Regeneration Paper Out



    This week our laboratory's research paper was accepted at PLOS ONE. This wraps up my last few years of experiments looking at the effects of tubulin acetylation on axonal regeneration in vitro and in vivo. Although our investigations led mostly to negative data, I hope that it contributes to the body of knowledge in the regeneration field.

    Back in 2013, we followed up on a study by the Valeria Cavalli laboratory in Washington University, St Louis, studying how histone deacetylase (HDAC5), when exported from the nucleus to the axonal cytoplasm, could be important for axonal regeneration after injury. HDAC5 is an enzyme normally found in the nucleus of cells, which, along with other HDACs, deacetylates histone proteins, inhibits gene transcription and is widely thought to inhibit axonal regeneration. The novelty of the finding by the Cavalli lab was that inhibiting HDAC5 in the axonal cytoplasm diminished axonal regeneration. Furthermore, they proposed that this was due to HDAC5 having a function in deacetylation of microtubules in the axonal cytoplasm, which promoted a more dynamic microtubule pool to augment axon growth.

    I wanted to look at whether axonal regeneration could be enhanced when HDAC5 was over-expressed in adult DRG axons and in injured axons of the sciatic nerve in rats. I also wanted to see if expressing alpha tubulin acetyl transferase (aTAT1), which specifically acetylates tubulin, would have the opposite effect on axonal regeneration to HDAC5. Although aTAT1 is known to affect sperm motility and development, few labs have hitherto reported on the effect of aTAT1 in axon growth of adult neurons. Contrary to our expectations, we found an increase in axonal growth after over expressing aTAT1. We suggested in the paper that this increase could have been due to unknown functions of aTAT1 at play outside of its catalytic activity. Furthermore, over expressing HDAC5 in the axonal cytoplasm did not increase axonal growth. None of the genes we tested had a significant effect on improving axonal regeneration in vivo in lesioned sciatic nerves.

    Even though we did not find any significantly ground breaking improvements in axonal regeneration, I hope that the finding of aTAT1 enhancing axon growth in vitro will provide a basis for further study into its role for regeneration. The study of posttranslational modifications in neurons, particularly with respect to how microtubules can be altered, has exploded since I began the investigation. To truly stimulate axonal growth and microtubule dynamicity after injury it will likely require not just an acetylation modification but multiple changes throughout the cytoskeleton.

    This manuscript was my first corresponding author paper in which I delt with the submission, cover letter and editor correspondances. This followed the usual long series of processes involving conceptualization, design and writing of the manuscript with my professor. The process gave me a finer understanding of the submission process for peer review papers, at least with PLOS ONE. The review process was remarkably smooth for me considering the editor's demands were not beyond my capabilities in the lab. I also dealt with a constant back and forth communication in the last week with the journal publisher, correcting the paper at a granular level in order to fit it with the format of the journal. What really struck me was the requirement for raw data disclosure, essentially an agreement that I would upload all my raw data (MS Excel files) with the manuscript to show that I had not made up the results. This is something new to the journal which none of my immediate colleagues had discussed before in previous years. It's a sign of the times - in the era of p-hacking and overwhelming observer-biased publications in the biological sciences I think it is a step in the right direction. Enforcing raw data uploads maintains some honesty and data integrity. It also gives other people - scientist or non-scientist - a chance to point out if I have made a mistake.