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Peroxisome Biogenesis Disorders-Zellweger spectrum disorder (PBD-ZSD) is a rare, autosomal recessive peroxisome biogenesis disorder that presents with variable symptoms. In patients with PBD-ZSD, pathogenic variants in the PEX family of genes disrupt normal peroxisomal function, impairing α- and β-oxidation of very-long-chain fatty acids and synthesis of bile acids, resulting in increased levels of toxic bile acid intermediates and multisystem organ damage. The spectrum of severity in PBD-ZSD is variable, with some patients dying in the first year of life, while others live into adulthood. Symptoms of mild PBD-ZSD include various combinations of developmental delay, craniofacial dysmorphic features, visual impairment, sensorineural hearing loss, liver disease, and adrenal insufficiency. Disease progression in mild PBD-ZSD is generally slow, and may include extended periods of stability in some cases. The presence and extent to which symptoms occur in mild PBD-ZSD represents a diagnostic challenge that can cause delays in diagnosis with potential significant implications related to disease monitoring and treatment. There is some support for the pharmacologic therapies of Lorenzo's oil, docosohexanoic acid, and batyl alcohol in altering symptoms; however, systematic long-term studies are lacking. Cholic acid (CA) therapy has demonstrated treatment efficacy in patients with PBD-ZSD, including decreased toxic bile acid intermediates, transaminase levels, and liver inflammation, with improvement in growth parameters. However, these responses are most apparent in patients diagnosed and treated at a young age. Advanced liver disease may limit the efficacy of CA, underscoring the need to diagnose and treat these patients before significant liver damage and other related complications occur. Here we discuss the signs and symptoms of PBD-ZSD in patients with mild disease, standard diagnostic tools, factors affecting disease management, and available pharmacological interventions.

A 5-year-old female patient, presented with"night blindness and poor hearing for 1 year"whose first diagnosis was Usher syndrome due to retinitis pigmentosa accompanied by sensorineural deafness. Compound heterozygous variants (c.5GA, p.W2*/c.3022CT, p.P1008S) of PEX1, the causative gene for Zellweger spectrum disorder was confirmed by targeted exome sequencing analysis. Permanent tooth enamel dysplasia, nail leukoplakia, and biochemical abnormalities of peroxisome which is consistent with mild Zellweger spectrum disorder were found when she followed up.患儿女性，5岁，因“夜盲、听力差1年”就诊，因视网膜色素变性合并感音神经性耳聋，首诊为Usher综合征。目标区域捕获测序分析发现患儿携带Zellweger谱系障碍致病基因PEX1复合杂合变异c.5GA，p.W2*/c.3022CT，p.P1008S。后期随访发现患儿恒牙釉质发育不良，指甲白斑，过氧化物酶体功能生化异常，诊断为轻型Zellweger谱系障碍。.

The article deals with the modern principles for the diagnosis and treatment of peroxisomal biogenesis disorders of Zellweger syndrome spectrum according to the recommendations of the Global Foundation for Peroxisomal Disorders 2016. The authors presented the clinical features of these diseases. The lesions of the nervous, bone, urinary, endocrine, sensory systems and tooth enamel are characteristic signs of the disease. Our own clinical observation on the disturbances of oxidation of very long chain fatty acids in an infant is considered separately. Section of Zellweger spectrum disorders diagnosis is based on world standards for disease diagnosis and includes markers of very long-chain fatty acid β-oxidation, as well as α-oxidation by pristanic and phytanic acids, metabolism of pipecolic acid and other peroxisomal dysfunctions. The final diagnosis of peroxisomal biogenesis disorders in Zellweger syndrome spectrum at the present stage is established by the genetic testing method, ­using the sequencing techniques of the new generation for the PEX genes. The severity of neurological disorders and the progressive course of the disease, as well as emergence of the possibility of treating X-linked adrenoleukodystrophy opened the prospects of screening for X-linked adrenoleukodystrophy based on a combination of liquid chromatography and tandem mass spectrometry to detect the elevated levels of very long-chain fatty acids in newborns in blood spots. Clinical monitoring since diagnosis was established includes correction of initial disturbances and revealing disease symptoms, which appear later.

OBJECTIVES. Peroxisome Biogenesis Disorders in the Zellweger Spectrum (PBD-ZSD) are autosomal recessive disorders characterized by defects in peroxisome function, biosynthesis, and/or assembly. Despite its frequent documentation, hearing loss associated with PBD-ZSD has not been extensively characterized. The purpose of this retrospective natural history study was to better characterize the hearing loss associated with PBD-ZSD and to provide additional insight into the evaluation and management of PBD-ZSD patients with hearing loss. DESIGN. Audiological data from medical records of 42 patients with PBD-ZSD or D-bifunctional protein deficiency were collected from an ongoing longitudinal retrospective natural history study. An initial dataset of 300 audiograms and/or audiometric test results from the 42 patients were used to characterize the degree of hearing loss, type of hearing loss, relationships between air and bone conduction thresholds, age-related changes in hearing loss, and benefit with amplification. RESULTS. The majority of PBD-ZSD patients in this study presented with moderately-severe to severe hearing loss and relatively slow rates of longitudinal changes in hearing sensitivity. Improvements in hearing thresholds were observed with use of hearing aid amplification. Though bone conduction data was limited, air-bone gaps and air conduction threshold fluctuations observed in several patients suggest there may be an increased occurrence of mixed hearing losses in PBD-ZSD populations. CONCLUSION. The results of this retrospective study provide insight into the hearing loss associated with PBD-ZSD, but also emphasize the need for more complete assessments of hearing loss type and middle ear function in these patients. The addition of more comprehensive datasets to the ongoing natural history study will enhance our understanding of the pathophysiology underlying PBD-ZSD and guide the development of targeted evaluation and management recommendations for patients with PBD-ZSD.

To investigate the value of very long chain acylcarnitine (VLCAC) and lysophosphatidylcholine (LPC) in screening of peroxisomal disease in children. Eighteen children with peroxisomal disease, including 14 cases of X-linked adrenoleukodystrophy (X-ALD group) and 4 cases of Zellweger syndrome (ZS group) diagnosed based on clinical symptoms, MRI and genetic tests were enrolled in the study; and 200 healthy children were selected as control group. Samples of dried blood spots were collected from all subjects, VLCAC and LPC in dried blood spots were extracted by solvent containing internal isotopic standards hexacosanoylcarnitine (H-C26) and C26:0 lysophosphatidylcholine (H-C26:0-LPC). The eicosanoylcarnitine (C20), docosanoylcarnitine (C22), tetracosanoylcarnitine (C24), hexacosanoylcarnitine (C26), C20:0 lysophosphatidylcholine (C20:0-LPC), C22:0 lysophosphatidylcholine (C22:0-LPC), C24:0 lysophosphatidylcholine (C24:0-LPC) and C26:0 lysophosphatidylcholine (C26:0-LPC) were detected by tandem mass spectrometry (MS/MS). The above 8 indicators and the ratios were compared among the groups using Kruskal-Wallis test and Mann-Whitney test; the contribution of each index to the disease were analyzed by partial least square method. Except C24:0-LPC/C20:0-LPC, there were significant differences in all indicators and ratios among all groups (

Background Zellweger syndrome (ZS) is commonly manifested as facial deformities, hypotonia, and liver dysfunction. However, ZS caused by PEX26 gene mutation shows a broad and dispersed clinical pattern. In this study, the PEX26 gene in ZS was analyzed to enrich its clinical characteristics. Meanwhile, phenotypic and genotypic characteristics of Zellweger spectrum disorder (ZSD) induced by PEX26 mutation were evaluated. Methods The clinical data of newborn with ZS in our hospital were analyzed retrospectively. We performed WES and found that the infant carried the PEX26 gene variant. We searched the biomedical literature databases (PubMed, Web of Science, and EMBASE) to compare clinical features and genotypes. Results The neonate developed facial deformities, hypotonia, feeding difficulties, and seizures. Her homozygous variant was found in the PEX26 gene (NM_017929: exon2: c.34del) inherited from both parents. Electronic databases, including our case, reported 32 pathogenic variants in PEX26. We found that variation c.292C> T accounted for the largest proportion of PEX26 mutations (16/66, 24.24%). The proportion of deleterious mutations in ZS patients was significantly higher than that in NALD and IRD patients. Conclusions We identified pathogenic variations in the PEX26 gene and expanded the known mutant spectrum. By comparing patients with PEX26 mutations, the study determined that a significantly higher percentage of deleterious mutations in ZS was associated with severe clinical phenotypic characteristics.

In Zellweger syndrome (ZS), lack of peroxisome function causes physiological and developmental abnormalities in many organs such as the brain, liver, muscles, and kidneys, but little is known about the exact pathogenic mechanism. By disrupting the zebrafish pex2 gene, we established a disease model for ZS and found that it exhibits pathological features and metabolic changes similar to those observed in human patients. By comprehensive analysis of the fatty acid profile, we found organ-specific accumulation and reduction of distinct fatty acid species, such as an accumulation of ultra-very-long-chain polyunsaturated fatty acids (ultra-VLC-PUFAs) in the brains of pex2 mutant fish. Transcriptome analysis using microarray also revealed mutant-specific gene expression changes that might lead to the symptoms, including reduction of crystallin, troponin, parvalbumin, and fatty acid metabolic genes. Our data indicated that the loss of peroxisomes results in widespread metabolic and gene expression changes beyond the causative peroxisomal function. These results suggest the genetic and metabolic basis of the pathology of this devastating human disease.

The peroxisome is responsible for a variety of vital pathways in primary metabolism, including the very long-chain fatty-acid oxidation and plasmalogen lipid biosynthesis. Autosomal recessive disorder of the Zellweger spectrum (ZSD) is a major subset of peroxisome biogenesis disorders (PBDs) that can be caused by mutations in any of the 14 PEX genes. Zellweger syndrome (ZS) is the foremost common and severe phenotype within the heterogeneous ZSD. However, missense mutations encode proteins with residual functions, which are associated with phenotypes that are milder than ZS. Mutations in the PEX1 gene are among the most prevalent. PEX1 and PEX6 proteins, belonging to the AAA family of ATPases, form a hexameric complex, which is associated with peroxisome membranes and essential for peroxisome biology. In this study, a two-month-old Iranian boy with hypotonia, poor feeding, and difficulty in breathing was diagnosed with Zellweger syndrome. The parents of the patient were second cousins and healthy and no similar cases were observed in the parents' family. The PEX1 gene was sequenced in the patient and his parents. The compound heterozygous mutations, p. Arg949Trp and p. Gly970Ala, were identified in the patient, while the parents were heterozygous for these alleles. Sequence analysis of the mutant PEX1 D2 domain revealed that mutation p. Arg949Trp precisely occurred in a conserved arginine residue (P4 Arg), which hinders the substrate processing of the complex. Several database records have reported mutation p. Arg949Trp(R949W) but its clinical significance is given as uncertain. We report here a novel mutation, p. Gly970Ala, which is not recorded before and may prevent proper interaction of PEX1 and PEX6 proteins. In summary, the clinical findings and peroxisome profile of the patient suggested that compound heterozygosity for these two missense mutations resulted in a nonfunctional PEX1/PEX6 complex causing the severe ZS phenotype.

Background & Objective:Peroxisome biogenesis disorders (PBDs) are a group of diseases with peroxisomal dysfunction. Wide range of symptoms are associated with the disease which are due to mutations in thePEXgenes. ThePEX1mutation occurs in Zellweger syndrome (ZS), a severe autosomal recessive condition with hypotonia, intellectual disability, and hepatic enlargement. The present study determined the molecular aspects of ZS in a family in South Khorasan Province, Iran. Materials & Methods:Whole-exome sequencing (WES) was performed, clinical history was taken, and the family pedigree was drawn. Subsequently, Sanger sequencing was performed for unique primers. Afterwards, in terms of ZS phenotype, in silico studies were done to examine the changes that occurred in the protein structure. Results:ThePEX1(NC_000007.14) mutation was detected at location Chr7q21.2. This chromosomal location was anticipated as the disorder-causing variant. GGT (Glycine) changes to GAT (Aspartate) in codon 843 were confirmed by Sanger sequencing. Examination results of the mentioned family revealed a missense mutation in thePEX1. Conclusion:In conclusion, our study indicated a mutation in thePEX1in the affected family. This mutation is a missense variant at codon 843 in ZS patients. It has an autosomal recessive inheritance pattern. This mutation may be widespread among Iranian population with ZS and can be used for a more desirable personalized medicine. Keywords:Peroxisomal biogenesis factor,Point mutation,Whole exome sequencing,Zellweger syndrome

Peroxisomal biogenesis disorders (PBDs) are a heterogeneous group of genetic diseases. Multiple peroxisomal pathways are impaired, and very long chain fatty acids (VLCFA) are the first line biomarkers for the diagnosis. The clinical presentation of PBDs may range from severe, lethal multisystemic disorders to milder, late-onset disease. The vast majority of PBDs belong to Zellweger Spectrum Disordes (ZSDs) and represents a continuum of overlapping clinical symptoms, with Zellweger syndrome being the most severe and Heimler syndrome the less severe disease. Mild clinical conditions frequently present normal or slight biochemical alterations, making the diagnosis of these patients challenging. In the present study we used a combined WES and RNA-seq strategy to diagnose a patient presenting with retinal dystrophy as the main clinical symptom. Results showed the patient was compound heterozygous for mutations in PEX1. VLCFA were normal, but retrospective analysis of lysosphosphatidylcholines (LPC) containing C22:0–C26:0 species was altered. This simple test could avoid the diagnostic odyssey of patients with mild phenotype, such as the individual described here, who was diagnosed very late in adult life. We provide functional data in cell line models that may explain the mild phenotype of the patient by demonstrating the hypomorphic nature of a deep intronic variant altering PEX1 mRNA processing.

Background Pathogenic variants in PEX-genes can affect peroxisome assembly and function and cause Zellweger spectrum disorders (ZSDs), characterized by variable phenotypes in terms of disease severity, age of onset and clinical presentations. So far, defects in at least 15 PEX-genes have been implicated in Mendelian diseases, but in some of the ultra-rare ZSD subtypes genotype–phenotype correlations and disease mechanisms remain elusive. Methods We report five families carrying biallelic variants in PEX13. The identified variants were initially evaluated by using a combination of computational approaches. Immunofluorescence and complementation studies on patient-derived fibroblasts were performed in two patients to investigate the cellular impact of the identified mutations. Results Three out of five families carried a recurrent p.Arg294Trp non-synonymous variant. Individuals affected with PEX13-related ZSD presented heterogeneous clinical features, including hypotonia, developmental regression, hearing/vision impairment, progressive spasticity and brain leukodystrophy. Computational predictions highlighted the involvement of the Arg294 residue in PEX13 homodimerization, and the analysis of blind docking predicted that the p.Arg294Trp variant alters the formation of dimers, impairing the stability of the PEX13/PEX14 translocation module. Studies on muscle tissues and patient-derived fibroblasts revealed biochemical alterations of mitochondrial function and identified mislocalized mitochondria and a reduced number of peroxisomes with abnormal PEX13 concentration. Conclusions This study expands the phenotypic and mutational spectrum of PEX13-related ZSDs and also highlight a variety of disease mechanisms contributing to PEX13-related clinical phenotypes, including the emerging contribution of secondary mitochondrial dysfunction to the pathophysiology of ZSDs.

Peroxisomes play an essential role in cellular homeostasis by regulating lipid metabolism and the conversion of reactive oxygen species (ROS). Several peroxisomal proteins, known as peroxins (PEXs), control peroxisome biogenesis and degradation. Various mutations in the PEX genes are genetic causes for the development of inheritable peroxisomal-biogenesis disorders, such as Zellweger syndrome. Among the peroxins, PEX1 defects are the most common mutations in Zellweger syndrome. PEX1 is an AAA-ATPase that regulates the recycling of PEX5, which is essential for importing peroxisome matrix proteins. However, the post-transcriptional regulation of PEX1 is largely unknown. Here, we showed that heterogeneous nuclear ribonucleoprotein A1 (HNRNPA1) controls PEX1 expression. In addition, we found that depletion of HNRNPA1 induces autophagic degradation of peroxisome, which is blocked in ATG5-knockout cells. In addition, depletion of HNRNPA1 increased peroxisomal ROS levels. Inhibition of the generation of peroxisomal ROS by treatment with NAC significantly suppressed pexophagy in HNRNPA1-deficient cells. Taken together, our results suggest that depletion of HNRNPA1 increases peroxisomal ROS and pexophagy by downregulating PEX1 expression.

The popularity of homemade blenderized tube feeding (HBTF) continues to increase among enteral nutrition (EN) consumers and healthcare providers alike, citing improved feeding tolerance over standard commercial enteral formulas, among other health outcomes. Within the past 5-10 years, there has been a surge in the development of commercial blenderized tube feeding (CBTF) products. CBTF products promote similar benefits from whole foods like those used in HBTF while being a nutritionally-consistent, easy to use, and shelf-stable option for EN consumers. Research is improving but is still limited for HBTF and virtually nonexistent for CBTF products. This review aims to summarize current health outcomes of HBTF, compare HBTF with CBTF, evaluate CBTF products, and provide considerations for future research and practices.

The purpose of this series is to highlight a range of rare health conditions. Rare health conditions are those that affect no more and usually fewer than 1 person in every 2000 and many healthcare assistants (HCAs) and nurses will encounter some of these conditions, given the high number of these conditions. This 34th article will briefly explore four of these conditions: Zellweger syndrome, Stickler syndrome, mucormycosis and Zollinger-Ellison syndrome.

Zellweger spectrum disorder (ZSD) is a rare, debilitating genetic disorder of peroxisome biogenesis that affects multiple organ systems and presents with broad clinical heterogeneity. Although severe, intermediate, and mild forms of ZSD have been described, these designations are often arbitrary, presenting difficulty in understanding individual prognosis and treatment effectiveness. The purpose of this study is to conduct a scoping review and meta-analysis of existing literature and a medical chart review to determine if characterization of clinical findings can predict severity in ZSD. Our PubMed search for articles describing severity, clinical findings, and survival in ZSD resulted in 107 studies (representing 307 patients) that were included in the review and meta-analysis. We also collected and analyzed these same parameters from medical records of 136 ZSD individuals from our natural history study. Common clinical findings that were significantly different across severity categories included seizures, hypotonia, reduced mobility, feeding difficulties, renal cysts, adrenal insufficiency, hearing and vision loss, and a shortened lifespan. Our primary data analysis also revealed significant differences across severity categories in failure to thrive, gastroesophageal reflux, bone fractures, global developmental delay, verbal communication difficulties, and cardiac abnormalities. Univariable multinomial logistic modeling analysis of clinical findings and very long chain fatty acid (VLCFA) hexacosanoic acid (C26:0) levels showed that the number of clinical findings present among seizures, abnormal EEG, renal cysts, and cardiac abnormalities, as well as plasma C26:0 fatty acid levels could differentiate severity categories. We report the largest characterization of clinical findings in relation to overall disease severity in ZSD. This information will be useful in determining appropriate outcomes for specific subjects in clinical trials for ZSD.

Impaired peroxisome assembly caused by mutations in PEX genes results in a human congenital metabolic disease called Zellweger spectrum disorder (ZSD), which impacts the development and physiological function of multiple organs. In this study, we revealed a long-standing problem of heterogeneous peroxisome distribution among cell population, so called "peroxisomal mosaicism", which appears in patients with mild form of ZSD. We mutated PEX3 gene in HEK293 cells and obtained a mutant clone with peroxisomal mosaicism. We found that peroxisomal mosaicism can be reproducibly arise from a single cell, even if the cell has many or no peroxisomes. Using time-lapse imaging and a long-term culture experiment, we revealed that peroxisome biogenesis oscillates over a span of days; this was also confirmed in the patient's fibroblasts. During the oscillation, the metabolic activity of peroxisomes was maintained in the cells with many peroxisomes while depleted in the cells without peroxisomes. Our results indicate that ZSD patients with peroxisomal mosaicism have a cell population whose number and metabolic activities of peroxisomes can be recovered. This finding opens the way to develop novel treatment strategy for ZSD patients with peroxisomal mosaicism, who currently have very limited treatment options.

The incidence of rare diseases is approximately two cases per 10,000 people. Today, in most cases, orphan diseases are caused by genetic disorders, less often - some forms of oncological, oncohematological, infectious disorders. These conditions have a severe and chronic course, accompanied by a decrease in quality and a reduction in the life expectancy of patients. Aim - describe a clinical case of an rare disease that is referred to as Zellweger spectrum disorders. Literature review and analysis of clinical-anamnestic and laboratory-instrumental methods of research of a 6.5 years old girl. The given clinical case, namely Zellweger spectrum disorders (ZSD), is a hereditary autosomal recessive disease characterized by nonspecific clinical manifestations and phenotype, which complicates timely diagnosis and delays symptomatic, and in some cases prognostically favorable treatment. Molecular genetic research makes it possible to finally confirm this disease. Therefore, at the slightest suspicion of this pathology, it is worth investigating the level of long-chain fatty acids, plasmalogen of erythrocytes, intermediate metabolites of bile acid synthesis, or carrying out genetic sequencing. Further studies of this condition are carried out in the world in order to obtain new methods of treatment and improve the quality of life of patients. The presented clinical case of a rare disease, which belongs to ZSD, confirms the need for alertness of family doctors and pediatricians in order to timely diagnose and correct rare diseases in children.

Background: Peroxisomes are cells' organelles that responsible for the metabolism of branched-chain and very-long-chain fatty acids (VLCFA), polyamines, and amino acids. Peroxisomal biogenesis factor 6 (PEX6) is one of the factors required for the import of the proteins into peroxisomes. Mutation in any one of PEX genes will result in Zellweger syndrome (ZS), one of the peroxisome biogenesis disorder. Case Presentation: A 11-year-old girl referred was with central hypotonia and global developmental delay and feeding problems. She has an open and flat fontanel. Liver function tests and thyroid-stimulating hormone were elevated. Plasma VLCFA C26, VLCFA C24/C22, and VLCFA C26/C22 were elevated. Cerebrospinal fluid flow artifact and posterior displacement of the basilar artery findings raised the possibility of increased intracranial pressure. X-ray showed mild irregularity in the end plates of the lumbar vertebrae, bilateral coxa valga, irregularity in the articular surfaces of the ossified epiphysis of the upper and lower limbs, and generalized osteopenia. The audiological assessment profound hearing loss in both ears. Inborn error of metabolism, next-generation sequencing gene panel analysis, and whole exome sequencing showed that no pathogenic or likely pathogenic variants explaining the phenotypes. The single nucleotide polymorphisms testing showed a deletion in PEX6 gene (homozygous variant of uncertain significance). Conclusion: We report a case of ZS associated with a new PEX6 mutation that has not been previously reported in the literature.

Purpose We aimed to estimate the carrier frequency of Zellweger spectrum disorder (ZSD), a rare autosomal-recessive disease, and the associated disease incidence based on data from the Exome Aggregation Consortium (ExAC) of approximately 60,000 individuals. Methods We obtained variants from ExAC in 13 PEX genes associated with ZSD. Potentially pathogenic missense variants were identified with computational variant analysis tools according to three stringency levels. Using variants classified as potentially pathogenic, we estimated the carrier frequency and the associated incidence for the entire ExAC population and its sub-populations. We also evaluated variants based on pathogenicity criteria for sequence variant interpretation outlined by the American College of Medical Genetics and Genomics (ACMG) and calculated the carrier frequency and incidence based on those variants. Results The bioinformatically estimated incidence rate of ZSD in the ExAC population is 1 in 83,841 using our least stringent pathogenicity cutoff. Under clinical guidelines outlined by ACMG, the estimated incidence is 1 in 3,275,751 births. Conclusion We outlined a process for estimating the ZSD disease carrier frequency and incidence in a large consortium using bioinformatics tools. Our results are close to current newborn screening estimates in New York of 1 in 90,000 births, estimated from 1.08 million screenings.

Zellweger spectrum disorder (ZSD) is the most severe peroxisomal biogenesis disorder (PBD). Why ZSD patients not only loose functional peroxisomes but also present with severe mitochondrial dysfunction was a long‐standing mystery. In this issue, Nuebel et al (2021) identified that loss of peroxisomes leads to re‐routing of peroxisomal proteins to mitochondria, thereby impairing mitochondrial structure and function. The findings provide the first molecular understanding of the mitochondrial‐peroxisomal link in ZSD., A study in this issue provides the first molecular understanding of the mitochondrial‐peroxisomal link in peroxisomal disorders.

Peroxisome biogenesis disorders-Zellweger spectrum disorders (PBD-ZSD)-are primarily autosomal recessive disorders caused by mutations in any of 13 PEX genes involved in peroxisome assembly. Compared to other PEX-related disorders, some PEX16 defects are associated with an atypical phenotype consisting of spasticity, cerebellar dysfunction, preserved cognition, and prolonged survival. In this case series, medical records and brain MRIs from 7 patients with this PEX16 presentation were reviewed to further characterize this phenotype. Classic PBD features such as sensory deficits and amelogenesis imperfecta were absent in all 7 patients, while all patients had hypertonia. Five patients were noted to have dystonia and received a treatment trial of levodopa/carbidopa. Four treated patients had partial but significant improvements in their dystonia and tremors, and 1 patient had only minimal response. Brain MRI studies commonly showed T2/FLAIR hyperintensities in the brainstem, superior and middle cerebellar peduncles, corticospinal tracts, and splenium of the corpus callosum. Genetic analysis revealed novel biallelic variants in 3 probands (c.683C T/372delG; c.692A G homozygous; c.865C G/451C T) and 1 novel variant (c.956_958delCGC) in another proband. We demonstrated residual PEX16 protein amounts by immunoblotting in fibroblasts available from 5 patients with this atypical PEX16 disease (3 from this series, 2 previously reported), in contrast to the absence of PEX16 protein in fibroblasts from a patient with the severe ZSD presentation. This study further characterizes the phenotype of PEX16 defects by highlighting novel and distinctive clinical, neuroradiological, and molecular features of the disease and proposes a potential treatment for the dystonia. ClinicalTrials.gov Identifier: NCT01668186. Date of registration: January 2012.

Background Zellweger spectrum disorders (ZSDs) are a rare, heterogenous group of autosomal recessively inherited disorders characterized by reduced peroxisomes numbers, impaired peroxisomal formation, and/or defective peroxisomal functioning. In the absence of functional peroxisomes, bile acid synthesis is disrupted, and multisystem disease ensues with abnormalities in the brain, liver, kidneys, muscle, eyes, ears, and nervous system. Main body Liver disease may play an important role in morbidity and mortality, with hepatic fibrosis that can develop as early as the postnatal period and often progressing to cirrhosis within the first year of life. Because hepatic dysfunction can have numerous secondary effects on other organ systems, thereby impacting the overall disease severity, the treatment of liver disease in patients with ZSD is an important focus of disease management. Cholbam® (cholic acid), approved by the U.S. Food and Drug Administration in March 2015, is currently the only therapy approved as adjunctive treatment for patients with ZSDs and single enzyme bile acid synthesis disorders. This review will focus on the use of CA therapy in the treatment of liver disease associated with ZSDs, including recommendations for initiating and maintaining CA therapy and the limitations of available clinical data supporting its use in this patient population. Conclusions Cholbam is a safe and well-tolerated treatment for patients with ZSDs that has been shown to improve liver chemistries and reduce toxic bile acid intermediates in the majority of patients with ZSD. Due to the systemic impacts of hepatic damage, Cholbam should be initiated in patients without signs of advanced liver disease.

Peroxisomes are multifunctional organelles best known for their role in cellular lipid and hydrogen peroxide metabolism. In this chapter, we review and discuss the diverse functions of this organelle in brain physiology and neurodegeneration, with a particular focus on oxidative stress. We first briefly summarize what is known about the various nexuses among peroxisomes, the central nervous system, oxidative stress, and neurodegenerative disease. Next, we provide a comprehensive overview of the complex interplay among peroxisomes, oxidative stress, and neurodegeneration in patients suffering from primary peroxisomal disorders. Particular examples that are discussed include the prototypic Zellweger spectrum disorders and X-linked adrenoleukodystrophy, the most prevalent peroxisomal disorder. Thereafter, we elaborate on secondary peroxisome dysfunction in more common neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Finally, we highlight some issues and challenges that need to be addressed to progress towards therapies and prevention strategies preserving, normalizing, or improving peroxisome activity in patients suffering from neurodegenerative conditions.

Zellweger syndrome disorders (ZSD) is the principal group of peroxisomal disorders characterized by a defect of peroxisome biogenesis due to mutations in one of the 13 PEX genes. The clinical spectrum is very large with a continuum from antenatal forms to adult presentation. Whereas biochemical profile in body fluids is classically used for their diagnosis, the revolution of high-throughput sequencing has extended the knowledge about these disorders. The aim of this review is to offer a large panorama on molecular basis, clinical presentation and treatment of ZSD, and to update the diagnosis strategy of these disorders in the era of next-generation sequencing (NGS).

In Zellweger syndrome (ZS), lack of peroxisome function causes physiological and developmental abnormalities in many organs such as the brain, liver, muscles, and kidneys, but little is known about the exact pathogenic mechanism. By disrupting the zebrafish pex2 gene, we established a disease model for ZS and found that it exhibits a pathological condition and metabolic failures similar to that of human patients. By comprehensive analysis of fatty acid profile, we found organ specific accumulation and reduction of distinct fatty acid species such as an accumulation of ultra-very-long-chain polyunsturated fatty acids (ultra-VLCPUFAs) in the brain of pex2 mutant fish. Transcriptome analysis using microarray also revealed mutant-specific gene expression changes that might lead to the symptom, which include reduction of crystallin, troponin, parvalbumin, and fatty acid metabolic genes. Our data indicated that the loss of peroxisome results in widespread metabolic and gene expression changes beyond the causative peroxisomal function. These results suggest the genetic and metabolic basis of the pathology of this devastating human disease.

Advances in genetic technology have allowed for the development of multiplex panels that can test for hundreds of genetic disorders at the same time; these large panels are referred to as expanded carrier screening. This process can screen couples for far more conditions than the gene-by-gene approach used with traditional carrier screening; however, although expanded carrier screening has been promoted as an efficient means of detecting many more disorders, the complexities of genetic sequencing raise substantial challenges and concerns. In our practice, we have seen a number of complex cases in which only attention to detail on the part of thorough genetic counselors allowed identification of misclassified variants that could have resulted in significant patient harm. We raise issues that require urgent attention by professional societies, including: whether to endorse testing that uses sequencing compared with genotyping; required components of pretest and posttest counseling; reclassification of variants; whether obstetric health care professionals have a responsibility to assure that patients understand the iterative process of variant interpretation and how it relates to carrier screening results; and the question of rescreening in subsequent pregnancies. Implementation of expanded carrier screening needs to be considered thoughtfully in light of the complexity of genetic sequencing and limited knowledge of genetics of most front-line obstetric health care professionals.

At least 14 distinctive PEX genes function in the biogenesis of peroxisomes. Biallelic alterations in the peroxisomal biogenesis factor 12 (PEX12) gene lead to Zellweger syndrome spectrum (ZSS) with variable clinical expressivity ranging from early lethality to mildly affected with long-term survival. Herein, we define 20 patients derived from 14 unrelated Egyptian families, 19 of which show a homozygous PEX12 in-frame (c.1047_1049del p.(Gln349del)) deletion. This founder mutation, reported rarely outside of Egypt, was associated with a uniformly severe phenotype. Patients showed developmental delay in early life followed by motor and mental regression, progressive hypotonia, unsteadiness, and lack of speech. Seventeen patients had sparse hair or partial alopecia, a striking feature that was not noted previously in PEX12. Neonatal cholestasis was manifested in 2 siblings. Neurodiagnostics showed consistent cerebellar atrophy and variable white matter demyelination, axonal neuropathy in about half, and cardiomyopathy in 10% of patients. A single patient with a compound heterozygous PEX12 mutation exhibited milder features with late childhood onset with gait disturbance and learning disability. Thus, the PEX12 relatively common founder mutation accounts for the majority of PEX12-related disease in Egypt and delineates a uniform clinical and radiographic phenotype.

The peroxisomal diseases are genetically determined disorders caused either by the failure to form or maintain the peroxisome or by a defect in the function of a single protein that is normally located in this organelle. It is a heterogeneous group of autosomal recessive disorders characterized by a defect in peroxisome formation and are caused by mutations in one of 13 PEX genes. The defect in peroxisome formation or impaired metabolic pathways result in metabolic abnormalities. Typically in Zellweger spectrum disorders (ZSD) patients accumulate very long chain fatty acids (VLCFAs), phytanic and pristanic acid, C27-bile acid intermediates and pipecolic acid in plasma and have a deficiency of plasmalogens in erythrocytes.These disorders present with a wider range of phenotype than has been recognized in the past and few of them may phenotypically resemble Downs Syndrome.

Peroxisomes are single-membrane organelles present in eukaryotes. The functional importance of peroxisomes in humans is represented by peroxisome-deficient peroxisome biogenesis disorders (PBDs), including Zellweger syndrome. Defects in the genes that encode the 14 peroxins that are required for peroxisomal membrane assembly, matrix protein import and division have been identified in PBDs. A number of recent findings have advanced our understanding of the biology, physiology and consequences of functional defects in peroxisomes. In this Review, we discuss a cooperative cell defense mechanisms against oxidative stress that involves the localization of BAK (also known as BAK1) to peroxisomes, which alters peroxisomal membrane permeability, resulting in the export of catalase, a peroxisomal enzyme. Another important recent finding is the discovery of a nucleoside diphosphate kinase-like protein that has been shown to be essential for how the energy GTP is generated and provided for the fission of peroxisomes. With regard to PBDs, we newly identified a mild mutation, Pex26-F51L that causes only hearing loss. We will also discuss findings from a new PBD model mouse defective in Pex14, which manifested dysregulation of the BDNF–TrkB pathway, an essential signaling pathway in cerebellar morphogenesis. Here, we thus aim to provide a current view of peroxisome biogenesis and the molecular pathogenesis of PBDs.

Background Mutations in PEX16 cause peroxisome biogenesis disorder (PBD). Zellweger syndrome characterized by neurological dysfunction, dysmorphic features, liver disease and early death represents the severe end of this clinical spectrum. Here we discuss the diagnostic challenge of atypical PEX16 related PBD in 3 patients from highly inbred kindred and describe the role of specific metabolites analyses, fibroblasts studies, whole-exome sequencing (WES) and metabolomics profiling to establish the diagnosis. Methods and patients The proband is a 12-year-old male born to consanguineous parents. Despite normal development in the first year, regression and progressive spastic diplegia, poor coordination and dysarthria occurred thereafter. Patient 2 (3-year old female) and Patient 3 (19-month old female) shared similar clinical course with the proband. Biochemical studies on plasma and fibroblasts, WES and global metabolomics analyses were performed. Results Very-long-chain fatty acids analysis showed subtle elevations in C26 and C26/C22. Global Metabolomics-Assisted Pathway profiling was not remarkable. Immunocytochemical investigations on fibroblasts revealed fewer catalase and PMP70-containing particles indicating aberrant peroxisomal assembly. Complementation studies were inconclusive. WES revealed a novel homozygous variant in PEX16 (c.859C>T). The biochemical profiles of Patient 2 and Patient 3 were similar to the proband and the same genotype was confirmed. Conclusion This paper highlights the diagnostic challenge of PEX16 patients due to the widely variable clinical and biochemical phenotypes. It also emphasizes the important roles of combined biochemical assays with next generation sequencing techniques in reaching diagnosis in the context of atypical clinical presentations, subtle biomarker abnormalities and consanguinity.

Zellweger spectrum disorder (ZSD) results from biallelic mutations in PEX genes required for peroxisome biogenesis. PEX1-G843D is a common hypomorphic allele in the patient population that is associated with milder disease. In prior work using a PEX1-G843D/null patient fibroblast line expressing a green fluorescent protein (GFP) reporter with a peroxisome-targeting signal (GFP-PTS1), we demonstrated that treatments with the chemical chaperone betaine and flavonoid acacetin diacetate recovered peroxisome functions. To identify more effective compounds for preclinical investigation, we evaluated 54 flavonoids using this cell-based phenotype assay. Diosmetin showed the most promising combination of potency and efficacy (EC50 2.5 µM). All active 5',7'-dihydroxyflavones showed greater average efficacy than their corresponding flavonols, whereas the corresponding flavanones, isoflavones, and chalcones tested were inactive. Additional treatment with the proteostasis regulator bortezomib increased the percentage of import-rescued cells over treatment with flavonoids alone. Cotreatments of diosmetin and betaine showed the most robust additive effects, as confirmed by three independent functional assays in primary PEX1-G843D patient cells, but neither agent was active alone or in combination in patient cells homozygous for the PEX1 c.2097_2098insT null allele. Moreover, diosmetin treatment increased PEX1, PEX6, and PEX5 protein levels in PEX1-G843D patient cells, but none of these proteins increased in PEX1 null cells. We propose that diosmetin acts as a pharmacological chaperone that improves the stability, conformation, and functions of PEX1/PEX6 exportomer complexes required for peroxisome assembly. We suggest that diosmetin, in clinical use for chronic venous disease, and related flavonoids warrant further preclinical investigation for the treatment of PEX1-G843D-associated ZSD.

PURPOSE: Peroxisome biogenesis disorders–Zellweger spectrum disorders (PBD-ZSD) are metabolic diseases with multisystem manifestations. Individuals with PBD-ZSD exhibit impaired peroxisomal biochemical functions and have abnormal levels of peroxisomal metabolites, but the broader metabolic impact of peroxisomal dysfunction and the utility of metabolomic methods is unknown. METHODS: We studied 19 individuals with clinically and molecularly characterized PBD-ZSD. We performed both quantitative peroxisomal biochemical diagnostic studies in parallel with untargeted small molecule metabolomic profiling in plasma samples with detection of > 650 named compounds. RESULTS: The cohort represented intermediate to mild PBD-ZSD subjects with peroxisomal biochemical alterations on targeted analysis. Untargeted metabolomic profiling of these samples revealed elevations in pipecolic acid and long-chain lysophosphatidylcholines, as well as an unanticipated reduction in multiple sphingomyelin species. These sphingomyelin reductions observed were consistent across the PBD-ZSD samples and were rare in a population of > 1,000 clinical samples. Interestingly, the pattern or “PBD-ZSD metabolome” was more pronounced in younger subjects suggesting studies earlier in life reveal larger biochemical changes. CONCLUSION: Untargeted metabolomics is effective in detecting mild to intermediate cases of PBD-ZSD. Surprisingly, dramatic reductions in plasma sphingomyelin are a consistent feature of the PBD-ZSD metabolome. The use of metabolomics in PBD-ZSD can provide insight into novel biomarkers of disease.

The purpose of this series is to briefly highlight a range of rare health conditions. Rare health conditions are those that affect no more and usually fewer than 1 person in every 2000 and many HCAs and nurses will encounter some of these conditions, given the high number of these conditions. This fifteenth article will briefly explore four of these conditions.

Mitochondria are constantly communicating with the rest of the cell. Defects in mitochondria underlie severe pathologies, whose mechanisms remain poorly understood. It is becoming increasingly evident that mitochondrial malfunction resonates in other organelles, perturbing their function and their biogenesis. In this manuscript, we review the current knowledge on the cross-talk between mitochondria and other organelles, particularly lysosomes, peroxisomes and the endoplasmic reticulum. Several organelle interactions are mediated by transcriptional programs, and other signaling mechanisms are likely mediating organelle dysfunction downstream of mitochondrial impairments. Many of these organelle crosstalk pathways are likely to have a role in pathological processes., Highlights • Mitochondrial malfunction affects lysosomal biogenesis via AMPK signaling. • Lysosomal malfunction represses mitochondrial function. • ER stress promotes degradation of damaged mitochondria. • Organelle crosstalk is a key component of mitochondrial signaling in physiology and pathology.

Zellweger spectrum disorders (ZSD) are rare autosomal recessive inherited metabolic disorders and include severe (Zellweger syndrome) and milder phenotypes [neonatal adrenoleukodystrophy and infantile Refsum disease (IRD)]. ZSD are characterized by impaired peroxisomal functions and lack of peroxisomes detected by electron microscopy (EM). ZSD are caused by mutations in any of the 14 PEX genes. Patients with ZSD commonly demonstrate nonspecific hepatic symptoms within the first year, often without clinical suspicion of ZSD. Thus, recognition of pathologic findings in the liver is critical for the early diagnosis. We herein demonstrate the histologic and ultrastructural features in liver biopsies in the early and advanced phases from a 16-year-old male with IRD. The initial biopsy at 5 months of age showed a lack of peroxisomes by EM, and this finding played a critical role in the early diagnosis. In contrast, the second biopsy at 14 years of age, after long-term diet therapy, demonstrated significant disease progression with near-cirrhotic liver. In addition to lack of peroxisomes, EM revealed abundant trilamellar inclusions within large angulated lysosomes in many of the hepatocytes and Kupffer cells. Mitochondrial abnormalities were identified only in the second biopsy and were mainly identified in damaged cells; thus they were likely nonspecific secondary changes. This is the first report demonstrating histological and ultrastructural features of liver biopsies in the early and advanced phases from a child with ZSD. Trilamellar inclusions are considered to be an ultrastructural hallmark of ZSD, but they may not be apparent in the early phases.

Lipids are among the most important organic compounds found in all living cells, from primitive archaebacteria to flowering plants or mammalian cells. They form part of cell walls and constitute cell storage material. Their biosynthesis and metabolism play key roles in faraway topics such as biofuel production (third-generation biofuels produced by microorganisms, e.g. algae) and human diseases such as adrenoleukodystrophy, Zellweger syndrome, or Refsum disease. Current lipidomic analysis requires fast and accurate processing of samples and especially their characterization. Because the number of possible lipids and, more specifically, molecular species of lipids is of the order of hundreds to thousands, it is necessary to process huge amounts of data in a short time. There are two basic approaches to lipidomic analysis: shotgun and liquid chromatography-mass spectometry. Both methods have their pros and cons. This review deals with lipidomics not according to the type of ionization or the lipid classes analyzed but according to the types of samples (organisms) under study. Thus, it is divided into lipidomic analysis of archaebacteria, bacteria, yeast, fungi, algae, plants, and animals.

Background: Zellweger syndrome (ZS) is a peroxisome biogenesis disorder attributed to a mutation of the PEX genes family. The incidence of this disease in Africa and the Arab world remains unknown. This contribution is aimed at describing the clinical phenotype and biochemical features in Tunisian patients with ZS in order to improve the detection and management of this severe disorder. Methods: A total of 52 patients diagnosed with ZS and 60 age- and sex-matched healthy controls were included in this study. Patients were recruited during the past 21 years, and the diagnosis of ZS was based on clinical and biochemical characteristics. Plasma very long chain fatty acids (VLCFA) were analyzed using capillary gas chromatography. The estimated incidence of ZS was calculated using the HardyâWeinberg formula. Results: The estimated incidence of ZS is 1/15,898 in Tunisia. Age at diagnosis varied between 3 days and 18 months. Severe neurological syndrome, polymalformative features, and hepatodigestive signs were observed in 100%, 67.9%, and 32% of patients, respectively. Values for plasma C26:0 and C26:0/C22:0 and C24:0/C22:0 ratios were noticeably higher in ZS patients than in controls. Distributions of values were completely different for C26:0 (0.10â0.37 vs. 0.001â0.009), C26:0/C22:0 ratio (0.11â1.29 vs. 0.003â0.090), and C24:0/C22:0 ratio (1.03â3.18 vs. 0.4â0.90) in ZS patients versus controls, respectively. Conclusions: This study highlights the high incidence of ZS in Tunisia and the possibility of simple and reliable biochemical diagnosis, thus permitting early genetic counseling for families at risk. Key Words: gas chromatography, hypotonia, peroxisomal disorder, very long chain fatty acids, Zellweger syndrome

Introduction: Zellweger spectrum disorders (ZSDs) are caused by an impairment of peroxisome biogenesis, resulting in multiple metabolic abnormalities. This leads to a range of symptoms, including hepatic dysfunction and coagulopathy. This study evaluated the incidence and severity of coagulopathy and the effect of vitamin K supplementation orally and IV in ZSD. Methods: Data were retrospectively retrieved from the medical records of 30 ZSD patients to study coagulopathy and the effect of vitamin K orally on proteins induced by vitamin K absence (PIVKA-II) levels. Five patients from the cohort with a prolonged prothrombin time, low factor VII, and elevated PIVKA-II levels received 10 mg of vitamin K IV. Laboratory results, including thrombin generation, at baseline and 72 h after vitamin K administration were examined. Results: In the retrospective cohort, four patients (13.3%) experienced intracranial bleedings and 14 (46.7%) reported minor bleeding. No thrombotic events occurred. PIVKA-II levels decreased 38% after start of vitamin K therapy orally. In the five patients with a coagulopathy, despite treatment with oral administration of vitamin K, vitamin K IV caused an additional decrease (23%) of PIVKA-II levels and increased thrombin generation. Conclusion: Bleeding complications frequently occur in ZSD patients due to liver disease and vitamin K deficiency. Vitamin K deficiency is partly corrected by vitamin K supplementation orally, and vitamin K administered IV additionally improves vitamin K status, as shown by further decrease of PIVKA-II and improved thrombin generation.

Zellweger syndrome (ZS) is a consequence of a peroxisome biogenesis disorder (PBD) caused by the presence of a pathogenic mutation in one of the 13 genes from the PEX family. ZS is a severe multisystem condition characterized by neonatal appearance of symptoms and a shorter life. Here, we report a case of ZS with a mild phenotype, due to a novel PEX6 gene mutation. The patient presented subtle craniofacial dysmorphic features and slightly slower psychomotor development. At the age of 2 years, he was diagnosed with adrenal insufficiency, hypoacusis, and general deterioration. Magnetic resonance imaging showed a symmetrical hyperintense signal in the frontal and parietal white matter. Biochemical tests showed elevated liver transaminases, elevated serum very long chain fatty acids, and phytanic acid. After the death of the child at the age of 6 years, molecular diagnostics were continued in order to provide genetic counseling for his parents. Next generation sequencing (NGS) analysis with the TruSight One™ Sequencing Panel revealed a novel homozygous PEX6 p.Ala94Pro mutation. In silico prediction of variant severity suggested its possible benign effect. To conclude, in the milder phenotypes, adrenal insufficiency, hypoacusis, and leukodystrophy together seem to be pathognomonic for ZS.

Objectives: Patients with bile acid synthesis disorders (BASDs) due to single enzyme defects (SEDs) or Zellweger spectrum disorders (ZSDs) accumulate hepatotoxic atypical bile acids resulting in potentially fatal progressive liver disease. We evaluated the efficacy and safety of oral cholic acid in patients with BASD. Methods: In this phase 3, open-label, single-arm, nonrandomized, noncomparative study conducted over 18 years, patients were administered cholic acid orally 10 to 15 mg · kg−1 · day−1. The primary efficacy variables were changes from pre- to post-treatment in atypical urinary bile acids, liver chemistries (serum aspartate aminotransferase, alanine aminotransferase), and height and weight. Additional efficacy variables included changes in serum bilirubin and liver histology. Results: Of the 85 enrolled patients (63 with SED and 22 with ZSD), 79 received at least 1 dose of study medication; 70 patients (50 with SED and 20 with ZSD) were included in the modified intent-to-treat dataset. Cholic acid significantly improved urine bile acid metabolite scores (P

Bile acids facilitate the absorption of lipids in the gut, but are also needed to maintain cholesterol homeostasis, induce bile flow, excrete toxic substances and regulate energy metabolism by acting as signaling molecules. Bile acid biosynthesis is a complex process distributed across many cellular organelles and requires at least 17 enzymes in addition to different metabolite transport proteins to synthesize the two primary bile acids, cholic acid and chenodeoxycholic acid. Disorders of bile acid synthesis can present from the neonatal period to adulthood and have very diverse clinical symptoms ranging from cholestatic liver disease to neuropsychiatric symptoms and spastic paraplegias. This review describes the different bile acid synthesis pathways followed by a summary of the current knowledge on hereditary disorders of human bile acid biosynthesis with a special focus on diagnostic bile acid profiling using mass spectrometry. (C) 2017 Elsevier Ltd. All rights reserved

Introduction Zellweger spectrum disorders (ZSD) are a group of genetic metabolic disorders caused by a defect in peroxisome biogenesis. This results in multiple metabolic abnormalities, including elevated very long-chain fatty acid (VLCFA) levels. Elevated levels of C26:0-lysophosphatidylcholine (C26:0-lysoPC) have been shown in dried blood spots (DBS) from ZSD patients. However, little is known about the sensitivity and specificity of this marker and C26:0-carnitine, another VLCFA-marker, in ZSD. We investigated C26:0-lysoPC and C26:0-carnitine as diagnostic markers for ZSD in DBS and fibroblasts. Methods C26:0-lysoPC levels in 91 DBS from 37 different ZSD patients were determined and compared to the levels in 209 control DBS. C26:0-carnitine levels were measured in 41 DBS from 29 ZSD patients and 97 control DBS. We measured C26:0-lysoPC levels in fibroblasts from 24 ZSD patients and 61 control individuals. Results Elevated C26:0-lysoPC levels (> 72 nmol/L) were found in 86/91 ZSD DBS (n=33/37 patients) corresponding to a sensitivity of 89.2%. Median level was 567 nmol/l (range 28-3133 nmol/l). Consistently elevated C26:0-carnitine levels (> 0.077 mu mol/L) in DBS were found in 16 out of 29 ZSD patients corresponding to a sensitivity of 55.2%. C26:0-lysoPC levels were elevated in 21/24 ZSD fibroblast lines. Discussion C26:0-lysoPC in DBS is a sensitive and useful marker for VLCFA accumulation in patients with a ZSD. C26:0-carnitine in DBS is elevated in some ZSD patients, but is less useful as a diagnostic marker. Implementation of C26:0-lysoPC measurement in the diagnostic work-up when suspecting a ZSD is advised. This marker has the potential to be used for newborn screening for ZSD

Peroxisome biogenesis disorders (PBDs) represent a spectrum of human genetic disorders that are characterized by damaged peroxisome assembly. In the newborn period, the characteristics of affected patients include dysmorphic facial features, neonatal hypotonia, seizures, ocular abnormalities, poor feeding, liver cysts with hepatic dysfunction and skeletal defects. These can be caused by a defect in at least 14 different PEX genes. In this study, whole-exome sequencing (WES) was performed on samples from two Chinese newborns with clinical features of Zellweger syndrome. WES identified two novel mutations (c.2416+1G>T and c.2489delT) in patient 1 and another two novel mutations (c.1483+1G>A and c.1727dupG) in patient 2 in the PEX1 gene. All four mutations have a serious influence on the protein function, which also highlights the power of WES, particularly in clinically challenging cases.

Ketohexokinase (KHK) is the first and rate-limiting enzyme of fructose metabolism. Expression of the two alternatively spliced KHK isoforms, KHK-A and KHK-C, is tissue-specific and KHK-C is predominantly expressed in liver, kidney and intestine and responsible for the fructose-catabolizing function. While KHK isoform choice has been linked to the development of disorders such as obesity, diabetes, cardiovascular disease and cancer, little is known about the regulation of total KHK expression. In the present study, we investigated how hypoxic signaling influences fructose metabolism in the liver. Hypoxia or von Hippel-Lindau (VHL) tumor suppressor loss leads to the stabilization of hypoxia-inducible factors alpha (HIF-1α and HIF-2α) and the activation of their signaling to mediate adaptive responses. By studying liver-specific Vhl, Vhl/Hif1a, and Vhl/Epas1 knockout mice, we found that KHK expression is suppressed by HIF-2α (encoded by Epas1) but not by HIF-1α signaling on mRNA and protein levels. Reduced KHK levels were accompanied by downregulation of aldolase B (ALDOB) in the livers of Vhl and Vhl/Hif1a knockout mice, further indicating inhibited fructose metabolism. HIF-1α and HIF-2α have both overlapping and distinct target genes but are differentially regulated depending on the cell type and physiologic or pathologic conditions. HIF-2α activation augments peroxisome degradation in mammalian cells by pexophagy and thereby changes lipid composition reminiscent of peroxisomal disorders. We further demonstrated that fructose metabolism is negatively regulated by peroxisome-deficiency in a Pex2 knockout Zellweger mouse model, which lacks functional peroxisomes and is characterized by widespread metabolic dysfunction. Repression of fructolytic genes in Pex2 knockout mice appeared to be independent of PPARα signaling and nutritional status. Interestingly, our results demonstrate that both HIF-2α and peroxisome-deficiency result in downregulation of Khk independent of splicing as both isoforms, Khka as well as Khkc, are significantly downregulated. Hence, our study offers new and unexpected insights into the general regulation of KHK, and therefore fructolysis. We revealed a novel regulatory function of HIF-2α, suggesting that HIF-1α and HIF-2α have tissue-specific opposing roles in the regulation of Khk expression, isoform choice and fructolysis. In addition, we discovered a previously unknown function of peroxisomes in the regulation of fructose metabolism.

Pipecolic acid (Pip), a non-proteinacious product of lysine catabolism, is an important regulator of immunity in plants and humans alike. For instance, Pip accumulation is associated with the genetic disorder Zellweger syndrome, chronic liver diseases, and pyridoxine-dependent epilepsy in humans. In plants, Pip accumulates upon pathogen infection and is required for plant defense. The aminotransferase ALD1 catalyzes biosynthesis of Pip precursor piperideine-2-carboxylic acid, which is converted to Pip via ornithine cyclodeaminase. A variety of methods are used to quantify Pip, and some of these involve use of expensive amino acid analysis kits. Here, we describe a simplified procedure for quantitative analysis of Pip from plant tissues. Pipecolic acid was extracted from leaf tissues along with an internal standard norvaline, derivatized with propyl chloroformate and analyzed by gas chromatography-coupled mass spectrometry using selective ion mode. This procedure is simple, economical, and efficient and does not involve isotopic internal standards or multiple-step derivatizations.

Peroxisomes are presented in all eukaryotic cells and play essential roles in many of lipid metabolic pathways, including β-oxidation of fatty acids and synthesis of ether-linked glycerophospholipids, such as plasmalogens. Impaired peroxisome biogenesis, including defects of membrane assembly, import of peroxisomal matrix proteins, and division of peroxisome, causes peroxisome biogenesis disorders (PBDs). Fourteen complementation groups of PBDs are found, and their complementing genes termed PEXs are isolated. Several new mutations in peroxins from patients with mild PBD phenotype or patients with phenotypes unrelated to the commonly observed impairments of PBD patients are found by next-generation sequencing. Exploring a dysfunctional step(s) caused by the mutation is important for unveiling the pathogenesis of novel mutation by means of cellular and biochemical analyses.

Peroxisomes are ubiquitous subcellular organelles. Peroxisomal disorders may be divided into disorders of peroxisome biogenesis and single-enzyme disorders. Nearly all of these disorders are expressed in the nervous system. The most common disorder of the group is X-linked adrenoleukodystrophy, which may develop in either childhood or adulthood with various neurologic manifestations. In contrast are the severe biogenesis disorders that are multisystem and may affect neuronal migration with resultant developmental abnormalities, seizures, and progressive demyelination. The diagnosis of these disorders results on the understanding of the biochemical abnormalities and they may reliably diagnosed by biochemical measures or DNA analysis.

Zellweger syndrome disorders (ZSD) is the principal group of peroxisomal disorders characterized by a defect of peroxisome biogenesis due to mutations in one of the 13 PEX genes. The clinical spectrum is very large with a continuum from antenatal forms to adult presentation. Whereas biochemical profile in body fluids is classically used for their diagnosis, the revolution of high-throughput sequencing has extended the knowledge about these disorders. The aim of this review is to offer a large panorama on molecular basis, clinical presentation and treatment of ZSD, and to update the diagnosis strategy of these disorders in the era of next-generation sequencing (NGS).