MicroRNA-338 Attenuates Cortical Neuronal Outgrowth by Modulating the Expression of Axon Guidance Genes

Abstract

MicroRNAs (miRs) are small non-coding RNAs that confer robustness to gene networks through post-transcriptional gene regulation. Previously, we identified miR-338 as a modulator of axonal outgrowth in sympathetic neurons. In the current study, we examined the role of miR-338 in the development of cortical neurons and uncovered its downstream mRNA targets. Long-term inhibition of miR-338 during neuronal differentiation resulted in reduced dendritic complexity and altered dendritic spine morphology. Furthermore, monitoring axon outgrowth in cortical cells revealed that miR-338 overexpression decreased, whereas inhibition of miR-338 increased axonal length. To identify gene targets mediating the observed phenotype, we inhibited miR-338 in cortical neurons and performed whole-transcriptome analysis. Pathway analysis revealed that miR-338 modulates a subset of transcripts involved in the axonal guidance machinery by means of direct and indirect gene targeting. Collectively, our results implicate miR-338 as a novel regulator of cortical neuronal maturation by fine-tuning the expression of gene networks governing cortical outgrowth.

MicroRNA-338 modulates cortical neuronal placement and polarity

“…1E findings that miR-338 sponge efficiently reduces endogenous miR-338 levels in cortical neurons. 18 In vivo modulation of miR-338 levels affects neuronal migration in the developing cortex Since previous studies suggested that miR-338 might have the capacity to modulate axonal development in neurons, we aimed at determining the effects of miR-338 expression changes on cortical development. To examine the expression profile of miR-338 during brain development, total RNA was isolated from brain tissue obtained at several developmental time points, namely, embryonic (E) day E10.5, E13.5, E14.5, E15.5, E16.5, E18.5, and at postnatal day (P) 0, followed by qRT-PCR quantification of mature miR-338 levels at these time points.…”

“…miR-338 target analysis in primary cortical neurons raised the possibility that miR-338 could similarly modulate the expression of many genes fitting in pathways critical for programming neuronal development. 18 Previously we have used anti-miR-338 with a relatively short half-life, and provided evidence that this miR attenuates neuronal outgrowth by locally regulating axonal mitochondrial function. 17 Our studies suggested that the repressing effect of miR-338 on axonal outgrowth diminished over time as axonal outgrowth grew near the length of unaltered control neurons within 5-6 d (unpublished observation).…”

“…Pathway analysis revealed that miR-338 modulates a subset of transcripts involved in the axonal guidance machinery by means of direct and indirect gene targeting. 18 Interestingly, the mouse models of 22q11.2 deletion syndrome, which constitutes one of the strongest genetic risks for schizophrenia and exhibits an age-dependent reduction of miR-338 levels, also suffer from mitochondrial dysfunction, which raises the possibility that mitochondrial dysfunction in this mouse model may be one of the many consequences of an aberrant miR-338 levels. 39,40 In Conclusion, the outcome of this investigation suggests a direct role for miR-338 during early cortical development.…”

“…16 Furthermore, miR-338 controls axonal outgrowth in cortical and superior cervical ganglion (SCG) neurons through the regulation of axon guidance and nuclear-encoded mitochondrial genes, respectively. 17,18 miR-338 is encoded within the intron of the AATK gene. Previously, we showed that miR-338 has the capacity to regulate the mRNA levels of its host-gene by binding to the AATK 3 0 untranslated region (3 0 UTR).…”

Effects of miR-338 on morphine tolerance by targeting CXCR4 in a rat model of bone cancer pain

“…Since pain and morphine tolerance have similar signalling pathways, miRNA may also be involved in the development of morphine tolerance, and neurons in the dorsal horn of the spinal cord may also be key in pain conduction and development of morphine tolerance [23]. While miR-338 is a kind of brain-specific miRNA [10] also expressed in spinal cord [24], it is safe to infer that miR-338 is related to development of morphine tolerance. Researches show that miR-338 expression was down-regulated in liver cancer and oral squamous cell carcinoma, and this reduced level of miR-338 was closely related to malignant activities like cancer metastasis that can cause BCP [25–27]; thus we can infer that miR-338 expression may also be down-regulated.…”