Mir21a, a microRNA, is involved in multiple biological processes and associated with various pathways. It has been linked to the NF-κB signaling pathway, among others, and plays a significant role in inflammation, cell proliferation, and tumorigenesis. Gene knockout mouse models have been crucial in understanding its functions [1,2,3].

In a study on colorectal cancer, Fusobacterium nucleatum was found to increase miR21 expression by activating Toll-like receptor 4 signaling to MYD88 and then nuclear factor-κB. Inhibitors of miR21 prevented F. nucleatum-induced cell proliferation and invasion, and miR21a-/-mice had fewer and smaller tumors, along with longer survival times compared to control mice, suggesting miR21a promotes colorectal carcinogenesis [1].

In an anaphylaxis study, miR21a mimic negatively regulated passive cutaneous anaphylaxis and passive systemic anaphylaxis by inhibiting hallmarks of allergic reactions, indicating its role in allergic inflammations [2].

For glioblastoma, disruption of genomic mmu-miR-21a with a single adeno-associated virus vector reduced tumor growth and improved overall survival in glioblastoma-bearing mice, showing its oncogenic role in glioblastoma [3].

In conclusion, Mir21a is a key regulator in processes like inflammation, cell proliferation, and tumor development. Findings from Mir21a knockout mouse models have revealed its significance in diseases such as colorectal cancer, anaphylaxis, and glioblastoma, providing valuable insights into the underlying mechanisms and potential therapeutic targets.

References:

1. Yang, Yongzhi, Weng, Wenhao, Peng, Junjie, Qin, Huanlong, Ma, Yanlei. 2016. Fusobacterium nucleatum Increases Proliferation of Colorectal Cancer Cells and Tumor Development in Mice by Activating Toll-Like Receptor 4 Signaling to Nuclear Factor-κB, and Up-regulating Expression of MicroRNA-21. In Gastroenterology, 152, 851-866.e24. doi:10.1053/j.gastro.2016.11.018. https://pubmed.ncbi.nlm.nih.gov/27876571/

2. Jo, Hyein, Jeoung, Jaewhoon, Shim, Kyeonghee, Jeoung, Dooil. 2024. Nur77 Mediates Anaphylaxis by Regulating miR-21a. In Current issues in molecular biology, 46, 3175-3192. doi:10.3390/cimb46040199. https://pubmed.ncbi.nlm.nih.gov/38666929/

3. Nieland, Lisa, Vrijmoet, Anne B, Jetten, Isabelle W, Breakefield, Xandra O, Abels, Erik R. 2024. CRISPR targeting of mmu-miR-21a through a single adeno-associated virus vector prolongs survival of glioblastoma-bearing mice. In Molecular therapy : the journal of the American Society of Gene Therapy, 33, 133-151. doi:10.1016/j.ymthe.2024.11.023. https://pubmed.ncbi.nlm.nih.gov/39563028/