https://archiv.ub.uni-marburg.de/diss/z2012/1000/cover.png Molecularbiolobical screening of the CHRM2-gen in patients with dilated cardiomyopathy 2012-11-16 Zhang L, Hu A, Yuan H, Cui L, Miao G, Yang X, Wang L, Liu J, Liu X, Wang S, Zhang Z, Liu L, Zhao R und Shen Y. A missense mutation in the CHRM2 gene is associated with familial dilated cardiomyopathy. Circ Res, 2008; 102(11):1426–1432. Kühl U, Pauschinger M, Seeberg B, Lassner D, Noutsias M, Poller W und Schultheiss H-P. Viral persistence in the myocardium is associated with progressive cardiac dysfunction. Circulation, 2005; 112(13):1965–1970. Mobascher A, Rujescu D, Mittelstraß K, Giegling I, Lamina C, Nitz B, Brenner H, Fehr C, Breitling L P, Gallinat J, Rothenbacher D, Raum E, Müller H, Ruppert A, Hartmann A M, Möller H J, Gal A, Gieger C, Wichmann H E, Illig T, Dahmen N und Winterer G. Association of a variant in the muscarinic acetylcholine receptor 2 gene (CHRM2) with nicotine addiction. 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Proc Natl Acad Sci, 1977; 74(12):5463-5467. monograph Muscarinic acetylcholinreceptor Kongestive Herzmuskelkrankheit doctoralThesis Medical sciences Medicine Medizin 2012-07-09 urn:nbn:de:hebis:04-z2012-10003 ths Dr. Pankuweit Sabine Pankuweit, Sabine (Dr.) Straulino, Fabian Straulino Fabian CHRM2 Innere Medizin 2012 Publikationsserver der Universitätsbibliothek Marburg Universitätsbibliothek Marburg Die dilatative Kardiomyopathie (DCM) ist eine ätiologisch heterogene Erkrankung der Herzmuskulatur, die durch eine ventrikuläre Dilatation und eingeschränkte Pumpfunktion gekennzeichnet ist. Neben autoimmunen und infektiösen Faktoren spielen bei der Pathogenese der Erkrankung vor allem genetische Veränderungen eine Rolle. In den letzten Jahren konnten durch molekularbiologische Untersuchungen Mutationen in über 30 Krankheitsgenen bei Patienten mit DCM identifiziert werden. Neben Proteinen des Sarkomers und des Zytoskeletts zählen auch Rezeptorproteine und deren Regulatoren hierzu. Das CHRM2-Gen ist ein neues mögliches Krankheitsgen der DCM. Es befindet sich auf Chromosom 731q-35q und kodiert für den muskarinergen Acetylcholinrezeptor Typ 2 (m2AChR). Der m2AChR ist der vorherrschende muskarinerge Rezeptor am Herzen und vermittelt über sein Gi-Protein eine Reduktion der intrazellulären cAMP Konzentration. Dies senkt den Calciumeinstrom in die Myokardzelle und hat einen negativ inotropen und chronotropen Effekt. In einer Arbeit von Zhang et al. konnte bereits bei einer Familie mit familiärer DCM eine Missense-Mutation im m2AChR bei allen erkrankten Familienmitgliedern nachgewiesen werden. Ziel dieser Arbeit war es, weitere Mutationen in der kodierenden Region des CHRM2-Gens bei Patienten mit DCM zu identifizieren und einen möglichen Einfluss der Mutationen auf den klinischen Verlauf der Erkrankung zu untersuchen. Hierfür wurde aus Volblutproben von 337 an DCM erkrankten Patienten der kodierende Abschnitt des CHRM2-Gens mittels Polymeraserkettenreaktion (PCR) und single-stranded-conformation-polymorphism Gelelektrophorese (SSCP) molekularbiologisch untersucht. In der SSCP auffällige Proben wurden sequenziert. Anamnestische Daten der Patienten sowie die Ergebnisse klinisch-echokardiographischer Untersuchungen bei Einschluss der Patienten und im 1-Jahresverlauf liegen vor. In der untersuchten Patientengruppe konnten zwei neue heterozygote Missense-Mutationen sowie ein Polymorphismus identifiziert werden. Die Missense-Mutation G885A bewirkt einen Aminosäureaustausch von Valin zu Isoleucin an Position 231 im Rezeptorprotein. Durch die Mutation G1268C wird Glutamin durch Histidin an Position 358 ersetzt. Bei dem Träger dieser Mutation liegt eine familiäre Form der DCM vor und ein ebenfalls an DCM erkrankter Sohn des Indexpatienten konnte als weiterer Träger identifiziert werden. Hinsichtlich der echokardiographischen Daten, besonders im 1-Jahresverlauf, konnten bei keinem Mutationsträgern Unterschiede zu Patienten mit DCM ohne nachgewiesene Mutation gefunden werden. Die anschließende Untersuchung einer Kontrollgruppe aus 300 gesunden Blutspendern der Blutbank Marburg identifizierte keine weiteren Träger der Mutationen. Beide Mutationen bewirken eine Veränderung der Aminosäuresequenz in der dritten intrazellulären Schleife des m2AChR. Dieser Bereich ist für die Kopplung des Rezeptors an sein G-Protein und die Regulation der Rezeptordichte bzw. der Rezeptorfunktion von Bedeutung. Eine Auswirkung der Mutationen auf die intrazellulären Signaltransduktion und Calciumhomöostase ist denkbar. Insgesamt unterstützen die Ergebnisse dieser Arbeit die Rolle des CHRM2-Gens als weiteres Krankheitsgen der DCM. Die hier gezeigte Prävalenz von 0,6 % ist mit der Prävalenz von anderen etablierten Krankheitsgenen vergleichbar. Zum Verständnis der Rolle des CHRM2-Gens in der Pathogenese der DCM und um die Auswirkungen der Mutationen auf die Funktion des Rezeptorproteins abschließend zu klären, sind funktionelle Untersuchungen der mutierten Rezeptoren notwendig. Medizin opus:4509 Molekularbiologisches Screening des CHRM2-Gens bei Patienten mit dilatativer Kardiomyopathie Muscarinrezeptor Philipps-Universität Marburg Dilated cardiomyopathy (DCM) is a heterogeneous heart muscle disease characterized by ventricular dilatation and impaired function of the heart. Despite autoimmune and infectious factors genetic changes play a major role in the pathogenesis of this disease. In the last few years mutations in over 30 different genes were identified in patients with DCM. Most were found in genes coding for proteins of the sarcomere or cytoskeletal proteins but mutations in receptors or their regulatory proteins were detected as well. The CHRM2-gen is a potential new disease gene of DCM. It is localized on chromosome 731q-35q and is coding for the muscarinic acetlycholin receptor type 2 (m2AChR). The m2AChR is the main muscarinic receptor in the mammalian heart and mediates a reduction of the intracellular cAMP concentration through the Gi-protein. Calcium influx into the myocardial cell is reduced resulting in negative inotrope and chronotrope effects. In a study of Zhang et al. one missense mutation in the CHRM2-gene was found in all affected members of a family with familial DCM. The purpose of this study was to identify further mutations in the coding region of the CHRM2-gene in patients with DCM and to explore the influence of these mutations on the clinical course of the disease. Therefore we screened the coding region of the CHRM2-gen with polymerase chain reaction (PCR) and single-stranded-conformation-polymorphism gelelectrophoresis (SSCP) in 337 patients with DCM. The DNA of patients with conspicuous findings in the SSCP was analyzed by direct sequencing. Informations of an echocardiographic examination at the time of admission and at an one year follow-up are documented. In the investigated group of patients with DCM we could identify two new heterozygous missense mutations and one polymorphism in the CHRM2-gene. As a result of the mutation G885A the aminoacid valin is changed to isoleucin at position 231 of the receptor protein. The effect of the mutation G1268C is a substitution of glutamin by histidine at position 358. The diagnosis of familial DCM was confirmed for the carrier of this mutation because the diagnosis of DCM was established in one son of the indexpatient. The mutation G1268C was found in the DNA of the son as well. A correlation between the identified mutations and the results of the echocardiographic examination of the carriers, especially at the one year follow-up, could not be observed. In a following screening of 300 healthy blood donors from the Marburger Blutbank no further carriers of the mutations were found. The effect of both mutations is an aminoacid change at the third intracellular loop of the m2AChR. This area is important for the receptor-G-protein-coupling and for the regulation of the receptor concentration at the cell surface or rather the regulation of the receptor function. An influence on the intracellular signal transduction and calcium homeostasis is possible. Taken together, the results of this study support the role of the CHRM2-gene in the pathogenesis of DCM. A prevalence of 0,6 % is comparable with the prevalence of established disease genes in DCM. For a complete understanding of the role of the CHRM2-gen in the pathogenesis of DCM and to clarify the effect of the mutations on the function of the m2AChR further functional analysis of the mutated receptor is required. German application/pdf https://doi.org/10.17192/z2012.1000 Dilated cardiomyopathy, CHRM2 2012-11-16