Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
Department of Psychiatry, Neuroscience Program, UCSF Weill Institute for Neurosciences and the Nina Ireland Laboratory of Developmental Neurobiology, University of California San Francisco, San Francisco, CA 94158, USA.
Cell. 2018 Jan 25;172(3):491-499.e15. doi: 10.1016/j.cell.2017.12.017. Epub 2018 Jan 18.
Non-coding "ultraconserved" regions containing hundreds of consecutive bases of perfect sequence conservation across mammalian genomes can function as distant-acting enhancers. However, initial deletion studies in mice revealed that loss of such extraordinarily constrained sequences had no immediate impact on viability. Here, we show that ultraconserved enhancers are required for normal development. Focusing on some of the longest ultraconserved sites genome wide, located near the essential neuronal transcription factor Arx, we used genome editing to create an expanded series of knockout mice lacking individual or combinations of ultraconserved enhancers. Mice with single or pairwise deletions of ultraconserved enhancers were viable and fertile but in nearly all cases showed neurological or growth abnormalities, including substantial alterations of neuron populations and structural brain defects. Our results demonstrate the functional importance of ultraconserved enhancers and indicate that remarkably strong sequence conservation likely results from fitness deficits that appear subtle in a laboratory setting.
非编码的“超保守”区域包含数百个连续的碱基，在哺乳动物基因组中具有完美的序列保守性，可以作为远距离作用的增强子。然而，最初在小鼠中的缺失研究表明，失去这些极其受限的序列对生存力没有直接影响。在这里，我们表明超保守增强子是正常发育所必需的。我们专注于基因组上一些最长的超保守位点，位于关键神经元转录因子 Arx 附近，使用基因组编辑技术创建了一系列扩展的敲除小鼠，这些小鼠缺失了单个或多个超保守增强子。具有单个或成对缺失超保守增强子的小鼠具有活力和生育能力，但几乎在所有情况下都表现出神经或生长异常，包括神经元群体的大量改变和结构脑缺陷。我们的结果证明了超保守增强子的功能重要性，并表明非常强的序列保守性可能是由于在实验室环境中表现出细微的适应性缺陷所致。
