The adult brain contains niches of neural stem cells that continuously add new neurons to selected circuits throughout life. Two niches have been extensively studied in various mammalian species ...including humans, the subventricular zone of the lateral ventricles and the subgranular zone of the hippocampal dentate gyrus. Recently, studies conducted mainly in rodents have identified a third neurogenic niche in the adult hypothalamus. In order to evaluate whether a neural stem cell niche also exists in the adult hypothalamus in humans, we performed multiple immunofluorescence labeling to assess the expression of a panel of neural stem/progenitor cell (NPC) markers (Sox2, nestin, vimentin, GLAST, GFAP) in the human hypothalamus and compared them with the mouse, rat and a non‐human primate species, the gray mouse lemur (Microcebus murinus). Our results show that the adult human hypothalamus contains four distinct populations of cells that express the five NPC markers: (a) a ribbon of small stellate cells that lines the third ventricular wall behind a hypocellular gap, similar to that found along the lateral ventricles, (b) ependymal cells, (c) tanycytes, which line the floor of the third ventricle in the tuberal region, and (d) a population of small stellate cells in the suprachiasmatic nucleus. In the mouse, rat and mouse lemur hypothalamus, co‐expression of NPC markers is primarily restricted to tanycytes, and these species lack a ventricular ribbon. Our work thus identifies four cell populations with the antigenic profile of NPCs in the adult human hypothalamus, of which three appear specific to humans.
The adult human hypothalamus contains four populations of cells harboring an antigenic profile of neural stem cells: ependymal cells, a ventricular ribbon of cells lying behind a hypocellular gap, tanycytes and a population of suprachiasmatic cells. In the mouse, rat and gray mouse lemur hypothalamus, a similar antigenic profile is essentially restricted to tanycytes.
Calcium (Ca2+) acts as a ubiquitous second messenger, and normal cell and tissue physiology strictly depends on the precise regulation of Ca2+ entry, storage, and release. Store‐operated Ca2+ entry ...(SOCE) is a major mechanism controlling extracellular Ca2+ entry, and mainly relies on the accurate interplay between the Ca2+ sensor STIM1 and the Ca2+ channel ORAI1. Mutations in STIM1 or ORAI1 result in abnormal Ca2+ homeostasis and are associated with severe human disorders. Recessive loss‐of‐function mutations impair SOCE and cause combined immunodeficiency, while dominant gain‐of‐function mutations induce excessive extracellular Ca2+ entry and cause tubular aggregate myopathy (TAM) and Stormorken syndrome (STRMK). TAM and STRMK are spectra of the same multisystemic disease characterized by muscle weakness, miosis, thrombocytopenia, hyposplenism, ichthyosis, dyslexia, and short stature. To date, 42 TAM/STRMK families have been described, and here we report five additional families for which we provide clinical, histological, ultrastructural, and genetic data. In this study, we list and review all new and previously reported STIM1 and ORAI1 cases, discuss the pathomechanisms of the mutations based on the known functions and the protein structure of STIM1 and ORAI1, draw a genotype/phenotype correlation, and delineate an efficient screening strategy for the molecular diagnosis of TAM/STRMK.
Electron microscopy showing tubular aggregates in muscle fibers from a TAM/STRMK patient.
Adult glioblastomas, IDH‐wildtype represent a heterogeneous group of diseases. They are resistant to conventional treatment by concomitant radiochemotherapy and carry a dismal prognosis. The ...discovery of oncogenic gene fusions in these tumors has led to prospective targeted treatments, but identification of these rare alterations in practice is challenging. Here, we report a series of 30 adult diffuse gliomas with an in frame FGFR3‐TACC3 oncogenic fusion (n = 27 WHO grade IV and n = 3 WHO grade II) as well as their histological and molecular features. We observed recurrent morphological features (monomorphous ovoid nuclei, nuclear palisading and thin parallel cytoplasmic processes, endocrinoid network of thin capillaries) associated with frequent microcalcifications and desmoplasia. We report a constant immunoreactivity for FGFR3, which is a valuable method for screening for the FGFR3‐TACC3 fusion with 100% sensitivity and 92% specificity. We confirmed the associated molecular features (typical genetic alterations of glioblastoma, except the absence of EGFR amplification, and an increased frequency of CDK4 and MDM2 amplifications). FGFR3 immunopositivity is a valuable tool to identify gliomas that are likely to harbor the FGFR3‐TACC3 fusion for inclusion in targeted therapeutic trials.
Pediatric diffuse midline gliomas are devastating diseases. Among them, diffuse midline gliomas H3K27M‐mutant are associated with worse prognosis. However, recent studies have highlighted significant ...differences in clinical behavior and biological alterations within this specific subgroup. In this context, simple markers are needed to refine the prognosis of diffuse midline gliomas H3K27M‐mutant and guide the clinical management of patients. The aims of this study were (i) to describe the molecular, immunohistochemical and, especially, chromosomal features of a cohort of diffuse midline gliomas and (ii) to focus on H3K27M‐mutant tumors to identify new prognostic markers. Patients were retrospectively selected from 2001 to 2017. Tumor samples were analyzed by immunohistochemistry (including H3K27me3, EGFR, c‐MET and p53), next‐generation sequencing and comparative genomic hybridization array. Forty‐nine patients were included in the study. The median age at diagnosis was 9 years, and the median overall survival (OS) was 9.4 months. H3F3A or HIST1H3B mutations were identified in 80% of the samples. Within the H3K27M‐mutant tumors, PDGFRA amplification, loss of 17p and a complex chromosomal profile were significantly associated with worse survival. Three prognostic markers were identified in diffuse midline gliomas H3K27M‐mutant: PDGFRA amplification, loss of 17p and a complex chromosomal profile. These markers are easy to detect in daily practice and should be considered to refine the prognosis of this entity.
Purpose
Targeted treatment for brainstem lesions requires above all a precise histopathological and molecular diagnosis. In the current technological era, robot-assisted stereotactic biopsies ...represent an accurate and safe procedure for tissue diagnosis. We present our center’s experience in frameless robot-assisted biopsies for brainstem lesions.
Methods
We performed a retrospective analysis of all patients benefitting from a frameless robot-guided stereotactic biopsy at our University Hospital, from 2001 to 2017. Patients consented to the use of data and/or images. The NeuroMate® robot (Renishaw™, UK) was used. We report on lesion location, trajectory strategy, histopathological diagnosis and procedure safety.
Results
Our series encompasses 96 patients (103 biopsies) treated during a 17 years period. Mean age at biopsy: 34.0 years (range 1–78). Most common location: pons (62.1%). Transcerebellar approach: 61 procedures (59.2%). Most common diagnoses: diffuse glioma (67.0%), metastases (7.8%) and lymphoma (6.8%). Non conclusive diagnosis: 10 cases (9.7%). After second biopsy this decreased to 4 cases (4.1%). Overall biopsy diagnostic yield: 95.8%. Permanent disability was recorded in 3 patients (2.9%, all adults), while transient complications in 17 patients (17.7%). Four cases of intra-tumoral hematoma were recorded (one case with rapid decline and fatal issue). Adjuvant targeted treatment was performed in 72.9% of patients. Mean follow-up (in the Neurosurgery Department): 2.2 years.
Conclusion
Frameless robot-assisted stereotactic biopsies can provide the initial platform towards a safe and accurate management for brainstem lesions, offering a high diagnostic yield with low permanent morbidity.
We investigated the challenging diagnostic case of a ventricular cystic glioneuronal tumor with papillary features, by RNA sequencing using the Illumina TruSight RNA Fusion panel. We did not retrieve ...the SLC44A1‐PRKCA fusion gene specific for papillary glioneuronal tumor, but an EWSR1‐PATZ1 fusion transcript. RT‐PCR followed by Sanger sequencing confirmed the EWSR1‐PATZ1 fusion. It matched with canonic EWSR1 fusion oncogene, juxtaposing the entire N‐terminal transcriptional activation domain of EWSR1 gene and the C‐terminal DNA binding domain of a transcription factor gene, PATZ1. PATZ1 protein belongs to the BTB‐ZF (broad‐complex, tramtrack and bric‐à‐brac ‐zinc finger) family. It directly regulates Pou5f1 and Nanog and is essential to maintaining stemness by inhibiting neural differentiation. EWSR1‐PATZ1 fusion is a rare event in tumors: it was only reported in six round cell sarcomas and in three gliomas of three exclusively molecular studies. The first reported glioma was a BRAFV600E negative ganglioglioma, the second a BRAFV600E negative glioneuronal tumor, not otherwise specified and the third, very recently reported, a high grade glioma, not otherwise specified. In our study, forty BRAFV600E negative gangliogliomas were screened by FISH using EWSR1 break‐apart probes. We performed methylation profiling for the index case and for seven out of the ten FISH positive cases. The index case clustered apart from other pediatric low grade glioneuronal entities, and specifically from the well‐defined ganglioglioma methylation group. An additional pediatric intraventricular ganglioglioma clustered slightly more closely with ganglioglioma, but showed differences from the main ganglioglioma group and similarities with the index case. Both cases harbored copy number variations at the PATZ1 locus. EWSR1‐PATZ1 gene fusion might define a new type of glioneuronal tumors, distinct from gangliogliomas.
Aims
We searched for recurrent pathological features and molecular alterations in a retrospective series of 72 low‐grade epilepsy‐associated neuroepithelial tumours (LEATs) with a prominent ...oligodendroglioma‐like component, in order to classify them according to the 2021 World Health Organization (WHO) classification of central nervous system (CNS) tumours.
Methods
Centralised pathological examination was performed as well as targeted molecular analysis of v‐Raf murine sarcoma viral oncogene homologue B (BRAF) and fibroblast growth factor receptor 1 (FGFR1) by multiplexed digital polymerase chain reaction (mdPCR). DNA methylation profiling was performed in cases with sufficient DNA. In cases with no genetic alteration by mdPCR and sufficient material, RNA sequencing was done.
Results
We first reclassified our cohort into three groups: ganglioglioma (GG, n = 14), dysembryoplastic neuroepithelial tumours (DNTs, n = 19) and glioneuronal tumours/paediatric‐type low‐grade glioma (LGG) not otherwise specified (GNT/PLGG NOS, n = 39). mdPCR found an alteration in 38/72 cases. Subsequent RNA sequencing revealed a fusion transcript involving BRAF, FGFR1/2/3 or neurotrophic tyrosine kinase receptor type 2 NTRK2 in 9/25 cases. DNA methylation profiling found 12/46 cases with a calibrated score ≥0.9. Unsupervised hierarchical clustering revealed two clusters: Cluster 1 was enriched with cases classified as DNT at histology, belonging to the LGG–DNT methylation class (MC), with haematopoietic progenitor cell antigen (CD34) negativity and FGRF1 alterations; Cluster 2 was enriched with cases classified at histology as GG, belonging to the LGG–GG MC MC, with BRAF V600E mutation and CD34 positivity. The tumours reclassified as GNT/PLGG NOS were equally distributed across both clusters. Interestingly, all polymorphous low‐grade neuroepithelial tumour of the young belonged to Cluster 2, whereas diffuse LGG mitogen‐activated protein kinase (MAPK) pathway‐altered were equally distributed among the two clusters. This led us to build an algorithm to classify LEATs with a prominent oligodendroglioma‐like component.
Conclusions
Integrated histomolecular diagnosis of LEATs with a prominent oligodendroglioma‐like component remains challenging. Because these tumours can be split into two major clusters of biological significance, the clinicopathological relevance of the four types recognised by the WHO CNS5 within this spectrum of tumours is questionable.
By performing centralized pathological examination as well as targeted molecular analysis by multiplexed digital PCR, DNA methylation profiling and RNA sequencing, we retrospectively studied 72 supratentorial low‐grade gliomas or glioneuronal tumours with an oligodendroglioma‐like component in order to classify them according to the 2021 WHO classification of CNS tumours. Our study highlights the challenges in the diagnosis of supratentorial tumours with an oligodendroglioma‐like component occurring in children and young adults and shows that these tumours belong to two major groups of biological relevance, although four entities are currently recognized within this spectrum of tumours by the WHO CNS5 classification.
Molecular heterogeneity is a key feature of glioblastoma that impedes patient stratification and leads to large discrepancies in mean patient survival. Here, we analyze a cohort of 96 glioblastoma ...patients with survival ranging from a few months to over 4 years. 46 tumors are analyzed by mass spectrometry-based spatially-resolved proteomics guided by mass spectrometry imaging. Integration of protein expression and clinical information highlights three molecular groups associated with immune, neurogenesis, and tumorigenesis signatures with high intra-tumoral heterogeneity. Furthermore, a set of proteins originating from reference and alternative ORFs is found to be statistically significant based on patient survival times. Among these proteins, a 5-protein signature is associated with survival. The expression of these 5 proteins is validated by immunofluorescence on an additional cohort of 50 patients. Overall, our work characterizes distinct molecular regions within glioblastoma tissues based on protein expression, which may help guide glioblastoma prognosis and improve current glioblastoma classification.
Aim
Rosette‐forming glioneuronal tumour (RGNT) is a rare central nervous system (CNS) World Health Organization (WHO) grade 1 brain neoplasm. According to the WHO 2021, essential diagnostic criteria ...are a ‘biphasic histomorphology with neurocytic and a glial component, and uniform neurocytes forming rosettes and/or perivascular pseudorosettes associated with synaptophysin expression’ and/or DNA methylation profile of RGNT whereas ‘FGFR1 mutation with co‐occurring PIK3CA and/or NF1 mutation’ are desirable criteria.
Material and methods
We report a series of 46 cases fulfilling the essential pathological diagnostic criteria for RGNT. FGFR1 and PIK3CA hotspot mutations were searched for by multiplexed digital PCR in all cases, whereas DNA methylation profiling and/or PIK3R1 and NF1 alterations were analysed in a subset of cases.
Results
Three groups were observed. The first one included 21 intracranial midline tumours demonstrating FGFR1 mutation associated with PIK3CA or PIK3R1 (n = 19) or NF1 (n = 1) or PIK3CA and NF1 (n = 1) mutation. By DNA methylation profiling, eight cases were classified as RGNT (they demonstrated FGFR1 and PIK3CA or PIK3R1 mutations). Group 2 comprised 11 cases associated with one single FGFR1 mutation. Group 3 included six cases classified as low‐grade glioma (LGG) other than RGNT (one‐sixth showed FGFR1 mutation and one a FGFR1 and NF1 mutation) and eight cases without FGFR1 mutation. Groups 2 and 3 were enriched in lateral and spinal cases.
Conclusions
We suggest adding FGFR1 mutation and intracranial midline location as essential diagnostic criteria. When DNA methylation profiling is not available, a RGNT diagnosis remains certain in cases demonstrating characteristic pathological features and FGFR1 mutation associated with either PIK3CA or PIK3R1 mutation.
Rosette‐forming glioneuronal tumour (RGNT) is a rare central nervous system World Health Organization grade 1 midline, FGFR1‐mutated glioneuronal tumour equally affecting male and female and typically occurring between 10 and 40 years. Histopathological features are not sufficient to reach RGNT diagnosis. DNA methylation profiling is the most reliable way to reach RGNT diagnosis; when lacking, a diagnosis is certain in cases demonstrating characteristic pathological features and a FGFR1 mutation associated with either PIK3CA mutation or less frequently PIK3R1 mutation.
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