Mir125b-1 is a microRNA gene. MicroRNAs are crucial regulators in various biological processes, often involved in post-transcriptional regulation of gene expression by binding to target mRNAs [4].

In the human brain, Mir125b-1 is not imprinted. In mice, it is highly expressed in the brain but down-regulated during brain development. It shows preferential expression in the olfactory bulb, thalamus, and hypothalamus, and is enriched in GABAergic neurons, especially somatostatin-expressing GABAergic neurons [1]. Also, its methylation level is significantly correlated with the progression of metastatic clear cell renal cell carcinoma, including late stages, large tumor size, metastasis to lymph nodes and/or distant organs, and loss of differentiation in the tumor [2]. In breast cancer, increased methylation of Mir125b-1 is observed in tumors compared to normal tissues, and it is associated with lymph node metastasis, which can be used to develop a marker system for predicting breast cancer metastasis [3,8]. In non-small cell lung cancer, a significantly high level of its methylation is found in adenocarcinoma and squamous cell lung cancer compared to adjacent normal lung tissue [5]. In ovarian carcinoma, it is hypermethylated at the early stages [7]. And in kidney cancer, its increased methylation levels are associated with the development of distant metastases [6].

In summary, Mir125b-1 is involved in the development and progression of multiple cancers, including renal, breast, lung, and ovarian cancers, through methylation-related mechanisms. In the brain, it shows specific spatiotemporal expression patterns during development. Studies on Mir125b-1, especially those related to its methylation and expression in disease models, help in understanding the pathogenesis of these diseases and may provide potential biomarkers for diagnosis and prognosis.