Ct55, a Cancer/Testis Antigen (CTA) gene, has its physiological expression restricted to the testis but is activated in many human cancers. It functions as an autophagic manipulator, interacting with LAMP2 and GABARAP (key autophagy regulators) to regulate spermatogenesis. Also, it is involved in pathways related to cancer cell proliferation, mitochondrial DNA maintenance, and NF-κB signaling [1,2,3]. Genetic models, like gene knockout mouse models, are valuable for studying Ct55's functions.

In gene knockout mouse models, depletion of Ct55 led to male infertility in mice, mimicking human sperm individualization defects, excessive cytoplasm residue, and acrosome development issues [1]. In cancer-related studies, CT55 silencing decreased cancer cell proliferation, reduced mtDNA copy number, and attenuated colitis-associated colorectal cancer by inhibiting NF-κB signaling [2,3].

In conclusion, Ct55 plays essential roles in spermatogenesis and cancer-related biological processes. The gene knockout mouse models have revealed its significance in male infertility and in promoting certain cancers, thus providing insights into potential therapeutic targets for infertility and cancers such as colitis-associated colorectal cancer.

References:

1. Zhang, Guohui, Jiang, Chuan, Yang, Yushang, Yang, Yihong, Shen, Ying. 2022. Deficiency of cancer/testis antigen gene CT55 causes male infertility in humans and mice. In Cell death and differentiation, 30, 500-514. doi:10.1038/s41418-022-01098-6. https://pubmed.ncbi.nlm.nih.gov/36481789/

2. Aurrière, Jade, Goudenege, David, Baechler, Simone A, Lenaers, Guy, Khiati, Salim. 2022. Cancer/Testis Antigen 55 is required for cancer cell proliferation and mitochondrial DNA maintenance. In Mitochondrion, 64, 19-26. doi:10.1016/j.mito.2022.02.005. https://pubmed.ncbi.nlm.nih.gov/35189384/

3. Zhao, Huan, Pan, Wen-Ming, Zhang, Hui-Hui, Du, Run-Lei, Zhang, Xiao-Dong. 2019. Cancer testis antigen 55 deficiency attenuates colitis-associated colorectal cancer by inhibiting NF-κB signaling. In Cell death & disease, 10, 304. doi:10.1038/s41419-019-1537-x. https://pubmed.ncbi.nlm.nih.gov/30944312/