The molecular dynamics of subdistal appendages in multi-ciliated cells

The motile cilia of ependymal cells coordinate their beats to facilitate a forceful and directed flow of cerebrospinal fluid (CSF). Each cilium originates from a basal body with a basal foot protruding from one side. A uniform alignment of these basal feet is crucial for the coordination of ciliary beating. The process by which the basal foot originates from subdistal appendages of the basal body, however, is unresolved. Here, we show FGFR1 Oncogene Partner (FOP) is a useful marker for delineating the transformation of a circular, unpolarized subdistal appendage into a polarized structure with a basal foot. Ankyrin repeat and SAM domain-containing protein 1A (ANKS1A) interacts with FOP to assemble region I of the basal foot. Importantly, disruption of ANKS1A reduces the size of region I. This produces an unstable basal foot, which disrupts rotational polarity and the coordinated beating of cilia in young adult mice. ANKS1A deficiency also leads to severe degeneration of the basal foot in aged mice and the detachment of cilia from their basal bodies. This role of ANKS1A in the polarization of the basal foot is evolutionarily conserved in vertebrates. Thus, ANKS1A regulates FOP to build and maintain the polarity of subdistal appendages.

Principal component analysis of avian hind limb and foot morphometrics and the relationship between ecology and phylogeny

Principal component analysis has been used to test for similarities in ecology and life habit between modern and fossil birds; however, the two main portions of the hind limb—the foot and the long bone elements—have not been examined separately. We examine the potential links between morphology, ecology, and phylogeny through a synthesis of phylogenetic paleoecological methods and morphospace analysis. Both hind limb morphologies and species’ ecologies exhibit extreme phylogenetic clumping, although these patterns are at least partially explainable by a Brownian motion style of evolution. Some morphologies are strongly correlated with particular ecologies, while some ecologies are occupied by a variety of morphologies. Within the morphospace analyses, the length of the hallux (toe I) is the most defining characteristic of the entire hind limb. The foot and hind limb are represented on different axes when all measurements are considered in an analysis, suggesting that these structures undergo morphological change separately from each other. Early birds tend to cluster together, representing an unspecialized basal foot morphotype and a hind limb reliant on hip-driven, not knee-driven, locomotion. Direct links between morphology, ecology, and phylogeny are unclear and complicated and may be biased due to sample size (~60 species). This study should be treated as a preliminary analysis that further studies, especially those examining the vast diversity of modern birds, can build upon.

Super-resolution Molecular Map of Basal Foot Reveals Novel Cilium in Airway Multiciliated Cells

Motile cilia are beating machines that play a critical role in airway defense. During airway cell differentiation, hundreds of motile cilia are templated from basal bodies that extend a basal foot, an appendage that links motile cilia together to ensure beating coordination. This assembly has thus far escaped structural analysis because its size is below the resolution limit. Here, we determine the molecular architecture and identify basal foot proteins using a super-resolution-driven approach. Quantitative super-resolution image analysis shows that the basal foot is organized in three main regions linked by elongated coiled-coil proteins. FIB-SEM tomography and comparative super-resolution mapping of basal feet reveal that, among hundreds of motile cilia of an airway cell, a hybrid cilium with features of primary and motile cilia is harbored. The hybrid cilium is conserved in mammalian multiciliated cells and originates from parental centrioles. We further demonstrate that this novel cilium is a signalling centre whose cellular position is dependent on flow.

Two appendages homologous between basal bodies and centrioles are formed using distinct Odf2 domains

Ciliogenesis is regulated by context-dependent cellular cues, including some transduced through appendage-like structures on ciliary basal bodies called transition fibers and basal feet. However, the molecular basis for this regulation is not fully understood. The Odf2 gene product, ODF2/cenexin, is essential for both ciliogenesis and the formation of the distal and subdistal appendages on centrioles, which become basal bodies. We examined the effects of Odf2 deletion constructs on ciliogenesis in Odf2-knockout F9 cells. Electron microscopy revealed that ciliogenesis and transition fiber formation required the ODF2/cenexin fragment containing amino acids (aa) 188–806, whereas basal foot formation required aa 1–59 and 188–806. These sequences also formed distal and subdistal appendages, respectively, indicating that the centriole appendages are molecularly analogous to those on basal bodies. We used the differential formation of appendages by Odf2 deletion constructs to study the incorporation and function of molecules associated with each appendage type. We found that transition fibers and distal appendages were required for ciliogenesis and subdistal appendages stabilized the centrosomal microtubules.

Phoenix canariensis: Canary Island Date Palm

The Canary Island date palm is native to the Canary Islands. Although it can reach heights of 40–50 feet, it is slow growing and requires many years to attain that height. It has 8- to 15-foot-long rigid leaves that contain up to 200 V-shaped leaflets, the basal ones of which are modified into long, sharp spines. Leaves are not self-cleaning and must be manually removed when dead, but the leaf bases eventually rot off, leaving an attractive diamond-shaped pattern of leaf scars on the 2- to 3-foot-diameter trunk. On older specimens, the basal foot or so of the trunk typically is covered with short root initials. This 6-page fact sheet was written by T. K. Broschat, and published by the UF Department of Environmental Horticulture, August 2013. http://edis.ifas.ufl.edu/st439

The establishment of rotational polarity in the airway and ependymal cilia: analysis with a novel cilium motility mutant mouse

The airway is covered by multicilia that beat in a metachronous manner toward the mouth to eliminate debris and infectious particles. Coordinated one-directional beating is an essential feature of multicilia in the airway to guarantee proper mucociliary clearance. Defects in ciliary motility lead to primary ciliary dyskinesia (PCD), with major symptoms including bronchitis and other chronic respiratory diseases. Recent work suggested that ciliary motility and planar polarity are required in the process of ciliary alignment that produces coordinated beating. However, the extent to which cilia motility is involved in this process in mammals has not yet been fully clarified. Here, to address the role of ciliary motility in the process of coordinated ciliary alignment, we analyzed Kintoun mice mutants ( Ktu−/−). Ktu−/− exhibited typical phenotypes of PCD with complete loss of ciliary motility in trachea and another ciliated tissue, the brain ependyma. Immunohistochemistry using antibodies against axonemal dynein confirmed the loss of multiple axonemal dynein components in mutant cilia. Observation of cilia orientation based on basal foot directions revealed that ciliary motility was not required in the alignment of airway cilia, whereas a strong requirement was observed in brain ependymal cells. Thus we conclude that the involvement of ciliary motility in the establishment of coordinated ciliary alignment varies among tissues.