The CHRNB2 gene encodes a subunit of the neuronal nicotinic acetylcholine receptor (nAChR), a ligand-gated ion channel located in the plasma membrane. This channel is a heteropentameric structure composed of alpha and beta subunits. Upon activation by its ligands nicotine or acetylcholine, the channel allows the passage of sodium, potassium and calcium ions across the plasma membrane, thus mediating signal transduction at synapses. The channel is believed to play a role in several brain functions such as memory, learning, sleep and the perception of pain and sound.
The gene has been implicated in Epilepsy, Nocturnal Frontal Lobe, 3 (ENFL3), a neurological disorder characterized by clusters of motor seizures that occur during sleep.
The CHRNB2 gene is located on the long arm of chromosome 1. It spans a length of 12.2 kb of DNA and its coding sequence is spread across 6 exons. The protein product encoded by this gene has a molecular mass of 57 kDa and consists of 502 amino acids. The gene is overexpressed in the fetal and adult human brain. Heterozygous mutations in the CHRNB2 gene have been associated with ENFL3; so far 3 missense CHRNB2 mutations have been identified in affected individuals.
Monies et al. (2017) discussed the findings of 1000 diagnostic panels and exomes carried out at a next generation sequencing lab in Saudi Arabia. One patient, a 21-month-old female, presented with neuroregression, fine/gross motor delay, speech delay, microcephaly, temporal lobe atrophy, dystonia, hypertonia, hepatic failure and poor vision. Using a multigene panel for neurological disorders, a heterozygous mutation (c.6862C>T, p.R2288X) was identified in exon 4 of the patient’s CHRNB2 gene, associated with Nocturnal Frontal Lobe Epilepsy, 3 (ENFL3). As the CHRNB2 gene had previously been tentatively linked to ENFL3, this report helped confirm its association with the disorder.
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