Primary Cilia, Sonic Hedgehog Signaling, and Spinal Cord Development

Most studies on the origin of oligodendrocyte lineage have been performed in the spinal cord. By contrast, molecular mechanisms that regulate the appearance of the oligodendroglial lineage in the brain have not yet attracted much attention. We provide evidence for three distinct sources of oligodendrocytes in the mouse telencephalon. In addition to two subpallial ventricular foci, the anterior entopeduncular area and the medial ganglionic eminence, the rostral telencephalon also gives rise to oligodendrocytes. We show that oligodendrocytes in the olfactory bulb are generated within the rostral pallium from ventricular progenitors characterized by the expression of Plp. We provide evidence that these Plp oligodendrocyte progenitors do not depend on signal transduction mediated by platelet-derived growth factor receptors (PDGFRs), and therefore propose that they belong to a different lineage than the PDGFRα-expressing progenitors. Moreover, induction of oligodendrocytes in the telencephalon is dependent on sonic hedgehog signaling, as in the spinal cord. In all these telencephalic ventricular territories, oligodendrocyte progenitors were detected at about the same developmental stage as in the spinal cord. However, both in vivo and in vitro, the differentiation into O4-positive pre-oligodendrocytes was postponed by 4-5 days in the telencephalon in comparison with the spinal cord. This delay between determination and differentiation appears to be intrinsic to telencephalic oligodendrocytes, as it was not shortened by diffusible or cell-cell contact factors present in the spinal cord.

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A novel role for primary cilia in airway remodeling

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00284.2016 ◽

2017 ◽

Vol 313 (2) ◽

pp. L328-L338 ◽

Cited By ~ 1

Author(s):

Carol S. Trempus ◽

Weifeng Song ◽

Ahmed Lazrak ◽

Zhihong Yu ◽

Judy R. Creighton ◽

...

Keyword(s):

Sonic Hedgehog ◽

Hedgehog Signaling ◽

Primary Cilia ◽

Calcium Influx ◽

Airway Remodeling ◽

Critical Role ◽

Calcium Flux ◽

Airway Smooth Muscle Cells ◽

Mechanical Stimuli ◽

Sonic Hedgehog Signaling

Primary cilia (PC) are solitary cellular organelles that play critical roles in development, homeostasis, and disease pathogenesis by modulating key signaling pathways such as Sonic Hedgehog and calcium flux. The antenna-like shape of PC enables them also to facilitate sensing of extracellular and mechanical stimuli into the cell, and a critical role for PC has been described for mesenchymal cells such as chondrocytes. However, nothing is known about the role of PC in airway smooth muscle cells (ASMCs) in the context of airway remodeling. We hypothesized that PC on ASMCs mediate cell contraction and are thus integral in the remodeling process. We found that PC are expressed on ASMCs in asthmatic lungs. Using pharmacological and genetic methods, we demonstrated that PC are necessary for ASMC contraction in a collagen gel three-dimensional model both in the absence of external stimulus and in response to the extracellular component hyaluronan. Mechanistically, we demonstrate that the effect of PC on ASMC contraction is, to a small extent, due to their effect on Sonic Hedgehog signaling and, to a larger extent, due to their effect on calcium influx and membrane depolarization. In conclusion, PC are necessary for the development of airway remodeling by mediating calcium flux and Sonic Hedgehog signaling.

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ARL13B regulates Sonic Hedgehog signaling from outside primary cilia

10.1101/711671 ◽

2019 ◽

Author(s):

Eduardo D. Gigante ◽

Megan R. Taylor ◽

Anna A. Ivanova ◽

Richard A. Kahn ◽

Tamara Caspary

Keyword(s):

Signal Transduction ◽

Sonic Hedgehog ◽

Protein Trafficking ◽

Hedgehog Signaling ◽

Primary Cilia ◽

Complete Loss ◽

Wild Type ◽

Sonic Hedgehog Signaling ◽

Biochemical Function

AbstractARL13B is a regulatory GTPase highly enriched in cilia. Complete loss of Arl13b disrupts cilia architecture, protein trafficking and Sonic hedgehog signaling. To determine whether ARL13B is required within cilia, we knocked in a cilia-excluded variant of ARL13B (V358A) and showed it retains all known biochemical function. We found that ARL13BV358A protein was expressed but could not be detected in cilia, even when retrograde ciliary transport was blocked. We showed Arl13bV358A/V358A mice are viable and fertile with normal Shh signal transduction. However, in contrast to wild type cilia, Arl13bV358A/V358A cells displayed short cilia and lacked ciliary ARL3 and INPP5E. These data indicate that ARL13B’s role within cilia can be uncoupled from its function outside of cilia. Furthermore, these data imply that the cilia defects upon complete absence of ARL13B do not underlie the alterations in Shh transduction, which is unexpected given the requirement of cilia for Shh transduction.

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Author response: ARL13B regulates Sonic hedgehog signaling from outside primary cilia

10.7554/elife.50434.sa2 ◽

2019 ◽

Author(s):

Eduardo D Gigante ◽

Megan R Taylor ◽

Anna A Ivanova ◽

Richard A Kahn ◽

Tamara Caspary

Keyword(s):

Sonic Hedgehog ◽

Hedgehog Signaling ◽

Primary Cilia ◽

Author Response ◽

Sonic Hedgehog Signaling

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ARL13B regulates Sonic hedgehog signaling from outside primary cilia

eLife ◽

10.7554/elife.50434 ◽

2020 ◽

Vol 9 ◽

Cited By ~ 6

Author(s):

Eduardo D Gigante ◽

Megan R Taylor ◽

Anna A Ivanova ◽

Richard A Kahn ◽

Tamara Caspary

Keyword(s):

Signal Transduction ◽

Sonic Hedgehog ◽

Protein Trafficking ◽

Hedgehog Signaling ◽

Primary Cilia ◽

Complete Loss ◽

Wild Type ◽

Sonic Hedgehog Signaling ◽

Biochemical Function

ARL13B is a regulatory GTPase highly enriched in cilia. Complete loss of Arl13b disrupts cilia architecture, protein trafficking and Sonic hedgehog signaling. To determine whether ARL13B is required within cilia, we knocked in a cilia-excluded variant of ARL13B (V358A) and showed it retains all known biochemical function. We found that ARL13BV358A protein was expressed but could not be detected in cilia, even when retrograde ciliary transport was blocked. We showed Arl13bV358A/V358A mice are viable and fertile with normal Shh signal transduction. However, in contrast to wild type cilia, Arl13bV358A/V358A cells displayed short cilia and lacked ciliary ARL3 and INPP5E. These data indicate that ARL13B’s role within cilia can be uncoupled from its function outside of cilia. Furthermore, these data imply that the cilia defects upon complete absence of ARL13B do not underlie the alterations in Shh transduction, which is unexpected given the requirement of cilia for Shh transduction.

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Trisomy 21 induces pericentrosomal crowding disrupting early stages of primary ciliogenesis and mouse cerebellar development

10.1101/2021.11.10.468107 ◽

2021 ◽

Author(s):

Cayla E Jewett ◽

Bailey L McCurdy ◽

Eileen T O'Toole ◽

Katherine S Given ◽

Carrie H Lin ◽

...

Keyword(s):

Down Syndrome ◽

Sonic Hedgehog ◽

Trisomy 21 ◽

Hedgehog Signaling ◽

Primary Cilia ◽

Chromosome 21 ◽

Sonic Hedgehog Signaling ◽

Trafficking Defects ◽

Microtubule Networks

Primary cilia are signaling organelles essential for development and homeostasis. Loss of primary cilia is lethal, and decreased or defective cilia cause multisystemic conditions called ciliopathies. Down syndrome shares clinical overlap with ciliopathies. We previously showed that trisomy 21 diminishes primary cilia formation and function due to elevated Pericentrin, a centrosome protein encoded on chromosome 21. Pericentrin is mislocalized, creating aggregates that disrupt pericentrosomal trafficking and microtubule organization. Here, we examine the cilia-related molecules and pathways disrupted in trisomy 21 and their in vivo phenotypic relevance. Utilizing ciliogenesis time course experiments, we reveal how Pericentrin, microtubule networks, and components of ciliary vesicles are reorganized for ciliogenesis in euploid cells. Early in ciliogenesis, chromosome 21 polyploidy results in elevated Pericentrin and microtubule networks away from the centrosome that ensnare MyosinVA and EHD1, blocking mother centriole uncapping that is essential for ciliogenesis. Ciliated trisomy 21 cells have persistent trafficking defects that reduce transition zone protein localization, which is critical for Sonic hedgehog signaling. Sonic hedgehog signaling is decreased and anticorrelates with Pericentrin levels in trisomy 21 primary mouse embryonic fibroblasts. Finally, we observe decreased ciliation in vivo. A mouse model of Down syndrome with elevated Pericentrin has fewer primary cilia in cerebellar granule neuron progenitors and thinner external granular layers. Our work reveals that elevated Pericentrin in trisomy 21 disrupts multiple early steps of ciliogenesis and creates persistent trafficking defects in ciliated cells. This pericentrosomal crowding results in signaling defects consistent with the neurological deficits found in individuals with Down syndrome.

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Arl13b regulates Sonic Hedgehog signaling from outside primary cilia

10.1242/prelights.13242 ◽

2019 ◽

Author(s):

Alex Eve

Keyword(s):

Sonic Hedgehog ◽

Hedgehog Signaling ◽

Primary Cilia ◽

Sonic Hedgehog Signaling

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Platelet-derived growth factor-A and sonic hedgehog signaling direct lung fibroblast precursors during alveolar septal formation

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00011.2013 ◽

2013 ◽

Vol 305 (3) ◽

pp. L229-L239 ◽

Cited By ~ 33

Author(s):

Stephen E. McGowan ◽

Diann M. McCoy

Keyword(s):

Growth Factor ◽

Gas Exchange ◽

Sonic Hedgehog ◽

Hedgehog Signaling ◽

Primary Cilia ◽

Platelet Derived Growth Factor ◽

Lung Fibroblasts ◽

Alveolar Cells ◽

Sonic Hedgehog Signaling

Alveolar septal formation is required to support the respiration of growing mammals; in humans effacement of the alveolar surface and impaired gas exchange are critical features of emphysema and pulmonary fibrosis. Platelet-derived growth factor-A (PDGF-A) and its receptor PDGF-receptor-α (PDGFRα) are required for secondary septal elongation in mice during postnatal days 4 through 12 and they regulate the proliferation and septal location of interstitial fibroblasts. We examined lung fibroblasts (LF) to learn whether PDGFRα expression distinguished a population of precursor cells, with enhanced proliferative and migratory capabilities. We identified a subpopulation of LF that expresses sonic hedgehog (Shh) and stem cell antigen-1 (Sca1). PDGF-A and Shh both increased cytokinesis and chemotaxis in vitro, but through different mechanisms. In primary LF cultures, Shh signaled exclusively through a noncanonical pathway involving generation of Rac1-GTP, whereas both the canonical and noncanonical pathways were used by the Mlg neonatal mouse LF cell line. LF preferentially oriented their primary cilia toward their anterior pole during migration. Furthermore, a larger proportion of PDGFRα-expressing LF, which are more abundant at the septal tips, bore primary cilia compared with other alveolar cells. In pulmonary emphysema, destroyed alveolar septa do not regenerate, in part because cells fail to assume a configuration that allows efficient gas exchange. Better understanding how LF are positioned during alveolar development could identify signaling pathways, which promote alveolar septal regeneration.

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