(14;15)(q10;q10) karyotype with de novo RAI1 locus duplication MLPA detected. Uniparental disomy 14 and 15 were excluded. The pregnancy was terminated at 26 weeks of gestation. Lysosomal enzyme investigations in amniotic fluid were not conclusive and 5% recurrence risk for hydrops foetalis was counselled. In the fifth pregnancy prenatal diagnosis revealed a 46,XY karyotype without RAI1 duplication. However, ultrasound investigation showed again a progressive hydrops foetalis. Cultured amniocytes from the fourth pregnancy combined with amniotic fluid investigation of the fifth pregnancy using glycosaminoglycan electrophoresis and lysosomal enzyme activity measurements confirmed beta-glucuronidase deficiency in both. Cord blood investigation revealed prominently vacuolated monocytes, with basophilic inclusions in lymphocytes (Gasser cells) and metachromatic granules (Alder-Reilly bodies) in granulocytes. Electron microscopic investigations showed vacuolated Hofbauer cells in the placenta and foamy macrophages in spleen, liver, and other organs. Greatly reduced activity of beta-glucuronidase in cultured skin fibroblasts reconfirmed the diagnosis of MPS type VII and GUSB DNA analysis is still pending. We can conclude that recurrent massive non-immune hydrops foetalis is likely autosomal recessive with 25% recurrence risk in which lysosomal storage disorders need to be investigated.  

Genetic cancer risk modifiers in hereditary breast and/or ovarian cancer families
R. D. Brandão1,2, M. J. Blok1,2, J. Harssel1, A. Romano1,2, C. Schrander-Stumpel1,2, J. Geraedts1,2, M. Zeegers1,3, E. B. Gómez García1,2;
1Maastricht University Hospital, Maastricht, The Netherlands, 2GROW - School for Oncology and Developmental Biology, Maastricht, The Netherlands, 3School of Medicine, University of Birmingham, Birmingham, United Kingdom.
Introduction: Variability observed in penetrance, age of onset, and site of the tumor, both among and within BRCA families suggests that, other, low-penetrance, genetic variants modify the cancer risk. Objective: To study the effect of six polymorphisms, recently described as being risk modifiers of sporadic breast cancer (BC) or ovarian cancer (OC) in BRCA families. Methodology: We recorded the cancer history (tumor site, age of diagnosis) of 548 women (293 carriers, 255 non-carriers) from 125 BRCA families (72 BRCA1, 53 BRCA2). The polymorphisms genotyped were: +331G/A and PROGINS, localized in the progesterone receptor gene, CASP8 D302H, CASP8 -652 6Nins/del, FGFR2 (rs2981582) and TNRC9 (rs3803662). Familial clustering was taken into account in the statistical analyses. Results: Two polymorphisms modified the risk of OC in BRCA1 and BRCA2 families: +331 G/A heterozygous genotype increased the risk (OR:2.41, 95%CI: 0.98-5.96, p=0.056), while FGFR2 had a protective effect (OR:0.52, 95%CI: 0.28-0.96, p= 0.037). FGFR2 was also significantly associated with increased risk of bilateral BC (OR:2.67, 95%CI: 1.45-4.92, p=0.002), whereas CASP8 -652 6Nins/del had a trend towards a protective effect, restricted to BRCA1 mutation carriers (OR:0.71, 95%CI:0.48-1.05, p=0.084). Furthermore, PROGINS was significantly associated with BC among the BRCA2 non-carriers (phenocopies) (OR:8.17, 95%CI: 2.17-30.76, p=0.002). Conclusions: We have found evidence that certain polymorphisms involved in hormone mediated cell proliferation and apoptosis modify the BC and OC risks in BRCA families. This may be relevant for an individual assessment of the most suitable preventive option, among those currently available, for each of those patients.  

 

ASHG

Searching for mitochondrial mutations involved in age-related hearing impairment.
E. Fransen1, S. Bonneux1, E. Van Eyken1, L. Van Laer1, HJM. Smeets2, G. Van Camp1. 1) Center for Medical Genetics, University of Antwerp, Antwerp, Belgium; 2) Department of Genetics and Cell Biology, Clinical Genetics, Maastricht University, Maastricht, The Netherlands. Age-related hearing impairment (ARHI) is a condition whereby hearing acuity declines with ageing. Although this occurs in every individual, some persons are more severely affected than others. About half of the phenotypic variance is attributable to genetic factors. We have previously identified SNPs within two nuclear genes (GRHL2 and GRM7) that are associated with ARHI, and reported significant linkage between the ARHI phenotype and chromosomal region 8q24, but much of the variance remains unexplained Mitochondrial (mt) DNA mutations have been implicated in several ageing processes, and certain forms of nonsyndromic hearing loss are caused by mitochondrial mutations. In this study we explore whether mt variation contributes to ARHI. We have fully sequenced the 16 kb mt genome in 199 good-hearing and 200 bad-hearing persons, using the GeneChip Human Mitochondrial Resequencing Array (Affymetrix). Of the 399 participants, 369 could be classified into one of the European mt Haplogroups. No association was found between Haplogroup and affection status. When accounting for known ARHI risk factors (occupational noise, smoking, bmi, alcohol consumption, solvent exposure), no association was found either. With regard to the revised Cambridge Reference Sequence (rCRS, Genbank Accession Number AC_000021), a total of 818 distinct mutations were found across the dataset. More than half of these mutations (451 = 55%) were found in only one individual. The average number of mutations per individual was not significantly different between cases and controls, even when weighting the mutations according to conservation. For the more common variants, a Fisher-exact test was used to screen for allele frequency differences between cases and controls. The most significant signal was observed for position 10876. Seven of the cases carry a G at this position instead of a C, which was not observed among any of the controls. (p=0.01). Apart from the C10876G variant, we found eight additional variants with p-values between 0.01 and 0.1, that were all specific to subhaplogroup U2e. Six of the 9 disease-associated variants are located within the protein-coding region, but none of them alters the protein sequence. One of the variants belongs to a tRNA gene, while the last variant is part of the control region (D-loop).  

CHIP-based sequence analysis of 34 cardiomyopathy genes in 250 patients reveals new genes involved in HCM and DCM and multiple pathogenic mutations in single patients.

H. Smeets1,2, W. Van Dijk1, A.Stassen1, P. Lindsey1,2, Y. Arens1, P. Helderman1, C. Marcelis3, J. Van der Smagt4, S. Heymans2,5, P. Volders2.5, R. Jongbloed1,2, A. van den Wijngaard1.
1) Dept Clinic Genet, Maastricht UMC, Maastricht, The Netherlands; 2) Research School CARIM, Univ Maastricht, Maastricht, The Netherlands; 3) Dept Clinic Genet, UMC St. Radboud, Nijmegen, The Netherlands; 4) Dept Clinic Genet, Utrecht UMC, Utrecht, The Netherlands; 5) Dept Cardiol, Maastricht UMC, Maastricht, The Netherlands. Inherited cardiomyopathy is a frequent cardiac disease with a prevalence of 1:500 (HCM) to 1: 2500 (DCM). Due to the large amount of genes involved, the clinical heterogeneity and the laborious screening methods, it is difficult to unravel rapidly the genetic cause in all cases. Current diagnostic screening solves only 60-70% of the families by testing a limited number of genes in an often time-consuming sequential fashion and usually stops when a pathogenic mutation has been identified. However, double pathogenic mutations seem to be present in 5-10% of the familial cases. In order to create a fast, parallel genetic screening pipeline for inherited cardiomyopathy, we designed a resequencing array (CardioCHIP) covering 34 genes in duplicate (300Kb). We included genes known to be involved in DCM, HCM, LVNC and LGMD and candidate genes based on their presence in the sarcomere and Z-disc. All exons and flanking introns (38bp) were included on the CardioCHIP, covering the heart- and muscle-specific RNA-isoforms. The 5’UTR and 3’UTR regions and, for a selection of genes, the promoter regions were included as well. The genes, which were interrogated by the Cardio- CHIP, were amplified in 152 LR-PCR covering 395 exons, resulting in a sequence of 146.541 nucleotides. So far, 250 patients were sequenced for all 34 cardiomyopathy genes. The mutation detection rate is around 99% and about 98% of the novel exonic variants can be confirmed by conventional sequence analysis. In addition to mutations detected in the 13 genes routinely tested for HCM or DCM, we identified mutations in the 21 additional genes, some of which were the first for those new candidate genes. We identified in several patients up to 4 pathogenic mutations, involved in different pathogenic processes. Our data indicate that parallel analysis of multiple genes is a prerequisite for genetic testing in HCM and DCM to identify rapidly the genetic cause. Due to the potential presence of multiple mutations and to prevent misinterpretation, it is essential to test all genes in all patients and not proceed solely on the first genetic defect identified, as is the current practice. This is also the case for the relatives at risk, which would imply that for proper prognosis and preventive treatment all candidate genes should be tested in parallel for each individual.  

Holoprosencephaly mutations in the Dutch population.
A.D.C. Paulussen1,C. Schrander Stumpel1,2, J. Herbergs1, C. de Die Smulders1, S. Stegmann1, Y. Arens1, M. Vreeburg1, G. Tan-Sindhunata6, M. Collee3, A. van Haeringen4, A. Hoogeboom5, K. Lichtenbelt3, A. Lachmeijer6, W. Kerstjens Frederikse7, M.L. Kwee6, J.A. Maat Kievit5, G. Mancini5, M. Simon5, I. Stolte Dijkstra7, H.J. Smeets1,2. 1) Dept Clinical Genetics, Maastricht University Medical Center, Maastricht, Netherlands; 2) Research Institute Growth and Development (GROW), University Maastricht, Maastricht, The Netherlands; 3) Department of Clinical Genetics, University Medical Center, Utrecht, The Netherlands; 4) Department of Human and Clinical Genetics, Leiden University Medical Center, The Netherlands; 5) Department of Clinical Genetics, Erasmus University Medical Center, Rotterdam, The Netherlands; 6) Department of Clinical Genetics, VU University Medical Center, Amsterdam, The Netherlands; 7) Department of Genetics, University Medical Center Groningen, Groningen, The Netherlands. Holoprosencephaly (HPE) is a severe malformation of the brain that involves abnormal formation and septation of the developing central nervous system. The prevalence is 1:250 during early embryogenesis, but the live born prevalence is only 1:16,000. The etiology of HPE is extremely heterogeneous and can include both a teratogenic and/or genetic basis. We studied four genes known to be involved in HPE, namely SHH, ZIC2, SIX3 and TGIF by sequence and MLPA analysis. A series of in total 80 sporadic and familial HPE cases with a variable clinical spectrum has been analysed. We detected 19 pathogenic mutations (24%) in total, of which 3 in SHH, 7 in ZIC2 and 9 in SIX3. Only one mutation (Alanine-tract expansion in ZIC2) was reported previously and detected twice in this population, all others were novel. Two mutations were complete gene deletions (one SIX3, one ZIC2 deletion) of which the deletion sizes were further characterized using the 250K Nsp I Affymetrix SNP array. The ZIC2 deletion was too small to be detected with this array, the SIX3 deletion also comprised the SIX2 gene and was approximately 1,37 Mb in size. The familial mutations displayed considerable heterogeneity in clinical expression, which makes it difficult to establish genotype-phenotype correlations and indicates that although the mutation detected is essential, it is not the only factor involved. Additional environmental factors and modifier genes will play a role as well. HPE development is probably a multihit process, which implicates more genes, illustrating the importance of further identification of new genes or risk-factors.  

Homozygosity mapping reveals new genes and gene defects in consanguineous families with OXPHOS disease.
M. Gerards1,2, B. van den Bosch1,2, W. Sluiter3, E. de Wit3, K. Schoonderwoerd4, A. van der Kooi5, I. de Coo6, H. Smeets1,2. 1) Dept Clinic Genet, Maastricht UMC, Maastricht, Limburg, Netherlands; 2) Research School GROW, Univ Maastricht, Maastricht, The Netherlands; 3) Dept Biochem, Mitochondrial Research Unit, Erasmus MC, Rotterdam, The Netherlands; 4) Dept Clin Genet, Erasmus MC, Rotterdam, The Netherlands; 5) Dept Neurol, Academic Medical Center, Amsterdam, The Netherlands; 6) Dept Neurol, Erasmus MC, Rotterdam, The Netherlands. Mitochondrial or OXPHOS disorders are clinically and genetically highly heterogeneous, making the identification of the underlying gene defect a major challenge. Classification based on clinical or biochemical criteria or gene expression profiling remains difficult and only applicable to small subgroups of patients. Therefore, the most successful approach for finding the genetic defect still remains SNP-based homozygosity mapping and candidate gene analysis, as illustrated for 2 consanguineous families with OXPHOS disease. In the first family with 3 children affected with Leigh syndrome, a homozygous region of 11.5Mb on chromosome 20 was identified containing 8 mitochondrial genes. Patients were homozygous for an amino acid substitution (p.L159F) in C20orf7, an new assembly factor of OXPHOS Complex I. Blue native gel electrophoresis showed in blood a decrease to 30% of mature Complex I in patients compared to controls indicating the pathogenic mechanism of this mutation. A homozygous region on chromosome 1 containing 4 mitochondrial genes was detected in the second family with 3 children with progressive cerebellar ataxia. Mutation screening of CABC1 (the chaperone, ABC1 activity of bc1 complex homologue gene) revealed a homozygous nonsense mutation (c.1042C>T, p.R348X). CABC1 is the homologue of the yeast COQ8 gene, which is involved in the ubiquinone biosynthesis pathway. An additional 4 patients with cerebellar ataxia were screened for mutations in the CABC1 gene. One patient was compound heterozygous for the same c.1042C>T mutation and had an additional nonsense mutation (c.1136T>A, p.L379X). The pathogenic role for both CABC1 mutations is evident as they either lead to a truncated protein missing important protein kinase motifs required for ATP binding or to nonsense mediated mRNA decay. We conclude that homozygosity mapping is the preferred method to identify pathogenic mutations in consanguineous families and maybe also in idividual patients.