SCN8A
SCN8A is a gene that encodes the alpha subunit of the voltage-gated sodium channel, Nav1.6. This channel is primarily found in the neurons of the central nervous system and plays a crucial role in the propagation of action potentials in neurons. Mutations in the SCN8A gene have been associated with a variety of neurological disorders, including epilepsy, intellectual disability, and movement disorders.
Structure[edit | edit source]
The SCN8A gene is located on the short (p) arm of chromosome 12 at position 13. The encoded protein, Nav1.6, is a large, complex molecule composed of four homologous domains (I-IV), each containing six transmembrane segments (S1-S6). The S4 segment in each domain acts as a voltage sensor, while the pore-forming loop between S5 and S6 is responsible for sodium ion selectivity and conductance.
Function[edit | edit source]
Nav1.6 channels are primarily expressed in the axon initial segment and nodes of Ranvier in neurons, where they play a critical role in the initiation and propagation of action potentials. They are also involved in the regulation of neuronal excitability and synaptic transmission.
Clinical significance[edit | edit source]
Mutations in the SCN8A gene can lead to a variety of neurological disorders. These include:
- SCN8A encephalopathy: This severe condition is characterized by early-onset epileptic seizures, intellectual disability, and movement disorders. It is caused by de novo (new) mutations in the SCN8A gene.
- Early infantile epileptic encephalopathy 13 (EIEE13): This is a severe form of epilepsy that begins in infancy. Affected individuals have frequent seizures and severe intellectual disability.
- Intellectual disability, autosomal dominant 16 (MRD16): This condition is characterized by mild to moderate intellectual disability, often accompanied by seizures.
See also[edit | edit source]
References[edit | edit source]
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Contributors: Prab R. Tumpati, MD