Publications by authors named "Robert F Hevner"

86 Publications

ATP1A2- and ATP1A3-associated early profound epileptic encephalopathy and polymicrogyria.

Brain 2021 Apr 21. Epub 2021 Apr 21.

Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Meyer Children's Hospital, University of Florence, Florence, Italy.

Constitutional heterozygous mutations of ATP1A2 and ATP1A3, encoding for two distinct isoforms of the Na+/K+-ATPase (NKA) alpha-subunit, have been associated with familial hemiplegic migraine (ATP1A2), alternating hemiplegia of childhood (ATP1A2/A3), rapid-onset dystonia-parkinsonism, cerebellar ataxia-areflexia-progressive optic atrophy, and relapsing encephalopathy with cerebellar ataxia (all ATP1A3). A few reports have described single individuals with heterozygous mutations of ATP1A2/A3 associated with severe childhood epilepsies. Early lethal hydrops fetalis, arthrogryposis, microcephaly, and polymicrogyria have been associated with homozygous truncating mutations in ATP1A2. We investigated the genetic causes of developmental and epileptic encephalopathies variably associated with malformations of cortical development in a large cohort and identified 22 patients with de novo or inherited heterozygous ATP1A2/A3 mutations. We characterized clinical, neuroimaging and neuropathological findings, performed in silico and in vitro assays of the mutations' effects on the NKA-pump function, and studied genotype-phenotype correlations. Twenty-two patients harboured 19 distinct heterozygous mutations of ATP1A2 (six patients, five mutations) and ATP1A3 (16 patients, 14 mutations, including a mosaic individual). Polymicrogyria occurred in 10 (45%) patients, showing a mainly bilateral perisylvian pattern. Most patients manifested early, often neonatal, onset seizures with a multifocal or migrating pattern. A distinctive, 'profound' phenotype, featuring polymicrogyria or progressive brain atrophy and epilepsy, resulted in early lethality in seven patients (32%). In silico evaluation predicted all mutations to be detrimental. We tested 14 mutations in transfected COS-1 cells and demonstrated impaired NKA-pump activity, consistent with severe loss of function. Genotype-phenotype analysis suggested a link between the most severe phenotypes and lack of COS-1 cell survival, and also revealed a wide continuum of severity distributed across mutations that variably impair NKA-pump activity. We performed neuropathological analysis of the whole brain in two individuals with polymicrogyria respectively related to a heterozygous ATP1A3 mutation and a homozygous ATP1A2 mutation and found close similarities with findings suggesting a mainly neural pathogenesis, compounded by vascular and leptomeningeal abnormalities. Combining our report with other studies, we estimate that ∼5% of mutations in ATP1A2 and 12% in ATP1A3 can be associated with the severe and novel phenotypes that we describe here. Notably, a few of these mutations were associated with more than one phenotype. These findings assign novel, 'profound' and early lethal phenotypes of developmental and epileptic encephalopathies and polymicrogyria to the phenotypic spectrum associated with heterozygous ATP1A2/A3 mutations and indicate that severely impaired NKA pump function can disrupt brain morphogenesis.
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http://dx.doi.org/10.1093/brain/awab052DOI Listing
April 2021

Long-lasting analgesia via targeted in situ repression of Na1.7 in mice.

Sci Transl Med 2021 Mar;13(584)

Department of Bioengineering, University of California San Diego, San Diego, CA 92093, USA.

Current treatments for chronic pain rely largely on opioids despite their substantial side effects and risk of addiction. Genetic studies have identified in humans key targets pivotal to nociceptive processing. In particular, a hereditary loss-of-function mutation in Na1.7, a sodium channel protein associated with signaling in nociceptive sensory afferents, leads to insensitivity to pain without other neurodevelopmental alterations. However, the high sequence and structural similarity between Na subtypes has frustrated efforts to develop selective inhibitors. Here, we investigated targeted epigenetic repression of Na1.7 in primary afferents via epigenome engineering approaches based on clustered regularly interspaced short palindromic repeats (CRISPR)-dCas9 and zinc finger proteins at the spinal level as a potential treatment for chronic pain. Toward this end, we first optimized the efficiency of Na1.7 repression in vitro in Neuro2A cells and then, by the lumbar intrathecal route, delivered both epigenome engineering platforms via adeno-associated viruses (AAVs) to assess their effects in three mouse models of pain: carrageenan-induced inflammatory pain, paclitaxel-induced neuropathic pain, and BzATP-induced pain. Our results show effective repression of Na1.7 in lumbar dorsal root ganglia, reduced thermal hyperalgesia in the inflammatory state, decreased tactile allodynia in the neuropathic state, and no changes in normal motor function in mice. We anticipate that this long-lasting analgesia via targeted in vivo epigenetic repression of Na1.7 methodology we dub pain LATER, might have therapeutic potential in management of persistent pain states.
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http://dx.doi.org/10.1126/scitranslmed.aay9056DOI Listing
March 2021

Unipolar (Dendritic) Brush Cells Are Morphologically Complex and Require Tbr2 for Differentiation and Migration.

Front Neurosci 2020 8;14:598548. Epub 2021 Jan 8.

Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, United States.

Previous studies demonstrated specific expression of transcription factor Tbr2 in unipolar brush cells (UBCs) of the cerebellum during development and adulthood. To further study UBCs and the role of Tbr2 in their development we examined UBC morphology in transgenic mouse lines (reporter and lineage tracer) and also examined the effects of Tbr2 deficiency in (MGI: ) conditional knock-out (cKO) mice. In reporter and lineage tracer cerebellum, UBCs exhibited more complex morphologies than previously reported including multiple dendrites, bifurcating dendrites, and up to four dendritic brushes. We propose that "dendritic brush cells" (DBCs) may be a more apt nomenclature. In cKO cerebellum, mature UBCs were completely absent. Migration of UBC precursors from rhombic lip to cerebellar cortex and other nuclei was impaired in cKO mice. Our results indicate that UBC migration and differentiation are sensitive to Tbr2 deficiency. To investigate whether UBCs develop similarly in humans as in rodents, we studied Tbr2 expression in mid-gestational human cerebellum. Remarkably, Tbr2 UBC precursors migrate along the same pathways in humans as in rodent cerebellum and disperse to create the same "fountain-like" appearance characteristic of UBCs exiting the rhombic lip.
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http://dx.doi.org/10.3389/fnins.2020.598548DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820753PMC
January 2021

The spectrum of brain malformations and disruptions in twins.

Am J Med Genet A 2020 Nov 18. Epub 2020 Nov 18.

Department of Pediatrics, Division of Genetics and Metabolism, University of Minnesota, Minneapolis, Minnesota, USA.

Twins have an increased risk for congenital malformations and disruptions, including defects in brain morphogenesis. We analyzed data on brain imaging, zygosity, sex, and fetal demise in 56 proband twins and 7 less affected co-twins with abnormal brain imaging and compared them to population-based data and to a literature series. We separated our series into malformations of cortical development (MCD, N = 39), cerebellar malformations without MCD (N = 13), and brain disruptions (N = 11). The MCD group included 37/39 (95%) with polymicrogyria (PMG), 8/39 (21%) with pia-ependymal clefts (schizencephaly), and 15/39 (38%) with periventricular nodular heterotopia (PNH) including 2 with PNH but not PMG. Cerebellar malformations were found in 19 individuals including 13 with a cerebellar malformation only and another 6 with cerebellar malformation and MCD. The pattern varied from diffuse cerebellar hypoplasia to classic Dandy-Walker malformation. Brain disruptions were seen in 11 individuals with hydranencephaly, porencephaly, or white matter loss without cysts. Our series included an expected statistically significant excess of monozygotic (MZ) twin pairs (22/41 MZ, 54%) compared to population data (482/1448 MZ, 33.3%; p = .0110), and an unexpected statistically significant excess of dizygotic (DZ) twins (19/41, 46%) compared to the literature cohort (1/46 DZ, 2%; p < .0001. Recurrent association with twin-twin transfusion syndrome, intrauterine growth retardation, and other prenatal factors support disruption of vascular perfusion as the most likely unifying cause.
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http://dx.doi.org/10.1002/ajmg.a.61972DOI Listing
November 2020

Reelin Mediates Hippocampal Cajal-Retzius Cell Positioning and Infrapyramidal Blade Morphogenesis.

J Dev Biol 2020 Sep 18;8(3). Epub 2020 Sep 18.

Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA 98101, USA.

We have previously described hypomorphic () mutant mice, , in which the morphology of the dentate gyrus is distinct from that seen in mice. In the mutant, the infrapyramidal blade of the dentate gyrus fails to extend, while the suprapyramidal blade forms with a relatively compact granule neuron layer. Underlying this defect, we now report several developmental anomalies in the dentate gyrus. Most strikingly, the distribution of Cajal-Retzius cells was aberrant; Cajal-Retzius neurons were increased in the suprapyramidal blade, but were greatly reduced along the subpial surface of the prospective infrapyramidal blade. We also observed multiple abnormalities of the fimbriodentate junction. Firstly, progenitor cells were distributed abnormally; the "neurogenic cluster" at the fimbriodentate junction was absent, lacking the normal accumulation of Tbr2-positive intermediate progenitors. However, the number of dividing cells in the dentate gyrus was not generally decreased. Secondly, a defect of secondary glial scaffold formation, limited to the infrapyramidal blade, was observed. The densely radiating glial fibers characteristic of the normal fimbriodentate junction were absent in mutants. These fibers might be required for migration of progenitors, which may account for the failure of neurogenic cluster formation. These findings suggest the importance of the secondary scaffold and neurogenic cluster of the fimbriodentate junction in morphogenesis of the mammalian dentate gyrus. Our study provides direct genetic evidence showing that normal RELN function is required for Cajal-Retzius cell positioning in the dentate gyrus, and for formation of the fimbriodentate junction to promote infrapyramidal blade extension.
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http://dx.doi.org/10.3390/jdb8030020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7558149PMC
September 2020

Reply to Hsueh YP et al.

Eur J Hum Genet 2020 08 9;28(8):999. Epub 2020 Apr 9.

Department of Neurological Surgery, Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA.

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http://dx.doi.org/10.1038/s41431-020-0622-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7471462PMC
August 2020

Intermediate progenitors support migration of neural stem cells into dentate gyrus outer neurogenic niches.

Elife 2020 04 3;9. Epub 2020 Apr 3.

Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, United States.

The hippocampal dentate gyrus (DG) is a unique brain region maintaining neural stem cells (NCSs) and neurogenesis into adulthood. We used multiphoton imaging to visualize genetically defined progenitor subpopulations in live slices across key stages of mouse DG development, testing decades old static models of DG formation with molecular identification, genetic-lineage tracing, and mutant analyses. We found novel progenitor migrations, timings, dynamic cell-cell interactions, signaling activities, and routes underlie mosaic DG formation. Intermediate progenitors (IPs, Tbr2+) pioneered migrations, supporting and guiding later emigrating NSCs (Sox9+) through multiple transient zones prior to converging at the nascent outer adult niche in a dynamic settling process, generating all prenatal and postnatal granule neurons in defined spatiotemporal order. IPs (Dll1+) extensively targeted contacts to mitotic NSCs (Notch active), revealing a substrate for cell-cell contact support during migrations, a developmental feature maintained in adults. Mouse DG formation shares conserved features of human neocortical expansion.
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http://dx.doi.org/10.7554/eLife.53777DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7159924PMC
April 2020

What Makes the Human Brain Human?

Authors:
Robert F Hevner

Neuron 2020 03;105(5):761-763

Department of Pathology, University of California San Diego, San Diego, CA, USA. Electronic address:

Which elements of the genome endow human brains with the capacity for heightened cognitive abilities? In this issue of Neuron, Namba et al. (2020) find that ARHGAP11B, a human-specific gene, augments cerebral cortex expansion by regulating metabolic pathways in mitochondria.
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http://dx.doi.org/10.1016/j.neuron.2020.02.007DOI Listing
March 2020

Longitudinal assessment of tumor development using cancer avatars derived from genetically engineered pluripotent stem cells.

Nat Commun 2020 Jan 28;11(1):550. Epub 2020 Jan 28.

Ludwig Cancer Research San Diego Branch, 9500 Gilman Dr., CMM-East Room 3055, La Jolla, CA, 92093, USA.

Many cellular models aimed at elucidating cancer biology do not recapitulate pathobiology including tumor heterogeneity, an inherent feature of cancer that underlies treatment resistance. Here we introduce a cancer modeling paradigm using genetically engineered human pluripotent stem cells (hiPSCs) that captures authentic cancer pathobiology. Orthotopic engraftment of the neural progenitor cells derived from hiPSCs that have been genome-edited to contain tumor-associated genetic driver mutations revealed by The Cancer Genome Atlas project for glioblastoma (GBM) results in formation of high-grade gliomas. Similar to patient-derived GBM, these models harbor inter-tumor heterogeneity resembling different GBM molecular subtypes, intra-tumor heterogeneity, and extrachromosomal DNA amplification. Re-engraftment of these primary tumor neurospheres generates secondary tumors with features characteristic of patient samples and present mutation-dependent patterns of tumor evolution. These cancer avatar models provide a platform for comprehensive longitudinal assessment of human tumor development as governed by molecular subtype mutations and lineage-restricted differentiation.
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http://dx.doi.org/10.1038/s41467-020-14312-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6987220PMC
January 2020

New insights into the development of the human cerebral cortex.

J Anat 2019 09 2;235(3):432-451. Epub 2019 Aug 2.

Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA, USA.

The cerebral cortex constitutes more than half the volume of the human brain and is presumed to be responsible for the neuronal computations underlying complex phenomena, such as perception, thought, language, attention, episodic memory and voluntary movement. Rodent models are extremely valuable for the investigation of brain development, but cannot provide insight into aspects that are unique or highly derived in humans. Many human psychiatric and neurological conditions have developmental origins but cannot be studied adequately in animal models. The human cerebral cortex has some unique genetic, molecular, cellular and anatomical features, which need to be further explored. The Anatomical Society devoted its summer meeting to the topic of Human Brain Development in June 2018 to tackle these important issues. The meeting was organized by Gavin Clowry (Newcastle University) and Zoltán Molnár (University of Oxford), and held at St John's College, Oxford. The participants provided a broad overview of the structure of the human brain in the context of scaling relationships across the brains of mammals, conserved principles and recent changes in the human lineage. Speakers considered how neuronal progenitors diversified in human to generate an increasing variety of cortical neurons. The formation of the earliest cortical circuits of the earliest generated neurons in the subplate was discussed together with their involvement in neurodevelopmental pathologies. Gene expression networks and susceptibility genes associated to neurodevelopmental diseases were discussed and compared with the networks that can be identified in organoids developed from induced pluripotent stem cells that recapitulate some aspects of in vivo development. New views were discussed on the specification of glutamatergic pyramidal and γ-aminobutyric acid (GABA)ergic interneurons. With the advancement of various in vivo imaging methods, the histopathological observations can be now linked to in vivo normal conditions and to various diseases. Our review gives a general evaluation of the exciting new developments in these areas. The human cortex has a much enlarged association cortex with greater interconnectivity of cortical areas with each other and with an expanded thalamus. The human cortex has relative enlargement of the upper layers, enhanced diversity and function of inhibitory interneurons and a highly expanded transient subplate layer during development. Here we highlight recent studies that address how these differences emerge during development focusing on diverse facets of our evolution.
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http://dx.doi.org/10.1111/joa.13055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6704245PMC
September 2019

Glial injury in neurotoxicity after pediatric CD19-directed chimeric antigen receptor T cell therapy.

Ann Neurol 2019 07 27;86(1):42-54. Epub 2019 May 27.

Seattle Children's Ben Towne Center for Childhood Cancer Research, Seattle Children's Research Institute, Seattle, WA.

Objective: To test whether systemic cytokine release is associated with central nervous system inflammatory responses and glial injury in immune effector cell-associated neurotoxicity syndrome (ICANS) after chimeric antigen receptor (CAR)-T cell therapy in children and young adults.

Methods: We performed a prospective cohort study of clinical manifestations as well as imaging, pathology, CSF, and blood biomarkers on 43 subjects ages 1 to 25 who received CD19-directed CAR/T cells for acute lymphoblastic leukemia (ALL).

Results: Neurotoxicity occurred in 19 of 43 (44%) subjects. Nine subjects (21%) had CTCAE grade 3 or 4 neurological symptoms, with no neurotoxicity-related deaths. Reversible delirium, headache, decreased level of consciousness, tremor, and seizures were most commonly observed. Cornell Assessment of Pediatric Delirium (CAPD) scores ≥9 had 94% sensitivity and 33% specificity for grade ≥3 neurotoxicity, and 91% sensitivity and 72% specificity for grade ≥2 neurotoxicity. Neurotoxicity correlated with severity of cytokine release syndrome, abnormal past brain magnetic resonance imaging (MRI), and higher peak CAR-T cell numbers in blood, but not cerebrospinal fluid (CSF). CSF levels of S100 calcium-binding protein B and glial fibrillary acidic protein increased during neurotoxicity, indicating astrocyte injury. There were concomitant increases in CSF white blood cells, protein, interferon-γ (IFNγ), interleukin (IL)-6, IL-10, and granzyme B (GzB), with concurrent elevation of serum IFNγ IL-10, GzB, granulocyte macrophage colony-stimulating factor, macrophage inflammatory protein 1 alpha, and tumor necrosis factor alpha, but not IL-6. We did not find direct evidence of endothelial activation.

Interpretation: Our data are most consistent with ICANS as a syndrome of systemic inflammation, which affects the brain through compromise of the neurovascular unit and astrocyte injury. ANN NEUROL 2019.
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http://dx.doi.org/10.1002/ana.25502DOI Listing
July 2019

Homozygous Mutations in CSF1R Cause a Pediatric-Onset Leukoencephalopathy and Can Result in Congenital Absence of Microglia.

Am J Hum Genet 2019 05 11;104(5):936-947. Epub 2019 Apr 11.

Department of Pediatrics, Division of Genetic Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA; Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA 98101, USA. Electronic address:

Microglia are CNS-resident macrophages that scavenge debris and regulate immune responses. Proliferation and development of macrophages, including microglia, requires Colony Stimulating Factor 1 Receptor (CSF1R), a gene previously associated with a dominant adult-onset neurological condition (adult-onset leukoencephalopathy with axonal spheroids and pigmented glia). Here, we report two unrelated individuals with homozygous CSF1R mutations whose presentation was distinct from ALSP. Post-mortem examination of an individual with a homozygous splice mutation (c.1754-1G>C) demonstrated several structural brain anomalies, including agenesis of corpus callosum. Immunostaining demonstrated almost complete absence of microglia within this brain, suggesting that it developed in the absence of microglia. The second individual had a homozygous missense mutation (c.1929C>A [p.His643Gln]) and presented with developmental delay and epilepsy in childhood. We analyzed a zebrafish model (csf1r) lacking Csf1r function and found that their brains also lacked microglia and had reduced levels of CUX1, a neuronal transcription factor. CUX1 neurons were also reduced in sections of homozygous CSF1R mutant human brain, identifying an evolutionarily conserved role for CSF1R signaling in production or maintenance of CUX1 neurons. Since a large fraction of CUX1 neurons project callosal axons, we speculate that microglia deficiency may contribute to agenesis of the corpus callosum via reduction in CUX1 neurons. Our results suggest that CSF1R is required for human brain development and establish the csf1r fish as a model for microgliopathies. In addition, our results exemplify an under-recognized form of phenotypic expansion, in which genes associated with well-recognized, dominant conditions produce different phenotypes when biallelically mutated.
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http://dx.doi.org/10.1016/j.ajhg.2019.03.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6506793PMC
May 2019

Malformations of Cerebral Cortex Development: Molecules and Mechanisms.

Annu Rev Pathol 2019 01;14:293-318

Department of Pathology, University of Washington School of Medicine, Seattle, Washington 98195, USA; email: ,

Malformations of cortical development encompass heterogeneous groups of structural brain anomalies associated with complex neurodevelopmental disorders and diverse genetic and nongenetic etiologies. Recent progress in understanding the genetic basis of brain malformations has been driven by extraordinary advances in DNA sequencing technologies. For example, somatic mosaic mutations that activate mammalian target of rapamycin signaling in cortical progenitor cells during development are now recognized as the cause of hemimegalencephaly and some types of focal cortical dysplasia. In addition, research on brain development has begun to reveal the cellular and molecular bases of cortical gyrification and axon pathway formation, providing better understanding of disorders involving these processes. New neuroimaging techniques with improved resolution have enhanced our ability to characterize subtle malformations, such as those associated with intellectual disability and autism. In this review, we broadly discuss cortical malformations and focus on several for which genetic etiologies have elucidated pathogenesis.
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http://dx.doi.org/10.1146/annurev-pathmechdis-012418-012927DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6938687PMC
January 2019

Intermediate progenitors and Tbr2 in cortical development.

Authors:
Robert F Hevner

J Anat 2019 09 24;235(3):616-625. Epub 2019 Jan 24.

Department of Pathology, University of California, San Diego, CA, USA.

In developing cerebral cortex, intermediate progenitors (IPs) are transit amplifying cells that specifically express Tbr2 (gene: Eomes), a T-box transcription factor. IPs are derived from radial glia (RG) progenitors, the neural stem cells of developing cortex. In turn, IPs generate glutamatergic projection neurons (PNs) exclusively. IPs are found in ventricular and subventricular zones, where they differentiate as distinct ventricular IP (vIP) and outer IP (oIP) subtypes. Morphologically, IPs have short processes, resembling filopodia or neurites, that transiently contact other cells, most importantly dividing RG cells to mediate Delta-Notch signaling. Also, IPs secrete a chemokine, Cxcl12, which guides interneuron and microglia migrations and promotes thalamocortical axon growth. In mice, IPs produce clones of 1-12 PNs, sometimes spanning multiple layers. After mitosis, IP daughter cells undergo asymmetric cell death in the majority of instances. In mice, Tbr2 is necessary for PN differentiation and subtype specification, and to repress IP-genic transcription factors. Tbr2 directly represses Insm1, an IP-genic transcription factor gene, as well as Pax6, a key activator of Tbr2 transcription. Without Tbr2, abnormal IPs transiently accumulate in elevated numbers. More broadly, Tbr2 regulates the transcriptome by activating or repressing hundreds of direct target genes. Notably, Tbr2 'unlocks' and activates PN-specific genes, such as Tbr1, by recruiting Jmjd3, a histone H3K27me3 demethylase that removes repressive epigenetic marks placed by polycomb repressive complex 2. IPs have played an important role in the evolution and gyrification of mammalian cerebral cortex, and TBR2 is essential for human brain development.
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http://dx.doi.org/10.1111/joa.12939DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6656625PMC
September 2019

Intermittent Hypoxia Disrupts Adult Neurogenesis and Synaptic Plasticity in the Dentate Gyrus.

J Neurosci 2019 02 26;39(7):1320-1331. Epub 2018 Dec 26.

Institute for Integrative Physiology, Section of Emergency Medicine, The University of Chicago, Chicago, Illinois 60637,

Individuals with sleep apnea often exhibit changes in cognitive behaviors consistent with alterations in the hippocampus. It is hypothesized that adult neurogenesis in the dentate gyrus is an ongoing process that maintains normal hippocampal function in many mammalian species, including humans. However, the impact of chronic intermittent hypoxia (IH), a principal consequence of sleep apnea, on hippocampal adult neurogenesis remains unclear. Using a murine model, we examined the impact of 30 d of IH (IH) on adult neurogenesis and synaptic plasticity in the dentate gyrus. Although IH did not affect paired-pulse facilitation, IH suppressed long-term potentiation (LTP). Immunohistochemical experiments also indicate that IH perturbs multiple aspects of adult neurogenesis. IH increased the number of proliferating Sox2 neural progenitor cells in the subgranular zone yet reduced the number of doublecortin-positive neurons. Consistent with these findings, cell lineage tracing revealed that IH increased the proportion of radial glial cells in the subgranular zone, yet decreased the proportion of adult-born neurons in the dentate gyrus. While administration of a superoxide anion scavenger during IH did not prevent neural progenitor cell proliferation, it mitigated the IH-dependent suppression of LTP and prevented adult-born neuron loss. These data demonstrate that IH causes both reactive oxygen species-dependent and reactive oxygen species-independent effects on adult neurogenesis and synaptic plasticity in the dentate gyrus. Our findings identify cellular and neurophysiological changes in the hippocampus that may contribute to cognitive and behavioral deficits occurring in sleep apnea. Individuals with sleep apnea experience periods of intermittent hypoxia (IH) that can negatively impact many aspects of brain function. Neurons are continually generated throughout adulthood to support hippocampal physiology and behavior. This study demonstrates that IH exposure attenuates hippocampal long-term potentiation and reduces adult neurogenesis. Antioxidant treatment mitigates these effects indicating that oxidative signaling caused by IH is a significant factor that impairs synaptic plasticity and reduces adult neurogenesis in the hippocampus.
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http://dx.doi.org/10.1523/JNEUROSCI.1359-18.2018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6381238PMC
February 2019

Clonal analysis reveals laminar fate multipotency and daughter cell apoptosis of mouse cortical intermediate progenitors.

Development 2018 09 14;145(17). Epub 2018 Sep 14.

Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA

In developing cerebral cortex, most pyramidal-projection neurons are produced by intermediate progenitors (IPs), derived in turn from radial glial progenitors. Although IPs produce neurons for all cortical layers, it is unknown whether individual IPs produce multiple or single laminar fates, and the potential of IPs for extended proliferation remains uncertain. Previously, we found that, at the population level, early IPs (present during lower-layer neurogenesis) produce lower- and upper-layer neurons, whereas late IPs produce upper-layer neurons only. Here, we employed mosaic analysis with double markers (MADM) in mice to sparsely label early IP clones. Most early IPs produced 1-2 neurons for deep layers only. Less frequently, early IPs produced larger clones (up to 12 neurons) spanning lower and upper layers, or upper layers only. The majority of IP-derived clones (∼66%) were associated with asymmetric cell death after the first division. These data demonstrate that laminar fate is not predetermined, at least in some IPs. Rather, the heterogeneous sizes and laminar fates of early IP clones are correlated with cell division/death/differentiation choices and neuron birthdays, respectively.
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http://dx.doi.org/10.1242/dev.164335DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6141770PMC
September 2018

The Epigenetic Factor Landscape of Developing Neocortex Is Regulated by Transcription Factors Pax6→ Tbr2→ Tbr1.

Front Neurosci 2018 22;12:571. Epub 2018 Aug 22.

Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, United States.

Epigenetic factors (EFs) regulate multiple aspects of cerebral cortex development, including proliferation, differentiation, laminar fate, and regional identity. The same neurodevelopmental processes are also regulated by transcription factors (TFs), notably the Pax6→ Tbr2→ Tbr1 cascade expressed sequentially in radial glial progenitors (RGPs), intermediate progenitors, and postmitotic projection neurons, respectively. Here, we studied the EF landscape and its regulation in embryonic mouse neocortex. Microarray and hybridization assays revealed that many EF genes are expressed in specific cortical cell types, such as intermediate progenitors, or in rostrocaudal gradients. Furthermore, many EF genes are directly bound and transcriptionally regulated by Pax6, Tbr2, or Tbr1, as determined by chromatin immunoprecipitation-sequencing and gene expression analysis of TF mutant cortices. Our analysis demonstrated that Pax6, Tbr2, and Tbr1 form a direct feedforward genetic cascade, with direct feedback repression. Results also revealed that each TF regulates multiple EF genes that control DNA methylation, histone marks, chromatin remodeling, and non-coding RNA. For example, Tbr1 activates and to promote the formation of non-canonical Polycomb repressive complex 1 (PRC1). Also, Pax6, Tbr2, and Tbr1 collectively drive massive changes in the subunit isoform composition of BAF chromatin remodeling complexes during differentiation: for example, a novel switch from (Baf40c) to (Baf40a), the latter directly activated by Tbr2. Of 11 subunits predominantly in neuronal BAF, 7 were transcriptionally activated by Pax6, Tbr2, or Tbr1. Using EFs, Pax6→ Tbr2→ Tbr1 effect persistent changes of gene expression in cell lineages, to propagate features such as regional and laminar identity from progenitors to neurons.
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http://dx.doi.org/10.3389/fnins.2018.00571DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6113890PMC
August 2018

Congenital Zika virus infection as a silent pathology with loss of neurogenic output in the fetal brain.

Nat Med 2018 03 5;24(3):368-374. Epub 2018 Feb 5.

Washington National Primate Research Center, Seattle, Washington, USA.

Zika virus (ZIKV) is a flavivirus with teratogenic effects on fetal brain, but the spectrum of ZIKV-induced brain injury is unknown, particularly when ultrasound imaging is normal. In a pregnant pigtail macaque (Macaca nemestrina) model of ZIKV infection, we demonstrate that ZIKV-induced injury to fetal brain is substantial, even in the absence of microcephaly, and may be challenging to detect in a clinical setting. A common and subtle injury pattern was identified, including (i) periventricular T2-hyperintense foci and loss of fetal noncortical brain volume, (ii) injury to the ependymal epithelium with underlying gliosis and (iii) loss of late fetal neuronal progenitor cells in the subventricular zone (temporal cortex) and subgranular zone (dentate gyrus, hippocampus) with dysmorphic granule neuron patterning. Attenuation of fetal neurogenic output demonstrates potentially considerable teratogenic effects of congenital ZIKV infection even without microcephaly. Our findings suggest that all children exposed to ZIKV in utero should receive long-term monitoring for neurocognitive deficits, regardless of head size at birth.
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http://dx.doi.org/10.1038/nm.4485DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5839998PMC
March 2018

A dual-fluorescence reporter in the Eomes locus for live imaging and medium-term lineage tracing.

Genesis 2017 08 14;55(8). Epub 2017 Jul 14.

Institute of Experimental and Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Freiburg, Freiburg, Germany.

The T-box transcription factor Eomes (also known as Tbr2) shows short-lived expression in various localized domains of the embryo, including epiblast cells during gastrulation and intermediate progenitor cells in the cerebral cortex. In these tissues Eomes fulfills crucial roles for lineage specification of progenitors. To directly observe Eomes-dependent cell lineages in the living embryo, we generated a novel dual-fluorescence reporter allele that expresses a membrane-bound tdTomato protein for investigation of cell morphology and a nuclear GFP for cell tracing. This allele recapitulates endogenous EOMES protein expression and is suitable for live imaging. We found that the allele can also be used as a short-to-medium-term lineage tracer, as GFP persists in cells longer than EOMES protein and marks Eomes-dependent lineages with a timeframe of days to weeks depending on the proliferation rate. In summary, we present a novel genetic tool for investigation of Eomes-dependent cell types by live imaging and lineage tracing.
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http://dx.doi.org/10.1002/dvg.23043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5568967PMC
August 2017

C-Terminal Region Truncation of RELN Disrupts an Interaction with VLDLR, Causing Abnormal Development of the Cerebral Cortex and Hippocampus.

J Neurosci 2017 01;37(4):960-971

Center for Developmental Biology and Regenerative Medicine and

We discovered a hypomorphic reelin (Reln) mutant with abnormal cortical lamination and no cerebellar hypoplasia. This mutant, Reln, carries a chemically induced splice-site mutation that truncates the C-terminal region (CTR) domain of RELN protein and displays remarkably distinct phenotypes from reeler The mutant does not have an inverted cortex, but cortical neurons overmigrate and invade the marginal zone, which are characteristics similar to a phenotype seen in the cerebral cortex of Vldlr mice. The dentate gyrus shows a novel phenotype: the infrapyramidal blade is absent, while the suprapyramidal blade is present and laminated. Genetic epistasis analysis showed that Reln/Apoer2 double homozygotes have phenotypes akin to those of reeler mutants, while Reln/Vldlr mice do not. Given that the receptor double knock-out mice resemble reeler mutants, we infer that Reln/Apoer2 double homozygotes have both receptor pathways disrupted. This suggests that CTR-truncation disrupts an interaction with VLDLR (very low-density lipoprotein receptor), while the APOER2 signaling pathway remains active, which accounts for the hypomorphic phenotype in Reln mice. A RELN-binding assay confirms that CTR truncation significantly decreases RELN binding to VLDLR, but not to APOER2. Together, the in vitro and in vivo results demonstrate that the CTR domain confers receptor-binding specificity of RELN.

Significance Statement: Reelin signaling is important for brain development and is associated with human type II lissencephaly. Reln mutations in mice and humans are usually associated with cerebellar hypoplasia. A new Reln mutant with a truncation of the C-terminal region (CTR) domain shows that Reln mutation can cause abnormal phenotypes in the cortex and hippocampus without cerebellar hypoplasia. Genetic analysis suggested that CTR truncation disrupts an interaction with the RELN receptor VLDLR (very low-density lipoprotein receptor); this was confirmed by a RELN-binding assay. This result provides a mechanistic explanation for the hypomorphic phenotype of the CTR-deletion mutant, and further suggests that Reln mutations may cause more subtle forms of human brain malformation than classic lissencephalies.
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http://dx.doi.org/10.1523/JNEUROSCI.1826-16.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5296787PMC
January 2017

Fetal brain lesions after subcutaneous inoculation of Zika virus in a pregnant nonhuman primate.

Nat Med 2016 11 12;22(11):1256-1259. Epub 2016 Sep 12.

Department of Pediatrics, University of Washington, Seattle, Washington, USA.

We describe the development of fetal brain lesions after Zika virus (ZIKV) inoculation in a pregnant pigtail macaque. Periventricular lesions developed within 10 d and evolved asymmetrically in the occipital-parietal lobes. Fetal autopsy revealed ZIKV in the brain and significant cerebral white matter hypoplasia, periventricular white matter gliosis, and axonal and ependymal injury. Our observation of ZIKV-associated fetal brain lesions in a nonhuman primate provides a model for therapeutic evaluation.
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http://dx.doi.org/10.1038/nm.4193DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5365281PMC
November 2016

A comprehensive transcriptional map of primate brain development.

Nature 2016 07 13;535(7612):367-75. Epub 2016 Jul 13.

Allen Institute for Brain Science, Seattle, Washington 98109, USA.

The transcriptional underpinnings of brain development remain poorly understood, particularly in humans and closely related non-human primates. We describe a high-resolution transcriptional atlas of rhesus monkey (Macaca mulatta) brain development that combines dense temporal sampling of prenatal and postnatal periods with fine anatomical division of cortical and subcortical regions associated with human neuropsychiatric disease. Gene expression changes more rapidly before birth, both in progenitor cells and maturing neurons. Cortical layers and areas acquire adult-like molecular profiles surprisingly late in postnatal development. Disparate cell populations exhibit distinct developmental timing of gene expression, but also unexpected synchrony of processes underlying neural circuit construction including cell projection and adhesion. Candidate risk genes for neurodevelopmental disorders including primary microcephaly, autism spectrum disorder, intellectual disability, and schizophrenia show disease-specific spatiotemporal enrichment within developing neocortex. Human developmental expression trajectories are more similar to monkey than rodent, although approximately 9% of genes show human-specific regulation with evidence for prolonged maturation or neoteny compared to monkey.
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http://dx.doi.org/10.1038/nature18637DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5325728PMC
July 2016

Intermediate Progenitor Cohorts Differentially Generate Cortical Layers and Require Tbr2 for Timely Acquisition of Neuronal Subtype Identity.

Cell Rep 2016 06 16;16(1):92-105. Epub 2016 Jun 16.

Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA; Department of Neurological Surgery, University of Washington School of Medicine, Seattle, WA 98104, USA. Electronic address:

Intermediate progenitors (IPs) amplify the production of pyramidal neurons, but their role in selective genesis of cortical layers or neuronal subtypes remains unclear. Using genetic lineage tracing in mice, we find that IPs destined to produce upper cortical layers first appear early in corticogenesis, by embryonic day 11.5. During later corticogenesis, IP laminar fates are progressively limited to upper layers. We examined the role of Tbr2, an IP-specific transcription factor, in laminar fate regulation using Tbr2 conditional mutant mice. Upon Tbr2 inactivation, fewer neurons were produced by immediate differentiation and laminar fates were shifted upward. Genesis of subventricular mitoses was, however, not reduced in the context of a Tbr2-null cortex. Instead, neuronal and laminar differentiation were disrupted and delayed. Our findings indicate that upper-layer genesis depends on IPs from many stages of corticogenesis and that Tbr2 regulates the tempo of laminar fate implementation for all cortical layers.
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http://dx.doi.org/10.1016/j.celrep.2016.05.072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4927342PMC
June 2016

Association of MTOR Mutations With Developmental Brain Disorders, Including Megalencephaly, Focal Cortical Dysplasia, and Pigmentary Mosaicism.

JAMA Neurol 2016 07;73(7):836-845

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.

Importance: Focal cortical dysplasia (FCD), hemimegalencephaly, and megalencephaly constitute a spectrum of malformations of cortical development with shared neuropathologic features. These disorders are associated with significant childhood morbidity and mortality.

Objective: To identify the underlying molecular cause of FCD, hemimegalencephaly, and diffuse megalencephaly.

Design, Setting, And Participants: Patients with FCD, hemimegalencephaly, or megalencephaly (mean age, 11.7 years; range, 2-32 years) were recruited from Pediatric Hospital A. Meyer, the University of Hong Kong, and Seattle Children's Research Institute from June 2012 to June 2014. Whole-exome sequencing (WES) was performed on 8 children with FCD or hemimegalencephaly using standard-depth (50-60X) sequencing in peripheral samples (blood, saliva, or skin) from the affected child and their parents and deep (150-180X) sequencing in affected brain tissue. Targeted sequencing and WES were used to screen 93 children with molecularly unexplained diffuse or focal brain overgrowth. Histopathologic and functional assays of phosphatidylinositol 3-kinase-AKT (serine/threonine kinase)-mammalian target of rapamycin (mTOR) pathway activity in resected brain tissue and cultured neurons were performed to validate mutations.

Main Outcomes And Measures: Whole-exome sequencing and targeted sequencing identified variants associated with this spectrum of developmental brain disorders.

Results: Low-level mosaic mutations of MTOR were identified in brain tissue in 4 children with FCD type 2a with alternative allele fractions ranging from 0.012 to 0.086. Intermediate-level mosaic mutation of MTOR (p.Thr1977Ile) was also identified in 3 unrelated children with diffuse megalencephaly and pigmentary mosaicism in skin. Finally, a constitutional de novo mutation of MTOR (p.Glu1799Lys) was identified in 3 unrelated children with diffuse megalencephaly and intellectual disability. Molecular and functional analysis in 2 children with FCD2a from whom multiple affected brain tissue samples were available revealed a mutation gradient with an epicenter in the most epileptogenic area. When expressed in cultured neurons, all MTOR mutations identified here drive constitutive activation of mTOR complex 1 and enlarged neuronal size.

Conclusions And Relevance: In this study, mutations of MTOR were associated with a spectrum of brain overgrowth phenotypes extending from FCD type 2a to diffuse megalencephaly, distinguished by different mutations and levels of mosaicism. These mutations may be sufficient to cause cellular hypertrophy in cultured neurons and may provide a demonstration of the pattern of mosaicism in brain and substantiate the link between mosaic mutations of MTOR and pigmentary mosaicism in skin.
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http://dx.doi.org/10.1001/jamaneurol.2016.0363DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4979321PMC
July 2016

Evolution of the mammalian dentate gyrus.

Authors:
Robert F Hevner

J Comp Neurol 2016 Feb 29;524(3):578-94. Epub 2015 Jul 29.

Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, 98101.

The dentate gyrus (DG), a part of the hippocampal formation, has important functions in learning, memory, and adult neurogenesis. Compared with homologous areas in sauropsids (birds and reptiles), the mammalian DG is larger and exhibits qualitatively different phenotypes: 1) folded (C- or V-shaped) granule neuron layer, concave toward the hilus and delimited by a hippocampal fissure; 2) nonperiventricular adult neurogenesis; and 3) prolonged ontogeny, involving extensive abventricular (basal) migration and proliferation of neural stem and progenitor cells (NSPCs). Although gaps remain, available data indicate that these DG traits are present in all orders of mammals, including monotremes and marsupials. The exception is Cetacea (whales, dolphins, and porpoises), in which DG size, convolution, and adult neurogenesis have undergone evolutionary regression. Parsimony suggests that increased growth and convolution of the DG arose in stem mammals concurrently with nonperiventricular adult hippocampal neurogenesis and basal migration of NSPCs during development. These traits could all result from an evolutionary change that enhanced radial migration of NSPCs out of the periventricular zones, possibly by epithelial-mesenchymal transition, to colonize and maintain nonperiventricular proliferative niches. In turn, increased NSPC migration and clonal expansion might be a consequence of growth in the cortical hem (medial patterning center), which produces morphogens such as Wnt3a, generates Cajal-Retzius neurons, and is regulated by Lhx2. Finally, correlations between DG convolution and neocortical gyrification (or capacity for gyrification) suggest that enhanced abventricular migration and proliferation of NSPCs played a transformative role in growth and folding of neocortex as well as archicortex.
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http://dx.doi.org/10.1002/cne.23851DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4706817PMC
February 2016

PI3K/AKT pathway mutations cause a spectrum of brain malformations from megalencephaly to focal cortical dysplasia.

Brain 2015 Jun 25;138(Pt 6):1613-28. Epub 2015 Feb 25.

2 Seattle Children's Research Institute, Centre for Integrative Brain Research, Seattle, WA, USA 3 University of Washington, Paediatrics, Seattle, WA, USA.

Malformations of cortical development containing dysplastic neuronal and glial elements, including hemimegalencephaly and focal cortical dysplasia, are common causes of intractable paediatric epilepsy. In this study we performed multiplex targeted sequencing of 10 genes in the PI3K/AKT pathway on brain tissue from 33 children who underwent surgical resection of dysplastic cortex for the treatment of intractable epilepsy. Sequencing results were correlated with clinical, imaging, pathological and immunohistological phenotypes. We identified mosaic activating mutations in PIK3CA and AKT3 in this cohort, including cancer-associated hotspot PIK3CA mutations in dysplastic megalencephaly, hemimegalencephaly, and focal cortical dysplasia type IIa. In addition, a germline PTEN mutation was identified in a male with hemimegalencephaly but no peripheral manifestations of the PTEN hamartoma tumour syndrome. A spectrum of clinical, imaging and pathological abnormalities was found in this cohort. While patients with more severe brain imaging abnormalities and systemic manifestations were more likely to have detected mutations, routine histopathological studies did not predict mutation status. In addition, elevated levels of phosphorylated S6 ribosomal protein were identified in both neurons and astrocytes of all hemimegalencephaly and focal cortical dysplasia type II specimens, regardless of the presence or absence of detected PI3K/AKT pathway mutations. In contrast, expression patterns of the T308 and S473 phosphorylated forms of AKT and in vitro AKT kinase activities discriminated between mutation-positive dysplasia cortex, mutation-negative dysplasia cortex, and non-dysplasia epilepsy cortex. Our findings identify PI3K/AKT pathway mutations as an important cause of epileptogenic brain malformations and establish megalencephaly, hemimegalencephaly, and focal cortical dysplasia as part of a single pathogenic spectrum.
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http://dx.doi.org/10.1093/brain/awv045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4614119PMC
June 2015

Brain overgrowth in disorders of RTK-PI3K-AKT signaling: a mosaic of malformations.

Authors:
Robert F Hevner

Semin Perinatol 2015 Feb 26;39(1):36-43. Epub 2014 Nov 26.

Department of Neurological Surgery, University of Washington School of Medicine, Seattle, WA; Department of Pathology, University of Washington School of Medicine, Seattle, WA; Center for Integrative Brain Research, Seattle Children׳s Research Institute, 1900 Ninth Ave, Seattle, WA 98101. Electronic address:

Disorders of brain overgrowth are significant causes of intractable epilepsy, intellectual disability, autism, and other complex neurological problems. The pathology of these disorders is sometimes striking and characteristic, as in hemimegalencephaly, but can also be subtle, as in autism. Recent genetic studies have shown that many diverse forms of brain overgrowth are caused by de novo mutations that increase activity in the receptor tyrosine kinase (RTK)-phosphatidylinositol-3-kinase (PI3K)-AKT signaling pathway, a key mediator of signaling by growth factors in the developing brain, such as fibroblast growth factors. In cases where mutations arise in postzygotic embryos, brain regions exhibit mosaic pathology that reflects the distribution of mutant cells, ranging from focal cortical dysplasia to lobar or hemispheric overgrowth. In turn, the histopathology of these disorders is also remarkably varied. The common underlying mechanisms of RTK-PI3K-AKT overactivation suggest new possibilities for drugs that inhibit this pathway.
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http://dx.doi.org/10.1053/j.semperi.2014.10.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4268391PMC
February 2015

Neuropathologic features of pontocerebellar hypoplasia type 6.

J Neuropathol Exp Neurol 2014 Nov;73(11):1009-25

From the Calgary Laboratory Services (JTJ) and Alberta Children's Hospital Foundation Research Institute for Child and Maternal Health, Department of Medical Genetics (AMI), University of Calgary, Calgary, Alberta; Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario (ACS, MRV, FCC, DEB, JMichaud, KMB); and McGill University and Genome Quebec Innovation Center, Montreal, Quebec (JAS, JMajewski), Canada; Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (RFH, RAD); and Department of Neurological Surgery, University of Washington, Seattle, Washington (RFH).

Pontocerebellar hypoplasia is a group of severe developmental disorders with prenatal onset affecting the growth and function of the brainstem and cerebellum. The rarity and genetic heterogeneity of this group of disorders can make molecular diagnosis challenging. We report 3 siblings who were born to nonconsanguineous parents, were hypotonic at birth, developed seizures, had repeated apneic spells, and died within 2 months of life. Neuroimaging showed that all had profound cerebellar hypoplasia and simplified cortical gyration. Genetic analysis by whole-exome sequencing demonstrated compound heterozygous mutations in the mitochondrial arginyl transfer RNA synthetase gene RARS2, indicating that the children had pontocerebellar hypoplasia type 6. Autopsies on the younger twin siblings revealed small and immature cerebella at an approximate developmental age of less than 18 weeks. The basis pontis showed regressive changes, and the medulla had marked inferior olivary hypoplasia. The brains of both twins were microencephalic and had simplified gyri; cortices were immature, and deep white matter had extensive astrocytosis. The findings suggest a near-normal embryologic period followed by midgestation developmental slowing or cessation and later regression in select anatomic regions. This is the first detailed description of neuropathologic findings associated with pontocerebellar hypoplasia type 6 and demonstrates the profound effects of RARS2 disruption during early neurodevelopment.
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http://dx.doi.org/10.1097/NEN.0000000000000123DOI Listing
November 2014

Germline SMARCE1 mutations predispose to both spinal and cranial clear cell meningiomas.

J Pathol 2014 Dec 6;234(4):436-40. Epub 2014 Oct 6.

Manchester Centre for Genomic Medicine, University of Manchester, Manchester Academic Health Sciences Centre (MAHSC), UK.

We recently reported SMARCE1 mutations as a cause of spinal clear cell meningiomas. Here, we have identified five further cases with non-NF2 spinal meningiomas and six with non-NF2 cranial meningiomas. Three of the spinal cases and three of the cranial cases were clear cell tumours. We screened them for SMARCE1 mutations and investigated copy number changes in all point mutation-negative samples. We identified two novel mutations in individuals with spinal clear cell meningiomas and three mutations in individuals with cranial clear cell meningiomas. Copy number analysis identified a large deletion of the 5' end of SMARCE1 in two unrelated probands with spinal clear cell meningiomas. Testing of affected and unaffected relatives of one of these individuals identified the same deletion in two affected female siblings and their unaffected father, providing further evidence of incomplete penetrance of meningioma disease in males. In addition, we found loss of SMARCE1 protein in three of 10 paraffin-embedded cranial clear cell meningiomas. Together, these results demonstrate that loss of SMARCE1 is relevant to cranial as well as spinal meningiomas. Our study broadens the spectrum of mutations in the SMARCE1 gene and expands the phenotype to include cranial clear cell meningiomas.
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http://dx.doi.org/10.1002/path.4427DOI Listing
December 2014