To do this, scientists have made the necessary mutations in cells using modern technology editing the genome CRISPR \ Cas9. A cellular model is appropriate for studying the molecular mechanisms of the development of a hereditary neurodegenerative disease, which is considered incurable today.
The first symptoms of Huntington's disease (tics, involuntary movements and other motor and mental disorders) occur 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 to 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 (huntingtin). In the normal gene, there is a section 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 triplet CAG encodes the amino acid glutamine, which means, that the polyglutamine tract is present in the synthesized protein. It is interesting that this protein is synthesized in many cells of the body, however, mainly striatum neurons (the brain structure is responsible for muscle tone, some behavioral reactions, etc.) die, — says the participant in the study, 4th-year student of the Faculty of Natural Sciences, NSU Dinara Sharipova — 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 before. It is also not entirely clear what exact toxic effect has huntingtin on cells.
To search for answers to these questions, scientists need a cellular model of the disease. To create a cell line of Huntington's disease, researchers have mutated to normal cells, extending the
CAG repeats pathway using modern CRISPR / Cas9 genome editing technology. After the fibroblast line (connective tissue cells) was obtained with the mutation, they were reprogrammed to a pluripotent state and made induced pluripotent stem cells (IPSC).
— Roughly speaking, we returned the cells to their past. The technology of obtaining IPSC allows us to return cells stem, — says 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 the cells decreases, they go through several stages in their development and eventually become differentiated cells (neurons, skin cells, intestines, etc.).
— Now we already have IPSK lines with a mutation; they are differentiated into neurons and other cells of the nervous tissue. At the same time, we get lines, bearing fewer repetitions of the CAG than already obtained a line (I mean, we want to get some model lines, differing in size mutation that affects the severity of the disease). Also for my diploma work, I get a mutant line of neuroblastoma cells (malignant tumor of the nervous system). This cell line is convenient for modeling neural processes, as it can be differentiated into different types of neurons directly, bypassing the stage of IPSC.
According to the researcher, she has chosen this topic, because she always wanted to study biomedicine.
— In today's world, there are many diseases that remain incurable and underexplored. Huntington's disease also belongs to them. To develop an effective method of treatment, it is necessary to study all the molecular processes that occur during neurodegeneration, and our work is dedicated to this.
In addition, apart from Huntington's disease, there are about ten poorly studied diseases having the same cause (lengthening of the polyglutamine tract in some protein). After examining the processes leading to the development of Huntington's disease, we may disclose some details of the elaboration of these diseases, — said Dinara Sharipova.
