Absence of plastin 1 causes abnormal maintenance of hair cell stereocilia and a moderate form of hearing loss in mice.
Bottom Line: Several actin-associated proteins are essential for stereocilia formation and maintenance, and their absence leads to deafness.Auditory hair cells developed normally in Pls1 KO, but in young adult animals, the stereocilia of inner hair cells were reduced in width and length.These results show that in contrast to other actin-bundling proteins such as espin, harmonin or Eps8, plastin 1 is dispensable for the initial formation of stereocilia.
Affiliation: Centre for Auditory Research, UCL Ear Institute, University College London, London, UK.Show MeSH
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Mentions: To determine whether the absence of plastin 1 might affect the structural organization of the parallel actin bundles within stereocilia, high-resolution images of thin sections of IHCs stereocilia from adult het and Pls1 KO mice were collected (Fig. 6A and B). The mean distance between actin filaments was measured (Fig. 6C) at two different levels of stereocilia: the top region (within 300 nm of the tip) and the shaft region located more basally. At the level of the shaft, there was no significant difference in the packing density of actin filaments in abnormal-looking stereocilia of Pls1 KO (mean = 8.628 nm, SD = 2.36; n = 250 measurements) compared with het (mean = 8.644 nm, SD = 2.154; n = 250) samples. This suggests that the reduction in width of IHC stereocilia is primarily due to a reduction in the number of actin filaments they contain and not to drastic changes in their packing. In the top region, however, the interfilament distance was slightly but significantly (P < 0.05) increased in Pls1 KO (mean = 9.638 nm, SD = 1.851; n = 250, five stereocilia) compared with het (mean = 9.134 nm, SD = 2.049; n = 250, five stereocilia) samples, suggesting that plastin 1 may have a particular importance for F-actin crosslinking at this site, where the plus end of actin filaments is located.Figure 6.
Affiliation: Centre for Auditory Research, UCL Ear Institute, University College London, London, UK.