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Hypothalamic projections to the optic tectum in larval zebrafish

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  • Lucy A. Heap, University of Queensland
  • ,
  • Gilles C. Vanwalleghem
  • Andrew W. Thompson, University of Queensland
  • ,
  • Itia Favre-Bulle, University of Queensland
  • ,
  • Halina Rubinsztein-Dunlop, University of Queensland
  • ,
  • Ethan K. Scott, University of Queensland

The optic tectum of larval zebrafish is an important model for understanding visual processing in vertebrates. The tectum has been traditionally viewed as dominantly visual, with a majority of studies focusing on the processes by which tectal circuits receive and process retinally-derived visual information. Recently, a handful of studies have shown a much more complex role for the optic tectum in larval zebrafish, and anatomical and functional data from these studies suggest that this role extends beyond the visual system, and beyond the processing of exclusively retinal inputs. Consistent with this evolving view of the tectum, we have used a Gal4 enhancer trap line to identify direct projections from rostral hypothalamus (RH) to the tectal neuropil of larval zebrafish. These projections ramify within the deepest laminae of the tectal neuropil, the stratum album centrale (SAC)/stratum griseum periventriculare (SPV), and also innervate strata distinct from those innervated by retinal projections. Using optogenetic stimulation of the hypothalamic projection neurons paired with calcium imaging in the tectum, we find rebound firing in tectal neurons consistent with hypothalamic inhibitory input. Our results suggest that tectal processing in larval zebrafish is modulated by hypothalamic inhibitory inputs to the deep tectal neuropil.

Original languageEnglish
Article number135
JournalFrontiers in Neuroanatomy
Publication statusPublished - 17 Jan 2018
Externally publishedYes

Bibliographical note

Funding Information:
We thank Rebecca Dunning for creating the PME-linker-MCS plasmid. We are grateful to Karl Deisseroth for providing the Channelrhodopsin-2(ET/TC) plasmid and Misha Ahrens for providing the HuC:H2B-GCaMP6s transgenic line. We thank Owen Randlett, Alexander Schier, and Florian Engert for providing the Z-Brain atlas prior to publication, as well as for assisting in Z-Brain analysis. We thank Jan Kaslin and members of the Scott laboratory for comments on the manuscript. Support was provided by the Australian Research Council Postgraduate Awards to LAH and AWT; an National Health and Medical Research Council (NHMRC) Project Grant (APP1066887), ARC Future Fellowship (FT110100887), a Simons Foundation Explorer Award (336331) and two ARC Discovery Project Grants (DP140102036 and DP110103612) to EKS; an ARC Discovery Project (DP140100753) to HR-D; a UQ Postgraduate Scholarship to IF-B; and an European Molecular Biology Organization (EMBO) Long-term Fellowship (ALTF 727-2014) to GCV. Imaging was performed at the Queensland Brain Institute’s Advanced Microscopy Facility, generously supported by the Australian Government through the ARC LIEF grant LE130100078.

Publisher Copyright:
© 2018 Heap, Vanwalleghem, Thompson, Favre-Bulle, Rubinsztein-Dunlop and Scott.

    Research areas

  • Hypothalamus, Optogenetics, SPIM (selective plane illumination microscopy), Superior colliculus, Tectum, Zebrafish

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