Arl13b regulates ciliogenesis and the dynamic localization of Shh signaling proteins

Larkins, Christine E.; Aviles, Gladys D. Gonzalez; East, Michael P.; Kahn, Richard; Caspary, Tamara

doi:10.1091/mbc.e10-12-0994

Cited by 252 publications

(310 citation statements)

References 51 publications

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“…However, in contrast to other mouse mutants that disrupt cilia, we found via both biochemical and genetic analyses that Gli3 repressor activity was unaffected in Arl13b hnn mutants (Caspary et al, 2007). Arl13b hnn mutants possess abnormal cilia in which components of Shh signaling are not regulated properly: Ptch1 and Smo localize to cilia regardless of Shh stimulation, and there is no Gli enrichment in cilia upon Shh stimulation (Larkins et al, 2011). This is consistent with the constitutive activation of Shh…”

Section: Introductionsupporting

confidence: 77%

“…At confluence, MEFs were split into a six-well plate containing gelatin-coated cover slips at a density of 800,000 cells/well. MEFs were then serum-starved for 24 hours and tamoxifen (2 M, Sigma H7904) was added in serum-free media, 10% FBS-containing media or Shh-conditioned media (Larkins et al, 2011). Cover slips were collected at 24, 36, 42 and 48 hours, and MEFs were fixed and processed for antibody staining.…”

Section: Cagg-crementioning

confidence: 99%

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Temporal deletion of Arl13b reveals that a mispatterned neural tube corrects cell fate over time

Bay

Mariani

et al. 2012

Development

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SUMMARYCilia are necessary for sonic hedgehog (Shh) signaling, which is required to pattern the neural tube. We know that ventral neural cell fates are defined by a specific cohort of transcription factors that are induced by distinct thresholds of Shh activity mediated by opposing gradients of Gli activator (GliA) and Gli repressor (GliR). Despite this understanding, the role of Shh as an instructive morphogen is viewed as increasingly complex, with current models integrating positive inputs in terms of ligand concentration and time, along with negative feedback via the downstream gene regulatory network. To investigate the relative contributions of the positive and negative inputs from Shh signaling in neural patterning, we took advantage of a protein that uncouples the regulation of GliA and GliR: the cilia protein ADP-ribosylation factor-like 13b (Arl13b). By deleting Arl13b in mouse, we induced low-level constitutive GliA function at specific developmental stages and defined a crucial period prior to E10.5 when shifts in the level of GliA cause cells to change their fate. Strikingly, we found that improperly patterned cells in these mice converted to the wild-type pattern by E12.5. We further showed that the recovery of patterning did not occur when we also deleted Gli3, the primary GliR in the neural tube, revealing a crucial role of Gli3 in the maintenance of neural patterning.

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Section: Introductionsupporting

confidence: 77%

Section: Cagg-crementioning

confidence: 99%

Temporal deletion of Arl13b reveals that a mispatterned neural tube corrects cell fate over time

Bay

Mariani

et al. 2012

Development

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“…Similarly, the Arl13 and Arl3 Arf-family small GTPases (Zhang et al 2013) play roles in ciliary transmembrane protein targeting and localization in C. elegans sensory neurons and in mammalian cells (Schrick et al 2006;Larkins et al 2011;Humbert et al 2012;Li et al 2012;Schwarz et al 2012). No effects were found on STR-44 or STR-163 localization in rab-8 mutants in either AWB or ASK (Table 3).…”

Section: Resultsmentioning

confidence: 99%

Diverse Cell Type-Specific Mechanisms Localize G Protein-Coupled Receptors to Caenorhabditis elegans Sensory Cilia

Brear

Yoon

Wojtyniak³

et al. 2014

Genetics

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The localization of signaling molecules such as G protein-coupled receptors (GPCRs) to primary cilia is essential for correct signal transduction. Detailed studies over the past decade have begun to elucidate the diverse sequences and trafficking mechanisms that sort and transport GPCRs to the ciliary compartment. However, a systematic analysis of the pathways required for ciliary targeting of multiple GPCRs in different cell types in vivo has not been reported. Here we describe the sequences and proteins required to localize GPCRs to the cilia of the AWB and ASK sensory neuron types in Caenorhabditis elegans. We find that GPCRs expressed in AWB or ASK utilize conserved and novel sequences for ciliary localization, and that the requirement for a ciliary targeting sequence in a given GPCR is different in different neuron types. Consistent with the presence of multiple ciliary targeting sequences, we identify diverse proteins required for ciliary localization of individual GPCRs in AWB and ASK. In particular, we show that the TUB-1 Tubby protein is required for ciliary localization of a subset of GPCRs, implying that defects in GPCR localization may be causal to the metabolic phenotypes of tub-1 mutants. Together, our results describe a remarkable complexity of mechanisms that act in a protein-and cellspecific manner to localize GPCRs to cilia, and suggest that this diversity allows for precise regulation of GPCR-mediated signaling as a function of external and internal context. SIGNALING molecules must be precisely localized to specific subcellular domains to optimize detection and transduction of external stimuli. G protein-coupled receptors (GPCRs) comprise a large family of transmembrane signaling proteins that directly bind and transduce a range of cues including photons, odorants, neurotransmitters, and peptides (Pierce et al. 2002;Kato and Touhara 2009;Demaria and Ngai 2010;Sung and Chuang 2010;Chamero et al. 2012;Frooninckx et al. 2012;Montell 2012;Bathgate et al. 2013). Regulation of GPCR function, including regulation of membrane targeting and trafficking to specific subcellular regions, is a major contributor to the tuning of signaling efficacy and fidelity (e.g., Deretic et al. 1995;Ango et al. 2000;Xia et al. 2003;Esseltine et al. 2012;. However, much remains to be understood regarding the mechanisms by which GPCR trafficking and membrane localization are regulated.GPCR-mediated signal transduction in many cellular contexts requires these proteins to be localized to specialized microtubule-based primary cilia. For example, in photoreceptors and olfactory neurons, efficient sensory signal transduction is mediated via localization of rhodopsin and olfactory receptors, together with other signaling molecules, to photoreceptor outer segments and olfactory neuron cilia, respectively (Insinna and Besharse 2008;Berbari et al. 2009;Pifferi et al. 2010;Deretic and Wang 2012). Receptors in the Hedgehog (Hh) morphogen signaling pathway such as the Smoothened and Patched transmembrane proteins, and the G...

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“…About 70% of wild-type MEFs show Arl13b-positive cilia upon culture in serum-free condition for 24 h. MEFs that lack Arl13b rarely grow cilia (B20% ciliated cells after serum starvation) and their cilia are shorter. 12 We transfected Arl13b hnn MEFs with either a wild-type ARL13B construct or the Y86C ARL13B construct, along with a DsRed cotransfection plasmid to allow visualization of the transfected cells. We measured the ability of each construct to rescue normal ARL13B protein expression in the cilia of Arl13b hnn MEFs.…”

Section: Novel Arl13b Variant In Joubert Syndrome S Thomas Et Almentioning

confidence: 99%

“…10 In mouse, loss of Arl13b function results in disrupted cilia and defective SHH signaling due to the involvement of ARL13B in the movement of SHH signaling components in and out of the cilia. 11,12 Similarly, arl-13, the Caenorhabditis elegans orthologue of ARL13B, functions in ciliary membranes, where it is involved in ciliary transmembrane protein localization and transport of proteins to the tip of the cilium. 13,14 More recently, Arl13b signaling in primary cilia has been shown to be crucial for the polarization of radial glial scaffold, an essential step in cerebral cortex formation.…”

mentioning

confidence: 99%

Identification of a novel ARL13B variant in a Joubert syndrome-affected patient with retinal impairment and obesity

et al. 2014

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Joubert syndrome (JS) is a genetically heterogeneous autosomal recessive ciliopathy with 22 genes implicated to date, including a small, ciliary GTPase, ARL13B. ARL13B is required for cilia formation in vertebrates. JS patients display multiple symptoms characterized by ataxia due to the cerebellar vermis hypoplasia, and that can also include ocular abnormalities, renal cysts, liver fibrosis or polydactyly. These symptoms are shared with other ciliopathies, some of which display additional phenotypes, such as obesity. Here we identified a novel homozygous missense variant in ARL13B/JBTS8 in a JS patient who displayed retinal defects and obesity. We demonstrate the variant disrupts ARL13B function, as its expression did not rescue the mutant phenotype either in Arl13b scorpion zebrafish or in Arl13b hennin mouse embryonic fibroblasts, while the wild-type ARL13B did. Finally, we show that ARL13B is localized within the primary cilia of neonatal mouse hypothalamic neurons consistent with the known link between hypothalamic ciliary function and obesity. Thus our data identify a novel ARL13B variant that causes JS and retinopathy and suggest an extension of the phenotypic spectrum of ARL13B mutations to obesity.

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Arl13b regulates ciliogenesis and the dynamic localization of Shh signaling proteins

Abstract: We show Arl13b is localized to the ciliary membrane and regulates tubulin modifications and ciliary length in vitro. Significantly, we found that Smoothened is enriched in Arl13b null fibroblasts, even without Sonic hedgehog stimulation, but that Glis are not similarly enriched.

Cited by 252 publications

References 51 publications

Temporal deletion of Arl13b reveals that a mispatterned neural tube corrects cell fate over time

Temporal deletion of Arl13b reveals that a mispatterned neural tube corrects cell fate over time

Diverse Cell Type-Specific Mechanisms Localize G Protein-Coupled Receptors to Caenorhabditis elegans Sensory Cilia

Identification of a novel ARL13B variant in a Joubert syndrome-affected patient with retinal impairment and obesity

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