Spinal Muscular Atrophy (SMA) is a neurodegenerative disease targeting motor neurons. It normally occurs in the spinal cord. Nerve cells send messages from the brain to the muscles and vice versa. They are primarily responsible for bodily movements such as walking, swallowing, and breathing.
Severe strains of SMA cause paralysis and eventually death for the victims. Patients with milder forms normally experience weakness and wasting away of the muscular tissue. SMA involves the loss of nerve cells called motor neurons.
In most cases the proximal and lung muscles are affected first, but then spread to other body systems.
Neurons in SMA patients are unable to produce adequate amounts of a protein called Survival of Motor Neuron (SMN). This causes wasting away and eventually death of the cells.
Scientists have researched and developed different therapies to alleviate and treat the effects of SMA, and most of them have been targeted at fixing the gene itself. Approximately one in 50 people are carriers of the fatal genetic disease, which kills the most number of infants under the age 2.
Recent Harvard Research
In a recent discovery, researchers at the Harvard Stem Cell Institute (HSCI) have identified a compound that helps stabilise and protect the SMN protein. It uses induced pluripotent stem cells to make human models of neurological diseases.
Lee Rubin, a faculty member from the institutes’ Department of Stem Cell and Regenerative Biology sought to determine why motor neurons were targeted, and found out that the motor neurons experienced similar stress as those affected by Amyotrophic Lateral Sclerosis, also known as Lou Gehrig’s disease. His team of researchers also found out that some SMA affected neurons were dying before others, though they all experienced the same environment.
When the team analysed motor neurons derived from ALS patients, they found out that motor neurons with the highest levels of SMN protein were most likely to survive than those with lower levels. The research also showed that the survival of motor neurons depended on the availability of the SMN protein. The results suggest that if the amount of SMN protein is increased in any single motor neuron, the cell could be saved from dying.
In order to affirm these results, researchers led by Nadia Litterman induced human and murine motor neurons with a compound called Cullin, which is thought to regulate protein generation in cells. They found out that when exposed to Cullin, the SMA proteins became more stable and even multiplied abundantly. As a consequence of this, all motor neurons survived in the human specimens in the dish, and the in mouse models.
In summarising the results of the study, Rubin pointed out the discovery could end up benefitting patients who suffered from ALS as well as SMA.
Harvard’s office of technology development have filed an application to patent this approach towards the search for a cure for both diseases.