Systemic administration of tripeptidyl peptidase I in a mouse model of late infantile neuronal ceroid lipofuscinosis: effect of glycan modification

Late-infantile neuronal ceroid lipofuscinosis (LINCL) is a recessive genetic disease of childhood caused by deficiencies in the lysosomal protease tripeptidyl peptidase I (TPP1). Disease is characterized by progressive and extensive neuronal death. One hurdle towards development of enzyme replacement therapy is delivery of TPP1 to the brain. In this study, we evaluated the effect of modifying N-linked glycans on recombinant human TPP1 on its pharmacokinetic properties after administration via tail vein injection to a mouse model of LINCL. Unmodified TPP1 exhibited a dose-dependent serum half-life of 12 min (0.12 mg) to 45 min (2 mg). Deglycosylation or modification using sodium metaperiodate oxidation and reduction with sodium borohydride increased the circulatory half-life but did not improve targeting to the brain compared to unmodified TPP1. Analysis of liver, brain, spleen, kidney and lung demonstrated that for all preparations, >95% of the recovered activity was in the liver. Interestingly, administration of a single 2 mg dose (80 mg/kg) of unmodified TPP1 resulted in ∼10% of wild-type activity in brain. This suggests that systemic administration of unmodified recombinant enzyme merits further exploration as a potential therapy for LINCL.

Mutational analysis of telomere genes in BRCA1/2-negative breast cancer families with very short telomeres

A majority of the familial breast cancer cases are not explained by mutations in the best-known high susceptibility genes BRCA1 and BRCA2. Since there is a link between DNA repair and telomere maintenance mechanisms, we have investigated for the first time the role of telomere genes in breast cancer predisposition. By a combination of DHPLC and direct sequencing, we screened for sequence variation in 14 telomere-related genes which included telomerase and shelterin complexes in index cases from 50 BRCA1/2-negative families previously characterized to have very short telomere length in peripheral blood leukocytes. Clear pathogenic changes were not detected in any of the genes analyzed. Most of the changes were non-coding variants and only nine corresponded to coding variants located in TPP1, TINF2, NHP2, TNKS, and RAD54B genes; although only two corresponded to coding missense changes leading to aminoacid changes in genes NHP2 and RAD54B. However, functional prediction analysis and control population studies of both variants ruled out its possible pathogenic role. Our results discard a major contribution of telomere-specific genes in hereditary breast cancer.

[Neuronal ceroid lipofuscinosis: diagnostic algorithm and clinical description of the Finnish (CLN5) and Turkish (CLN7) variants late infantile]

INTRODUCTION

The neuronal ceroid lipofuscinosis are classified based on age at onset into four main clinical forms in child-hood: infantile, late infantile, juvenile and congenital (CLN1, CLN2, CLN3 and CLN10). The variant late infantile forms (CLN5, CLN6, CLN7 and CLN8) are characterized by a wide variability of the clinical phenotypes and the most patients are originated from Finland and Turkey (Finnish, CLN5, and Turkish, CLN7 variants).

CASE REPORTS

We describe three unrelated patients with Finnish variant and another patient with Turkish variant. We describe an algorithm to facility the diagnosis of these low prevalence diseases. Patients with Finnish variant started with behaviour disorder between 2.6 and 4.6 years of age followed by learning difficulties and visual failure at an age of 6 years. Generalised tonic-clonic and myoclonic seizures were observed at 7 years of age with myoclonic jerks later on. Patients developed ataxia and blindness within 9 years and increasingly disability at 11 years of age. The patient with Turkish variant started with refractory epilepsy at age of 2, followed by a severe neurodegeneration manifested by ataxia, loss of walking ability within 2-3 years and vegetative state at 11 years of age.

CONCLUSIONS

The clinical spectrum of the variant late infantile forms shows a wide geographical distribution. We report three novel mutations in the CLN5 gene and a diagnostic algorithm to facility the correlation genotype-phenotype studies.

Intrathecal tripeptidyl-peptidase 1 reduces lysosomal storage in a canine model of late infantile neuronal ceroid lipofuscinosis

Late infantile neuronal ceroid lipofuscinosis (LINCL) is caused by mutations in the gene encoding tripeptidyl-peptidase 1 (TPP1). LINCL patients accumulate lysosomal storage materials in the CNS accompanied by neurodegeneration, blindness, and functional decline. Dachshunds homozygous for a null mutation in the TPP1 gene recapitulate many symptoms of the human disease. The objectives of this study were to determine whether intrathecal (IT) TPP1 treatment attenuates storage accumulation and functional decline in TPP1-/- Dachshunds and to characterize the CNS distribution of TPP1 activity. TPP1 was administered to one TPP1-/- and one homozygous wild-type (WT) dog. An additional TPP1-/- and WT dog received vehicle. Four IT administrations of 32 mg TPP1 formulated in 2.3 mL of artificial cerebrospinal fluid (aCSF) or vehicle were administered monthly via the cerebellomedullary cistern from four to seven months of age. Functional decline was assessed by physical and neurological examinations, electrophysiology, and T-maze performance. Neural tissues were collected 48 h after the fourth administration and analyzed for TPP1 activity and autofluorescent storage material. TPP1 was distributed at greater than WT levels in many areas of the CNS of the TPP1-/- dog administered TPP1. The amount of autofluorescent storage was decreased in this dog relative to the vehicle-treated affected control. No improvement in overall function was observed in this dog compared to the vehicle-treated TPP1-/- littermate control. These results demonstrate for the first time in a large animal model of LINCL widespread delivery of biochemically active TPP1 to the brain after IT administration along with a decrease in lysosomal storage material. Further studies with this model will be necessary to optimize the dosing route and regimen to attenuate functional decline.

Loss of Niemann-Pick C1 or C2 protein results in similar biochemical changes suggesting that these proteins function in a common lysosomal pathway

Niemann-Pick Type C (NPC) disease is a lysosomal storage disorder characterized by accumulation of unesterified cholesterol and other lipids in the endolysosomal system. NPC disease results from a defect in either of two distinct cholesterol-binding proteins: a transmembrane protein, NPC1, and a small soluble protein, NPC2. NPC1 and NPC2 are thought to function closely in the export of lysosomal cholesterol with both proteins binding cholesterol in vitro but they may have unrelated lysosomal roles. To investigate this possibility, we compared biochemical consequences of the loss of either protein. Analyses of lysosome-enriched subcellular fractions from brain and liver revealed similar decreases in buoyant densities of lysosomes from NPC1 or NPC2 deficient mice compared to controls. The subcellular distribution of both proteins was similar and paralleled a lysosomal marker. In liver, absence of either NPC1 or NPC2 resulted in similar alterations in the carbohydrate processing of the lysosomal protease, tripeptidyl peptidase I. These results highlight biochemical alterations in the lysosomal system of the NPC-mutant mice that appear secondary to lipid storage. In addition, the similarity in biochemical phenotypes resulting from either NPC1 or NPC2 deficiency supports models in which the function of these two proteins within lysosomes are linked closely.

Therapeutic approaches to the challenge of neuronal ceroid lipofuscinoses

The Neuronal Ceroid Lipofuscinoses (NCLs) are lysosomal storage diseases (LSDs) affecting the central nervous system (CNS), with generally recessive inheritance. They are characterized by pathological lipofuscin-like material accumulating in cells. The clinical phenotypes at all onset ages show progressive loss of vision, decreasing cognitive and motor skills, epileptic seizures and premature death, with dementia without visual loss prominent in the rarer adult forms. Eight causal genes, CLN10/CTSD, CLN1/PPT1, CLN2/TPP1, CLN3, CLN5, CLN6, CLN7/MFSD8, CLN8, with more than 265 mutations and 38 polymorphisms (http://www.ucl.ac.uk/ncl) have been described. Other NCL genes are hypothesized, including CLN4 and CLN9; CLCN6, CLCN7 and possibly SGSH are under study. Some therapeutic strategies applied to other LSDs with significant systemic involvement would not be effective in NCLs due to the necessity of passing the blood brain barrier to prevent the neurodegeneration, repair or restore the CNS functionality. There are therapies for the NCLs currently at preclinical stages and under phase 1 trials to establish safety in affected children. These approaches involve enzyme replacement, gene therapy, neural stem cell replacement, immune therapy and other pharmacological approaches. In the next decade, progress in the understanding of the natural history and the biochemical and molecular cascade of events relevant to the pathogenesis of these diseases in humans and animal models will be required to achieve significant therapeutic advances.

A critical tryptophan and Ca2+ in activation and catalysis of TPPI, the enzyme deficient in classic late-infantile neuronal ceroid lipofuscinosis

Background

Tripeptidyl aminopeptidase I (TPPI) is a crucial lysosomal enzyme that is deficient in the fatal neurodegenerative disorder called classic late-infantile neuronal ceroid lipofuscinosis (LINCL). It is involved in the catabolism of proteins in the lysosomes. Recent X-ray crystallographic studies have provided insights into the structural/functional aspects of TPPI catalysis, and indicated presence of an octahedrally coordinated Ca²⁺.

Methodology

Purified precursor and mature TPPI were used to study inhibition by NBS and EDTA using biochemical and immunological approaches. Site-directed mutagenesis with confocal imaging technique identified a critical W residue in TPPI activity, and the processing of precursor into mature enzyme.

Principal Findings

NBS is a potent inhibitor of the purified TPPI. In mammalian TPPI, W542 is critical for tripeptidyl peptidase activity as well as autocatalysis. Transfection studies have indicated that mutants of the TPPI that harbor residues other than W at position 542 have delayed processing, and are retained in the ER rather than transported to lysosomes. EDTA inhibits the autocatalytic processing of the precursor TPPI.

Conclusions/Significance

We propose that W542 and Ca²⁺ are critical for maintaining the proper tertiary structure of the precursor proprotein as well as the mature TPPI. Additionally, Ca²⁺ is necessary for the autocatalytic processing of the precursor protein into the mature TPPI. We have identified NBS as a potent TPPI inhibitor, which led in delineating a critical role for W542 residue. Studies with such compounds will prove valuable in identifying the critical residues in the TPPI catalysis and its structure-function analysis.

Novel interactions of CLN5 support molecular networking between Neuronal Ceroid Lipofuscinosis proteins

BACKGROUND

Neuronal ceroid lipofuscinoses (NCLs) comprise at least eight genetically characterized neurodegenerative disorders of childhood. Despite of genetic heterogeneity, the high similarity of clinical symptoms and pathology of different NCL disorders suggest cooperation between different NCL proteins and common mechanisms of pathogenesis. Here, we have studied molecular interactions between NCL proteins, concentrating specifically on the interactions of CLN5, the protein underlying the Finnish variant late infantile form of NCL (vLINCLFin).

RESULTS

We found that CLN5 interacts with several other NCL proteins namely, CLN1/PPT1, CLN2/TPP1, CLN3, CLN6 and CLN8. Furthermore, analysis of the intracellular targeting of CLN5 together with the interacting NCL proteins revealed that over-expression of PPT1 can facilitate the lysosomal transport of mutated CLN5FinMajor, normally residing in the ER and in the Golgi complex. The significance of the novel interaction between CLN5 and PPT1 was further supported by the finding that CLN5 was also able to bind the F1-ATPase, earlier shown to interact with PPT1.

CONCLUSION

We have described novel interactions between CLN5 and several NCL proteins, suggesting a modifying role for these proteins in the pathogenesis of individual NCL disorders. Among these novel interactions, binding of CLN5 to CLN1/PPT1 is suggested to be the most significant one, since over-expression of PPT1 was shown to influence on the intracellular trafficking of mutated CLN5, and they were shown to share a binding partner outside the NCL protein spectrum.

Retention of lysosomal protein CLN5 in the endoplasmic reticulum causes neuronal ceroid lipofuscinosis in Asian sibship

The neuronal ceroid lipofuscinoses (NCLs) form a group of autosomal recessively inherited neurodegenerative disorders that mainly affect children. Ten NCL forms can be distinguished by age at onset, clinicopathologic features, and genetics. In eight of these forms, the underlying genes have been identified. At present, approximately 10% of all patients do not fall into one of the eight known genetic forms of NCL. We have identified two Asian families with two novel homozygous mutations in the CLN5 gene. In the first Pakistani family, two children developed symptoms of an early juvenile NCL. After exclusion of mutations in genes known to be associated with this age of onset in families from many different countries (CLN1, CLN2, CLN3, CLN6, CLN8 and CLN10) SNP array-based homozygosity mapping led to the identification of a novel homozygous mutation c.1072_1073delTT (p.Leu358AlafsX4) in CLN5. In the second Afghan family, two children developed symptoms of a late infantile NCL. The mutation c.1137G>T (p.Trp379Cys) in CLN5 was identified. The affected children in these families represent the first reported CLN5 patients originating in Asian sibships. Expression analysis showed that mutant p.Leu358AlafsX4 CLN5 is truncated and lacks a used N-glycosylation site at Asn401. The missense mutation p.Trp379Cys affected neither the size nor glycosylation of the CLN5 protein. Double immunofluorescence microscopy showed that while the wild-type CLN5 protein is localized in lysosomes, both mutant CLN5 proteins are retained in the endoplasmic reticulum rather than reaching the lysosome.

Crystal structure and autoactivation pathway of the precursor form of human tripeptidyl-peptidase 1, the enzyme deficient in late infantile ceroid lipofuscinosis

Late infantile neuronal ceroid lipofuscinosis is a fatal childhood neurological disorder caused by a deficiency in the lysosomal protease tripeptidyl-peptidase 1 (TPP1). TPP1 represents the only known mammalian member of the S53 family of serine proteases, a group characterized by a subtilisin-like fold, a Ser-Glu-Asp catalytic triad, and an acidic pH optimum. TPP1 is synthesized as an inactive proenzyme (pro-TPP1) that is proteolytically processed into the active enzyme after exposure to low pH in vitro or targeting to the lysosome in vivo. In this study, we describe an endoglycosidase H-deglycosylated form of TPP1 containing four Asn-linked N-acetylglucosamines that is indistinguishable from fully glycosylated TPP1 in terms of autocatalytic processing of the proform and enzymatic properties of the mature protease. The crystal structure of deglycosylated pro-TPP1 was determined at 1.85 angstroms resolution. A large 151-residue C-shaped prodomain makes extensive contacts as it wraps around the surface of the catalytic domain with the two domains connected by a 24-residue flexible linker that passes through the substrate-binding groove. The proenzyme structure reveals suboptimal catalytic triad geometry with its propiece linker partially blocking the substrate-binding site, which together serve to prevent premature activation of the protease. Finally, we have identified numerous processing intermediates and propose a structural model that explains the pathway for TPP1 activation in vitro. These data provide new insights into TPP1 function and represent a valuable resource for constructing improved TPP1 variants for treatment of late infantile neuronal ceroid lipofuscinosis.

The clinical and genetic epidemiology of neuronal ceroid lipofuscinosis in Newfoundland

The neuronal ceroid lipofuscinoses (NCLs) are the commonest neurodegenerative disorders of children. The aims of this study were to determine the incidence of NCL in Newfoundland, identify the causative genes, and analyze the relationship between phenotype and genotype. Patients with NCL diagnosed between 1960 and 2005 were ascertained through the provincial genetics and pediatric neurology clinics. Fifty-two patients from 34 families were identified. DNA was obtained from 28/34 (82%) families; 18 families had mutations in the CLN2 gene, comprising five different mutations of which two were novel. One family had a CLN3 mutation, another had a novel mutation in CLN5, and five families shared the same mutation in CLN6. One family was misdiagnosed, and in two, molecular testing was inconclusive. Disease from CLN2 mutations had an earlier presentation (p = 0.003) and seizure onset (p < 0.001) compared with CLN6 mutation. There was a slower clinical course for those with CLN5 mutation compared with CLN2 mutation. NCL in Newfoundland has a high incidence, 1 in 7353 live births, and shows extensive genetic heterogeneity. The incidence of late infantile NCL, 9.0 per 100,000 (or 1 in 11,161) live births, is the highest reported in the world.

Residual levels of tripeptidyl-peptidase I activity dramatically ameliorate disease in late-infantile neuronal ceroid lipofuscinosis

Classical late-infantile neuronal ceroid lipofuscinosis (LINCL) is a hereditary neurodegenerative disease of childhood that is caused by mutations in the gene (CLN2) encoding the lysosomal protease tripeptidyl-peptidase I (TPPI). LINCL is fatal and there is no treatment of demonstrated efficacy in affected children but preclinical studies with AAV-mediated gene therapy have demonstrated promise in a mouse model. Here, we have generated mouse CLN2-mutants that express different amounts of TPPI activity to benchmark levels required for therapeutic benefits. Approximately 3% of normal TPPI activity in brain delayed disease onset and doubled lifespan to a median of approximately 9 months compared to mice expressing approximately 0.2% of normal levels. Expression of 6% of normal TPPI activity dramatically attenuated disease, with a median lifespan of approximately 20 months which approaches that of unaffected mice. While the lifespan of this hypomorph is shortened, disease is late-onset, less severe and progresses slowly compared to mice expressing lower TPPI levels. For gene therapy and other approaches that restore enzyme activity, these results suggest that 6% of normal TPPI activity throughout the CNS of affected individuals will provide a significant therapeutic benefit but higher levels will be required to cure this disease.

CLN2/TPP1 deficiency: the novel mutation IVS7-10A>G causes intron retention and is associated with a mild disease phenotype

The classical form of late infantile neuronal ceroid lipofuscinosis (LINCL) is a childhood hereditary neurodegenerative disease usually fatal in the first decade of life. The underlying gene, CLN2, encodes the lysosomal soluble enzyme tripeptidyl-peptidase 1 (TPP1). In a Portuguese patient with juvenile form of the disease, the histochemical study revealed the presence of curvilinear inclusions typical of LINCL. In vitro TPP1 activity was deficient in patient's cells. CLN2 gene analysis revealed the transition IVS7-10A>G (g.4196A>G) in both alleles. In silico analysis suggested that A-to-G change in the A-rich region of intron 7 could cause aberrant splicing of exon 8 by creating a novel acceptor splice site. However, because the wild-type acceptor of intron 7 is weak and it was not apparently affected, the severity of this mutation could not be established through sequencing data of gDNA. Normal level of spliced CLN2/mRNA was observed in patient's fibroblasts. In the cDNA, the 9-nt retention of intronic sequence (c.886_887ins9) was observed. The mutation is predicted to result in a protein with three extra amino acids between proline 295 and glycine 296. In patient's fibroblasts the level of mutant CLN2p was reduced to about 60% but the migration pattern was similar to the wild-type protein, suggesting that it was correctly targeted to the lysosomes. Taken together, these findings suggest that the first "ag" is selected for splicing and the mutant protein must retain some residual catalytic activity, thus explaining the late onset and the delayed progression of the disease.

Proteomics Analysis of Serum from Mutant Mice Reveals Lysosomal Proteins Selectively Transported by Each of the Two Mannose 6-Phosphate Receptors

Most mammalian cells contain two types of mannose 6-phosphate (Man-6-P) receptors (MPRs): the 300 kDa cation-independent (CI) MPR and 46 kDa cation-dependent (CD) MPR. The two MPRs have overlapping function in intracellular targeting of newly synthesized lysosomal proteins, but both are required for efficient targeting. Despite extensive investigation, the relative roles and specialized functions of each MPR in targeting of specific proteins remain questions of fundamental interest. One possibility is that most Man-6-P glycoproteins are transported by both MPRs, but there may be subsets that are preferentially transported by each. To investigate this, we have conducted a proteomics analysis of serum from mice lacking either MPR with the reasoning that lysosomal proteins that are selectively transported by a given MPR should be preferentially secreted into the bloodstream in its absence. We purified and identified Man-6-P glycoproteins and glycopeptides from wild-type, CDMPR-deficient, and CIMPR-deficient mouse serum and found both lysosomal proteins and proteins not currently thought to have lysosomal function. Different mass spectrometric approaches (spectral count analysis of nanospray LC-MS/MS experiments on unlabeled samples and LC-MALDI/TOF/TOF experiments on iTRAQ-labeled samples) revealed a number of proteins that appear specifically elevated in serum from each MPR-deficient mouse. Man-6-P glycoforms of cellular repressor of E1A-stimulated genes 1, tripeptidyl peptidase I, and heparanase were elevated in absence of the CDMPR and Man-6-P glycoforms of alpha-mannosidase B1, cathepsin D, and prosaposin were elevated in the absence of the CIMPR. Results were confirmed by Western blot analyses for select proteins. This study provides a comparison of different quantitative mass spectrometric approaches and provides the first report of proteins whose cellular targeting appears to be MPR-selective under physiological conditions.

Neurological deterioration in late infantile neuronal ceroid lipofuscinosis

BACKGROUND

Late infantile neuronal ceroid lipofuscinosis (LINCL) is associated with progressive degeneration of the brain and retina starting in early childhood.

METHODS

Thirty-two individual neurologic, ophthalmologic, and CNS imaging (MRI and MRS) assessments of 18 children with LINCL were analyzed. Disease severity was followed by two rating scales, one previously established but modified to solely assess the brain and exclude the retinal disease (modified Hamburg LINCL scale), and a newly developed scale, with expanded evaluation of the CNS impairment (Weill Cornell LINCL scale).

RESULTS

For the 18 children, the Weill Cornell scale yielded a closer correlation with both age and time since initial clinical manifestation of the disease than did the modified Hamburg scale. There were no significant differences as a function of age or time since initial manifestation of the disease in the rating scales among the most frequent CLN2 mutations (G3556C, 56% of all alleles or C3670T, 22% of all alleles). Measurements of cortical MRS N-acetyl-aspartate content, MRI ventricular, gray matter and white matter volume, and cortical apparent diffusion coefficient correlated to a variable degree with the age of the children and the time since initial clinical manifestation of the disease. All imaging measurements correlated better with the Weill Cornell CNS scale compared to the modified Hamburg LINCL scale.

CONCLUSION

The data suggest that the Weill Cornell late infantile neuronal ceroid lipofuscinosis (LINCL) scale, together with several of the MRI measurements, may be useful in the assessment of severity and progression of LINCL and for the evaluation of novel therapeutic strategies.

Timing of therapeutic intervention determines functional and survival outcomes in a mouse model of late infantile batten disease

Classical late infantile neuronal ceroid lipofuscinosis (cLINCL) is a monogenic disorder caused by the loss of tripeptidyl peptidase 1 (TPP1) activity as a result of mutations in CLN2. Absence of TPP1 results in lysosomal storage with an accompanying axonal degeneration throughout the central nervous system (CNS), which leads to progressive neurodegeneration and early death. In this study, we compared the efficacies of pre- and post-symptomatic injections of recombinant adeno-associated virus (AAV) for treating the cellular and functional abnormalities of CLN2 mutant mice. Intracranial injection of AAV1-hCLN2 resulted in widespread human TPP1 (hTPP1) activity in the brain that was 10-100-fold above wild-type levels. Injections before disease onset prevented storage and spared neurons from axonal degeneration, reflected by the preservation of motor function. Furthermore, the majority of CLN2 mutant mice treated pre-symptomatically lived for at least 330 days, compared with a median survival of 151 days in untreated CLN2 mutant controls. In contrast, although injection after disease onset ameliorated lysosomal storage, there was evidence of axonal degeneration, motor function showed limited recovery, and the animals had a median lifespan of 216 days. These data illustrate the importance of early intervention for enhanced therapeutic benefit, which may provide guidance in designing novel treatment strategies for cLINCL patients.

Late-infantile neuronal ceroid lipofuscinosis (CLN2/Jansky-Bielschowsky type) in Oman

This study was conducted to see the pattern of neuronal ceroid lipofuscinosis in Oman. Eleven children (10 male) with late-infantile neuronal ceroid lipofuscinosis were seen in 5 families. Most of the patients, 9 of 11 (81.8%), were CLN2 type (late-infantile neuronal ceroid lipofuscinosis or Jansky-Bielschowsky), and 2 patients were the atypical type. Five children were seen in 1 extended family. All children had onset with seizures except in 1 family. The majority had onset between ages 1 to 4 years. Nine and of the 11 children had onset with myoclonic seizures. Neuroregression and microcephaly were noted in all. All children had brain volume reduction and typical cerebellar atrophy. Ophthalmological examination was abnormal in all. Clinical features, histological findings, and genetic study reveal that CLN2 type is the most common form of neuronal ceroid lipofuscinosis. There is male predominance of 90.1% in this part of the Arab world.

Decreased T2 signal in the thalami may be a sign of lysosomal storage disease

INTRODUCTION

Lysosomal disorders are rare and are caused by genetically transmitted lysosomal enzyme deficiencies. A decreased T2 signal in the thalamus has occasionally been reported.

AIMS

Because the finding of bilateral abnormal signal intensity of the thalamus on T2-weighted images has not been systematically reviewed, and its value as a diagnostic tool critically evaluated, we carried out a systematic review of the literature.

METHODS

Articles in English with 30 trios of keywords were collected from PubMed. Exclusion criteria were lack of conventional T2-weighted images in the protocol and not being a human study. Finally, 111 articles were included. The thalamus was considered affected only if mentioned in the text or in the figure legends.

RESULTS

Some 117 patients with various lysosomal diseases and five patients with ceruloplasmin deficiency were reported to have a bilateral decrease in T2 signal intensity. At least one article reported a bilateral decrease in signal intensity of the thalami on T2-weighted images in association with GM1 and GM2 gangliosidosis and with Krabbe's disease, aspartylglucosaminuria, mannosidosis, fucosidosis, and mucolipidosis IV. Furthermore, thalamic alteration was a consistent finding in several types of neuronal ceroid lipofuscinosis (NCL) including CLN1 (infantile NCL), CLN2 (classic late infantile NCL), CLN3 (juvenile NCL), CLN5 (Finnish variant late infantile NCL), and CLN7 (Turkish variant late infantile NCL).

CONCLUSION

A decrease in T2 signal intensity in the thalami seems to be a sign of lysosomal disease.

Neuronal ceroid lipofuscinosis: a common pathway?

The neuronal ceroid lipofuscinoses are pediatric neurodegenerative diseases with common clinical features. Of the nine clinical variants (CLN1-CLN9), six have been genetically identified. Most variants manifest cell death and dysregulated sphingolipid metabolism, suggesting the proteins defective in these disorders may interact along one pathway. NCL patient-derived cell lines exhibit cell growth and apoptotic defects that reverse following transfection with the wild-type gene. The membrane-bound proteins CLN3, CLN6, and CLN8 complement each other, as do CLN1 and CLN2 proteins, with respect to growth and apoptosis. The CLN2 protein also corrects growth and apoptosis in CLN3-, CLN6-, and CLN8-deficient cell lines. Neither CLN1-deficient nor CLN2-deficient growth defects are corrected by CLN3, CLN6, and CLN8 proteins. CLN2, CLN3, CLN6, and CLN8 proteins co-immunoprecipitate and co-localize to early and/or recycling endosomes and lipid rafts. Additionally, CLN2p and CLN1p co-immunoprecipitate. The work presented supports interactions between NCL proteins occurring at multiple points along one pathway.

Enhanced survival of the LINCL mouse following CLN2 gene transfer using the rh.10 rhesus macaque-derived adeno-associated virus vector

Late infantile neuronal ceroid lipofuscinosis (LINCL) is a lysosomal storage disorder caused by mutations in the CLN2 gene and a deficiency of tripeptidyl peptidase I (TPP-I). Prior studies with adeno-associated virus (AAV) serotype 2 or 5 mediated transfer of the CLN2 complementary DNA to the central nervous system (CNS) of CLN2(-/-) mice cleared CNS storage granules, but provided no improvement in the phenotype or survival of this model of LINCL. In this study, AAV serotypes (AAV2, AAV5, AAV8, and AAVrh.10) were compared for the delivery of the same CLN2 expression cassette. AAVrh.10, derived from rhesus macaque, provided the highest TPP-I level and maximum spread beyond the site of injection. The AAVrh.10-based vector functioned equally well in naive rats and in rats previously immunized against human serotypes of AAV. When administered to the CNS of CLN2(-/-) mice, the AAVrh.10CLN2 vector provided widespread TPP-I activity comparable to that in the wild-type mice. Importantly, the AAVrh.10CLN2-treated CLN2(-/-) mice had significant reduction in CNS storage granules and demonstrated improvement in gait, nest-making abilities, seizures, balance beam function, and grip strength, as well as having a survival advantage.

Characterisation of lipofuscin-like lysosomal inclusion bodies from human placenta

A structural hallmark of lysosomes is heterogeneity of their contents. We describe a method for isolation of particulate materials from human placental lysosomes. After a methionine methyl ester-induced disruption of lysosomes and two density gradient centrifugations we obtained a homogeneous membrane fraction and another one enriched in particulate inclusions. The latter exhibited a yellow-brown coloration and contained bodies lacking a delimiting membrane, which were characterised by a granular pattern and high electron density. The lipofuscin-like inclusion materials were rich in tripeptidyl peptidase I, beta-glucuronidase, acid ceramidase and apolipoprotein D and contained proteins originating from diverse subcellular localisations. Here we show that human term placenta contains lipofuscin-like lysosomal inclusions, a phenomenon usually associated with senescence in postmitotic cells. These findings imply that a simple pelleting of a lysosomal lysate is not appropriate for the isolation of lysosomal membranes, as the inclusions tend to be sedimented with the membranes.

Two novel CLN5 mutations in a Portuguese patient with vLINCL: insights into molecular mechanisms of CLN5 deficiency

The neuronal ceroid-lipofuscinoses are the most common neurodegenerative disorders in childhood characterized by progressive blindness, epilepsy, brain atrophy, and premature death. Based on the age at onset, disease progression and ultrastructural features three classical (infantile, late-infantile, and juvenile) and three variant late-infantile forms are generally distinguished (Finnish variant, Costa Rican variant, and epilepsy with progressive motor retardation). The Finnish variant late-infantile form has been associated with CLN5 gene defects, with only five mutations described to date. We report a patient with vLINCL/CLN5 who represents the first evidence of the disease in the Portuguese population. Mutational screening revealed the previously described missense mutation c.835G>A (D279N) inherited from the mother, and two novel mutations, c.565C>T (Q189X) and c.335G>C (R112P) from paternal and maternal inheritance, respectively. Based on data here reported: (i) the number of possible mutations in CLN5 gene is now 7; (ii) the CLN5 Portuguese case represents the third description of the disease outside northern Europe; (iii) the CLN5/mRNA expression level reduced to 45% supports the existence of one mRNA non-producing allele, further noticeable at the protein level; (iv) Western blotting data using a specific antibody to human CLN5p provided evidence for the presence of four integral membrane isoforms in human fibroblasts; (v) data from differential expression of CLN2, CLN3, and CLN5 suggest down-regulation of CLN3 gene expression in CLN2 and CLN5-deficient human patients and this observation strengths the hypothesis of functional redundancy of the CLN system.

A frame shift mutation in canine TPP1 (the ortholog of human CLN2) in a juvenile Dachshund with neuronal ceroid lipofuscinosis

The neuronal ceroid lipofuscinoses (NCLs) are inherited lysosomal storage diseases characterized by progressive neuropathy and the accumulation of autofluorescent cytoplasmic granules. Clinical signs of a new canine NCL began in a 9-month-old male Dachshund with vomiting, mental dullness, and loss of previously learned commands and rapidly progressed to include disorientation, ataxia, visual deficits, generalized myoclonic seizures, and death at 12 months of age. Neurons throughout the CNS contained autofluorescent storage granules that stained with periodic acid-Schiff and Luxol fast blue stains. Electron microscopy revealed that the storage granule contents consisted of curvilinear-appearing material characteristic of human late infantile NCL caused by CLN2 mutations. Nucleotide sequence analysis of canine TPP1, the ortholog of human CLN2, revealed a single nucleotide deletion in exon 4 which predicted a frame shift with a premature stop codon. Brain tissue from the affected dog lacked detectable activity of the tripeptidyl-peptidase enzyme encoded by TPP1, whereas the specific activities of 15 other lysosomal enzymes were higher than those in the brains of three control dogs. The affected Dachshund was homozygous for the mutant c.325delC allele, his sire and dam were heterozygotes, and 181 unrelated dogs, including 77 Dachshunds, were all homozygous for the wild-type allele. A DNA assay that detects the mutant allele will help Dachshund breeders avoid producing affected puppies in future generations. Furthermore, this Dachshund NCL may prove to be a useful model for studying the pathogenesis of neurodegeneration in human late infantile NCL and for evaluating novel therapeutic interventions for this disease.