Mir125b-1-KO Mouse

Mir125b-1 is a microRNA-encoding gene. MicroRNAs are crucial regulators in various biological processes, often involved in post-transcriptional regulation of gene expression by binding to target mRNAs [1-8].

In human brain, Mir125b-1 is not imprinted, which is different from its isoform Mir125b-2. In mouse brain, it is highly expressed but down-regulated during development, with preferential expression in the olfactory bulb, thalamus, and hypothalamus, and is enriched in GABAergic neurons, especially somatostatin-expressing ones [1].

In metastatic clear cell renal cell carcinoma, high methylation levels of Mir125b-1 are correlated with late stages, large tumor size, metastasis, and loss of differentiation [2]. In breast cancer, increased methylation of Mir125b-1 in tumors compared to normal tissues was observed, and it was part of an optimized marker system for early diagnosis. Detection of its methylation was sufficient to classify samples as breast cancer [3].

In melanogenesis, reduction of miR-125b expression in pigmented cells was due to hypermethylation of the Mir125b-1 promoter [4]. In non-small cell lung cancer, a significantly high level of Mir125b-1 methylation was found in adenocarcinoma and squamous cell lung cancer compared to adjacent normal tissue [5].

In kidney cancer, increased methylation of Mir125b-1 was associated with distant metastases, and a combined panel including this gene could estimate metastasis probability with high accuracy [6]. In ovarian carcinoma, Mir125b-1 was hypermethylated at early stages, and in breast cancer, its hypermethylation was associated with lymph node metastasis and a system for predicting metastasis was developed based on it [7,8].

In conclusion, Mir125b-1 is involved in multiple biological and disease-related processes. Its non-imprinting in the human brain and specific spatiotemporal expression in the mouse brain contribute to understanding brain development. In various cancers such as renal, breast, lung, and ovarian cancers, changes in its methylation status are associated with tumor progression, metastasis, and can be used as potential biomarkers, highlighting the importance of studying Mir125b-1 in disease diagnosis and prognosis.