Axonal transcriptome of human stem cell derived neurons
The identification of axonal mRNAs in model organisms has led to the discovery of multiple proteins synthesized within axons for functional roles such as axon guidance and injury response. The extent to which protein synthesis within the axon is conserved in humans is unknown. Here we used axon-isolating microfluidic chambers to characterize the axonal transcriptome of human embryonic stem cells (hESC-neurons) differentiated using a protocol for glutamatergic neurons. Using gene expression analysis, we identified mRNAs proportionally enriched in axons, representing a functionally unique local transcriptome as compared to the human neuronal transcriptome inclusive of somata and dendrites. Further, we found that the most abundant mRNAs within hESC-neuron axons were functionally similar to the axonal transcriptome of rat cortical neurons. We confirmed the presence of two well characterized axonal mRNAs in model organisms, {beta}-actin and GAP43, within hESC-neuron axons using multiplexed single molecule RNA-FISH. Additionally, we report the novel finding that oxytocin mRNA localized to these human axons and confirmed its localization using RNA-FISH. This new evaluation of mRNA within human axons provides an important resource for studying local mRNA translation and has the potential to reveal both conserved and unique axonal mechanisms across species and neuronal types.