The genetic and phenotypic spectra of adult genetic leukoencephalopathies in a cohort of 309 patients

Terra incognita of glial cell dynamics in the etiology of leukodystrophies: Broadening disease and therapeutic perspectives

Neuroglial cells, also known as glia, are primarily characterized as auxiliary cells within the central nervous system (CNS). The recent findings have shed light on their significance in numerous physiological processes and their involvement in various neurological disorders. Leukodystrophies encompass an array of rare and hereditary neurodegenerative conditions that were initially characterized by the deficiency, aberration, or degradation of myelin sheath within CNS. The primary cellular populations that experience significant alterations are astrocytes, oligodendrocytes and microglia. These glial cells are either structurally or metabolically impaired due to inherent cellular dysfunction. Alternatively, they may fall victim to the accumulation of harmful by-products resulting from metabolic disturbances. In either situation, the possible replacement of glial cells through the utilization of implanted tissue or stem cell-derived human neural or glial progenitor cells hold great promise as a therapeutic strategy for both the restoration of structural integrity through remyelination and the amelioration of metabolic deficiencies. Various emerging treatment strategies like stem cell therapy, ex-vivo gene therapy, infusion of adeno-associated virus vectors, emerging RNA-based therapies as well as long-term therapies have demonstrated success in pre-clinical studies and show promise for rapid clinical translation. Here, we addressed various leukodystrophies in a comprehensive and detailed manner as well as provide prospective therapeutic interventions that are being considered for clinical trials. Further, we aim to emphasize the crucial role of different glial cells in the pathogenesis of leukodystrophies. By doing so, we hope to advance our understanding of the disease, elucidate underlying mechanisms, and facilitate the development of potential treatment interventions.

The impact of immunity on the risk of coronary artery disease: insights from a multiomics study

BACKGROUND

Immune inflammation is intricately associated with coronary artery disease (CAD) progression, necessitating the pursuit of more efficacious therapeutic strategies. This study aimed to uncover potential therapeutic targets for CAD and myocardial infarction (MI) by elucidating the causal connection between regulatory immune-related genes (RIRGs) and these disorders.

METHODOLOGY

We performed summary data-based Mendelian randomization analysis to assess the therapeutic targets linked to expression quantitative trait loci and methylation quantitative trait loci of RIRGs in relation to CAD and MI. Independent validation cohorts and datasets from coronary artery and left ventricular heart tissue were analyzed. To strengthen causal inference, colocalization analysis and PhenoScanner phenotype scans were employed.

RESULTS

Utilizing multiomics integration, we pinpointed EIF2B2, FCHO1, and DDT as CAD risk genes. Notably, EIF2B2 and FCHO1 displayed significant associations with MI. High EIF2B2 expression, regulated by cg16144293, heightened CAD and MI risk at rs175438. In contrast, enhanced FCHO1 expression, modulated by cg18329931, reduced CAD and MI risk at rs13382133. DDT upregulation influenced by cg11060661 and cg09664220 was associated with decreased CAD risk at rs5760120. Colocalization analysis firmly established these relationships.

CONCLUSION

EIF2B2, FCHO1, and DDT represent risk loci for CAD progression within RIRGs. Our identification of these genes enhances understanding of CAD pathogenesis and directs future drug development efforts.

Rare Sequence Variation Underlying Suspected Familial Cerebral Small-Vessel Disease

BACKGROUND

Cerebral small-vessel disease (cSVD) is the leading monogenic cause of stroke. Despite genetic screening in routine diagnosis, many cases remain without a known causative variant. Using a cohort with suspected familial cSVD and whole-genome sequencing, we screened for variants in genes associated with monogenic cSVD and searched for novel variants associated with the disease.

METHODS AND RESULTS

Rare variants were identified in whole-genome sequencing data from the NBR (National Institute for Health Research BioResource Rare Disease) study. Pathogenic variants in known monogenic cSVD genes were identified. Gene-based burden tests and family analysis were performed to identify novel variants associated with familial cSVD. A total of 257 suspected cSVD cases (mean ± SD age, 56.2 ± 16.1 years), and 13 086 controls with other nonstroke diseases (5874 [44.9%] men) were studied. A total of 8.9% of the cases carried a variant in known cSVD genes. Excluding these known causes, 23.6% of unrelated subjects with cSVD carried predicted deleterious variants in the Genomics England gene panel, but no association was found with cSVD in burden tests. We identified potential associations with cSVD in noncoding genes, including RP4-568F9.3 (adjusted P = 7.1 × 10-25), RP3-466I7.1 (adjusted P = 8.9 × 10-16), and ZNF209P (adjusted P = 1.0 × 10-15), and matrisomal genes (adjusted P = 5.1 × 10-6), including FAM20C, INHA, LAMC1, and VWA5B2.

CONCLUSIONS

Predicted deleterious variants in known cSVD genes were present in 23.6% of unrelated cases with cSVD, but none of the genes were associated with the disease. Rare variants in noncoding and matrisomal genes could potentially contribute to cSVD development. These genes could play a role in tissue development and brain endothelial cell function. However, further studies are needed to confirm their pathophysiological roles.

Prevalence and Characterization of NOTCH2NLC GGC Repeat Expansions in Koreans: From a Hospital Cohort Analysis to a Population-Wide Study

Background and Objectives

GGC repeat expansions in the NOTCH2NLC gene are associated with a broad spectrum of progressive neurologic disorders, notably, neuronal intranuclear inclusion disease (NIID). We aimed to investigate the population-wide prevalence and clinical manifestations of NOTCH2NLC-related disorders in Koreans.

Methods

We conducted a study using 2 different cohorts from the Korean population. Patients with available brain MRI scans from Seoul National University Hospital (SNUH) were thoroughly reviewed, and NIID-suspected patients presenting the zigzag edging signs underwent genetic evaluation for NOTCH2NLC repeats by Cas9-mediated nanopore sequencing. In addition, we analyzed whole-genome sequencing data from 3,887 individuals in the Korea Biobank cohort to estimate the distribution of the repeat counts in Koreans and to identify putative patients with expanded alleles and neurologic phenotypes.

Results

In the SNUH cohort, among 90 adult-onset leukoencephalopathy patients with unknown etiologies, we found 20 patients with zigzag edging signs. Except for 2 diagnosed with fragile X-associated tremor/ataxia syndrome and 2 with unavailable samples, all 16 patients (17.8%) were diagnosed with NIID (repeat range: 87-217). By analyzing the Korea Biobank cohort, we estimated the distribution of repeat counts and threshold (>64) for Koreans, identifying 6 potential patients with NIID. Furthermore, long-read sequencing enabled the elucidation of transmission and epigenetic patterns of NOTCH2NLC repeats within a family affected by pediatric-onset NIID.

Discussion

This study presents the population-wide distribution of NOTCH2NLC repeats and the estimated prevalence of NIID in Koreans, providing valuable insights into the association between repeat counts and disease manifestations in diverse neurologic disorders.

Pathophysiology of cerebral small vessel disease: a journey through recent discoveries

Cerebral small vessel disease (cSVD) encompasses a heterogeneous group of age-related small vessel pathologies that affect multiple regions. Disease manifestations range from lesions incidentally detected on neuroimaging (white matter hyperintensities, small deep infarcts, microbleeds, or enlarged perivascular spaces) to severe disability and cognitive impairment. cSVD accounts for approximately 25% of ischemic strokes and the vast majority of spontaneous intracerebral hemorrhage and is also the most important vascular contributor to dementia. Despite its high prevalence and potentially long therapeutic window, there are still no mechanism-based treatments. Here, we provide an overview of the recent advances in this field. We summarize recent data highlighting the remarkable continuum between monogenic and multifactorial cSVDs involving NOTCH3, HTRA1, and COL4A1/A2 genes. Taking a vessel-centric view, we discuss possible cause-and-effect relationships between risk factors, structural and functional vessel changes, and disease manifestations, underscoring some major knowledge gaps. Although endothelial dysfunction is rightly considered a central feature of cSVD, the contributions of smooth muscle cells, pericytes, and other perivascular cells warrant continued investigation.

The Phenotypic and Genotypic Spectrum of CSF1R-Related Disorder in China

BACKGROUND

Colony-stimulating factor 1 receptor (CSF1R)-related disorder (CRD) is a rare autosomal dominant disease. The clinical and genetic characteristics of Chinese patients have not been elucidated.

OBJECTIVE

The objective of the study is to clarify the core features and influence factors of CRD patients in China.

METHODS

Clinical and genetic-related data of CRD patients in China were collected. Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and Sundal MRI Severity Score were evaluated. Whole exome sequencing was used to analyze the CSF1R mutation status. Patients were compared between different sexes, mutation types, or mutation locations.

RESULTS

A total of 103 patients were included, with a male-to-female ratio of 1:1.51. The average age of onset was (40.75 ± 8.58). Cognitive impairment (85.1%, 86/101) and parkinsonism (76.2%, 77/101) were the main clinical symptoms. The most common imaging feature was bilateral asymmetric white matter changes (100.0%). A total of 66 CSF1R gene mutants (22 novel mutations) were found, and 15 of 92 probands carried c.2381 T > C/p.I794T (16.30%). The MMSE and MoCA scores (17.0 [9.0], 11.90 ± 7.16) of female patients were significantly lower than those of male patients (23.0 [10.0], 16.36 ± 7.89), and the white matter severity score (20.19 ± 8.47) of female patients was significantly higher than that of male patients (16.00 ± 7.62). There is no statistical difference in age of onset between male and female patients.

CONCLUSIONS

The core manifestations of Chinese CRD patients are progressive cognitive decline, parkinsonism, and bilateral asymmetric white matter changes. Compared to men, women have more severe cognitive impairment and imaging changes. c.2381 T > C/p.I794T is a hotspot mutation in Chinese patients. © 2024 International Parkinson and Movement Disorder Society.

Neuronal Intranuclear Inclusion Disease with NOTCH2NLC GGC Repeat Expansion: A Systematic Review and Challenges of Phenotypic Characterization

Neuronal intranuclear inclusion disease (NIID) is a highly clinically heterogeneous neurodegenerative disorder primarily attributed to abnormal GGC repeat expansions in the NOTCH2NLC gene. This study aims to comprehensively explore its phenotypic characteristics and genotype-phenotype correlation. A literature search was conducted in PubMed, Embase, and the Cochrane Library from September 1, 2019, to December 31, 2022, encompassing reported NIID cases confirmed by pathogenic NOTCH2NLC mutations. Linear regressions and trend analyses were performed. Analyzing 635 cases from 85 included studies revealed that familial cases exhibited significantly larger GGC repeat expansions than sporadic cases (p < 0.001), and this frequency significantly increased with expanding GGC repeats (p trend < 0.001). Age at onset (AAO) showed a negative correlation with GGC repeat expansions (p < 0.001). The predominant initial symptoms included tremor (31.70%), cognitive impairment (14.12%), and muscle weakness (10.66%). The decreased or absent tendon reflex (DTR/ATR) emerged as a notable clinical indicator of NIID due to its high prevalence. U-fiber was observed in 79.11% of patients, particularly prominent in paroxysmal disease-dominant (87.50%) and dementia-dominant cases (81.08%). Peripheral neuropathy-dominant cases exhibited larger GGC repeat expansions (median = 123.00) and an earlier AAO (median = 33.00) than other phenotypes. Moreover, a significant genetic anticipation of 3.5 years was observed (p = 0.039). This study provides a comprehensive and up-to-date compilation of genotypic and phenotypic information on NIID since the identification of the causative gene NOTCH2NLC. We contribute a novel diagnostic framework for NIID to support clinical practice.

Case report: Neuronal intranuclear inclusion disease initially mimicking reversible cerebral vasoconstriction syndrome: serial neuroimaging findings during an 11-year follow-up

Neuronal intranuclear inclusion disease (NIID) is a rare, progressive neurodegenerative disorder known for its diverse clinical manifestations. Although episodic neurogenic events can be associated with NIID, no reported cases have demonstrated concurrent clinical features or MRI findings resembling reversible cerebral vasoconstriction syndrome (RCVS). Here, we present the inaugural case of an adult-onset NIID patient who initially displayed symptoms reminiscent of RCVS. The 59-year-old male patient's initial presentation included a thunderclap headache, right visual field deficit, and confusion. Although his brain MRI appeared normal, MR angiography unveiled left posterior cerebral artery occlusion, subsequently followed by recanalization, culminating in an RCVS diagnosis. Over an 11-year period, the patient encountered 10 additional episodes, each escalating in duration and intensity, accompanied by seizures. Simultaneously, cognitive impairment progressed. Genetic testing for NIID revealed an abnormal expansion of GGC repeats in NOTCH2NLC, with a count of 115 (normal range, <60), and this patient was diagnosed with NIID. Our report highlights that NIID can clinically and radiologically mimic RCVS. Therefore, in the differential diagnosis of RCVS, particularly in cases with atypical features or recurrent episodes, consideration of NIID is warranted. Additionally, the longitudinal neuroimaging findings provided the course of NIID over an 11-year follow-up period.

Missense Variants in COL4A1/2 Are Associated with Cerebral Aneurysms: A Case Report and Literature Review

BACKGROUND

Although cerebral aneurysm (CA) is a defining complication of COL4A1/2-related vasculopathy, the specific factors influencing its onset remain uncertain. This study aimed to identify and analyze these factors.

METHODS

We described a family presenting with a novel variant of the COL4A1 gene complicated with CA. Concurrently, an exhaustive review of previously documented patients with COL4A1/2-related vasculopathy was conducted by sourcing data from PubMed, Web of Science, Google Scholar, and Ichushi databases. We compared the variant types and locations between patients with CA (positive group) and those without CA (negative group).

RESULTS

This study included 53 COL4A1/2 variants from 76 patients. Except for one start codon variant, all the identified variants in CA were missense variants. Otherwise, CA was not associated with other clinical manifestations, such as small-vessel disease or other large-vessel abnormalities. A higher frequency of missense variants (95.5% vs. 58.1%, p = 0.0035) was identified in the CA-positive group.

CONCLUSIONS

CA development appears to necessitate qualitative alterations in COL4A1/2, and the underlying mechanism seems independent of small-vessel disease or other large-vessel anomalies. Our findings suggest that a meticulous evaluation of CA is necessary when missense variants in COL4A1/2 are identified.

Adult-onset leukodystrophies: a practical guide, recent treatment updates, and future directions

Adult-onset leukodystrophies though individually rare are not uncommon. This group includes several disorders with isolated adult presentations, as well as several childhood leukodystrophies with attenuated phenotypes that present at a later age. Misdiagnoses often occur due to the clinical and radiological overlap with common acquired disorders such as infectious, immune, inflammatory, vascular, metabolic, and toxic etiologies. Increased prevalence of non-specific white matter changes in adult population poses challenges during diagnostic considerations. Clinico-radiological spectrum and molecular landscape of adult-onset leukodystrophies have not been completely elucidated at this time. Diagnostic approach is less well-standardized when compared to the childhood counterpart. Absence of family history and reduced penetrance in certain disorders frequently create a dilemma. Comprehensive evaluation and molecular confirmation when available helps in prognostication, early initiation of treatment in certain disorders, enrollment in clinical trials, and provides valuable information for the family for reproductive counseling. In this review article, we aimed to formulate an approach to adult-onset leukodystrophies that will be useful in routine practice, discuss common adult-onset leukodystrophies with usual and unusual presentations, neuroimaging findings, recent advances in treatment, acquired mimics, and provide an algorithm for comprehensive clinical, radiological, and genetic evaluation that will facilitate early diagnosis and consider active treatment options when available. A high index of suspicion, awareness of the clinico-radiological presentations, and comprehensive genetic evaluation are paramount because treatment options are available for several disorders when diagnosed early in the disease course.

Case report: Neuronal intranuclear inclusion disease presenting with acute encephalopathy

Neuronal intranuclear inclusion disease (NIID), a neurodegenerative disease previously thought to be rare, is increasingly recognized despite heterogeneous clinical presentations. NIID is pathologically characterized by ubiquitin and p-62 positive intranuclear eosinophilic inclusions that affect multiple organ systems, including the brain, skin, and other tissues. Although the diagnosis of NIID is challenging due to phenotypic heterogeneity, a greater understanding of the clinical and imaging presentations can improve accurate and early diagnosis. Here, we present three cases of pathologically proven adult-onset NIID, all presenting with episodes of acute encephalopathy with protracted workups and lengthy time between symptom onset and diagnosis. Case 1 highlights challenges in the diagnosis of NIID when MRI does not reveal classic abnormalities and provides a striking example of hyperperfusion in the setting of acute encephalopathy, as well as unique pathology with neuronal central chromatolysis, which has not been previously described. Case 2 highlights the progression of MRI findings associated with multiple NIID-related encephalopathic episodes over an extended time period, as well as the utility of skin biopsy for antemortem diagnosis.

NOTCH2NLC GGC repeats are not expanded in Italian amyotrophic lateral sclerosis patients

Repeat expansions in genes other than C9orf72 and ATXN2 have been recently associated with Amyotrophic Lateral Sclerosis (ALS). Indeed, an abnormal number of GGC repeats in NOTCH2NLC has been recently reported in 0.7% of sporadic ALS patients from mainland China. This finding was not confirmed in an ALS cohort of subjects from Taiwan. As the involvement of expanded NOTCH2NLC alleles in ALS is debated, we addressed this point by evaluating NOTCH2NLC repeat expansions in an Italian cohort of ALS patients. A screening analysis of NOTCH2NLC GGC repeats was performed by repeat-primed polymerase chain reaction (RP-PCR) in a cohort of 385 probable/definite ALS Italian patients. Mean age at onset was 60.5 years (SD 13.7), and 60.9% were males. Sporadic cases were 357 (92.7%), and most patients had a spinal onset (71.8%). None of our patients showed the typical sawtooth tail pattern on RP-PCR, thus excluding abnormal repeat expansion in NOTCH2NLC. Overall, we suggest that NOTCH2NLC expanded alleles might be absent or at least extremely rare in ALS Italian patients. Further investigations in larger cohorts with different ethnic backgrounds are required to support the involvement of NOTCH2NLC in ALS.