microRNA EXPRESSION IN THE LATE EMBRYONIC PAX6-NULL MOUSE CEREBELLUM

Classically, Pax6 is a gene critical for eye development, but more recently it has been shown to be important for the development of several organ systems including the cerebellum. In the Pax6 mutant cerebellum there are developmental alterations specific to the glutamatergic neurons. This study investigates the regulatory role of microRNAs (miRNAs), small non-coding RNAs, on mRNAs in wildtype and Pax6-null cerebellar development at embryonic day (E) 18.5. RNAs were extracted and sequenced, establishing the expression profile of both miRNAs and mRNAs. A total of 491 known miRNAs and 262 putative, novel miRNAs met the expression criteria defined for our cerebellar samples. Using bioinformatic tools, 20 significantly differentially expressed (DE) known miRNAs and 60 DE mRNAs were identified between wildtype and Pax6-null tissue. The DE miRNAs identified had high expression correlation with 208 unique mRNA targets in our samples. These target mRNAs and the DE mRNAs were significantly enriched for functions in brain development, particularly relevant to synaptogenesis. Overall, our study adds to the growing body of literature on the functional and mechanistic roles of miRNAs in brain development, from the perspective of key regulatory networks controlled by Pax6.

长期以来，Pax6均被视为调控眼睛发育的核心基因，但近年研究证实，其在包括小脑（cerebellum）在内的多个器官系统的发育过程中同样发挥关键作用。在Pax6突变的小脑中，谷氨酸能神经元（glutamatergic neurons）会出现特异性的发育异常。本研究针对胚胎发育第18.5天（E18.5）的野生型（wildtype）与Pax6缺失型（Pax6-null）小脑发育过程，探究微小RNA（microRNAs, miRNAs，一类小型非编码RNA（small non-coding RNAs））对信使RNA（messenger RNAs, mRNAs）的调控作用。研究人员对样本中的RNA进行提取与测序，成功构建出miRNAs与mRNAs的完整表达谱。经筛选，共计491种已知miRNAs与262种潜在新型miRNAs满足本次小脑样本设定的表达筛选标准。借助生物信息学工具（bioinformatic tools），本研究在野生型与Pax6缺失型脑组织样本中，鉴定得到20种显著差异表达（differentially expressed, DE）的已知miRNAs以及60种差异表达mRNA。进一步分析显示，本次鉴定出的差异表达miRNAs，与样本内208种独特的mRNA靶标存在显著的表达相关性。上述靶标mRNA与差异表达mRNA均显著富集于脑发育相关的功能通路，尤其与突触发生（synaptogenesis）密切相关。综上，本研究从Pax6调控的关键信号网络视角出发，为阐明miRNAs在脑发育中的功能与机制的现有研究体系补充了新的实验证据。