In the December 2013 issue of PLOS1, researchers sought to understand how a mutation in a particular ion channel may lead to febrile seizures.
Fevers in small children can lead to seizures, and, while most children do not suffer any long-term damage from such seizures, a small fraction of children can develop epilepsy later in life. Hence, the question of why some children are more susceptible to febrile seizures is an area of active research.
An ion channel called the Hyperpolarization-activated cyclic nucleotide-gated (HCN) allows for ions to pass in and out of neurons and is responsible for rhythmic activity in ensembles of neurons. Hence, these are also sometimes called as the ”pacemaker channels.:
There is some evidence that HCN channels may contribute to febrile seizures. To understand how this could be the case; researchers took cells from children with febrile seizures, cultured them, and studied how they responded to increased temperature. These were the results:
- Gene analysis revealed a novel mutation (called S126L) in the HCN gene in children who had presented with febrile seizures.
- The electrical activity of cells that had the mutated ion channel (as opposed to the intact one) was studied at 25ºC and at 38ºC to see if there was a difference in how these cells react.
- No differences between cells were found at 25ºC.
- However, when the temperature of the media was raised to 38ºC, cells with the mutated ion channel showed a greater sensitivity to higher temperature. The mutation in the HCN channel allowed it to pass more positive ions into the cell, resulting in enhanced depolarization and excitability.
More research needs to be done to understand these and other mutations in the HCN gene; however the S126L is a novel mutation that may lead to hyperexcitability in neurons during increased temperatures.