Chrm2, which codes for the cholinergic muscarinic 2 receptor, is a key part of the cholinergic neurotransmitter system. It plays important roles in cognitive functions such as processing cueing/prior information to enhance attentional processes, and is involved in higher-level cognitive flexibility mechanisms [1]. Also, it is associated with the regulation of acetylcholine levels as cortical Chrm2 acts as an autoreceptor [6].

Research has shown that Chrm2 polymorphisms are implicated in various diseases. In Mexican pediatric population, certain Chrm2 polymorphisms are associated with asthma susceptibility [2]. Variation in Chrm2 also predisposes to alcohol dependence, drug dependence, and affective disorders, with a specific haplotype block within the 5'-UTR potentially being more important for the development of these disorders [3]. Additionally, a specific genotype of Chrm2 may have a protective effect for the development of tardive dyskinesia in schizophrenia patients, though the association may be secondary to other factors [4]. In terms of personality traits, Chrm2 variation may contribute to the genetic component of agreeableness and conscientiousness [5].

In conclusion, Chrm2 is crucial for cognitive functions and is associated with multiple disease conditions including asthma, substance dependencies, affective disorders, and tardive dyskinesia. Studies on Chrm2, especially those exploring its polymorphisms, help in understanding the genetic basis of these diseases, potentially paving the way for new diagnostic and therapeutic approaches.

References:

1. Zink, Nicolas, Bensmann, Wiebke, Arning, Larissa, Stock, Ann-Kathrin, Beste, Christian. 2019. CHRM2 Genotype Affects Inhibitory Control Mechanisms During Cognitive Flexibility. In Molecular neurobiology, 56, 6134-6141. doi:10.1007/s12035-019-1521-6. https://pubmed.ncbi.nlm.nih.gov/30729426/

2. Jiménez-Morales, Silvia, Jiménez-Ruíz, Juan Luis, Del Río-Navarro, Blanca Estela, Dean, Michael, Orozco, Lorena. 2014. CHRM2 but not CHRM1 or CHRM3 polymorphisms are associated with asthma susceptibility in Mexican patients. In Molecular biology reports, 41, 2109-17. doi:10.1007/s11033-014-3060-6. https://pubmed.ncbi.nlm.nih.gov/24430298/

3. Luo, Xingguang, Kranzler, Henry R, Zuo, Lingjun, Blumberg, Hilary P, Gelernter, Joel. 2005. CHRM2 gene predisposes to alcohol dependence, drug dependence and affective disorders: results from an extended case-control structured association study. In Human molecular genetics, 14, 2421-34. doi:. https://pubmed.ncbi.nlm.nih.gov/16000316/

4. Boiko, Anastasiia S, Ivanova, Svetlana A, Pozhidaev, Ivan V, Wilffert, Bob, Loonen, Anton J M. 2019. Pharmacogenetics of tardive dyskinesia in schizophrenia: The role of CHRM1 and CHRM2 muscarinic receptors. In The world journal of biological psychiatry : the official journal of the World Federation of Societies of Biological Psychiatry, 21, 72-77. doi:10.1080/15622975.2018.1548780. https://pubmed.ncbi.nlm.nih.gov/30623717/

5. Luo, Xingguang, Kranzler, Henry R, Zuo, Lingjun, Wang, Shuang, Gelernter, Joel. 2007. CHRM2 variation predisposes to personality traits of agreeableness and conscientiousness. In Human molecular genetics, 16, 1557-68. doi:. https://pubmed.ncbi.nlm.nih.gov/17468496/

6. Fujita, Masayo, Ochiai, Yukiko, Hagino, Yoko, Dean, Brian, Ikeda, Kazutaka. 2022. Involvement of muscarinic receptors in psychomotor hyperactivity in dopamine-deficient mice. In Molecular brain, 15, 96. doi:10.1186/s13041-022-00984-x. https://pubmed.ncbi.nlm.nih.gov/36447257/