A systematic review and individual participant data meta-analysis of gonadal steroid hormone receptors in meningioma

OBJECTIVE

The relationship between patient and meningioma characteristics and hormone receptors (HRs) of progesterone, estrogen, and androgen remains poorly defined despite literature suggesting that meningiomas are sensitive to gonadal steroid hormones. Therefore, the authors sought to collect and compare data on this topic by performing a systematic review and meta-analysis of reported studies of HR status in meningiomas.

METHODS

A MEDLINE PubMed literature review conducted for articles published between January 1, 1951, and December 31, 2020, resulted in 634 unduplicated articles concerning meningiomas and HRs. There were 114 articles that met the criteria of detailed detection protocols for progesterone receptor (PR), estrogen receptor (ER), and/or androgen receptor (AR) using immunohistochemistry (IHC) or ligand-binding (LB) assays and simultaneous reporting of HR status with at least one variable among age, sex, histology, location, grade, or recurrence. Between-study heterogeneity and risk of bias were evaluated using graphical and statistical methods. The authors performed a multilevel meta-analysis using random-effects modeling on aggregated data (n = 4447) and individual participant data (n = 1363) with subgroup results summarized as pooled effects. A mixed-effects meta-regression using individual participant data was performed to analyze independently associated variables.

RESULTS

The 114 selected articles included data for 5810 patients with 6092 tumors analyzed to determine the expression of three HRs in human meningiomas: PRs, ARs, and ERs. The proportions of HR+ meningiomas were estimated to be 0.76 (95% CI 0.72-0.80) for PR+ and 0.50 (95% CI 0.33-0.66) for AR+ meningiomas. ER+ meningioma detection varied depending on the measurement method used and was 0.06 (95% CI 0.03-0.10) with IHC and 0.11 (95% CI 0.06-0.20) with LB assays. There were associations between age and PR and ER expression that varied between male and female patients. PR+ and AR+ were more common in female patients (OR 1.84, 95% CI 1.47-2.29 for PR and OR 4.16, 95% CI 1.62-10.68 for AR). Additionally, PR+ meningiomas were enriched in skull base locations (OR 1.89, 95% CI 1.03-3.48) and meningothelial histology (OR 1.86, 95% CI 1.23-2.81). A meta-regression showed that PR+ was independently associated with age (OR 1.11 95% CI 1.09-1.13; p < 0.0001) and WHO grade I tumors (OR 8.09, 95% CI 3.55-18.44; p < 0.0001). ER+ was negatively associated with meningothelial histology (OR 0.94, 95% CI 0.86-0.98; p = 0.044) and positively associated with convexity location (OR 1.12, 95% CI 1.05-1.18; p = 0.0003).

CONCLUSIONS

The association between HRs and meningioma features has been investigated but unexplained for decades. In this study the authors demonstrated that HR status has a strong association with known meningioma features, including WHO grade, age, female sex, histology, and anatomical location. Identifying these independent associations allows for a better understanding of meningioma heterogeneity and provides a foundation for revisiting targeted hormonal therapy in meningioma on the basis of proper patient stratification according to HR status.

Mutation of key signaling regulators of cerebrovascular development in vein of Galen malformations

To elucidate the pathogenesis of vein of Galen malformations (VOGMs), the most common and most severe of congenital brain arteriovenous malformations, we performed an integrated analysis of 310 VOGM proband-family exomes and 336,326 human cerebrovasculature single-cell transcriptomes. We found the Ras suppressor p120 RasGAP (RASA1) harbored a genome-wide significant burden of loss-of-function de novo variants (2042.5-fold, p = 4.79 x 10-7). Rare, damaging transmitted variants were enriched in Ephrin receptor-B4 (EPHB4) (17.5-fold, p = 1.22 x 10-5), which cooperates with p120 RasGAP to regulate vascular development. Additional probands had damaging variants in ACVRL1, NOTCH1, ITGB1, and PTPN11. ACVRL1 variants were also identified in a multi-generational VOGM pedigree. Integrative genomic analysis defined developing endothelial cells as a likely spatio-temporal locus of VOGM pathophysiology. Mice expressing a VOGM-specific EPHB4 kinase-domain missense variant (Phe867Leu) exhibited disrupted developmental angiogenesis and impaired hierarchical development of arterial-capillary-venous networks, but only in the presence of a "second-hit" allele. These results illuminate human arterio-venous development and VOGM pathobiology and have implications for patients and their families.

Super-enhancer hijacking drives ectopic expression of hedgehog pathway ligands in meningiomas

Hedgehog signaling mediates embryologic development of the central nervous system and other tissues and is frequently hijacked by neoplasia to facilitate uncontrolled cellular proliferation. Meningiomas, the most common primary brain tumor, exhibit Hedgehog signaling activation in 6.5% of cases, triggered by recurrent mutations in pathway mediators such as SMO. In this study, we find 35.6% of meningiomas that lack previously known drivers acquired various types of somatic structural variations affecting chromosomes 2q35 and 7q36.3. These cases exhibit ectopic expression of Hedgehog ligands, IHH and SHH, respectively, resulting in Hedgehog signaling activation. Recurrent tandem duplications involving IHH permit de novo chromatin interactions between super-enhancers within DIRC3 and a locus containing IHH. Our work expands the landscape of meningioma molecular drivers and demonstrates enhancer hijacking of Hedgehog ligands as a route to activate this pathway  in neoplasia.

Pleiotropic role of TRAF7 in skull-base meningiomas and congenital heart disease

While somatic variants of TRAF7 (Tumor necrosis factor receptor-associated factor 7) underlie anterior skull-base meningiomas, here we report the inherited mutations of TRAF7 that cause congenital heart defects. We show that TRAF7 mutants operate in a dominant manner, inhibiting protein function via heterodimerization with wild-type protein. Further, the shared genetics of the two disparate pathologies can be traced to the common origin of forebrain meninges and cardiac outflow tract from the TRAF7-expressing neural crest. Somatic and inherited mutations disrupt TRAF7-IFT57 interactions leading to cilia degradation. TRAF7-mutant meningioma primary cultures lack cilia, and TRAF7 knockdown causes cardiac, craniofacial, and ciliary defects in Xenopus and zebrafish, suggesting a mechanistic convergence for TRAF7-driven meningiomas and developmental heart defects.

Genetic dysregulation of an endothelial Ras signaling network in vein of Galen malformations

To elucidate the pathogenesis of vein of Galen malformations (VOGMs), the most common and severe congenital brain arteriovenous malformation, we performed an integrated analysis of 310 VOGM proband-family exomes and 336,326 human cerebrovasculature single-cell transcriptomes. We found the Ras suppressor p120 RasGAP ( RASA1 ) harbored a genome-wide significant burden of loss-of-function de novo variants (p=4.79×10 ^-7 ). Rare, damaging transmitted variants were enriched in Ephrin receptor-B4 ( EPHB4 ) (p=1.22×10 ^-5 ), which cooperates with p120 RasGAP to limit Ras activation. Other probands had pathogenic variants in ACVRL1 , NOTCH1 , ITGB1 , and PTPN11 . ACVRL1 variants were also identified in a multi-generational VOGM pedigree. Integrative genomics defined developing endothelial cells as a key spatio-temporal locus of VOGM pathophysiology. Mice expressing a VOGM-specific EPHB4 kinase-domain missense variant exhibited constitutive endothelial Ras/ERK/MAPK activation and impaired hierarchical development of angiogenesis-regulated arterial-capillary-venous networks, but only when carrying a "second-hit" allele. These results illuminate human arterio-venous development and VOGM pathobiology and have clinical implications.

Vascular steal and associated intratumoral aneurysms in highly vascular brain tumors: illustrative case

BACKGROUND

Intratumoral aneurysms in highly vascular brain tumors can complicate resection depending on their location and feasibility of proximal control. Seemingly unrelated neurological symptoms may be from vascular steal that can help alert the need for additional vascular imaging and augmenting surgical strategies.

OBSERVATIONS

A 29-year-old female presented with headaches and unilateral blurred vision, secondary to a large right frontal dural-based lesion with hypointense signal thought to represent calcifications. Given these latter findings and clinical suspicion for a vascular steal phenomenon to explain the blurred vision, computed tomography angiography was obtained, revealing a 4 × 2-mm intratumoral aneurysm. Diagnostic cerebral angiography confirmed this along with vascular steal by the tumor from the right ophthalmic artery. The patient underwent endovascular embolization of the intratumoral aneurysm, followed by open tumor resection in the same setting without complication, minimal blood loss, and improvement in her vision.

LESSONS

Understanding the blood supply of any tumor, but highly vascular ones in particular, and the relationship with normal vasculature is undeniably important in avoiding potentially dangerous situations and optimizing maximal safe resection. Recognition of highly vascular tumors should prompt thorough understanding of the vascular supply and relationship of intracranial vasculature with consideration of endovascular adjuncts when appropriate.

Criteria for Cerebrospinal Fluid Diversion in Retractorless Sphenoid Wing Meningioma Surgery: A Technical Report

Objective  Sphenoid wing meningiomas (SWMs) can present surgical challenges, in that they are often obscured by overlying brain, encase critical neurovascular structures, and obliterate cerebrospinal fluid (CSF) cisterns. While brain retraction can enable access, its use can have potentially deleterious effects. We report the benefits and outcomes of the criteria we have developed for use of cerebrospinal diversion to perform retractorless surgery for SWMs. Design  Technical report. Setting  Yale School of Medicine and Yale New Haven Hospital. Participants  Between May, 2019 and December, 2020, ten consecutive patients were included who met the presented criteria for SWM surgery with preoperative lumbar drain (LD) placement. Main Outcome Measures  Length of hospital stay, surgical complications, and extent of resection. Results  We have developed the following criteria for LD placement in patients with SWMs such that LDs are preoperatively placed in patients with tumors with one or more of the following criteria: (1) medial location along the sphenoid wing, (2) vascular encasement resulting in obliteration of the optic carotid cistern and/or proximal sylvian fissure, and/or (3) the presence of associated edema. CSF release, after craniotomy and sphenoid wing removal, allowed for optimization of exposure, leading to the maximal safe extent of tumor resection without brain retraction or any complications. Conclusions  Preoperative LD placement is effective in allowing for maximal extent of resection of SWMs and may be considered in cases where local CSF release is not possible. This technique is useful in those tumors located more medially, with encasement of the vasculature and/or associated with edema.

Genomic profiling of sporadic multiple meningiomas

BACKGROUND

Multiple meningiomas (MMs) rarely occur sporadically. It is unclear whether each individual tumor in a single patient behaves similarly. Moreover, the molecular mechanisms underlying the formation of sporadic MMs and clonal formation etiology of these tumors are poorly understood.

METHODS

Patients with spatially separated MMs without prior radiation exposure or a family history who underwent surgical resection of at least two meningiomas were included. Unbiased, comprehensive next generation sequencing was performed, and relevant clinical data was analyzed.

RESULTS

Fifteen meningiomas and one dural specimen from six patients were included. The majority of tumors (12/15) were WHO Grade I; one patient had bilateral MMs, one of which was Grade II, while the other was Grade I. We found 11/15 of our cohort specimens were of NF2-loss subtype. Meningiomas from 5/6 patients had a monoclonal origin, with the tumor from the remaining patient showing evidence for independent clonal formation. We identified a novel case of non-NF2 mutant MM with monoclonal etiology. MMs due to a monoclonal origin did not always display a homogenous genomic profile, but rather exhibited heterogeneity due to branching evolution.

CONCLUSIONS

Both NF2-loss and non-NF2 driven MMs can form due to monoclonal expansion and those tumors can acquire inter-tumoral heterogeneity through branched evolution. Grade I and II meningiomas can occur in the same patient. Thus, the molecular make-up and clinical behavior of one tumor in MMs, cannot reliably lend insight into that of the others and suggests the clinical management strategy for MMs should be tailored individually.

PPIL4 is essential for brain angiogenesis and implicated in intracranial aneurysms in humans

Intracranial aneurysm (IA) rupture leads to subarachnoid hemorrhage, a sudden-onset disease that often causes death or severe disability. Although genome-wide association studies have identified common genetic variants that increase IA risk moderately, the contribution of variants with large effect remains poorly defined. Using whole-exome sequencing, we identified significant enrichment of rare, deleterious mutations in PPIL4, encoding peptidyl-prolyl cis-trans isomerase-like 4, in both familial and index IA cases. Ppil4 depletion in vertebrate models causes intracerebral hemorrhage, defects in cerebrovascular morphology and impaired Wnt signaling. Wild-type, but not IA-mutant, PPIL4 potentiates Wnt signaling by binding JMJD6, a known angiogenesis regulator and Wnt activator. These findings identify a novel PPIL4-dependent Wnt signaling mechanism involved in brain-specific angiogenesis and maintenance of cerebrovascular integrity and implicate PPIL4 gene mutations in the pathogenesis of IA.

NIMG-64. TYPE OF BONY INVOLVEMENT PREDICTS GENOMIC SUBGROUP IN SPHENOID WING MENINGIOMAS

OBJECTIVE

As sphenoid wing meningiomas (SWMs) are associated with varying degrees of bony involvement, we sought to understand potential relationships between genomic subgroup and this feature.

METHODS

Patients treated at Yale-New Haven Hospital for SWM were reviewed. Genomic subgroup was determined via whole exome sequencing, while the extent of bony involvement was radiographically classified as frank tumor invasion (TI), hyperostosis only (HOOs), or both (TI+HO). Among additional clinical variables collected, a subset of tumors was identified as spheno-orbital meningiomas (SOMs). Predictive logistic regression models were developed for genomic subgroups based on pre-operative clinical features.

RESULTS

Among 64 SWMs, 53% had HOO, 9% had TI, and 14% had TI+HO; nine SOMs were identified. Tumors with invasion (i.e., TI or TI+HO) were more likely to be WHO grade II (p: 0.028). Additionally, tumors with invasion were nearly 30 times more likely to harbor NF2 mutations (OR: 27.6; p: 0.004), while hyperostosis only (without frank tumor invasion) were over 4 times more likely to have a TRAF7 mutation (OR: 4.5; p: 0.023). SOMs were a significant predictor of underlying TRAF7 mutation (OR: 10.21; p: 0.004).

CONCLUSIONS

SWMs with invasion into bone tend to be higher grade and are more likely to be NF2 mutated, while SOMs and those with hyperostosis are associated with TRAF7 variants. Pre-operative prediction of molecular subtypes based on radiographic bony characteristics may have significant biological and clinical implications based on known recurrence patterns associated with genomic drivers.

INNV-09. SURGICAL STRATEGIES FOR OLDER PATIENTS WITH GLIOBLASTOMA

OBJECTIVE

Though image-guided surgery with intraoperative magnetic resonance imaging (IoMRI) is associated with higher extent of resection, we aimed to determine the clinical outcome of its use, compared to other less time-consuming intraoperative ultrasound (IoUS), in this patient population.

METHODS

Clinical data of 221 consecutive patients aged 70 years or older, who underwent surgical resection for GBM with intraoperative ultrasonography (IoUS) alone or combination of IoMRI + IoUS at Yale New Haven Hospital and Memorial Sloan Kettering Cancer Center were retrospectively reviewed. Variables were analyzed, and comparative analyses were performed, including predictors of overall survival.

RESULTS

The addition of IoMRI was not superior to IoUS alone in terms of overall survival (OS) (HR=0.85, 95% CI 0.49-1.47; P= 0.56) or Karnofsky Performance Score (KPS) at 6 weeks postoperatively (OR=0.51, 95% CI 0.22-1.15; P= 0.102). On the contrary, the length of surgery (LOSx) was significantly longer (P&lt; 0.0001) in the IoMRI group. Postoperative complications were significantly less in the IoUS-only group (OR=0.17, 95% CI 0.3-0.46; P=0.002) and in patients who had a preoperative KPS score of 70 or higher (OR=0.092, 95% CI 0.018-0.47; P=0.004). Patients with relatively lower preoperative KPS scores (&lt; 70) showed significant clinical improvement at 6 weeks postoperatively (P=0.0002). Patients with postoperative complications were more likely to have lower KPS scores at 6 weeks postoperatively (OR=0.30, 95% CI 0.10-0.89; P= 0.031), while increased extent of resection was associated with improved KPS scores at 6 weeks postoperatively (OR=2.171, 95% CI 1.22-3.87; P= 0.009).

CONCLUSION

Aggressive management with surgical resection should be considered in older patients with GBM, even those with relatively poor KPS scores. The use of IoMRI in this patient population does not appear to yield any survival benefit over IoUS but instead significantly prolongs the length of surgery, increasing the risk for potential postoperative complications.

EPCO-29. GENOMIC PROFILING OF SPORADIC MULTIPLE MENINGIOMAS

INTRODUCTION

In rare cases, sporadic meningiomas can occur as multiple tumors in the same patient without a known germline mutation. While the underlying mechanism that leads to the formation of these multiple lesions has been hypothesized to be monoclonal or independent, the genomic profiles to support these theories remain understudied.

METHODS

Patients with an absence of family history of meningioma and prior radiation history with multiple metachronous meningiomas were included. All tissue underwent whole exome sequencing and analysis of somatic single nucleotide variations (SNV), small insertion/deletion (INDEL) events together with copy number variations (CNV) was performed. The genomic findings were correlated with clinical data.

RESULTS

A cohort of 13 meningiomas and one dural specimen, from five individuals was studied. The majority (9/13 tumors) of tumors had NF2 mutation/Chr22 loss. Four out of 5 cases had a monoclonal origination, whereas one case displayed an independent clonal formation. The somatic profile of dura was unrevealing. In contrast to the current understanding, we found monoclonal formation of multiple meningiomas is not exclusive to NF2 driven cases, as non-NF2 mutated meningiomas can too display a monoclonal etiology. Moreover, multiple monoclonal-originating lesions did not always display a homogenous profile, but rather exhibited heterogeneity through branching evolution, where some lesions acquired genomic alterations associated with aggressive behavior. The histological characterization of multiple meningioma cases does not necessarily overlap with the genomic clustering.

CONCLUSION

To our knowledge, this is the first study to use unbiased comprehensive genomic methods to reveal the heterogeneity of multiple meningioma genomic profiles. Our extensive genomic characterization of this cohort revealed that monoclonal formation can be observed both in NF2 and non-NF2 mutant meningiomas and can introduce heterogeneity. Therefore, in order to understand the full scope of each individual’s disease, detailed genomic profiling of all lesions, when possible, should be performed.

DIAPH1 Variants in Non-East Asian Patients With Sporadic Moyamoya Disease

Importance

Moyamoya disease (MMD), a progressive vasculopathy leading to narrowing and ultimate occlusion of the intracranial internal carotid arteries, is a cause of childhood stroke. The cause of MMD is poorly understood, but genetic factors play a role. Several familial forms of MMD have been identified, but the cause of most cases remains elusive, especially among non-East Asian individuals.

Objective

To assess whether ultrarare de novo and rare, damaging transmitted variants with large effect sizes are associated with MMD risk.

Design, Setting, and Participants

A genetic association study was conducted using whole-exome sequencing case-parent MMD trios in a small discovery cohort collected over 3.5 years (2016-2019); data were analyzed in 2020. Medical records from US hospitals spanning a range of 1 month to 1.5 years were reviewed for phenotyping. Exomes from a larger validation cohort were analyzed to identify additional rare, large-effect variants in the top candidate gene. Participants included patients with MMD and, when available, their parents. All participants who met criteria and were presented with the option to join the study agreed to do so; none were excluded. Twenty-four probands (22 trios and 2 singletons) composed the discovery cohort, and 84 probands (29 trios and 55 singletons) composed the validation cohort.

Main Outcomes and Measures

Gene variants were identified and filtered using stringent criteria. Enrichment and case-control tests assessed gene-level variant burden. In silico modeling estimated the probability of variant association with protein structure. Integrative genomics assessed expression patterns of MMD risk genes derived from single-cell RNA sequencing data of human and mouse brain tissue.

Results

Of the 24 patients in the discovery cohort, 14 (58.3%) were men and 18 (75.0%) were of European ancestry. Three of 24 discovery cohort probands contained 2 do novo (1-tailed Poisson P = 1.1 × 10-6) and 1 rare, transmitted damaging variant (12.5% of cases) in DIAPH1 (mammalian diaphanous-1), a key regulator of actin remodeling in vascular cells and platelets. Four additional ultrarare damaging heterozygous DIAPH1 variants (3 unphased) were identified in 3 other patients in an 84-proband validation cohort (73.8% female, 77.4% European). All 6 patients were non-East Asian. Compound heterozygous variants were identified in ena/vasodilator-stimulated phosphoproteinlike protein EVL, a mammalian diaphanous-1 interactor that regulates actin polymerization. DIAPH1 and EVL mutant probands had severe, bilateral MMD associated with transfusion-dependent thrombocytopenia. DIAPH1 and other MMD risk genes are enriched in mural cells of midgestational human brain. The DIAPH1 coexpression network converges in vascular cell actin cytoskeleton regulatory pathways.

Conclusions and Relevance

These findings provide the largest collection to date of non-East Asian individuals with sporadic MMD harboring pathogenic variants in the same gene. The results suggest that DIAPH1 is a novel MMD risk gene and impaired vascular cell actin remodeling in MMD pathogenesis, with diagnostic and therapeutic ramifications.

Barriers to Cancer Evaluation Follow-Up: Reasons and Predictors of Missed Visits in a Rural Population in Botswana

Background: Missed clinical appointments contribute to delayed cancer diagnosis, treatment, and ultimately poorer outcomes. In Botswana, a middle income sub-Saharan African country where oncology treatment is available for free to all citizens, median time from first facility visit to treatment initiation is 160 days (IQR: 59-653). Aim: To identify patient and visit characteristics associated with missing appointments, and describe reasons for missed visits among adult patients undergoing evaluation for possible cancer at public facilities in a rural district in Botswana. Methods: Patients ≥ 18 years with symptoms or signs suggestive of cancer were enrolled in the Potlako trial, an ongoing prospective health systems pilot seeking to improve timely diagnosis and treatment of cancer. Study staff tracked patient visits and if a patient missed a visit, study staff administered a brief structured phone interview to 1) determine reasons, 2) reschedule visit and 3) arrange transport support if needed. Patients who enrolled and completed follow-up between May 1, 2016 and March 23, 2018 were included in analysis. We used logistic regression (STATA v12) to explore predictors of missed visits (patient as defaulter vs not, visit being missed vs not). All factors significant in univariate analysis ( P < 0.05) were included in final models. Results: A total of 488 cancer suspects completed their cancer evaluation following a median of 7 visits (IQR: 4-11) and 125 days (IQR: 55-228). Breast and cervical cancer were the most commonly suspected malignancies. Median age was 49 (IQR: 33-64), 358 (73.4%) were female, 143 (28.4%) had an ultimate diagnosis of cancer. There were 172 missed visits, involving 94 (19.3%) patients (defaulters), including 20 (21.3%) found to have cancer, of whom 38 (39.6%) missed more than one visit. Defaulters tended to be less than 40 years (aOR 0.49, 95% CI: 0.31-0.79) and had their first visit for cancer evaluation at a general outpatient unit (aOR 2.1, 95% CI: 1.15-3.87). In the adjusted model, we found no statistically significant association between defaulter status and gender, final diagnosis, and patient's next-of-kin. Missed visits were more likely to occur on Fridays (aOR 1.50, CI: 1.05-2.15) and less likely to occur ±1 week around a public holiday (aOR 0.55, CI: 0.33-0.91). Leading reasons for missed visits were: work obligations (18.0%), family duties including child care and attending funerals (16.3%), prohibitive transport fees (10.5%), not remembering appointment date (8.7%). Conclusion: Multiple visits are required to complete evaluation for cancer suspects and missed visits are common. Our findings suggest possible interventions to improve efficiency, which include: simplifying diagnostic cascade, transport support, visit reminders, intensified counseling for younger patients and those seen at general outpatient clinics, and avoidance of Friday scheduling.

Somatic POLE mutations cause an ultramutated giant cell high-grade glioma subtype with better prognosis

BACKGROUND

Malignant high-grade gliomas (HGGs), including the most aggressive form, glioblastoma multiforme, show significant clinical and genomic heterogeneity. Despite recent advances, the overall survival of HGGs and their response to treatment remain poor. In order to gain further insight into disease pathophysiology by correlating genomic landscape with clinical behavior, thereby identifying distinct HGG molecular subgroups associated with improved prognosis, we performed a comprehensive genomic analysis.

METHODS

We analyzed and compared 720 exome-sequenced gliomas (136 from Yale, 584 from The Cancer Genome Atlas) based on their genomic, histological, and clinical features.

RESULTS

We identified a subgroup of HGGs (6 total, 4 adults and 2 children) that harbored a statistically significantly increased number of somatic mutations (mean = 9257.3 vs 76.2, P = .002). All of these "ultramutated" tumors harbored somatic mutations in the exonuclease domain of the polymerase epsilon gene (POLE), displaying a distinctive genetic profile, characterized by genomic stability and increased C-to-A transversions. Histologically, they all harbored multinucleated giant or bizarre cells, some with predominant infiltrating immune cells. One adult and both pediatric patients carried homozygous germline mutations in the mutS homolog 6 (MSH6) gene. In adults, POLE mutations were observed in patients younger than 40 years and were associated with a longer progression-free survival.

CONCLUSIONS

We identified a genomically, histologically, and clinically distinct subgroup of HGGs that harbored somatic POLE mutations and carried an improved prognosis. Identification of distinctive molecular and pathological HGG phenotypes has implications not only for improved classification but also for potential targeted treatments.

The essential role of centrosomal NDE1 in human cerebral cortex neurogenesis

We investigated three families whose offspring had extreme microcephaly at birth and profound mental retardation. Brain scans and postmortem data showed that affected individuals had brains less than 10% of expected size (≤10 standard deviation) and that in addition to a massive reduction in neuron production they displayed partially deficient cortical lamination (microlissencephaly). Other body systems were apparently unaffected and overall growth was normal. We found two distinct homozygous mutations of NDE1, c.83+1G>T (p.Ala29GlnfsX114) in a Turkish family and c.684_685del (p.Pro229TrpfsX85) in two families of Pakistani origin. Using patient cells, we found that c.83+1G>T led to the use of a novel splice site and to a frameshift after NDE1 exon 2. Transfection of tagged NDE1 constructs showed that the c.684_685del mutation resulted in a NDE1 that was unable to localize to the centrosome. By staining a patient-derived cell line that carried the c.83+1G>T mutation, we found that this endogeneously expressed mutated protein equally failed to localize to the centrosome. By examining human and mouse embryonic brains, we determined that NDE1 is highly expressed in neuroepithelial cells of the developing cerebral cortex, particularly at the centrosome. We show that NDE1 accumulates on the mitotic spindle of apical neural precursors in early neurogenesis. Thus, NDE1 deficiency causes both a severe failure of neurogenesis and a deficiency in cortical lamination. Our data further highlight the importance of the centrosome in multiple aspects of neurodevelopment.

The effects of protein kinase C activator phorbol dibutyrate on traumatic brain edema and aquaporin-4 expression

BACKGROUND

Aquaporin-4 (AQP4) is the major water channel in the central nervous system. Brain edema emerges from increased AQP4 expression in traumatic brain injury (TBI). Cell line studies have shown that the protein kinase activator phorbol ester exerts a suppressive effect on AQP4 and water permeability. The aim of this study was to investigate the effects of a phorbol ester, phorbol dibutyrate (PDBu), on increased TBI AQP4 expression and accompanying brain edema.

METHODS

Fifty-six male Wistar rats were first divided into two groups: the edema group, in which the percentage of water in brain tissue would be evaluated, and the immunohistochemical group, allowing AQP4 expression to be determined. Both groups were further sub-divided into four groups consisting of 7 subjects. These four groups were as follows: sham-operated control group, severe diffuse TBI group, 0.9% saline-treated diffuse TBI group, and the PDBu-treated diffuse TBI group (2300 µg/kg, iv). The results were evaluated statistically.

RESULTS

PDBu treatment significantly reduced brain water concentration (p<0.001). Furthermore, PDBu was found to reduce trauma-induced AQP4 upregulation (p<0.05).

CONCLUSION

This study showed that traumatic brain edema was prevented by intravenous PDBu administration via AQP4 downregulation, supporting the idea emphasizing the importance of AQP4 expression control in TBI.

Whole-exome sequencing identifies recessive WDR62 mutations in severe brain malformations

The development of the human cerebral cortex is an orchestrated process involving the birth of neural progenitors in the peri-ventricular germinal zones, cell proliferation characterized by both symmetric and asymmetric mitoses, followed by migration of post-mitotic neurons to their final destinations in 6 highly ordered, functionally-specialized layers^1,2. An understanding of the molecular mechanisms guiding these intricate processes is in its infancy, substantially driven by the discovery of rare mutations that cause malformations of cortical development (MCD)^3-6. Mapping of disease loci in putative Mendelian forms of MCD has been hindered by marked locus heterogeneity, small kindred sizes and diagnostic classifications that may not reflect molecular pathogenesis. Here we demonstrate the use of whole-exome sequencing to overcome these obstacles by identifying recessive mutations in WDR62 as the cause of a wide spectrum of severe cerebral cortical malformations including microcephaly, pachygria with cortical thickening as well as hypoplasia of the corpus callosum. Some patients with WDR62 mutations had evidence of additional abnormalities including lissencephaly, schizencephaly, polymicrogyria and, in one instance, cerebellar hypoplasia, all traits traditionally regarded as distinct entities. In mouse and humans, WDR62 transcripts and protein are enriched in neural progenitors within the ventricular and subventricular zones. WDR62 expression in the neocortex is transient, spanning the period of embryonic neurogenesis. Unlike other known microcephaly genes, WDR62 does not apparently associate with centrosomes and is predominantly nuclear in localization. These findings unify previously disparate aspects of cerebral cortical development and highlight the utility of whole-exome sequencing to identify disease loci in settings in which traditional methods have proved challenging.