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Lysosome-related organelles (LROs) are a group of functionally diverse, cell type-specific compartments. LROs include melanosomes, alpha and dense granules, lytic granules, lamellar bodies and other compartments with distinct morphologies and functions allowing specialised and unique functions of their host cells. The formation, maturation and secretion of specific LROs are compromised in a number of hereditary rare multisystem disorders, including Hermansky-Pudlak syndromes, Griscelli syndrome and the Arthrogryposis, Renal dysfunction and Cholestasis syndrome. Each of these disorders impacts the function of several LROs, resulting in a variety of clinical features affecting systems such as immunity, neurophysiology and pigmentation. This has demonstrated the close relationship between LROs and led to the identification of conserved components required for LRO biogenesis and function. Here, we discuss aspects of this conserved machinery among LROs in relation to the heritable multisystem disorders they associate with, and present our current understanding of how dysfunctions in the proteins affected in the disease impact the formation, motility and ultimate secretion of LROs. Moreover, we have analysed the expression of the members of the CHEVI complex affected in Arthrogryposis, Renal dysfunction and Cholestasis syndrome, in different cell types, by collecting single cell RNA expression data from the human protein atlas. We propose a hypothesis describing how transcriptional regulation could constitute a mechanism that regulates the pleiotropic functions of proteins and their interacting partners in different LROs. [ABSTRACT FROM AUTHOR]

Abstract Background Arthrogryposis-Renal dysfunction-Cholestasis syndrome (ARC, MIM#208085) is a rare multisystem disease due to mutations in the VPS33B and VIPAR genes, both involved in maintaining apical-basolateral cell polarity. The correlation between mutations and phenotype in the ARC Syndrome is not well described. We report on a 6 year old patient who presented with severe renal Fanconi as first manifestation of ARC related to a combined de novo mutation in the VPS33B gene. Case presentation A 6 year old girl presented during the first year of life with severe renal Fanconi as the first manifestation of ARC-Syndrome. This case presents all defining features of ARC syndrome (including liver, skin and articular manifestations) with predominantly renal impairment at presentation. This novel mutation may be associated with a pronounced renal phenotype in ARC. Furthermore, we report on the successful use of LDL-Apheresis and biliodigestive derivation for treatment of cholestatic pruritus with encouraging results. Conclusion ARC is a heterogeneous disorder with early mortality. This case report contributes to a better understanding of this rare disorder, describes a novel mutation in the VPS33B gene and presents an innovative rescue treatment approach.

Arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome is a rare autosomal recessive multisystemic disease that is associated with the liver, kidney, skin, and central nervous and musculoskeletal systems. ARC occurs as a result of mutations in the VPS33B (Vacuolar protein sorting 33 homolog B) or VIPAR (VPS33B interacting protein, apical-basolateral polarity regulator) genes. A female infant presented with neonatal cholestasis with a severe clinical outcome. She was diagnosed with ARC syndrome using targeted exome sequencing (TES). Exome sequencing revealed compound heterozygous mutations, c.707A>T and c.239+5G>A, in VPS33B, where c.707A>T was a novel variant; the resultant functional protein defects were predicted via in silico analysis. c.239+5G>A, a pathogenic mutation that affects splicing, is found in less than 0.1% of the general population. Invasive techniques, such as liver biopsies, did not contribute to a differential diagnosis of ARC syndrome; thus, early TES together with clinical presentations constituted an apparently accurate diagnostic procedure. [ABSTRACT FROM AUTHOR]

Intrahepatic cholestasis is characterized by the accumulation of compounds in the serum that are normally secreted by hepatocytes into the bile. Genes associated with familial intrahepatic cholestasis (FIC) include ATP8B1 (FIC1), ABCB11 (FIC2), ABCB4 (FIC3), TJP2 (FIC4), NR1H4 (FIC5) and MYO5B (FIC6). With advanced genome sequencing methodologies, additional mutated genes are rapidly identified in patients presenting with idiopathic FIC. Notably, several of these genes, VPS33B, VIPAS39, SCYL1, and AP1S1, together with MYO5B, are functionally associated with recycling endosomes and/or the Golgi apparatus. These are components of a complex process that controls the sorting and trafficking of proteins, including those involved in bile secretion. These gene variants therefore suggest that defects in intracellular trafficking take a prominent place in FIC. Here we review these FIC-associated trafficking genes and their variants, their contribution to biliary transporter and canalicular protein trafficking, and, when perturbed, to cholestatic liver disease. Published variants for each of these genes have been summarized in table format, providing a convenient reference for those who work in the intrahepatic cholestasis field.

Mutations in VPS33B and VIPAS39 cause the severe multisystem disorder A rthrogryposis, R enal dysfunction and C holestasis (ARC) syndrome. Amongst other symptoms, patients with ARC syndrome suffer from severe ichthyosis. Roles for VPS33B and VIPAR have been reported in lysosome-related organelle biogenesis, integrin recycling, collagen homeostasis and maintenance of cell polarity. Mouse knockouts of Vps33b or Vipas39 are good models of ARC syndrome and develop an ichthyotic phenotype. We demonstrate that the skin manifestations in Vps33b and Vipar deficient mice are histologically similar to those of patients with ARC syndrome. Histological, immunofluorescent and electron microscopic analysis of Vps33b and Vipar deficient mouse skin biopsies and isolated primary cells showed that epidermal lamellar bodies, which are essential for skin barrier function, had abnormal morphology and the localisation of lamellar body cargo was disrupted. Stratum corneum formation was affected, with increased corneocyte thickness, decreased thickness of the cornified envelope and reduced deposition of lipids. These defects impact epidermal homeostasis and lead to abnormal barrier formation causing the skin phenotype in Vps33b and Vipar deficient mice and patients with ARC syndrome. [ABSTRACT FROM AUTHOR]

VPS33B and VIPAR comprise the two known components of the recently christened class C Homologues in Endosome-Vesicle Interaction ( CHEVI) complex, thought to act as a tethering complex in endosomal trafficking distinct from the HOPS and CORVET complexes in mammalian cells. A recent paper in The Journal of Pathology further explores the role of the CHEVI complex in the biogenesis of α-granules in megakaryocytes, identifying two novel interactors of this complex: α-tubulin and SEC22B, and demonstrating that VPS33B expression is required for the localization of SEC22B and the α-granule cargo VWF to proplatelets in megakaryocytes. These findings advance the current knowledge of the function of the CHEVI complex in α-granule biogenesis and together with studies in other systems, corroborate its role in the specialized delivery of cargo in different cell types. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome is a rare but fatal autosomal recessive multisystem disorder caused by mutations in the VPS33B or VIPAR gene. The classical presentation of ARC includes congenital joint contractures, renal tubular dysfunction, and cholestasis. Additional features include ichthyosis, central nervous system malformation, platelet anomalies, and severe failure to thrive. Diagnosis of ARC syndrome relies on clinical features, organ biopsy, and mutational analysis. However, no specific treatment currently exists for this syndrome. Conclusion This is an overview of the latest knowledge regarding the genetic features and clinical manifestations of ARC syndrome. Greater awareness and understanding of this syndrome should allow more timely intervention with potential for improving long-term outcome. [ABSTRACT FROM AUTHOR]

Background Arthrogryposis, renal dysfunction and cholestasis (ARC) syndrome is a multisystem autosomal-recessive disorder caused by defects in the VPS33B and VIPAR genes, involved in localization of apical membrane proteins. Affected children usually die by 1 year of age, often secondary to infective complications. The classic renal manifestation previously described in ARC syndrome is proximal–tubular dysfunction. The aim of this study is to gain further insight into the renal manifestations of this syndrome. Methods Clinical review of three cases of ARC syndrome presenting to a tertiary centre. Together with measurement of VPS33B and VIPAR protein expression in the human glomerulus. Results The cases demonstrated severe failure to thrive and in addition to commonly described features profound proteinuria and albuminuria, together with hypoalbuminaemia, suggesting glomerular involvement of this syndrome. Western blotting of conditionally immortalized human glomerular cells and ex vivo immunofluorescent analysis of the human glomerulus revealed that VPS33B and VIPAR were highly expressed in glomerular endothelium, and podocytes, but not in the mesangium. Conclusions ARC syndrome affects the glomerulus as well as the proximal tubule in the kidney. Our molecular studies suggest that both cell types that constitute the glomerular filtration barrier are affected in this condition, providing an explanation for the albuminuria that we have observed in our cases. [ABSTRACT FROM PUBLISHER]

Arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome is a rare autosomal recessive multisystem disorder caused by mutations in vacuolar protein sorting 33 homologue B ( VPS33B) and VPS33B interacting protein, apical-basolateral polarity regulator ( VIPAR). Cardinal features of ARC include congenital joint contractures, renal tubular dysfunction, cholestasis, severe failure to thrive, ichthyosis, and a defect in platelet alpha-granule biogenesis. Most patients with ARC do not survive past the first year of life. We report two patients presenting with a mild ARC phenotype, now 5.5 and 3.5 years old. Both patients were compound heterozygotes with the novel VPS33B donor splice-site mutation c.1225+5G>C in common. Immunoblotting and complementary DNA analysis suggest expression of a shorter VPS33B transcript, and cell-based assays show that c.1225+5G>C VPS33B mutant retains some ability to interact with VIPAR (and thus partial wild-type function). This study provides the first evidence of genotype-phenotype correlation in ARC and suggests that VPS33B c.1225+5G>C mutation predicts a mild ARC phenotype. We have established an interactive online database for ARC (https://grenada.lumc.nl/LOVD2/ARC) comprising all known variants in VPS33B and VIPAR. Also included in the database are 15 novel pathogenic variants in VPS33B and five in VIPAR. Hum Mutat 33:1656-1664, 2012. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Simple Summary: Cholestasis refers to a medical condition in which the liver is not capable of secreting bile. The consequent accumulation of toxic bile components in the liver leads to liver failure. Cholestasis can be caused by mutations in genes that code for proteins involved in bile secretion. Recently mutations in other genes have been discovered in patients with cholestasis of unknown origin. Interestingly, many of these newly discovered genes code for proteins that regulate the intracellular distribution of other proteins, including those involved in bile secretion. This group of genes thus suggests the deregulated intracellular distribution of bile-secreting proteins as an important but still poorly understood mechanism that underlies cholestasis. To expedite a better understanding of this mechanism, we have reviewed these genes and their mutations and we discuss these in the context of cholestasis. Intrahepatic cholestasis is characterized by the accumulation of compounds in the serum that are normally secreted by hepatocytes into the bile. Genes associated with familial intrahepatic cholestasis (FIC) include ATP8B1 (FIC1), ABCB11 (FIC2), ABCB4 (FIC3), TJP2 (FIC4), NR1H4 (FIC5) and MYO5B (FIC6). With advanced genome sequencing methodologies, additional mutated genes are rapidly identified in patients presenting with idiopathic FIC. Notably, several of these genes, VPS33B, VIPAS39, SCYL1, and AP1S1, together with MYO5B, are functionally associated with recycling endosomes and/or the Golgi apparatus. These are components of a complex process that controls the sorting and trafficking of proteins, including those involved in bile secretion. These gene variants therefore suggest that defects in intracellular trafficking take a prominent place in FIC. Here we review these FIC-associated trafficking genes and their variants, their contribution to biliary transporter and canalicular protein trafficking, and, when perturbed, to cholestatic liver disease. Published variants for each of these genes have been summarized in table format, providing a convenient reference for those who work in the intrahepatic cholestasis field. [ABSTRACT FROM AUTHOR]