AAV-mediated gene therapy for sialidosis.

Sialidosis (mucolipidosis I) is a glycoprotein storage disease, clinically characterized by a spectrum of systemic and neurological phenotypes. The primary cause of the disease is deficiency of the lysosomal sialidase NEU1, resulting in accumulation of sialylated glycoproteins/oligosaccharides in tissues and body fluids. Neu1-/- mice recapitulate the severe, early-onset forms of the disease, affecting visceral organs, muscles, and the nervous system, with widespread lysosomal vacuolization evident in most cell types. Sialidosis is considered an orphan disorder with no therapy currently available. Here, we assessed the therapeutic potential of AAV-mediated gene therapy for the treatment of sialidosis. Neu1-/- mice were co-injected with two scAAV2/8 vectors, expressing human NEU1 and its chaperone PPCA. Treated mice were phenotypically indistinguishable from their WT controls. NEU1 activity was restored to different extent in most tissues, including the brain, heart, muscle, and visceral organs. This resulted in diminished/absent lysosomal vacuolization in multiple cell types and reversal of sialyl-oligosacchariduria. Lastly, normalization of lysosomal exocytosis in the cerebrospinal fluids and serum of treated mice, coupled to diminished neuroinflammation, were measures of therapeutic efficacy. These findings point to AAV-mediated gene therapy as a suitable treatment for sialidosis and possibly other diseases, associated with low NEU1 expression.

Unique clinical and electrophysiological features in the peripheral nerve system in patients with sialidosis - a case series study.

BACKGROUND: To investigate the peripheral nervous system involvement in S sialidosis with typical features of myoclonus, seizure, and giant waves in somatosensory evoked potentials suggesting hyperexcitability in the central nervous system. METHODS: The clinical presentation of patients with genetically confirmed sialidosis was recorded. Neurophysiological studies, including nerve conduction studies (NCSs), F-wave studies, and needle electromyography (EMG), were performed on these patients. RESULTS: Six patients (M/F: 2:4) were recruited. In addition to the classical presentation, intermittent painful paresthesia was noted in four patients, and three of whom reported it as the earliest symptom. In the NCSs, one patient had reduced compound muscle action potential amplitudes in the right ulnar nerve, while another patient had prolonged distal motor latency in the bilateral tibial and peroneal nerves. Prolonged F-wave latency (83.3%), repeater F-waves (50%), and neurogenic polyphasic waves in EMG (in 2 out of 3 examined patients) were also noted. Interestingly, a very late response was noted in the F-wave study of all patients, probably indicating lesions involving the proximal peripheral nerve or spinal cord. CONCLUSION: In addition to the central nervous system, the peripheral nervous system is also involved in sialidosis, with corresponding clinical symptoms. Further study on these phenomena is indicated.

Clinical and Structural Characteristics of NEU1 Variants Causing Sialidosis Type 1.

OBJECTIVE: Sialidosis type 2 has variants that are both catalytically inactive (severe), while sialidosis type 1 has at least one catalytically active (mild) variant. This study aimed to discuss the structural changes associated with these variants in a newly reported family carrying N-acetyl-α-neuraminidase-1 (NEU1) variants and explore the clinical characteristics of different combinations of variants in sialidosis type 1. METHODS: First, whole-exome sequencing and detailed clinical examinations were performed on the family. Second, structural analyses, including assessments of energy, flexibility and polar contacts, were conducted for several NEU1 variants, and a sialidase activity assay was performed. Third, previous NEU1 variants were systematically reviewed, and the clinical characteristics of patients in the severe-mild and mild-mild groups with sialidosis type 1 were analyzed. RESULTS: We report a novel family with sialidosis type 1 and the compound heterozygous variants S182G and V143E. The newly identified V143E variant was predicted to be a mild variant through structural analysis and was confirmed by a sialidase activity assay. Cherry-red spots were more prevalent in the severe-mild group, and ataxia was more common in the mild-mild group. Impaired cognition was found only in the severe-mild group. Moreover, patients with cherry-red spots and abnormal electroencephalographies and visual evoked potentials had a relatively early age of onset, whereas patients with myoclonus had a late onset. CONCLUSION: Changes in flexibility and local polar contacts may be indicators of NEU1 pathogenicity. Sialidosis type 1 can be divided into two subgroups according to the variant combinations, and patients with these two subtypes have different clinical characteristics.

Juvenile sialidosis: a rare case and review of the literature.

Background: Sialidosis is a rare variety of lysosomal storage disease that results in intracellular accumulation of sialic acid containing compounds. The authors report the first case of type II sialidosis, juvenile subtype in a 30-month-old male child from Nepal. Case presentation: Progressive hearing loss with coarse facies, hepatomegaly, kyphoscoliosis, dysostosis multiplex were the major features in a 30-month-old child born to healthy non-consanguineous parents. With the suspicion of lysosomal storage disease, urinary oligosaccharides were tested and were positive. Whole-exome sequencing revealed a mutation in the neuraminidase gene (NEU1) and established the diagnosis of sialidosis. Clinical discussion: Sialidosis is a rare autosomal recessive type of lysosomal storage disease resulting due to mutation of the neuraminidase gene leading to intracellular accumulation of sialic acid compounds. Based on the presence of visual symptoms, sialidosis is classified into type I and II varieties. Our case is of type II juvenile sialidosis. Conclusion: Despite rare, sialidosis is a life-threatening, and disabling disease. Exploring targeted therapy is the utmost to treat this condition.

Meta-analysis of the correlation between ocular and neurological manifestations in 43 Chinese children with sialidosis type I / 中华眼底病杂志

Objective:To investigate the correlation between macular cherry red spot (CS) and severity of neurological manifestations in Chinese children with sialidosis (SD) type I.Methods:A evidence-based medical study. "China", "Sialidosis" and "Sialidoses" were used as Chinese and English search terms. The literature was searched in CNKI, Wanfang and PubMed. The cases were all from China and matched the diagnostic criteria. According to the presence or absence of CS in the fundus, the SD children were divided into a group with CS (+) and a group without CS (-), and the correlation between the occurrence of ocular CS and neurological manifestations was compared with meta-analysis by RevMan 5.3 software.Results:Sixty-eight studies were initially retrieved according to the search strategy, and 17 studies were finally included, and 5 studies with CS+ and CS- were meta-analyzed. Among the 43 patients, 28 were male and 15 were female, with a median age of 12 years. Visual impairment was observed in 37 cases (90.2%, 37/41, 2 cases not recorded), and CS was present in 24 cases (55.8%, 24/43). The most common neurological manifestation was myoclonus (97.7%, 42/43), followed by cerebellar ataxia (95.1%, 39/41, 2 cases not recorded) and seizures (91.4%, 32/35, 8 cases not recorded). Pathogenic NEU1 gene mutations were detected in 42 cases and one case was undocumented. The incidence of seizure in group CS+ (100%, 20/20) was higher than that in group CS- (80%, 12/15). Meta-analysis showed that there was no statistically significant difference between the incidence of myoclonus or ataxia [relative risk ( RR)=1.13, 95% confidence interval ( CI) 0.79-1.63, P=0.49] and seizure ( RR=1.13, 95% CI 0.84-2.06, P=0.24) among the children in the CS+ and CS- groups. Conclusions:The incidence of ocular CS in Chinese children with type I SD was 55.8%. There was no correlation with neurological manifestations, however the incidence of seizure was significantly higher in patients with CS than in others without CS.

A novel spot mutation leading to sialidosis type 1-myoclonus syndrome and optical coherence tomography findings / Uma nova mutação pontual levando à sialidose tipo 1 - síndrome mioclônica e seus achados na tomografia de coerência óptica

ABSTRACT This report presents the optical coherence tomography findings and a new NEU1 mutation in bilateral macular cherry-red spot syndrome associated with sialidosis type 1. A 19-year-old patient with a macular cherry-red spot underwent metabolic and genetic analyses supported by spectral-domain optical coherence tomography. Fundus examination revealed bilateral macular cherry-red spot. Spectral-domain optical coherence tomography revealed increased hyperreflectivity in the retinal inner layers and the photoreceptor layer in the foveal region. The genetic analysis detected a new NEU1 mutation, which caused type I sialidosis. In cases with a macular cherry-red spot, sialidosis should be included in the differential diagnosis, and NEU1 mutation should be screened. Spectral-domain optical coherence tomography alone is not sufficient in the differential diagnosis because childhood metabolic diseases may exhibit similar signs.

RESUMO Neste artigo, objetivamos apresentar os achados da tomografia de coerência óptica em uma nova mutação detectada no gene NEU1 em um caso de síndrome macular vermelho-cereja bilateral associada à sialidose tipo 1. Um paciente de 19 anos com um achado de mancha macular vermelho-cereja foi submetido a análises metabólicas e genéticas, apoiadas por imagens de tomografia de coerência óptica de domínio espectral (SD-OCT). Ao exame de fundo de olho, foi observada uma mancha macular vermelho-cereja bilateral. Nas imagens de SD-OCT, observou-se hiper-refletividade nas camadas internas da retina e na camada fotorreceptora na região foveal. Foi realizada uma análise genética e uma nova mutação foi detectada no gene NEU1, resultando em sialidose tipo 1. Nos casos em que é detectada uma mancha vermelho-cereja na mácula, o diagnóstico diferencial de sialidose deve ser feito e mutações do gene NEU1 devem ser rastreadas. A SD-OCT por si só não é suficiente para o diagnóstico diferencial, porque achados de aparência semelhante podem se manifestar em casos de doenças metabólicas da infância.

Lysosomal sialidase NEU1, its intracellular properties, deficiency, and use as a therapeutic agent.

Neuraminidase 1 (NEU1) is a lysosomal sialidase that cleaves terminal α-linked sialic acid residues from sialylglycans. NEU1 is biosynthesized in the rough endoplasmic reticulum (RER) lumen as an N-glycosylated protein to associate with its protective protein/cathepsin A (CTSA) and then form a lysosomal multienzyme complex (LMC) also containing ß-galactosidase 1 (GLB1). Unlike other mammalian sialidases, including NEU2 to NEU4, NEU1 transport to lysosomes requires association of NEU1 with CTSA, binding of the CTSA carrying terminal mannose 6-phosphate (M6P)-type N-glycan with M6P receptor (M6PR), and intralysosomal NEU1 activation at acidic pH. In contrast, overexpression of the single NEU1 gene in mammalian cells causes intracellular NEU1 protein crystallization in the RER due to self-aggregation when intracellular CTSA is reduced to a relatively low level. Sialidosis (SiD) and galactosialidosis (GS) are autosomal recessive lysosomal storage diseases caused by the gene mutations of NEU1 and CTSA, respectively. These incurable diseases associate with the NEU1 deficiency, excessive accumulation of sialylglycans in neurovisceral organs, and systemic manifestations. We established a novel GS model mouse carrying homozygotic Ctsa IVS6 + 1 g/a mutation causing partial exon 6 skipping with simultaneous deficiency of Ctsa and Neu1. Symptoms developed in the GS mice like those in juvenile/adult GS patients, such as myoclonic seizures, suppressed behavior, gargoyle-like face, edema, proctoptosis due to Neu1 deficiency, and sialylglycan accumulation associated with neurovisceral inflammation. We developed a modified NEU1 (modNEU1), which does not form protein crystals but is transported to lysosomes by co-expressed CTSA. In vivo gene therapy for GS and SiD utilizing a single adeno-associated virus (AAV) carrying modNEU1 and CTSA genes under dual promoter control will be created.

Severe dilated cardiomyopathy as an unusual clinical presentation in an infant with sialidosis type II.

We report a unique case of an infant with a severe dilated cardiomyopathy as the clinical presentation of sialidosis type II (OMIM 256550), a rare autosomal recessive inherited lysosomal storage disease that is characterized by partial or complete deficiency of α-neuraminidase, following mutations in the gene neuraminidase 1 (NEU1), located on the short arm of chromosome 6 (6p21.3). Accumulation of metabolic intermediates leads to severe morbidity, especially myoclonus, gait disturbances, cherry-red macules with secondary loss of visual acuity, impaired color vision and night blindness, and sometimes additional neurological findings such as seizures. Dilated cardiomyopathies are characterized by dilation and impaired contraction of the left or both ventricles, whereas most of the metabolic cardiomyopathies are hypertrophic forms appearing with diastolic dysfunction and, in case of lysosomal storage diseases, often associated with valvular thickening and prolapse. Cardiac manifestations in systemic storage disorders are common although rarely described in mucolipidoses. In mucolipidosis type 2 or I-cell disease only three cases were presented with severe dilated cardiomyopathy and endocardial fibroelastosis in infancy, as opposed to sialidosis type II, by which to the best of our knowledge no presentation of dilated cardiomyopathy was previously reported in literature.

A case of nephrosialidosis caused by mutation of neuraminidase 1 gene / 中华肾脏病杂志

The child was a 9-year-old girl, and sought medical advice due to "proteinuria for over a month". Renal biopsy result showed focal segmental glomerulosclerosis with diffuse vacuolization of glomerular podocytes and tubular epithelial cells. The child was diagnosed as type Ⅱ sialidosis with a compound heterozygote mutation in neuraminidase 1 gene for c.239C>T(p.Pro80Leu), c.220G>C(p.Val74Leu) and c.205A>G(p.Arg69Gly). Her father was proved to carry the first mutation, and her mother carried the other two, respectively. The report aims to improve the clinician's understanding of the rare disease. Early diagnosis can help avoid overuse of immunosuppressants, guide treatment reasonably and improve prognosis.

Fluorescent In Situ Staining and Flow Cytometric Procedures as New Pre-Diagnostic Tests for Sialidosis, GM1 Gangliosidosis and Niemann-Pick Type C.

BACKGROUND: Early diagnosis is essential in the field of lysosomal storage disorders for the proper management of patients and for starting therapies before irreversible damage occurs, particularly in neurodegenerative conditions. Currently, specific biomarkers for the diagnosis of lysosomal storage disorders are lacking in routine laboratory practice, except for enzymatic tests, which are available only in specialized metabolic centers. Recently, we established a method for measuring and verifying changes in GM1 ganglioside levels in peripheral blood lymphocytes in patients with GM1 gangliosidosis. However, fresh blood is not always available, and using frozen/thawed lymphocytes can lead to inaccurate results. METHODS: We used frozen/thawed fibroblasts obtained from stored biopsies to explore the feasibility of fluorescent imaging and flow-cytometric methods to track changes in storage materials in fibroblasts from patients with three lysosomal neurodegenerative conditions: GM1 gangliosidosis, Sialidosis, and Niemann-Pick type C. We used specific markers for each pathology. RESULTS AND CONCLUSIONS: We demonstrated that with our methods, it is possible to clearly distinguish the levels of accumulated metabolites in fibroblasts from affected and unaffected patients for all the three pathologies considered. Our methods proved to be rapid, sensitive, unbiased, and potentially applicable to other LSDs.

NEU1-A Unique Therapeutic Target for Alzheimer's Disease.

Neuraminidase 1 (NEU1) is considered to be the most abundant and ubiquitous mammalian enzyme, with a broad tissue distribution. It plays a crucial role in a variety of cellular mechanisms. The deficiency of NEU1 has been implicated in various pathological manifestations of sialidosis and neurodegeneration. Thus, it is a novel therapeutic target for neurodegenerative changes in the Alzheimer's brain. However, to manipulate NEU1 as a therapeutic target, it is imperative to understand that, although NEU1 is commonly known for its lysosomal catabolic function, it is also involved in other pathways. NEU1 is involved in immune response modulation, elastic fiber assembly modulation, insulin signaling, and cell proliferation. In recent years, our knowledge of NEU1 has continued to grow, yet, at the present moment, current data is still limited. In addition, the unique biochemical properties of NEU1 make it challenging to target it as an effective therapeutic option for sialidosis, which is a rare disease but has an enormous patient burden. However, the fact that NEU1 has been linked to the pathology of Alzheimer's disease, which is rapidly growing worldwide, makes it more relevant to be studied and explored. In the present study, the authors have discussed various cellular mechanisms involving NEU1 and how they are relevant to sialidosis and Alzheimer's disease.

Myoclonus generators in sialidosis.

Objective: Sialidosis is an inborn error of metabolism. There is evidence that the myoclonic movements observed in this disorder have a cortical origin, but this mechanism does not fully explain the bilaterally synchronous myoclonus activity frequently observed in many patients. We present evidence of a subcortical basis for synchronous myoclonic phenomena. Methods: Electromyographic investigations were undertaken in two molecularly and biochemically confirmed patients with sialidosis type-1. Results: The EMG recordings showed clear episodes of bilaterally synchronous myoclonic activity in contralateral homologous muscles. We also observed a high muscular-muscular coherence with near-zero time-lag between these muscles. Conclusion: The absence of coherence phase lag between the right-and-left homologous muscles during synchronous events indicates that a unilateral cortical source cannot fully explain the myoclonic activity. There must exist a subcortical mechanism for bilateral synchronization accounting for this phenomenon. Significance: Understanding this mechanism may illuminate cortical-subcortical relationships in myoclonus.

Ascites in infantile onset type II Sialidosis.

Sialidosis is a rare autosomal-recessive lysosomal storage disease due to mutations in the NEU1 gene leading to a deficit of alpha-n-acetyl neuraminidase and causing aberrant accumulation of sialylated glycoproteins/peptides and oligosaccharides in the lysosomes of various organs and tissues. Type II sialidosis (dysmorphic form) is classified into three subgroups based on the age of onset and the clinical severity: Congenital or neonatal, infantile (onset 0-12 months) and juvenile form (onset 13 months-20 years). We report the case of a 3-year-old boy with sialidosis type II infantile form, who developed a voluminous ascites. To the best of our knowledge, ascites is not described in the infantile form but in the congenital form of the disease. Ascites seems to be of a multifactorial origin regarding our investigations: on the one hand, portal hypertension and on the other hypoalbuminemia maintained by proteinuria secondary to nephrosialidosis. Loss of plasma proteins in the gastrointestinal tract (protein-losing enteropathy) should also be considered in the case of portal hypertension and damages of the reticuloendothelial system.

Hematopoietic cell transplantation for sialidosis type I.

We report the clinical and laboratory follow-up data of an adolescent female with Type I Sialidosis who underwent bone marrow transplant (BMT). After BMT, plasma and urine biomarkers responded concurrently with engraftment. Neuropsychiatry data showed preservation in some domains, but she did have overall decline in motor performance. Sialidosis is a very rare lysosomal condition, and we believe this to be the first report of a case of Type I Sialidosis undergoing BMT.

Neurophysiolgical implications in sialidosis type 1: a case report.

Sialidosis is a rare autosomal recessive hereditary disease caused by NEU1 gene mutations. A 25-year-old woman developed generalized tonic-clonic seizures since teenage, followed by progressive visional decline and limb myoclonus. Her sister had similar presentations. Both patients were products of a consanguineous marriage. Electroencephalography (EEG) revealed extensive paroxysmal spiky beta brush. Somatosensory evoked potentials (SEP) after stimulation of median nerves demonstrated giant SEP and C-reflex support the cortical origin of myoclonus. Genetic tests confirmed that both sisters carried the known pathogenic homozygous mutation of c.544A > G in exon 3 of the NEU1 gene. The diagnosis of sialidosis type 1 was then made. This suggests that neurophysiological abnormalities, especially spiky beta brush on EEG, might facilitate the early diagnosis of sialidosis type 1.

Recent advance in sialidosis / 中华神经医学杂志

Sialidosis is a rare autosomal recessive genetic disorder, and has a series of clinical symptoms and signs caused by neuraminidase 1 ( NEU1) gene mutations. This article reviews the etiology, clinical features, diagnoses, treatments and prognoses of sialidosis in order to improve the understanding and diagnosis of this disease and reduce the misdiagnosis of this disease.

Clinical Exome Sequencing Enables Congenital Sialidosis Type II Diagnosis in Two Siblings Presenting with Unreported Clinical Features from a Rare Homozygous Sequence Variant p.(Tyr370Cys) in NEU1.

Sialidosis is a rare autosomal recessive disease that presents with progressive lysosomal storage of sialylated glycopeptides and oligosaccharides caused by homozygous or compound heterozygous sequence variants in the neuraminidase 1 (NEU1) gene. These sequence variants can lead to sialidosis type I and II; the latter is the most severe and presents prenatally or at early age. However, sialidosis diagnosis is challenging, especially in those health systems with limited resources of developing countries. Consequently, it is necessary to dip into high-throughput molecular diagnostic tools to allow for an accurate diagnosis with better cost-effectiveness and turnaround time. We report a 4-member pedigree segregating an ultrarare missense variant, c.1109A>G; p.Tyr370Cys, in NEU1 as detected by whole-exome sequencing. Two short-lived siblings, who presented with previously unreported clinical features from such a homozygous sequence variant, were diagnosed with sialidosis type II. Additionally, we present a novel molecular model exhibiting the consequences of the variant in the sialidase-1 tridimensional structure. This study allowed us to provide a definitive diagnosis for our patients, increase our understanding of this pathogenic variant, and improve genetic counseling.

Prospects for the use of indicators of sialic acid metabolism in medicine (review of literature).

Sialic acids (SA) determine the degree of molecular hydrophilia, relieve binding together and their transportation, they increase mucin viscosity, stabilize the protein and membrane structure. Apart from that, SA are structural components of gangliosides participating in the formation of the outer layer of the plasma membrane. The degree of silyliation of glycoproteins and glycolipids is an important factor of molecular recognition in the cell, between the cells, between a cell and territorial matrix, as well as between a cell and some outer pathogenic factors. They can either mask the sites of recognition or be determinants of recognition. The most well-studied enzymes taking part in the SA metabolism and sialo-containing compounds are N-acetylneuraminate, cythydiltransferase, sialyltransferase, sialydase, aldolase SA and sialyl-O-acetylesterase. Numerous investigations have shown that aberrant sialylation is a specific feature of various changes and disorders of metabolism. Besides that, sialic acids are the first point of contact for different pathogenic microorganisms and the host's body due to their presence on the external surface of the cells and tissue of the mucous membrane. That is why the study of the above-mentioned various sialic acids fractions as well as of the activity of the enzymes participating in their metabolism in the blood plasma and tissues, and of the influence on the activity of these enzymes with the help of medicine can make an essential contribution to the diagnosis and treatment of many diseases.

Modeling Sialidosis with Neural Precursor Cells Derived from Patient-Derived Induced Pluripotent Stem Cells.

Sialidosis, caused by a genetic deficiency of the lysosomal sialidase gene (NEU1), is a systemic disease involving various tissues and organs, including the nervous system. Understanding the neurological dysfunction and pathology associated with sialidosis remains a challenge, partially due to the lack of a human model system. In this study, we have generated two types of induced pluripotent stem cells (iPSCs) with sialidosis-specific NEU1G227R and NEU1V275A/R347Q mutations (sialidosis-iPSCs), and further differentiated them into neural precursor cells (iNPCs). Characterization of NEU1G227R- and NEU1V275A/R347Q- mutated iNPCs derived from sialidosis-iPSCs (sialidosis-iNPCs) validated that sialidosis-iNPCs faithfully recapitulate key disease-specific phenotypes, including reduced NEU1 activity and impaired lysosomal and autophagic function. In particular, these cells showed defective differentiation into oligodendrocytes and astrocytes, while their neuronal differentiation was not notably affected. Importantly, we found that the phenotypic defects of sialidosis-iNPCs, such as impaired differentiation capacity, could be effectively rescued by the induction of autophagy with rapamycin. Our results demonstrate the first use of a sialidosis-iNPC model with NEU1G227R- and NEU1V275A/R347Q- mutation(s) to study the neurological defects of sialidosis, particularly those related to a defective autophagy-lysosome pathway, and may help accelerate the development of new drugs and therapeutics to combat sialidosis and other LSDs.

Anesthetic management for mastectomy and total hysterectomy in a 49-year-old woman with type 1 sialidosis: a case report.

BACKGROUND: Sialidosis is an autosomal recessive glycoprotein storage disorder, caused by neuraminidase deficiency which leads to abnormal intracellular accumulation and urinary excretion of sialylated oligosaccharides, resulting in various morphological and functional disorders. Only a few reports have described the anesthetic managements of patients with sialidosis. CASE PRESENTATION: A 49-year-old woman with type 1 sialidosis suffered from all limb contractures, an ocular cherry-red spot, and myoclonic seizures of the limbs. She had been cognitively normal. She was separately scheduled for mastectomy under total intravenous anesthesia and total hysterectomy under combined general and epidural anesthesia uneventfully. CONCLUSIONS: Our patient with type 1 sialidosis received both general and epidural anesthesia uneventfully. Anesthesiologists should carefully assess patients with sialidosis and give careful consideration to individually tailored anesthetic managements.