Myriam Srour

BACKGROUND: Familial focal epilepsy with variable foci (FFEVF) is a genetic epilepsy disorder in which affected family members experience different focal seizures. Focal cortical dysplasia (FCD) is a frequent cause of drug-resistant epilepsy in the pediatric population. Patients with focal epilepsy are less frequently referred for presurgical evaluation when FCD is not identified on MRI or when they have genetic epilepsy. The authors describe the successful surgical management of 3 drug-resistant FFEVF patients who initially had either negative or inconclusive MRI studies. OBSERVATIONS: All 3 patients carried the same germline pathogenic variant in NPRL3 , a GATOR1 complex gene. In patient 1, an ill-defined signal abnormality on MRI raised the suspicion for FCD and suggested that similar occult lesions might underlie the epilepsy of her relatives, whose scan results were initially reported as negative. Each patient was thus referred for comprehensive presurgical evaluation. Through the use of advanced neuroimaging, epileptogenic zones were identified in all 3 patients, allowing for targeted resection. At the last follow-up, all had remained seizure free for more than 5 years. LESSONS: When a genetic alteration is associated with FCD, such patients warrant imaging reexamination and exhaustive presurgical evaluation with advanced neuroimaging, as eventual lesion detection and subsequent resection can lead to long-term seizure freedom. https://thejns.org/doi/10.3171/CASE26127

The posterior fossa is a critical anatomical region housing the cerebellum and brainstem. Posterior fossa malformations are a heterogeneous group of conditions challenging to diagnose and prognosticate prenatally. Fetal magnetic resonance imaging (MRI) plays an important role in their assessment. This retrospective study examined the clinical and radiological data from 115 maternal-fetal dyads (116 fetuses) with posterior fossa malformations on fetal MRI, assessed concordance with postnatal imaging, and investigated MRI features associated with adverse outcomes. Fetal posterior fossa malformations were heterogenous: 66% (76/116) were structural and 34% (40/116) involved only CSF-containing lesions. Cerebellar hypoplasia was the most frequent posterior fossa malformation, observed in 33% (38/116). 78% (91/116) of posterior fossa malformations were “complex” (with additional central nervous system and/or extraneural anomalies). Concordance between fetal MRI and postnatal imaging was 51% (27/53), which improved to 69% (20/29) when CSF-containing lesions were excluded. Among terminated pregnancies who underwent autopsy, the fetal MRI diagnosis was confirmed in 75% (12/16). Chiari-II malformations, pontocerebellar hypoplasia and cerebellar asymmetry were consistently confirmed on postnatal imaging. Four fetuses with cerebellar hypoplasia had normal postnatal imaging. Structural and “complex” posterior fossa malformations were more likely to have poor pregnancy outcomes (i.e., termination, fetal demise, or neonatal death) than CSF-only and isolated anomalies. Genetic testing was positive in 24% (19/80) of tested cases, and 16% (19/116) of the overall cohort. Fetal MRI has an important role in the accurate diagnosis and management of posterior fossa malformations, particularly for structural anomalies which are associated with poor pregnancy outcomes.

Background: Congenital Mirror Movement Syndrome (CMMS) involves involuntary movements on one side of the body while voluntary movements are performed on the other side. They disrupt left–right coordination and can be caused by a pathogenic variant in the DCC gene. CMMS have been extensively studied in the upper limb, but its impact on lower limb during gait in humans is unclear. Objectives: Determine the impact of CMMS on locomotor patterns in individuals with a DCC pathogenic variant. Methods: The gait pattern of seven individuals with a DCC pathogenic variant and ten healthy controls was assessed using 3D motion capture (kinematics), electromyographic recordings (EMG) of the soleus (SOL) and tibialis anterior (TA) muscles and foot pressure distribution during comfortable walking, fast walking, and running. Results: In comparison to controls, the DCC group exhibited prolonged soleus (SOL) EMG activity and overlapping left–right SOL activation at a comfortable walking speed. No change was noted in TA. Both groups demonstrated increased pressure at the toe during the push‐off phase; however, individuals with the most severe CMMS also displayed an early stance‐phase pressure peak, reflecting contralateral push‐off. These features diminished at higher walking speeds. Kinematic analysis revealed delayed knee flexion and prolonged double‐limb support in the DCC group. Group differences were more pronounced when comparing control participants to DCC individuals with observable CMMS (Wood and Tauber scale). Conclusions: DCC variants impair left–right coordination, particularly affecting distal extensor muscle timing during gait. These disruptions are most evident during slow walking and correlate with mirror movement severity.

The axon guidance cue netrin-1 signals through its receptor DCC (deleted in colorectal cancer) to attract commissural axons to the midline. Variants in DCC are frequently associated with congenital mirror movements (CMMs). A CMM-associated variant in the cytoplasmic tail of DCC is located in a conserved motif predicted to bind to a regulator of actin dynamics called the WAVE (Wiskott-Aldrich syndrome protein–family verprolin homologous protein) regulatory complex (WRC). Here, we explored how this variant affects DCC function and may contribute to CMM. We found that a conserved WRC-interacting receptor sequence (WIRS) motif in the cytoplasmic tail of DCC mediated the interaction between DCC and the WRC. This interaction was required for netrin-1–mediated axon guidance in cultured rodent commissural neurons. Furthermore, the WIRS motif of Fra, the Drosophila DCC ortholog, was required for attractive signaling in vivo at the Drosophila midline. The CMM-associated R1343H variant of DCC, which altered the WIRS motif, prevented the DCC-WRC interaction and impaired axon guidance in cultured commissural neurons and in Drosophila . The findings reveal the WRC as a pivotal component of netrin-1–DCC signaling and uncover a molecular mechanism explaining how a human genetic variant in the cytoplasmic tail of DCC may lead to CMM.

Fibrinogen is a blood-derived protein involved in coagulation, and can make its way into the central nervous system (CNS) following breakdown of the blood-brain barrier. This molecule has been implicated in multiple sclerosis (MS), a disease marked by inflammation and demyelination in the CNS, as well as other neurological disorders. However, the effect of this molecule has not been studied on human myelinating cells. This study examines how fibrinogen influences human oligodendrocyte (OL) lineage cells at various stages of development. Using induced pluripotent stem cell-derived (iPSC) OL precursors and human primary OLs, we examined the effects of fibrinogen on cell differentiation, viability and myelination-related function. Here we show that fibrinogen induces an aberrant differentiation of early lineage OLs, by inhibiting their maturation and inducing an astrocytic phenotype, as seen in previous studies. On mature OLs, fibrinogen was found to promote myelination capacity as shown by ensheathment assays as well as on the RNA level. These effects were associated with the activation of BMP signalling, both in early and mature OLs. Transcriptomic analysis of human MS brain tissue shows similar pro-myelination changes in a subset of OLs, suggesting in vivo relevance. These findings indicate that fibrinogen has a lineage-dependent effect, where it may be inhibitory earlier in the lineage while promoting OL function in later stages. Understanding this dual role will provide insight into remyelination failure in MS and highlights the importance of timing and target in future therapeutic strategies. Significance Statement: In multiple sclerosis (MS), the blood protein fibrinogen leaks into the brain and has been shown to interfere with myelin repair. This study demonstrates that fibrinogen has opposite effects on human oligodendrocyte-lineage cells depending on their stage of maturation. While it blocks the differentiation of early-stage cells, it enhances the functional capacity of mature oligodendrocytes. These findings help explain why remyelination may fail in MS and suggest that fibrinogen could both hinder and support repair, depending on the cell context. This dual role has important implications for developing stage-specific therapies for MS.

Background: Congenital mirror movements (CMM) is a rare neurodevelopmental disorder characterized by involuntary movements from one side of the body that mirror voluntary movements on the opposite side. To date, five genes have been associated with CMM, namely DCC, RAD51, NTN1, ARHGEF7, and DNAL4.Objective: The aim of this study is to characterize the genetic landscape of CMM in a large group of 80 affected individuals.Methods: We screened 80 individuals with CMM from 43 families for pathogenic variants in CMM genes. In large CMM families, we tested for presence of pathogenic variants in multiple affected and unaffected individuals. In addition, we evaluated the impact of three missense DCC variants on binding between DCC and Netrin‐1 in vitro.Results: Causal pathogenic/likely pathogenic variants were found in 35% of probands overall, and 70% with familial CMM. The most common causal gene was DCC, responsible for 28% of CMM probands and 80% of solved cases. RAD51, NTN1, and ARHGEF7 were rare causes of CMM, responsible for 2% each. Penetrance of CMM in DCC pathogenic variant carriers was 68% and higher in males than females (74% vs. 54%). The three tested missense variants (p.Ile164Thr; p.Asn176Ser; and p.Arg1343His) bind Netrin‐1 similarly to wild type DCC.Conclusions: A genetic etiology can be identified in one third of CMM individuals, with DCC being the most common gene involved. Two thirds of CMM individuals were unsolved, highlighting that CMM is genetically heterogeneous and other CMM genes are yet to be discovered. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Background and Objectives Somatic and germline pathogenic variants in genes of the mammalian target of rapamycin (mTOR) signaling pathway are a common mechanism underlying a subset of focal malformations of cortical development (FMCDs) referred to as mTORopathies, which include focal cortical dysplasia (FCD) type II, subtypes of polymicrogyria, and hemimegalencephaly. Our objective is to screen resected FMCD specimens with mTORopathy features on histology for causal somatic variants in mTOR pathway genes, describe novel pathogenic variants, and examine the variant distribution in relation to neuroimaging, histopathologic classification, and clinical outcomes. Methods We performed ultra-deep sequencing using a custom HaloPlex^HS Target Enrichment kit in DNA from 21 resected fresh-frozen histologically confirmed FCD type II, tuberous sclerosis complex, or hemimegalencephaly specimens. We mapped the variant alternative allele frequency (AAF) across the resected brain using targeted ultra-deep sequencing in multiple formalin-fixed paraffin-embedded tissue blocks. We also functionally validated 2 candidate somatic MTOR variants and performed targeted RNA sequencing to validate a splicing defect associated with a novel DEPDC5 variant. Results We identified causal mTOR pathway gene variants in 66.7% (14/21) of patients, of which 13 were somatic with AAF ranging between 0.6% and 12.0%. Moreover, the AAF did not predict balloon cell presence. Favorable seizure outcomes were associated with genetically clear resection borders. Individuals in whom a causal somatic variant was undetected had excellent postsurgical outcomes. In addition, we demonstrate pathogenicity of the novel c.4373_4375dupATG and candidate c.7499T>A MTOR variants in vitro. We also identified a novel germline aberrant splice site variant in DEPDC5 (c.2802-1G>C). Discussion The AAF of somatic pathogenic variants correlated with the topographic distribution, histopathology, and postsurgical outcomes. Moreover, cortical regions with absent histologic FCD features had negligible or undetectable pathogenic variant loads. By contrast, specimens with frank histologic abnormalities had detectable pathogenic variant loads, which raises important questions as to whether there is a tolerable variant threshold and whether surgical margins should be clean, as performed in tumor resections. In addition, we describe 2 novel pathogenic variants, expanding the mTORopathy genetic spectrum. Although most pathogenic somatic variants are located at mutation hotspots, screening the full-coding gene sequence remains necessary in a subset of patients.

Oligodendrocyte (OL) injury and loss are central features of evolving lesions in multiple sclerosis. Potential causative mechanisms of OL loss include metabolic stress within the lesion microenvironment. Here we use the injury response of primary human OLs (hOLs) to metabolic stress (reduced glucose/nutrients) in vitro to help define the basis for the in situ features of OLs in cases of MS. Under metabolic stress in vitro, we detected reduction in ATP levels per cell that precede changes in survival. Autophagy was initially activated, although ATP levels were not altered by inhibitors (chloroquine) or activators (Torin-1). Prolonged stress resulted in autophagy failure, documented by non-fusion of autophagosomes and lysosomes. Consistent with our in vitro results, we detected higher expression of LC3, a marker of autophagosomes in OLs, in MS lesions compared to controls. Both in vitro and in situ, we observe a reduction in nuclear size of remaining OLs. Prolonged stress resulted in increased ROS and cleavage of spectrin, a target of Ca²⁺-dependent proteases. Cell death was however not prevented by inhibitors of ferroptosis or MPT-driven necrosis, the regulated cell death (RCD) pathways most likely to be activated by metabolic stress. hOLs have decreased expression of VDAC1, VDAC2, and of genes regulating iron accumulation and cyclophilin. RNA sequencing analyses did not identify activation of these RCD pathways in vitro or in MS cases. We conclude that this distinct response of hOLs, including resistance to RCD, reflects the combined impact of autophagy failure, increased ROS, and calcium influx, resulting in metabolic collapse and degeneration of cellular structural integrity. Defining the basis of OL injury and death provides guidance for development of neuro-protective strategies.

Heterozygous pathogenic variants in PPP2R5D gene are associated with PPP2R5D-related neurodevelopmental disorder, a rare autosomal dominant condition, characterized by neurodevelopmental impairment in childhood, macrocephaly/megalencephaly, hypotonia, epilepsy, and dysmorphic features. Up-to-date, only approximately 100 cases have been published in the literature and the full phenotypic and genotypic spectrum have not yet been fully described. PPP2R5D gene encodes the B56 delta subunit of the PP2A enzyme complex. We describe a neonatal form of PPP2R5D-related disorder with early infantile death, caused by a novel in-frame deletion causing loss of 8 amino acids and insertion of serine at position 201 (p.Phe194_Pro201delinsSer) of the B56 delta subunit. This deletion is predicted to disrupt a critical acidic loop of amino acids important for binding other subunits of the PP2A enzyme complex, and harbors many of the residues previously reported to cause a mild-moderate form of this condition. This report describes a neonatal lethal presentation of the PPP2R5D-related neurodevelopmental disorder and provides additional evidence that disruption of the acidic loop is an important pathomechanism underlying PPP2R5D-related disorder.

Mirror movements (MM) disorder is characterized by involuntary movements on one side of the body that mirror intentional movements on the opposite side. We performed genetic characterization of a family with autosomal dominant MM and identified ARHGEF7 , a RhoGEF, as a candidate MM gene. We found that Arhgef7 and its partner Git1 bind directly to Dcc. Dcc is the receptor for Netrin-1, an axon guidance cue that attracts commissural axons to the midline, promoting the midline crossing of axon tracts. We show that Arhgef7 and Git1 are required for Netrin-1–mediated axon guidance and act as a multifunctional effector complex. Arhgef7/Git1 activates Rac1 and Cdc42 and inhibits Arf1 downstream of Netrin-1. Furthermore, Arhgef7/Git1, via Arf1, mediates the Netrin-1–induced increase in cell surface Dcc. Mice heterozygous for Arhgef7 have defects in commissural axon trajectories and increased symmetrical paw placements during skilled walking, a MM-like phenotype. Thus, we have delineated how ARHGEF7 mutation causes MM.