Frataxin deficiency leads to reduced expression and impaired translocation of NF-E2-related factor (Nrf2) in cultured motor neurons

Oxidative stress has been implicated in the pathogenesis of Friedreich's Ataxia (FRDA), a neurodegenerative disease caused by the decreased expression of frataxin, a mitochondrial protein responsible of iron homeostasis. Under conditions of oxidative stress, the activation of the transcription factor NF-E2-related factor (Nrf2) triggers the antioxidant cellular response by inducing antioxidant response element (ARE) driven genes. Increasing evidence supports a role for the Nrf2-ARE pathway in neurodegenerative diseases. In this study, we analyzed the expression and the distribution of Nrf2 in silenced neurons for frataxin gene. Decreased Nrf2 mRNA content and a defective activation after treatment with pro-oxidants have been evidenced in frataxin-silenced neurons by RT-PCR and confocal microscopy. The loss of Nrf2 in FRDA may greatly enhance the cellular susceptibility to oxidative stress and make FRDA neurons more vulnerable to injury. Our findings may help to focus on this promising target, especially in its emerging role in the neuroprotective response.

Pontocerebellar hypoplasia type 6 caused by mutations in RARS2: definition of the clinical spectrum and molecular findings in five patients

Recessive mutations in the mitochondrial arginyl-transfer RNA synthetase (RARS2) gene have been associated with early onset encephalopathy with signs of oxidative phosphorylation defects classified as pontocerebellar hypoplasia 6. We describe clinical, neuroimaging and molecular features on five patients from three unrelated families who displayed mutations in RARS2. All patients rapidly developed a neonatal or early-infantile epileptic encephalopathy with intractable seizures. The long-term follow-up revealed a virtual absence of psychomotor development, progressive microcephaly, and feeding difficulties. Mitochondrial respiratory chain enzymes in muscle and fibroblasts were normal in two. Blood and CSF lactate was abnormally elevated in all five patients at early stages while appearing only occasionally abnormal with the progression of the disease. Cerebellar vermis hypoplasia with normal aspect of the cerebral and cerebellar hemispheres appeared within the first months of life at brain MRI. In three patients follow-up neuroimaging revealed a progressive pontocerebellar and cerebral cortical atrophy. Molecular investigations of RARS2 disclosed the c.25A>G/p.I9V and the c.1586+3A>T in family A, the c.734G>A/p.R245Q and the c.1406G>A/p.R469H in family B, and the c.721T>A/p.W241R and c.35A>G/p.Q12R in family C. Functional complementation studies in Saccharomyces cerevisiae showed that mutation MSR1-R531H (equivalent to human p.R469H) abolished respiration whereas the MSR1-R306Q strain (corresponding to p.R245Q) displayed a reduced growth on non-fermentable YPG medium. Although mutations functionally disrupted yeast we found a relatively well preserved arginine aminoacylation of mitochondrial tRNA. Clinical and neuroimaging findings are important clues to raise suspicion and to reach diagnostic accuracy for RARS2 mutations considering that biochemical abnormalities may be absent in muscle biopsy.

EPI-743 reverses the progression of the pediatric mitochondrial disease--genetically defined Leigh Syndrome

BACKGROUND

Genetically defined Leigh syndrome is a rare, fatal inherited neurodegenerative disorder that predominantly affects children. No treatment is available. EPI-743 is a novel small molecule developed for the treatment of Leigh syndrome and other inherited mitochondrial diseases. In compassionate use cases and in an FDA Expanded Access protocol, children with Leigh syndrome treated with EPI-743 demonstrated objective signs of neurologic and neuromuscular improvement. To confirm these initial findings, a phase 2A open label trial of EPI-743 for children with genetically-confirmed Leigh syndrome was conducted and herein we report the results.

METHODS

A single arm clinical trial was performed in children with genetically defined Leigh syndrome. Subjects were treated for 6 months with EPI-743 three times daily and all were eligible for a treatment extension phase. The primary objective of the trial was to arrest disease progression as assessed by neuromuscular and quality of life metrics. Results were compared to the reported natural history of the disease.

RESULTS

Ten consecutive children, ages 1-13 years, were enrolled; they possessed seven different genetic defects. All children exhibited reversal of disease progression regardless of genetic determinant or disease severity. The primary endpoints--Newcastle Pediatric Mitochondrial Disease Scale, the Gross Motor Function Measure, and PedsQL Neuromuscular Module--demonstrated statistically significant improvement (p<0.05). In addition, all children had an improvement of one class on the Movement Disorder-Childhood Rating Scale. No significant drug-related adverse events were recorded.

CONCLUSIONS

In comparison to the natural history of Leigh syndrome, EPI-743 improves clinical outcomes in children with genetically confirmed Leigh syndrome.

Pediatric reference intervals for muscle coenzyme Q(10)

Coenzyme Q(10) (CoQ(10)) is present in humans in both the reduced (ubiquinol, CoQ(10)H(2)) and oxidized (ubiquinone, CoQ(10)) forms. CoQ(10) is an essential cofactor in mitochondrial oxidative phosphorylation, and is necessary for ATP production. Total, reduced and oxidized CoQ(10) levels in skeletal muscle of 148 children were determined by HPLC coupled with electrochemical detection, and we established three level thresholds for total CoQ(10) in muscle. We defined as "severe deficiency", CoQ(10) levels falling in the range between 0.82 and 4.88 μmol/g tissue; as "intermediate deficiency", those ranging between 5.40 and 9.80 μmol/g tissue, and as "mild deficiency", the amount of CoQ(10) included between 10.21 and 19.10 μmol/g tissue. Early identification of CoQ(10) deficiency has important implications in children, not only for those with primary CoQ(10) defect, but also for patients with neurodegenerative disorders, in order to encourage earlier supplementation with this agent also in mild and intermediate deficiency.

Protein glutathionylation in cellular compartments: a constitutive redox signal

Glutathione provides means of regulating protein function by the process of glutathionylation. Despite the role of oxidative stress biomarkers assumed recently by glutathionylated proteins in human diseases, so far no information is available on the intracellular distribution of glutathionylated proteins in human cell lines. In this study, we combined the specificity of monoclonal antibody labeling for protein-bound glutathione (GS-Pro) with the ability of confocal microscopy to localize molecules with high spatial resolution. We performed immunofluorescence analysis on dermal fibroblasts, both in steady state than in proliferative conditions, and on in situ extracted matrix samples. For the first time, we report the compartmentalization of constitutively glutathionylated proteins in different subcellular districts and we found a tight association between glutathione, nuclear lamina, and cytoskeleton. In proliferating cells, total GS-Pro fluorescence increases in the early phases of growth and significantly drops when cells reach confluence. Interestingly, a nuclear shift of GS-Pro was observed between 6 and 48 hours after plating, becoming homogeneous with the cytoplasm when growth slows. The ability to visualize a detailed intracellular distribution of this critical marker of protein oxidation may provide an additional tool to highlight pathways in turns 'redox-activated' and to identify new pathogenic pathways in human diseases.

Neuroprotection: the emerging concept of restorative neural stem cell biology for the treatment of neurodegenerative diseases

During the past decades Neural Stem Cells have been considered as an alternative source of cells to replace lost neurons and NSC transplantation has been indicated as a promising treatment for neurodegenerative disorders. Nevertheless, the current understanding of NSC biology suggests that, far from being mere spare parts for cell replacement therapies, NSCs could play a key role in the pharmacology of neuroprotection and become protagonists of innovative treatments for neurodegenerative diseases. Here, we review this new emerging concept of NSC biology.

The use of muscle biopsy in the diagnosis of undefined ataxia with cerebellar atrophy in children

Childhood cerebellar ataxias, and particularly congenital ataxias, are heterogeneous disorders and several remain undefined. We performed a muscle biopsy in patients with congenital ataxia and children with later onset undefined ataxia having neuroimaging evidence of cerebellar atrophy. Significant reduced levels of Coenzyme Q10 (COQ10) were found in the skeletal muscle of 9 out of 34 patients that were consecutively screened. A mutation in the ADCK3/Coq8 gene (R347X) was identified in a female patient with ataxia, seizures and markedly reduced COQ10 levels. In a 2.5-years-old male patient with non syndromic congenital ataxia and autophagic vacuoles in the muscle biopsy we identified a homozygous nonsense mutation R111X mutation in SIL1 gene, leading to early diagnosis of Marinesco-Sjogren syndrome. We think that muscle biopsy is a valuable procedure to improve diagnostic assesement in children with congenital ataxia or other undefined forms of later onset childhood ataxia associated to cerebellar atrophy at MRI.

Intermittent-relapsing pyruvate dehydrogenase complex deficiency: a case with clinical, biochemical, and neuroradiological reversibility

Pyruvate dehydrogenase complex (PDHC) deficiency causes encephalomyopathies, of which there are four major categories: (1) neonatal encephalopathy with lactic acidosis; (2) an early infantile form, which (3) at times resembles Leigh syndrome; and (4) a later-onset form. Long-term clinical and radiological follow-up is still incompletely elucidated. We report a 12-year-old male with intermittent-relapsing PDHC deficiency who presented with three typical acute episodes of metabolic decompensation over 7 years. Neuroimaging showed reversible signal abnormalities in the basal ganglia, inferior olivary nuclei, periaqueductal grey matter, and dentate nuclei, with evidence of lactate on magnetic resonance spectroscopy. Molecular analysis of PDH1A revealed a novel hemizygous c.1045G>A mutation, predicting a p.A349T missense mutation. He was treated with thiamine supplementation and, while on this regimen, he experienced several intercurrent febrile episodes without neurological compromise. This case report stresses the importance of performing neuroimaging during acute clinical episodes because brain lesions in PDHC deficiency may be transient and reversible, and false-negative results may mislead the diagnosis and delay the treatment.

All glutathione forms are depleted in blood of obese and type 1 diabetic children

BACKGROUND

Oxidative stress plays an important role in the pathogenesis of type 1 diabetes (T1D), where an increase in reactive oxygen species may contribute to the initial destruction of β-cells. Accumulating evidence also suggests a role for oxidative stress in obesity, where it may potentiate the development of complications.

OBJECTIVE

To analyze the in vivo homeostasis of glutathione in children with T1D at onset and in children who are obese, to evaluate the systemic content of all glutathione forms (total, reduced, oxidized, and protein-bound glutathione) and the balance among them. Moreover, since glutathione bound to hemoglobin is a clinical marker of oxidative stress in human blood, we analyzed glutathionyl-hemoglobin in T1D and in obese children.

SUBJECTS

Children with T1D at onset (n = 30) or obesity (n = 30) at the first observation, and 30 healthy subjects chosen from the children who attended the outpatient clinic for minor problems.

METHODS

We assessed circulating levels of various glutathione forms by performing reverse-phase high performance liquid chromatography. Glutathionyl-hemoglobin analysis was carried out by cation-exchange chromatography.

RESULTS

In children with T1D and in obese children, we found a significant decrease of all glutathione forms including, for the first time, the content of total glutathione and glutathionylated proteins. The comparison among forms shows no significant imbalance in T1D patients, whereas in obese children it seems to suggest an attempt to rebalance the glutathione system homeostasis.

CONCLUSIONS

Our findings consistently show in vivo evidence of glutathione depletion upon early onset of T1D and in obese children, thus evidencing glutathione as an early marker in these two metabolic conditions.

S-Glutathionylation signaling in cell biology: progress and prospects

S-Glutathionylation is a mechanism of signal transduction by which cells respond effectively and reversibly to redox inputs. The glutathionylation regulates most cellular pathways. It is involved in oxidative cellular response to insult by modulating the transcription factor Nrf2 and inducing the expression of antioxidant genes (ARE); it contributes to cell survival through nuclear translocation of NFkB and activation of survival genes, and to cell death by modulating the activity of caspase 3. It is involved in mitotic spindle formation during cell division by binding cytoskeletal proteins thus contributing to cell proliferation and differentiation. Glutathionylation also interfaces with the mechanism of phosphorylation by modulating several kinases (PKA, CK) and phosphatases (PP2A, PTEN), thus allowing a cross talk between the two processes of signal transduction. Also, skeletal RyR1 channels responsible of muscle excitation-contraction coupling appear to be sensitive to glutathionylation. Members of the ryanodine receptor super family, responsible for Ca(2) release from endoplasmic reticulum stores, contain sulfhydryl groups that function as a redox "switch", which either induces or inhibits Ca(2) release. Finally, but very importantly, glutathionylation of proteins may also act on cell metabolism by modulating enzymes involved in glycosylation, in the Krebs cycle and in mitochondrial oxidative phosphorylation. In this review, we propose a greater role for glutathionylation in cell biology: not only a cellular response to oxidative stress, but an elegant and sensitive mechanism able to respond even to subtle changes in redox balance in the different cellular compartments. Given the wide spectrum of redox-sensitive proteins, we discuss the possibility that different pathways light up by glutathionylation under various pathological conditions. The feature of reversibility of this process also makes it prone to develop targeted drug therapies and monitor the pharmacological effectiveness once identified the sensor proteins involved.

Emodin prevents intrahepatic fat accumulation, inflammation and redox status imbalance during diet-induced hepatosteatosis in rats

High-fat and/or high-carbohydrate diets may predispose to several metabolic disturbances including liver fatty infiltration (hepatosteatosis) or be associated with necro-inflammation and fibrosis (steatohepatitis). Several studies have emphasized the hepatoprotective effect of some natural agents. In this study, we investigated the potential therapeutic effects of the treatment with emodin, an anthraquinone derivative with anti-oxidant and anti-cancer abilities, in rats developing diet-induced hepatosteatosis and steatohepatitis. Sprague-Dawley rats were fed a standard diet (SD) for 15 weeks, or a high-fat/high-fructose diet (HFD/HF). After 5 weeks, emodin was added to the drinking water of some of the SD and HFD/HF rats. The experiment ended after an additional 10 weeks. Emodin-treated HFD/HF rats were protected from hepatosteatosis and metabolic derangements usually observed in HFD/HF animals. Furthermore, emodin exerted anti-inflammatory activity by inhibiting the HFD/HF-induced increase of tumor necrosis factor (TNF)-α. Emodin also affected the hepatocytes glutathione homeostasis and levels of the HFD/HF-induced increase of glutathionylated/phosphorylated phosphatase and tensin homolog (PTEN). In conclusion, we demonstrated that a natural agent such as emodin can prevent hepatosteatosis, preserving liver from pro-inflammatory and pro-oxidant damage caused by HFD/HF diet. These findings are promising, proposing emodin as a possible hindrance to progression of hepatosteatosis into steatohepatitis.

Novel large-range mitochondrial DNA deletions and fatal multisystemic disorder with prominent hepatopathy

Hepatic involvement in mitochondrial cytopathies rarely manifests in adulthood, but is a common feature in children. Multiple OXPHOS enzyme defects in children with liver involvement are often associated with dramatically reduced amounts of mtDNA. We investigated two novel large scale deletions in two infants with a multisystem disorder and prominent hepatopathy. Amount of mtDNA deletions and protein content were measured in different post-mortem tissues. The highest levels of deleted mtDNA were in liver, kidney, pancreas of both patients. Moreover, mtDNA deletions were detected in cultured skin fibroblasts in both patients and in blood of one during life. Biochemical analysis showed impairment of mainly complex I enzyme activity. Patients manifesting multisystem disorders in childhood may harbour rare mtDNA deletions in multiple tissues. For these patients, less invasive blood specimens or cultured fibroblasts can be used for molecular diagnosis. Our data further expand the array of deletions in the mitochondrial genomes in association with liver failure. Thus analysis of mtDNA should be considered in the diagnosis of childhood-onset hepatopathies.

Oxidative stress parameters in paediatric non-alcoholic fatty liver disease

We have investigated the presence and the possible clinical implications of oxidative stress in children with non-alcoholic fatty liver disease (NAFLD). The present study was an observational study of oxidative stress parameters in the progression of paediatric NAFLD. We observed the role of oxidative stress in children diagnosed with NAFLD by evaluating: serum protein carbonyls, hepatic expression of 8-hydroxy-2-deoxyguanosine (8-OHG), and circulating antibody against malondialdehyde adducted human serum albumin (MDA-HSA). Forty consecutive children with biopsy-proven NAFLD (27 male; 13 female) referred to Bambino Gesù Children's Hospital, Rome, Italy, from January 2007 to April 2008 were included in the study. Serum variations of protein carbonyls, 8-OHG, and circulating antibody against MDA-HSA were evaluated. Elevated protein carbonyls were evident in 33 subjects (83%) irrespective of obesity and insulin resistance. Moreover, liver biopsies of NAFLD patients positive for circulating protein carbonyls also showed a significant increase in the nuclear staining for 8-OHG (p=0.006; 95% CI 3.1-17.7). Anti-MDA-HSA IgG above control threshold was detected in 25 (63%) children. Although protein carbonyl levels were unrelated with disease severity, patients with elevated anti-MDA-HSA IgG had scores for lobular inflammation significantly higher (p=0.019) than subjects with antibodies within the control range, while steatosis, hepatocyte ballooning and fibrosis were similar. High anti-MDA-HSA reactivity was also associated with a 13-fold increased risk (OR=12.9; 95= CI 1.5-113.8; p=0.013) of a NAFLD activity score (NAS) >or=5. These results demonstrate that oxidative stress has an high prevalence in children with NAFLD and is associated with an increased severity of steatohepatitis.

Mirnome analysis reveals novel molecular determinants in the pathogenesis of diet-induced nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is an emerging disease with a broad spectrum of liver conditions. The complex molecular pathogenesis of NAFLD is still unclear. In this study, we conducted an analysis of microRNA (miRNA) expression profiles in liver of rats made NAFLD by different diets. To this aim, Sprague-Dawley rats were fed ad libitum for 3 months with different diets: standard diet (SD), diet enriched in fats and low in carbohydrates (HFD), SD with high fructose (SD-HF) and diet with high levels of fats and fructose (HFD-HF). Our results demonstrated that the treatment with different dietetic regimens caused a significant increase of the body weight and the alteration of some metabolic parameters compared with control animals, as well as various liver injuries. The miRNAs analysis showed the significant downregulation of three miRNAs (miR-122, miR-451 and miR-27) and the upregulation of miR-200a, miR-200b and miR-429 in HFD, SD-HF and HFD-HF rats. Besides, miR-21 expression was significantly decreased only in fructose-enriched diets. These miRNAs target molecules involved in the control of lipid and carbohydrate metabolism, signal transduction, cytokine and chemokine-mediated signaling pathway and apoptosis. Western blot analysis of PKCδ, LITAF, ALDOLASE-A, p38MAPK, PTEN, LIPIN1, EPHRIN-A1, EPHA2 and FLT1 showed a diet-induced deregulation of all these proteins. Interestingly, the expression pattern of LITAF, PTEN, LIPIN1, EPHRIN-A1, EPHA2 and FLT1 might be well explained by the trend of their specific mRNAs, by potentially regulatory miRNAs, or both. In conclusion, we highlight for the first time the potential involvement of novel determinants (miRNAs and proteins) in the molecular pathogenesis of diet-induced NAFLD.

GSSG-mediated Complex I defect in isolated cardiac mitochondria

The mitochondrial respiratory chain represents the major source of reactive oxygen species (ROS) in cells and its dysfunction may contribute to the pathogenesis of several diseases. In mitochondria, glutathione is the major redox buffer and is a good indicator for the redox environment of the cell. Indeed, overproduction of ROS decreases the ratio between reduced and oxidized glutathione leading the latter to bind to proteins by a mechanism called glutathionylation. In this study, we demonstrate that in isolated cardiac mitochondria the respiratory chain enzyme Complex I is highly susceptible to glutathionylation under conditions of oxidative stress, showing a significant dose- and time-dependent decrease of the activity after treatment with oxidized glutathione. Among respiratory chain enzymes, Complex I appears the most affected by the oxidant-mediated inactivation in isolated mitochondria. Also, in cultured cardiomyocytes CI activity was strongly inhibited after in vivo treatment with hydrogen peroxide. Noteworthy, HPLC analysis showed a significant increase of protein glutathionylation in oxidatively stressed cells and this rise is in vivo reverted after incubation of cells with anti-oxidant N-acetyl-cysteine. These findings take particular importance given that CI represents the entry point of electrons into oxidative phosphorylation and that the threshold at which CI dysfunction affects ATP production is lower than that of any other OXPHOS complexes, making the enzyme particularly critical for the health of cells.

Susceptibility of isolated myofibrils to in vitro glutathionylation: Potential relevance to muscle functions

In this study we investigated the molecular mechanism of glutathionylation on isolated human cardiac myofibrils using several pro-glutathionylating agents. Total glutathionylated proteins appeared significantly enhanced with all the pro-oxidants used. The increase was completely reversed by the addition of a reducing agent, demonstrating that glutathione binding occurs by a disulfide and that the process is reversible. A sensitive target of glutathionylation was alpha-actin, showing a different reactivity to the several pro-glutathionylating agents by ELISA. Noteworthy, myosin although highly sensitive to the in vitro glutathionylation does not represent the primary glutathionylation target in isolated myofibrils. Light scattering measurements of the glutathionylated alpha-actin showed a slower polymerisation compared to the non-glutathionylated protein and force development was depressed after glutathionylation, when the myofibrils were mounted in a force recording apparatus. Interestingly, confocal laser scanning microscopy of cardiac cryosections indicated, for the first time, the constitutive glutathionylation of alpha-cardiac actin in human heart. Due to the critical location of alpha-actin in the contractile machinery and to its susceptibility to the oxidative modifications, glutathionylation may represent a mechanism for modulating sarcomere assembly and muscle functionality under patho-physiological conditions in vivo.

Friedreich's ataxia: oxidative stress and cytoskeletal abnormalities

Friedreich's ataxia (FRDA) is an autosomal recessive disorder caused by mutations in the gene encoding frataxin, a mitochondrial protein implicated in iron metabolism. Current evidence suggests that loss of frataxin causes iron overload in tissues, and increase in free-radical production leading to oxidation and inactivation of mitochondrial respiratory chain enzymes, particularly Complexes I, II, III and aconitase. Glutathione plays an important role in the detoxification of ROS in the Central Nervous System (CNS), where it also provides regulation of protein function by glutathionylation. The cytoskeletal proteins are particularly susceptible to oxidation and appear constitutively glutathionylated in the human CNS. Previously, we showed loss of cytoskeletal organization in fibroblasts of patients with FRDA found to be associated with increased levels of glutathione bound to cytoskeletal proteins. In this study, we analysed the glutathionylation of proteins in the spinal cord of patients with FRDA and the distribution of tubulin and neurofilaments in the same area. We found, for the first time, a significant rise of the dynamic pool of tubulin as well as abnormal distribution of the phosphorylated forms of human neurofilaments in FRDA motor neurons. In the same cells, the cytoskeletal abnormalities co-localized with an increase in protein glutathionylation and the mitochondrial proteins were normally expressed by immunocytochemistry. Our results suggest that in FRDA oxidative stress causes abnormally increased protein glutathionylation leading to prominent abnormalities of the neuronal cytoskeleton.

Glutathionylation of p65NF-kappaB correlates with proliferating/apoptotic hepatoma cells exposed to pro- and anti-oxidants

Oxidative stress influences a variety of regulatory proteins, including nuclear factor-kappaB (NF-kappaB). NF-kappaB is critical for maintaining the proliferation/apoptosis balance in hepatocytes. In this study we investigated the causal links between glutathione, NF-kappaB and hepatocyte damage. HepG2 and 3B cells were exposed to different doses of H2O2 or N-acetylcysteine (NAC) and the proliferation/apoptosis rate, glutathione forms, and p65NF-kappaB glutathionylation and activity were analysed. Our results demonstrate that H2O2 stopped proliferative response at low doses, but induced apoptosis only at high doses. In contrast, NAC exerted, proportionally to its concentration, a dual role simultaneously increasing both proliferation and apoptosis. Interestingly, the levels of protein-bound glutathione were increased by H2O2 and decreased by NAC. Moreover, the antibody recognizing the glutathionylated proteins co-precipitated and -localized with the cytoplasmic inactive form of p65NF-kappaB in H2O2- and NAC-treated cells, even when, in 1 mM NAC-treated cells, a part of p65 was glutathione-free and localized into the nucleus. Apoptotic cells were characterised principally by a cytoskeletal staining of glutathionylation and retention of NF-kappaB in the cytoplasmic region; whereas in proliferating cells, glutathionylated proteins were concentrated into the perinuclear region and p65NF-kappaB was traslocated into the nucleus. While cytoplasmic NF-kappaB retention correlated well with an increased apoptotic rate, a greater expression of this protein was observed in association with the NAC-dependent. In conclusion, our findings suggest that glutathionylation inhibits NF-kappaB activity causing reduced hepatocyte survival, which is common in several liver diseases.

Variant late infantile neuronal ceroid lipofuscinosis because of CLN1 mutations

The neuronal ceroid lipofuscinoses are a heterogeneous group of inherited degenerative disorders of the central nervous system. Cases of ceroid lipofuscinosis with cytoplasmic storage of granular osmiophilic deposits are associated with reduced activity of palmitoyl-protein thioesterase-1 (PPT-1) and mutations in CLN1, and occur from infancy to adulthood. We present clinical and diagnostic investigations in six children with variant late infantile neuronal ceroid lipofuscinosis and mutations in CLN1. The main clinical features at onset were behavioral disturbances and cognitive decline. Myoclonic jerks constituted the most prominent paroxysmal phenomenon. An electroencephalogram revealed the "vanishing" pattern described in infantile ceroid lipofuscinosis. Neurologic regression was associated with dramatic shrinkage of cortical structures, evident upon brain magnetic resonance imaging. Three unrelated children harboring the same homozygous mutation in CLN1 and a girl who carried a novel mutation resulting in skipping of multiple exons presented with a similar clinical phenotype. The most severe picture occurred in two siblings who carried a homozygous mutation predicting a prematurely truncated protein. Similar to the infantile form, the clinical evolution in this group of patients was characterized by an onset of severe neurologic impairment, peaking within a relatively short period of time, followed by a slower evolution of the disease.

Assaying ATP synthesis in cultured cells: a valuable tool for the diagnosis of patients with mitochondrial disorders

Mitochondrial ATP synthase plays a central role in cell function by synthesising most of the ATP in human tissues. In different cells, active regulation of mitochondrial ATP synthase in response to cellular energy demand has been demonstrated, as well as its alteration under several pathological conditions affecting oxidative phosphorylation (OXPHOS). Traditionally, detection of OXPHOS defects is based on the spectrophotometric measurement of respiratory chain complex activities in muscle biopsies. Considering the broad clinical spectrum of mitochondrial disorders, and the difficulty in arriving at a single diagnostic method, in this study we propose measurement of ATP synthesis in mitochondria from skin fibroblasts as an effective screening tool. In the light of our results this assessment emerges as a useful marker of impaired energy production in primary OXPHOS disorders of childhood and as a tool with the potential to drive further molecular genetic studies.