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2013 : Understanding a fatal childhood disorder and dissecting biology Mark S. Sands Washington University School of Medicine in St. Louis

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Recommended Citation Sands, Mark S., ,"Farber disease: Understanding a fatal childhood disorder and dissecting ceramide biology." EMBO Molecular Medicine.5,6. 799-801. (2013). https://digitalcommons.wustl.edu/open_access_pubs/1827

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Farber disease: understanding a fatal childhood disorder and dissecting ceramide biology

Mark S. Sands

Keywords: acid ; ceramide; Farber disease; lysosomal storage disease See related article in EMBO Molecular Medicine http://dx.doi.org/10.1002/emmm.201202301

Farber disease (Lipogranulomatosis) is a ease present symptoms by 3–6 months of gest that normal ceramide levels and rare, invariably fatal, inherited metabolic age and die at approximately 2 years of are critical for early embryo- disorder first described by Sidney Farber age. The intermediate/mild form has nic development. in 1957 (Farber et al, 1957). Farber no neurologic component and affected Significant progress has been made disease is inherited in an autosomal patients typically live to 5–7 years of towards effective therapies for LSDs recessive fashion and is caused by age. However, some mild Farber patients through the use of recombinant mutations in the lysosomal acid cerami- live into their teens or early adulthood. replacement, bone marrow transplanta- dase (ASAH1) . Therefore, Farber The pathogenesis of Farber disease is tion (BMT), small molecule drugs and disease is classified as one of the >50 largely unknown. In addition, there is gene therapy. It is likely that Farber distinct lysosomal storage disorders no apparent genotype/phenotype corre- disease would be responsive to similar (LSDs). Acid ceramidase (ACDase) is a lation and little or no correlation between approaches. However, the lack of an soluble lysosomal enzyme responsible authentic animal model of Farber disease for the degradation of ceramide. Low has hindered this research. Thus, there is levels (10% normal) of ACDase activity » This represents a truly no effective therapy currently available result in the progressive accumulation of significant advancement in for Farber disease. ceramide in most tissues. the study of this disorder. In this issue of EMBO Molecular Affected children initially present with « Medicine, Alayoubi et al (2013) describe stiffness and deformation, promi- the development of a ‘knock-in’ mouse nent subcutaneous nodules and progres- ACDase levels and disease severity. This model of Farber disease. This represents sive hoarseness due to laryngeal involve- lack of understanding is due in part to a truly significant advancement in the ment. As the disease progresses affected the small number of patients evaluated study of this disorder. Since no complete children can also develop cardiac, pul- and the imprecision associated with the ASAH1 deletions have been identified monary and central nervous system ACDase assays. to date in Farber patients, the authors defects. Like most LSDs, there is a An authentic small animal model of inserted a homoallelic missense mutation spectrum of severities associated with Farber disease would greatly facilitate (P362R) discovered in a patient with a Farber disease. The most severe neonatal research into disease mechanisms and ‘classical’ Farber disease presentation. form results in death within the first few aid in the development of effective This particular mutation is located within days of life. Children with the most therapies. Unfortunately, a complete the most highly conserved amino acid common, ‘classical’ form of Farber dis- ‘knock-out’ model of Farber disease region of the mouse and human ASAH1 resulted in early embryonic lethality (Li . This mutation results in normal et al, 2002) and a reduction of ACDase levels of protein but <10% normal Departments of Internal Medicine and Genetics, activity in the ovaries of a conditional ACDase activity in an in vitro expression Washington University School of Medicine, St. ‘knock-out’ resulted in oocyte apoptosis assay (Li et al, 1999). Alayoubi et al Louis, MO, USA (Eliyahu et al, 2012). These data highlight (2013) performed a biochemical, histo- Corresponding author: Tel: þ1 314 362 5494; Fax: þ1 314 362 9333; the difficulty in generating mouse models logical, haematological and clinical eva- P361R/P361R E-mail: [email protected] of certain LSDs, in particular the lipid luation of the Asah1 mouse in DOI 10.1002/emmm.201302781 storage disorders. These data also sug- order to determine if this model mimics

ß 2013 The Authors. Published by John Wiley and Sons, Ltd on behalf of EMBO. This is an open access article under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits use, distribution and reproduction in any medium, provided the original work is properly cited. EMBO Mol Med (2013) 5, 799–801 799 Closeup www.embomolmed.org Farber disease and ceramide biology

the human disease. Briefly, the mouse » It will be of great interest metabolism and has been has low levels of ACDase activity, to more thoroughly investigate shown to be involved in tumorigenesis ceramide accumulation in all tissues the effects of lysosomal (Park & Schuchman, 2006). Over expres- assayed (including the brain), histiocytic sion of ACDase has been identified as infiltrations, decreased body weight, ceramide accumulation on the a marker of certain tumours and can shortened life span (median 65 days), animal’s metabolic state, inhibit tumour cell apoptosis. Inhibition impaired ovary development, altered skeletal development, immune of ACDase activity is being actively myeloid parameters, shortened epiphy- system and CNS function. investigated as a possible therapy for seal plates and elevated MCP-1 levels in « certain tumours. The Asah1P361R/P361R liver, spleen, brain and thymus. Finally, mouse will help elucidate the role of the authors demonstrate that the ACDase, ceramide and other sphingoli- Asah1P361R/P361R mice have profound animal model of Farber disease will pids in tumorigenesis and allow thera- hydrocephalus as measured by magnetic allow the investigators to identify new peutic approaches targeted at ACDase resonance imaging. Based on this initial disease mechanisms that can be targeted to be tested in vivo. yet extensive characterization, it is clear either alone or in combination, thus There are a relatively large number of that the ACDase-deficient mouse accu- increasing efficacy (Hawkins-Salsbury functions ascribed directly to ceramide rately models most of the characteristics et al, 2011). and it also serves as the core molecule of the human disease. It will be of great The implications of the Asah1P361R/P361R for a number of , including interest to more thoroughly investigate mouse for understanding the pathogen- and the glycosphingo- the effects of lysosomal ceramide accu- esis of, and developing therapies for lipids (Fig 1). Ceramide has been shown mulation on the animal’s metabolic state, Farber disease are obvious. However, to be a pro-apoptotic molecule. This is skeletal development, immune system, this model also represents a powerful consistent with the oocyte apoptosis and CNS function. tool to aid in the understanding of observed in the conditional Asah1 Not only did Alayoubi et al (2013) ceramide biology. There is a growing ‘knock-out’ described above (Eliyahu create and characterize a mouse model body of literature demonstrating the et al, 2012). Ceramide can also have of Farber disease, in the same report importance of ACDase, ceramide, and direct effects on inflammation, immune they performed an experiment to deter- related lipids in a number of biological function, cardiac function, atherosclero- mine the efficacy of systemic gene processes (Fig 1). ACDase is one of the sis, metabolic abnormalities and differ- therapy for this disease. The authors key regulating ceramide and entiation, just to name a few (Bieberich, injected a lentiviral vector expressing human ACDase intravenously into neo- natal Asah1P361R/P361R mice. This Palmitoyl-CoA + L-Serine approach was chosen for two reasons: (i) Farber disease is progressive and early ACDase treatment will likely be more efficacious Ceramide Tumor marker Synthetic enzymes since it can prevent rather than reverse Tumor resistance pre-existing disease, and (ii) ACDase is a soluble lysosomal enzyme that Farber disease can be secreted from the genetically Ceramide modified cells and taken up by non- Lipid raft integrity Sphingomyelin Inflammation + fatty acid transduced cells through a receptor- Apoptosis mediated mechanism. This has the Metabolic syndrome potential to mediate widespread correc- Differentiation tion of the disease (Sands and Davidson, 2006). The lentiviral-treated mice had significantly increased body weight and life span, improved haematologic para- meters, and nearly normal ceramide levels in the liver and spleen. Unfortu- Figure 1. Acid ceramidase and ceramide actions. Ceramide is a lipid that is sequentially synthesized nately, there was no decrease in ceramide through several reactions starting with palmitoyl-CoA and L-serine. Ceramide is central to the further accumulation in the brain. Although the synthesis of several key membrane lipids such as sphingomyelin and the glycospohingolipids, therapeutic response was only partial, and glucosylceramide. Ceramide has also been shown to be directly involved in a this is an important proof-of-principle number of biological processes, including lipid raft integrity, inflammation, apoptosis, metabolic syndrome and differentiation, just to name a few. Acid ceramidase (ACDase) is a soluble lysosomal enzyme experiment demonstrating the feasibility responsible for the breakdown of ceramide to sphingosine and fatty acid. A deficiency in ACDase activity of this approach and could not have been leads to the accumulation of ceramide in many tissues, the hallmark of Farber disease. Acid ceramidase P361R/P361R performed without the Asah1 has also been shown to be involved in the resistance of certain tumor cells to chemotherapeutic agents mouse. The creation of an accurate small and has been identified as a tumor marker in other malignancies.

800 ß 2013 The Authors. Published by John Wiley and Sons, Ltd on behalf of EMBO. EMBO Mol Med (2013) 5, 799–801 www.embomolmed.org Closeup Mark S. Sands

2012). Although in vitro data suggest that » This animal model will ceramide accumulation leads to severe and lysosomal ceramide accumulation in also provide a new and varied pathological consequences. EMBO Mol cultured Farber cells does not affect Med DOI: 10.1002/emmm.201202301 important tool in the quest Bieberich E (2012) It’s a lipid world: bioactive normal ceramide signalling pathways, it to more fully understand the and signaling in neural stem seems unlikely that the ceramide that cell differentiation. Neurochem Res 37: 1208- accumulates in diseased cells or is complex actions of ceramide 1229 released from dead or dying cells will and sphingolipids. « Eliyahu E, Shtraizent N, Shalgi R, Schuchman EH be completely benign in vivo. Ceramide, (2012) Construction of conditional ceramidase sphingomyelin and the glycosphingoli- knockout mice and in vivo effects on oocyte pids, galactosylceramide and glucosyl- In conclusion, Alayoubi et al (2013) development and fertility. Cell Physiol Biochem 30: 735-748 ceramide, are integral membrane com- thoroughly and convincingly demonstrate Farber S, Cohen J, Uzman LL (1957) ponents that are concentrated in lipid that the mouse model of ACDase defi- Lipogranulomatosis: a new lipo-glyco-protein rafts and are believed to be important for ciency is an accurate phenocopy of Farber ‘‘storage’’ disease. J Mt Sinai Hosp 24: 816-837 both proper raft and non-raft architec- disease and systemic gene therapy may be Hawkins-Salsbury JA, Reddy AS, Sands MS (2011) ture. Sphingomyelin and galactosylcera- part of an effective therapeutic strategy. Combination therapy for lysosomal storage mide are also two of the major compo- This animal model will also provide a new diseases: is the whole greater than the sum of its parts? Hum Mol Genet 20: R54-R60 nents of myelin sheaths surrounding and important tool in the quest to more Li CM, Park JH, He X, Levy B, Chen F, Arai K, Adler axons. Galactosylceramide, in particular, fully understand the complex actions of DA, Disteche CM, Koch J, Sandhoff K, et al (1999) makes up >20% of the total mass of ceramide and sphingolipids. The human acid ceramidase gene (ASAH): myelin lipids. Perturbation of ceramide structure, chromosomal location, mutation levels as a result of altered catabolism by analysis, and expression. Genomics 62: 223-231 ACDase could affect the levels of the Acknowledgements Li CM, Park JH, Simonaro CM, He X, Gordon RE, glycosphingolipids and sphingomyelin, The author is supported by grants from Friedman AH, Ehleiter D, Paris F, Manova K, Hepbildikler S, et al (2002) Insertional and, secondarily membrane integrity, the the National Institutes of Health mutagenesis of the mouse acid ceramidase gene proper functioning of raft- or membrane- (NS043205 and NS084861) and from leads to early embryonic lethality in homozygotes associated proteins, and axonal health. The Legacy of Angels Foundation. The and progressive lipid storage disease in The ACDase-deficient mouse represents author thanks Jacqui Hawkins-Salsbury heterozygotes. Genomics 79: 218-224 an important addition to a growing and Charles Shyng for critical comments Park JH, Schuchman EH (2006) Acid ceramidase number of mouse models that have on the manuscript. and human disease. Biochim Biophys Acta genetic defects affecting sphingolipid 1758: 2133-2138 Sabourdy F, Kedjouar B, Sorli SC, Colie S, Milhas D, metabolism (Sabourdy et al, 2008). These The author declares that he has no Salma Y, Levade T (2008) Functions of models, alone and in combination will conflict of interest. sphingolipid metabolism in mammals—lessons facilitate both the study of the physiolo- from genetic defects. Biochim Biophys Acta gical consequences of lysosomal cera- References 1781: 145-183 mide accumulation and the dissection of Alayoubi AM, Wang JCM, Au BCY, Carpentier S, Sands MS, Davidson BL (2006) Gene therapy for these complex lipid signalling pathways Garcia V, Dworski S, Ghamrasni SE, Kirouac KN, lysosomal storage diseases. Mol Ther 13: 839- in vivo. Exertier J, Xiong ZJ, et al (2013) Systemic 849

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