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The photoreceptor outer segment (OS), a well-defined sensory cilium, provides an important context for the study of intraflagellar transport (IFT). The early phases of OS development involve successive events that are common to virtually all cilia. Additionally, intense protein trafficking occurs through the cilium and relies on IFT to maintain pro...
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... the transport of components essential for its com- plex architecture and function in phototransduction. The cilium extends from its basal body to form a transition zone, common to all cilia, and its membrane forms an expanded distal domain that accumulates the photopigment, opsin, and other transduction components as a prelude to disc formation ( Fig. 1). Although there is a great deal of focus on the transition zone (Besharse and Horst, 1990;Rohlich, 1975), generally referred to as the connecting cilium, the photoreceptor ciliary axoneme extends distally into the OS ( Kaplan et al., 1987;Sale et al., 1988) where it terminates as singlet microtubules (Insinna et al., 2008b;Steinberg ...
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... is also substantial evidence suggesting that additional singlet microtubules are present in the distal OS (Eckmiller, 1996;Eckmiller, 2000;Roof et al., 1991). During OS formation the ciliary plasmalemma of photoreceptors becomes organized into disc membranes that align perpendicular to the axoneme, which extends distally along one side of the OS (Fig. 1). The discs of rod and cone photoreceptors differ in that those of rods are contained in the cytoplasmic compart- ment and are separated from the OS plasmalemma, while most discs of cones maintain continuity with the plasma membrane (Young, 1976). This fundamental design difference suggests distinct mechanisms of OS disc formation ...
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... current model for photoreceptor IFT (Fig. 1) involves IFT protein complexes like those in other types of cilia, but is divergent in that it includes two kinesin 2 family motors, heterotrimeric kinesin II and homodimeric KIF17, for transport of proteins from the site of synthesis in the inner segment (IS) to the OS. As in other ciliary IFT models cytoplasmic dynein 2 is thought to ...
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Anterograde intraflagellar transport (IFT) employing kinesin-2 molecular motors has been implicated in trafficking of photoreceptor outer segment proteins. We generated embryonic retina-specific (prefix emb) and tamoxifen-induced (prefix tam) deletions of KIF3a and IFT88 in adult mice to study photoreceptor ciliogenesis and protein trafficking. In...
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... The homodimeric Kif17 is the mammalian homolog of the molecular motor OSM-3, a dendritic motor for odorant receptors in Caenorhabditis elegans and holds many different biological functions ranging from the in-vesicles dendritic transport of N-methyl-D-aspartate receptor subunit 2B (NR2B), kainate receptor subunit GluR5, and voltage-gated K+ channel Kv4.2, to intraflagellar transport (IFT)/ciliogenesis and spermatogenesis [3]. Eventually, in vertebrate photoreceptors, Kif17 is necessary for outer segment (OS) development and disc morphogenesis, and this role has been recognized in mutant zebrafish and mice models [4,5]. However, little is known about the involvement of KIF17 in human ophthalmological phenotypes. ...
... Kif17 belongs to the kinesin-2 family of motor proteins, which is part of the kinesin superfamily of proteins (KIFs) and holds a variety of biological functions, including the regulation of the early development of the photoreceptor cilium [3][4][5]13]. As a motor protein, Kif17 shows an N-terminus head motor (N-kinesin) and a tail domain, and two putative stalk domains that form an alpha-helical coiled-coil ( Figure 1B). ...
... Functional (cellular) studies using patient-derived fibroblasts to assess the impact of the identified missense variants on transcript and protein were not possible, due to the absence of KIF17 expression in skin. However, different animal model studies, including from mice and zebrafish, have highlighted an essential role of KIF17 in eye development, particularly for the OS development and disc morphogenesis [3][4][5]. ...
Microphthalmia, anophthalmia, and coloboma (MAC) are a group of congenital eye anomalies that can affect one or both eyes. Patients can present one or a combination of these ocular abnormalities in the so called "MAC spectrum". The KIF17 gene encodes the kinesin-like protein Kif17, a microtubule-based, ATP-dependent, motor protein that is pivotal for outer segment development and disc morphogenesis in different animal models, including mice and zebrafish. In this report, we describe a Sicilian family with two siblings affected with congenital coloboma, microphthalmia, and a mild delay of motor developmental milestones. Genomic DNA from the siblings and their unaffected parents was sequenced with a clinical exome that revealed compound heterozygous variants in the KIF17 gene (NM_020816.4: c.1255C > T (p.Arg419Trp); c.2554C > T (p.Arg852Cys)) segregating with the MAC spectrum phenotype of the two affected siblings. Variants were inherited from the healthy mother and father, are present at a very low-frequency in genomic population databases, and are predicted to be deleterious in silico. Our report indicates the potential co-segregation of these biallelic KIF17 variants with microphthalmia and coloboma, highlighting a potential conserved role of this gene in eye development across different species.
... KIF17 appears largely dispensable for ciliogenesis in zebrafish as Kif17 homozygous mutant animals are viable and display subtle morphological defects of olfactory cilia only ( Zhao et al., 2012). However, KIF17 appeared to play a role during early photoreceptor development of zebrafish retina (Insinna et al., 2009;Malicki and Besharse, 2012). Recent experiments performed by Dr. Besharse's group showed that zebrafish and mouse Osm-3/Kif17 mutants display delayed onset of OS disc morphogenesis without adversely affecting the development of mature and functional photoreceptors ( Lewis et al., 2017). ...
Photoreceptors are polarized neurons, with very specific subcellular compartmentalization and unique requirements for protein expression and trafficking. Each photoreceptor contains an outer segment, the site of photon capture that initiates vision, an inner segment that houses the biosynthetic machinery and a synaptic terminal for signal transmission to downstream neurons. Outer segments and inner segments are connected by a connecting cilium (CC), the equivalent of a transition zone (TZ) of primary cilia. The connecting cilium is part of the basal body/axoneme backbone that stabilizes the outer segment. This report will update the reader on late developments in photoreceptor ciliogenesis and transition zone formation, specifically in mouse photoreceptors, focusing on early events in photoreceptor ciliogenesis. The connecting cilium, an elongated and narrow structure through which all outer segment proteins and membrane components must traffic, functions as a gate that controls access to the outer segment. Here we will review genes and their protein products essential for basal body maturation and for CC/TZ genesis, sorted by phenotype. Emphasis is given to naturally occurring mouse mutants and gene knockouts that interfere with CC/TZ formation and ciliogenesis.
... The mammalian homolog of OSM-3 (KIF17) is important for development of the photoreceptor outer segments, a highly modified form of primary cilia that also possess singlet microtubules similar to C. elegans cilia [47][48][49] [50]. Here we identified specific mutations that impact OSM-3 activity and localization, many of which were dependent on loss of nphp-4. ...
Nephronophthisis (NPHP) is a ciliopathy in which genetic modifiers may underlie the variable penetrance of clinical features. To identify modifiers, a screen was conducted on C. elegans nphp-4(tm925) mutants. Mutations in ten loci exacerbating nphp-4(tm925) ciliary defects were obtained. Four loci have been identified, three of which are established ciliopathy genes mks-1, mks-2, and mks-5. The fourth allele (yhw66) is a missense mutation (S316F) in OSM-3, a kinesin required for cilia distal segment assembly. While osm-3(yhw66) mutants alone have no overt cilia phenotype, nphp-4(tm925);osm-3(yhw66) double mutants lack distal segments and are dye-filling (Dyf) and osmotic avoidance (Osm) defective, similar to osm-3(mn357) null mutants. In osm-3(yhw66) mutants anterograde intraflagellar transport (IFT) velocity is reduced. Furthermore, expression of OSM-3(S316F)::GFP reduced IFT velocities in nphp-4(tm925) mutants, but not in wild type animals. In silico analysis indicates the S316F mutation may affect a phosphorylation site. Putative phospho-null OSM-3(S316F) and phospho-mimetic OSM-3(S316D) proteins accumulate at the cilia base and tip respectively. FRAP analysis indicates that the cilia entry rate of OSM-3(S316F) is slower than OSM-3 and that in the presence of OSM-3(S316F), OSM-3 and OSM-3(S316D) rates decrease. In the presence OSM-3::GFP or OSM-3(S316D)::GFP, OSM-3(S316F)::tdTomato redistributes along the cilium and accumulates in the cilia tip. OSM-3(S316F) and OSM-3(S316D) are functional as they restore cilia distal segment formation in osm-3(mn357) null mutants; however, only OSM-3(S316F) rescues the osm-3(mn357) null Dyf phenotype. Despite rescue of cilia length in osm-3(mn357) null mutants, neither OSM-3(S316F) nor OSM-3(S316D) restores ciliary defects in nphp-4(tm925);osm-3(yhw66) double mutants. Thus, these OSM-3 mutations cause NPHP-4 dependent and independent phenotypes. These data indicate that in addition to regulating cilia protein entry or exit, NPHP-4 influences localization and function of a distal ciliary kinesin. Moreover, data suggest human OSM-3 homolog (Kif17) could act as a modifying locus affecting disease penetrance or expressivity in NPHP patients.
... De manière identique, la Kinésine-II est restreinte au cil connecteur alors que l'orthologue de OSM-3, KIF17 transite le long des deux segments et est nécessaire pour la formation du segment externe des photorécepteurs uniquement (Insinna et al., 2008;Insinna et al., 2009). ...
Cilia are highly conserved structures found from protozoa to mammals where they play essential physiological and developmental functions and cilia dysfunction leads to various syndromes in humans known as ciliopathies. To understand cilia formation and function, I performed functional analysis of two new target genes of the RFX ciliogenic transcription factors. First, I focused on CCDC151 that is evolutionary conserved in motile ciliated species. I showed that CCDC151 is involved in the control of IFT-dependent dynein arm assembly in animals and required for geotaxis behavior of adult flies. In zebrafish, depletion of Ccdc151 leads to left-right asymmetry defects and kidney cysts, two phenotypes resulting from impaired ciliary beating. However, I also showed that CCDC151 is also implicated in other cellular functions in vertebrates as it is involved in proper orientation of cell divisions and implicated in the regulation of primary cilium length in mammalian cells. In a second part, I studied LRRC48 that is also conserved in species with motile cilia. I showed that this protein is essential for motility of flagellar spermatozoids and for motility of the 9+0 sensory cilia as well as in the auditory response in drosophila. In zebrafish, morpholinos induced depletion of this protein leads to hydrocephaly, kidney cysts, inner ear abnormalities and cilia motility defects. Moreover this protein is also required for inner ear biogenesis in the model. In conclusion, these two genes are essential for ciliogenesis and they are new candidate genes potentially implicated in human ciliary diseases
... The severity of disruption is positively correlated with the degree of deficiency in KIF17, which is most prominent in central retina, where the outer segments almost completely fail to form (75) . To tease apart the respective roles played by the two members of the kinesin-2 family, dominant negative forms of KIF3B or KIF17 driven by a late-onset, cone-specifi c transducin promoter was generated in zebrafi sh cone photoreceptors (72,77) . Dominant negative KIF3B disrupted the functions of both inner segments and synaptic terminals. ...
Kinesins are ATP-dependent molecular motors that carry cargos along microtubules, generally in an anterograde direction. They are classified into 14 distinct families with varying structural and functional characteristics. KIF17 is a member of the kinesin-2 family that is plus end-directed. It is a homodimer with a pair of head motor domains that bind microtubules, a coiled-coil stalk, and a tail domain that binds cargos. In neurons, KIF17 transports N-methyl-D-aspartate receptor NR2B subunit, kainate receptor GluR5, and potassium Kv4.2 channels from cell bodies exclusively to dendrites. These cargos are necessary for synaptic transmission, learning, memory, and other functions. KIF17's interaction with NXF2 enables the transport of mRNA bidirectionally in dendrites. KIF17 or its homolog OSM-3 also mediates intraflagellar transport of cargos to the distal tips of flagella or cilia, thereby aiding in ciliogenesis. In many invertebrate and vertebrate sensory cells, KIF17 delivers cargos that contribute to chemosensory perception and signal transduction. In vertebrate photoreceptors, KIF17 is necessary for outer segment development and disc morphogenesis. In the testis, KIF17 (KIF17b) mediates microtubule-independent delivery of ACT from the nucleus to the cytoplasm and microtubule-dependent transport of Spatial-ε, both are presumably involved in spermatogenesis. KIF17 is also implicated in epithelial polarity and morphogenesis, placental transport and development, and the development of specific brain regions. The transcriptional regulation of KIF17 has recently been found to be mediated by nuclear respiratory factor 1 (NRF-1), which also regulates NR2B as well as energy metabolism in neurons. Dysfunctions of KIF17 are linked to a number of pathologies.
... Similar defects are observed by a direct knockdown of a tubulin polyglutamylase (Pathak et al., 2007). Finally, through a series of studies in zebrafish, several microtubular motors have been implicated in transport of IFT complexes during photoreceptor outer segment development (Krock et al., 2007;Krock and Perkins, 2008;Insinna et al., 2009;Insinna et al., 2010). ...
Free swimming zebrafish larvae depend mainly on their sense of vision to evade predation and to catch prey. Hence, there is strong selective pressure on the fast maturation of visual function and indeed the visual system already supports a number of visually driven behaviors in the newly hatched larvae.The ability to exploit the genetic and embryonic accessibility of the zebrafish in combination with a behavioral assessment of visual system function has made the zebrafish a popular model to study vision and its diseases.Here, we review the anatomy, physiology, and development of the zebrafish eye as the basis to relate the contributions of the zebrafish to our understanding of human ocular diseases.
... Although most OS proteins incorporate into disc membranes and are eventually shed from the distal tips of photoreceptors, IFT particles are believed to migrate along the length of the axoneme in both an anterograde and a retrograde manner. Evidence for this comes from transient transgenesis experiments where constructs containing IFT proteins fused to GFP were expressed using a zebrafish rhodopsin promoter (Insinna et al., 2009b;Kennedy et al., 2001;Luby-Phelps et al., 2008). Rod-specific overexpression of IFT20-GFP, IFT52-GFP, IFT57-GFP, and IFT88-GFP found localization of IFT proteins along the entire length of the axoneme, as well as the basal body and the connecting cilium. ...
... Overexpression of the dominant-negative Kif17 (DNKIF17) caused severe ablation of cone OSs, whereas the dominant-negative Kif3b (DNKIF3B) was less damaging to cones. In contrast, opsin mislocalization was observed in cells expressing DNKIF3B but not DNKIF17, suggesting that these two kinesins regulate trafficking of distinct cargoes (Insinna et al., 2009b)). ...
In recent years, studies of zebrafish rod and cone photoreceptors have yielded novel insights into the differentiation of distinct photoreceptor cell types and the mechanisms guiding photoreceptor regeneration following cell death, and they have provided models of human retinal degeneration. These studies were facilitated by the use of transgenic zebrafish expressing fluorescent reporter genes under the control of various cell-specific promoters. Improvements in transgenesis techniques (e.g., Tol2 transposition), the availability of numerous fluorescent reporter genes with different localization properties, and the ability to generate transgenes via recombineering (e.g., Gateway technology) have enabled researchers to quickly develop transgenic lines that improve our understanding of the causes of human blindness and ways to mitigate its effects.
In aquaculture, herbal extracts have been widely tested in multiple fish species due to their safety, low toxicity, and minimal environmental impacts. However, little information is known about the regulatory roles in fish early life stages. Here in the present study, taking dojo loach as an example, we applied glycyrrhizic acid (GA), the most abundant component in licorice root, both in egg hatching and larviculture. GA pre-treatment once at 12.5 mg/L but not 50 mg/L during egg hatching significantly promoted hatchability, thus same dosage were supplemented during Artemia feeding in larviculture. As a positive control, egg yolk was also supplemented during larviculture, resulting in the increased larval body length after 5 days and 10 days. However, GA supplementation even significantly inhibited the body length of loach larvae after 10 days. Further studies indicated the expression pattern of genes involved in growth (GH & IGF-1), early development (PP1, VEGFAa, VIP, & IFT22), nutrient transport (SGLT1, FABP2, & PEPT1), immune (C3–1, Myd88, & IL-1β) and antioxidative responses (SOD, CAT, & GPx) supported the phenotype regarding egg hatchability and larval body length. Thus, our study suggested that the effects of GA and other herbal extracts on fish might vary depending on the dosage and treating period, thus such application should be careful especially during early fish life stages, which may even inhibit fish larval growth performance at inappropriate dosage or period.
In Caenorhabditis elegans, homodimeric [kinesin family (KIF) 17, osmotic avoidance abnormal-3 (OSM-3)] and heterotrimeric (KIF3) kinesin-2 motors are required to establish sensory cilia by intraflagellar transport (IFT) where KIF3 and KIF17 cooperate to build the axoneme core and KIF17 builds the distal segments. However, the function of KIF17 in vertebrates is unresolved. We expressed full-length and motorless KIF17 constructs in mouse rod photoreceptors using adeno-associated virus in Xenopus laevis rod photoreceptors using a transgene and in ciliated IMCD3 cells. We found that tagged KIF17 localized along the rod outer segment axoneme when expressed in mouse and X. laevis photoreceptors, whereas KIF3A was restricted to the proximal axoneme. Motorless KIF3A and KIF17 mutants caused photoreceptor degeneration, likely through dominant negative effects on IFT. KIF17 mutant lacking the motor domain translocated to nuclei after exposure of a C-terminal nuclear localization signal. Germ-line deletion of Kif17 in mouse did not affect photoreceptor function. A rod-specific Kif3/Kif17 double knockout mouse demonstrated that KIF17 and KIF3 do not act synergistically and did not prevent rhodopsin trafficking to rod outer segments. In summary, the nematode model of KIF3/KIF17 cooperation apparently does not apply to mouse photoreceptors in which the photosensory cilium is built exclusively by KIF3.-Jiang, L., Tam, B. M., Ying, G., Wu, S., Hauswirth, W. W., Frederick, J. M., Moritz, O. L., Baehr, W. Kinesin family 17 (osmotic avoidance abnormal-3) is dispensable for photoreceptor morphology and function.
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