Characterization of green fluorescent protein–expressing retinal cone bipolar cells in a 5-hydroxytryptamine receptor 2a transgenic mouse line

Abstract

Retinal bipolar cells relay visual information from photoreceptors to third-order retinal neurons. Bipolar cells, comprising multiple types, play an essential role in segregating visual information into multiple parallel pathways in the retina. The identification of molecular markers that can label specific retinal bipolar cells could facilitate the investigation of bipolar cell functions in the retina. Transgenic mice with specific cell type(s) labeled with green fluorescent protein (GFP) have become a powerful tool for morphological and functional studies of neurons in the CNS, including the retina. In this study, we report a 5-hydroxytryptamine receptor 2a (5-HTR2a) transgenic mouse line in which expression of GFP was observed in two populations of bipolar cells in the retina. Based on the terminal stratification and immunostaining, all the strongly GFP-labeled bipolar cells were found to be type 4 cone bipolar cells. A small population of weakly labeled bipolar cells was also observed, which may represent type 8 or 9 cone bipolar cells. GFP expression in retinal cone bipolar cells was seen as early as postnatal day 5. In addition, despite severe retinal degeneration due to an rd1 (or Pde6brd1) gene in this transgenic line, the density of GFP-labeled cone bipolar cells remained stable up to at least 6 months of the age. This transgenic mouse line will be a useful tool for the study of type 4 cone bipolar cells in the retina under both normal and disease conditions.

DSCAM-mediated control of dendritic and axonal arbor outgrowth enforces tiling and inhibits synaptic plasticity

“…We used Htr2a transgenic mice (31,32) and immunohistochemistry (IHC) against cell-type-specific markers (33) to study structural development and neuronal plasticity of OFF-type BCs during development [postnatal days (P) 15 and 21] and following developmental maturity (P35, 3 mo, and 6 mo). We quantified dendritic and axonal arbor morphology of more than 1,500 type 3b and type 4 BCs (BC3s, BC4s) through manual tracing in confocal fluorescence image stacks of retinal whole-mounts obtained at five time points ( Fig.…”

“…All animal procedures were performed in accordance with protocols approved by the Animal Use and Care Committees at the University of Idaho and the University of Louisville, and were in compliance with National Institutes of Health guidelines. We used two different transgenic mouse lines manipulating Dscam: (i) Dscam tm1Pfu and (ii) Dscam tm1.1Pfu ; one Cre-dependent reporter mouse: Gt(ROSA)26Sortm9(CAG-tdTomato)Hze (referred to as Ai9; The Jackson Laboratory, stock no: 007909) (96); three Cre recombinaseexpressing transgenic mouse lines: (i) Tg(Htr2a-cre)KM207Gsat (referred to as HTR:Cre; MMRRC stock no: 036750) (31), (ii) Pou4f2:Cre (courtesy of Vann Bennett, Duke University, Durham, NC); (iii) Gt(ROSA)26Sortm1(Cre/ERT2)Tyi (referred to as CreER; The Jackson Laboratory, stock no: J008463) (52); and one GFP transgenic mouse: Htr2a-EGFP (referred to as HTR:GFP; MMRRC, stock no: DQ118) (32). Mice were maintained on a mixed genetic background containing C57BL/6, C3H, 129, and FVB.…”

Heterogeneous transgene expression in the retinas of the TH-RFP, TH-Cre, TH-BAC-Cre and DAT-Cre mouse lines

“…The cellular expression patterns in retinas of many transgenic lines, including both Cre and BAC-Cre lines (Rowan and Cepko, 2004, Haverkamp et al, 2009, Lu et al, 2009, Siegert et al, 2009, Ivanova et al, 2010) includes: 1) the ectopic expression of the transgene in cell types that do not endogenously express the gene, 2) the incomplete expression of the transgene in its endogenous cell types, or 3) a combination of both (Gong et al, 2007, Haverkamp et al, 2009, Ivanova et al, 2010). These patterns of Cre-induced tdTomato fluorescence are also seen in our screen of the dopamine transmitter-related Cre lines: the TH-BAC- and TH-tdTomato retinas had incomplete labeling of type 1 DA amacrine cells as well as numerous other ectopically labeled amacrine cells, and the DAT-tdTomato retina had bistratified and monostratified amacrine cell types, but no labeling of the type 1 DA amacrine cells.…”

Developmental localization of adhesion and scaffolding proteins at the cone synapse

“…Mice used in this study were from either of a C57Bl/6J inbred background, including HTR2a-GFP mice, which were generously provided by Dr. Lane Brown, or from an inbred C3H/HeJ background in which the defective allele of Pde6b ( rd1 ) was replaced with a wild type allele (Costa et al, 2010). HTR2a-GFP mice express GFP in type 4 OFF bipolar cells (Lu et al, 2009). Macaque retinas were obtained from the University of California Primate Center and were fixed in 4% PFA for one hour on ice.…”