AII amacrine cells discriminate between heterocellular and homocellular locations when assembling connexin36-containing gap junctions.
Electrical synapses (gap junctions) rapidly transmit signals between neurons and are composed of connexins. In neurons, connexin36 (Cx36) is the most abundant isoform; however, the mechanisms underlying formation of Cx36-containing electrical synapses are unknown. We focus on homocellular and heterocellular gap junctions formed by an AII amacrine cell, a key interneuron found in all mammalian retinas. In mice lacking native Cx36 but expressing a variant tagged with enhanced green fluorescent protein at the C-terminus (KO-Cx36-EGFP), heterocellular gap junctions formed between AII cells and ON cone bipolar cells are fully functional, whereas homocellular gap junctions between two AII cells are not formed. A tracer injected into an AII amacrine cell spreads into ON cone bipolar cells but is excluded from other AII cells. Reconstruction of Cx36-EGFP clusters on an AII cell in the KO-Cx36-EGFP genotype confirmed that the number, but not average size, of the clusters is reduced - as expected for AII cells lacking a subset of electrical synapses. Our studies indicate that some neurons exhibit at least two discriminatory mechanisms for assembling Cx36. We suggest that employing different gap-junction-forming mechanisms could provide the means for a cell to regulate its gap junctions in a target-cell-specific manner, even if these junctions contain the same connexin.
Research Centre for Neurosensory Sciences/Department of Neurobiology, University of Oldenburg, 26111 Oldenburg, Germany.
Arndt
A
Meyer
Gerrit
G
Hilgen
Birthe
B
Dorgau
Esther M
EM
Sammler
Reto
R
Weiler
Hannah
H
Monyer
Karin
K
Dedek
Sheriar G
SG
Hormuzdi
D025042:Amacrine Cells / Q000378:metabolism*; D000818:Animals; D017630:Connexins / Q000235:genetics* / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism*; D055786:Gene Knockout Techniques; D049452:Green Fluorescent Proteins / Q000096:biosynthesis; D018345:Mice, Knockout; D055503:Protein Multimerization; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012160:Retina / Q000166:cytology; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein / Q000378:metabolism; D000097004:Gap Junction delta-2 Protein
D017630:Connexins; D049452:Green Fluorescent Proteins; D011993:Recombinant Fusion Proteins; D062826:Zonula Occludens-1 Protein; D000097004:Gap Junction delta-2 Protein; C569043:Tjp1 protein, mouse; C082920:connexin 45; C485184:enhanced green fluorescent protein
Amacrine cell; Bipolar cell; Electrical synapse; Gap junction; Retina; connexin