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Molecular characteristics

A range of different types of ‘faults’ in the SCN2A gene can cause SCN2A-related disorders. These include:

  • Missense variants which are a change in one DNA base pair that results in the substitution of one amino acid for another in the protein made by a gene.
  • Nonsense variants in which there is an altered DNA sequence which prematurely signals the cell to stop building a protein. This type of mutation results in a shortened protein that may function improperly or not at all.
  • Frameshift variants which are the addition or loss of DNA bases which changes a gene’s ‘reading frame’. A reading frame consists of groups of 3 chemical ‘bases’ that each code for one amino acid. A frameshift mutation shifts the grouping of these bases and changes the code for amino acids resulting in a typically non-functional protein.

The specific genetic variant in an affected individual will be documented in the genetic test report.

The SCN2A gene codes for the Nav1.2 channel, which is an important sodium channel in the brain that regulates the excitability of brain cells. Pathogenic variants in the SCN2A gene alter the function of the Nav1.2 channel. The channel may be overactive or underactive. This can cause brain cells to fire more or less frequently than they should, which can result in epileptic seizures and/or differences in how a child learns and develops.

An extensive discussion of the spectrum of genetic changes and the impact on the function of the Nav1.2 channel in SCN2A-related disorders can be found in the Professionals – Molecular characteristics section.

It is recommended that an appointment with a clinical genetics service will be made to discuss the genetic test result and provide genetic counselling to the family.