Choroid plexus mast cells drive tumor-associated hydrocephalus.

Tumor-associated hydrocephalus (TAH) is a common and lethal complication of brain metastases. Although other factors beyond mechanical obstructions have been suggested, the exact mechanisms are unknown. Using single-nucleus RNA sequencing and spatial transcriptomics, we find that a distinct population of mast cells locate in the choroid plexus and dramatically increase during TAH. Genetic fate tracing and intracranial mast-cell-specific tryptase knockout showed that choroid plexus mast cells (CPMCs) disrupt cilia of choroid plexus epithelia via the tryptase-PAR2-FoxJ1 pathway and consequently increase cerebrospinal fluid production. Mast cells are also found in the human choroid plexus. Levels of tryptase in cerebrospinal fluid are closely associated with clinical severity of TAH. BMS-262084, an inhibitor of tryptase, can cross the blood-brain barrier, inhibit TAH in vivo, and alleviate mast-cell-induced damage of epithelial cilia in a human pluripotent stem-cell-derived choroid plexus organoid model. Collectively, we uncover the function of CPMCs and provide an attractive therapy for TAH.

The choroid plexus links innate immunity to CSF dysregulation in hydrocephalus.

The choroid plexus (ChP) is the blood-cerebrospinal fluid (CSF) barrier and the primary source of CSF. Acquired hydrocephalus, caused by brain infection or hemorrhage, lacks drug treatments due to obscure pathobiology. Our integrated, multi-omic investigation of post-infectious hydrocephalus (PIH) and post-hemorrhagic hydrocephalus (PHH) models revealed that lipopolysaccharide and blood breakdown products trigger highly similar TLR4-dependent immune responses at the ChP-CSF interface. The resulting CSF "cytokine storm", elicited from peripherally derived and border-associated ChP macrophages, causes increased CSF production from ChP epithelial cells via phospho-activation of the TNF-receptor-associated kinase SPAK, which serves as a regulatory scaffold of a multi-ion transporter protein complex. Genetic or pharmacological immunomodulation prevents PIH and PHH by antagonizing SPAK-dependent CSF hypersecretion. These results reveal the ChP as a dynamic, cellularly heterogeneous tissue with highly regulated immune-secretory capacity, expand our understanding of ChP immune-epithelial cell cross talk, and reframe PIH and PHH as related neuroimmune disorders vulnerable to small molecule pharmacotherapy.

Convergence of multiple RNA-silencing pathways on GW182/TNRC6.

The RNA-binding protein TRIM71/LIN-41 is a phylogenetically conserved developmental regulator that functions in mammalian stem cell reprogramming, brain development, and cancer. TRIM71 recognizes target mRNAs through hairpin motifs and silences them through molecular mechanisms that await identification. Here, we uncover that TRIM71 represses its targets through RNA-supported interaction with TNRC6/GW182, a core component of the miRNA-induced silencing complex (miRISC). We demonstrate that AGO2, TRIM71, and UPF1 each recruit TNRC6 to specific sets of transcripts to silence them. As cellular TNRC6 levels are limiting, competition occurs among the silencing pathways, such that the loss of AGO proteins or of AGO binding to TNRC6 enhances the activities of the other pathways. We conclude that a miRNA-like silencing activity is shared among different mRNA silencing pathways and that the use of TNRC6 as a central hub provides a means to integrate their activities.

Pathogenic variants in autism gene KATNAL2 cause hydrocephalus and disrupt neuronal connectivity by impairing ciliary microtubule dynamics.

Enlargement of the cerebrospinal fluid (CSF)-filled brain ventricles (cerebral ventriculomegaly), the cardinal feature of congenital hydrocephalus (CH), is increasingly recognized among patients with autism spectrum disorders (ASD). KATNAL2, a member of Katanin family microtubule-severing ATPases, is a known ASD risk gene, but its roles in human brain development remain unclear. Here, we show that nonsense truncation of Katnal2 (Katnal2Δ17) in mice results in classic ciliopathy phenotypes, including impaired spermatogenesis and cerebral ventriculomegaly. In both humans and mice, KATNAL2 is highly expressed in ciliated radial glia of the fetal ventricular-subventricular zone as well as in their postnatal ependymal and neuronal progeny. The ventriculomegaly observed in Katnal2Δ17 mice is associated with disrupted primary cilia and ependymal planar cell polarity that results in impaired cilia-generated CSF flow. Further, prefrontal pyramidal neurons in ventriculomegalic Katnal2Δ17 mice exhibit decreased excitatory drive and reduced high-frequency firing. Consistent with these findings in mice, we identified rare, damaging heterozygous germline variants in KATNAL2 in five unrelated patients with neurosurgically treated CH and comorbid ASD or other neurodevelopmental disorders. Mice engineered with the orthologous ASD-associated KATNAL2 F244L missense variant recapitulated the ventriculomegaly found in human patients. Together, these data suggest KATNAL2 pathogenic variants alter intraventricular CSF homeostasis and parenchymal neuronal connectivity by disrupting microtubule dynamics in fetal radial glia and their postnatal ependymal and neuronal descendants. The results identify a molecular mechanism underlying the development of ventriculomegaly in a genetic subset of patients with ASD and may explain persistence of neurodevelopmental phenotypes in some patients with CH despite neurosurgical CSF shunting.

A role for mutations in AK9 and other genes affecting ependymal cells in idiopathic normal pressure hydrocephalus.

Idiopathic normal pressure hydrocephalus (iNPH) is an enigmatic neurological disorder that develops after age 60 and is characterized by gait difficulty, dementia, and incontinence. Recently, we reported that heterozygous CWH43 deletions may cause iNPH. Here, we identify mutations affecting nine additional genes (AK9, RXFP2, PRKD1, HAVCR1, OTOG, MYO7A, NOTCH1, SPG11, and MYH13) that are statistically enriched among iNPH patients. The encoded proteins are all highly expressed in choroid plexus and ependymal cells, and most have been associated with cilia. Damaging mutations in AK9, which encodes an adenylate kinase, were detected in 9.6% of iNPH patients. Mice homozygous for an iNPH-associated AK9 mutation displayed normal cilia structure and number, but decreased cilia motility and beat frequency, communicating hydrocephalus, and balance impairment. AK9+/- mice displayed normal brain development and behavior until early adulthood, but subsequently developed communicating hydrocephalus. Together, our findings suggest that heterozygous mutations that impair ventricular epithelial function may contribute to iNPH.

A congenital hydrocephalus-causing mutation in Trim71 induces stem cell defects via inhibiting Lsd1 mRNA translation.

Congenital hydrocephalus (CH) is a major cause of childhood morbidity. Mono-allelic mutations in Trim71, a conserved stem-cell-specific RNA-binding protein, cause CH; however, the molecular basis for pathogenesis mediated by these mutations remains unknown. Here, using mouse embryonic stem cells as a model, we reveal that the mouse R783H mutation (R796H in human) alters Trim71's mRNA substrate specificity and leads to accelerated stem-cell differentiation and neural lineage commitment. Mutant Trim71, but not wild-type Trim71, binds Lsd1 (Kdm1a) mRNA and represses its translation. Specific inhibition of this repression or a slight increase of Lsd1 in the mutant cells alleviates the defects in stem cell differentiation and neural lineage commitment. These results determine a functionally relevant target of the CH-causing Trim71 mutant that can potentially be a therapeutic target and provide molecular mechanistic insights into the pathogenesis of this disease.

Biomechanical instability of the brain-CSF interface in hydrocephalus.

Hydrocephalus, characterized by progressive expansion of the CSF-filled ventricles (ventriculomegaly), is the most common reason for brain surgery. 'Communicating' (i.e. non-obstructive) hydrocephalus is classically attributed to a primary derangement in CSF homeostasis, such as choroid plexus-dependent CSF hypersecretion, impaired cilia-mediated CSF flow currents, or decreased CSF reabsorption via the arachnoid granulations or other pathways. Emerging data suggest that abnormal biomechanical properties of the brain parenchyma are an under-appreciated driver of ventriculomegaly in multiple forms of communicating hydrocephalus across the lifespan. We discuss recent evidence from human and animal studies that suggests impaired neurodevelopment in congenital hydrocephalus, neurodegeneration in elderly normal pressure hydrocephalus and, in all age groups, inflammation-related neural injury in post-infectious and post-haemorrhagic hydrocephalus, can result in loss of stiffness and viscoelasticity of the brain parenchyma. Abnormal brain biomechanics create barrier alterations at the brain-CSF interface that pathologically facilitates secondary enlargement of the ventricles, even at normal or low intracranial pressures. This 'brain-centric' paradigm has implications for the diagnosis, treatment and study of hydrocephalus from womb to tomb.

TRIM71 mutations cause a neurodevelopmental syndrome featuring ventriculomegaly and hydrocephalus.

Congenital hydrocephalus (CH), characterized by cerebral ventriculomegaly, is one of the most common reasons for pediatric brain surgery. Recent studies have implicated lin-41 (lineage variant 41)/TRIM71 (tripartite motif 71) as a candidate CH risk gene, however, TRIM71 variants have not been systematically examined in a large patient cohort or conclusively linked with an OMIM syndrome. Through cross-sectional analysis of the largest assembled cohort of patients with cerebral ventriculomegaly, including neurosurgically-treated CH (totaling 2,697 parent-proband trios and 8,091 total exomes), we identified 13 protein-altering de novo variants (DNVs) in TRIM71 in unrelated children exhibiting variable ventriculomegaly, CH, developmental delay, dysmorphic features, and other structural brain defects including corpus callosum dysgenesis and white matter hypoplasia. Eight unrelated patients were found to harbor arginine variants, including two recurrent missense DNVs, at homologous positions in RPXGV motifs of different NHL domains. Seven additional patients with rare, damaging, unphased or transmitted variants of uncertain significance were also identified. NHL-domain variants of TRIM71 exhibited impaired binding to the canonical TRIM71 target CDKN1A; other variants failed to direct the subcellular localization of TRIM71 to processing bodies. Single-cell transcriptomic analysis of human embryos revealed expression of TRIM71 in early first-trimester neural stem cells of the brain. These data show TRIM71 is essential for human brain morphogenesis and that TRIM71 mutations cause a novel neurodevelopmental syndrome featuring ventriculomegaly and CH.

The "microcephalic hydrocephalus" paradox as a paradigm of altered neural stem cell biology.

Characterized by enlarged brain ventricles, hydrocephalus is a common neurological disorder classically attributed to a primary defect in cerebrospinal fluid (CSF) homeostasis. Microcephaly ("small head") and hydrocephalus are typically viewed as two mutually exclusive phenomenon, since hydrocephalus is thought of as a fluid "plumbing" disorder leading to CSF accumulation, ventricular dilatation, and resultant macrocephaly. However, some cases of hydrocephalus can be associated with microcephaly. Recent work in the genomics of congenital hydrocephalus (CH) and an improved understanding of the tropism of certain viruses such as Zika and cytomegalovirus are beginning to shed light into the paradox "microcephalic hydrocephalus" by defining prenatal neural stem cells (NSC) as the spatiotemporal "scene of the crime." In some forms of CH and viral brain infections, impaired fetal NSC proliferation leads to decreased neurogenesis, cortical hypoplasia and impaired biomechanical interactions at the CSF-brain interface that collectively engender ventriculomegaly despite an overall and often striking decrease in head circumference. The coexistence of microcephaly and hydrocephalus suggests that these two phenotypes may overlap more than previously appreciated. Continued study of both conditions may be unexpectedly fertile ground for providing new insights into human NSC biology and our understanding of neurodevelopmental disorders.

Prdm16 is required for the maintenance of neural stem cells in the postnatal forebrain and their differentiation into ependymal cells.

We and others showed previously that PR domain-containing 16 (Prdm16) is a transcriptional regulator required for stem cell function in multiple fetal and neonatal tissues, including the nervous system. However, Prdm16 germline knockout mice died neonatally, preventing us from testing whether Prdm16 is also required for adult stem cell function. Here we demonstrate that Prdm16 is required for neural stem cell maintenance and neurogenesis in the adult lateral ventricle subventricular zone and dentate gyrus. We also discovered that Prdm16 is required for the formation of ciliated ependymal cells in the lateral ventricle. Conditional Prdm16 deletion during fetal development using Nestin-Cre prevented the formation of ependymal cells, disrupting cerebrospinal fluid flow and causing hydrocephalus. Postnatal Prdm16 deletion using Nestin-CreERT2 did not cause hydrocephalus or prevent the formation of ciliated ependymal cells but caused defects in their differentiation. Prdm16 was required in neural stem/progenitor cells for the expression of Foxj1, a transcription factor that promotes ependymal cell differentiation. These studies show that Prdm16 is required for adult neural stem cell maintenance and neurogenesis as well as the formation of ependymal cells.

Design of a Stem Cell-Based Therapy for Ependymal Repair in Hydrocephalus Associated With Germinal Matrix Hemorrhages.

BACKGROUND: In preterm birth germinal matrix hemorrhages (GMHs) and the consequent posthemorrhagic hydrocephalus (PHH), the neuroepithelium/ependyma development is disrupted. This work is aimed to explore the possibilities of ependymal repair in GMH/PHH using a combination of neural stem cells, ependymal progenitors (EpPs), and mesenchymal stem cells. METHODS: GMH/PHH was induced in 4-day-old mice using collagenase, blood, or blood serum injections. PHH severity was characterized 2 weeks later using magnetic resonance, immunofluorescence, and protein expression quantification with mass spectrometry. Ependymal restoration and wall regeneration after stem cell treatments were tested in vivo and in an ex vivo experimental approach using ventricular walls from mice developing moderate and severe GMH/PHH. The effect of the GMH environment on EpP differentiation was tested in vitro. Two-tailed Student t or Wilcoxon-Mann-Whitney U test was used to find differences between the treated and nontreated groups. ANOVA and Kruskal-Wallis tests were used to compare >2 groups with post hoc Tukey and Dunn multiple comparison tests, respectively. RESULTS: PHH severity was correlated with the extension of GMH and ependymal disruption (means, 88.22% severe versus 19.4% moderate). GMH/PHH hindered the survival rates of the transplanted neural stem cells/EpPs. New multiciliated ependymal cells could be generated from transplanted neural stem cells and more efficiently from EpPs (15% mean increase). Blood and TNFα (tumor necrosis factor alpha) negatively affected ciliogenesis in cells committed to ependyma differentiation (expressing Foxj1 [forkhead box J1] transcription factor). Pretreatment with mesenchymal stem cells improved the survival rates of EpPs and ependymal differentiation while reducing the edematous (means, 18% to 0.5% decrease in severe edema) and inflammatory conditions in the explants. The effectiveness of this therapeutical strategy was corroborated in vivo (means, 29% to 0% in severe edema). CONCLUSIONS: In GMH/PHH, the ependyma can be restored and edema decreased from either neural stem cell or EpP transplantation in vitro and in vivo. Mesenchymal stem cell pretreatment improved the success of the ependymal restoration.

Genetic blueprint of congenital muscular dystrophies with brain malformations in Egypt: A report of 11 families.

Congenital muscular dystrophies (CMDs) are a group of rare muscle disorders characterized by early onset hypotonia and motor developmental delay associated with brain malformations with or without eye anomalies in the most severe cases. In this study, we aimed to uncover the genetic basis of severe CMD in Egypt and to determine the efficacy of whole exome sequencing (WES)-based genetic diagnosis in this population. We recruited twelve individuals from eleven families with a clinical diagnosis of CMD with brain malformations that fell into two groups: seven patients with suspected dystroglycanopathy and five patients with suspected merosin-deficient CMD. WES was analyzed by variant filtering using multiple approaches including splicing and copy number variant (CNV) analysis. We identified likely pathogenic variants in FKRP in two cases and variants in POMT1, POMK, and B3GALNT2 in three individuals. All individuals with merosin-deficient CMD had truncating variants in LAMA2. Further analysis in one of the two unsolved cases showed a homozygous protein-truncating variant in Feline Leukemia Virus subgroup C Receptor 1 (FLVCR1). FLVCR1 loss of function has never been previously reported. Yet, loss of function of its paralog, FLVCR2, causes lethal hydranencephaly-hydrocephaly syndrome (Fowler Syndrome) which should be considered in the differential diagnosis for dystroglycanopathy. Overall, we reached a diagnostic rate of 86% (6/7) for dystroglycanopathies and 100% (5/5) for merosinopathy. In conclusion, our results provide further evidence that WES is an important diagnostic method in CMD in developing countries to improve the diagnostic rate, management plan, and genetic counseling for these disorders.

Disseminated Aspergillosis in X-linked Agammaglobulinemia: Beyond the norm.

X-linked agammaglobulinemia (XLA) due to a mutation in Bruton's tyrosine kinase (BTK), leads to the arrested development of B cells at the pro-B cell stage. This results in absent B cells and severe hypogammaglobulinemia. XLA patients usually present with recurrent sinopulmonary infection. Bacterial infections are the commonest [2], fungal infections like Pneumocystis jirovecii, Aspergillus and Candida species are rarely reported and they are associated with mortality in XLA [3]. We report a 3.5-year-old boy with disseminated aspergillosis, an uncommon presentation of XLA. Despite treatment with antifungals, including voriconazole and amphotericin B, the patient succumbed to the illness. Genetic analysis revealed a pathogenic variant in the BTK gene (R28H), confirming XLA diagnosis. This case highlights the potential for severe fungal infections in XLA patients and suggests broader immune system dysregulation beyond B-cell defects.

Measuring CSF shunt flow with MRI using flow enhancement of signal intensity (FENSI).

PURPOSE: To develop and validate a noninvasive imaging technique for accurately assessing very slow CSF flow within shunt tubes in pediatric patients with hydrocephalus, aiming to identify obstructions that might impede CSF drainage. THEORY AND METHODS: A simulation of shunt flow enhancement of signal intensity (shunt-FENSI) signal is used to establish the relationship between signal change and flow rate. The quantification of flow enhancement of signal intensity data involves normalization, curve fitting, and calibration to match simulated data. Additionally, a phase sweep method is introduced to accommodate the impact of magnetic field inhomogeneity on the flow measurement. The method is tested in flow phantoms, healthy adults, intensive care unit patients with external ventricular drains (EVD), and shunt patients. EVDs enable shunt-flow measurements to be acquired with a ground truth measure of CSF drainage. RESULTS: The flow-rate-to-signal simulation establishes signal-flow relationships and takes into account the T1 of draining fluid. The phase sweep method accurately accounts for phase accumulation due to frequency offsets at the shunt. Results in phantom and healthy human participants reveal reliable quantification of flow rates using controlled flows and agreement with the flow simulation. EVD patients display reliable measures of flow rates. Shunt patient results demonstrate feasibility of the method and consistent flow rates for functional shunts. CONCLUSION: The results demonstrate the technique's applicability, accuracy, and potential for diagnosing and noninvasively monitoring hydrocephalus. Limitations of the current approach include a high sensitivity to motion and strict requirement of imaging slice prescription.

Assessment of Ventricular Size and Neurocognitive Outcomes in Children with Postnatal Closure of Myelomeningocele.

OBJECTIVE: To assess if ventricular size before shunting is correlated with neurodevelopmental outcomes in children with postnatal myelomeningocele closure. STUDY DESIGN: This retrospective review included children with postnatal surgical closure of myelomeningocele and neuropsychological testing between 2018 and 2023 at the University of California, San Francisco. Frontal-occipital horn ratio (FOHR) was measured immediately before shunt placement or on the first study that reported ventricular stability for nonshunted patients. The primary outcome was full scale IQ (FSIQ) on the Weschler Intelligence Scale. Secondary outcomes included indices of the Weschler scale, the Global Executive Composite from the Behavior Rating Inventory of Executive Function, and the general adaptive composite from the Adaptive Behavior Assessment Scale. Univariable and multivariable regression was used to determine if FOHR was correlated with neuropsychological scores. RESULTS: Forty patients met the inclusion criteria; 26 (65%) had shunted hydrocephalus. Age at neuropsychological testing was 10.9 ± 0.6 years. FOHR was greater in the shunted group (0.64 vs 0.51; P < .001). There were no differences in neuropsychological results between shunted and nonshunted groups. On univariable analysis, greater FOHR was associated with lower FSIQ (P = .025) and lower Visual Spatial Index scores (P = .013), which remained significant on multivariable analysis after adjusting for gestational age at birth, lesion level, shunt status, and shunt revision status (P = .049 and P = .006, respectively). Separate analyses by shunt status revealed that these effects were driven by the shunted group. CONCLUSIONS: Greater FOHR before shunting was correlated with lower FSIQ and the Visual Spatial Index scores on the Weschler Intelligence Scales. Larger studies are needed to explore further the relationship between ventricle size, hydrocephalus, and neurodevelopmental outcomes.

CCDC88C variants are associated with focal epilepsy and genotype-phenotype correlation.

CCDC88C gene, which encodes coiled-coil domain containing 88C, is essential for cell communication during neural development. Variants in the CCDC88C caused congenital hydrocephalus, some accompanied by seizures. In patients with epilepsy without acquired etiologies, we performed whole-exome sequencing (trio-based). Two de novo and two biallelic CCDC88C variants were identified in four cases with focal (partial) epilepsy. These variants did not present or had low frequencies in the gnomAD populations and were predicted to be damaging by multiple computational algorithms. Patients with de novo variants presented with adult-onset epilepsy, whereas patients with biallelic variants displayed infant-onset epilepsy. They all responded well to anti-seizure medications and were seizure-free. Further analysis showed that de novo variants were located at crucial domains, whereas one paired biallelic variants were located outside the crucial domains, and the other paired variant had a non-classical splicing and a variant located at crucial domain, suggesting a sub-molecular effect. CCDC88C variants associated with congenital hydrocephalus were all truncated, whereas epilepsy-associated variants were mainly missense, the proportion of which was significantly higher than that of congenital hydrocephalus-associated variants. CCDC88C is potentially associated with focal epilepsy with favorable outcome. The underlying mechanisms of phenotypic variation may correlation between genotype and phenotype.

Proteomic profile and predictive markers of outcome in patients with subarachnoid hemorrhage.

BACKGROUND: The molecular mechanisms underlying development of posthemorrhagic hydrocephalus (PHH) following subarachnoid hemorrhage (SAH) remain incompletely understood. Consequently, treatment strategies tailored towards the individual patient remain limited. This study aimed to identify proteomic cerebrospinal fluid (CSF) biomarkers capable of predicting shunt dependency and functional outcome in patients with SAH in order to improve informed clinical decision making. METHODS: Ventricular CSF samples were collected twice from 23 patients with SAH who required external ventricular drain (EVD) insertion (12 patients with successful EVD weaning, 11 patients in need of permanent CSF shunting due to development of PHH). The paired CSF samples were collected acutely after ictus and later upon EVD removal. Cisternal CSF samples were collected from 10 healthy control subjects undergoing vascular clipping of an unruptured aneurysm. All CSF samples were subjected to mass spectrometry-based proteomics analysis. Proteomic biomarkers were quantified using area under the curve (AUC) estimates from a receiver operating curve (ROC). RESULTS: CSF from patients with SAH displayed a distinct proteomic profile in comparison to that of healthy control subjects. The CSF collected acutely after ictus from patients with SAH was moreover distinct from that collected weeks later but appeared similar in the weaned and shunted patient groups. Sixteen unique proteins were identified as potential predictors of shunt dependency, while three proteins were identified as potential predictors of functional outcome assessed six months after ictus with the modified Rankin Scale. CONCLUSIONS: We here identified several potential proteomic biomarkers in CSF from patients with SAH capable of predicting (i) shunt dependency and thus development of PHH and (ii) the functional outcome assessed six months after ictus. These proteomic biomarkers may have the potential to aid clinical decision making by predicting shunt dependency and functional outcome following SAH.

Congenital hydrocephalus: new Mendelian mutations and evidence for oligogenic inheritance.

BACKGROUND: Congenital hydrocephalus is characterized by ventriculomegaly, defined as a dilatation of cerebral ventricles, and thought to be due to impaired cerebrospinal fluid (CSF) homeostasis. Primary congenital hydrocephalus is a subset of cases with prenatal onset and absence of another primary cause, e.g., brain hemorrhage. Published series report a Mendelian cause in only a minority of cases. In this study, we analyzed exome data of PCH patients in search of novel causal genes and addressed the possibility of an underlying oligogenic mode of inheritance for PCH. MATERIALS AND METHODS: We sequenced the exome in 28 unrelated probands with PCH, 12 of whom from families with at least two affected siblings and 9 of whom consanguineous, thereby increasing the contribution of genetic causes. Patient exome data were first analyzed for rare (MAF < 0.005) transmitted or de novo variants. Population stratification of unrelated PCH patients and controls was determined by principle component analysis, and outliers identified using Mahalanobis distance 5% as cutoff. Patient and control exome data for genes biologically related to cilia (SYScilia database) were analyzed by mutation burden test. RESULTS: In 18% of probands, we identify a causal (pathogenic or likely pathogenic) variant of a known hydrocephalus gene, including genes for postnatal, syndromic hydrocephalus, not previously reported in isolated PCH. In a further 11%, we identify mutations in novel candidate genes. Through mutation burden tests, we demonstrate a significant burden of genetic variants in genes coding for proteins of the primary cilium in PCH patients compared to controls. CONCLUSION: Our study confirms the low contribution of Mendelian mutations in PCH and reports PCH as a phenotypic presentation of some known genes known for syndromic, postnatal hydrocephalus. Furthermore, this study identifies novel Mendelian candidate genes, and provides evidence for oligogenic inheritance implicating primary cilia in PCH.

Mediation of White Matter Alterations in the Association Between Ventricular Dilation and Cognitive Decline in Hydrocephalus Patients: An MRI Study.

BACKGROUND: Cognitive impairment is commonly observed in hydrocephalus patients. Ventricular enlargement compresses brain parenchyma, especially the white matter (WM). PURPOSE: To investigate whether the relationship between ventricular dilation and cognitive decline in hydrocephalus patients is mediated by WM alterations. STUDY TYPE: Retrospective. POPULATION: 51 communicating hydrocephalus patients (median age, 54 years), 50 obstructive hydrocephalus patients (median age, 49 years), and 53 control subjects (median age, 50 years). FIELD STRENGTH/SEQUENCE: Diffusion tensors imaging, 3D T1 BRAVO, 3D FIESTA, CUBE T2, and FLAIR sequences at 3T. ASSESSMENT: DTI parameters (skeletonized fractional anisotropy (FA), skeletonized mean diffusivity (MD), and peak width of skeletonized mean diffusivity p(PSMD)) were extracted using FSL software. Global, periventricular, and deep white matter hyperintensity (WMH) volumes, degree of ventricular enlargement (Evans index), and other conventional imaging markers (number of lacunes and perivascular spaces, intracranial and brain volume) were extracted using united imaging intelligence. Cognitive tests included Montreal cognitive assessment (MoCA), clock drawing test (CDT), and vocabulary fluency test (VFT). STATISTICAL TESTS: Multivariable linear regression analysis, mediation analyses, and dominance analysis. P-value <0.05 was considered significant. RESULTS: The degree of ventricular dilation, DTI parameters, and cognitive function scores were interrelated. The skeletonized FA values (ß = -0.0917, 95% confidence interval (CI): -0.205, -0.024) and normalized global WMH volume (ß = -0.0635, 95% CI: -0.13, -0.0005) together mediated 37.2% of the association between Evans index and MoCA. A comparable causal pathway was found for periventricular WMHs but not for deep WMHs. Dominance analysis indicated skeletonized FA values had a greater impact on cognition than WMH volume. The skeletonized FA values also mediated the association between Evans index and CDT (ß = -0.0897, 95% CI: -0.165, -0.026) and VFT (ß = -0.1589, 95% CI: -0.27, -0.083). CONCLUSION: WM alterations were causal mediators between ventricular dilation and cognitive decline in hydrocephalus patients. EVIDENCE LEVEL: 3. TECHNICAL EFFICACY: Stage 3.

The putative protein kinase Stk36 is essential for ciliogenesis and CSF flow by associating with Ulk4.

Motile cilia lining on the ependymal cells are crucial for cerebrospinal fluid (CSF) flow and its dysfunction is often associated with hydrocephalus. Unc51-like-kinase 4 (Ulk4) was previously linked to CSF flow and motile ciliogenesis in mice, as the hypomorph mutant of Ulk4 (Ulk4tm1a/tm1a ) developed hydrocephalic phenotype resulted from defective ciliogenesis and disturbed ciliary motility, while the underling mechanism is largely obscure. Here, we report that serine/threonine kinase 36 (STK36), a paralog of ULK4, directly interacts with ULK4 and this was demonstrated by yeast two-hybrid (Y2H) in yeast and coimmunoprecipitation (co-IP) assays in HEK293T cells, respectively. The interaction region was confined to their respective N-terminal kinase domain. The hypomorph mutant of Stk36 (Stk36tmE4-/- ) also developed progressive hydrocephalus postnatally and dysfunctional CSF flow, with multiple defects of motile cilia, including reduced ciliary number, disorganized ciliary orientation, defected axonemal structure and inconsistent base body (BB) orientation. Stk36tmE4-/- also disturbed the expression of Foxj1 transcription factor and a range of other ciliogenesis-related genes. All these morphological changes, motile cilia defects and transcriptional dysregulation in the Stk36tmE4-/- are practically copied from that in Ulk4tm1a/tm1a mice. Taken together, we conclude that both Stk36 and Ulk4 are crucial for CSF flow, they cooperate by direct binding with their kinase domain to regulate the Foxj1 transcription factor pathways for ciliogenesis and cilia function, not limited to CSF flow. The underlying molecular mechanism probably conserved in evolution and could be extended to other metazoans.