Regeneration in zebrafish lateral line neuromasts: Expression of the neural progenitor cell marker sox2 and proliferation‐dependent and‐independent mechanisms of hair cell renewal

Abstract

Mechanosensory hair cells are essential for audition in vertebrates, and in many species, have the capacity for regeneration when damaged. Regeneration is robust in the fish lateral line system as new hair cells can reappear after damage induced by waterborne aminoglycoside antibiotics, platinum-based drugs, and heavy metals. Here, we characterize the loss and reappearance of lateral line hair cells induced in zebrafish larvae treated with copper sulfate using diverse molecular markers. Transgenic fish that express green fluorescent protein in different cell types in the lateral line system have allowed us to follow the regeneration of hair cells after different damage protocols. We show that conditions that damage only differentiated hair cells lead to reappearance of new hair cells within 24 h from nondividing precursors, whereas harsher conditions are followed by a longer recovery period that is accompanied by extensive cell division. In order to characterize the cell population that gives rise to new hair cells, we describe the expression of a neural stem cell marker in neuromasts. The zebrafish sox2 gene is strongly expressed in neuromast progenitor cells, including those of the migrating lateral line primordium, the accessory cells that underlie the hair cells in neuromasts, and in interneuromastic cells that give rise to new neuromasts. Moreover, we find that most of the cells that proliferate within the neuromast during regeneration express this marker. Thus, our results describe the dynamics of hair cell regeneration in zebrafish and suggest the existence of at least two mechanisms for recovery of these cells in neuromasts.

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

“…1G and Fig. S1) (40). Counts of Sox2 + FACS-purified cells revealed that 95% of GFP + cells but only 6.6% of GFP − cells were positive for Sox2 (Fig.…”

Notch Signaling Regulates the Extent of Hair Cell Regeneration in the Zebrafish Lateral Line

“…Neuromasts exposed to copper showed both mitotic and nonmitotic regeneration depending on the severity of damage (Hernandez et al, 2007). Exposure of 3 dpf larvae to 1 M CuSO 4 resulted in mostly nonmitotic renewal, although treatment with a higher concentration (10 M) resulted in mostly proliferative replacement (Hernandez et al, 2007).…”

“…Exposure of 3 dpf larvae to 1 M CuSO 4 resulted in mostly nonmitotic renewal, although treatment with a higher concentration (10 M) resulted in mostly proliferative replacement (Hernandez et al, 2007). There are several possibilities to explain the differences in the level of nonmitotic regeneration after low-dose copper compared with that seen after high copper or with neomycin treatment.…”

“…Similarly, they are hypersensitive to damage from ototoxic drugs such as aminoglycosides and antineoplastic drugs (Song et al, 1995;Williams and Holder, 2000;Harris et al, 2003;Murakami et al, 2003;Ton and Parng, 2005;Santos et al, 2006;Ou et al, 2007;Owens et al, 2007) as well as agents such as copper (Hernandez et al, 2006(Hernandez et al, , 2007Linbo et al, 2006). Regeneration of lateral line HCs have been studied after laser ablation in axolotls (Balak et al, 1990;Jones and Corwin, 1996) and aminoglycoside or copper treatments in fish (Song et al, 1995;Williams and Holder, 2000;Harris et al, 2003;Lopez-Schier and Hudspeth, 2006;Hernandez et al, 2007).…”

The transmembrane inner ear (Tmie) protein is essential for normal hearing and balance in the zebrafish

“…Live 5-dpf WT and mutant Et(krt4:GFP) sqet4 larvae were immersed in 5 M CuSO4 in E3 medium (18) for 1 h at 28.5°C and then rinsed twice briefly in E3 medium. After confirming essentially complete hair-cell death in the lateral line by fluorescence microscopy, we allowed treated animals to recover in E3 medium at 28.5°C.…”