Epidemiology and Genotyping of Patients with Lysosomal Storage Disease in Malaysia.

Background: Lysosomal storage disorders (LSD) are storage disorders involving malfunction of degradation enzymes in lysosome. More than 50 types of LSD have been discovered, which includes the group of mucopolysaccharidoses (MPS), sphingolipidoses, oligosaccharidoses, mucolipidoses, lipoprotein storage disorders, lysosomal transport defects and neuronal ceroid lipofuscinoses and others. The aims of this study were to calculate the birth prevalence and carrier frequency of LSDs in the Malaysian population; to compare our results with reported epidemiologic data from other populations, and to describe the mutation spectrum in Malaysia. From 2008 to 2017, 2.1% (92/4338) suspected patients were diagnosed with LSD. Results: The prevalence of LSD in Malaysia was 1/231,904 live births. The combined prevalence of MPS was 1/292,401 with its subtype of MPS II presented the highest calculated birth prevalence of 1/221,425. Within the group of sphingolipidoses, the combine prevalence was 1/770,777 with Fabry as the most common disorder with calculated prevalence of 1/193,203 followed by metachromatic leukodystrophy (MLD) (1/494,514). MLD is more common among people of Iban ethnicity with the prevalence of 1/6,981. Pompe and mucolipidoses type II are the less common subtypes of LSD with a prevalence of 1/1,694,634 and 1/2,229,516, respectively.Conclusion: Overall, although the prevalence of LSD in Malaysia may be underestimated, the prevalence of MPS is consistent with other reported in East Asian countries.

Impact of α-synuclein fibrillar strains and β-amyloid assemblies on mouse cortical neurons endo-lysosomal logistics

Endosomal transport and positioning cooperate in the establishment of neuronal compartment architecture, dynamics and function, contributing to neuronal intracellular logistics. Furthermore, endo-lysosomal dysfunction has been identified as a common mechanism in neurodegenerative diseases. Here, we analyzed endo-lysosomal transport when α-synuclein (α-syn) fibrillar polymorphs, β-amyloid (Aβ) fibrils and oligomers were externally applied on primary cultures of mouse cortical neurons. To measure this transport, we used a simple readout based on the spontaneous endocytosis in cultured neurons of fluorescent nanodiamonds, a perfectly stable nano-emitter, and the subsequent automatic extraction and quantification of their directed motions at high-throughput. α-syn fibrillar polymorphs, Aβ fibrils and oligomers induce a two-fold decrease of the fraction of nanodiamonds transported along microtubules, while only slightly reducing their interaction with cortical neurons. This important decrease in moving endosomes is expected to have a huge impact on neuronal homeostasis. We next assessed lysosomes dynamics, using Lysotracker. Neurons exposure to Aβ oligomers led to an increase in the number of lysosomes, a decrease in the fraction of moving lysosome and an increase in their size, reminiscent of that found in APP transgenic model of Alzheimer disease. We then analyzed the effect of α-syn fibrillar polymorphs, Aβ fibrils and oligomers on endosomal and lysosomal transport and quantified directed transport of those assemblies within cortical neurons. We report different impacts on endosomal and lysosomal transport parameters and differences in the trajectory lengths of cargoes loaded with pathogenic protein assemblies. Our results suggest that intraneuronal pathogenic protein aggregates internalization and transport may represent a target for novel neuroprotective therapeutic strategies.

Chediak-Higashi Syndrome in Accelerated Phase, a Case Report

Chediak-Higashi syndrome corresponds to a series of genetic abnormalities in lysosomal transport, of autosomal recessive inheritance, characterized by partial oculocutaneous albinism and recurrent infections,1 usually between 7 and 10 years of age the accelerated phase of the disease, where developing hemophagocytic syndrome, given by a set of clinical findings, laboratory and histological studies where phagocytosis is prominent,2 with a failure in the regulation of the immune system due to an excessive production of pro-inflammatory cytokines that coexists with a dysfunction of natural killer cells and T lymphocytes, which leads to lethal development. We present a case of a 13-month-old patient, natural and from Pregonero, with a family history of consanguinity, recurrent respiratory infections, and a characteristic phenotype of Chediak-Higashi syndrome, without prior diagnosis or controls for this pathology, who presents with hemophagocytic syndrome leading to its death in 20 days.

Continuous transport of a small fraction of plasma membrane cholesterol to endoplasmic reticulum regulates total cellular cholesterol

Cells employ regulated transport mechanisms to ensure that their plasma membranes (PMs) are optimally supplied with cholesterol derived from uptake of low-density lipoproteins (LDL) and synthesis. To date, all inhibitors of cholesterol transport block steps in lysosomes, limiting our understanding of post-lysosomal transport steps. Here, we establish the cholesterol-binding domain 4 of anthrolysin O (ALOD4) as a reversible inhibitor of cholesterol transport from PM to endoplasmic reticulum (ER). Using ALOD4, we: (1) deplete ER cholesterol without altering PM or overall cellular cholesterol levels; (2) demonstrate that LDL-derived cholesterol travels from lysosomes first to PM to meet cholesterol needs, and subsequently from PM to regulatory domains of ER to suppress activation of SREBPs, halting cholesterol uptake and synthesis; and (3) determine that continuous PM-to-ER cholesterol transport allows ER to constantly monitor PM cholesterol levels, and respond rapidly to small declines in cellular cholesterol by activating SREBPs, increasing cholesterol uptake and synthesis.

The Rab7 effector PLEKHM1 binds Arl8b to promote cargo traffic to lysosomes

Endocytic, autophagic, and phagocytic vesicles move on microtubule tracks to fuse with lysosomes. Small GTPases, such as Rab7 and Arl8b, recruit their downstream effectors to mediate this transport and fusion. However, the potential cross talk between these two GTPases is unclear. Here, we show that the Rab7 effector PLEKHM1 simultaneously binds Rab7 and Arl8b, bringing about clustering and fusion of late endosomes and lysosomes. We show that the N-terminal RUN domain of PLEKHM1 is necessary and sufficient for interaction with Arl8b and its subsequent localization to lysosomes. Notably, we also demonstrate that Arl8b mediates recruitment of HOPS complex to PLEKHM1-positive vesicle contact sites. Consequently, Arl8b binding to PLEKHM1 is required for its function in delivery and, therefore, degradation of endocytic and autophagic cargo in lysosomes. Finally, we also show that PLEKHM1 competes with SKIP for Arl8b binding, which dictates lysosome positioning. These findings suggest that Arl8b, along with its effectors, orchestrates lysosomal transport and fusion.

Lysosomal Storage Disorders

Lysosomal storage disorders are characterized by the presence of nondegraded material in endosomal / lysosomal compartments. Any process that interferes with the lysosomal degradation or endosomal / lysosomal transport of molecules can give rise to storage. The cause may be genetic in nature or environmental, as is the case in drug-induced lipidoses or when undegradable materials are present. In this chapter we discuss the genetic lysosomal storage disorders.

First Report ofCTNSMutations in a Chinese Family with Infantile Cystinosis

Infantile cystinosis (IC) is a rare autosomal recessive disorder characterized by a defect in the lysosomal-membrane transport protein, cystinosin. It serves as a prototype for lysosomal transport disorders. To date, severalCTNSmutations have been identified as the cause of the prototypic disease across different ethnic populations worldwide. However, in Asia, theCTNSmutation is very rarely reported. For the Chinese population, no literature onCTNSmutation screening for IC is available to date. In this paper, by using the whole exome sequencing and Sanger sequencing, we identified two novelCTNSsplicing deletions in a Chinese IC family, one at the donor site of exon 6 ofCTNS(IVS6+1, del G) and the other at the acceptor site of exon 8 (IVS8-1, del GT). These data give information for the genetic counseling of the IC that occurred in Chinese population.