VEGA 2/0169/16

Principal Investigator: Michal Cagalinec

Duration: January 2016 – December 2018
Coordinating Organization: Institute of Molecular Physiology and Genetics SAS, Bratislava (2016-2017); Institute of Experimental Endocrinology BRC SAS (2018)

Annotation:

Wolfram syndrome (WS) is a recessive neurological disorder caused by mutation of the Wfs1 gene. The Wfs1 protein is highly expressed in the brain and heart and is embedded in the endoplasmic reticulum (ER) where it modulates Ca2+ levels and ER stress. Additionally, the main symptoms of the WS are consistent with the ones characteristic for mitochondrial diseases. In fact, our preliminary results showed already that silencing of Wfs1 in mouse neurons decreased the mitochondrial fusion frequency and caused mitochondrial fragmentation, demonstrating strong impact of Wfs1 to mitochondrial function in neurons. Although the high expression of Wfs1 in the heart and cardiac symptoms in WS identified recently emphasize the functional importance of Wfs1 in the heart, the most common causes of morbidity in WS are the neurological manifestations.

Keywords:

mitochondria, endoplasmic reticulum, Wolfram syndrome, fusion-fission, calcium, contractility

Objectives:

Therefore in this project we propose to study if the knockout of the Wfs1 gene in mice leads to disturbance in contractile properties of the heart both at organ and cell level. As Wfs1 impacts mitochondrial dynamics and morphology in neurons, we plan to analyse mitochondrial dynamics and ultrastructure in Wfs1 deficient myocytes. To understand the functional link of Wfs1 to mitochondria in neurons and myocytes we aim to answer if this link is mediated by direct ER-mitochondria interaction and/or by calcium. Mitochondria-ER contact sites will be analysed by electron microscopy. The role of calcium will be elucidated by measuring of myocyte cytoplasmic calcium transients using confocal microscopy and the interaction of Wfs1 with the two most abundant calcium channels in ER – the IP3- and ryanodine receptors will be resolved by methods of molecular biology.

Central question: What mechanism protects functionality of ventricular myocytes from failure in case of deletion or mutation of Wfs1 gene?
Finding an answer to this question may open a possibility to improve the brain functioning by turning on these protection mechanisms in neurons or to use them for a therapy of other cardiovascular diseases.
Goal 1. Is mitochondrial dynamics impaired in the Wfs-/- myocytes?
Goal 2. Does the Wfs1 deficiency cause perturbations in mitochondrial ultrastructure of cardiac myocytes? Do these changes differ from the ones in neurons?
Goal 3. Is Wfs1 responsible for tighter interaction between mitochondria and ER?
Goal 4. Are the cytoplasmic calcium levels and the contractile properties of the left ventricular myocytes isolated from the Wfs1-/- animals perturbed?

Publications: