Sox2 haploinsufficiency primes regeneration and Wnt responsiveness in the mouse cochlea
Patrick J. Atkinson, … , Tomokatsu Udagawa, Alan G. Cheng
Patrick J. Atkinson, … , Tomokatsu Udagawa, Alan G. Cheng
Published March 19, 2018
Citation Information: J Clin Invest. 2018;128(4):1641-1656. https://doi.org/10.1172/JCI97248.
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Sox2 haploinsufficiency primes regeneration and Wnt responsiveness in the mouse cochlea

Abstract

During development, Sox2 is indispensable for cell division and differentiation, yet its roles in regenerating tissues are less clear. Here, we used combinations of transgenic mouse models to reveal that Sox2 haploinsufficiency (Sox2haplo) increases rather than impairs cochlear regeneration in vivo. Sox2haplo cochleae had delayed terminal mitosis and ectopic sensory cells, yet normal auditory function. Sox2haplo amplified and expanded domains of damage-induced Atoh1+ transitional cell formation in neonatal cochlea. Wnt activation via β-catenin stabilization (β-cateninGOF) alone failed to induce proliferation or transitional cell formation. By contrast, β-cateninGOF caused proliferation when either Sox2haplo or damage was present, and transitional cell formation when both were present in neonatal, but not mature, cochlea. Mechanistically, Sox2haplo or damaged neonatal cochleae showed lower levels of Sox2 and Hes5, but not of Wnt target genes. Together, our study unveils an interplay between Sox2 and damage in directing tissue regeneration and Wnt responsiveness and thus provides a foundation for potential combinatorial therapies aimed at stimulating mammalian cochlear regeneration to reverse hearing loss in humans.

Authors

Patrick J. Atkinson, Yaodong Dong, Shuping Gu, Wenwen Liu, Elvis Huarcaya Najarro, Tomokatsu Udagawa, Alan G. Cheng

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Figure 6

Sox2 haploinsufficiency acts as a permissive signal for β-catenin–induced proliferation in the undamaged neonatal cochlea.

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Sox2 haploinsufficiency acts as a permissive signal for β-catenin–induce...
(A) Schematic of the experimental paradigm. Fgfr3-iCre Ctnnb1fl(ex3)/+ and Sox2CreERT2/+ Ctnnb1fl(ex3)/+ pups were given tamoxifen on P2, followed by daily administration of EdU (P3–P5), and cochleae were examined on P5. (B) No EdU+ cells were detected in the organ of Corti in cochleae from Fgfr3-iCre Ctnnb1fl(ex3)/+ mice treated with tamoxifen on P2. (C) EdU+ supporting cells but not hair cells arranged as foci (dashed lines, arrowhead) were found in P5 Sox2CreERT2/+ Ctnnb1fl(ex3)/+ cochleae. (D) Fgfr3-iCre Ctnnb1fl(ex3)/+ and Fgfr3-iCre Sox2fl/+ Ctnnb1fl(ex3)/+ pups were given tamoxifen on P1, followed by EdU administration daily (P3–P5), and cochleae were examined on P5. (E) The apical turn of Fgfr3-iCre Ctnnb1fl(ex3)/+ cochleae revealed no EdU+ hair cells or supporting cells. (F) Like Sox2CreERT2/+ Ctnnb1fl(ex3)/+ cochlea, but in contrast to Fgfr3-iCre Ctnnb1fl(ex3)/+ cochlea, EdU+ cells arranged as clusters (dashed lines, arrowheads) were found in Fgfr3-iCre Ctnnb1fl(ex3)/+ Sox2fl/+ cochlea (tamoxifen was given on P1). (G) Quantification of EdU+ cells. The differences in EdU+ cells between Sox2haplo and conditional Sox2haplo models can be attributed to the timing or degrees of Sox2 partial deletion. (H) Fgfr3-iCre Ctnnb1fl(ex3)/+, Sox2CreERT2/+ Ctnnb1fl(ex3)/+, and Fgfr3-iCre Sox2fl/+ Ctnnb1fl(ex3)/+ pups were injected with tamoxifen on P1, and cochleae were harvested on P4. (I) Gfi1-labeled hair cells were present, but no Atoh1- or Gfi1-labeled Sox2+ supporting cells were detected in Fgfr3-iCre Ctnnb1fl(ex3)/+ cochlea. (J) No Atoh1- or Gfi1-labeled Sox2+ supporting cells were detected in Sox2CreERT2/+ Ctnnb1fl(ex3)/+ cochlea, although foci-like clusters were still noted in the pillar cell region (dashed lines, arrowheads). (K) Neither Atoh1- nor Gfi1-labeled transitional cells were detected in Fgfr3-iCre Ctnnb1fl(ex3)/+ Sox2fl/+ cochlea (tamoxifen was administered on P1), although foci-like clusters could still be observed (dashed line, arrowhead). Data represent the mean ± SD. *P < 0.05 and ***P < 0.001, by 1-way ANOVA with Holm-Sidak multiple comparisons test. n = 3. Scale bars: 20 μm.