Infantile onset encephalomyopathy, retinopathy, optic atrophy, and mitochondrial DNA depletion associated with a novel pathogenic DHX16 variant.

We studied a patient with mitochondrial DNA depletion in skeletal muscle and a multiorgan phenotype, including fatal encephalomyopathy, retinopathy, optic atrophy, and sensorineural hearing loss. Instead of pathogenic variants in the mitochondrial maintenance genes, we identified previously unpublished variant in DHX16 gene, a de novo heterozygous c.1360C>T (p. Arg454Trp). Variants in DHX16 encoding for DEAH-box RNA helicase have previously been reported only in five patients with a phenotype called as neuromuscular oculoauditory syndrome including developmental delay, neuromuscular symptoms, and ocular or auditory defects with or without seizures. We performed functional studies on patient-derived fibroblasts and skeletal muscle revealing, that the DHX16 expression was decreased. Clinical features together with functional data suggest, that our patient's disease is associated with a novel pathogenic DHX16 variant, and mtDNA depletion could be a secondary manifestation of the disease.

Molecular characterization of DICER1-mutated pituitary blastoma.

Pituitary blastoma (PitB) has recently been identified as a rare and potentially lethal pediatric intracranial tumor. All cases that have been studied molecularly possess at least one DICER1 pathogenic variant. Here, we characterized nine pituitary samples, including three fresh frozen PitBs, three normal fetal pituitary glands and three normal postnatal pituitary glands using small-RNA-Seq, RNA-Seq, methylation profiling, whole genome sequencing and Nanostring® miRNA analyses; an extended series of 21 pituitary samples was used for validation purposes. These analyses demonstrated that DICER1 RNase IIIb hotspot mutations in PitBs induced improper processing of miRNA precursors, resulting in aberrant 5p-derived miRNA products and a skewed distribution of miRNAs favoring mature 3p over 5p miRNAs. This led to dysregulation of hundreds of 5p and 3p miRNAs and concomitant dysregulation of numerous mRNA targets. Gene expression analysis revealed PRAME as the most significantly upregulated gene (500-fold increase). PRAME is a member of the Retinoic Acid Receptor (RAR) signaling pathway and in PitBs, the RAR, WNT and NOTCH pathways are dysregulated. Cancer Hallmarks analysis showed that PI3K pathway is activated in the tumors. Whole genome sequencing demonstrated a quiet genome with very few somatic alterations. The comparison of methylation profiles to publicly available data from ~ 3000 other central nervous system tumors revealed that PitBs have a distinct methylation profile compared to all other tumors, including pituitary adenomas. In conclusion, this comprehensive characterization of DICER1-related PitB revealed key molecular underpinnings of PitB and identified pathways that could potentially be exploited in the treatment of this tumor.

Duplication 2p16 is associated with perisylvian polymicrogyria.

Polymicrogyria (PMG) is a heterogeneous brain malformation that may result from prenatal vascular disruption or infection, or from numerous genetic causes that still remain difficult to identify. We identified three unrelated patients with polymicrogyria and duplications of chromosome 2p, defined the smallest region of overlap, and performed gene pathway analysis using Cytoscape. The smallest region of overlap in all three children involved 2p16.1-p16.3. All three children have bilateral perisylvian polymicrogyria (BPP), intrauterine and postnatal growth deficiency, similar dysmorphic features, and poor feeding. Two of the three children had documented intellectual disability. Gene pathway analysis suggested a number of developmentally relevant genes and gene clusters that were over-represented in the critical region. We narrowed a rare locus for polymicrogyria to a region of 2p16.1-p16.3 that contains 33-34 genes, 23 of which are expressed in cerebral cortex during human fetal development. Using pathway analysis, we showed that several of the duplicated genes contribute to neurodevelopmental pathways including morphogen, cytokine, hormonal and growth factor signaling, regulation of cell cycle progression, cell morphogenesis, axonal guidance, and neuronal migration. These findings strengthen the evidence for a novel locus associated with polymicrogyria on 2p16.1-p16.3, and comprise the first step in defining the underlying genetic etiology.

Recessive osteogenesis imperfecta caused by missense mutations in SPARC.

Secreted protein, acidic, cysteine-rich (SPARC) is a glycoprotein that binds to collagen type I and other proteins in the extracellular matrix. Using whole-exome sequencing to identify the molecular defect in two unrelated girls with severe bone fragility and a clinical diagnosis of osteogenesis imperfecta type IV, we identified two homozygous variants in SPARC (GenBank: NM_003118.3; c.497G>A [p.Arg166His] in individual 1; c.787G>A [p.Glu263Lys] in individual 2). Published modeling and site-directed mutagenesis studies had previously shown that the residues substituted by these mutations form an intramolecular salt bridge in SPARC and are essential for the binding of SPARC to collagen type I. The amount of SPARC secreted by skin fibroblasts was reduced in individual 1 but appeared normal in individual 2. The migration of collagen type I alpha chains produced by these fibroblasts was mildly delayed on SDS-PAGE gel, suggesting some overmodification of collagen during triple helical formation. Pulse-chase experiments showed that collagen type I secretion was mildly delayed in skin fibroblasts from both individuals. Analysis of an iliac bone sample from individual 2 showed that trabecular bone was hypermineralized on the material level. In conclusion, these observations show that homozygous mutations in SPARC can give rise to severe bone fragility in humans.

NHLRC2 variants identified in patients with fibrosis, neurodegeneration, and cerebral angiomatosis (FINCA): characterisation of a novel cerebropulmonary disease.

A novel multi-organ disease that is fatal in early childhood was identified in three patients from two non-consanguineous families. These children were born asymptomatic but at the age of 2 months they manifested progressive multi-organ symptoms resembling no previously known disease. The main clinical features included progressive cerebropulmonary symptoms, malabsorption, progressive growth failure, recurrent infections, chronic haemolytic anaemia and transient liver dysfunction. In the affected children, neuropathology revealed increased angiomatosis-like leptomeningeal, cortical and superficial white matter vascularisation and congestion, vacuolar degeneration and myelin loss in white matter, as well as neuronal degeneration. Interstitial fibrosis and previously undescribed granuloma-like lesions were observed in the lungs. Hepatomegaly, steatosis and collagen accumulation were detected in the liver. A whole-exome sequencing of the two unrelated families with the affected children revealed the transmission of two heterozygous variants in the NHL repeat-containing protein 2 (NHLRC2); an amino acid substitution p.Asp148Tyr and a frameshift 2-bp deletion p.Arg201GlyfsTer6. NHLRC2 is highly conserved and expressed in multiple organs and its function is unknown. It contains a thioredoxin-like domain; however, an insulin turbidity assay on human recombinant NHLRC2 showed no thioredoxin activity. In patient-derived fibroblasts, NHLRC2 levels were low, and only p.Asp148Tyr was expressed. Therefore, the allele with the frameshift deletion is likely non-functional. Development of the Nhlrc2 null mouse strain stalled before the morula stage. Morpholino knockdown of nhlrc2 in zebrafish embryos affected the integrity of cells in the midbrain region. This is the first description of a fatal, early-onset disease; we have named it FINCA disease based on the combination of pathological features that include fibrosis, neurodegeneration, and cerebral angiomatosis.

ExomeAI: detection of recurrent allelic imbalance in tumors using whole-exome sequencing data.

SUMMARY: Whole-exome sequencing (WES) has extensively been used in cancer genome studies; however, the use of WES data in the study of loss of heterozygosity or more generally allelic imbalance (AI) has so far been very limited, which highlights the need for user-friendly and flexible software that can handle low-quality datasets. We have developed a statistical approach, ExomeAI, for the detection of recurrent AI events using WES datasets, specifically where matched normal samples are not available. AVAILABILITY: ExomeAI is a web-based application, publicly available at: http://genomequebec.mcgill.ca/exomeai. CONTACT: JavadNadaf@gmail.com or somayyeh.fahiminiya@mcgill.ca SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Germline and somatic FGFR1 abnormalities in dysembryoplastic neuroepithelial tumors.

Dysembryoplastic neuroepithelial tumor (DNET) is a benign brain tumor associated with intractable drug-resistant epilepsy. In order to identify underlying genetic alterations and molecular mechanisms, we examined three family members affected by multinodular DNETs as well as 100 sporadic tumors from 96 patients, which had been referred to us as DNETs. We performed whole-exome sequencing on 46 tumors and targeted sequencing for hotspot FGFR1 mutations and BRAF p.V600E was used on the remaining samples. FISH, copy number variation assays and Sanger sequencing were used to validate the findings. By whole-exome sequencing of the familial cases, we identified a novel germline FGFR1 mutation, p.R661P. Somatic activating FGFR1 mutations (p.N546K or p.K656E) were observed in the tumor samples and further evidence for functional relevance was obtained by in silico modeling. The FGFR1 p.K656E mutation was confirmed to be in cis with the germline p.R661P variant. In 43 sporadic cases, in which the diagnosis of DNET could be confirmed on central blinded neuropathology review, FGFR1 alterations were also frequent and mainly comprised intragenic tyrosine kinase FGFR1 duplication and multiple mutants in cis (25/43; 58.1 %) while BRAF p.V600E alterations were absent (0/43). In contrast, in 53 cases, in which the diagnosis of DNET was not confirmed, FGFR1 alterations were less common (10/53; 19 %; p < 0.0001) and hotspot BRAF p.V600E (12/53; 22.6 %) (p < 0.001) prevailed. We observed overexpression of phospho-ERK in FGFR1 p.R661P and p.N546K mutant expressing HEK293 cells as well as FGFR1 mutated tumor samples, supporting enhanced MAP kinase pathway activation under these conditions. In conclusion, constitutional and somatic FGFR1 alterations and MAP kinase pathway activation are key events in the pathogenesis of DNET. These findings point the way towards existing targeted therapies.

Nonsense mutation in the WDR73 gene is associated with Galloway-Mowat syndrome.

BACKGROUND: Neuroanatomical defects are often present in children with severe developmental delay and intellectual disabilities. Few genetic loci have been associated with disorders of neurodevelopment. Our objective of the present study was to analyse a consanguineous Arab family showing some of the hallmark signs of a rare cerebellar hypoplasia-related neurodevelopmental syndrome as a strategy for discovering a causative genetic mutation. METHODS: We used whole exome sequencing to identify the causative mutation in two female siblings of a consanguineous Arab family showing some of the hallmark signs of a cerebellar-hypoplasia-related neurodevelopmental disorder. Direct Sanger sequencing was used to validate the candidate mutations that cosegregated with the phenotype. Gene expression and loss of function studies were carried out in the zebrafish model system to examine the role of the candidate gene in neurodevelopment. RESULTS: Patients presented with severe global developmental delay, intellectual disability, hypoplasia of the cerebellum and biochemical findings suggestive of nephrotic disease. Whole exome sequencing of the two patients revealed a shared nonsense homozygous variant in WDR73 (p.Q235X (c.703C>T)) resulting in loss of the last 144 amino acids of the protein. The variant segregated according to a recessive mode of inheritance in this family and was absent from public and our inhouse databases. We examined the developmental role of WDR73 using a loss-of-function paradigm in zebrafish. There was a significant brain growth and morphogenesis defect in wdr73 knockdown embryos resulting in a poorly differentiated midbrain and cerebellum. CONCLUSIONS: The results provide new insight into the functional role of WDR73 in brain development and show that perturbation of its function in an inherited disorder in humans is associated with cerebellar hypoplasia as well as nephrotic disease, consistent with Galloway-Mowat Syndrome.

Transcriptome profiling of granulosa and theca cells during dominant follicle development in the horse.

Several aspects of equine ovarian physiology are unique among domestic species. Moreover, follicular growth patterns are very similar between horses and humans. This study aimed to characterize, for the first time, global gene expression profiles associated with growth and preovulatory (PO) maturation of equine dominant follicles. Granulosa cells (GCs) and theca interna cells (TCs) were harvested from follicles (n = 5) at different stages of an ovulatory wave in mares corresponding to early dominance (ED; diameter ≥22 mm), late dominance (LD; ≥33 mm) and PO stage (34 h after administration of crude equine gonadotropins at LD stage), and separately analyzed on a horse gene expression microarray, followed by validation using quantitative PCR and immunoblotting/immunohistochemistry. Numbers of differentially expressed transcripts (DETs; ≥2-fold; P < 0.05) during the ED-LD and LD-PO transitions were 546 and 2419 in GCs and 5 and 582 in TCs. The most prominent change in GCs was the down-regulation of transcripts associated with cell division during both ED-LD and LD-PO. In addition, DET sets during LD-PO in GCs were enriched for genes involved in cell communication/adhesion, antioxidation/detoxification, immunity/inflammation, and cholesterol biosynthesis. In contrast, the largest change in TCs during the LD-PO transition was an up-regulation of genes involved in immune activation, with other DET sets mapping to GPCR/cAMP signaling, lipid/amino acid metabolism, and cell proliferation/survival and differentiation. In conclusion, distinct expression profiles were identified between growing and PO follicles and, particularly, between GCs and TCs within each stage. Several DETs were identified that have not been associated with follicle development in other species.

Exomic and epigenomic analysis of pulmonary blastoma.

OBJECTIVE: Pulmonary blastoma is a rare, biphasic, adult-onset lung tumor. In this study, we investigate whether DICER1 pathogenic variants are a feature of pulmonary blastomas through in-depth analysis of the molecular events defining them. METHODS: We performed exome-wide sequencing and DNA methylation profiling of 8 pulmonary blastomas from 6 affected persons. RESULTS: We identified biallelic somatic DICER1 pathogenic variants in 7 of 8 cases. The remaining case had a solitary missense pathogenic variant in the RNase IIIb domain of DICER1. Six of 8 cases carried a CTNNB1 hotspot variant and 4 of 8 had a somatic pathogenic variant in TP53. Methylation analysis showed that the pulmonary blastomas clustered with other DICER1-mutated tumors and not with other more common types of lung cancer. CONCLUSION: We conclude somatic DICER1 pathogenic variants are the major driver of pulmonary blastoma and are likely to act in conjunction with CTNNB1 hotspot variants that are often present.

Identity and nature of neural stem cells in the adult human subventricular zone.

The existence of neural stem cells (NSCs) in adult human brain neurogenic regions remains unresolved. To address this, we created a cell atlas of the adult human subventricular zone (SVZ) derived from fresh neurosurgical samples using single-cell transcriptomics. We discovered 2 adult radial glia (RG)-like populations, aRG1 and aRG2. aRG1 shared features with fetal early RG (eRG) and aRG2 were transcriptomically similar to fetal outer RG (oRG). We also captured early neuronal and oligodendrocytic NSC states. We found that the biological programs driven by their transcriptomes support their roles as early lineage NSCs. Finally, we show that these NSCs have the potential to transition between states and along lineage trajectories. These data reveal that multipotent NSCs reside in the adult human SVZ.

Invasive growth of brain metastases is linked to CHI3L1 release from pSTAT3-positive astrocytes.

BACKGROUND: Compared to minimally invasive brain metastases (MI BrM), highly invasive (HI) lesions form abundant contacts with cells in the peritumoral brain parenchyma and are associated with poor prognosis. Reactive astrocytes (RAs) labeled by phosphorylated STAT3 (pSTAT3) have recently emerged as a promising therapeutic target for BrM. Here, we explore whether the BrM invasion pattern is influenced by pSTAT3+ RAs and may serve as a predictive biomarker for STAT3 inhibition. METHODS: We used immunohistochemistry to identify pSTAT3+ RAs in HI and MI human and patient-derived xenograft (PDX) BrM. Using PDX, syngeneic, and transgenic mouse models of HI and MI BrM, we assessed how pharmacological STAT3 inhibition or RA-specific STAT3 genetic ablation affected BrM growth in vivo. Cancer cell invasion was modeled in vitro using a brain slice-tumor co-culture assay. We performed single-cell RNA sequencing of human BrM and adjacent brain tissue. RESULTS: RAs expressing pSTAT3 are situated at the brain-tumor interface and drive BrM invasive growth. HI BrM invasion pattern was associated with delayed growth in the context of STAT3 inhibition or genetic ablation. We demonstrate that pSTAT3+ RAs secrete Chitinase 3-like-1 (CHI3L1), which is a known STAT3 transcriptional target. Furthermore, single-cell RNA sequencing identified CHI3L1-expressing RAs in human HI BrM. STAT3 activation, or recombinant CHI3L1 alone, induced cancer cell invasion into the brain parenchyma using a brain slice-tumor plug co-culture assay. CONCLUSIONS: Together, these data reveal that pSTAT3+ RA-derived CHI3L1 is associated with BrM invasion, implicating STAT3 and CHI3L1 as clinically relevant therapeutic targets for the treatment of HI BrM.

PRAME protein expression in DICER1-related tumours.

DICER1 syndrome is an autosomal dominant tumour predisposition syndrome usually affecting persons under 30 years of age. Many of the associated benign and malignant lesions occur almost exclusively in DICER1 syndrome. One such tumour, pituitary blastoma (pitB), overexpresses PRAME 500x above control levels. PRAME (PReferentially expressed Antigen in MElanoma) is expressed in malignancies that are not DICER1-related (e.g. melanoma). To address whether PRAME expression is part of the DICER1 phenotype, or simply a feature of pitB, a series of 75 DICER1-mutated specimens and 33 non-mutated specimens was surveyed using immunohistochemistry for PRAME, together with EZH2, which complexes with PRAME. In DICER1-mutated specimens, positive staining for PRAME was only seen in malignant tumours; 7 of 11 histological types and 34/62 individual tumours were positive, while non-tumourous lesions were always negative. Pleuropulmonary blastoma (PPB) showed a continuum in staining, with type I lesions being PRAME negative (n = 7) but all type II and type III lesions PRAME positive (n = 7). Similarly, cystic nephroma (CN) was negative (n = 8), with anaplastic sarcoma of the kidney being positive (n = 2). However, one atypical CN with mesenchymal cell proliferation was PRAME-positive. Embryonal rhabdomyosarcoma (RMS) with DICER1 pathogenic variants (PVs) was positive for PRAME (5/6), but the same tumour type without DICER1 PVs was also positive (9/15). Staining for EZH2 corresponded to that seen with PRAME, validating the latter. This study leads us to conclude that (1) PRAME expression occurs in two-thirds of DICER1-related malignancies; (2) PRAME may be a marker for the progression that certain DICER1-related lesions are thought to undergo, such as PPB and CN; and (3) PRAME expression in some tumours, such as RMS, appears to be an intrinsic feature of the tumour, rather than specifically related to DICER1 PVs. Therapy directed against PRAME may offer novel treatment options in patients with the DICER1 syndrome.

Glioblastoma scRNA-seq shows treatment-induced, immune-dependent increase in mesenchymal cancer cells and structural variants in distal neural stem cells.

BACKGROUND: Glioblastoma is a treatment-resistant brain cancer. Its hierarchical cellular nature and its tumor microenvironment (TME) before, during, and after treatments remain unresolved. METHODS: Here, we used single-cell RNA sequencing to analyze new and recurrent glioblastoma and the nearby subventricular zone (SVZ). RESULTS: We found 4 glioblastoma neural lineages are present in new and recurrent glioblastoma with an enrichment of the cancer mesenchymal lineage, immune cells, and reactive astrocytes in early recurrences. Cancer lineages were hierarchically organized around cycling oligodendrocytic and astrocytic progenitors that are transcriptomically similar but distinct to SVZ neural stem cells (NSCs). Furthermore, NSCs from the SVZ of patients with glioblastoma harbored glioblastoma chromosomal anomalies. Lastly, mesenchymal cancer cells and TME reactive astrocytes shared similar gene signatures which were induced by radiotherapy in a myeloid-dependent fashion in vivo. CONCLUSION: These data reveal the dynamic, immune-dependent nature of glioblastoma's response to treatments and identify distant NSCs as likely cells of origin.

Germline Missense Variants in CDC20 Result in Aberrant Mitotic Progression and Familial Cancer.

CDC20 is a coactivator of the anaphase promoting complex/cyclosome (APC/C) and is essential for mitotic progression. APC/CCDC20 is inhibited by the spindle assembly checkpoint (SAC), which prevents premature separation of sister chromatids and aneuploidy in daughter cells. Although overexpression of CDC20 is common in many cancers, oncogenic mutations have never been identified in humans. Using whole-exome sequencing, we identified heterozygous missense CDC20 variants (L151R and N331K) that segregate with ovarian germ cell tumors in two families. Functional characterization showed these mutants retain APC/C activation activity but have impaired binding to BUBR1, a component of the SAC. Expression of L151R and N331K variants promoted mitotic slippage in HeLa cells and primary skin fibroblasts derived from carriers. Generation of mice carrying the N331K variant using CRISPR-Cas9 showed that, although homozygous N331K mice were nonviable, heterozygotes displayed accelerated oncogenicity of Myc-driven cancers. These findings highlight an unappreciated role for CDC20 variants as tumor-promoting genes. SIGNIFICANCE: Two germline CDC20 missense variants that segregate with cancer in two families compromise the spindle assembly checkpoint and lead to aberrant mitotic progression, which could predispose cells to transformation. See related commentary by Villarroya-Beltri and Malumbres, p. 3432.

Invasive growth associated with cold-inducible RNA-binding protein expression drives recurrence of surgically resected brain metastases.

BACKGROUND: Sixty percent of surgically resected brain metastases (BrM) recur within 1 year. These recurrences have long been thought to result from the dispersion of cancer cells during surgery. We tested the alternative hypothesis that invasion of cancer cells into the adjacent brain plays a significant role in local recurrence and shortened overall survival. METHODS: We determined the invasion pattern of 164 surgically resected BrM and correlated with local recurrence and overall survival. We performed single-cell RNA sequencing (scRNAseq) of >15,000 cells from BrM and adjacent brain tissue. Validation of targets was performed with a novel cohort of BrM patient-derived xenografts (PDX) and patient tissues. RESULTS: We demonstrate that invasion of metastatic cancer cells into the adjacent brain is associated with local recurrence and shortened overall survival. scRNAseq of paired tumor and adjacent brain samples confirmed the existence of invasive cancer cells in the tumor-adjacent brain. Analysis of these cells identified cold-inducible RNA-binding protein (CIRBP) overexpression in invasive cancer cells compared to cancer cells located within the metastases. Applying PDX models that recapitulate the invasion pattern observed in patients, we show that CIRBP is overexpressed in highly invasive BrM and is required for efficient invasive growth in the brain. CONCLUSIONS: These data demonstrate peritumoral invasion as a driver of treatment failure in BrM that is functionally mediated by CIRBP. These findings improve our understanding of the biology underlying postoperative treatment failure and lay the groundwork for rational clinical trial development based upon invasion pattern in surgically resected BrM.

A functionally impaired missense variant identified in French Canadian families implicates FANCI as a candidate ovarian cancer-predisposing gene.

BACKGROUND: Familial ovarian cancer (OC) cases not harbouring pathogenic variants in either of the BRCA1 and BRCA2 OC-predisposing genes, which function in homologous recombination (HR) of DNA, could involve pathogenic variants in other DNA repair pathway genes. METHODS: Whole exome sequencing was used to identify rare variants in HR genes in a BRCA1 and BRCA2 pathogenic variant negative OC family of French Canadian (FC) ancestry, a population exhibiting genetic drift. OC cases and cancer-free individuals from FC and non-FC populations were investigated for carrier frequency of FANCI c.1813C>T; p.L605F, the top-ranking candidate. Gene and protein expression were investigated in cancer cell lines and tissue microarrays, respectively. RESULTS: In FC subjects, c.1813C>T was more common in familial (7.1%, 3/42) than sporadic (1.6%, 7/439) OC cases (P = 0.048). Carriers were detected in 2.5% (74/2950) of cancer-free females though female/male carriers were more likely to have a first-degree relative with OC (121/5249, 2.3%; Spearman correlation = 0.037; P = 0.011), suggesting a role in risk. Many of the cancer-free females had host factors known to reduce risk to OC which could influence cancer risk in this population. There was an increased carrier frequency of FANCI c.1813C>T in BRCA1 and BRCA2 pathogenic variant negative OC families, when including the discovery family, compared to cancer-free females (3/23, 13%; OR = 5.8; 95%CI = 1.7-19; P = 0.005). In non-FC subjects, 10 candidate FANCI variants were identified in 4.1% (21/516) of Australian OC cases negative for pathogenic variants in BRCA1 and BRCA2, including 10 carriers of FANCI c.1813C>T. Candidate variants were significantly more common in familial OC than in sporadic OC (P = 0.04). Localization of FANCD2, part of the FANCI-FANCD2 (ID2) binding complex in the Fanconi anaemia (FA) pathway, to sites of induced DNA damage was severely impeded in cells expressing the p.L605F isoform. This isoform was expressed at a reduced level, destabilized by DNA damaging agent treatment in both HeLa and OC cell lines, and exhibited sensitivity to cisplatin but not to a poly (ADP-ribose) polymerase inhibitor. By tissue microarray analyses, FANCI protein was consistently expressed in fallopian tube epithelial cells and only expressed at low-to-moderate levels in 88% (83/94) of OC samples. CONCLUSIONS: This is the first study to describe candidate OC variants in FANCI, a member of the ID2 complex of the FA DNA repair pathway. Our data suggest that pathogenic FANCI variants may modify OC risk in cancer families.

Exome sequencing study of partial agenesis of the corpus callosum in men with developmental delay, epilepsy, and microcephaly.

BACKGROUND: This study reports the genetic features of four Caucasian males from the Saguenay-Lac-St-Jean region affected by partial agenesis of the corpus callosum (ACC) with hypotonia, epilepsy, developmental delay, microcephaly, hypoplasia, and autistic behavior. METHODS: We performed whole exome sequencing (WES) to identify new genes involved in this pathological phenotype. The regions of interest were subsequently sequenced for family members. RESULTS: Single-nucleotide variations (SNVs) and insertions or deletions were detected in genes potentially implicated in brain defects observed in these patients. One patient did not have mutations in genes related to ACC, but carried a de novo pathogenic mutation in Mucolipin-1 (MCOLN1) and was diagnosed with mucolipidosis type IV. Among the other probands, missense SNVs were observed in DCLK2 (Doublecortin Like Kinase 2), HERC2 (HECT And RLD Domain Containing E3 Ubiquitin Protein Ligase 2), and KCNH3 (Potassium channel, voltage-gated, subfamily H, member 3). One patient also carried a non-frameshift insertion in CACNA1A (Cav2.1(P/Q-type) calcium channels). CONCLUSION: Although no common genetic defect was observed in this study, we provide evidence for new avenues of investigation for ACC, such as molecular pathways involving HERC2, CACNA1A, KCNH3, and more importantly DCLK2. We also allowed to diagnose an individual with mucolipidosis type IV.

Single-cell RNA-seq reveals that glioblastoma recapitulates a normal neurodevelopmental hierarchy.

Cancer stem cells are critical for cancer initiation, development, and treatment resistance. Our understanding of these processes, and how they relate to glioblastoma heterogeneity, is limited. To overcome these limitations, we performed single-cell RNA sequencing on 53586 adult glioblastoma cells and 22637 normal human fetal brain cells, and compared the lineage hierarchy of the developing human brain to the transcriptome of cancer cells. We find a conserved neural tri-lineage cancer hierarchy centered around glial progenitor-like cells. We also find that this progenitor population contains the majority of the cancer's cycling cells, and, using RNA velocity, is often the originator of the other cell types. Finally, we show that this hierarchal map can be used to identify therapeutic targets specific to progenitor cancer stem cells. Our analyses show that normal brain development reconciles glioblastoma development, suggests a possible origin for glioblastoma hierarchy, and helps to identify cancer stem cell-specific targets.

Author Correction: Single-cell RNA-seq reveals that glioblastoma recapitulates a normal neurodevelopmental hierarchy.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.