Key Takeaways & Executive Findings
- •• miR-9 exhibits a developmental stage-specific expression pattern in the mouse cerebral cortex, with high levels during early neurogenesis and gradual decline thereafter. • miR-9 promotes neuronal and oligodendrocyte differentiation while suppressing astrocyte differentiation in neural stem cells derived from the ventricular and subventricular zones. • Gain- and loss-of-function experiments demonstrate that miR-9 is a critical regulator of trilineage differentiation balance in neural stem cells. • These findings provide new insights into the molecular mechanisms underlying cortical development and potential therapeutic targets for neurodegenerative diseases.
Abstract
BACKGROUND: Neural stem cells located in the ventricular zone and subventricular zone are crucial for cortical neurodevelopment and the treatment of neurodegenerative diseases. However, their precise regulatory mechanisms remain incompletely understood. miRNA-9 is one of the most abundantly expressed miRNAs in the vertebrate embryonic and adult brain, playing diverse roles during development. Nevertheless, the role of miR-9 in neural stem cell differentiation remains unclear. OBJECTIVE: To investigate the role of miR-9 in regulating the differentiation of neural stem cells in the ventricular zone and subventricular zone. METHODS: Neural stem cells were isolated from the ventricular zone and subventricular zone of embryonic day 14.5 ICR mice and cultured in proliferation medium for 3-4 days to form neurospheres. Stemness was identified by Pax6/Nestin immunofluorescence double staining. The expression profile of miR-9 was detected by qRT-PCR in telencephalon tissues at embryonic days 12.5, 14.5, 16.5, 18.5 and postnatal days 0, 7, as well as in embryonic day 14.5 neural stem cells cultured in vitro. Neural stem cells were transfected with miR-9 inhibitor or mimic using transfection reagents. After 24 hours, cells were differentiated for 3-4 days (neurons) and 6-8 days (glial cells). The differentiation of each lineage was quantified by immunofluorescence staining for Tuj1 (neuronal marker), myelin basic protein (oligodendrocyte marker), and glial fibrillary acidic protein (astrocyte marker). RESULTS AND CONCLUSION: qRT-PCR results showed that miR-9 was highly expressed in early embryonic telencephalon (E12.5-E14.5) and gradually decreased with development (E16.5 to P7). In E14.5 neural stem cells, miR-9 expression level was close to 90% of the internal reference RNU6B. Functional experiments showed that compared with the control group, the miR-9 inhibition group had decreased proportions of Tuj1-positive neurons and myelin basic protein-positive oligodendrocytes, while the proportion of glial fibrillary acidic protein-positive astrocytes increased. Conversely, the miR-9 overexpression group had increased proportions of Tuj1-positive neurons and myelin basic protein-positive oligodendrocytes, and decreased proportion of glial fibrillary acidic protein-positive astrocytes, with significant differences (P < 0.001). These results indicate that miR-9 plays a bidirectional regulatory role in neural stem cell differentiation: (1) It participates in the temporal regulation of neurogenesis through developmental stage-specific expression patterns (high early, downregulated later); (2) It maintains the balance of trilineage differentiation by promoting neuronal and oligodendrocyte differentiation while inhibiting astrocyte generation.
1. Introduction
The differentiation process of neural stem cells in the cerebral cortex is a core event in the development of the mammalian central nervous system, and its precise regulation is crucial for the formation of the six-layered cortical tissue [1]. Neural stem cells are a group of cells with self-renewal capacity and multilineage differentiation potential [2], exhibiting significant spatiotemporal heterogeneity during brain development [3]. The ventricular zone and subventricular zone, as two key germinal regions of neural stem cells, regulate the dynamic balance between neurogenesis and gliogenesis through symmetric and asymmetric division [4-5]. Dysregulation of this balance can lead to brain dysfunction and various neurological diseases, such as brain tumors [6-7], schizophrenia [8], major depression [9], Parkinson's disease [10-11], and Alzheimer's disease [12-13], indicating that neural stem cell differentiation is tightly regulated.
Recent single-cell sequencing studies have shown that the expression profiles of non-coding RNAs in neural stem cells exhibit obvious spatiotemporal specificity [14]. This spatial heterogeneity suggests that microenvironmental signals may regulate the fate determination of neural stem cells through epigenetic mechanisms. MicroRNAs (miRNAs), as key post-transcriptional regulators, have not been systematically characterized for their spatiotemporal expression patterns. miR-9 is one of the most abundantly expressed miRNAs in the vertebrate embryonic and adult brain, playing diverse roles during development [15]. Among the many miRNAs regulating neural stem cell differentiation, miR-9 has attracted much attention due to its evolutionary conservation and high expression in brain tissue [16]. Previous studies have shown that miR-9 participates in early neurogenesis regulation by targeting transcription factors such as TLX (Nr2e1) and FOXG1 [17-18]. However, the specific mechanism of miR-9 in the differentiation choice of neural stem cells in the ventricular and subventricular zones remains controversial.
In this study, we isolated neural stem cells from the embryonic mouse ventricular and subventricular zones, constructed a region-specific miR-9 expression profile using qRT-PCR, and simulated in vivo conditions to investigate the role of miR-9 in neural stem cell differentiation.
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LIU Yingzhao, MA Yanxia, LIN Yaofa, ZHANG Guoqiao, MIAO Weiliang, JIA Yanli, CHI Chenshen, SONG Wangsheng, LI Di, LIU Chenglong, ZHANG Haonan (2026). miR-9 regulates the differentiation of neural stem cells in mouse cerebral cortex. Chinese Journal of Tissue Engineering Research. https://doi.org/10.12307/2026.21344
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Frequently Asked Questions
What is the role of miR-9 in neural stem cell differentiation?
miR-9 promotes neuronal and oligodendrocyte differentiation while inhibiting astrocyte differentiation, thus maintaining the balance of trilineage differentiation in neural stem cells.
How does miR-9 expression change during brain development?
miR-9 is highly expressed in early embryonic telencephalon (E12.5-E14.5) and gradually decreases with development (E16.5 to P7).
What methods were used to study miR-9 function?
Neural stem cells were isolated from E14.5 mouse brains, cultured as neurospheres, and transfected with miR-9 inhibitor or mimic. Differentiation was assessed by immunofluorescence staining for neuronal, oligodendrocyte, and astrocyte markers.
What are the potential implications of this study?
The findings provide insights into the molecular mechanisms of cortical development and may inform therapeutic strategies for neurodegenerative diseases by targeting miR-9.
What is the significance of the ventricular and subventricular zones?
These zones are key germinal regions containing neural stem cells that generate neurons and glial cells during development and in adulthood, playing a role in brain repair and neurodegenerative disease research.
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