Progressive degeneration of hair bundles in <i>Tur/Tur</i> cochleae.

<p>(A,B) Immunofluorescence of anti-myosin VI on cochlear sections of wild-type (A) and <i>Tur/Tur</i> mutant at P0 (from middle turn). Arrow points to smaller tunnel of Corti in the mutant. (C-D) Phalloidin staining of whole-mount cochlear sensory epithelium (middle turn) from P0 (C,D), P14 (E,F) and P21 (G,H) with phalloidin (red). <i>Myo6</i>^{<i>Tur/Tur</i>} cochleae show irregular shapes of hair bundles compared to wild-type cochleae throughout all regions of the cochlea. Asterisks in H point to degeneration or elongation of stereocilial bundles in the mutant at P21. IHC, inner hair cell; OHC, outer hair cell. Scale bar: 25 μm.</p

The penetrant rate for gross and behavioral abnormalities of <i>Turner</i> mice.

<p>The penetrant rate for gross and behavioral abnormalities of <i>Turner</i> mice.</p

ABR threshold measurements of mice at 4 (unbroken lines) and 10 (broken lines) weeks of age.

<p>(A) Average threshold ± s.e.m. for wild-type (+/+) at 4 weeks (n = 3) and 10 weeks (n = 6), <i>Tur</i> heterozygous <i>(Tur/+)</i> at 10 weeks (n = 8) and homozygous ears (<i>Tur/Tur</i>) at 4 weeks (n = 5) and 10 weeks (n = 6) of age. Averages of 90 dB SPL were used for thresholds beyond the upper limit of the sound system. The <i>Tur/+</i> mice at 10 weeks of age had mild hearing loss in both ears (threshold shifted by 10–20 dB between 16 and 45 kHz), while <i>Tur/+</i> mice at 4 weeks of age (n = 5) had relatively normal hearing. However, all homozygous mice at 4 weeks of age had severe hearing loss (threshold shift by ~20–40 dB), while homozygous mice at 10 weeks of age had >35 dB loss between 5–11 kHz and >50 dB loss between 16–45 kHz.</p

Disorganized vestibular hair bundles in <i>Tur/Tur</i> mutant.

<p>(A-F) Phalloidin staining showing stereocilia in maculae in the utricle and saccule at P14. Hair bundles of <i>Tur/Tur</i> mice are irregular with no pattern of organization. Arrows in F point to elongation of stereocilia in the mutant when compared to that in normal mice (arrows in E). Panel E,F are higher magnification of boxed area in C,D. (G,H) Anti-myosin VI immunostaining on utricle sections. Scale bars: E,F, 13 μm and all other panels, 20 μm.</p

The <i>Turner</i> mutation in myosin VI.

<p>(A) Pattern program output of the results of 11 markers located between 63.3798 Mb and 96.3284 Mb, tested on DNA derived from 11 affected (9 were G3 offspring and 2 were the N2 breeding pair), that showed recombination between three markers (gnf09.071.906, 09.081.324 and rs13480312). The <i>Tur</i> mutation was determined to lie between marker rs6292345 (75.3386 Mb) and rs3698443 (87.1572 Mb). The black box (linked) indicates mice heterozygous for the C3H and the C57; the white box (unlinked) indicates mice homozygous for the C3H (patterns 1 and 2) or the C57 (pattern 4). (B) Sequence analysis of the <i>Turner</i> genomic DNA revealing a 820A>T transversion in exon 8 (NM_001039546). Control DNA shows a single A peak and heterozygous DNA (<i>Tur/+</i>) shows both A and T peaks, but homozygous DNA (<i>Tur/Tur</i>) shows a single T peak. (C) The p. N200I single amino acid substitution. Alignment of a portion of myosin VI protein from various species revealing conservation of the N200 residue. The switch I loop consensus sequence motif within the motor domain is indicated.</p

A variety of structural defects in <i>Tur</i> mutant cochlear hair bundles at P21.

<p>Higher magnifications of SEM images showing stereocilia bundles of outer hair cells in wild-type (A), <i>Tur/Tur</i> (B-E) and <i>Tur/+</i> (F-J) mice. <i>Myo6</i>^{<i>Tur/Tur</i>} cochleae show formation of multiple clumps of stereocilia within the same cell (split bundles) (B-D), stereocilial fusion bundles (arrow, D), folded stereocilia (E) or other abnormal shapes (generally deformed bundles) (C,E). In <i>Myo6</i>^<i>Tur/+</i> cochleae (F-J), the stereocilia also appear to be misshapen in the basal turn and loss of hair cells was occasionally observed (arrow in F). However, hair bundle split or degeneration was not apparent. Scale bars: A, 1 μm; B-E,G-J, 2 μm; F, 3 μm.</p

Degeneration of vestibular hair cells in <i>Tur/Tur</i> mutant.

<p>H&E staining of inner ear tissue at 4 weeks. (A-H) Posterior (A,B) and anterior (C,D) crista ampullaris, utricular macula (E,F) and Organ of Corti (G,H) in wild-type (A,C,E,G) and <i>Tur/Tur</i> mutant (B,D,F,H). Significant reduction of hair cells in the vestibular sensory organs (arrows in B,D,F) and collapse of the organ of Corti (arrow, H) are evident in the inner ear of <i>Tur/Tur</i> mice. Panels G,H are images showing the organ of Corti in the basal turn. Abb.: hc, hair cell; ihc, inner hair cell; ohc, outer hair cell; sc, supporting cell; tc, tunnel of Corti. Scale bar: A-F, 50 μm and G,H, 25 μm.</p

Disorganization and degeneration of hair bundles in <i>Tur/Tur</i> mutant cochleae at P0 and P21.

<p>SEM images showing stereocilial bundles of outer hair cells in the mid-basal turn in wild-type at P0 (A) and P21 (E), <i>Tur/Tur</i> at P0 (B-D) and P21 (F,G). <i>Myo6</i>^{<i>Tur/Tur</i>} cochleae show misshapen stereocilia, which appear to be smaller/narrower when compared to those in wild-type mice at P0. At P21, stereocilial degeneration is apparent in the majority of cells in the mid-basal turn (arrows). Scale bars: A-D, 2 μm; E,F, 3.0 μm; G, 2.5 μm.</p