Retina development in zebrafish requires the heparan sulfate proteoglycan agrin.
Recent studies from our laboratory have begun to elucidate the role of agrin in zebrafish development. One agrin morphant phenotype that results from agrin knockdown is microphthalmia (reduced eye size). To begin to understand the mechanisms underlying the role of agrin in eye development, we have analyzed retina development in agrin morphants. Retinal differentiation is impaired in agrin morphants, with retinal lamination being disrupted following agrin morpholino treatment. Pax 6.1 and Mbx1 gene expression, markers of eye development, are markedly reduced in agrin morphants. Formation of the optic fiber layer of the zebrafish retina is also impaired, exhibited as both reduced size of the optic fiber layer, and disruption of retinal ganglion cell axon growth to the optic tectum. The retinotectal topographic projection to the optic tectum is perturbed in agrin morphants in association with a marked loss of heparan sulfate expression in the retinotectal pathway, with this phenotype resembling retinotectal phenotypes observed in mutant zebrafish lacking enzymes for heparan sulfate synthesis. Treatment of agrin morphants with a fibroblast growth factor (Fgf) receptor inhibitor, rescue of the retinal lamination phenotype by transplantation of Fgf8-coated beads, and disruption of both the expression of Fgf-dependent genes and activation of ERK in agrin morphants provides evidence that agrin modulation of Fgf function contributes to retina development. Collectively, these agrin morphant phenotypes provide support for a crucial role of agrin in retina development and formation of an ordered retinotectal topographic map in the optic tectum of zebrafish.
Liu
I-Hsuan
IH
Julius L. Chambers Biomedical/Biotechnology Research Institute, Durham, North Carolina 27707, USA.
Zhang
Chengjin
C
Kim
Min Jung
MJ
Cole
Gregory J
GJ
D000165:Acridine Orange; D018171:Agrin / Q000502:physiology*; D000818:Animals; D030801:Animals, Genetically Modified; D016923:Cell Death; D051959:ELAV Proteins / Q000235:genetics; D000067778:ELAV-Like Protein 3; D004625:Embryo, Nonmammalian / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051518:Fibroblast Growth Factor 3 / Q000235:genetics / Q000378:metabolism; D019922:GAP-43 Protein / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D019812:Heparan Sulfate Proteoglycans / Q000502:physiology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D012160:Retina / Q000187:drug effects / Q000196:embryology* / Q000254:growth & development* / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives; D013477:Superior Colliculi / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D050821:Transcription Factor Brn-3C / Q000235:genetics; D015027:Zebrafish / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D029961:Zebrafish Proteins / Q000235:genetics
D018171:Agrin; D051959:ELAV Proteins; D000067778:ELAV-Like Protein 3; D004791:Enzyme Inhibitors; D051518:Fibroblast Growth Factor 3; D019922:GAP-43 Protein; D019812:Heparan Sulfate Proteoglycans; C527864:N-(5-(5,7-dimethyl Bodipy)-1-pentanoyl)-erythrosphingosine; D016376:Oligonucleotides, Antisense; D011758:Pyrroles; C105686:SU 5402; D050821:Transcription Factor Brn-3C; D029961:Zebrafish Proteins; C088635:elavl3 protein, zebrafish; D049452:Green Fluorescent Proteins; D000165:Acridine Orange; D013110:Sphingosine