Swinburne, IanMosaliganti, Kishore RUpadhyayula, SrigokulLiu, Tsung-LiHildebrand, DavidTsai, Tony Y -CChen, AnzhiAl-Obeidi, EbaaFass, Anna KMalhotra, SamirEngert, FlorianLichtman, JeffKirchausen, TomasBetzig, EricMegason, Sean2018-07-252018Swinburne, I. A., K. R. Mosaliganti, S. Upadhyayula, T. Liu, D. G. C. Hildebrand, T. Y. -. Tsai, A. Chen, et al. 2018. “Lamellar projections in the endolymphatic sac act as a relief valve to regulate inner ear pressure.” eLife 7 (1): e37131. doi:10.7554/eLife.37131. http://dx.doi.org/10.7554/eLife.37131.http://nrs.harvard.edu/urn-3:HUL.InstRepos:37298501The 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.en-USinner earpressuretimelapselamellavalveZebrafishJournal Article2018-07-2510.7554/eLife.37131