| Abstract No.: | A-A1021 |
| Country: | Canada |
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| Title: | ROLE OF FOXN4 IN SPINAL CORD INTERNEURON SPECIFICATION IN THE ZEBRAFISH |
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| Authors/Affiliations: | 1 Li Lin*; 2 Pierre Drapeau;
1 McGill, Montreal, QC, Canada; 2 Université de Montréal, QC, Canada
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| Content: | Objectives: Our study seeks to understand the development of the descending glutamatergic neurons of the vertebrate spinal cord, which is responsible for generating rhythmic motor activities. Most of these interneurons (INs) are thought to be part of the V2 interneuron class in the ventral spinal cord, which is subdivided into V2a and V2b. Generated from the same progenitor pool (p2), the V2 sub-types are actually of opposing neurotransmitter phenotypes, with the V2a being excitatory glutamatergic neurons that activate spinal circuits, and the V2b being inhibitory GABAergic neurons which block activity. Recent studies in mouse identified a transcription factor, foxn4, to be necessary in specifying V2b fate. However, there are contradicting results as to if foxn4 is sufficient in this role to induce V2b INs and suppress V2a fate. Here, we utilized the much simpler system of embryonic zebrafish to study the role of foxn4 in this respect.
Material and Methods: Using RT-PCR, we first investigated the developmentally regulated alternative transcripts of foxn4 in the zebrafish as previous study has implied there was an adult and embryonic form. A translation blocking antisense morpholino oligonucleotide (AMO) was used to knock-down (KD) the expression of foxn4 and the resulting change in V2a and V2b cell numbers was quantified. Over-expression analysis was also possible by injecting in vitro synthesized foxn4 mRNA into 1-4 cell staged embryos. V2a INs were counted in several somites in a transgenic alx-GFP line or by in situ hybridization with a probe to alx. V2b were labeled by immuno staining with an antibody to GABAergic neurons, after a double in-situ/immuno to confirm that a majority of gata3 INs are positive for GAD65/67.
Results: So far, our results indicate that while foxn4 is capable of inducing V2b INs, its KD has little effect on both the V2a & V2b populations.
Conclusion: Our preliminary data support the fact that Foxn4 apparently promotes the V2b over the V2a fate. Knock-down of foxn4 seems to have little effect on the IN populations, although it might be due to the low dose of AMO we used in the experiment. To have a complete idea of the role of foxn4 in the specification of V2 sub-types, we may also need to explore the role of other transcription factors such as mash1 in the future.
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