Mutations Induce Severe Cardiomyopathy
The heart muscle makes the heart beat about seventy times per
minute, thus providing the entire body with oxygen and nutrients. Dysfunction
of the heart muscle may lead to cardiac arrhythmia, cardiac insufficiency, and
even heart failure.
In LVNC, a disease which was just discovered a few years
ago, the left ventricle of the heart resembles that of an embryo. Since the
disease can also occur in small children, scientists assumed it was a
developmental disorder of the heart muscle tissue.
Now, Dr. Klaassen and her colleagues have been able to show
that the disease is due to a genetic defect and is thus a familial disease. It
affects genes whose proteins are responsible for contraction and, thus, for the
pumping function of the heart muscle, i.e. genes encoding β-myosin heavy
chain, α-cardiac actin, and troponin T.
Genetic testing on individual families showed that the
probability of an affected parent passing on the gene mutations to his or her children
is 50 percent. “That is why gene testing of these families is so important,” Dr.
Klaassen said.
If a gene test turns out to be negative, the tested person
can be certain that he or she will not get LVNC. But if the test is positive, the
implication is not so clear. “As a consequence of the altered heart muscle
tissue, the affected person may develop functional myocardial impairment later
in life,” Dr. Klaassen explained.
However, a mutation in these genes need not inevitably lead
to myocardial insufficiency. “We examined a 70-year-old patient who did not show
any symptoms of the disease although she had the mutation,” the cardiologist
added. “Apparently, other genetic factors, as well as environmental factors,
like a healthy lifestyle, influence the manifestation of the disease.”
*Mutations in Sarcomere Protein Genes in
Left Ventricular Noncompaction
Sabine Klaassen, MD1,2*; Susanne
Probst, MSc1*; Erwin Oechslin, MD3;
Brenda Gerull, MD1, Gregor Krings, MD2; Pia Schuler, MD4;
Matthias Greutmann, MD4; David Hürlimann, MD4; Mustafa
Yegitbasi5, MD; Lucia Pons, MD6, Michael Gramlich, MD1;
Jörg-Detlef Drenckhahn, MD1; Arnd Heuser, MD1, Felix
Berger, MD2,5; Rolf Jenni, MD4; Ludwig Thierfelder, MD1,7
1)Max-Delbrück-Center for Molecular Medicine, Berlin, Germany; 2)Clinic
of Pediatric Cardiology, Charité, Humboldt University Berlin, Germany; 3)Adult
Congenital Cardiac Centre at Peter Munk Cardiac Centre, University Health Network/Toronto
General Hospital, Toronto, Canada; 4)Cardiovascular Center, Division
of Echocardiography, University Hospital Zürich, Zürich, Switzerland; 5)Department
of Congenital Heart Defects/Pediatric Cardiology, German Heart Institute
Berlin, Berlin, Germany; 6)Ospedale Regionale di Mendrisio Beata
Vergine, Mendrisio, Switzerland; 7)Helios Clinic Berlin-Buch,
Charité, Humboldt University Berlin, Germany
In a healthy heart, the left ventricle, LV (above right), the right ventricle (above left), and their atriums are surrounded by compact muscle tissue. (Picture: Sabine Klaassen/ Copyright: MDC)
In a patient with LVNC, sponge-like muscle tissue protrudes into the left ventricle (above right as indicated by arrows) and impairs the heart’s ability to pump blood. (Picture: Sabine Klaassen/ Copyright: MDC)
Barbara Bachtler
Press and Public Affairs
Max Delbrück Center for Molecular Medicine (MDC)
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