Biology subjects

Nanjundappa, R.

Publications and source records attributed to Nanjundappa, R..

3 recordsLinked to original sources

bioRxiv2024

Loss of an extensive ciliary connectome induces proteostasis and cell fate switching in a severe motile ciliopathy

Motile cilia have essential cellular functions in development, reproduction, and homeostasis. Genetic causes for motile ciliopathies have been identified, but the consequences on cellular functions beyond impaired motility remain unknown. Variants in CCDC39 and CCDC40 cause severe disease not explained by loss of motility. Using human cells with pathological variants in these genes, Chlamydomonas genetics, cryo-electron microscopy, single cell RNA transcriptomics, and proteomics, we identified perturbations in multiple cilia-independent pathways. Absence of the axonemal CCDC39/CCDC40 heterodimer results in loss of a connectome of over 90 proteins. The undocked connectome activates cell quality control pathways, switches multiciliated cell fate, impairs microtubule architecture, and creates a defective periciliary barrier. Both cilia-dependent and independent defects are likely responsible for the disease severity. Our findings provide a foundation for reconsidering the broad cellular impact of pathologic variants in ciliopathies and suggest new directions for therapies.

cell biology↗

bioRxiv2018

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.

cell biology↗

bioRxiv2018

Regulation of Cilia Abundance in Multiciliated Cells

Multiciliated cells (MCC) are specialized epithelia that contain hundreds of motile cilia used to propel fluid over the surface of the cell. To template these cilia, each MCC produces hundreds of centrioles by a process termed centriole amplification. Airway progenitor cells initially contain two parental centrioles that nucleate multiple centrioles at once, and structures called deuterosomes that assemble the vast majority of centrioles during amplification. Remarkably, how each cell regulates the precise number of its centrioles and cilia remains unknown. Here, we investigate mechanisms that establish centriole number in MCC using an ex vivo airway culture model. We show that ablation of parental centrioles, via inhibition of Plk4 kinase, does not perturb deuterosome formation and centriole amplification, nor alter the total complement of centrioles per cell. Airway MCC vary in size and surface area, and exhibit a broad range in centriole number. Quantification of centriole abundance in vitro and in vivo identified a direct relationship between cell-surface area and centriole number. By manipulating cell size and shape, we discovered that centriole number scales with increasing surface area. Collectively, our results demonstrate that parental centrioles and Plk4 are dispensable for deuterosome formation, centriole amplification, and establishment of centriole number. Instead, a cell-intrinsic surface area-dependent mechanism controls centriole and cilia abundance in multiciliated cells.

cell biology↗