Development of a stereocilia bundle on the apical surface of a mouse nascent inner ear hair cell expressing green fluorescence protein (GFP) tagged-beta-actin. The nascent hair cell was imaged live on a spinning-disc confocal microscope with a Zeiss 63X objective at one-hour intervals for approximately 3 days.This is one of 112 movies available as a supplement to Drummond, et al., 2015 Nature Communications doi 10.1038/ncommons7873: www.ncbi.nlm.nih.gov/pubmed/ 25898120.
In the inner ear, there are cells that have long finger-like projections on top of a special cell called a hair cell. These projections are called "stereocilia," and they are necessary for our ability to detect sound. Stereocilia are delicate structures and are easily damaged by loud sound and some drugs. Once damaged, stereocilia do not regenerate. For that matter, we don’t know much about how stereocilia form in the first place. We do know that stereocilia develop from tiny projections called microvilli that are present on many other cell types in our body. Until now, nobody has visualized the development of a bundle of stereocilia in a living nascent hair cell. This movie, which lasts 21 seconds, is a record of stereocilia development over 62 hours. The movie shows tiny microvilli elongating on the surface of a round hair cell to form long, mature streocilia. The movie images are visually similar to blades of grass growing from short seedlings in a flower pot. The short "seedling-like" stereocilia grow in length to form a bundle of many mature stereocilia. The mature stereocilia function to process sound and the motion of one’s head that is necessary for balance.