“Inflammation and matrix metalloproteinase 9 (Mmp-9) regulate photoreceptor regeneration in adult zebrafish”

For journal club this week, we read a paper from Dr. Nicholas Silva who published this work last year in Glia, titled “Inflammation and matrix metalloproteinase 9 (Mmp-9) regulate photoreceptor regeneration in adult zebrafish”. These findings came out of his PhD work in the Hitchcock lab at the University of Michigan. 
This was a fun zebrafish glia paper with beautiful images and neat techniques (some of us were new to the zymogram!) that investigates how the inflammatory environment affects the ability of Müller glia to proliferate and differentiate into new rods and cones after photoreceptor injury. During this injury response, Müller glia highly express a matrix metalloproteinase, Mmp-9. It turns out that if the glia don’t express mmp9, they increase proliferation and make more photoreceptors. Overproduced rods persist over time, however, cones die. Cone survival can be rescued in mmp9 mutants by suppressing the immune response later in time with dexamethasone, suggesting that Mmp-9’s influence on the inflammatory ‘soup’ affects photoreceptor regeneration. 
Of course there’s more twists and turns to the story, so we encourage you to check out the paper for yourself! We look forward to reading Nick’s future work as a postdoc in the Molofsky Lab and beyond. 
-Evan