Multicilia dynamically transduce Sonic Hedgehog signaling to regulate choroid plexus functions.

The choroid plexus is a major site for cerebrospinal fluid (CSF) production, characterized by a multiciliated epithelial monolayer that regulates CSF production. We demonstrate that defective choroid plexus ciliogenesis or intraflagellar transport yields neonatal hydrocephalus, at least in part due to increased water channel Aqp1 and ion transporter Atp1a2 expression. We demonstrate choroid plexus multicilia as sensory cilia, transducing both canonical and non-canonical Sonic Hedgehog (Shh) signaling.

Multicilia dynamically transduce Shh signaling to regulate choroid plexus functions.

Choroid plexus is a major site for cerebrospinal fluid (CSF) production, characterized by a multiciliated epithelial monolayer that regulates CSF production. We demonstrate that defective choroid plexus ciliogenesis or Intraflagellar transport yields neonatal hydrocephalus, at least in part, due to increased water channel Aqp1 and ion transporter Atp1a2 expression. We demonstrate choroid plexus multicilia as sensory cilia, transducing both canonical and non-canonical Shh signaling.

An alternative cell cycle coordinates multiciliated cell differentiation.

The canonical mitotic cell cycle coordinates DNA replication, centriole duplication and cytokinesis to generate two cells from one. Some cells, such as mammalian trophoblast giant cells, use cell cycle variants like the endocycle to bypass mitosis. Differentiating multiciliated cells, found in the mammalian airway, brain ventricles and reproductive tract, are post-mitotic but generate hundreds of centrioles, each of which matures into a basal body and nucleates a motile cilium.

An RFX transcription factor regulates ciliogenesis in the closest living relatives of animals.

Cilia allowed our protistan ancestors to sense and explore their environment, avoid predation, and capture bacterial prey. Regulated ciliogenesis was likely critical for early animal evolution, and in modern animals, deploying cilia in the right cells at the right time is crucial for development and physiology. Two transcription factors, RFX and FoxJ1, coordinate ciliogenesis in animals but are absent from the genomes of many other ciliated eukaryotes, raising the question of how the regulation of ciliogenesis in animals evolved.

Vertebrate cells differentially interpret ciliary and extraciliary cAMP.

Hedgehog pathway components and select G protein-coupled receptors (GPCRs) localize to the primary cilium, an organelle specialized for signal transduction. We investigated whether cells distinguish between ciliary and extraciliary GPCR signaling. To test whether ciliary and extraciliary cyclic AMP (cAMP) convey different information, we engineered optogenetic and chemogenetic tools to control the subcellular site of cAMP generation.

Flow-Cytometric Analysis and Purification of Airway Epithelial-Cell Subsets.

The human airway epithelium is essential in homeostasis, and epithelial dysfunction contributes to chronic airway disease. Development of flow-cytometric methods to characterize subsets of airway epithelial cells will enable further dissection of airway epithelial biology. Leveraging single-cell RNA-sequencing data in combination with known cell type-specific markers, we developed panels of antibodies to characterize and isolate the major airway epithelial subsets (basal, ciliated, and secretory cells) from human bronchial epithelial-cell cultures.

Evolutionary Proteomics Uncovers Ancient Associations of Cilia with Signaling Pathways.

Cilia are organelles specialized for movement and signaling. To infer when during evolution signaling pathways became associated with cilia, we characterized the proteomes of cilia from sea urchins, sea anemones, and choanoflagellates. We identified 437 high-confidence ciliary candidate proteins conserved in mammals and discovered that Hedgehog and G-protein-coupled receptor pathways were linked to cilia before the origin of bilateria and transient receptor potential (TRP) channels before the origin of animals.

Mutations in CCDC11, which encodes a coiled-coil containing ciliary protein, causes situs inversus due to dysmotility of monocilia in the left-right organizer.

In vertebrates, establishment of left-right (LR) asymmetry is dependent on cilia-driven fluid flow within the LR organizer. Mutations in CCDC11 disrupt LR asymmetry in humans, but how the gene functions in LR patterning is presently unknown. We describe a patient with situs inversus totalis carrying homozygous loss-of-function mutations in CCDC11.

A function for the Joubert syndrome protein Arl13b in ciliary membrane extension and ciliary length regulation.

Cilia perform a variety of functions in a number of developmental and physiological contexts, and are implicated in the pathogenesis of a wide spectrum of human disorders. While the ciliary axoneme is assembled by intraflagellar transport, how ciliary membrane length is regulated is not completely understood. Here, we show that zebrafish embryos as well as mammalian cells overexpressing the ciliary membrane protein Arl13b, an ARF family small GTPase that is essential for ciliary differentiation, showed pronounced increase in ciliary length.

Systematic discovery of novel ciliary genes through functional genomics in the zebrafish.

Cilia are microtubule-based hair-like organelles that play many important roles in development and physiology, and are implicated in a rapidly expanding spectrum of human diseases, collectively termed ciliopathies. Primary ciliary dyskinesia (PCD), one of the most prevalent of ciliopathies, arises from abnormalities in the differentiation or motility of the motile cilia. Despite their biomedical importance, a methodical functional screen for ciliary genes has not been carried out in any vertebrate at the organismal level.

Switching on cilia: transcriptional networks regulating ciliogenesis.

Cilia play many essential roles in fluid transport and cellular locomotion, and as sensory hubs for a variety of signal transduction pathways. Despite having a conserved basic morphology, cilia vary extensively in their shapes and sizes, ultrastructural details, numbers per cell, motility patterns and sensory capabilities. Emerging evidence indicates that this diversity, which is intimately linked to the different functions that cilia perform, is in large part programmed at the transcriptional level.

Specification of vertebrate slow-twitch muscle fiber fate by the transcriptional regulator Blimp1.

Skeletal muscles of vertebrates are typically composed of slow- and fast-twitch fibers that differ in their morphology, gene expression profiles, contraction speeds, metabolic properties and patterns of innervation. During myogenesis, how muscle precursors are induced to mature into distinct slow- or fast-twitch fiber-types is inadequately understood. We have previously shown that within the somites of the zebrafish embryo, the activity of the zinc finger and SET domain-containing transcriptional regulator Blimp1 is essential for the specification of slow muscle fibers.

Prospero acts as a binary switch between self-renewal and differentiation in Drosophila neural stem cells.

Stem cells have the remarkable ability to give rise to both self-renewing and differentiating daughter cells. Drosophila neural stem cells segregate cell-fate determinants from the self-renewing cell to the differentiating daughter at each division. Here, we show that one such determinant, the homeodomain transcription factor Prospero, regulates the choice between stem cell self-renewal and differentiation.

Turning back the clock on neural progenitors.

Drosophila neural progenitor cells, or neuroblasts, alter their transcriptional profile over time to produce different neural cell types. A recent paper by Pearson and Doe shows that older neuroblasts can be reprogrammed to behave like young neuroblasts, and to produce early neural cell types, simply by expressing the transcription factor, Hunchback. The authors show that competence to respond to Hunchback diminishes over time.

amontillado, the Drosophila homolog of the prohormone processing protease PC2, is required during embryogenesis and early larval development.

Biosynthesis of most peptide hormones and neuropeptides requires proteolytic excision of the active peptide from inactive proprotein precursors, an activity carried out by subtilisin-like proprotein convertases (SPCs) in constitutive or regulated secretory pathways. The Drosophila amontillado (amon) gene encodes a homolog of the mammalian PC2 protein, an SPC that functions in the regulated secretory pathway in neuroendocrine tissues. We have identified amon mutants by isolating ethylmethanesulfonate (EMS)-induced lethal and visible mutations that define two complementation groups in the amon interval at 97D1 of the third chromosome.