Gene-expression analysis of hair cell regeneration in the zebrafish lateral line

Abstract

Deafness caused by the terminal loss of inner ear hair cells is one of the most common sensory diseases. However, nonmammalian animals (e.g., birds, amphibians, and fish) regenerate damaged hair cells. To understand better the reasons underpinning such disparities in regeneration among vertebrates, we set out to define at high resolution the changes in gene expression associated with the regeneration of hair cells in the zebrafish lateral line. We performed RNA-Seq analyses on regenerating support cells purified by FACS. The resulting expression data were subjected to pathway enrichment analyses, and the differentially expressed genes were validated in vivo via whole-mount in situ hybridizations. We discovered that cell cycle regulators are expressed hours before the activation of Wnt/β-catenin signaling following hair cell death. We propose that Wnt/β-catenin signaling is not involved in regulating the onset of proliferation but governs proliferation at later stages of regeneration. In addition, and in marked contrast to mammals, our data clearly indicate that the Notch pathway is significantly down-regulated shortly after injury, thus uncovering a key difference between the zebrafish and mammalian responses to hair cell injury. Taken together, our findings lay the foundation for identifying differences in signaling pathway regulation that could be exploited as potential therapeutic targets to promote either sensory epithelium or hair cell regeneration in mammals.signaling pathway analysis | RNA sequencing | neuromast | Jak/Stat3 | cdkn1b

Notch inhibition induces mitotically generated hair cells in mammalian cochleae via activating the Wnt pathway

“…Loss of Notch signaling produces ectopic HCs through direct transdifferentiation of SCs during late development and postnatal cochlea (22)(23)(24)(25), yet the role of Notch in cell proliferation under those conditions remains to be determined. A recent study in zebrafish showed that Notch inhibition is accompanied with cell cycle reentry immediately after HC damage in the lateral line neuromasts (44). In this study, we demonstrate that SC proliferation was induced by Notch inhibition in vivo and in vitro.…”

Dynamic gene expression by putative hair-cell progenitors during regeneration in the zebrafish lateral line

“…Finally, they characterized the transcriptional profile of GFPpositive cells by whole-transcriptome sequencing rather than by microarray analysis. A more detailed comparison of the results can be found in the accompanying paper (61).…”

Sensory hair cell development and regeneration: similarities and differences

“…This suggests that FGF signaling inhibits proliferation during regeneration but that blocking FGF signaling alone is not sufficient to enhance proliferation. A decrease in Fgfr3 expression has also been observed after damage in the chicken cochlea and in the zebrafish lateral line (Bermingham-McDonogh et al, 2001;Jiang et al, 2014), whereas Fgfr3 upregulation occurs in the damaged, mammalian cochlea (Pirvola et al, 1995). Whether this difference in FGF receptor expression between mammalian and non-mammalian cochleae accounts for their contrasting proliferative capacities is currently unclear.…”

“…The findings of studies that have probed the dynamics of gene expression during regeneration, such as those in the chicken inner ear organs and the zebrafish lateral line, have already illustrated such multiplex changes during the different phases of regeneration (Alvarado et al, 2011;Hawkins et al, 2007;Jiang et al, 2014;Ku et al, 2014;Steiner et al, 2014). As we gain knowledge about the transcriptome of the nonregenerating mammalian cochlea, we can begin to dissect its gene expression patterns and contrast them with those seen in regenerating sensory organs.…”