@article {160482, title = {Coupling between spatial compartments integrates morphogenetic patterning in the organ of Corti.}, journal = {PLoS Biol}, volume = {23}, year = {2025}, month = {2025 Sep}, pages = {e3003350}, abstract = {

Morphogenetic information arises from a combination of genetically encoded cellular properties and emergent cellular behaviors. The spatio-temporal implementation of this information is critical to ensure robust, reproducible tissue shapes, yet the principles underlying its organization remain unknown. We investigated this principle using the mouse auditory epithelium, the organ of Corti (OC). OC consists of a sensory domain, which transduces sound through polar mechanosensory hair cells (HC), part of a mosaic with supporting cells (SC). On either side of the sensory domain are non-sensory domains. These domains undergo cellular rearrangements, which, together, lead to a spiral cochlea that contains planar polarized HCs. This makes the mammalian cochlea a compelling system to understand coordination across spatial scales. Using genetic and ex vivo approaches, we found patterning of OC into sensory and non-sensory domains is associated with a combinatorial expression of adhesion molecules, which underpins OC into spatially defined compartments, enabling planar cell polarity (PCP) cues to regulate compartment-specific organization. Through compartment-specific knockouts of the PCP protein, Vangl2, we find evidence of compartment coupling, a non-linear influence on the organization within one compartment when cellular organization is disrupted in another. In the OC, compartment coupling originates from vinculin-dependent junctional mechanics, coordinating cellular dynamics across spatial scales.

}, keywords = {Animals, Body Patterning, Cell Polarity, Hair Cells, Auditory, Mice, Mice, Knockout, Morphogenesis, Nerve Tissue Proteins, Organ of Corti}, issn = {1545-7885}, doi = {10.1371/journal.pbio.3003350}, author = {Prakash, Anubhav and Raman, Sukanya and Kaushik, Raman and Manchanda, Pallavi and Iyer, Anton S and Ladher, Raj K} } @article {159724, title = {Role of Pcdh15 in the development of intrinsic polarity of inner ear hair cells.}, journal = {PLoS Genet}, volume = {21}, year = {2025}, month = {2025 Aug}, pages = {e1011825}, abstract = {

In vertebrates, auditory information is transduced in the cochlea by mechanosensory hair cells (HC) through an eccentrically organised structure known as the hair bundle. This consists of a true cilium, known as the kinocilium, and modified microvilli, known as stereocilia. The hair bundle has a distinct structure with stereocilia organised in graded rows, with the longest abutting the kinocilium. The hair bundles of all HC are aligned to the tissue axis and are planar polarised. Important in the development and physiology of HC are protein bridges consisting of cadherin-23 (CDH23) and protocadherin-15 (PCDH15). These link the tips of stereocilia, where they play a role in mechanotransduction, and between the kinocilia and the stereocilia, where they are involved in development. Both Cdh23 and Pcdh15 mutations result in defects in planar polarity; however, the mechanism through which this defect arises is unclear. Using a novel mutant for the Pcdh15-CD2 isoform, we show that while the initial deflection of the kinocilium occurs, its peripheral migration to register with Gαi is perturbed. Pcdh15-CD2 genetically interacts with Gpsm2, perturbing vestibular function. We find that the earliest expression of PCDH15-CD2 is at the base of the kinocilia, and the defects in morphogenesis occur before the formation of kinocilial links. By re-introducing functional PCDH15-CD2, we show that polarity can be restored. Our data suggest that, in addition to its adhesive role, PCDH15-CD2 has an early role in intrinsic hair cell polarity through a mechanism independent of kinocilial links.

}, keywords = {Animals, Basal Bodies, Cadherin Related Proteins, Cell Polarity, Ear, Inner, Gene Knock-In Techniques, Hair Cells, Auditory, Mice, Mutation, Phosphorylation, Protein Domains, Protein Precursors, Tyrosine}, issn = {1553-7404}, doi = {10.1371/journal.pgen.1011825}, author = {Kaushik, Raman and Pandey, Shivangi and Prakash, Anubhav and Ganatra, Fenil and Abe, Takaya and Kiyonari, Hiroshi and Ladher, Raj K} } @article {147298, title = {Mosaic Atoh1 deletion in the chick auditory epithelium reveals a homeostatic mechanism to restore hair cell number.}, journal = {Dev Biol}, volume = {516}, year = {2024}, month = {2024 Jul 27}, pages = {35-46}, abstract = {

The mechanosensory hair cell of the vertebrate inner ear responds to the mechanical deflections that result from hearing or change in the acceleration due to gravity, to allow us to perceive and interpret sounds, maintain balance and spatial orientation. In mammals, ototoxic compounds, disease, and acoustic trauma can result in damage and extrusion of hair cells, without replacement, resulting in hearing loss. In contrast, non-mammalian vertebrates can regenerate sensory hair cells. Upon damage, hair cells are extruded and an associated cell type, the supporting cell is transformed into a hair cell. The mechanisms that can trigger regeneration are not known. Using mosaic deletion of the hair cell master gene, Atoh1, in the embryonic avian inner ear, we find that despite hair cells depletion at E9, by E12, hair cell number is restored in sensory epithelium. Our study suggests a homeostatic mechanism can restores hair cell number in the basilar papilla, that is activated when juxtracrine signalling is disrupted. Restoration of hair cell numbers during development may mirror regenerative processes, and our work provides insights into the mechanisms that trigger regeneration.

}, issn = {1095-564X}, doi = {10.1016/j.ydbio.2024.07.017}, author = {Singh, Nishant and Kaushik, Raman and Prakash, Anubhav and Singh Saini, Surjit and Garg, Sonal and Adhikary, Adrija and Ladher, Raj K} } @article {113534, title = {In Ovo and Ex Ovo Methods to Study Avian Inner Ear Development.}, journal = {J Vis Exp}, year = {2022}, month = {2022 Jun 16}, abstract = {

The inner ear perceives sound and maintains balance using the cochlea and vestibule. It does this by using a dedicated mechanosensory cell type known as the hair cell. Basic research in the inner ear has led to a deep understanding of how the hair cell functions, and how dysregulation can lead to hearing loss and vertigo. For this research, the mouse has been the pre-eminent model system. However, mice, like all mammals, have lost the ability to replace hair cells. Thus, when trying to understand cellular therapies for restoring inner ear function, complementary studies in other vertebrate species could provide further insights. The auditory epithelium of birds, the basilar papilla (BP), is a sheet of epithelium composed of mechanosensory hair cells (HCs) intercalated by supporting cells (SCs). Although the anatomical architecture of the basilar papilla and the mammalian cochlea differ, the molecular mechanisms of inner ear development and hearing are similar. This makes the basilar papilla a useful system for not only comparative studies but also to understand regeneration. Here, we describe dissection and manipulation techniques for the chicken inner ear. The technique shows genetic and small molecule inhibition methods, which offer a potent tool for studying the molecular mechanisms of inner ear development. In this paper, we discuss in ovo electroporation techniques to genetically perturb the basilar papilla using CRIPSR-Cas9 deletions, followed by dissection of the basilar papilla. We also demonstrate the BP organ culture and optimal use of culture matrices, to observe the development of the epithelium and the hair cells.

}, keywords = {Animals, Chickens, Cochlea, Hair Cells, Auditory, Mammals, Mice, Organ of Corti, Vestibule, Labyrinth}, issn = {1940-087X}, doi = {10.3791/64172}, author = {Singh, Nishant and Prakash, Anubhav and Chakravarthy, Suraj Ranganath and Kaushik, Raman and Ladher, Raj K} }