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Cathepsin D-deficient Drosophila recapitulate the key features of neuronal ceroid lipofuscinoses.

Neuronal ceroid lipofuscinoses (NCLs) are a group of lysosomal storage disorders characterized pathologically by neuronal accumulation of autofluorescent storage material and neurodegeneration. An ovine NCL form is caused by a recessive point mutation in the cathepsin D gene, which encodes a lysosomal aspartyl protease. This mutation results in typical NCL pathology with neurodegeneration and characteristic neuronal storage material. We have generated a Drosophila NCL model by inactivating the conserved Drosophila cathepsin D homolog. We report here that cathepsin D mutant flies exhibit the key features of NCLs. They show progressive neuronal accumulation of autofluorescent storage inclusions, which are also positive for periodic acid Schiff and luxol fast blue stains. Ultrastructurally, the storage material is composed of membrane-bound granular electron-dense material, similar to the granular osmiophilic deposits found in the human infantile and ovine congenital NCL forms. In addition, cathepsin D mutant flies show modest age-dependent neurodegeneration. Our results suggest that the metabolic pathway leading to NCL pathology is highly conserved during evolution, and that cathepsin D mutant flies can be used to study the pathogenesis of NCLs.

Amino Acid Sequence↗

The intracellular location and function of proteins of neuronal ceroid lipofuscinoses.

Neuronal ceroid lipofuscinoses are a group of diseases characterized by accumulation of hydrophobic proteins in lysosomes of neurons and other types of cells. NCLs are caused by at least 8 mutant genes (CLN1-CLN8), though CLN4 and CLN7 have not yet been identified. Except for Cln1p, the protein encoded by CLN1, the defective proteins are associated with lysosomal accumulation of mitochondrial ATP synthase subunit c. Cln1p and Cln2p are soluble lysosomal enzymes, targeted to lysosomes in a mannose 6-phosphate dependent manner. Mutations in the lysosomal protease cathepsin D cause another NCL. Cln3p, Cln5p, Cln6p and Cln8p are thought to be transmembrane proteins. Cln3p and Cln5p are localized in the endosome-lysosomal compartment. Deficiency of endosomal membrane protein CLC-3, a member of the chloride channel family, causes NCL-like phenotype and lysosomal storage of subunit c. Herein, we review the features of NCL and NCL-related proteins and discuss the involvement of the proteins in lysosomal degradation of subunit c.

Animals↗

[Neuronal ceroid lipofuscinoses].

BACKGROUND: Neuronal ceroid lipofuscinoses (NCL) is a group of degenerative neurological diseases. The diseases are autosomally recessively inherited and are characterized by the accumulation of fluorescent ceroid and lipofuscin in neuronal cells in the brain and in extraneuronal cells. The aim of this review was to assess and to summarize research related to diagnostics and treatment of NCL. MATERIAL AND METHODS: The article is built on own experience and systematic searches on PubMed, Medline, PsychInfo and the Internet. RESULTS AND INTERPRETATION: Three main types of NCL with childhood onset are recognised; an infantile, a late infantile, and a juvenile type. One NCL type starts in adulthood. In Norway the juvenile type is diagnosed most frequently. The diseases are rare. The incidence rates in different countries range from 0.5 to 8.0 per 100,000 live births. The main features include impaired vision, failure of psychomotor development, seizures and premature death. Prior to availability of genetic testing, the clinical status, ophthalmologic examination, examination of blood cells for deposited material (vacuolised lymphocytes) and neurophysiological examinations were the most important methods of confirming the diagnosis. Recent genetic findings have established that defects in at least six different genes underlie the various forms of NCL. There is no curative treatment. Scientists are trying to develop treatment using enzyme replacement, gene therapy, stem cell transplantation and pharmacotherapy. Symptomatic and palliative treatment is therefore essential.

Adult↗

The molecular genetic basis of the neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders characterized by the presence of autofluorescent lipopigment in neurons and other cell types. The childhood onset types display autosomal recessive inheritance. Naturally occurring animal NCLs have been described in many species including mouse, sheep and dog. In the last decade major advances have occurred in the molecular genetic analysis of the NCLs. Six disease gene loci have been mapped, and five disease genes have been isolated. Two of these encode lysosomal enzymes: CLN1 encodes palmitoyl-protein thioesterase (PPT), and CLN2 encodes tripeptidyl peptidase 1 (TPP1). The remaining three, CLN3, CLN5 and CLN8 encode putative membrane proteins of unknown function. The murine orthologue of CLN8 causes motor neuron degeneration (mnd), a mouse model of NCL. These advances have revolutionized diagnosis and classification, but a unified theory of pathogenesis and effective treatment remain elusive.

Aminopeptidases↗

Genetics of the neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses (NCLs) are an intriguing group of inherited neurodegenerative disorders characterized by blindness, progressive psychomotor deterioration and death of neocortical neurons. Clinically, four major NCL groups have been identified: infantile, late infantile, juvenile and adult. In recent years, our understanding of the molecular basis of different NCLs has advanced significantly. The accumulation of autofluorescent material in patients' tissues has been shown to be caused by defects in either lysosomal enzymes or in novel membrane proteins of unknown function. Although the accumulated material is biochemically well defined and some of the causative mutations are known, a unifying hypothesis for the molecular basis of the NCLs remains elusive. Further work will be required to characterize the interactiving molecules and metabolic pathways involved in the pathogenesis of NCLs.

Adolescent↗

Molecular genetics of the neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders characterised by the accumulation of autofluorescent storage material in neurons and other cell types. The clinical features include visual impairment, progressive myoclonic epilepsy, and cognitive decline reflecting progressive neurodegeneration. The NCLs are subdivided into several subtypes according to age of onset, clinical course, and ultrastructure of the storage material. The molecular genetic basis of this group of disorders has recently been clarified. Mutations in the gene encoding a lysosomal enzyme, palmitoyl protein thioesterase (PPT), cause infantile NCL (locus CLN1 on chromosome 1p32) or Haltia-Santavuori disease. This Finnish disease is characterised ultrastructurally by granular osmiophilic deposits (GRODs). Juvenile-onset NCL with GRODs also is caused by mutations in PPT. Classic late-infantile NCL (Jansky-Bielschowsky disease) is caused by mutations in a gene encoding a pepstatin-insensitive lysosomal peptidase (CLN2 on chromosome 11p15), and juvenile-onset NCL (Batten disease) is caused by mutations in a gene encoding a 438-amino-acid membrane protein (CLN3 on chromosome 16p12) of unknown function. A locus for Finnish variant late-infantile NCL, CLN5, has been mapped to chromosome 13q22 and a locus for variant late-infantile NCL, CLN6, to chromosome 15q21-23. These and further advances will allow the molecular basis of the NCLs to be elucidated and may lead to new strategies for diagnosis and treatment.

Adolescent↗

An Australasian diagnostic service for the neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses (NCLs) are a family of related genetic disorders that together are believed to affect one child in every 12,500 births in the USA. Our laboratory has developed a diagnostic service for classical late infantile neuronal ceroid lipofuscinosis (LINCL) by assay of tripeptidyl-peptidase I (TPP-I) activity using the fluorogenic peptide substrate Ala-Ala-Phe aminomethylcoumarin, followed by a screen for three mutations in the CLN2 gene. In addition, we have also begun to offer a limited diagnostic service for the juvenile (JNCL) and infantile (INCL) forms of the disease on the basis of mutation analysis of the CLN3 and CLN1 genes, respectively. Retrospective analysis of Australasian patients with a clinical suspicion of NCL has revealed that six are affected by LINCL, six by JNCL and, to date, two by INCL. Mutation analysis of our LINCL patients has shown that the three screened mutations, namely, the nonsense mutation R208X and the splice mutations IVS5-1 G > C and IVS5-1 G > A, constitute 83% of alleles.

Aminopeptidases↗

Biochemical aspects of neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses (NCLs) collectively constitute the most common group of progressive brain diseases in children. The childhood forms of NCL are recessively inherited monogenic diseases, resulting in progressive dementia and motor problems, epilepsy, blindness and, finally, early death. Pathologically, the NCLs are characterized by accumulation of autofluorescent storage material in the lysosomes of neurons and other cells. The disease is selectively manifested in the central nervous system, so that there is a progressive loss of neurons. This leads to a dramatic cerebral atrophy typical of the early onset forms of NCL. The present review summarizes the knowledge of the biochemistry of NCLs, and discusses the possible pathogenetic mechanisms involved in the neurodegeneration in NCLs.

Aminopeptidases↗

The dystrophic retina in multisystem disorders: the electroretinogram in neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses (NCL) are neurodegenerative disorders with psychomotor deterioration, seizures, visual failure and premature death, all associated with abnormal storage of lipoproteins within lysosomes. The most common forms of NCL are an infantile form (INCL, CLN1), a late infantile form (LINCL, CLN2) and a juvenile onset form (JNCL, CLN3). The electroretinogram (ERG) is abnormal early in all three of these forms and eventually is totally ablated. The purpose of this report is to describe the ERG in INCL, LINCL and JNCL. The ERGs of 7 patients who were examined by the author over the past 15 years were reviewed. Ganzfeld ERG responses were recorded using the ISCEV standard protocol and an intensity response series over a 3.7 log unit range. The earliest ERG manifestation of INCL is a marked loss of the scotopic and photopic b-wave with relative preservation of the a-wave; this defect, which was evident for both rods and cones, suggests preservation of photoreceptor outer segment function with severe disturbance of transmission of the signal to the second-order neuron, the bipolar cells. For LINCL, the rod responses were mildly abnormal but more preserved than in INCL or JNCL. The cone b-wave amplitudes in patients with early LINCL were severely subnormal with prolonged implicit times. Patients with JNCL invariably showed severe to profound ERG abnormalities when first tested, with essentially no rod-mediated activity and marked loss of a-wave amplitudes with even greater loss of b-wave amplitudes, creating electronegative configuration waveforms. Differences in the ERG responses were thus found that provide further clues to the earliest site of pathology within the retina.

Biopsy↗

The neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses are clinical disorders associated with the accumulation of autofluorescent waxy pigments within cells of several different tissues. Such syndromes always have neurological manifestations. Variations in clinical course, genetics, pathogenesis, and possibly treatment occur in each of the several forms listed under this category. Ten subtypes have now been recognized: (1) chronic, juvenile (Batten type); (2) acute, late infantile (Bielschowsky type); (3) subacute-chronic, adult (Kufs type); (4) acute, infantile (Santavuori-Haltia type); (5) congenital (Norman-Wood type); (6) acute, adult (Zeman-Dyken type); (7) acute-subacute childhood (Bielschowsky variant); (8) chronic, childhood with pervasiveness (Edathodu-Dyken type); (9) chronic, infantile with autism (Dyken type); and (10) chronic, juvenile with ataxia and spasticity (Dyken type). By far the most common of these are the first four disorders listed. It is proposed that this present classification of neuronal ceroid lipofuscinosis is more comprehensive than previous ones and fails to support the hypothesis that this disorder represents a unitary disease process, rather than different diseases with similar characteristics. At present, each of the neuronal ceroid lipofuscinosis types are of unknown etiology.

Humans↗

Iron and oxygen radicals in tissue damage: implications for the neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses (NCL) are an important group of progressive encephalopathies characterized by accumulation of autofluorescent storage material, which probably arise during the destruction of cells by lipid peroxidation and the action of oxygen radicals such as superoxide (O.2-) and the hydroxyl radical (OH.). The rates of lipid peroxidation and of superoxide-dependent hydroxyl radical formation would be greatly accelerated by the presence of non-protein-bound iron salts. Cerebrospinal fluid from patients with different types of NCL has a higher level of non-protein-bound iron and lower antioxidant activity than that of controls. The raised iron content and decreased antioxidant protection found in cerebrospinal fluids may be symptomatic of a more general abnormality in iron metabolism and protection against its damaging effects.

Antioxidants↗

Correlations between genotype, ultrastructural morphology and clinical phenotype in the neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses (NCLs) are a group of severe neurodegenerative diseases with onset usually in childhood and characterised by the intracellular accumulation of autofluorescent storage material. Within the last decade, mutations that cause NCL have been found in six human genes (CLN1, CLN2, CLN3, CLN5, CLN6 and CLN8). Mutations in two additional genes cause disease in animal models that share features with NCL-CTSD in sheep and mice and PPT2 in mice. Approximately 160 NCL disease-causing mutations have now been described (listed and fully cited in the NCL Mutation Database, http://www.ucl.ac.uk/ncl/ ). Most mutations result in a classic morphology and disease phenotype, but some mutations are associated with disease that is of later onset, less severe or protracted in its course, or with atypical morphology. Seven common mutations exist, some having a worldwide distribution and others associated with families originating from specific geographical regions. This review attempts to correlate the gene, disease-causing mutation, morphology and clinical phenotype for each type of NCL.

Aminopeptidases↗

Pheno/genotypic correlations of neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses (NCL) are a large group of autosomal recessive lysosomal storage disorders with both enzymatic deficiency and structural protein dysfunction. Previously, diagnosis of NCL was based on age at onset and clinicopathologic (C-P) findings, classified as 1) infantile (INCL), 2) late infantile (LINCL), 3) juvenile (JNCL), and 4) adult (ANCL). Most patients with NCL have progressive ocular and cerebral dysfunction, including cognitive/motor dysfunction and uncontrolled seizures. After reviewing 319 patients with NCL, the authors found that 64 (20%) did not fit into this classification of NCL. With research progress, four additional forms have been recognized: 5) Finnish, 6) Gypsy/Indian, and 7) Turkish variants of LINCL and 8) northern epilepsy, also known as progressive epilepsy with mental retardation. These eight NCL forms resulted from 100 different mutations on genes CLN1to CLN8 causing different phenotypes (http://www.ucl.ac.uk/ncl). The genes CLN1 and CLN2 encode lysosomal palmitoyl protein thioesterase and tripeptidyl peptidase 1. The function of CLN3, CLN5, and CLN8 gene-encoded products is unknown, although their predicted amino acid sequences suggest they have a transmembrane topology. The diagnosis of NCL is based on C-P findings, enzymatic assay, and molecular genetic testing. Before biochemical and genetic tests are conducted, ultrastructural studies (i.e., blood [buffy coat] or punch biopsies [skin, conjunctiva]) must be performed to confirm the presence and nature of lysosomal storage material (fingerprint or curvilinear profiles or granular osmiophilic deposits). The recognition of variable onset from infancy to middle age supersedes the traditional emphasis on age-related NCL forms.

Age of Onset↗

Molecular diagnosis of and carrier screening for the neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses (NCLs) are a large group of autosomal recessive lysosomal storage disorders with both enzymatic deficiency and structural protein dysfunction. Three typical forms, the infantile (INCL), late-infantile (LINCL), and juvenile (JNCL), are among the most common childhood-onset neurodegenerative disorders. They result from mutations on genes CLN1, CLN2, and CLN3, respectively. We determined that the mutations 223A --> G and 451C --> T in CLN1, T523-1G --> C, and 636 C --> T in CLN2, and deletion of a 1.02-kb genomic fragment in CLN3 are the five common mutations for NCL. To offer clinical genetic testing for the NCLs, we have developed simple and quick PCR-based molecular tests for detecting INCL-, LINCL-, and JNCL-affected individuals from 180 NCL families (27 INCL, 76 LINCL, and 77 JNCL). The sensitivity of testing to detect NCL patients among clinically suspected individuals was determined to be 78% (21/27) for INCL, 66% (54/76) for LINCL, and 75% (58/77) for JNCL. When molecular screening for carriers was conducted among the normal siblings or parents of the probands, we identified two carriers out of three individuals tested for INCL, 20/56 (35.7%) carriers for LINCL, and 48/106 (45.3%) carriers for JNCL families. In addition, 5% (9/180) of NCL patients revealed genetic heterogeneity and were reclassified. Seven patients previously diagnosed as having JNCL were now found to carry mutations of CLN2 (5/7) or CLN1 (2/7) and 2 with late-infantile onsets were identified as carrying mutations of CLN1. Our data demonstrate the importance of DNA testing to detect accurately both affected individuals and carriers in NCL families.

Adolescent↗

Neuronal ceroid lipofuscinoses: a review.

Neuronal ceroid lipofuscinoses (NCLs) are among the most common neurodegenerative diseases in childhood but rarely present in adulthood. The main symptoms are psychomotor deterioration, visual failure, epilepsy and motor disturbances. The NCLs are morphologically characterized by the accumulation of lipopigments within numerous cell types and loss of neurons. Pathogenesis is unknown. The current clinical classification recognizes six classic types of NCL and several atypical forms. Electrophysiological and neuroradiological findings may be of diagnostic significance, but disease recognition rests on the demonstration of a typical ultrastructural pattern. Genetic studies have demonstrated that several different genetic loci are involved in the pathogenesis of NCL, but the molecular mechanisms underlying neuronal death and lipopigment accumulation are not understood.

Humans↗

Mechanisms of neurodegeneration in neuronal ceroid-lipofuscinoses.

Neuronal ceroid-lipofuscinoses (NCL) are a group of neurodegenerative diseases and autosomal recessive lysosomal storage disorders. We examined the involvement of cell death, oxidative stress, and glutamate excitotoxicity using immunohistochemistry against Bcl-2, Bcl-x, oxidative products to proteins, lipids and DNA, calcium-binding proteins (calbindin-D28K, parvalbumin, calretinin), and glial glutamate transporters (excitatory amino acid transporters 1 and 2), in addition to terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) in the brains from three cases of late infantile form of NCL (LINCL) and one case of juvenile form of NCL (JNCL) to investigate the neurodegenerative mechanisms. In the cerebral and cerebellar cortex, all of three LINCL cases demonstrated neurons with TUNEL-immunoreactive nuclei, whereas the JNCL case did not show TUNEL-immunoreactive nuclei. The coexistence of the nuclear TUNEL-immunoreactivity nuclei and cytoplasmic deposition of 4-hydroxy-2-nonenal-modified protein in the frontal cortex and hypoglossal nucleus may suggest a possible interrelationship between DNA fragmentation and lipid oxidation in LINCL. Additionally, glycoxidation of protein and oxidative stress to DNA seemed to be involved in the cerebellar and cerebral degeneration, respectively. Interneurons immunoreactive for calbindin-D28K and parvalbumin were severely reduced in the cerebral cortex, whereas those for calretinin were comparatively well preserved in LINCL, indicating the possibility of altered GABAergic system. The disturbance of expression of glial glutamate transporters seemed to be heterogeneous and mild. These findings suggest the possibility of new treatments for neurodegeneration in LINCL using antioxidative agents and/or GABAergic medications.

Adolescent↗

Reconsideration of the classification of the neuronal ceroid-lipofuscinoses.

Neuronal ceroid-lipofuscinoses (NCL) represent diseases of different types. Each variety of NCL may have its own clinical course, genetics, pathogenesis, and treatment. Four disorders are presently accepted as examples of NCL. These include the chronic juvenile or Batten type, the acute late infantile or Bielschowsky type, the chronic or subacute adult Kufs type, and the acute infantile or Santavuori-Haltia type. Seventy patients with clinical and pathological features of NCL have been studied over 20 years; 62 of these fit into one of the above categories, but 8 are atypical and present nosologic problems. Recognized as examples of atypical NCL are 1) chronic congenital or Norman-Wood type, 2) acute adult or Zeman-Dyken type, 3) acute childhood or Bielschowsky variant, 4) chronic childhood (Edathodu-Dyken) type, with pervasiveness, 5) chronic infantile (Dyken) type with autism, and 6) chronic juvenile (Dyken) type with ataxia. It is proposed that our present classification of NCL be based on differentiating clinical dynamics and characteristics, age-of-onset, and morphological and pathological criteria. Although genetic characteristics are now recognized, these are of autosomal recessive or autosomal dominant type. No differentiating biochemical differences have been established to aid in the nosology of these diseases.

Adult↗

Functional biology of the neuronal ceroid lipofuscinoses (NCL) proteins.

Neuronal ceroid lipofucinoses (NCLs) are a group of severe neurodegenerative disorders characterized by accumulation of autofluorescent ceroid lipopigment in patients' cells. The different forms of NCL share many similar pathological features but result from mutations in different genes. The genes affected in NCLs encode both soluble and transmembrane proteins and are localized to ER or to the endosomes/lysosomes. Due to selective vulnerability of the central nervous system in the NCL disorders, the corresponding proteins are proposed to have important, tissue specific roles in the brain. The pathological similarities of the different NCLs have led not only to the grouping of these disorders but also to suggestion that the NCL proteins function in the same biological pathway. Despite extensive research, including the development of several model organisms for NCLs and establishment of high-throughput techniques, the precise biological function of many of the NCL proteins has remained elusive. The aim of this review is to summarize the current knowledge of the functions, or proposed functions, of the different NCL proteins.

Aminopeptidases↗