The Ciliary Protein Arl13b Functions Outside of the Primary Cilium in Shh-Mediated Axon Guidance

Ferent, Julien; Constable, Sandii; Gigante, Eduardo D.; Yam, Patricia T.; Mariani, Laura; Legué, Emilie; Liem, Karel F.; Caspary, Tamara; Charron, Frédéric

doi:10.1016/j.celrep.2019.11.015

Cited by 40 publications

(34 citation statements)

References 57 publications

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“…Our finding that the SCP phenotype is identical in Smo Nex-Cre and Arl13b Nex-Cre mice is consistent with a model whereby ARL13B regulates SCP projections to the dorsal thalamus via a SMO-dependent mechanism. In line with previous work showing that ARL13B does not function from within cilia to regulate Shh-guided axon guidance, we found normal SCP thalamic targeting in mice expressing only a cilia-excluded ARL13B variant (Ferent et al 2019). By mutating a conserved arginine to glutamine, we generated a mouse expressing a mutation linked to JSRD in humans and observed no change in vertebrate Hh signaling (Cantagrel et al 2008).…”

Section: Discussionsupporting

confidence: 92%

“…In the case of the Smo Nex-Cre conditional mice, it is formally possible that the SCPs do not rely on SMO for midline crossing but only for subsequent targeting to the dorsal thalamus. The fact that the Arl13b Nex-Cre conditional mice phenocopied the Smo Nex-Cre phenotype makes this less likely, since ARL13B is directly implicated in JSRD and regulates SMO-dependent axon guidance in other contexts (Cantagrel et al 2008; Ferent et al 2019). It is also plausible that the protein turnover driven by Nex-Cre completed after midline crossing occurred.…”

Section: Discussionmentioning

confidence: 99%

“…The JSRD-causing genes ARL13B and INPP5E are known to regulate vertebrate Hh signaling. In mouse models, ARL13B loss disrupts cell fate specification in the neural tube, proliferation of the cerebellar granule precursor cells in the cerebellum and Shh-directed guidance of commissural axons in the spinal cord (Caspary et al 2007; Bay et al 2018; Ferent et al 2019). These data support a model whereby disruption of Shh signaling by ARL13B mutation could provide a single mechanism underlying the MTS.…”

Section: Introductionmentioning

confidence: 99%

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Smoothened and ARL13B are critical in mouse for superior cerebellar peduncle targeting

Suciu

Long

Caspary

2021

Preprint

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Patients with the ciliopathy Joubert syndrome present with physical anomalies, intellectual disability, and are diagnosed by the hindbrain “molar tooth sign” malformation. This radiological abnormality results from a combination of hypoplasia of the cerebellar vermis and inappropriate targeting of the white matter tracts of the superior cerebellar peduncles, which create a deepened interpeduncular fossa. ARL13B is a cilia-enriched regulatory GTPase established to regulate cell fate, cell proliferation and axon guidance through vertebrate Hedgehog signaling. In patients, point mutations in ARL13B cause Joubert syndrome. In order to understand the etiology of the molar tooth sign, we used mouse models to investigate the role of ARL13B during cerebellar development. We found ARL13B regulates superior cerebellar peduncle targeting and these fiber tracts require Hedgehog signaling for proper guidance. However, in mouse the Joubert-causing R79Q mutation in ARL13B does not disrupt Hedgehog signaling nor does it impact tract targeting. We found a small cerebellar vermis in mice lacking ARL13B function but no cerebellar vermis hypoplasia in mice expressing the Joubert-causing R79Q mutation. Additionally, mice expressing a cilia-excluded variant of ARL13B that transduces Hedgehog normally, showed normal tract targeting and vermis size. Taken together, our data indicate that ARL13B is critical for superior cerebellar peduncle targeting, likely via Hedgehog signaling, as well as control of cerebellar vermis size. Thus, our work highlights the complexity of ARL13B in molar tooth sign etiology.Summary statementJoubert syndrome is diagnosed by the hindbrain “molar tooth sign” malformation. Using mouse models, we show loss of the ciliary GTPase ARL13B, mutations in which lead to Joubert syndrome, result in two features of the molar tooth sign: hypoplasia of the cerebellar vermis and inappropriate targeting of the superior cerebellar peduncles. Furthermore, we demonstrate that loss of vertebrate Hedgehog signaling may be the underlying disrupted mechanism as we extend its role in axon guidance to the superior cerebellar peduncles.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Smoothened and ARL13B are critical in mouse for superior cerebellar peduncle targeting

Suciu

Long

Caspary

2021

Preprint

Self Cite

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“…We used immunocytochemistry to identify neuronal cilia during both cell proliferation and after various days past the induction of differentiation into functional neurons. ADP Ribosylation Factor Like GTPase 13B (ARL13B) is a widely used marker for cilia that is specifically and strongly enriched in the cilium (Caspary et al, 2007, 2016; Ferent et al, 2019). Immunofluorescence stainings revealed that ARL13B is expressed and specifically localized in LUHMES cells at the stage of cell proliferation (d0) as well as during differentiation into neurons (d1 to d6) ( Figure 1A ), suggesting that LUHMES cells and neurons are ciliated.…”

Section: Resultsmentioning

confidence: 99%

Differentiation of ciliated human midbrain-derived LUHMES neurons

Lauter

Coschiera

Yoshihara

et al. 2020

Preprint

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“…Furthermore, treatment with the agonist (SAG) and antagonist (Cyclo) of SMO indicated that the Hh signaling pathway is transduced in DC2 cells, as confirmed by the detection of GLI3 isoforms and expression of Rasl11b, a Hh signaling target gene 42 . While it is well established that canonical Hh signaling is transduced through the PC in vertebrates, and that impairment of primary ciliogenesis triggers a decrease in Hh signaling, 28,43‐45 the existence of noncanonical Hh signaling outside the PC has been reported 46,47 . To assess the contribution of the PC to Hh signaling in DC2 cells, we inhibited the cytoplasmic motor dynein with ciliobrevin D, which triggered a significant decrease in PC length along the entire length of the epididymis and on DC2 treated cells.…”

Section: Discussionmentioning

confidence: 99%

Hedgehog signaling pathway regulates gene expression profile of epididymal principal cells through the primary cilium

et al. 2020

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Primary cilia (PC) are organelles that sense and respond to dynamic changes of the extracellular milieu through the regulation of target genes. By using the epididymis as a model system, we determined the contribution of primary cilia in the regulation of epithelial cell functions through the transduction of the Hedgehog (Hh) signaling pathway. Both Sonic (SHH) and Indian Hedgehog (IHH) ligands were detected in epididymal epithelial cells by confocal microscopy and found secreted in the extracellular space. Gene expression profiling preformed on ciliated epithelial cells indicated that 153 and 1052 genes were differentially expressed following treatment with the Hh agonist SAG or the Hh antagonist cyclopamine (Cyclo), respectively. Strikingly, gene ontology analysis indicated that genes associated with immune response were the most affected following Hh modulation. The contribution of epididymal PC to canonical Hh pathway transduction was validated by ciliobrevin D treatment, which induced a significant decrease in PC length and a reduction in the expression Hh signaling targets. Such findings bring us closer to a molecular understanding of the subtle immune balance observed in some epithelia, including the epididymis and the intestine, which are organs featuring both tolerance toward autoimmune spermatozoa (or commensal bacteria) and defense against pathogens.

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The Ciliary Protein Arl13b Functions Outside of the Primary Cilium in Shh-Mediated Axon Guidance

Abstract: Highlights d Arl13b null mutant mice display commissural axon guidance defects d Arl13b is required for Shh-mediated growth cone attraction d Cilia-deficient Arl13b is sufficient for its role in axon guidance

Cited by 40 publications

References 57 publications

Smoothened and ARL13B are critical in mouse for superior cerebellar peduncle targeting

Smoothened and ARL13B are critical in mouse for superior cerebellar peduncle targeting

Differentiation of ciliated human midbrain-derived LUHMES neurons

Hedgehog signaling pathway regulates gene expression profile of epididymal principal cells through the primary cilium

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