Myosin VI and VIIa distribution among inner ear epithelia in diverse fishes

Abstract

Unconventional myosins are critical motor proteins in the vertebrate inner ear. Mutations in any one of at least six different myosins can lead to human hereditary deafness, but the precise functions of these proteins in the ear are unknown. This study uses a comparative approach to better understand the role of myosins VI and VIIa in vertebrate ears by examining protein distribution for these two myosins in the ears of evolutionarily diverse fishes and the aquatic clawed toad Xenopus laevis. Both myosins are expressed in the inner ears of all species examined in this study. Myo7a localizes to hair cells, particularly the actin-rich hair bundle, in all species studied. Myo6 also localizes to hair cells, but its distribution differs between species and end organs. Myo6 is found in hair bundles of most fish and frog epithelia examined here but not in anterior and posterior utricular hair bundles of American shad. These results show that myo7a distribution is highly conserved in diverse vertebrates and suggest functional conservation as well. The finding of myo6 in fish and Xenopus hair bundles, however, suggests a novel role for this protein in anamniotic hair cells. The lack of myo6 in specific American shad utricular hair bundles indicates a unique quality of these cells among fishes, perhaps relating to ultrasound detection capability that is found in this species.

Notch Signaling Regulates the Extent of Hair Cell Regeneration in the Zebrafish Lateral Line

“…We also assessed regeneration with the antibody-based HC markers myosin-VI (Hasson and Mooseker, 1994;Hasson et al, 1997;Coffin et al, 2007) and HCS-1 (Gale et al, 2000;LopezSchier and Hudspeth, 2006). Hair cells were concurrently immunostained and counted for both markers.…”

Phenotypic and Expression Analysis of a Novel Spontaneous Myosin VI Null Mutant Mouse

“…5B). The blot was probed with a rabbit polyclonal antibody for MYO6 that had been previously characterised [7,15,16,17]. A ~140-kDa band of MYO6 was abundant in tissues from wild-type mice but was not detectable in those of the rsv mutant.…”

myosin 7aa−/− mutant zebrafish show mild photoreceptor degeneration and reduced electroretinographic responses

“…In both mice and zebrafish, Myo7a is found in the sensory hair cells, specifically at the apical ends of the stereocilia and at the pericuticular necklace that anchors the bases of the stereocilia, both areas rich in F-actin (Hasson et al, 1995). In the mouse retina, Myo7a has been found in the actin-rich microvilli of the apical domain of the RPE cells (Coffin et al, 2007; Hasson et al, 1995) and in the connecting cilia between the inner and outer segments of the photoreceptors (Wolfrum and Schmitt, 2000). More recent evidence indicates that Myo7a localizes to the calyceal processes (Sahly et al, 2012).…”