When we used a Fourier face mask to reveal the location of highly hexagonal regions of these wild-type stereocilia, we found that central areas had a higher degree of hexagonal packing (Fig. of actin-binding proteins (Chhabra and Higgs, 2007; Michelot and Drubin, 2011). A special subset of these arrays comprises membrane-enveloped protrusions of tightly bundled parallel actin filaments, which include filopodia, microvilli, and inner hearing stereocilia. These protrusions enhance cells capabilities to transduce extracellular signals and transport essential metabolites (Gupton and Gertler, 2007; Crawley et al., 2014). Stereocilia of the inner ear’s sensory hair cells are particularly exaggerated examples of actin protrusions. Dozens to hundreds of coupled stereocilia make up SR 48692 the hair package, the organelle in the inner hearing that transduces sound or head motions into electrical signals (Fig. 1 A). Each stereocilium is definitely filled with a paracrystalline array of parallel actin filaments; SR 48692 an interfilament range of 10 nm (Tilney et al., 1980) shows that cross-linking is performed by tight actin cross-linkers, which include the espin, fascin, and plastin family members (Volkmann et al., 2001; Purdy et al., 2007; Jansen et al., 2011). Indeed, fascin 2 (FSCN2), plastin 1 (PLS1), and espin (ESPN) have each been reported to be abundant in hair cells (Tilney et al., 1989; Zheng et al., 2000; Shin et al., 2010; Fig. 1 B). Bundled, parallel actin filaments in biological constructions are packed either hexagonally or with liquid order, where the filaments display a high degree of order without being arranged on a regular lattice (Tilney et al., 1980). Stereocilia actin packing is definitely either hexagonal, as seen in chick cochlea and utricle (Tilney et al., 1983; Shin et al., 2013), or liquid, as seen in mouse inner hair cells (IHCs) and lizard cochlea (DeRosier et al., 1980; Tilney et al., 1980; Mogensen et al., 2007). Open in a separate window Number 1. Actin cross-linkers of mouse vestibular stereocilia. (A) Scanning electron micrograph of P30 mouse utricle hair bundles. Panel full width is definitely 15 m. (B) Website structure of the major stereocilia actin cross-linkers. FSCN2 (fascin 2) offers four -trefoil (T) domains. PLS1 (plastin 1) offers two EF-hands (EF) and four calponin homology (CH) domains. ESPN-1 (the longest espin splice form) offers nine ankyrin repeats (ANK), two proline-rich domains (P1 and P2), a masked actin-binding website (xAB) website, a Wiskott-Aldrich homology 2 (WH2) website, and an actin-binding module (ABM). ESPN-4 (the shortest espin splice form) just offers WH2 and ABM domains. (C) Protein immunoblot showing PLS1 is definitely absent in hair bundles isolated from mice. Molecular mass markers (in kD) are indicated. Because they rely on stereocilia for his or her physiological function, hair cells are ideal for studying structures made of bundled actin filaments. Hair-bundle phenotypes of human being, mouse, and zebrafish mutants are often illuminating; mutations that inactivate hair cell function often do not impact additional cell types, either because specialized paralogs are employed by hair cells or because payment from related molecules can prevent loss of function in additional cell types. In many cases, the morphological effects of mutation of the genes encoding specific actin-binding proteins immediately suggest a function for the protein (Drummond et al., 2012). Here, we examined stereocilia Rabbit Polyclonal to SERPING1 of SR 48692 the mouse vestibular system, which allowed us to combine phenotypic analysis of mice lacking functional versions.