What Is SCN2A?
SCN2A is a gene (also known as sodium voltage-gated channel alpha subunit 2) responsible for controlling the excitability of some of the neurons within the brain. This is due to the Nav1.2 sodium channel being affected by mutations of the SCN2A gene.
Conditions linked to SCN2A:
- Epilepsy - either early onset <3 months of age or later onset >3 months of age.
The epilepsies can be categorised as BFNIS (Benign Familial Neonatal-Infantile Seizures) or Developmental and Epileptic Encephalopathies such as Early Infantile Developmental Epileptic Encephalopathy (EIDEE). Epilepsy syndromes Ohtaraha, West and Lennox-Gastaut have also been linked to SCN2A variants.
- Autism Spectrum Disorder (ASD) and other neurological conditions
Symptoms are individual to the person diagnosed and their variant but can include gastrointestinal issues, Sleep disorders, Global development delay and Episodic Ataxia.
SCN2A can be inherited from a parent or be newly diagnosed in a person with no hereditary links which is known as De Novo.
With an increased focus on genetic testing in cases of Epilepsy and Autism, numbers of SCN2A diagnoses in older children and even adults are occurring where previously it would be more commonly found in younger children and infants due to symptoms such as early onset seizures and their response to particular sodium channel blocker medications including as Phenytoin, Sodium Valproate and Carbamazepine.
Gene mutations or variants are split into two categories based on elements seen or experienced.
Gain of function (GOF) variants - The Nav1.2 sodium channel is excessively active sending more signals across the neurons. This typically can result in cases of early onset seizures where seizures are seen in the days or 1st couple of weeks following birth.
Loss of function (LOF) variants - Here the same sodium channel is less active meaning fewer signals are sent via the neurons. Autism Spectrum Disorder and persons with intellectual disabilities without epilepsy are often found with a LOF variant.
However some variants are difficult to categorise but it can be helpful especially in cases of epilepsy as particular Sodium Channel blocker medications can be more helpful in GOF variants than in LOF for example.