Huntington's disease "in vitro"

Novosibirsk biologists have created a cellular model of Huntington's disease

NSU Press Service

Biologists of Novosibirsk State University and the Institute of Cytology and Genetics SB RAS have created a cell line that simulates Huntington's disease. To do this, scientists have introduced the necessary mutations into cells using modern CRISPR\Cas9 genome editing technology. The cellular model is necessary to study the molecular mechanisms of the development of hereditary neurodegenerative disease, which is considered incurable today.

The first symptoms of Huntington's disease (nervous tics, uncontrolled movements and other motor and mental disorders) are manifested in patients aged 35-45 years. Gradually, the disease of the nervous system progresses and within 15-20 years leads to the disintegration of the personality and then death. Treatment is only symptomatic, which temporarily improves the patient's condition, without leading to recovery.

The disease is associated with a mutation in the huntingtin gene. In a normal gene, there is a region consisting of several repeats of the CAG triplet. In all healthy people, such repetitions can be from 9 to 35, but in patients the number of repetitions increases: more than 36.

– The CAG triplet encodes the amino acid glutamine, that is, a polyglutamine tract is present in the synthesized protein. Interestingly, this protein is synthesized in many cells of the body, but mostly striatum neurons die (the structure of the brain responsible for muscle tone, some behavioral reactions, etc.), – says Dinara Sharipova, a 4th-year student of the Faculty of Natural Sciences of NSU, a participant in the study. – Until now, science does not know how the rest of the body's cells cope with the toxic effects of mutant huntingtin and why striatum neurons begin to die only at the age of 35-45 years, and not earlier. It is also not entirely clear what exactly is the toxic effect of huntingtin on cells.

To find the answer to these questions, scientists need a cellular model of the disease. To create a Huntington's disease cell line, the researchers introduced a mutation into normal cells by lengthening the CAG repeat pathway using modern CRISPR/Cas9 genome editing technology. After a line of fibroblasts (connective tissue cells) with a mutation was obtained, they were reprogrammed to a pluripotent state, that is, they were made into induced pluripotent stem cells (iPSCs).

– Roughly speaking, we have returned the cells to their past. The technology of obtaining IPSC allows us to return stem cells, – said Dinara Sharipova. – After all, stem cells have the potential to differentiate into all types of cells. Gradually, with the development of the embryo, the potential of cells decreases, they go through several stages in their development and eventually become differentiated cells (neurons, skin cells, intestines, etc.). 

The obtained "mutant" cell lines are stored in the laboratory of cellular models of human diseases of the ICIG SB RAS, and further work is being carried out with them.

– Now we already have IPSC lines with mutation, their differentiation into neurons and other cells of nervous tissue is underway. At the same time, in parallel, we get lines that carry a smaller number of CAG repeats than in the already obtained line (that is, we want to get several model lines that differ in the size of the mutation, on which the severity of the disease depends). Also, for my thesis, I get a mutant line on neuroblastoma cells (a malignant tumor of the nervous system). This cell line is convenient for modeling neural processes, since it can be differentiated into different types of neurons directly, bypassing the IPSC stage.

According to the researcher, she chose this topic because she always wanted to do biomedicine.

– There are a lot of diseases in the modern world that remain incurable and poorly researched. Huntington's disease also belongs to them. In order to develop an effective method of treatment, it is necessary first to thoroughly study all the molecular processes occurring during neurodegeneration, which, ultimately, is what our work is aimed at. In addition, in addition to Huntington's disease, there are about 10 little-studied diseases with the same cause (elongation of the polyglutamine tract in any protein). Having investigated the processes leading to the development of Huntington's disease, we may reveal some details of the development of these diseases," Dinara Sharipova said.

Portal "Eternal youth" http://vechnayamolodost.ru  25.01.2017