Phenotype Image Detail

Image

Caption

Actin filaments and cuticular plate in inner hair cells (IHCs) from Eps8l2^tm1Wma/Eps8l2^tm1Wma (Eps8L2-KO) mice. (A) TEM showing a horizontal section from an IHC hair bundle of a mutant mouse at P240. Note that the hair bundle is disorganized, making row structure hard to define. Gaps without stereocilia, especially in the tall (t) row, are present. Very thin stereocilia are apparent in the intermediate (i) stereociliary row. (Scale bar, 2 um.) (B) SEM image of part of an IHC bundle to show presumptive equivalent stereocilia to those illustrated in C-E. (Scale bar, 0.4 um.) (C-E) Stereocilia of varying thickness observed in mutants. They all contain a similar density of actin filaments, indicating that changes in packing do not explain the extreme variations in thickness. (Scale bar for C-E, 0.2 um.) (F-J) TEM images showing radial sections from P240 apical coil IHCs and outer hair cells (OHCs). (F) Normal structure of the apical end of an IHC from a control mouse. The cuticular plate (arrowheads) is relatively thin but normal in structure. (G) IHC from the mutant showing a partially fragmented cuticular plate; a split at the point is indicated by the arrow. (Scale bars for F and G, 1 um.) (H) IHC from the mutant showing a region (*) where the cuticular plate is absent. In addition, two stereociliary cores can be seen withdrawn into the apical cytoplasm (bottom right) and the remaining visible tall stereocilium appears to have three rootlet structures in its core where more commonly there is only one or two. (Scale bar, 0.5 um.) (I and J) Control and mutant OHCs, respectively. The depth of the cuticular plate, measured approximately along the double arrow line shown, was found to be significantly thicker (P < 0.05) in control (1.00 0.04 um, n = 6) than in mutant (0.76 0.09 um, n = 5) OHCs. (Scale bars, 2 um.) These data suggest a reduced ability to maintain the cuticular plate in both IHCs and OHCs in the mutants compared with the controls. The morphological defects, together with the presence of immunolabeling for Eps8L2 in the cuticular plate, suggest that Eps8L2 is also involved in the maintenance of normal actin networks at this location.

Copyright

This image is fromFurness DN, Proc Natl Acad Sci U S A 2013 Aug 20;110(34):13898-903. Copyright2013 National Academy of Sciences, U.S.A. J:200669

Associated Alleles

Symbol	Name
Eps8l2^tm1Wma	EPS8-like 2; targeted mutation 1, Walter Marcotti

Associated Genotypes

Allelic Composition	Genetic Background
Eps8l2^tm1Wma/Eps8l2^tm1Wma	B6.129P2-Eps8l2^tm1Wma