中国科学院昆明动物研究所机构知识库

动物的大脑发育涉及一系列的机制，包括从模块化分区、前体细胞增殖与分 化、到神经元的迁移。其中，与神经前体细胞的增殖与分化相关的一系列分子调 控机制尤其重要，因为它们可以调控脑容量的大小，对动物脑容量的进化可能具 有重要作用。前人的研究表明，多个导致人类常染色体隐性原发性小头症的致病 基因在灵长类的进化过程由于达尔文正选择都发生了快速的进化。其中， MCPH1 基因的快速进化是一个典型的例子。在人类的起源过程中 MCPH1 发生 了多个位点的人类特异突变, 可能对人类大脑容量和结构的进化具有重要贡献。 本论文利用CRISPR/Cas9基因编辑技术成功将小鼠MCPH1的两个位点替换为人 类特异突变的序列，建立了 MCPH1 基因人源化小鼠模型。我们对新生、出生后 35 天及出生后 70 天的小鼠（包括人源化小鼠和野生型对照小鼠）进行了脑发育 跟踪采样，收集了体重、脑重和大脑皮层厚度的数据；同时，采用 RNAseq 技术， 我们对新生幼鼠大脑和小脑组织进行了转录组测序。初步的研究结果显示，虽然 野生型和人源化小鼠之间在体重、脑重和大脑皮层厚度上存在统计学上的显著差 异，但这种差异仅体现在个别发育时期。脑组织转录组的表达差异分析表明，野 生型和人源化小鼠的基因表达具有差异，但差异的幅度不大，说明两个位点的人 源化替换对小鼠大脑发育的影响有限。

The development of the mammalian cerebral cortex involves a series of mechanisms: from patterning, progenitor cell proliferation and differentiation, to neuronal migration. Of these, the mechanisms that influence the proliferation and differentiation of neural progenitor cells are of particular interest, as they may have the greatest consequence on brain size, not only during development but also in evolution. Among the genes causing human autosomal recessive primary microcephaly, MCPH1 is a typical case of showing positive selection during primate evolution. In particular, during the origin of humans, MCPH1 has accumulated many human-specific amino acid changes, which may contribute to the large volume and sophiscated cognitive skills of humans during evolution. In this study, we successfully established the humanized mouse model of two specific loci of MCPH1 gene by CRISPR / Cas9 gene editing technique. Then we sampled newborn, 35-day-old and 70-day-old mice, collecting data on body weight, brain weight and cortical radial thickness. We also performed transcriptome analysis of cerebrum and cerebellum of newborn mice using RNAseq. The preliminary results showed that there were statistically significant differences in body weight, brain weight, and cortical radial thickness between the wild type and the humanized mice though these differerences only occurred in certain developmental stages. We identified differentially expressed genes between the wild type and the humanized mice in both cerebrum and cerebellum though the fold changes were small, implying that the effect of the two-loci subsitutions have relatively limited influence on mouse brain development.