Patterning the cone mosaic array in zebrafish retina requires specification of ultraviolet-sensitive cones.
Cone photoreceptors in teleost fish are organized in precise, crystalline arrays in the epithelial plane of the retina. In zebrafish, four distinct morphological/spectral cone types occupy specific, invariant positions within a regular lattice. The cone lattice is aligned orthogonal and parallel to circumference of the retinal hemisphere: it emerges as cones generated in a germinal zone at the retinal periphery are incorporated as single-cell columns into the cone lattice. Genetic disruption of the transcription factor Tbx2b eliminates most of the cone subtype maximally sensitive to ultraviolet (UV) wavelengths and also perturbs the long-range organization of the cone lattice. In the tbx2b mutant, the other three cone types (red, green, and blue cones) are specified in the correct proportion, differentiate normally, and acquire normal, planar polarized adhesive interactions mediated by Crumbs 2a and Crumbs 2b. Quantitative image analysis of cell adjacency revealed that the cones in the tbx2b mutant primarily have two nearest neighbors and align in single-cell-wide column fragments that are separated by rod photoreceptors. Some UV cones differentiate at the dorsal retinal margin in the tbx2b mutant, although they are severely dysmorphic and are eventually eliminated. Incorporating loss of UV cones during formation of cone columns at the margin into our previously published mathematical model of zebrafish cone mosaic formation (which uses bidirectional interactions between planar cell polarity proteins and anisotropic mechanical stresses in the plane of the retinal epithelium to generate regular columns of cones parallel to the margin) reproduces many features of the pattern disruptions seen in the tbx2b mutant.
Department of Molecular, Cellular, and Developmental Biology, College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, Michigan, United States of America.
Pamela A
PA
Raymond
Department of Molecular, Cellular, and Developmental Biology, College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, Michigan, United States of America.
Steven M
SM
Colvin
Department of Physics, College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, Michigan, United States of America.
Zahera
Z
Jabeen
Department of Molecular, Cellular, and Developmental Biology, College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, Michigan, United States of America.
Mikiko
M
Nagashima
Department of Molecular, Cellular, and Developmental Biology, College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, Michigan, United States of America.
Linda K
LK
Barthel
Department of Physics, College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, Michigan, United States of America.
Jeremy
J
Hadidjojo
Department of Molecular, Cellular, and Developmental Biology, College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, Michigan, United States of America.
Lilia
L
Popova
Department of Molecular, Cellular, and Developmental Biology, College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, Michigan, United States of America.
Vivek R
VR
Pejaver
Department of Physics, College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, Michigan, United States of America.
David K
DK
Lubensky
D000818:Animals; D002448:Cell Adhesion; D002450:Cell Communication / Q000528:radiation effects; D002454:Cell Differentiation; D016764:Cell Polarity / Q000528:radiation effects; D004625:Embryo, Nonmammalian; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D009024:Morphogenesis / Q000235:genetics*; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure*; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure*; D015398:Signal Transduction; D020825:T-Box Domain Proteins / Q000172:deficiency / Q000235:genetics*; D014466:Ultraviolet Rays; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029961:Zebrafish Proteins / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism
C513141:Crb2a protein, zebrafish; D008565:Membrane Proteins; D020825:T-Box Domain Proteins; D029961:Zebrafish Proteins; C513142:crb2b protein, zebrafish; C120107:tbx2b protein, zebrafish