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Motor neurons project from the central nervous system to innervate muscle cells to either directly or indirectly control their activity. Contact between a motor neuron and muscle cell is usually via a specialized synapse called a neuromuscular junction.
The authors show that in a mouse model of spinal muscular atrophy (SMA), there is a reduction in sensory synaptic drive that leads to motor neuron dysfunction and motor behavior impairments. SMA motor neurons showed a lower surface expression of Kv2.1 potassium channels and reduced spiking ability. Increasing neuronal activity pharmacologically led to the normalization of Kv2.1 surface expression and an improvement in motor function.
The sympathetic system maintains a physiological balance, adjusts bodily functions during daily living activities, and can activate stress responses. The authors identify a variety of unique sympathetic neuronal types and show that the system is highly organized with dedicated neurons organized into discrete outflow channels for specific bodily functions.
The subtype of motor neurons that is most likely to degenerate early in amyotrophic lateral sclerosis is prone to endoplasmic reticulum (ER) stress in mice, owing to low levels of SIL1, an ER-associated protein.