SUMMARY The scarcity of tissue-specific stem cells and the complexity of their surrounding environment have made molecular characterization of these cells particularly challenging. Through single-cell transcriptome and weighted gene co-expression network analysis (WGCNA), we uncovered molecular properties of CD133+/GFAP− ependymal (E) cells in the adult mouse forebrain neurogenic zone. Surprisingly, prominent hub genes of the gene network unique to ependymal CD133+/GFAP− quiescent cells were enriched for immune-responsive genes, as well as genes encoding receptors for angiogenic factors. Administration of vascular endothelial growth factor (VEGF) activated CD133+ ependymal neural stem cells (NSCs), lining not only the lateral but also the fourth ventricles and, together with basic fibroblast growth factor (bFGF), elicited subsequent neural lineage differentiation and migration. This study revealed the existence of dormant ependymal NSCs throughout the ventricular surface of the CNS, as well as signals abundant after injury for their activation.

Summary Recent advances in gene editing technology have introduced the potential for application of mutagenesis approaches in non-human primates to model human development and disease. Here we report successful TALEN-mediated mutagenesis of an X-linked, Rett Syndrome (RTT) gene, the methyl-CpG binding protein 2 (MECP2), in both rhesus and cynomolgus monkeys. Microinjection of MECP2-targeting TALEN plasmids into rhesus and cynomolgus zygotes leads to effective gene editing of MECP2 with no detected off-target mutagenesis. Male rhesus (2) and cynomolgous (1) fetuses carrying MECP2 mutations in various tissues including testes were miscarried during mid-gestation, consistent with RTT-linked male embryonic lethality in humans. One live delivery of a female cynomolgus monkey occurred after 162 days of gestation, with abundant MECP2 mutations in peripheral tissues. We conclude that TALEN-mediated mutagenesis can be an effective tool for genetic modeling of human disease in non-human primates.

Summary Gene-editing technologies have made it feasible to create nonhuman primate models for human genetic disorders. Here, we report detailed genotypes and phenotypes of TALEN-edited MECP2 mutant cynomolgus monkeys serving as a model for a neurodevelopmental disorder, Rett syndrome (RTT), which is caused by loss-of-function mutations in the human MECP2 gene. Male mutant monkeys were embryonic lethal, reiterating that RTT is a disease of females. Through a battery of behavioral analyses, including primate-unique eye-tracking tests, in combination with brain imaging via MRI, we found a series of physiological, behavioral, and structural abnormalities resembling clinical manifestations of RTT. Moreover, blood transcriptome profiling revealed that mutant monkeys resembled RTT patients in immune gene dysregulation. Taken together, the stark similarity in phenotype and/or endophenotype between monkeys and patients suggested that gene-edited RTT founder monkeys would be of value for disease mechanistic studies as well as development of potential therapeutic interventions for RTT.