Krabbe Disease Research Articles

Emerging Role of Ubiquitin Proteasome System and Autophagy in Pediatric Demyelinating Leukodystrophies and Therapeutic Opportunity

Leukodystrophies represent a heterogeneous group of disorders characterized by specific genetic mutations, metabolic abnormalities, and degeneration of white matter in the central nervous system. These disorders are classified into several categories, with X-linked adrenoleukodystrophy (X-ALD), metachromatic leukodystrophy (MLD), and globoid cell leukodystrophy (GLD) being the most prevalent demyelinating leukodystrophies in pediatric populations. Maintaining proteostasis, which is critical for normal cellular function, relies fundamentally on the ubiquitin–proteasome system (UPS) and autophagy for the degradation of misfolded and damaged proteins. Compelling evidence has highlighted the critical roles of UPS and autophagy dysfunction in the pathogenesis of neurodegenerative diseases. Given the complex and poorly understood pathomechanisms underlying demyelinating leukodystrophies, coupled with the pressing need for effective therapeutic strategies, this review aims to systemically analyze the molecular and pathological evidence linking UPS and autophagy dysfunction to demyelinating leukodystrophies, specifically X-ALD and GLD. Furthermore, we will assess the therapeutic potential of autophagy modulators in the management of X-ALD and GLD, with the objective to inspire further research into therapeutic approaches that target autophagy and UPS pathways. Novel therapies that enhance autophagy and UPS function hold promise as complementary regimens in combination therapies aimed at achieving comprehensive correction of the pathogenic mechanisms in demyelinating leukodystrophies.

Infantile Krabbe disease (0-12 months), progression, and recommended endpoints for clinical trials.

Krabbe disease is due to deficiency of galactocerebrosidase, resulting in progressive neurodegeneration due to demyelination. The purpose of this study is to document disease progression in the newly classified infantile-onset (0-12 months). We evaluated the outcomes of hematopoietic stem cell transplantation (HSCT) and described meaningful clinical endpoints. Patients with infantile Krabbe disease were prospectively evaluated between 2000 and 2022. All patients underwent comprehensive and standardized protocols. Descriptive statistics and Kaplan-Meier survival curves were used for analysis. One hundred and thirty-seven children with infantile Krabbe disease were included (68 males and 69 females). Of the 137, 96 were not treated and 41 underwent hematopoietic stem cell transplantation. Twenty-three were asymptomatic and 18 symptomatic. Initial symptoms included irritability, developmental delay or loss of milestones, feeding difficulties, spasticity, and reflux with an average survival of 2.2. Abnormalities in nerve conduction studies, auditory brainstem responses, and brain MRIs were evident in both groups of patients. Age at transplantation and signs and symptoms determined functional outcomes. Symptomatic and asymptomatic transplanted patients showed an increase in galactocerebrosidase and a decrease in psychosine, but did not reach the normal range. The median survival for transplanted symptomatic patients was 5 years while asymptomatic was extended to 15.5 years. Infantile Krabbe disease with onset before 12 months is rapidly progressive. Irreversible brain damage occurs unless timely HSCT is performed. HSCT does not prevent the progression of peripheral nerve disease. This study can be used to monitor patients and evaluate the effects of future therapies.

The Effect of Donepezil Hydrochloride in the Twitcher Mouse Model of Krabbe Disease.

Krabbe disease (KD) is a rare demyelinating disorder characterized by demyelination caused by mutations in the GALC gene, resulting in toxic accumulation of psychosine. Psychosine has been identified as detrimental to oligodendrocytes, leading to demyelination through diverse hypothesized pathways. Reducing demyelination is essential to maintain neurological function in KD; however, therapeutic interventions are currently limited. Acetylcholinesterase inhibitors (AChEi) are commonly used for symptomatic management of Alzheimer's Disease and are suggested to have potential disease-modifying effects, including regulating myelin state. In particular, donepezil, an AChEi, has demonstrated promising effects in cellular and animal models, including promotion of the expression of myelin-related genes and reduction of glial cell reactivity. This drug also acts as an agonist for sigma-1 receptors (Sig-1R), which are implicated in demyelination diseases. In the context of drug repurposing, here, we demonstrate that administration of donepezil has protective effects in the twitcher mouse model of KD. We provide data showing that donepezil preserves myelin and reduces glial cell reactivity in the brains of twitcher mice. Moreover, donepezil also improves behavioral phenotypes and increases lifespan in twitcher animals. These findings suggest that donepezil, with its dual activity as an AChE inhibitor and Sig-1R agonist, may hold promise as a therapeutic candidate for demyelinating diseases, including KD.

A lipid nanoparticle-based oligodendrocyte-specific mRNA therapy

Despite the wide range of applications of mRNA therapies, major difficulties exist in the efficient delivery of mRNA into oligodendrocytes, a type of glial cells in the brain. Commonly used viral vectors are not efficient in transforming oligodendrocytes. In this study, we introduced mRNAs into oligodendrocytes with high efficiency and specificity using LUNAR® lipid nanoparticles. The uptake of LUNAR® lipid nanoparticles occurred via low-density lipoprotein receptors in the presence of apoprotein E. A single dose of LUNAR®-human galactosylceramidase mRNA significantly improved phenotypes and survival of twitcher mice, a mouse model of Krabbe disease wherein oligodendrocytes are damaged by galactosylceramidase deficiency. This approach to mRNA therapeutics, combined with cell-specific nanocarriers, demonstrates remarkable potential for the treatment of neurological disorders associated with oligodenrocytes.

Expression study of Krabbe Disease GALC missense variants - Insights from quantification profiles of residual enzyme activity, secretion and psychosine levels.

Krabbe disease (KD) is an autosomal recessive lysosomal storage disorder caused by loss-of-function mutations in the GALC gene, which encodes for the enzyme galactosylceramidase (GALC). GALC is crucial for myelin metabolism. Functional deficiency of GALC leads to toxic accumulation of psychosine, dysfunction and death of oligodendrocytes, and eventual brain demyelination. To date, 46 clinically-relevant, pathogenic GALC missense mutations (MMs) have been identified in KD patients. These MMs are present in ∼70% of KD cases reported over 8 published studies between 1996 - 2019. However, the mechanisms by which these MMs lead to GALC functional deficiency and their correlations with clinical phenotype remain poorly understood. To address this, we generated a GALC -knockout human oligodendrocytic cell line (MO3.13/ GALC -KO) using CRISPR-Cas9 method to assess GALC function and GALC secretion. We evaluated 5 polymorphic and 31 clinically-relevant MM variants (MMVs) using transient expression assays. Our results showed that 26 MMVs, including 10 co-variants with p.I562T, reduced GALC activity by 92% - 100% compared to wild-type GALC (WT-GALC). MMVs from infantile-onset KD patients produced < 2% of WT activity, whereas those associated with juvenile- and adult-onset cases retained up to 7% of WT activity. Residual GALC activity was correlated with mature, lysosomal GALC protein levels (Pearson r = 0.93, P<0.0001). Many low-activity MMVs did not correspondingly impair GALC secretion. Twenty-one of the 26 low-activity MMVs showed a 21% - 100% reduction in sec-GALC levels, indicating varying degrees of GALC mis-trafficking among these variants. Importantly, GALC activity among MMVs strongly correlates with clinical disease severity, based on the age of symptom onset in patients with either homozygous MM (Pearson r = 0.98, P<0.0001, n = 7) or compound heterozygous (Pearson r = 0.94, P<0.0001, n = 12) MM-null mutation genotypes. Thus, our data suggests that GALC activity could serve as a prognostic disease indicator under specific experimental conditions. We further investigated the impact of pathogenic MMVs on psychosine accumulation, a key biomarker for KD. Psychosine levels were 21-fold higher in mock control cells compared to WT-GALC transfected cells (mock = 0.349 pmol/mg, WT-GALC = 0.016 pmol/mg), but negatively correlated with GALC activity among pathogenic MMVs (Pearson r = -0.63, P < 0.01, n = 15). Although psychosine levels were higher in most MMVs associated with infantile-onset KD, no significant correlations with clinical onset were detected. Overall, our study provides a comprehensive quantitative analysis of the functional deficits and mis-trafficking associated with clinically-relevant GALC MMVs, enhancing our understanding of the molecular genetics and genotype-phenotype correlations of the GALC gene in Krabbe disease.

Glycosphingolipids Associated Metabolic Disorders

Lipids play diverse roles in sustaining life, including energy storage, hormonal balance, and cellular communication. Alterations in lipid metabolism can lead to various disorders, including diabetes, atherosclerosis, cancer, and neurodegenerative diseases. Among these disorders, lysosomal storage disorders (LSDs) related to glycosphingolipids metabolism present significant challenges. This review systematically analyzes the current literature on LSDs, focusing on classification, clinical presentations, diagnostic advancements, available treatments, and emerging therapeutic strategies. Glycosphingolipids biosynthesis, particularly its role in viral dissemination and melanin synthesis, underscores its significance in health and disease. Additionally, the review delves into specific LSDs, such as Fabry disease, Gaucher disease, Sandhoff disease, Tay-Sachs disease, and Krabbe disease, highlighting their pathophysiology, prevalence, and treatment options. Enzyme replacement therapy and hematopoietic stem cell transplantation are mainstays in LSD treatment, but gene therapy shows promise. Furthermore, the review explores the role of glycosphingolipids in non-communicable diseases like diabetes, cancer, atherosclerosis, lupus, Alzheimer's, Parkinson's disease, and influenza. Understanding glycosphingolipid metabolism offers insights into disease mechanisms and therapeutic targets, paving the way for improved treatments and ultimately enhancing patient outcomes.

Genetic and Functional Analyses of Patients with Marked Hypo-High-Density Lipoprotein Cholesterolemia.

This study aimed to analyze two cases of marked hypo-high-density lipoprotein (HDL) cholesterolemia to identify mutations in ATP-binding cassette transporter A1 (ABCA1) and elucidate the molecular mechanism by which these novel pathological mutations contribute to hypo-HDL cholesterolemia in Tangier disease. Wild type and mutant expression plasmids containing a FLAG tag inserted at the C-terminus of the human ABCA1 gene were generated and transfected into HEK293T cells. ABCA1 protein expression and cholesterol efflux were evaluated via Western blotting and efflux assay. The difference in the rate of change in protein expression was evaluated when proteolytic and protein-producing systems were inhibited. In case 1, a 20-year-old woman presented with a chief complaint of gait disturbance. Her HDL-C level was only 6.2 mg/dL. Tangier disease was suspected because of muscle weakness, decreased nerve conduction velocity, and splenomegaly. Whole-exome analysis showed compound heterozygosity for a W484* nonsense mutation and S1343I missense mutation, which confirmed Tangier disease. Cholesterol efflux decreased by a mixture of W484* and S1343I mutations. The S1343I mutation decreased the protein production rate but increased the degradation rate, decreasing the protein levels. This patient also had Krabbe disease. The endogenous ABCA1 protein level of macrophage cell decreased by knocking down its internal galactocerebrosidase. Case 2, a 51-year-old woman who underwent tonsillectomy presented with peripheral neuropathy, corneal opacity, and HDL-C of 3.4 mg/dL. Whole-exome analysis revealed compound heterozygosity for R579* and R1572* nonsense mutations, which confirmed Tangier disease. Case 1 is a new ABCA1 mutation with complex pathogenicity, namely, a W484*/S1343I compound heterozygote with marked hypo-HDL cholesterolemia. Analyses of the compound heterozygous mutations indicated that decreases in ABCA1 protein levels and cholesterol efflux activity caused by the novel S1343I mutation combined with loss of W484* protein activity could lead to marked hypo-HDL cholesterolemia. Galactocerebrosidase dysfunction could also be a potential confounding factor for ABCA1 protein function.

Overview of Neuro-Ophthalmic Findings in Leukodystrophies.

Background: Leukodystrophies are a group of rare genetic diseases that primarily affect the white matter of the central nervous system. The broad spectrum of metabolic and pathological causes leads to manifestations at any age, most often in childhood and adolescence, and a variety of symptoms. Leukodystrophies are usually progressive, resulting in severe disabilities and premature death. Progressive visual impairment is a common symptom. Currently, no overview of the manifold neuro-ophthalmologic manifestations and visual impact of leukodystrophies exists. Methods: Data from 217 patients in the Hamburg leukodystrophy cohort were analyzed retrospectively for neuro-ophthalmologic manifestations, age of disease onset, and magnetic resonance imaging, visual evoked potential, and optical coherence tomography findings and were compared with data from the literature. Results: In total, 68% of the patients suffered from neuro-ophthalmologic symptoms, such as optic atrophy, visual neglect, strabismus, and nystagmus. Depending on the type of leukodystrophy, neuro-ophthalmologic symptoms occurred early or late during the course of the disease. Magnetic resonance imaging scans revealed pathologic alterations in the visual tract that were temporally correlated with symptoms. Conclusions: The first optical coherence tomography findings in Krabbe disease and metachromatic leukodystrophy allow retinal assessments. Comprehensive literature research supports the results of this first overview of neuro-ophthalmologic findings in leukodystrophies.

Abstract 8: Facilitating Hematopoietic Cell Transplant for Patients with Infantile Krabbe Disease Identified by Newborn Screening

Abstract 8: Facilitating Hematopoietic Cell Transplant for Patients with Infantile Krabbe Disease Identified by Newborn Screening

Exploring the globoid cell leukodystrophy protein network and therapeutic interventions

Globoid cell leukodystrophy is a severe rare disorder characterized by white matter degradation, resulting in a progressive loss of physical and mental abilities and has extremely limited therapeutic interventions. Therefore, this study aimed to delve into the Globoid cell leukodystrophy associated intricate network of differentially expressed genes (p < 0.05, |Fc|> 1) to identify potential druggable targets and possible therapeutic interventions using small molecules. The disease-associated neuronal protein circuit was constructed and analyzed, identifying 53 nodes (minimum edge cutoff 1), among which five (FOS, FOSB, GDNF, GFRA1, and JUN) were discerned as potential core protein nodes. Although our research enumerates the potential small molecules to target various protein nodes in the proposed disease network, we particularly underscore T-5224 to inhibit c-Jun activity as JUN was identified as one of the pivotal elements within the disease-associated neuronal protein circuit. The evaluation of T-5224 binding energy (− 11.0 kcal/mol) from docking study revealed that the compound to exhibit a notable affinity towards Jun/CRE complex. Moreover, the structural integrity of complex was affirmed through comprehensive molecular dynamics simulations, indicating a stable hydrophilic interaction between T-5224 and the Jun/CRE complex, thereby enhancing protein compactness and reducing solvent accessibility. This binding energy was further substantiated by free binding analysis, revealing a substantial thermodynamics complex state (− 448.00 ± 41.73 kJ/mol). Given that this investigation is confined to a computational framework, we additionally propose a hypothetical framework to ascertain the feasibility of inhibiting the Jun/CRE complex with T-5224 against Globoid cell leukodystrophy, employing a combination of in vitro and in vivo methodologies as a prospective avenue of this study.

Human iPSC-derived myelinating organoids and globoid cells to study Krabbe Disease.

Krabbe disease (Kd) is a lysosomal storage disorder (LSD) caused by the deficiency of the lysosomal galactosylceramidase (GALC) which cleaves the myelin enriched lipid galactosylceramide (GalCer). Accumulated GalCer is catabolized into the cytotoxic lipid psychosine that causes myelinating cells death and demyelination which recruits microglia/macrophages that fail to digest myelin debris and become globoid cells. Here, to understand the pathological mechanisms of Kd, we used induced pluripotent stem cells (iPSCs) from Kd patients to produce myelinating organoids and microglia. We show that Kd organoids have no obvious defects in neurogenesis, astrogenesis, and oligodendrogenesis but manifest early myelination defects. Specifically, Kd organoids showed shorter but a similar number of myelin internodes than Controls at the peak of myelination and a reduced number and shorter internodes at a later time point. Interestingly, myelin is affected in the absence of autophagy and mTOR pathway dysregulation, suggesting lack of lysosomal dysfunction which makes this organoid model a very valuable tool to study the early events that drive demyelination in Kd. Kd iPSC-derived microglia show a marginal rate of globoid cell formation under normal culture conditions that is drastically increased upon GalCer feeding. Under normal culture conditions, Kd microglia show a minor LAMP1 content decrease and a slight increase in the autophagy protein LC3B. Upon GalCer feeding, Kd cells show accumulation of autophagy proteins and strong LAMP1 reduction that at a later time point are reverted showing the compensatory capabilities of globoid cells. Altogether, this supports the value of our cultures as tools to study the mechanisms that drive globoid cell formation and the compensatory mechanism in play to overcome GalCer accumulation in Kd.

Experiences of patients with metachromatic leukodystrophy, adrenoleukodystrophy, or Krabbe disease and the experiences of their family members: a qualitative systematic review.

This review aimed to synthesize the experiences of patients with metachromatic leukodystrophy, adrenoleukodystrophy, or Krabbe disease and the experiences of their families. Leukodystrophies are metabolic diseases caused by genetic mutations. There are multiple forms of the disease, varying in age of onset and symptoms. The progression of leukodystrophies worsens central nervous system symptoms and significantly affects the lives of patients and their families. Qualitative studies on the experiences of patients with leukodystrophies and their family members were included. These experiences included treatments such as enzyme replacement therapy and hematopoietic stem cell transplantation; effects of tracheostomy and gastrostomy; burdens on the family, coordinating care within the health care system, and family planning due to genetic disorders. This review considered studies in any setting. MEDLINE (Ovid), CINAHL Plus (EBSCOhost), APA PsycINFO (EBSCOhost), Scopus, and MedNar databases were searched on November 18, 2022. Study selection, critical appraisal, data extraction, and data synthesis were conducted in accordance with the JBI methodology for systematic reviews of qualitative evidence, and synthesized findings were evaluated according to the ConQual approach. Eleven studies were eligible for synthesis, and 45 findings were extracted corresponding with participants' voices. Of these findings, 40 were unequivocal and 5 were credible. The diseases in the included studies were metachromatic leukodystrophy and adrenoleukodystrophy; no studies were identified for patients with Krabbe disease and their families. These findings were grouped into 11 categories and integrated into 3 synthesized findings, including i) providing care by family members and health care providers as physical symptoms progress, which relates to the effects of the characteristics of progressive leukodystrophies; ii) building medical teamwork to provide appropriate support services, comprising categories related to the challenges experienced with the health care system for patients with leukodystrophy and their families; and iii) coordinating family functions to accept and cope with the disease, which included categories related to family psychological difficulties and role divisions within the family. According to the ConQual criteria, the second synthesized finding had a low confidence level, and the first and third synthesized findings had a very low confidence level. The synthesized findings of this review provide evidence on the experiences of patients with metachromatic leukodystrophy or adrenoleukodystrophy and their families. These findings indicate that there are challenges in managing a patient's physical condition and coordinating the health care system and family functions. PROSPERO CRD42022318805. A Japanese-language version of the abstract of this review is available [ http://links.lww.com/SRX/A49 ].

Dietary Supplementation with n-3 Polyunsaturated Fatty Acids Delays the Phenotypic Manifestation of Krabbe Disease and Partially Restores Lipid Mediator Production in the Brain-Study in a Mouse Model of the Disease.

Lipid mediators from fatty acid oxidation have been shown to be associated with the severity of Krabbe disease (KD), a disorder linked to mutations in the galactosylceramidase (GALC) gene. This study aims to investigate the effects of n-3 polyunsaturated fatty acid (PUFA) supplementation on KD traits and fatty acid metabolism using Twitcher (Tw) animals as a natural model for KD. Wild-type (Wt), heterozygous (Ht), and affected Tw animals were treated orally with 36 mg n-3 PUFAs/kg body weight/day from 10 to 35 days of life. The end product of PUFA peroxidation (8-isoprostane), the lipid mediator involved in the resolution of inflammatory exudates (resolvin D1), and the total amount of n-3 PUFAs were analyzed in the brains of mice. In Tw mice, supplementation with n-3 PUFAs delayed the manifestation of disease symptoms (p < 0.0001), and in the bran, decreased 8-isoprostane amounts (p < 0.0001), increased resolvin D1 levels (p < 0.005) and increased quantity of total n-3 PUFAs (p < 0.05). Furthermore, total brain n-3 PUFA levels were associated with disease severity (r = -0.562, p = 0.0001), resolvin D1 (r = 0.712, p < 0.0001), and 8-isoprostane brain levels (r = -0.690, p < 0.0001). For the first time in a natural model of KD, brain levels of n-3 PUFAs are shown to determine disease severity and to be involved in the peroxidation of brain PUFAs as well as in the production of pro-resolving lipid mediators. It is also shown that dietary supplementation with n-3 PUFAs leads to a slowing of the phenotypic presentation of the disease and restoration of lipid mediator production.

Triggered saccadic oscillations: case series and review of the literature.

Saccadic oscillations (SOs) mostly occur spontaneously, but can be occasionally triggered by various stimuli. To determine clinical characteristics and underlying mechanisms of triggered SOs, we analyzed the clinical features and quantitative eye-movement recordings of six new patients and 10 patients in the literature who exhibited with triggered SOs. Eleven of the 16 patients (69%) had a lesion involving cerebellum and/or brainstem such as cerebellar degeneration, cerebellitis, or cerebellar infarction. The other causes were vestibular migraine (n = 2), multiple sclerosis (n = 1), Krabbe disease (n = 1), and idiopathic (n = 1). Vestibular stimulation was the most common trigger (n = 11, 69%), followed by removal of visual fixation (n = 4, 25%), hyperventilation (n = 1), light (n = 1), and blink (n = 1). The types of triggered SOs were varied which included ocular flutter (n = 13), opsoclonus (n = 3), vertical SOs (n = 2), and macrosaccadic oscillations (n = 1). Three patients exhibited downbeat nystagmus either before (n = 1) or after (n = 2) the onset of SOs. The frequency of triggered SOs ranged from 4 to 15Hz, and oscillations with smaller amplitudes had higher frequencies and smaller peak velocities. SOs can be triggered by the modulation of unstable saccadic neural networks through vestibular and visual inputs in lesions of the brainstem and cerebellum.

Late-onset Krabbe disease presenting as spastic paraplegia - implications of GCase and CTSB/D.

Krabbe disease (KD) is a multisystem neurodegenerative disorder with severe disability and premature death, mostly with an infancy/childhood onset. In rare cases of late-onset phenotypes, symptoms are often milder and difficult to diagnose. We here present a translational approach combining diagnostic and biochemical analyses of a male patient with a progressive gait disorder starting at the age of 44 years, with a final diagnosis of late-onset KD (LOKD). Additionally to cerebral MRI, protein structural analyses of the β-galactocerebrosidase protein (GALC) were performed. Moreover, expression, lysosomal localization, and activities of β-glucocerebrosidase (GCase), cathepsin B (CTSB), and cathepsin D (CTSD) were analyzed in leukocytes, fibroblasts, and lysosomes of fibroblasts. Exome sequencing revealed biallelic likely pathogenic variants: GALC exons 11-17: 33 kb deletion; exon 4: missense variant (c.334A>G, p.Thr112Ala). We detected a reduced GALC activity in leukocytes and fibroblasts. While histological KD phenotypes were absent in fibroblasts, they showed a significantly decreased activities of GCase, CTSB, and CTSD in lysosomal fractions, while expression levels were unaffected. The presented LOKD case underlines the age-dependent appearance of a mildly pathogenic GALC variant and its interplay with other lysosomal proteins. As GALC malfunction results in reduced ceramide levels, we assume this to be causative for the here described decrease in CTSB and CTSD activity, potentially leading to diminished GCase activity. Hence, we emphasize the importance of a functional interplay between the lysosomal enzymes GALC, CTSB, CTSD, and GCase, as well as between their substrates, and propose their conjoined contribution in KD pathology.

Promyelinating drugs ameliorate oligodendrocyte pathologies in a mouse model of Krabbe disease

Krabbe disease (KD) is a rare inherited demyelinating disorder caused by a deficiency in the lysosomal enzyme galactosylceramide (GalCer) β-galactosidase. Most patients with KD exhibit fatal cerebral demyelination with apoptotic oligodendrocyte (OL) death and die before the age of 2–4 years. We have previously reported that primary OLs isolated from the brains of twitcher (twi) mice, an authentic mouse model of KD, have cell-autonomous developmental defects and undergo apoptotic death accompanied by abnormal accumulation of psychosine, an endogenous cytotoxic lyso-derivative of GalCer. In this study, we aimed to investigate the effects of the preclinical promyelinating drugs clemastine and Sob-AM2 on KD OL pathologies using primary OLs isolated from the brains of twi mice. Both agents specifically prevented the apoptotic death observed in twi OLs. However, while Sob-AM2 showed higher efficacy in restoring the impaired differentiation and maturation of twi OLs, clemastine more potently reduced the endogenous psychosine levels. These results present the first preclinical in vitro data, suggesting that clemastine and Sob-AM2 can act directly and distinctly on OLs in KD and ameliorate their cellular pathologies associated with myelin degeneration.

Newborn Screening for 6 Lysosomal Storage Disorders in China

Newborn screening (NBS) for lysosomal storage disorders (LSDs) is becoming an increasing concern in public health. However, the birth prevalence of these disorders is rarely reported in the Chinese population, and subclinical forms of diseases among patients identified by NBS have not been evaluated. To evaluate the birth prevalence of the 6 LSDs in the Shanghai population and determine subclinical forms based on clinical, biochemical, and genetic characteristics. This cohort study included 50 108 newborns recruited from 41 hospitals in Shanghai between January and December 2021 who were screened for 6 LSDs using tandem mass spectrometry (MS/MS). Participants with screen-positive results underwent molecular and biochemical tests and clinical assessments. Data were analyzed from January 2021 through October 2022. All participants were screened for Gaucher, acid sphingomyelinase deficiency (ASMD), Krabbe, mucopolysaccharidosis type I, Fabry, and Pompe diseases using dried blood spots. Primary outcomes were the birth prevalence and subclinical forms of the 6 LSDs in the Shanghai population. Disease biomarker measurements, genetic testing, and clinical analysis were used to assess clinical forms of LSDs screened. Among 50 108 newborns (26 036 male [52.0%]; mean [SD] gestational age, 38.8 [1.6] weeks), the mean (SD) birth weight was 3257 (487) g. The MS/MS-based NBS identified 353 newborns who were positive. Of these, 27 newborns (7.7%) were diagnosed with 1 of 6 LSDs screened, including 2 newborns with Gaucher, 5 newborns with ASMD, 9 newborns with Krabbe, 8 newborns with Fabry, and 3 newborns with Pompe disease. The combined birth prevalence of LSDs in Shanghai was 1 diagnosis in 1856 live births, with Krabbe disease the most common (1 diagnosis/5568 live births), followed by Fabry disease (1 diagnosis/6264 live births), and ASMD (1 diagnosis/10 022 live births). Biochemical, molecular, and clinical analysis showed that early-onset clinical forms accounted for 3 newborns with positive results (11.1%), while later-onset forms represented nearly 90% of diagnoses (24 newborns [88.9%]). In this study, the combined birth prevalence of the 6 LSDs in Shanghai was remarkably high. MS/MS-based newborn screening, combined with biochemical and molecular genetic analysis, successfully identified and characterized newborns who were screen-positive, which may assist with parental counseling and management decisions.

Perinatal loss of galactosylceramidase in both oligodendrocytes and microglia is crucial for the pathogenesis of Krabbe disease in mice

Lysosomal galactosylceramidase (GALC) is expressed in all brain cells including oligodendrocytes (OLs), microglia and astrocytes, though the cell-specific function of GALC is largely unknown. Mutations in GALC cause Krabbe disease, a fatal neurological lysosomal storage disorder that usually affects infants. To study how Galc ablation in each glial cell type contributes to Krabbe pathogenesis, we used conditional Galc floxed mice. Here, we found that OL-specific Galc conditional knockout (CKO) in mice results in a phenotype that includes wasting, psychosine accumulation, and neuroinflammation. Microglia- or astrocyte-specific Galc deletion alone in mice did not show any specific phenotypes. Interestingly, mice with CKO of Galc from both OLs and microglia have a more severe neuroinflammation with an increase in globoid cell accumulation than OL-specific CKO alone. Moreover, the enhanced phenotype occurred without additional accumulation of psychosine. Further studies revealed that Galc-KO microglia cocultured with Galc-KO OLs elicits globoid cell formation and the overexpression of osteopontin and MCP-1, both proteins are known to recruit immune cells and promote engulfment of debris and damaged cells. We conclude that OLs are the primary cells that initiate KD with an elevated psychosine level and microglia are required for the progression of neuroinflammation in a psychosine independent manner.

Lysosomal storage diseases. Sphingolipidoses – leukodystrophy

Lysosomal storage diseases. Sphingolipidoses – leukodystrophy

Dual rare genetic diseases in five pediatric patients: insights from next-generation diagnostic methods

BackgroundClinicians traditionally aim to identify a singular explanation for the clinical presentation of a patient; however, in some cases, the diagnosis may remain elusive or fail to comprehensively explain the clinical findings. In recent years, advancements in next-generation sequencing, including whole-exome sequencing, have led to the incidental identification of dual diagnoses in patients. Herein we present the cases of five pediatric patients diagnosed with dual rare genetic diseases. Their natural history and diagnostic process were explored, and lessons learned from utilizing next-generation diagnostic technologies have been reported.ResultsFive pediatric cases (3 boys, 2 girls) with dual diagnoses were reported. The age at diagnosis was from 3 months to 10 years. The main clinical presentations were psychomotor retardation and increased muscular tension, some accompanied with liver dysfunction, abnormal appearance, precocious puberty, dorsiflexion restriction and varus of both feet, etc. After whole-exome sequencing, nine diseases were confirmed in these patients: Angelman syndrome and Krabbe disease in case 1, Citrin deficiency and Kabuki syndrome in case 2, Homocysteinemia type 2 and Copy number variant in case 3, Isolated methylmalonic acidemia and Niemann-Pick disease type B in case 4, Isolated methylmalonic acidemia and 21-hydroxylase deficiency in case 5. Fifteen gene mutations and 2 CNVs were identified. Four novel mutations were observed, including c.15292de1A in KMT2D, c.159_164inv and c.1427G > A in SLC25A13, and c.591 C > G in MTHFR.ConclusionsOur findings underscore the importance of clinicians being vigilant about the significance of historical and physical examination. Comprehensive clinical experience is crucial for identifying atypical clinical features, particularly in cases involving dual rare genetic diseases.