of the protein or cause alterations in transcriptional and translational regulation. CHRNA4/CHRNB2 Other well studied nAChR genes include the CHRNA4 and CHRNB2, which have been associated as Autosomal Dominant Nocturnal Frontal Lobe Epilepsy (ADNFLE) genes. Both of these nAChR subunits are present in the brain and the occurrence of mutations in these two subunits cause a generalized type of epilepsy. Examples include the CHRNA4 insertion mutation 776ins3 that is associated with nocturnal seizures and psychiatric disorders, and the CHRNB2 mutation I312M that seems to cause not only epilepsy but also very specific cognitive deficits, such as deficits in learning and memory. There is naturally occurring genetic variation between these two genes and analysis of single nucleotide polymorphisms (SNPs) and other gene modifications show a higher variation in the CHRNA4 gene than in the CHRNB2 gene, implying that nAChR β2, the protein encoded by CHRNB2, associates with more subunits than α4. CHRNA2 has also been reported as a third candidate for nocturnal frontal lobe seizures. CHRNA7 Several studies have reported an association between CHRNA7 and endophenotypes of psychiatric disorders and nicotine dependence, contributing to the significant clinical relevance of α7 and research being done on it. CHRNA7 was one of the first genes that had been considered to be involved with schizophrenia. Studies identified several CHRNA7 promoter polymorphisms that reduce the genes transcriptional activity to be associated with schizophrenia, which is consistent with the finding of reduced levels of a7 nAChRs in the brain of schizophrenic patients. Both nAChRs subtypes, α4β2 and α7, have been found to be significantly reduced in post-mortem studies of individuals with schizophrenia. Additionally, smoking rates are significantly higher in those with schizophrenia, implying that smoking nicotine may be a form of self-medicating. Notable variations Nicotinic receptors are pentamers of these subunits; i.e., each receptor contains five subunits. Thus, there is immense potential of variation of these subunits, some of which are more commonly found than others. The most broadly expressed subtypes include (α1)2β1δε (adult muscle-type), (α3)2(β4)3 (ganglion-type), (α4)2(β2)3 (CNS-type) and (α7)5 (another CNS-type). A comparison follows: See also Muscarinic agonist Muscarinic antagonist TDBzcholine References External links Calculated spatial position of Nicotinic acetylcholine receptor in the lipid bilayer Ion channels Autoantigens Cell signaling Acetylcholine receptors