Profiling the breadth of axonally enriched small non-coding RNAs

Local protein synthesis of a large population of axonal mRNAs is precisely regulated in regenerating axons.

MicroRNAs (miRNAs) are strong candidates for modulating such translational switches. Similar to axonal mRNAs, some miRNAs are differentially distributed in subcellular regions of neurons and their levels are altered following nerve injury. I hypothesize that a subset of miRNAs present in axons is derived from local maturation of precursor miRNAs (pre-miRNAs) that are specifically targeted to their final destinations to actively regulate local mRNA translation. Using a mechanical squeezing method optimized in my lab we isolated axoplasm from sciatic nerves to purify axonal RNAs. Axoplasmic RNA isolates were enriched for small RNAs and small miRNA libraries were generated for RNA deep sequencing. Of 141 axoplasmic miRNAs annotated, we found that 63 miRNAs showed significantly differential levels after nerve injury (Fig below).

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The heatmap with a cluster dendrogram shows distinct patterns of miRNA levels in sciatic nerve in response to injury. Red shows an increased change compared to the uninjured control and green denotes a decreased level.