We present evidence for a specific role of p53 in the mitochondria-associated cellular dysfunction and behavioral abnormalities of Huntington's disease (HD). Mutant huntingtin (mHtt) with expanded polyglutamine (polyQ) binds to p53 and upregulates levels of nuclear p53 as well as p53 transcriptional activity in neuronal cultures. The augmentation is specific, as it occurs with mHtt but not mutant ataxin-1 with expanded polyQ. p53 levels are also increased in the brains of mHtt transgenic (mHtt-Tg) mice and HD patients. Perturbation of p53 by pifithrin-alpha, RNA interference, or genetic deletion prevents mitochondrial membrane depolarization and cytotoxicity in HD cells, as well as the decreased respiratory complex IV activity of mHtt-Tg mice. Genetic deletion of p53 suppresses neurodegeneration in mHtt-Tg flies and neurobehavioral abnormalities of mHtt-Tg mice. Our findings suggest that p53 links nuclear and mitochondrial pathologies characteristic of HD.

SUMMARY Comparative analyses have identified genomic regions potentially involved in human evolution, but do not directly assess function. Human accelerated regions (HARs) represent conserved genomic loci with elevated divergence in humans. If some HARs regulate human-specific social and behavioral traits, then mutations would likely impact cognitive and social disorders. Strikingly, rare biallelic point mutations–identified by whole genome and targeted “HAR-ome” sequencing–showed a significant excess in individuals with ASD whose parents share common ancestry compared to familial controls, suggesting a contribution in 5% of consanguineous ASD cases. Using chromatin interaction sequencing, massively parallel reporter assays (MPRA), and transgenic mice, we identified disease-linked, biallelic HAR mutations in active enhancers for CUX1, PTBP2, GPC4, CDKL5, and other genes implicated in neural function, ASD, or both. Our data provide genetic evidence that specific HARs are essential for normal development, consistent with suggestions that their evolutionary changes may have altered social and/or cognitive behavior.

Besides its role in glycolysis, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) initiates a cell death cascade 1-9 . Diverse apoptotic stimuli activate inducible nitric oxide synthase (iNOS) or neuronal NOS (nNOS), with the generated nitric oxide (NO) S-nitrosylating GAPDH, abolishing its catalytic activity and conferring on it the ability to bind to Siah1, an E3-ubiquitin-ligase with a nuclear localization signal (NLS). The GAPDH-Siah1 protein complex, in turn, translocates to the nucleus and mediates cell death; these processes are blocked by procedures that interfere with GAPDH-Siah1 binding. Nuclear events induced by GAPDH to kill cells have been obscure. Here we show that nuclear GAPDH is acetylated at Lys 160 by the acetyltransferase p300/CREB binding protein (CBP) through direct protein interaction, which in turn stimulates the acetylation and catalytic activity of p300/CBP. Consequently, downstream targets of p300/CBP, such as p53 (refs 10 -15 ), are activated and cause cell death. A dominant-negative mutant GAPDH with the substitution of Lys 160 to Arg (GAPDH-K160R) prevents activation of p300/CBP, blocks induction of apoptotic genes and decreases cell death. Our findings reveal a pathway in which NO-induced nuclear GAPDH mediates cell death through p300/CBP.10Correspondence and requests for materials should be addressed A.S. or S.H.S (E-mail: asawa1@jhmi.edu; E-mail: ssnyder@jhmi.edu). 8 Current address: Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA. 9 These authors contributed equally to this work. AUTHOR CONTRIBUTIONS Ni.S. and M.R.H. were primarily responsible for experimental design and work, data analysis and preparation of figures, and helped to write the manuscript; M.K., M.C., B.-I.B., Ne.S. and B.T. contributed to data acquisition and analysis; T.D. and V.D. helped with the data analysis, provided technical assistance and material support; S.H.S and A.S. supervised the project and wrote the manuscript.Note: Supplementary Information is available on the Nature Cell Biology website. COMPETING FINANCIAL INTERESTSThe authors declare no competing financial interests. -(3-(aminomethyl)benzyl)acetamidine (1400W), a selective iNOS inhibitor (Fig. 1a). To ascertain whether p300 and/or CBP are physiologically responsible for GAPDH acetylation in intact cells, we depleted p300 and CBP by RNA interference (RNAi). Depletion of either protein decreased GAPDH acetylation, which was abolished following depletion of both CBP and p300 (Fig. 1b). We also observed acetylation of GAPDH by p300 in vitro ( Supplementary Information, Fig. S1a). Moreover, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometric analysis of nuclear GAPDH in HEK293 cells following apoptotic stress revealed acetylation at Lys 160 ( Supplementary Information, Fig. S1b, c). To confirm the site of acetylation in intact cells, we transfected HEK293 cells with GAPDH or a mutant GAPDH (GAPDH-K160R). We observed acetylation of wild-type but not the K160R mutant GAPDH (Fi...

Primary microcephaly (MCPH, for "microcephaly primary hereditary") is a disorder of brain development that results in a head circumference more than 3 standard deviations below the mean for age and gender. It has a wide variety of causes, including toxic exposures, in utero infections, and metabolic conditions. While the genetic microcephaly syndromes are relatively rare, studying these syndromes can reveal molecular mechanisms that are critical in the regulation of neural progenitor cells, brain size, and human brain evolution. Many of the causative genes for MCPH encode centrosomal proteins involved in centriole biogenesis. However, other MCPH genes fall under different mechanistic categories, notably DNA replication and repair. Recent gene discoveries and functional studies have implicated novel cellular processes, such as cytokinesis, centromere and kinetochore function, transmembrane or intracellular transport, Wnt signaling, and autophagy, as well as the apical polarity complex. Thus, MCPH genes implicate a wide variety of molecular and cellular mechanisms in the regulation of cerebral cortical size during development.

SUMMARY Mutations in several genes encoding centrosomal proteins dramatically decrease the size of the human brain. We show that Aspm and Wdr62 interact genetically to control brain size, with mice lacking Wdr62, Aspm or both showing gene dose-related centriole duplication defects that parallel the severity of the microcephaly, and increased ectopic basal progenitors, suggesting premature delamination from the ventricular zone. Wdr62 and Aspm localize to the proximal end of the mother centriole and interact physically, with Wdr62 required for Aspm localization, and both proteins, as well as microcephaly protein Cep63, required to localize CENPJ/CPAP/Sas-4, a final common target. Unexpectedly, Aspm and Wdr62 are required for normal apical complex localization and apical epithelial structure, providing a plausible unifying mechanism for the premature delamination and precocious differentiation of progenitors. Together, our results reveal links between centrioles, apical proteins, and cell fate, and illuminate how alterations in these interactions can dynamically regulate brain size.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) participates in a cell death cascade wherein a variety of stimuli activate nitric oxide (NO) synthases with NO nitrosylating GAPDH, conferring on it the ability to bind to Siah, an E3-ubiquitin-ligase, whose nuclear localization signal enables the GAPDH͞Siah protein complex to translocate to the nucleus where degradation of Siah targets elicits cell death. R-(؊)-Deprenyl (deprenyl) ameliorates the progression of disability in early Parkinson's disease and also has neuroprotective actions. We show that deprenyl and a related agent, TCH346, in subnanomolar concentrations, prevent S-nitrosylation of GAPDH, the binding of GAPDH to Siah, and nuclear translocation of GAPDH. In mice treated with the dopamine neuronal toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), low doses of deprenyl prevent binding of GAPDH and Siah1 in the dopamineenriched corpus striatum.fforts to prevent neurodegeneration in disorders such as Alzheimer's disease, Parkinson's disease (PD), Huntington's disease, and stroke have proceeded along two pathways. One involves identifying the fundamental molecular causes of these diseases, although even for Huntington's disease whose molecular causation is established, curative therapy has not followed directly. Alternatively, elucidating mechanisms of cell death may lead to agents that prevent neurodegeneration without knowing the specific disease etiology.The monoamine oxidase-B (MAO-B) inhibitor, R-(Ϫ)-Deprenyl (selegiline, hereafter designated deprenyl) (Fig. 1a) has been used in the therapy of PD with the initial goal of elevating dopamine levels (1-4). Deprenyl can delay the progression of disability in early Parkinson's disease, and recent studies also indicated that deprenyl reduces neuronal death in a variety of in vivo and in vitro experimental models. These include death of neuronal cultures induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), nitric oxide (NO), or peroxynitrite, as well as in vivo hypoxia models and peripheral or optic nerve crush (5-13). Neuroprotection by deprenyl has been suggested to be independent of MAO-B (14-16). Such a concept has been reinforced by the fact that the deprenyl derivative TCH346 (Fig. 1a) with no inhibitory action for MAO-B, also displays neuroprotective effects in culture models at concentrations as low as 0.1 pM and in intact animals at oral doses as low as 0.3 g͞kg (17-20).Recently we described a cell death signaling system whereby cell stressors activate inducible or neuronal nitric oxide synthase (NOS) with a specific S-nitrosylation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by NO (21). S-nitrosylation of GAPDH abolishes catalytic activity and confers upon GAPDH the ability to bind to Siah1 (hereafter designated Siah), an E3-ubiquitin-ligase whose nuclear localization signal mediates nuclear translocation of the GAPDH͞Siah complex. In the nucleus, GAPDH extends the rapid turnover of Siah, leading to the degradation of selected nuclear targets of Siah and apoptosis. In ...

The human neocortex has numerous specialized functional areas whose formation is poorly understood. Here, we describe a 15–base pair deletion mutation in a regulatory element of GPR56 that selectively disrupts human cortex surrounding the Sylvian fissure bilaterally including “Broca’s area,” the primary language area, by disrupting regional GPR56 expression and blocking RFX transcription factor binding. GPR56 encodes a heterotrimeric guanine nucleotide–binding protein (G protein)–coupled receptor required for normal cortical development and is expressed in cortical progenitor cells. GPR56 expression levels regulate progenitor proliferation. GPR56 splice forms are highly variable between mice and humans, and the regulatory element of gyrencephalic mammals directs restricted lateral cortical expression. Our data reveal a mechanism by which control of GPR56 expression pattern by multiple alternative promoters can influence stem cell proliferation, gyral patterning, and, potentially, neocortex evolution.

The human cerebral cortex is distinguished by its large size and abundant gyrification, or folding, yet the evolutionary mechanisms driving cortical size and structure are unknown. While genes essential for cortical developmental expansion have been identified from the genetics of human primary microcephaly (“small head”, associated with reduced brain size and intellectual disability)1, studies of these genes in mice, whose smooth cortex is one thousand times smaller than that of humans, have provided limited insight. Mutations of abnormal spindle-like microcephaly-associated (ASPM), the most common recessive microcephaly gene, reduce cortical volume by ≥50% in humans2–4, but have little effect in mice5–9, likely reflecting evolutionarily divergent functions of ASPM10,11. We used genome editing to create a germline knockout (KO) of Aspm in the ferret (Mustela putorius furo), a species with a larger, gyrified cortex and greater neural progenitor cell (NPC) diversity12–14 than mice, and closer Aspm protein sequence homology to human. Aspm KO ferrets exhibit severe microcephaly (25–40% decreases in brain weight), reflecting reduced cortical surface area without significant change in cortical thickness, as in human patients3,4, suggesting loss of “cortical units”. The mutant ferret fetal cortex displays a massive premature displacement of ventricular radial glial cells (VRG) to the outer subventricular zone (OSVZ), where many resemble outer radial glia (ORG), an NPC subtype essentially absent in mice and implicated in cerebral cortical expansion in primates12–16. These data suggest an evolutionary mechanism whereby Aspm regulates cortical expansion by controlling the affinity of VRG for the ventricular surface, thus modulating the ratio of VRG, the most undifferentiated cell type, to ORG, a more differentiated progenitor.