Our brains are bigger, relative to body size, than other animals’, but it’s not just size that matters. Elephants and whales have bigger brains, so comparing anatomy or even genomes of humans and other animals reveals little about the genetic and developmental changes that sent our brains down such a different path. Geneticists have identified a few key differences in the genes of humans and apes. But specifically how human variants of such genes shape our brain in development—and how they drove its evolution—have remained largely mysterious. Now, researchers are deploying new tools to understand the molecular mechanisms behind the unique features of our brain. At a symposium at The American Society of Human Genetics in Orlando, Florida, last month, they reported zooming in on the genes expressed in a single brain cell, as well as panning out to understand how genes foster connections among far-flung brain regions. Researchers are also experimenting with brain “organoids,” tiny structured blobs of lab-grown tissue, to detail the molecular mechanisms that govern the folding and growth of the embryonic human brain.

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新工具为人类大脑如何形成提供线索

相对于体型而言，我们的大脑比其他动物的大脑更大，但重要的不仅仅是大小。大象和鲸鱼的大脑更大，因此比较人类和其他动物的解剖结构甚至基因组，几乎无法揭示导致我们的大脑走上如此不同道路的遗传和发育变化。遗传学家已经确定了人类和猿类基因的一些关键差异。但具体而言，此类基因的人类变异如何在发育过程中塑造我们的大脑——以及它们如何推动其进化——在很大程度上仍然是个谜。现在，研究人员正在部署新工具来了解我们大脑独特特征背后的分子机制。上个月在佛罗里达州奥兰多举行的美国人类遗传学会研讨会上，他们报告说放大了单个脑细胞中表达的基因，以及了解基因如何促进遥远的大脑区域之间的联系。研究人员还在试验大脑“类器官”，即实验室培养的组织的微小结构斑点，以详细说明控制胚胎人脑折叠和生长的分子机制。