Lamellar projections in the endolymphatic sac act as a relief valve to regulate inner ear pressure

oleh: Ian A Swinburne, Kishore R Mosaliganti, Srigokul Upadhyayula, Tsung-Li Liu, David G C Hildebrand, Tony Y -C Tsai, Anzhi Chen, Ebaa Al-Obeidi, Anna K Fass, Samir Malhotra, Florian Engert, Jeff W Lichtman, Tomas Kirchhausen, Eric Betzig, Sean G Megason

Format: Article
Diterbitkan: eLife Sciences Publications Ltd 2018-06-01

Deskripsi

The inner ear is a fluid-filled closed-epithelial structure whose function requires maintenance of an internal hydrostatic pressure and fluid composition. The endolymphatic sac (ES) is a dead-end epithelial tube connected to the inner ear whose function is unclear. ES defects can cause distended ear tissue, a pathology often seen in hearing and balance disorders. Using live imaging of zebrafish larvae, we reveal that the ES undergoes cycles of slow pressure-driven inflation followed by rapid deflation. Absence of these cycles in lmx1bb mutants leads to distended ear tissue. Using serial-section electron microscopy and adaptive optics lattice light-sheet microscopy, we find a pressure relief valve in the ES comprised of partially separated apical junctions and dynamic overlapping basal lamellae that separate under pressure to release fluid. We propose that this lmx1-dependent pressure relief valve is required to maintain fluid homeostasis in the inner ear and other fluid-filled cavities.