Pearls & Oy-sters: AARS2 Leukodystrophy-Tremor and Tribulations.

A 35-year-old woman with a progressive, bilateral upper limb tremor, personality change, behavioral disturbance, and primary ovarian insufficiency was found to have AARS2-related leukodystrophy. She had congenital nystagmus which evolved to head titubation by age 8 years and then developed an upper limb tremor in her mid-teens. These symptoms stabilized during her 20s, but soon after this presentation at age 35 years, neurologic and behavioral disturbances progressed rapidly over a 12-month period requiring transition to an assisted living facility with care support (4 visits/day) and assistance for all activities of daily living. MRI of the brain demonstrated confluent white matter changes predominantly involving the frontal lobes consistent with a leukodystrophy. All other investigations were unremarkable. Nongenetic causes of a leukodystrophy including sexually transmitted diseases and recreational drug use were excluded. Family history was negative for similar symptoms. Gene panel testing identified compound heterozygous pathogenic AARS2 mutations. This case highlights the importance of MRI brain imaging in progressive tremor syndromes, the utility of gene panels in simultaneous testing of multiple disorders with overlapping phenotypes, and the need for awareness of comorbid endocrinological disorders in many of the genetic leukodystrophies, whose identification may aid in clinical diagnosis.

NOTCH1-Related Leukoencephalopathy: A Novel Variant and Literature Review.

NOTCH1-related leukoencephalopathy is a new diagnostic entity linked to heterozygous gain-of-function variants in NOTCH1 that neuroradiologically show some overlap with the inflammatory microangiopathy Aicardi-Goutières syndrome (AGS). To report a 16-year-old boy harbouring a novel NOTCH1 mutation who presented neuroradiological features suggestive of enhanced type I interferon signalling. We describe five years of follow-up and review the current literature on NOTCH1-related leukoencephalopathy. Clinical evaluation, standardised scales (SPRS, SARA, CBCL, CDI-2:P, WISCH-IV and VABS-2) and neuroradiological studies were performed, as well as blood DNA analysis. For the literature review, a search was performed on Pubmed, Scopus and Web of Science up to December 2023 using the following text word search strategy: (NOTCH1) AND (leukoencephalopathy). Our patient presents clinical features consistent with other reported cases with NOTCH1 mutations but is among the minority of patients with an onset after infancy. During the five-year follow-up, we observed an increase in the severity of spasticity and ataxia. However, at the age of 16 years, our proband is still ambulatory. As for other reported patients, he manifests psychiatric features ranging from hyperactivity during childhood to anxiety and depression during adolescence. The neuroradiological picture remained essentially stable over five years. In addition to the typical findings of leukoencephalopathy with cysts and calcifications already described, we report the presence of T2-hyperintensity and T1-hypotensity of the transverse pontine fibres, enhancement in the periventricular white matter after gadolinium administration and decreased NAA and Cho peaks in the periventricular white matter on MRS. We identified a novel heterozygous variant in NOTCH1 (c.4788_4799dup), a frame insertion located in extracellular negative regulatory region (NRR)-domain as in previously published cases. Blood interferon signalling was not elevated compared to controls. This case provides further data on a new diagnostic entity, i.e., NOTCH1-related leukoencephalopathy. By describing a standardised five-year follow-up in one case and reviewing the other patients described to date, we outline recommendations relating to monitoring in this illness, emphasising the importance of psychiatric and gastroenterological surveillance alongside neurological and neuropsychological management. Studies are needed to better understand the factors influencing disease onset and severity, which are heterogeneous.

GDF15 is a dynamic biomarker of the integrated stress response in the central nervous system.

AIM: Characterize Growth Differentiation Factor 15 (GDF15) as a secreted biomarker of the integrated stress response (ISR) within the central nervous system (CNS). METHODS: We determined GDF15 levels utilizing in vitro and in vivo neuronal systems wherein the ISR was activated. Primarily, we used the murine model of vanishing white matter disease (VWMD), a neurological disease driven by persistent ISR in the CNS, to establish a link between levels of GDF15 in the cerebrospinal fluid (CSF) and ISR gene expression signature in the CNS. GDF15 was also determined in the CSF of VWM patients. RESULTS: GDF15 expression was increased concomitant to ISR activation in stress-induced primary astrocytes as well as in retinal ganglion cells following optic nerve crush, while treatment with 2Bact, a specific eIF2B activator, suppressed both the ISR and GDF15. In the VWMD model, CSF GDF15 levels corresponded with the magnitude of the ISR and were reduced by 2BAct. In VWM patients, mean CSF GDF15 was elevated >20-fold as compared to healthy controls, whereas plasma GDF15 was undifferentiated. CONCLUSIONS: These data suggest that CSF GDF15 is a dynamic marker of ISR activation in the CNS and may serve as a pharmacodynamic biomarker for ISR-modulating therapies.

[Debut and evolution MRI images of a child with a new genetic variant of vanishing white matter leukodystrophy]. / Imágenes de resonancia magnética de inicio y evolución de un niño con nueva variante genética de leucodistrofia evanescente.

TITLE: Imágenes de resonancia magnética de inicio y evolución de un niño con nueva variante genética de leucodistrofia evanescente.

Etiologic Spectrum of Pediatric-Onset Leukodystrophies and Genetic Leukoencephalopathies: The Five-Year Experience of a Tertiary Care Center in Southern India.

BACKGROUND: White matter (WM) disorders with a genetic etiology are classified as leukodystrophies (LDs) and genetic leukoencephalopathies (GLEs). There are very few studies pertaining to the etiologic spectrum of these disorders in the Asian Indian population. METHODS: This study was conducted over a period of five years from January 2016 to December 2020, in the medical genetics department of a tertiary care hospital in southern India. A total of 107 patients up to age 18 years, with a diagnosis of a genetic WM disorder confirmed by molecular genetic testing and/or metabolic testing, were included in the study and categorized into LD or GLE group as per the classification suggested by the Global Leukodystrophy Initiative consortium in 2015. RESULTS: Forty-one patients were diagnosed to have LDs, and 66 patients had GLEs. The two most common LDs were metachromatic LD (16 patients) and X-linked adrenoleukodystrophy (seven patients). In the GLE group, lysosomal storage disorders were the most common (40 patients) followed by mitochondrial disorders (nine patients), with other metabolic disorders and miscellaneous conditions making up the rest. The clinical presentations, neuroimaging findings, and mutation spectrum of the patients in our cohort are discussed. CONCLUSIONS: This is one of the largest cohorts of genetic WM disorders reported till date from the Asian Indian population. The etiologies and clinical presentations identified in our study cohort are similar to those found in other Indian studies as well as in studies based on other populations from different parts of the world.

Inhibiting CSF1R alleviates cerebrovascular white matter disease and cognitive impairment.

White matter abnormalities, related to poor cerebral perfusion, are a core feature of small vessel cerebrovascular disease, and critical determinants of vascular cognitive impairment and dementia. Despite this importance there is a lack of treatment options. Proliferation of microglia producing an expanded, reactive population and associated neuroinflammatory alterations have been implicated in the onset and progression of cerebrovascular white matter disease, in patients and in animal models, suggesting that targeting microglial proliferation may exert protection. Colony-stimulating factor-1 receptor (CSF1R) is a key regulator of microglial proliferation. We found that the expression of CSF1R/Csf1r and other markers indicative of increased microglial abundance are significantly elevated in damaged white matter in human cerebrovascular disease and in a clinically relevant mouse model of chronic cerebral hypoperfusion and vascular cognitive impairment. Using the mouse model, we investigated long-term pharmacological CSF1R inhibition, via GW2580, and demonstrated that the expansion of microglial numbers in chronic hypoperfused white matter is prevented. Transcriptomic analysis of hypoperfused white matter tissue showed enrichment of microglial and inflammatory gene sets, including phagocytic genes that were the predominant expression modules modified by CSF1R inhibition. Further, CSF1R inhibition attenuated hypoperfusion-induced white matter pathology and rescued spatial learning impairments and to a lesser extent cognitive flexibility. Overall, this work suggests that inhibition of CSF1R and microglial proliferation mediates protection against chronic cerebrovascular white matter pathology and cognitive deficits. Our study nominates CSF1R as a target for the treatment of vascular cognitive disorders with broader implications for treatment of other chronic white matter diseases.

Genotypic and phenotypic heterogeneity among Chinese pediatric genetic white matter disorders.

BACKGROUND: The pediatric genetic white matter disorders are characterized by a broad disease spectrum. Genetic testing is valuable in the diagnosis. However, there are few studies on the clinical and genetic spectrum of Chinese pediatric genetic white matter disorders. METHODS: The participants were enrolled from the cohort of Peking Union Medical College Hospital. They all received history collection, brain MRI and gene sequencing. Their neurologic complaints which were related to white matter disorders occurred before 18. Brain MRI indicated periventricular and/or deep white matter lesions, fazekas grade 2-3. RESULTS: Among the 13 subjects, there were 11 males and two females. The average age of onset was 10.0 ± 5.5 years old. The potential genetic variants were found in 84.6% (11/13) subjects. The ABCD1 showed the greatest mutation frequency (30.8%, 4/13). The EIF2B3 A151fs, EIF2B4 c.885 + 2T > G, EIF2B5 R129X and MPV17 Q142X were novel pathogenic/likely pathogenic variants. 100% (4/4) ABCD1 carriers were accompanied by visual impairment, whereas 100% (3/3) EIF2B carriers developed dysuria. 100% (4/4) ABCD1 carriers exhibited diffuse white matter hyperintensities mainly in the posterior cortical regions, while the EIF2B4 and EIF2B5 carriers were accompanied by cystic degeneration. CONCLUSION: There is genotypic and phenotypic heterogeneity among Chinese subjects with pediatric genetic white matter disorders. The knowledge of these clinical and genetic characteristics facilitates an accurate diagnosis of these diseases.

Potential use of glucocorticosteroids in CSF1R mutation carriers - current evidence and future directions.

We recently found that glucocorticosteroids (GCs) have protective effects in CSF1R mutation carriers against developing symptomatic CSF1R-related leukoencephalopathy. Our findings were subsequently confirmed in a mouse model study. We have received many questions from patients, their families, patient organisations, and healthcare practitioners about the optimal type of GCs, the dose, the route of administration, and application timing. This paper attempts to answer the most urgent of these questions based on our previous studies and personal observations. Despite the promising observations, more research on larger patient groups is needed to elucidate the beneficial actions of GCs in CSF1R mutation carriers.

A novel missense variant in EIF2B5 identified in a consanguineous Iranian family with vanishing white matter disease and a brief review of the literature.

Vanishing of white matter (VWM) is a hereditary heterogeneous brain disorder that most often affects children. However, the onset of the disease varies from childhood to adulthood. VWM is caused by mutations in one of the five genes encoding subunits of the eukaryotic initiation factor eIF2B. In the current study, we aimed to determine the genetic cause of VWM in a large consanguineous Iranian family with three affected members. Next-generation sequencing was conducted on the proband to determine the underlying cause of VWM. The identified variant was validated by PCR-Sanger sequencing in the patient and was also segregated in his parents and two other affected members of the pedigree. The potential functional effects of this mutation within EIF2B5 were predicted by in silico analysis. We have also reviewed all EIF2B5 disease-causing variants and available clinical features of each patient reported in HGMD Professional 2022.2. A novel homozygous variant c.746T>G [p.Ile249Ser] was detected in EIF2B5 which was co-segregated with the disease in all affected family members in an autosomal recessive manner. All employed in silico prediction tools and 3D structure analysis for the novel mutation also supported the pathogenicity of this variant. Our study not only expanded the spectrum of the pathogenic variants in EIF2B5 but also presented a literature review on EIF2B5-related conditions that provide a comprehensive picture of the genetic nature of this gene and phenotypic variability in patients.

MAST1-related mega-corpus-callosum syndrome with central hypogonadism.

OBJECTIVE: Heterozygous variations in microtubule-associated serine/threonine kinase 1 gene (MAST1) were recently described in the mega-corpus-callosum syndrome with cerebellar hypoplasia and cortical malformations (MCCCHCM, MIM 618273), revealing the importance of the MAST genes family in global brain development. To date, patients with MAST1 gene mutations were mostly young children with central nervous system involvement, impaired motor function, speech delay, and brain magnetic resonance imaging (MRI) abnormalities. Here, we report the clinical presentation of an adult patient with a rare and de novo MAST1 mutation with central hypogonadism that could extend this phenotype. METHODS: A panel of 333 genes involved in epilepsy or cortical development was sequenced in the described patient. Routine biochemical analyses were performed, and hormonal status was investigated. RESULT: We report a 22-year-old man with a de novo, heterozygous missense variant in MAST1 (Chr19(GRCh37):g.12975903G > A, NP_055790.1:p.Gly517Ser). He presented with an epileptic encephalopathy associated with cerebral malformations, short stature, hypogonadotropic hypogonadism, and secondary osteopenia. CONCLUSION: This is the first patient with MAST1 gene mutation described with central hypogonadism, which may be associated with the phenotype of MCCCHCM syndrome.

Mutations in DARS2 result in global dysregulation of mRNA metabolism and splicing.

Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is a rare neurological disorder caused by the mutations in the DARS2 gene, which encodes the mitochondrial aspartyl-tRNA synthetase. The objective of this study was to understand the impact of DARS2 mutations on cell processes through evaluation of LBSL patient stem cell derived cerebral organoids and neurons. We generated human cerebral organoids (hCOs) from induced pluripotent stem cells (iPSCs) of seven LBSL patients and three healthy controls using an unguided protocol. Single cells from 70-day-old hCOs were subjected to SMART-seq2 sequencing and bioinformatic analysis to acquire high-resolution gene and transcript expression datasets. Global gene expression analysis demonstrated dysregulation of a number of genes involved in mRNA metabolism and splicing processes within LBSL hCOs. Importantly, there were distinct and divergent gene expression profiles based on the nature of the DARS2 mutation. At the transcript level, pervasive differential transcript usage and differential spliced exon events that are involved in protein translation and metabolism were identified in LBSL hCOs. Single-cell analysis of DARS2 (exon 3) showed that some LBSL cells exclusively express transcripts lacking exon 3, indicating that not all LBSL cells can benefit from the "leaky" nature common to splice site mutations. At the gene- and transcript-level, we uncovered that dysregulated RNA splicing, protein translation and metabolism may underlie at least some of the pathophysiological mechanisms in LBSL. To confirm hCO findings, iPSC-derived neurons (iNs) were generated by overexpressing Neurogenin 2 using lentiviral vector to study neuronal growth, splicing of DARS2 exon 3 and DARS2 protein expression. Live cell imaging revealed neuronal growth defects of LBSL iNs, which was consistent with the finding of downregulated expression of genes related to neuronal differentiation in LBSL hCOs. DARS2 protein was downregulated in iNs compared to iPSCs, caused by increased exclusion of exon 3. The scope and complexity of our data imply that DARS2 is potentially involved in transcription regulation beyond its canonical role of aminoacylation. Nevertheless, our work highlights transcript-level dysregulation as a critical, and relatively unexplored, mechanism linking genetic data with neurodegenerative disorders.

Clinical, genetic, and molecular characteristics in a central-southern Chinese cohort of genetic leukodystrophies.

OBJECTIVE: Leukodystrophies are a diverse group of rare inherited disorders that affect the white matter of the central nervous system with a wide phenotypic spectrum. We aimed to characterize the clinical and genetic features of leukodystrophies in a central-southern Chinese cohort. METHODS: A cohort of 16 Chinese probands with leukodystrophy was recruited and performed genetic analysis by targeted panels or whole-exome sequencing. Further functional analysis of identified mutations in the colony stimulating factor 1 receptor (CSF1R) gene was explored. RESULTS: A total of eight pathogenic variants (3 novel, 5 documented) were identified in genes including AARS2, ABCD1, CSF1R, and GALC. Common symptoms of leukodystrophy such as cognitive decline, behavioral symptoms, bradykinesia, and spasticity were observed in mutation carriers as well as other rare features (e.g., seizure, dysarthric, and vision impairment). Overexpressing CSF1R mutants p.M875I and p.F971Sfs*7 in vitro showed pronounced cleavage CSF1R and suppressed protein expression, respectively, and reduced transcripts of both mutants were observed. CSF1 treatment revealed deficient and suppressed CSF1R phospho-activation with the mutants. In contrast to the plasma membrane and endoplasmic reticulum (ER) localized wild-type CSF1R, M875I mutant showed much less membrane association and greater detainment in the ER, whereas F971Sfs*7 mutation led to aberrant non-ER localization. Both mutations caused suppressed cell viability, which was partially resulted from deficient/suppressed CSF1R-ERK signaling. INTERPRETATION: In summary, our findings expand the mutation spectrum of these genes in leukodystrophies. Supported by in vitro validation of the pathogenicity of heterozygous CSF1R mutations, our data also provide insights into the pathogenic mechanisms of CSF1R-related leukodystrophy.

Prophylactic effect of chronic immunosuppression in a mouse model of CSF-1 receptor-related leukoencephalopathy.

Mutations leading to colony-stimulating factor-1 receptor (CSF-1R) loss-of-function or haploinsufficiency cause CSF1R-related leukoencephalopathy (CRL), an adult-onset disease characterized by loss of myelin and neurodegeneration, for which there is no effective therapy. Symptom onset usually occurs in the fourth decade of life and the penetrance of disease in carriers is high. However, familial studies have identified a few carriers of pathogenic CSF1R mutations that remain asymptomatic even in their seventh decade of life, raising the possibility that the development and severity of disease might be influenced by environmental factors. Here we report new cases in which long-term glucocorticoid treatment is associated with asymptomatic status in elder carriers of pathogenic CSF-1R mutations. The main objective of the present study was to investigate the link between chronic immunosuppression initiated pre-symptomatically and resistance to the development of symptomatic CRL, in the Csf1r+/- mouse model. We show that chronic prednisone administration prevents the development of memory, motor coordination and social interaction deficits, as well as the demyelination, neurodegeneration and microgliosis associated with these deficits. These findings are in agreement with the preliminary clinical observations and support the concept that pre-symptomatic immunosuppression is protective in patients carrying pathogenic CSF1R variants associated with CRL. Proteomic analysis of microglia and oligodendrocytes indicates that prednisone suppresses processes involved in microglial activation and alleviates senescence and improves fitness of oligodendrocytes. This analysis also identifies new potential targets for therapeutic intervention.

Pearls & Oy-sters: CSF1R-Related Leukoencephalopathy With Spinal Cord Lesions Mimicking Multiple Sclerosis.

CSF1R-related leukoencephalopathy is an autosomal dominant neurologic disorder causing microglial dysfunction with a wide range of neurologic complications, including motor dysfunction, dementia, and seizures. This case report highlights an unusual presentation of CSF1R-related leukoencephalopathy with radiographic spinal cord involvement initially diagnosed as multiple sclerosis. This case highlights the importance of considering adult-onset neurogenetic disorders in the setting of white matter disease. Genetic testing provides a confirmatory diagnosis for an expanding number of adult-onset leukoencephalopathies and informs therapeutic decision-making.

Brain abnormalities, neurodegeneration, and dysosteosclerosis (BANDDOS): new cases, systematic literature review, and associations with CSF1R-ALSP.

CSF1R mutations cause autosomal-dominant CSF1R-related leukoencephalopathy with axonal spheroids and pigmented glia (CSF1R-ALSP) and autosomal-recessive brain abnormalities, neurodegeneration, and dysosteosclerosis (BANDDOS). The former is increasingly recognized, and disease-modifying therapy was introduced; however, literature is scarce on the latter. This review analyzes BANDDOS and discusses similarities and differences with CSF1R-ALSP.We systematically retrieved and analyzed the clinical, genetic, radiological, and pathological data on the previously reported and our cases with BANDDOS. We identified 19 patients with BANDDOS (literature search according to the PRISMA 2020 guidelines: n = 16, our material: n = 3). We found 11 CSF1R mutations, including splicing (n = 3), missense (n = 3), nonsense (n = 2), and intronic (n = 2) variants and one inframe deletion. All mutations disrupted the tyrosine kinase domain or resulted in nonsense-mediated mRNA decay. The material is heterogenous, and the presented information refers to the number of patients with sufficient data on specific symptoms, results, or performed procedures. The first symptoms occurred in the perinatal period (n = 5), infancy (n = 2), childhood (n = 5), and adulthood (n = 1). Dysmorphic features were present in 7/17 cases. Neurological symptoms included speech disturbances (n = 13/15), cognitive decline (n = 12/14), spasticity/rigidity (n = 12/15), hyperactive tendon reflex (n = 11/14), pathological reflexes (n = 8/11), seizures (n = 9/16), dysphagia (n = 9/12), developmental delay (n = 7/14), infantile hypotonia (n = 3/11), and optic nerve atrophy (n = 2/7). Skeletal deformities were observed in 13/17 cases and fell within the dysosteosclerosis - Pyle disease spectrum. Brain abnormalities included white matter changes (n = 19/19), calcifications (n = 15/18), agenesis of corpus callosum (n = 12/16), ventriculomegaly (n = 13/19), Dandy-Walker complex (n = 7/19), and cortical abnormalities (n = 4/10). Three patients died in infancy, two in childhood, and one case at unspecified age. A single brain autopsy evidenced multiple brain anomalies, absence of corpus callosum, absence of microglia, severe white matter atrophy with axonal spheroids, gliosis, and numerous dystrophic calcifications.In conclusion, BANDDOS presents in the perinatal period or infancy and has a devastating course with congenital brain abnormalities, developmental delay, neurological deficits, osteopetrosis, and dysmorphic features. There is a significant overlap in the clinical, radiological, and neuropathological aspects between BANDDOS and CSF1R-ALSP. As both disorders are on the same continuum, there is a window of opportunity to apply available therapy in CSF1R-ALSP to BANDDOS.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL): A challenging diagnosis and a rare multiple sclerosis mimic.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is an extremely rare hereditary cerebral small vessel disease caused by homozygous or compound heterozygous mutations in the gene coding for high-temperature requirement A serine peptidase 1 (HtrA1). Given the rare nature of the disease, delays in diagnosis and misdiagnosis are not uncommon. In this article, we reported the first case of CARASIL from Saudi Arabia with a novel homozygous variant c.1156C>T in exon 7 of the HTRA1 gene. The patient was initially misdiagnosed with primary progressive multiple sclerosis and treated with rituximab. CARASIL should be considered in the differential diagnosis of patients with suspected atypical progressive multiple sclerosis who have additional signs such as premature scalp alopecia and low back pain with diffuse white matter lesions in brain MRI. Genetic testing is important to confirm the diagnosis.