Adult differentiated cells can be reprogrammed into pluripotent stem cells or lineage-restricted proliferating precursors in culture; however, this has not been demonstrated in vivo. Here, we show that the single transcription factor SOX2 is sufficient to reprogram resident astrocytes into proliferative neuroblasts in the adult mouse brain. These induced adult neuroblasts (iANBs) persist for months and can be generated even in aged brains. When supplied with BDNF and noggin or when the mice are treated with a histone deacetylase inhibitor, iANBs develop into electrophysiologically mature neurons, which functionally integrate into the local neural network. Our results demonstrate that adult astrocytes exhibit remarkable plasticity in vivo, a feature that might have important implications in regeneration of the central nervous system using endogenous patient-specific glial cells.

SummaryGlial cells can be in vivo reprogrammed into functional neurons in the adult CNS; however, the process by which this reprogramming occurs is unclear. Here, we show that a distinct cellular sequence is involved in SOX2-driven in situ conversion of adult astrocytes to neurons. This includes ASCL1+ neural progenitors and DCX+ adult neuroblasts (iANBs) as intermediates. Importantly, ASCL1 is required, but not sufficient, for the robust generation of iANBs in the adult striatum. These progenitor-derived iANBs predominantly give rise to calretinin+ interneurons when supplied with neurotrophic factors or the small-molecule valproic acid. Patch-clamp recordings from the induced neurons reveal subtype heterogeneity, though all are functionally mature, fire repetitive action potentials, and receive synaptic inputs. Together, these results show that SOX2-mediated in vivo reprogramming of astrocytes to neurons passes through proliferative intermediate progenitors, which may be exploited for regenerative medicine.

SummaryPro-neural transcription factors and small molecules can induce the reprogramming of fibroblasts into functional neurons; however, the immediate-early molecular events that catalyze this conversion have not been well defined. We previously demonstrated that neurogenin 2 (NEUROG2), forskolin (F), and dorsomorphin (D) can reprogram fibroblasts into functional neurons with high efficiency. Here, we used this model to define the genetic and epigenetic events that initiate an acquisition of neuronal identity. We demonstrate that NEUROG2 is a pioneer factor, FD enhances chromatin accessibility and H3K27 acetylation, and synergistic transcription activated by these factors is essential to successful reprogramming. CREB1 promotes neuron survival and acts with NEUROG2 to upregulate SOX4, which co-activates NEUROD1 and NEUROD4. In addition, SOX4 targets SWI/SNF subunits and SOX4 knockdown results in extensive loss of open chromatin and abolishes reprogramming. Applying these insights, adult human glioblastoma cell and skin fibroblast reprogramming can be improved using SOX4 or chromatin-modifying chemicals.

Objective To determine the factors associated with intra- and postoperative cerebrospinal fluid (CSF) leaks in setting of endoscopic transsphenoidal sellar surgery. Study Design Retrospective cohort. Setting Tertiary referral center. Subjects and Methods This study included 806 patients who underwent endoscopic transsphenoidal sellar surgery between 2004 and 2016. The associations between CSF leaks (intra- and postoperative) and patient demographics, medical history, tumor characteristics, and intraoperative repair techniques were analyzed. Results In sum, 205 (25.4%) patients had a CSF leak: 188 (23.3%) intraoperative leaks and 38 (4.7%) postoperative leaks. Twenty-one (2.6%) patients had postoperative leaks after having repair of an intraoperative leak; 55% of patients with a postoperative leak had an intraoperative leak repaired. On multivariate analysis, body mass index (BMI), hydrocephalus, suprasellar extension, and craniopharyngioma significantly predicted intraoperative CSF leaks, while only BMI and hydrocephalus predicted postoperative CSF leaks. Patients having septal flap repairs of CSF leaks had a higher postoperative leak rate relative to other repair techniques (odds ratio, 6.37; P = .013). Rigid reconstruction did not correlate with leaks. Conclusion For this large cohort of patients undergoing endoscopic transsphenoidal sellar surgery, BMI and hydrocephalus were identified as predictors of postoperative CSF leaks, including those occurring after repair of intraoperative leak. These variables may put stress on the surgical repair of sellar defects, and consideration of these risk factors may help counsel patients and guide perioperative decision making in regard to repair strategies and CSF diversion techniques.

Injury to the adult brain induces activation of local astrocytes, which serves as a compensatory response that modulates tissue damage and recovery. However, the mechanism governing astrocyte activation during brain injury remains largely unknown. Here we provide in vivo evidence that SOX2, a transcription factor critical for stem cells and brain development, is also required for injury-induced activation of adult cortical astrocytes. Genome-wide chromatin immunoprecipitation-seq analysis of mouse cortical tissues reveals that SOX2 binds to regulatory regions of genes associated with signaling pathways that control glial cell activation, such as Nr2e1, Mmd2, Wnt7a, and Akt2. Astrocyte-specific deletion of Sox2 in adult mice greatly diminishes glial response to controlled cortical impact injury and, most unexpectedly, dampens injury-induced cortical loss and benefits behavioral recovery of mice after injury. Together, these results uncover an essential role of SOX2 in somatic cells under pathological conditions and indicate that SOX2-dependent astrocyte activation could be targeted for functional recovery after traumatic brain injury.