Temporal profiling of gene expression in cochleae of wild type and alpha9 null mice

Efferent inhibition of cochlear outer hair cells is mediated by nicotinic cholinergic receptors containing alpha9 (a9) and alpha10 subunits. Mice lacking a9 nicotinic subunits fail to exhibit classic olivocochlear responses and are characterized by abnormal synaptic morphology at the base of outer hair cells. To detail molecular changes induced upon the loss of a9 subunit, we sampled cochlear RNA from wild type and a9 null mice at postnatal (P) days spanning periods of synapse formation and maturation (P3, P7, P13 and P60). Our findings point to a delay in cochlear maturation starting at the onset of hearing (P13), as well as an up-regulation of various GABA receptor subunits in adult mice lacking the a9 nicotinic subunit. Cochleae were removed at postnatal ages P3, P7, P13 and P60. Cochlear tissues from 3-5 mice were pooled per replicate; biological triplicates were performed for each age and genotype.耳蜗外毛细胞的传出抑制由携带α9（a9）与α10亚基的烟碱型胆碱能受体介导。缺失α9烟碱亚基的小鼠无法表现出经典的橄榄耳蜗束反应，且外毛细胞底部呈现异常的突触形态。为详细解析α9亚基缺失所诱导的分子变化，我们于突触形成与成熟的不同阶段（出生后第3、7、13及60天，即P3、P7、P13和P60），从野生型与α9基因敲除小鼠中采集耳蜗RNA样本。研究结果表明，自听力启动的P13阶段起，耳蜗成熟进程出现延迟；同时在缺失α9烟碱亚基的成年小鼠体内，多种γ-氨基丁酸（GABA）受体亚基的表达出现上调。我们于出生后P3、P7、P13及P60四个时间点采集耳蜗组织。每个生物学重复混合3~5只小鼠的耳蜗组织；针对每个年龄与基因型组别，均设置三次生物学重复。