Eya1-Six1信号在斑马鱼侧线神经丘毛细胞再生过程中的表达

机械感觉毛细胞对于脊椎动物的听力和平衡能力至关重要，低等脊椎动物毛细胞在遭受损伤后具有很强的再生能力。鱼类侧线神经丘毛细胞与内耳毛细胞具有相似的结构、功能、发育和再生过程。我们将受精后5~6 d的斑马鱼仔鱼置于400 μmol/L新霉素溶液中处理1 h破坏神经丘毛细胞。分别对处理后2、4、8、12及24 h的斑马鱼仔鱼进行组织学切片及功能基因eya1和six1b的整体原位杂交。组织学切片结果显示：对照组神经丘毛细胞与支持细胞形态及排布都很规则，毛细胞和支持细胞分别位于上层和下层；处理后2~4 h，上层毛细胞数量显著下降；处理后8~12 h，支持细胞和毛细胞之间界限模糊，部分支持细胞变长，且与基膜脱离；处理后24 h，部分神经丘内毛细胞及支持细胞数量、形态及排布接近对照组水平。整体原位杂交结果显示：eya1和six1b在对照组斑马鱼仔鱼整个神经丘都有表达；处理后4 h内神经丘中央毛细胞中eya1和six1b的表达量显著下降，周围的支持细胞中仍保持一定量的表达；这两个基因的表达量从处理后8 h起逐渐提高，在处理后12~24 h恢复甚至超过对照组。综上结果表明：神经丘毛细胞再生过程中可能有支持细胞的参与，且重启了神经丘毛细胞发育过程中的功能基因eya1和six1b。

The expression of Eya1 Six1 signaling in the regeneration of hair cell in zebrafish lateral line neuromasts

Mechanoreceptive hair cells are essential for hearing and balance in vertebrates. They have an ability of spontaneous regeneration after damage in lower vertebrate but not in mammals. The lateral line hair cells in fish share structural, functional, developmental and regenerative similarities with those in the inner ear. In order to understand the mechanism of hair cell regeneration and the role of key functional genes,eya1andsix1bduring this process, zebrafish lateral line neuromast hair cells were taken as the study subject in this report. We destroyed neuromast hair cells by treating zebrafish larvae of 5 days postfertilization in 400 μmol/L neomycin for 1 hour. Both the control and treatment groups were observed at 2, 4, 8, 12 and 24 hours post treatment （hpt） via methods of histological sections and in situ hybridization （ISH）. It was found that, in control group, hair cells and supporting cells with regular shape were distributed ordinarily in top and lower respectively as two layers; however, the number of the cell in the top layer was significantly decreased during 2-4 hpt. During 8-12 hpt, the boundary between the top and lower layer was indistinct, and some supporting cells were elongated and separated from basement membrane. By 24 hpt, the number, shape, distribution of hair cells and supporting cells in some neuromasts were nearly recovered to the level of control samples. ISH results showed that both eya1andsix1b were expressed in the whole neuromast of the zebrafish larvae in control group. The expression levels of eya1andsix1b in hair cells, but not supporting cells, were significantly reduced during 2-4 hpt. The levels started increasing at 8 hpt, and gradually reached full recovery or even exceeded the level in the control group during 12-24 hpt. Our results indicate that, both the key functional genes eya1andsix1b are reactivated during the hair cell regeneration process in zebrafish lateral line neuromasts and the supporting cells may be involved in hair cell regeneration.