Project Research Report

prepared by Dr. Brais (June 2008)

At the end of 2006, the Foundation of Ataxia Charlevoix-Saguenay gave the mandate to Dr. Bernard Brais at the Centre hospitalier de l'Université de Montreal to conduct research on the Ataxia of Charlevoix-Saguenay (ARSACS). Four main objectives were established. The first one was to put in place a team of researchers in order to accelerate research on Sacsin, the mutated protein in ARSACS. Since early 2007, he is working with the team of Prof. Peter McPherson of the Montreal Neurological Institute, international expert in vesicular transport in the neurons. This collaboration now extends to Prof. Kalle Gehring, a specialist in interactions protein-protein and professor of biophysics at the Department of Biochemistry at McGill University.The team continues to explore further collaborations to accelerate work on various fronts.

The Foundation had also mandated Dr. Brais to develop reagents essential to the research on ARSACS. In this context, the team, in collaboration with various private partners, has developed a range of DNA (cDNA) of the SACS gene and a serie of antibodies.

At the time the project started, the function of the Sacsin was still unknown. Based on bio-informatics studies of the sequence and several laboratory experiments, the research team came to some assumptions about the function of this protein. Several results of protein-protein interactions suggest that the Sacsin is a protein essential to the functioning of a specific component of the neurons in the brain. The research work should lead to the submission of an article in 2008, which will confirm that the efforts of the Foundation have led to the launch of an active research on ARSACS.

The research team has also developed partnerships as well as strategies to generate mouse models of ARSACS. These models will enable us to better understand the normal role of the protein and the impact of mutations on its function. These models are essential to the development of therapeutic trials in animals.

The objective of the research group on ARSACS is the same as the Foundation, to better understand the biological basis of the disease in order to find therapeutic developments.

Minutes of the board meeting of June 4, 2007


In spite of the fact that the ataxia recessive spastic of Charlevoix-Saguenay is a recessive disease common in Quebec, research work to discover the function of the sacsine has not advanced since the discovery of the transferred gene. The goal of the research project is to characterize the function of the sacsine and to develop cellular models and animals which will allow a better comprehension of this disease. The objectives of this vast project are: 1) to identify other changes present in the French Canadian population; 2) to generate a complete cDNA for the SACS gene as well as antibodies against the protein sacsine; 3) to find the cellular and sub-cellular localization of the sacsine (normal and transferred); 4) to establish if the inhibition of SACS by RNAi has an impact on the cells ES, on the neuronal differentiation and on the synaptic functions; 5) to identify the proteins which interact with the sacsine; 6) to develop models of transgenic mice (knocked-out and knock-in).

The identification of all mutations of the SACS gene in the French Canadian population will make it possible to offer a better genetic advice. The identification of the function and the partners of the sacsine will make it possible to find therapeutic targets. The production of knocked-out and knock-in model mice will allow to study the function of the protein and to test various therapeutic molecules.matti

Where we are with the research project


Two basic tools are necessary for biomedical research at the cellular level: the availability of antibodies which allow the identification of a specific protein and one cDNA of the gene which can be modified. Since September 2006, a cDNA almost complete was produced, almost complete because since the original order and the reception of the cDNA, the definition of the gene has changed. However, it misses only some amino acids at one extremity. It needs to be modified slightly.

Five antibodies against various parts of the sacsine were produced. Several of them still require greater purification. One of these antibodies enabled us to obtain preliminary results on the possible cellular localization of the sacsine.

The cloning of the various functional fields of the protein will be completed soon. This will enable us to identify which fields of the protein are the most important and to identify the proteins which interact with the sacsine.

Preliminary experiments with RNAi are underway. As a first step, it is a question of seeing whether the stop of expression will be fatal or which cellular modifications are involved. For the cellular models, various neuronal cellular lines will make it possible to make studies of expression.

Animal models are in production: a transgenic knocked-out mouse by the Canadian consortium NorCOMM and a conditional knock-in and a knock-out mouse are in production in partnership with the RRTQ. At the clinical level, we are searching for new mutations present in the Quebec population. Other animal models will be also developed.