Cos2/Kif7 and Osm-3/Kif17 regulate onset of outer segment development in zebrafish photoreceptors through distinct mechanisms.
Zebrafish morphants of osm-3/kif17, a kinesin-2 family member and intraflagellar transport motor, have photoreceptor outer segments that are dramatically reduced in number and size. However, two genetic mutant lines, osm-3/kif17sa0119and osm-3/kif17sa18340, reportedly lack any observable morphological outer segment defects. In this work, we use TALENs to generate an independent allele, osm-3/kif17mw405, and show that both osm-3/kif17sa0119and osm-3/kif17mw405have an outer segment developmental delay in both size and density that is fully recovered by 6 days post-fertilization. Additionally, we use CRISPRs to generate cos2/kif7mw406, a mutation in the kinesin-4 family member cos2/kif7 that has been implicated in controlling ciliary architecture and Hedgehog signaling to test whether it may be functioning redundantly with osm-3/kif17. We show that cos2/kif7mw406has an outer segment developmental delay similar to the osm-3/kif17 mutants. Using a three-dimensional mathematical model of outer segments, we show that while cos2/kif7mw406and osm-3/kif17mw405outer segments are smaller throughout the first 6 days of development, the volumetric rates of outer segment morphogenesis are not different among wild-type, cos2/kif7mw406, and osm-3/kif17mw405after 60hpf. Instead, our model suggests that cos2/kif7mw406and osm-3/kif17mw405impact outer segment morphogenesis through upstream events that that are different for each motor. In the case of cos2/kif7mw406mutants, we show that early defects in Hedgehog signaling lead to a general, non-photoreceptor-specific delay of retinal neurogenesis, which in turn causes the secondary phenotype of delayed outer segment morphogenesis. In contrast, the osm-3/kif17mw405outer segment morphogenesis delays are linked specifically to initial disc morphogenesis of photoreceptors rather than an upstream event. Further, we show that osm-3/kif17 mutant mice also exhibit a similarly delayed outer segment development, suggesting a role for osm-3/kif17 in early outer segment development that is conserved across species. In conclusion, we show that both osm-3/kif17 and cos2/kif7 have comparable outer segment developmental delays, although through independent mechanisms.
Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Tylor R
TR
Lewis
Department of Ophthalmology and Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Sean R
SR
Kundinger
Department of Ophthalmology and Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Amira L
AL
Pavlovich
Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Jonathan R
JR
Bostrom
Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Brian A
BA
Link
Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA; Department of Ophthalmology and Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA. Electronic address: jbeshars@mcw.edu.
Joseph C
JC
Besharse
D000818:Animals; D001483:Base Sequence; D064113:CRISPR-Cas Systems / Q000235:genetics; D002923:Cilia / Q000187:drug effects / Q000378:metabolism; D000072669:Gene Editing; D053823:Hedgehog Proteins / Q000378:metabolism; D016547:Kinesins / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D009024:Morphogenesis / Q000187:drug effects; D060172:Morpholinos / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D055495:Neurogenesis / Q000187:drug effects; D055214:Retinal Photoreceptor Cell Outer Segment / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013696:Temperature; D000069896:Transcription Activator-Like Effector Nucleases; D015027:Zebrafish / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000378:metabolism*
D053823:Hedgehog Proteins; C499749:Kif7 protein, zebrafish; D060172:Morpholinos; D029961:Zebrafish Proteins; D000069896:Transcription Activator-Like Effector Nucleases; C528806:Kif17 protein, zebrafish; D016547:Kinesins
Hedgehog signaling; Intraflagellar Transport; Kinesin; Outer Segment