Long-QT Syndrome
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Molecular Biology Of Long-QT Syndrome
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The last few years have witnessed a dramatic progress in our understanding of the molecular bases of congenital long QT syndrome (LQTS). In a landmark series of scientific articles in 1995, Dr. Mark Keating and colleagues at the Howard Hughes Medical Institute at the University of Utah reported the discovery of two genes causing LQTS. Subsequently, more genes have been identified.
These genes are responsible for maintaining electrical balance in the heart. Specifically, they are encoding ion channels subunits, or proteins associated to the ion channel subunits, which are involved in the generation of the cardiac action potential.
One need only to inherit one variant of these gene defects to have LQTS. However, about 40% of the families with LQTS have not yet been linked to any of the known genes. This means there are more genes to be identified yet.
The LQTS types are labelled LQT1 to LQT12. The LQT11 and LQT12 types have just been discovered.|
Type |
Gene |
Protein |
Chromosomal Locus |
Comment |
Frequency, % |
| Romano-Ward (autosomal dominant) | |||||
|
LQT1 |
KCNQ1 |
KvLQT1 (Kv7.1) |
11p15.5 |
Trigger: Stress |
30-35 |
|
LQT2 |
KCNH2 |
hERG (Kv11.1) |
7q35-q36 |
Trigger: Noise |
25-30 |
|
LQT3 |
SCN5A |
Nav1.5 |
3p24-p21 |
Trigger: Sleep, rest. Beta blocker therapy seems to be the less effective. |
5-10 |
|
LQT4 |
ANK2 |
Ankyrin-B |
4q25-q27 |
LQT4 has been associated to the production of a defective accessory protein called Ankyrin-B. |
less than 1 |
|
LQT5 |
KCNE1 |
MinK |
21q22.1 |
Associated to the Jervell, Lange-Nielsen syndrome (congenital deafness). |
less than 1 |
|
LQT6 |
KCNE2 |
MiRP1 |
21q22.1 |
Triggers: certain drugs, exercise |
less than 1 |
|
LQT7 |
KCNJ2 |
Kir2.1 |
17q23 |
Associated to the Andersen-Tawil syndrome |
less than 1 |
|
LQT8 |
CACNA1C |
Cav1.2 |
12p13.3 |
Associated to the Timothy syndrome |
less than 1 |
|
LQT9 |
CAV3 |
Caveolin-3 |
3p25 |
Mutations of CAV3 also associated to muscle diseases |
less than 1 |
|
LQT10 |
SCN4B |
Navb4 |
11q23.3 |
So far, only found in one single family |
less than 1 |
| LQT11 | AKAP9 | AKAP9/yotiao | 7q21-q22 | less than 1 | |
| LQT12 | SNTA1 | a1-syntrophin | 20q11.2 | less than 1 | |
| Jervell, Lange-Nielsen (autosomal recessive) | |||||
| JLN1 |
KCNQ1 |
KvLQT1 |
11p15.5 |
more than 90.5 | |
| JLN2 |
KCNE1 |
MinK | 21q22.1 | less than 0.5 | |
Last Update: August 2008 / Prof. Dr. Hugues Abriel, University of Lausanne
Source: Clinical and Genetic Characteristics of Long QT Syndrome: Rev Esp Cardiol. 2007;60(7):739-52
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