Stage de master : Modeling neurodegenerative rare disorders in induced pluripotent stem cells (S. Bendahhou)

This master project is proposed by Team 1 for 2019-2020. Spinal muscular atrophies (SMA) are a heterogeneous group of neurodegenerative disorders characterized by the degeneration of anterior horn cells of the spinal cord, leading to progressive symmetric muscle weakness and atrophy. Using the iPS cells of SMA patients (type I-II-III) and healthy subjects, we propose to investigate the different aspects of SMA in vitro.

Spinal muscular atrophies (SMA) are a heterogeneous group of neurodegenerative disorders characterized by the degeneration of anterior horn cells of the spinal cord, leading to progressive symmetric muscle weakness and atrophy.

SMA is caused by hereditary recessive mutations or deletion in the survival of motor neuron 1 (SMN1) gene. SMA is the second most common autosomal recessive disorder after cystic fibrosis, with a panethnic carrier frequency of 1:54. It is also the most common cause of hereditary childhood death, usually leading to death within the first year of life.

In fact, there are four distinct forms of the disease described: SMA-I, SMA-II, SMA-III , and SMA-IV, clinically defined by an increase in the age of onset and a decrease in the severity of symptoms.

The mechanisms by which the reduction of SMN protein levels, encoded by SMN1 gene ubiquitously expressed, leads to selective degeneration of motor neurons (MNs), are not yet well understood. Until recently, SMA was considered an incurable neurodegenerative disease. A new treatment, an antisense oligonucleotide (Nusinersen), has been approved lately by the Food Drug Administration (FDA).

In recent years, there has been great interest in induced pluripotent stem (iPS) cells as a model for the study of genetic diseases, particularly those characterized by the inaccessibility of patients of disease target cells. The SMA, affecting motor neurons, is one of them. It has been shown, in iPS cells from a patient with SMA type I, that the process of motor neuronal differentiation is not involved, but the neuronal degeneration begins after neuronal development. In addition, different animal and cellular models of the disease have confirmed the presence of motor neuron hyperexcitability due to Na channel hyperactivity.

Using the iPS cells of SMA patients (type I-II-III) and healthy subjects, we propose to investigate the different aspects of SMA in vitro. These iPS cells are adult cells reprogrammed using 4 genes essential to embryonic stem cells (Oct4, Sox2, Klf4 and c-Myc), and are able to differentiate into all cell types. The motor neurons, astrocytes and sensory neurons will be derived from the different iPS cell lines of the three SMA types. We will evaluate the electrical properties, morphology, survival and cell proliferation on the motor neurons from the iPS cells.

This proposal will generate an in vitro model for the three most severe forms of SMA. These cells will represent a valuable tool to shed light on the electrical properties, investigating in particular the Na channels. Using patch clamp, PCR, and immunohistochemical techniques, this project will challenge the role of SMN1 in hyperexcitability and morphology in the motor neuron. Electron microscopy will allow us to conduct morphological studies of neuronal cells to better understand from which cell and at what stage of differentiation neuronal degeneration occurs. This could lead to the determination of the pathophysiological mechanisms underlying the SMA and may open the doors for the identification of novel SMN-independent therapeutic targets.

 

Cellules souches, différentiation

Canaux ioniques et transporteurs membranaires

Pathologie humaine

Signalisation moléculaire

Physiologie