Gene’s Mutation Crucial For Human Development Related To Arrhythmia

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Arrhythmia is a cardiac condition that can endanger one’s life. It is characterized by an abnormal heart rate or rhythm, such as bradycardia or tachycardia. Millions of people globally experience this condition. Studies have been conducted to discover more the pathology surrounding arrhythmias.

The heart rate and rhythm are regulated by the cardiac conduction system (CCS), which is composed of specialized cells controlling the cardiac rate found in the heart’s wall. These cells send electrical signals from the sinoatrial node (SA) in the right atrium to the ventricles that result to heart contraction and pumping of blood. Furthermore, the biologic and genetic aspects involved in the CCS’ formation and function are not yet very clear; nonetheless, this novel study with mice reveals that modified function of TBx3 gene impedes the development of CCS and leads to fatal arrhythmias.

Among humans, Tbx3 mutations were initially depicted as cause of limb deformities in people having ulnar-mammary syndrome (hereditary birth disorder where there are bone malformations in the hands/forearms and underdevelopment of sweat and mammary glands

According to the University of Utah’s researchers, CCS is highly sensitive to levels of TBx3. This can be found in the Proceedings of the National Academy of Sciences early edition, dated December 26, 2011. Arrhythmias and sudden death occurred in mouse embryos having under-the-critical threshold levels of Tbx3.  Moreover, when Tbx3 levels were augmented, mice tend to survive to birth. However, as adults, they suffered from arrhythmias and immediate death.

Dr. Anne M. Moon, U of U-School of Medicine’s adjunct professor of pediatrics and corresponding author of this study, stated that Tbx3 dysfunction and its link to acquired or spontaneous arrhythmias still necessitate further studies. She further added that the CCS has high sensitivity to Tbx3 and Tbx3 is a requisite for CCS’s development, maturation and proper functioning. Moreover, Tbx3 protein (a transcription factors encoded by Tbx3 gene) was associated with the development of the heart; nonetheless, its role still remains unclear. Moon and her colleagues (Dr. Deborah Frank, assistant professor of pediatrics) discovered that little changes in the Tbx3 gene’s structure may lead to the alteration of the protein’s level in mice. This can lead to the impairment of the electrical signal in the SA node and obstruct the atrioventricular (AV) node that is responsible for the conduction of signals from the atria to the ventricles. The outcome is life-threatening arrhythmias in mice (both embryonic and adult). Moon articulated that these findings have repercussions for the possibility of functional heart tissue regeneration.

In her future studies, Moon aims to determine the mechanism surrounding Tbx3’s regulation of the CCS’s cells, as well as if cells without sufficient Tbx3 die or transform into other forms of cell. This study truly provided a better picture of Tbx3’s role in a very important organ of humans—the heart.




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