title: Zebrafish TARP Cacng2 is required for the expression and normal development of AMPA receptors at excitatory synapses.
abstract: Fast excitatory synaptic transmission in the CNS is mediated by the neurotransmitter glutamate, binding to and activating AMPA receptors (AMPARs). AMPARs are known to interact with auxiliary proteins that modulate their behavior. One such family of proteins is the transmembrane AMPA receptor-related proteins, known as TARPs. Little is known about the role of TARPs during development, or about their function in non-mammalian organisms. Here we report the presence of TARPs, specifically the prototypical TARP, stargazin, in developing zebrafish. We find that zebrafish express two forms of stargazin, Cacng2a and Cacng2b from as early as 12-h post fertilization (hpf). Knockdown of Cacng2a and Cacng2b via splice-blocking morpholinos resulted in embryos that exhibited deficits in C-start escape responses, showing reduced C-bend angles, smaller tail velocities and aberrant C-bend turning directions. Injection of the morphants with Cacng2a or 2b mRNA rescued the morphological phenotype and the synaptic deficits. To investigate the effect of reduced Cacng2a and 2b levels on synaptic physiology, we performed whole cell patch clamp recordings of AMPA mEPSCs from zebrafish Mauthner cells. Knockdown of Cacng2a results in reduced AMPA currents and lower mEPSC frequencies, whereas knockdown of Cacng2b displayed no significant change in mEPSC amplitude or frequency. Non-stationary fluctuation analysis confirmed a reduction in the number of active synaptic receptors in the Cacng2a but not in the Cacng2b morphants. Together, these results suggest that Cacng2a is required for normal trafficking and function of synaptic AMPARs, while Cacng2b is largely non-functional with respect to the development of AMPA synaptic transmission.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.
authors.forename: Birbickram
authors.initials: B
authors.lastname: Roy
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.
authors.forename: Kazi T
authors.initials: KT
authors.lastname: Ahmed
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.
authors.forename: Marcus E
authors.initials: ME
authors.lastname: Cunningham
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.
authors.forename: Jannatul
authors.initials: J
authors.lastname: Ferdous
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.
authors.forename: Rajarshi
authors.initials: R
authors.lastname: Mukherjee
authors.affiliation: Department of Physiology, University of Alberta, Edmonton, Alberta, Canada, T6G 2H7.
authors.forename: Wang
authors.initials: W
authors.lastname: Zheng
authors.affiliation: Department of Physiology, University of Alberta, Edmonton, Alberta, Canada, T6G 2H7.
authors.forename: Xing-Zhen
authors.initials: XZ
authors.lastname: Chen
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.|Department of Physiology, University of Alberta, Edmonton, Alberta, Canada, T6G 2H7.|Centre for Neuroscience, University of Alberta, Edmonton, Alberta, Canada, T6G 2E1.
authors.forename: Declan W
authors.initials: DW
authors.lastname: Ali
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D055785:Gene Knockdown Techniques; D055369:Miniature Postsynaptic Potentials / Q000187:drug effects; D060172:Morpholinos; D009043:Motor Activity / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D012333:RNA, Messenger / Q000378:metabolism; D018091:Receptors, AMPA / Q000378:metabolism*; D012249:Rhombencephalon / Q000196:embryology / Q000378:metabolism / Q000473:pathology; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D013569:Synapses / Q000378:metabolism* / Q000473:pathology; D015027:Zebrafish / Q000196:embryology* / Q000502:physiology*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D060172:Morpholinos; D012333:RNA, Messenger; D018091:Receptors, AMPA; D029961:Zebrafish Proteins; C000613214:cacng2a protein, zebrafish
keywords: AMPA; Mauthner; development; stargazin; zebrafish