Unraveling the Hallervorden-Spatz syndrome: pantothenate kinase-associated neurodegeneration is the name

Endoplasmic Reticulum Membrane Contact Sites, Lipid Transport, and Neurodegeneration

The Endoplasmic Reticulum (ER) is an endomembrane system that plays a multiplicity of roles in cell physiology and populates even the most distal cell compartments, including dendritic tips and axon terminals of neurons. Some of its functions are achieved by a cross talk with other intracellular membranous organelles and with the plasma membrane at membrane contacts sites (MCSs). As the ER synthesizes most membrane lipids, lipid exchanges mediated by lipid transfer proteins at MCSs are a particularly important aspect of this cross talk, which synergizes with the cross talk mediated by vesicular transport. Several mutations of genes that encode proteins localized at ER MCSs result in familial neurodegenerative diseases, emphasizing the importance of the normal lipid traffic within cells for a healthy brain. Here, we provide an overview of such diseases, with a specific focus on proteins that directly or indirectly impact lipid transport.

Bi-Allelic Mutations in Zebrafish pank2 Gene Lead to Testicular Atrophy and Perturbed Behavior without Signs of Neurodegeneration

Coenzyme A (CoA) is an essential cofactor in all living organisms, being involved in a large number of chemical reactions. Sequence variations in pantothenate kinase 2 (PANK2), the first enzyme of CoA biosynthesis, are found in patients affected by Pantothenate Kinase Associated Neurodegeneration (PKAN), one of the most common forms of neurodegeneration, with brain iron accumulation. Knowledge about the biochemical and molecular features of this disorder has increased a lot in recent years. Nonetheless, the main culprit of the pathology is not well defined, and no treatment option is available yet. In order to contribute to the understanding of this disease and facilitate the search for therapies, we explored the potential of the zebrafish animal model and generated lines carrying biallelic mutations in the pank2 gene. The phenotypic characterization of pank2-mutant embryos revealed anomalies in the development of venous vascular structures and germ cells. Adult fish showed testicular atrophy and altered behavioral response in an anxiety test but no evident signs of neurodegeneration. The study suggests that selected cell and tissue types show a higher vulnerability to pank2 deficiency in zebrafish. Deciphering the biological basis of this phenomenon could provide relevant clues for better understanding and treating PKAN.

A partnership between the lipid scramblase XK and the lipid transfer protein VPS13A at the plasma membrane

Chorea-acanthocytosis (ChAc) and McLeod syndrome are diseases with shared clinical manifestations caused by mutations in VPS13A and XK, respectively. Key features of these conditions are the degeneration of caudate neurons and the presence of abnormally shaped erythrocytes. XK belongs to a family of plasma membrane (PM) lipid scramblases whose action results in exposure of PtdSer at the cell surface. VPS13A is an endoplasmic reticulum (ER)-anchored lipid transfer protein with a putative role in the transport of lipids at contacts of the ER with other membranes. Recently VPS13A and XK were reported to interact by still unknown mechanisms. So far, however, there is no evidence for a colocalization of the two proteins at contacts of the ER with the PM, where XK resides, as VPS13A was shown to be localized at contacts between the ER and either mitochondria or lipid droplets. Here we show that VPS13A can also localize at ER-PM contacts via the binding of its PH domain to a cytosolic loop of XK, that such interaction is regulated by an intramolecular interaction within XK, and that both VPS13A and XK are highly expressed in the caudate neurons. Binding of the PH domain of VPS13A to XK is competitive with its binding to intracellular membranes that mediate other tethering functions of VPS13A. Our findings support a model according to which VPS13A-dependent lipid transfer between the ER and the PM is coupled to lipid scrambling within the PM. They raise the possibility that defective cell surface exposure of PtdSer may be responsible for neurodegeneration.

Insights into VPS13 properties and function reveal a new mechanism of eukaryotic lipid transport

The occurrence of protein mediated lipid transfer between intracellular membranes has been known since the late 1960's. Since these early discoveries, numerous proteins responsible for such transport, which often act at membrane contact sites, have been identified. Typically, they comprise a lipid harboring module thought to shuttle back and forth between the two adjacent bilayers. Recently, however, studies of the chorein domain protein family, which includes VPS13 and ATG2, has led to the identification of a novel mechanism of lipid transport between organelles in eukaryotic cells mediated by a rod-like protein bridge with a hydrophobic groove through which lipids can slide. This mechanism is ideally suited for bulk transport of bilayer lipids to promote membrane growth. Here we describe how studies of VPS13 led to the discovery of this new mechanism, summarize properties and known roles of VPS13 proteins, and discuss how their dysfunction may lead to disease.

Coenzyme a Biochemistry: From Neurodevelopment to Neurodegeneration

Coenzyme A (CoA) is an essential cofactor in all living organisms. It is involved in a large number of biochemical processes functioning either as an activator of molecules with carbonyl groups or as a carrier of acyl moieties. Together with its thioester derivatives, it plays a central role in cell metabolism, post-translational modification, and gene expression. Furthermore, recent studies revealed a role for CoA in the redox regulation by the S-thiolation of cysteine residues in cellular proteins. The intracellular concentration and distribution in different cellular compartments of CoA and its derivatives are controlled by several extracellular stimuli such as nutrients, hormones, metabolites, and cellular stresses. Perturbations of the biosynthesis and homeostasis of CoA and/or acyl-CoA are connected with several pathological conditions, including cancer, myopathies, and cardiomyopathies. In the most recent years, defects in genes involved in CoA production and distribution have been found in patients affected by rare forms of neurodegenerative and neurodevelopmental disorders. In this review, we will summarize the most relevant aspects of CoA cellular metabolism, their role in the pathogenesis of selected neurodevelopmental and neurodegenerative disorders, and recent advancements in the search for therapeutic approaches for such diseases.

[Update on the etiology and pathogenesis of muscle dystonia]

Muscle dystonia is one of the most common extrapyramidal diseases and is the third most common after essential tremor and Parkinson's disease. The introduction of diagnostic methods expanded the understanding of the genetic basis of muscle dystonia and neurophysiological mechanisms of dystonic phenomena. However, the questions of the etiology and pathogenesis of dystonia still remain the subject of close interest of researchers. The review provides up-to-date information about the etiology and pathogenesis of muscle dystonia. Recent changes in the genetic nomenclature of dystonia are described. Modern ideas about the pathogenetic significance of such mechanisms as abnormalities of neural inhibition, disturbances of sensorimotor integration, and abnormalities of neural plasticity are considered. Recent research data support the concept of systemic sensorimotor disintegration, including not only basal ganglia dysfunction, but also motor network disorders involving the cerebellum, cortex, midbrain, thalamus and other areas.

WDR45, one gene associated with multiple neurodevelopmental disorders

The WDR45 gene is localized on the X-chromosome and variants in this gene are linked to six different neurodegenerative disorders, i.e., ß-propeller protein associated neurodegeneration, Rett-like syndrome, intellectual disability, and epileptic encephalopathies including developmental and epileptic encephalopathy, early-onset epileptic encephalopathy and West syndrome and potentially also specific malignancies. WDR45/WIPI4 is a WD-repeat β-propeller protein that belongs to the WIPI (WD repeat domain, phosphoinositide interacting) family. The precise cellular function of WDR45 is still largely unknown, but deletions or conventional variants in WDR45 can lead to macroautophagy/autophagy defects, malfunctioning mitochondria, endoplasmic reticulum stress and unbalanced iron homeostasis, suggesting that this protein functions in one or more pathways regulating directly or indirectly those processes. As a result, the underlying cause of the WDR45-associated disorders remains unknown. In this review, we summarize the current knowledge about the cellular and physiological functions of WDR45 and highlight how genetic variants in its encoding gene may contribute to the pathophysiology of the associated diseases. In particular, we connect clinical manifestations of the disorders with their potential cellular origin of malfunctioning and critically discuss whether it is possible that one of the most prominent shared features, i.e., brain iron accumulation, is the primary cause for those disorders.

Abbreviations: ATG/Atg: autophagy related; BPAN: ß-propeller protein associated neurodegeneration; CNS: central nervous system; DEE: developmental and epileptic encephalopathy; EEG: electroencephalograph; ENO2/neuron-specific enolase, enolase 2; EOEE: early-onset epileptic encephalopathy; ER: endoplasmic reticulum; ID: intellectual disability; IDR: intrinsically disordered region; MRI: magnetic resonance imaging; NBIA: neurodegeneration with brain iron accumulation; NCOA4: nuclear receptor coactivator 4; PtdIns3P: phosphatidylinositol-3-phosphate; RLS: Rett-like syndrome; WDR45: WD repeat domain 45; WIPI: WD repeat domain, phosphoinositide interacting

Cyclic Phosphopantothenic Acid Prodrugs for Treatment of Pantothenate Kinase-Associated Neurodegeneration

Mutations in the human PANK2 gene are implicated in neurodegenerative diseases such as pantothenate kinase-associated neurodegeneration (PKAN) and result in low levels of coenzyme-A (CoA) in the CNS due to impaired production of phosphopantothenic acid (PPA) from vitamin B5. Restoration of central PPA levels by delivery of exogenous PPA is a recent strategy to reactivate CoA biosynthesis in PKAN patients. Fosmetpantotenate is an oral PPA prodrug. We report here the development of a new PANk2^-/- knockout model that allows CoA regeneration in brain cells to be evaluated and describe two new series of cyclic phosphate prodrugs of PPA capable of regenerating excellent levels of CoA in this system. A proof-of-concept study in mouse demonstrates the potential of this new class of prodrugs to deliver PPA to the brain following oral administration and confirms incorporation of the prodrug-derived PPA into CoA.

Mitochondrial Dysfunction, Oxidative Stress and Neuroinflammation in Neurodegeneration with Brain Iron Accumulation (NBIA)

The syndromes of neurodegeneration with brain iron accumulation (NBIA) encompass a group of invalidating and progressive rare diseases that share the abnormal accumulation of iron in the basal ganglia. The onset of NBIA disorders ranges from infancy to adulthood. Main clinical signs are related to extrapyramidal features (dystonia, parkinsonism and choreoathetosis), and neuropsychiatric abnormalities. Ten NBIA forms are widely accepted to be caused by mutations in the genes PANK2, PLA2G6, WDR45, C19ORF12, FA2H, ATP13A2, COASY, FTL1, CP, and DCAF17. Nonetheless, many patients remain without a conclusive genetic diagnosis, which shows that there must be additional as yet undiscovered NBIA genes. In line with this, isolated cases of known monogenic disorders, and also, new genetic diseases, which present with abnormal brain iron phenotypes compatible with NBIA, have been described. Several pathways are involved in NBIA syndromes: iron and lipid metabolism, mitochondrial dynamics, and autophagy. However, many neurodegenerative conditions share features such as mitochondrial dysfunction and oxidative stress, given the bioenergetics requirements of neurons. This review aims to describe the existing link between the classical ten NBIA forms by examining their connection with mitochondrial impairment as well as oxidative stress and neuroinflammation.

PANK2 p.A170fs：a novel pathogenetic mutation, compound with PANK2 p.R440P, causing pantothenate kinase Associated neurodegeneration in a Chinese family

AIM

Pantothenate kinase associated neurodegeneration (PKAN) is a severe autosomal recessive rare disease and characterized by iron accumulation in the basal ganglia. To investigate the pathogenesis of this disease in two sibling patients with PANK in a Chinese family, whole-exome variant detection and functional analysis were performed.

MATERIALS AND METHODS

Clinical and radiographic investigations were performed in the two brother patients. Whole exome sequencing (WES) was used in mutation detection, and the mutations were confirmed by Sanger sequencing. A longevity cohort genetic database was applied as Chinese urban controls. Bioinformatic analysis was performed to predict the pathogenicity.

RESULTS

Compound heterozygous mutations of PANK2 were detected in two sibling brothers with PKAN in a Chinese family: c.510_522del (p.A170fs) and c.1319G > C (p.R440P) in the transcript NM_153638. PANK2: c.510_522del (p.A170fs) was absent in public data and the Chinese urban controls. Bioinformatics analysis showed that the above two variants were pathogenicity.

CONCLUSIONS

We identified a rare compound heterozygous combination of PANK2 mutations found in a Chinese family in which two sibling brothers suffered from PKAN. PANK2 c.510_522del (p.A170fs) was the first reported to be a PKAN pathogenic variant.

Single-center experience with Beta-propeller protein-associated neurodegeneration (BPAN); expanding the phenotypic spectrum

Beta-propeller protein-associated neurodegeneration (BPAN) is a subtype of neurodegeneration with brain iron accumulation (NBIA) that presents with childhood developmental delay (especially speech delay), occasionally associated with epileptic encephalopathy, autism, or Rett-like syndrome. The majority of children described to date have been severely affected, with little to no expressive speech function, severe developmental delay, and cognitive impairment. Herein, five additional patients with BPAN identified in the same center in Canada are described, four with the typical severe phenotype and one with a milder phenotype. Our findings provide further evidence that a spectrum of severity exists for this rare and newly described condition. Challenges in identifying iron accumulation on brain MRI are also addressed. Additionally, the importance of including the WDR45 gene on epilepsy and Rett-like syndrome genetic panels is highlighted.

GJA1 Variants Cause Spastic Paraplegia Associated with Cerebral Hypomyelination

Oculodentodigital dysplasia is an autosomal dominant disorder due to GJA1 variants characterized by dysmorphic features. Neurologic symptoms have been described in some patients but without a clear neuroimaging pattern. To understand the pathophysiology underlying neurologic deficits in oculodentodigital dysplasia, we studied 8 consecutive patients presenting with hereditary spastic paraplegia due to GJA1 variants. Clinical disease severity was highly variable. Cerebral MR imaging revealed variable white matter abnormalities, consistent with a hypomyelination pattern, and bilateral hypointense signal of the basal ganglia on T2-weighted images and/or magnetic susceptibility sequences, as seen in neurodegeneration with brain iron accumulation diseases. Patients with the more prominent basal ganglia abnormalities were the most disabled ones. This study suggests that GJA1-related hereditary spastic paraplegia is a complex neurodegenerative disease affecting both the myelin and the basal ganglia. GJA1 variants should be considered in patients with hereditary spastic paraplegia presenting with brain hypomyelination, especially if associated with neurodegeneration and a brain iron accumulation pattern.

Overexpression of Human Mutant PANK2 Proteins Affects Development and Motor Behavior of Zebrafish Embryos

Pantothenate Kinase-Associated Neurodegeneration (PKAN) is a genetic and early-onset neurodegenerative disorder characterized by iron accumulation in the basal ganglia. It is due to mutations in Pantothenate Kinase 2 (PANK2), an enzyme that catalyzes the phosphorylation of vitamin B5, first and essential step in coenzyme A (CoA) biosynthesis. Most likely, an unbalance of the neuronal levels of this important cofactor represents the initial trigger of the neurodegenerative process, yet a complete understanding of the connection between PANK2 malfunctioning and neuronal death is lacking. Most PKAN patients carry mutations in both alleles and a loss of function mechanism is proposed to explain the pathology. When PANK2 mutants were analyzed for stability, dimerization capacity, and enzymatic activity in vitro, many of them showed properties like the wild-type form. To further explore this aspect, we overexpressed the wild-type protein, two mutant forms with reduced kinase activity and two retaining the catalytic activity in zebrafish embryos and analyzed the morpho-functional consequences. While the wild-type protein had no effects, all mutant proteins generated phenotypes that partially resembled those observed in pank2 and coasy morphants and were rescued by CoA and vitamin B5 supplementation. The overexpression of PANK2 mutant forms appears to be associated with perturbation in CoA availability, irrespective of their catalytic activity.

Psychiatric Treatment and Management of Psychiatric Comorbidities of Movement Disorders

Pediatric movement disorders may present with psychiatric symptoms at many points during the course of the disease. For the relatively common pediatric movement disorder, Tourette syndrome, psychiatric comorbidities are well-described and treatment is well-studied. Managing these comorbidities may be more effective than improving the movements themselves. For more uncommon movement disorders, such as juvenile-onset Huntington disease, treatment of psychiatric comorbidities is not well-characterized, and best-practice recommendations are not available. For the least common movement disorders, such as childhood neurodegeneration with brain iron accumulation, psychiatric features may be nonspecific so that underlying diagnosis may be apparent only after recognition of other symptoms. However, psychiatric medication, psychotherapy, and psychosocial support for these disorders may prove helpful to many children and adolescents.

Fosmetpantotenate (RE-024), a phosphopantothenate replacement therapy for pantothenate kinase-associated neurodegeneration: Mechanism of action and efficacy in nonclinical models

In cells, phosphorylation of pantothenic acid to generate phosphopantothenic acid by the pantothenate kinase enzymes is the first step in coenzyme A synthesis. Pantothenate kinase 2, the isoform localized in neuronal cell mitochondria, is dysfunctional in patients with pantothenate kinase-associated neurodegeneration. Fosmetpantotenate is a phosphopantothenic acid prodrug in clinical development for treatment of pantothenate kinase-associated neurodegeneration, which aims to replenish phosphopantothenic acid in patients. Fosmetpantotenate restored coenzyme A in short-hairpin RNA pantothenate kinase 2 gene-silenced neuroblastoma cells and was permeable in a blood-brain barrier model. The rate of fosmetpantotenate metabolism in blood is species-dependent. Following up to 700 mg/kg orally, blood exposure to fosmetpantotenate was negligible in rat and mouse, but measurable in monkey. Consistent with the difference in whole blood half-life, fosmetpantotenate dosed orally was found in the brains of the monkey (striatal dialysate) but was absent in mice. Following administration of isotopically labeled-fosmetpantotenate to mice, ~40% of liver coenzyme A (after 500 mg/kg orally) and ~50% of brain coenzyme A (after 125 μg intrastriatally) originated from isotopically labeled-fosmetpantotenate. Additionally, 10-day dosing of isotopically labeled-fosmetpantotenate, 12.5 μg, intracerebroventricularly in mice led to ~30% of brain coenzyme A containing the stable isotopic labels. This work supports the hypothesis that fosmetpantotenate acts to replace reduced phosphopantothenic acid in pantothenate kinase 2-deficient tissues.

A pilot trial of deferiprone in pantothenate kinase-associated neurodegeneration patients

Pantothenate kinase-associated neurodegeneration (PKAN) is the most common form of neurodegeneration with brain iron accumulation, it is an autosomal recessive disease due to mutation in PANK 2 on chromosome 20, which causes the accumulation of iron in basal ganglia and production of free radicals that cause degeneration of the cells. Deferiprone is an iron chelator that was used in treatment of thalassemia patients, it can cross the blood-brain barrier and reverse the iron deposition in the brain. Five patients with genetically confirmed PKAN received 15 mg/kg deferiprone twice daily. All patients were examined at baseline, 12 and 18 months and magnetic resonance imaging (MRI) was done at the baseline and after 18 months. In our study qualitative evaluation of MRI showed that deferiprone was able to reduce the iron load in globus pallidus of all the patients and the results of clinical rating scales show that in four patients, there is an improvement in the first 12 months. The results of our paper show that deferiprone can prevent the progression of the disease.

First successful trial of preimplantation genetic diagnosis for pantothenate kinase-associated neurodegeneration

PURPOSE

We aim to present a case of a healthy infant born after intracytoplasmic sperm injection-in vitro fertilization (ICSI-IVF) with a preimplantation genetic diagnosis (PGD) for pantothenate kinase-associated neurodegeneration (PKAN) due to PANK2 mutation.

METHODS

ICSI-IVF was performed on a Thai couple, 34-year-old female and 33-year-old male, with a family history of PKAN in their first child. Following fertilization, each of the embryos were biopsied in the cleavage stage and subsequently processed for whole-genome amplification. Genetic status of the embryos was diagnosed by linkage analysis and direct mutation testing using primer extension-based mini-sequencing. Comprehensive chromosomal aneuploidy screening was performed using a next-generation sequencing-based strategy.

RESULTS

Only a single cycle of ICSI-IVF was processed. There were seven embryos from this couple-two were likely affected, three were likely carriers, one was likely unaffected, and one failed in target genome amplification. Aneuploidy screening was performed before making a decision on embryo transfer, and only one unaffected embryo passed the screening. That embryo was transferred in a frozen thawed cycle, and the pregnancy was successful. The diagnosis was confirmed by amniocentesis, which presented with a result consistent with PGD. At 38 weeks of gestational age, a healthy male baby was born. Postnatal genetic confirmation was also consistent with PGD and the prenatal results. At the age of 24 months, the baby presented with normal growth and development lacking any neurological symptoms.

CONCLUSIONS

We report the first successful trial of PGD for PKAN in a developing country using linkage analysis and mini-sequencing in cleavage stage embryos.

Exploring Missense Mutations in Tyrosine Kinases Implicated with Neurodegeneration

Protein kinases are one of the largest families of evolutionarily related proteins and the third most common protein class of human genome. All the protein kinases share the same structural organization. They are made up of an extracellular domain, transmembrane domain and an intra cellular kinase domain. Missense mutations in these kinases have been studied extensively and correlated with various neurological disorders. Individual mutations in the kinase domain affect the functions of protein. The enhanced or reduced expression of protein leads to hyperactivation or inactivation of the signalling pathways, resulting in neurodegeneration. Here, we present extensive analyses of missense mutations in the tyrosine kinase focussing on the neurodegenerative diseases encompassing structure function relationship. This is envisaged to enhance our understanding about the neurodegeneration and possible therapeutic measures.

Mutations in POMGNT1 cause non-syndromic retinitis pigmentosa

A growing number of human diseases have been linked to defects in protein glycosylation that affects a wide range of organs. Among them, O-mannosylation is an unusual type of protein glycosylation that is largely restricted to the muscular and nerve system. Consistently, mutations in genes involved in the O-mannosylation pathway result in infantile-onset, severe developmental defects involving skeleton muscle, brain and eye, such as the muscle-eye-brain disease (MIM no. 253280). However, the functional importance of O-mannosylation in these tissues at later stages remains largely unknown. In our study, we have identified recessive mutations in POMGNT1, which encodes an essential component in O-mannosylation pathway, in three unrelated families with autosomal recessive retinitis pigmentosa (RP), but without extraocular involvement. Enzymatic assay of these mutant alleles demonstrate that they greatly reduce the POMGNT1 enzymatic activity and are likely to be hypomorphic. Immunohistochemistry shows that POMGNT1 is specifically expressed in photoreceptor basal body. Taken together, our work identifies a novel disease-causing gene for RP and indicates that proper protein O-mannosylation is not only essential for early organ development, but also important for maintaining survival and function of the highly specialized retinal cells at later stages.

WDR45 mutations in Rett (-like) syndrome and developmental delay: Case report and an appraisal of the literature

Mutations in the WDR45 gene have been identified as causative for the only X-linked type of neurodegeneration with brain iron accumulation (NBIA), clinically characterized by global developmental delay in childhood, followed by a secondary neurological decline with parkinsonism and/or dementia in adolescence or early adulthood. Recent reports suggest that WDR45 mutations are associated with a broader phenotypic spectrum. We identified a novel splice site mutation (c.440-2 A > G) in a 5-year-old Argentinian patient with Rett-like syndrome, exhibiting developmental delay, microcephaly, seizures and stereotypic hand movements, and discuss this finding, together with a review of the literature. Additional patients with a clinical diagnosis of Rett (-like) syndrome were also found to carry WDR45 mutations before (or without) clinical decline or signs of iron accumulation by magnetic resonance imaging (MRI). This information indicates that WDR45 mutations should be added to the growing list of genetic alterations linked to Rett-like syndrome. Further, clinical symptoms associated with WDR45 mutations ranged from early-onset epileptic encephalopathy in a male patient with a deletion of WDR45 to only mild cognitive delay in a female patient, suggesting that analysis of this gene should be considered more often in patients with developmental delay, regardless of severity. The increasing use of next generation sequencing technologies as well as longitudinal follow-up of patients with an early diagnosis will help to gain additional insight into the phenotypic spectrum associated with WDR45 mutations.

Knock-down of pantothenate kinase 2 severely affects the development of the nervous and vascular system in zebrafish, providing new insights into PKAN disease

Pantothenate Kinase Associated Neurodegeneration (PKAN) is an autosomal recessive disorder with mutations in the pantothenate kinase 2 gene (PANK2), encoding an essential enzyme for Coenzyme A (CoA) biosynthesis. The molecular connection between defects in this enzyme and the neurodegenerative phenotype observed in PKAN patients is still poorly understood. We exploited the zebrafish model to study the role played by the pank2 gene during embryonic development and get new insight into PKAN pathogenesis. The zebrafish orthologue of hPANK2 lies on chromosome 13, is a maternal gene expressed in all development stages and, in adult animals, is highly abundant in CNS, dorsal aorta and caudal vein. The injection of a splice-inhibiting morpholino induced a clear phenotype with perturbed brain morphology and hydrocephalus; edema was present in the heart region and caudal plexus, where hemorrhages with reduction of blood circulation velocity were detected. We characterized the CNS phenotype by studying the expression pattern of wnt1 and neurog1 neural markers and by use of the Tg(neurod:EGFP/sox10:dsRed) transgenic line. The results evidenced that downregulation of pank2 severely impairs neuronal development, particularly in the anterior part of CNS (telencephalon). Whole-mount in situ hybridization analysis of the endothelial markers cadherin-5 and fli1a, and use of Tg(fli1a:EGFP/gata1a:dsRed) transgenic line, confirmed the essential role of pank2 in the formation of the vascular system. The specificity of the morpholino-induced phenotype was proved by the restoration of a normal development in a high percentage of embryos co-injected with pank2 mRNA. Also, addition of pantethine or CoA, but not of vitamin B5, to pank2 morpholino-injected embryos rescued the phenotype with high efficiency. The zebrafish model indicates the relevance of pank2 activity and CoA homeostasis for normal neuronal development and functioning and provides evidence of an unsuspected role for this enzyme and its product in vascular development.

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Zebrafish pank2 gene is highly expressed in the CNS and the main vascular structures.

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Pank2 down-regulation severely affects the development of the forebrain.

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Pank2 down-regulation affects the dorsal aorta, caudal vein and inter-somitic vessels.

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Pantethine and Coenzyme A restore the normal development in the absence of pank2 expression.

Screening for THAP1 Mutations in Polish Patients with Dystonia Shows Known and Novel Substitutions

The aim of this study was to assess the presence of DYT6 mutations in Polish patients with isolated dystonia and to characterize their phenotype. We sequenced THAP1 exons 1, 2 and 3 including exon-intron boundaries and 5'UTR fragment in 96 non-DYT1 dystonia patients. In four individuals single nucleotide variations were identified. The coding substitutions were: c. 238A>G (p.Ile80Val), found in two patients, and c.167A>G (p.Glu56Gly), found in one patient. The same variations were present also in the patients' symptomatic as well as asymptomatic relatives. Mutation penetration in the analyzed families was 50-66.7%. In the fourth patient, a novel c.-249C>A substitution in the promoter region was identified. The patient, initially suspected of idiopathic isolated dystonia, finally presented with pantothenate kinase 2-associated neurodegeneration phenotype and was a carrier of two PANK2 mutations. This is the first identified NBIA1 case carrying mutations in both PANK2 and THAP1 genes. In all symptomatic THAP1 mutation carriers (four probands and their three affected relatives) the first signs of dystonia occurred before the age of 23. A primary localization typical for DYT6 dystonia was observed in six individuals. Five subjects developed the first signs of dystonia in the upper limb. In one patient the disease began from laryngeal involvement. An uncommon primary involvement of lower limb was noted in the THAP1 and PANK2 mutations carrier. Neither of these THAP1 substitutions were found in 150 unrelated healthy controls. To the contrary, we identified a heterozygous C/T genotype of c.57C>T single nucleotide variation (p.Pro19Pro, rs146087734) in one healthy control, but in none of the patients. Therefore, a previously proposed association between this substitution and DYT6 dystonia seems unlikely. We found also no significant difference between cases and controls in genotypes distribution of the two-nucleotide -237-236 GA>TT (rs370983900 & rs1844977763) polymorphism.

Grey matter alterations in patients with Pantothenate Kinase-Associated Neurodegeneration (PKAN)

BACKGROUND

Pantothenate Kinase-Associated Neurodegeneration (PKAN) is a rare heritable disease marked by dystonia and loss of movement control. In contrast to the well-known "Eye-of-the-Tiger" sign affecting the globus pallidus, little is known about other deviations of brain morphology, especially about grey matter changes.

METHODS

We investigated 29 patients with PKAN and 29 age-matched healthy controls using Magnet Resonance Imaging and Voxel-Based Morphometry.

RESULTS

As compared to controls, children with PKAN showed increased grey matter density in the putamen and nucleus caudatus and adults with PKAN showed increased grey matter density in the ventral part of the anterior cingulate cortex. A multiple regression analysis with dystonia score as predictor showed grey matter reduction in the cerebellum, posterior cingulate cortex, superior parietal lobule, pars triangularis and small frontal and temporal areas and an analysis with age as predictor showed grey matter decreases in the putamen, nucleus caudatus, supplementary motor area and anterior cingulate cortex.

CONCLUSIONS

The grey matter increases may be regarded as a secondary phenomenon compensating the increased activity of the motor system due to a reduced inhibitory output of the globus pallidus. With increasing age, the grey matter reduction of cortical midline structures however might contribute to the progression of dystonic symptoms due to loss of this compensatory control.

Iron deposits in the chronically inflamed central nervous system and contributes to neurodegeneration

Neurodegenerative disorders are characterized by the presence of inflammation in areas with neuronal cell death and a regional increase in iron that exceeds what occurs during normal aging. The inflammatory process accompanying the neuronal degeneration involves glial cells of the central nervous system (CNS) and monocytes of the circulation that migrate into the CNS while transforming into phagocytic macrophages. This review outlines the possible mechanisms responsible for deposition of iron in neurodegenerative disorders with a main emphasis on how iron-containing monocytes may migrate into the CNS, transform into macrophages, and die out subsequently to their phagocytosis of damaged and dying neuronal cells. The dying macrophages may in turn release their iron, which enters the pool of labile iron to catalytically promote formation of free-radical-mediated stress and oxidative damage to adjacent cells, including neurons. Healthy neurons may also chronically acquire iron from the extracellular space as another principle mechanism for oxidative stress-mediated damage. Pharmacological handling of monocyte migration into the CNS combined with chelators that neutralize the effects of extracellular iron occurring due to the release from dying macrophages as well as intraneuronal chelation may denote good possibilities for reducing the deleterious consequences of iron deposition in the CNS.

Decreased serum hepcidin concentration correlates with brain iron deposition in patients with HBV-related cirrhosis

Purpose

Excessive brain iron accumulation contributes to cognitive impairments in hepatitis B virus (HBV)-related cirrhotic patients. The underlying mechanism remains unclear. Hepcidin, a liver-produced, 25-aminoacid peptide, is the major regulator of systemic iron metabolism. Abnormal hepcidin level is a key factor in some body iron accumulation or deficiency disorders, especially in those associated with liver diseases. Our study was aimed to explore the relationship between brain iron content in patients with HBV-related cirrhosis and serum hepcidin level.

Methods

Seventy HBV-related cirrhotic patients and forty age- sex-matched healthy controls were enrolled. Brain iron content was quantified by susceptibility weighted phase imaging technique. Serum hepcidin as well as serum iron, serum transferrin, ferritin, soluble transferrin receptor, total iron binding capacity, and transferrin saturation were tested in thirty cirrhotic patients and nineteen healthy controls. Pearson correlation analysis was performed to investigate correlation between brain iron concentrations and serum hepcidin, or other iron parameters.

Results

Cirrhotic patients had increased brain iron accumulation compared to controls in the left red nuclear, the bilateral substantia nigra, the bilateral thalamus, the right caudate, and the right putamen. Cirrhotic patients had significantly decreased serum hepcidin concentration, as well as lower serum transferring level, lower total iron binding capacity and higher transferrin saturation, compared to controls. Serum hepcidin level negatively correlated with the iron content in the right caudate, while serum ferritin level positively correlated with the iron content in the bilateral putamen in cirrhotic patients.

Conclusions

Decreased serum hepcidin level correlated with excessive iron accumulation in the basal ganglia in HBV-related cirrhotic patients. Our results indicated that systemic iron overload underlined regional brain iron repletion. Serum hepcidin may be a clinical biomarker for brain iron deposition in cirrhotic patients, which may have therapeutic potential.

PANK2 and C19orf12 mutations are common causes of neurodegeneration with brain iron accumulation

BACKGROUND

Neurodegeneration with brain iron accumulation (NBIA) constitutes a group of neurodegenerative disorders with pronounced iron deposition in the basal ganglia. PANK2 mutations are the most common cause of these disorders. C19orf12 was recently reported as another causative gene. We present phenotypic data and results of screening of PANK2 and C19orf12 in 11 unrelated Iranian NBIA patients.

METHODS

Phenotypic data were obtained by neurologic examination, magnetic resonance imaging, and interviews. Mutation screening of PANK2 and C19orf12 was performed by sequencing.

RESULTS

PANK2 and C19orf12 mutations were found in 7 and 4 patients, respectively. Phenotypic comparisons suggest that C19orf12 mutations as compared with PANK2 mutations result in a milder disease course.

CONCLUSIONS

Mutations in both PANK2 and C19orf12 contributed significantly to NBIA in the Iranian patients. To the best of our knowledge, this is the first genetic analysis reported on a cohort of NBIA patients from the Middle East.

Iron and neurodegeneration: from cellular homeostasis to disease

Accumulation of iron (Fe) is often detected in the brains of people suffering from neurodegenerative diseases. High Fe concentrations have been consistently observed in Parkinson's, Alzheimer's, and Huntington's diseases; however, it is not clear whether this Fe contributes to the progression of these diseases. Other conditions, such as Friedreich's ataxia or neuroferritinopathy are associated with genetic factors that cause Fe misregulation. Consequently, excessive intracellular Fe increases oxidative stress, which leads to neuronal dysfunction and death. The characterization of the mechanisms involved in the misregulation of Fe in the brain is crucial to understand the pathology of the neurodegenerative disorders and develop new therapeutic strategies. Saccharomyces cerevisiae, as the best understood eukaryotic organism, has already begun to play a role in the neurological disorders; thus it could perhaps become a valuable tool also to study the metalloneurobiology.

A novel type of familial proximal axonal dystrophy: three cases and a review of the axonal dystrophies

Three related infants of Roma ancestry, two of them siblings, showed hypotonia, predominantly axial, from birth, difficulty swallowing, myoclonic seizures, and respiratory difficulty. Dysmorphic features, principally micrognathia were present. EEGs showed focal epileptiform abnormalities. All three died in their 5th month from respiratory insufficiency complicated by pneumonia. Autopsy showed small brains without malformation. Microscopy revealed numerous axonal spheroids involving particularly the brain stem and spinal cord, with especial prominence in the middle cerebellar peduncle, the anterior part of the thalamic reticular nuclei, and the anterior horns and columns of the spinal cord. Spheroids that appeared to be on axons of lower motor neurons were especially large. No spheroids were seen in peripheral nerves; electron microscopy did not show spheroids in skin. By electron microscopy spheroids contained neurofilaments, sparse mitochondria, and electron dense granules. The material did not allow identification of microtubules. Closely packed vesicles excluded neurofilamanets from the center of many spheroids, especially in the middle cerebellar peduncle. Sprouting of axons from the surface of many spheroids was seen. This disease is distinct from the well described type of infantile neuroaxonal dystrophy (Seitelberger's disease) in view of the distribution of spheroids, presence of spheroids on proximal rather than distal parts of axons, sparing of the peripheral nerves, lack of staining for synuclein, presence of sprouting, and lack of membranous profiles in the spheroids. A review of reported types of axonal dystrophy has not shown identical cases.

Involvement of globus pallidus and midbrain nuclei in pantothenate kinase-associated neurodegeneration: measurement of T2 and T2* time

PURPOSE

To quantify involvement of globus pallidus and two midbrain nuclei (substantia nigra and red nucleus) in Pantothenate Kinase-Associated Neurodegeneration (PKAN).

MATERIAL AND METHODS

We performed T2 and T2* weighted imaging with calculation of the corresponding relaxation times on a subset of 5 patients from a larger group of 20 patients with PKAN from the southwest part of the Dominican Republic. Examinations were carried out on a 3T scanner and included a multi-echo spin-echo as well as a multi-echo gradient echo sequence. Results were compared to a control group of 19 volunteers.

RESULTS

T2 and T2* weighted sequences showed abnormal signal reduction in the globus pallidus of all patients. On T2* weighted imaging, abnormal signal in the substantia nigra could reliably be detected in 75% of cases, but differentiation from normal was less reliable in T2 weighted scans. Correspondingly, relaxation times differed from normal with very high significance (p < 0.0001) in the globus pallidus, but with with less significance in the substantia nigra (p ≤ 0.03). The red nucleus was not affected.

CONCLUSIONS

Signal reduction in the globus pallidus, which probably is due to abnormal accumulation of iron, is severe in PKAN and can be differentiated from normal with high reliability. The substantia nigra is affected to a lesser degree, and the red nucleus is not involved. The reason for this selective susceptibility of normally iron-rich brain structures for pathological accumulation of iron remains speculative. Our quantitative results might be helpful to assess the value of an iron chelation approach to therapy.

Missense PANK2 mutation without "eye of the tiger" sign: MR findings in a large group of patients with pantothenate kinase-associated neurodegeneration (PKAN)

PURPOSE

To present some unusual MR findings in a group of patients from the south-west of the Dominican Republic suffering from Pantothenate Kinase Associated Neurodegeneration (PKAN).

MATERIALS AND METHODS

Twenty patients and one preclinical case homozygous for the PANK2 mutation, 13 heterozygous gene carriers and 14 healthy volunteers were scanned prospectively using a 3 Tesla system.

RESULTS

All patients showed the typical signal reduction within the globus pallidus and the substantia nigra. A surprising finding was the absence of the bright spot ("tiger's eye") in the medial part of the pallidum in 6 patients, but not in the preclinical case. Both fractional anisotropy (FA) and mean diffusivity (MD) were increased with high significance in the globus pallidus, whereas a reduction of FA in the anterior parts of the internal capsule was accompanied by an elevation of MD.

CONCLUSION

Our findings support the hypothesis that the absence of the "tiger's eye" in PKAN might be secondary, probably caused by an increased accumulation of iron. This could artificially increase FA and MD values and change fiber tracking results. Except for the fronto-basal tracts, white matter was preserved well. This encouraging finding might support efforts to develop further therapeutic strategies in this devastating dystonia.

Twenty classic signs in neuroradiology: A pictorial essay

In this article we describe 20 classic signs in neuroradiology and provide illustrations of each; we also discuss the causes for their appearance, their reliability and sensitivity, and the differential diagnoses to be considered when they are encountered on imaging.

Neurodegeneration with brain iron accumulation - clinical syndromes and neuroimaging

Iron participates in a wide array of cellular functions and is essential for normal neural development and physiology. However, if inappropriately managed, the transition metal is capable of generating neurotoxic reactive oxygen species. A number of hereditary conditions perturb body iron homeostasis and some, collectively referred to as neurodegeneration with brain iron accumulation (NBIA), promote pathological deposition of the metal predominantly or exclusively within the central nervous system (CNS). In this article, we discuss seven NBIA disorders with emphasis on the clinical syndromes and neuroimaging. The latter primarily entails magnetic resonance scanning using iron-sensitive sequences. The conditions considered are Friedreich ataxia (FA), pantothenate kinase 2-associated neurodegeneration (PKAN), PLA2G6-associated neurodegeneration (PLAN), FA2H-associated neurodegeneration (FAHN), Kufor-Rakeb disease (KRD), aceruloplasminemia, and neuroferritinopathy. An approach to differential diagnosis and the status of iron chelation therapy for several of these entities are presented. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.

Pantothenate kinase 1 is required to support the metabolic transition from the fed to the fasted state

Coenzyme A (CoA) biosynthesis is regulated by the pantothenate kinases (PanK), of which there are four active isoforms. The PanK1 isoform is selectively expressed in liver and accounted for 40% of the total PanK activity in this organ. CoA synthesis was limited using a Pank1(-/-) knockout mouse model to determine whether the regulation of CoA levels was critical to liver function. The elimination of PanK1 reduced hepatic CoA levels, and fasting triggered a substantial increase in total hepatic CoA in both Pank1(-/-) and wild-type mice. The increase in hepatic CoA during fasting was blunted in the Pank1(-/-) mouse, and resulted in reduced fatty acid oxidation as evidenced by abnormally high accumulation of long-chain acyl-CoAs, acyl-carnitines, and triglycerides in the form of lipid droplets. The Pank1(-/-) mice became hypoglycemic during a fast due to impaired gluconeogenesis, although ketogenesis was normal. These data illustrate the importance of PanK1 and elevated liver CoA levels during fasting to support the metabolic transition from glucose utilization and fatty acid synthesis to gluconeogenesis and fatty acid oxidation. The findings also suggest that PanK1 may be a suitable target for therapeutic intervention in metabolic disorders that feature hyperglycemia and hypertriglyceridemia.

Pantothenate kinase-2 (Pank2) silencing causes cell growth reduction, cell-specific ferroportin upregulation and iron deregulation

Pantothenate kinase 2 (Pank2) is a mitochondrial enzyme that catalyses the first regulatory step of Coenzyme A synthesis and that is responsible for a genetic movement disorder named Pank-associated neurodegeneration (PKAN). This is characterized by abnormal iron accumulation in the brain, particularly in the globus pallidus. We downregulated Pank2 in some cell lines by using specific siRNAs to study its effect on iron homeostasis. In HeLa cells this caused a reduction of cell proliferation and of aconitase activity, signs of cytosolic iron deficiency without mitochondrial iron deposition, and a 12-fold induction of ferroportin mRNA. Pank2 silencing caused a strong induction of ferroportin mRNA also in hepatoma HepG2, a modest one in neuroblastoma SH-SY5Y and none in glioma U373 cells. A reduction of cell growth was observed in all these cell types. The strong Pank2-mediated alteration of ferroportin expression in some cell types might alter iron transfer to the brain and be connected with brain iron accumulation.

Iron in neuronal function and dysfunction

Iron (Fe) is an essential element for many metabolic processes, serving as a cofactor for heme and nonheme proteins. Cellular iron deficiency arrests cell growth and leads to cell death; however, like most transition metals, an excess of intracellular iron is toxic. The ability of Fe to accept and donate electrons can lead to the formation of reactive nitrogen and oxygen species, and oxidative damage to tissue components; contributing to disease and, perhaps, aging itself. It has also been suggested that iron-induced oxidative stress can play a key role in the pathogenesis of several neurodegenerative diseases. Iron progressively accumulates in the brain both during normal aging and neurodegenerative processes. However, iron accumulation occurs without the concomitant increase in tissue ferritin, which could increase the risk of oxidative stress. Moreover, high iron concentrations in the brain have been consistently observed in Alzheimer's disease (AD) and Parkinson's disease (PD). In this regard, metalloneurobiology has become extremely important in understanding the role of iron in the onset and progression of neurodegenerative diseases. Neurons have developed several protective mechanisms against oxidative stress, among them the activation of cellular signaling pathways. The final response will depend on the identity, intensity, and persistence of the oxidative insult. The characterization of the mechanisms involved in high iron induced in neuronal dysfunction and death is central to understanding the pathology of a number of neurodegenerative disorders.