Chrnb4, encoding the β4 subunit of the neuronal nicotinic acetylcholine receptors (nAChRs), is an important gene. nAChRs are allosterically regulated, ligand-gated ion channels, and the gene cluster CHRNA5-CHRNA3-CHRNB4 is associated with tobacco-related phenotypes [1]. Genetic variation in this cluster increases vulnerability to tobacco dependence and smoking-associated diseases [1].

In Chrnb4-Cre; Dicerflox/flox conditional knockout (CKO) mice, deletion of Dicer1 from cone cells leads to cone photoreceptor cell degeneration and death, with cone-specific abnormalities apparent by 3 weeks of age and 50% of cones lost by 4 months, along with impaired cone function [3]. Also, in human esophageal squamous cell carcinoma (ESCC), high expression of CHRNB4 is associated with unfavorable prognosis, and knockdown of CHRNB4 can inhibit ESCC cell proliferation via the Akt/mTOR and ERK1/2/mTOR pathways [2]. In non-small cell lung cancer, unmethylation of CHRNB4 is an unfavorable prognostic factor [4].

In conclusion, Chrnb4 is crucial in the function of nAChRs and is associated with tobacco-related phenotypes. Mouse models, especially CKO models, have revealed its role in cone photoreceptor survival and in cancer-related processes such as tumor progression and cell proliferation in ESCC and non-small cell lung cancer. These findings provide insights into the biological functions of Chrnb4 and its potential as a biomarker and therapeutic target in related diseases.

References:

1. Picciotto, Marina R, Kenny, Paul J. 2021. Mechanisms of Nicotine Addiction. In Cold Spring Harbor perspectives in medicine, 11, . doi:10.1101/cshperspect.a039610. https://pubmed.ncbi.nlm.nih.gov/32341069/

2. Li, Nan, Liu, Kaisheng, Dong, Shaowei, Wang, Xiao, Wang, Shaoxiang. 2020. Identification of CHRNB4 as a Diagnostic/Prognostic Indicator and Therapeutic Target in Human Esophageal Squamous Cell Carcinoma. In Frontiers in oncology, 10, 571167. doi:10.3389/fonc.2020.571167. https://pubmed.ncbi.nlm.nih.gov/33304845/

3. Aldunate, Eduardo Zabala, Di Foggia, Valentina, Di Marco, Fabiana, Ali, Robin R, Sowden, Jane C. 2019. Conditional Dicer1 depletion using Chrnb4-Cre leads to cone cell death and impaired photopic vision. In Scientific reports, 9, 2314. doi:10.1038/s41598-018-38294-9. https://pubmed.ncbi.nlm.nih.gov/30783126/

4. Yoo, Seung Soo, Lee, Su Man, Do, Sook Kyung, Kim, Dong Sun, Park, Jae Yong. 2014. Unmethylation of the CHRNB4 gene is an unfavorable prognostic factor in non-small cell lung cancer. In Lung cancer (Amsterdam, Netherlands), 86, 85-90. doi:10.1016/j.lungcan.2014.08.002. https://pubmed.ncbi.nlm.nih.gov/25172267/