Sphingolipid activator proteins (SAPs) are stored together with glycosphingolipids in the infantile neuronal ceroid-lipofuscinosis (INCL)

Lysosomal alterations and decreased electrophysiological activity in CLN3 disease patient-derived cortical neurons

CLN3 disease is a lysosomal storage disorder associated with fatal neurodegeneration that is caused by mutations in CLN3, with most affected individuals carrying at least one allele with a 966 bp deletion. Using CRISPR/Cas9, we corrected the 966 bp deletion mutation in human induced pluripotent stem cells (iPSCs) of a compound heterozygous patient (CLN3 Δ 966 bp and E295K). We differentiated these isogenic iPSCs, and iPSCs from an unrelated healthy control donor, to neurons and identified disease-related changes relating to protein synthesis, trafficking and degradation, and in neuronal activity, which were not apparent in CLN3-corrected or healthy control neurons. CLN3 neurons showed numerous membrane-bound vacuoles containing diverse storage material and hyperglycosylation of the lysosomal LAMP1 protein. Proteomic analysis showed increase in lysosomal-related proteins and many ribosomal subunit proteins in CLN3 neurons, accompanied by downregulation of proteins related to axon guidance and endocytosis. CLN3 neurons also had lower electrophysical activity as recorded using microelectrode arrays. These data implicate inter-related pathways in protein homeostasis and neurite arborization as contributing to CLN3 disease, and which could be potential targets for therapy.

Insulin-Like Growth Factors in the Pathogenesis of Neurological Diseases in Children

Insulin-like growth factors play a key role for neuronal growth, differentiation, the survival of neurons and synaptic formation. The action of IGF-1 is most pronounced in the developing brain. In this paper we will try to give an answer to the following questions: Why are studies in children important? What clinical studies in neonatal asphyxia, infantile spasms, progressive encephalopathy-hypsarrhythmia-optical atrophy (PEHO) syndrome, infantile ceroid lipofuscinosis (INCL), autistic spectrum disorders (ASD) and subacute sclerosing encephalopathy (SSPE) have been carried out? What are IGF-based therapeutic strategies? What are the therapeutic approaches? We conclude that there are now great hopes for the therapeutic use of IGF-1 for some neurological disorders (particularly ASD).

Neuronal ceroid lipofuscinosis associated with an MFSD8 mutation in Chihuahuas

The neuronal ceroid lipofuscinoses (NCLs) are hereditary neurodegenerative disorders characterized by progressive declines in neurological functions, seizures, and premature death. NCLs result from mutations in at least 13 different genes. Canine versions of the NCLs can serve as important models in developing effective therapeutic interventions for these diseases. NCLs have been described in a number of dog breeds, including Chihuahuas. Studies were undertaken to further characterize the pathology of Chihuahua NCL and to verify its molecular genetic basis. Four unrelated client owned Chihuahuas from Japan, Italy and England that exhibited progressive neurological signs consistent with a diagnosis of NCL underwent neurological examinations. Brain and in some cases also retinal and heart tissues were examined postmortem for the presence of lysosomal storage bodies characteristic of NCL. The affected dogs exhibited massive accumulation of autofluorescent lysosomal storage bodies in the brain, retina and heart accompanied by brain atrophy and retinal degeneration. The dogs were screened for known canine NCL mutations previously reported in a variety of dog breeds. All 4 dogs were homozygous for the MFSD8 single base pair deletion (MFSD8:c.843delT) previously associated with NCL in a Chinese Crested dog and in 2 affected littermate Chihuahuas from Scotland. The dogs were all homozygous for the normal alleles at the other genetic loci known to cause different forms of canine NCL. The MFSD8:c.843delT mutation was not present in 57 Chihuahuas that were either clinically normal or suffered from unrelated diseases or in 1761 unaffected dogs representing 186 other breeds. Based on these data it is almost certain that the MFSD8:c.843delT mutation is the cause of NCL in Chihuahuas. Because the disorder occurred in widely separated geographic locations or in unrelated dogs from the same country, it is likely that the mutant allele is widespread among Chihuahuas. Genetic testing for this mutation in other Chihuahuas is therefore likely to identify intact dogs with the mutant allele that could be used to establish a research colony that could be used to test potential therapeutic interventions for the corresponding human disease.

Analysis of NCL Proteins from an Evolutionary Standpoint

The Neuronal Ceroid Lipofuscinoses (NCLs) are the most common group of neurodegenerative disorders of childhood. While mutations in eight different genes have been shown to be responsible for these clinically distinct types of NCL, the NCLs share many clinical and pathological similarities. We have conducted an exhaustive Basic Local Alignment Search Tool (BLAST) analysis of the human protein sequences for each of the eight known NCL proteins- CLN1, CLN2, CLN3, CLN5, CLN6, CLN7, CLN8 and CLN10. The number of homologous species per CLN-protein identified by BLAST searches varies depending on the parameters set for the BLAST search. For example, a lower threshold is able to pull up more homologous sequences whereas a higher threshold decreases this number. Nevertheless, the clade confines are consistent despite this variation in BLAST searching parameters. Further phylogenetic analyses on the appearance of NCL proteins through evolution reveals a different time line for the appearance of the CLN-proteins. Moreover, divergence of each protein shows a different pattern, providing important clues on the evolving role of these proteins. We present and review in-depth bioinformatic analysis of the NCL proteins and classify the CLN-proteins into families based on their structures and evolutionary relationships, respectively. Based on these analyses, we have grouped the CLN-proteins into common clades indicating a common evolving pathway within the evolutionary tree of life. CLN2 is grouped in Eubacteria, CLN1 and CLN10 in Viridiplantae, CLN3 in Fungi/ Metazoa, CLN7 in Bilateria and CLN5, CLN6 and CLN8 in Euteleostomi.

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.

Quantification of mRNAs encoding proteins of the glycosphingolipid catabolism in mouse models of GM2 gangliosidoses and sphingolipid activator protein precursor (prosaposin) deficiency

We have investigated the mRNA amounts of six lysosomal proteins (beta-hexosaminidase alpha- and beta-subunit, sphingolipid activator protein precursor, GM2 activator protein, lysosomal sialidase, beta-glucocerebrosidase) involved in the degradation of glycosphingolipids. We analyzed extracts from brain tissues of mouse models for lysosomal storage diseases, i.e., the GM2 gangliosidoses and the deficiency of the sphingolipid activator protein precursor (prosaposin). The mRNA levels were quantified by real-time reverse transcription-polymerase chain reaction. Although storage of the respective lysosomal proteins has been reported in human and mice, no increase of their mRNA amounts could be detected here. Our results indicate that there is no transcriptional upregulation of lysosomal proteins in the examined neuronal storage disorders.

Batten's disease: clues to neuronal protein catabolism in lysosomes

Neuronal ceroid lipofuscinosis (Batten disease) encompasses a group of 8 or more inherited lysosomal storage diseases, with an overall frequency of 1 in 12,500 births. All are characterized by progressive blindness and dementia and were initially classified on the basis of age of onset, clinical phenotype and ultrastructural characterization of the storage material as granular osmiophilic deposits, curvilinear bodies or fingerprint bodies. Recent research has shown that the various forms of Batten disease result from mutations in at least 8 genes which code for proteins involved in different aspects of lysosomal protein catabolism. These include palmitoyl:protein thioesterase 1 (CLN1), tripeptidylpeptidase 1 (CLN2), cathepsin D (CLN8), and two membrane proteins of unknown function (CLN3 and CLN5). Biochemically, Batten disease is characterized by the accumulation in neurons and other cells of an autofluorescent pigment which has resisted many attempts at analysis. In this review we attempt to relate our current understanding of the nature of the storage material in Batten disease with this genetic information. We conclude that the 8 genes probably code for proteins which facilitate the degradation of post-translationally modified proteins in lysosomes, suggesting that the turnover of these proteins is highest in cortical neurons.

Brain lysosomal hydrolases in neuronal ceroid-lipofuscinoses

Although the neuronal ceroid-lipofuscinoses (NCLs) are often referred to as lysosomal storage disorders, information on brain lysosomal hydrolases in NCLs is not available. We have determined the specific activities of several acid hydrolases in postmortem brain gray matter of infantile (INCL), late infantile (LINCL), juvenile (JNCL), and adult (ANCL) forms of NCL, patients affected with other neurological disorders (ON), and normal controls. The specific activities of beta-hexosaminidase A and B were significantly high in JNCL gray matter, whereas in LINCL, the increase is significant only in beta-hexosaminidase compared to the controls. A significant increase in the activities of alpha-mannosidase, beta-glucuronidase, and acid phosphatase was also observed in LINCL and JNCL patients compared to the control values. beta-galactosidase activity was also found to be elevated in JNCL brains over the controls. In contrast, activities of beta-glucosidase and sialidase appeared to be lowered in INCL and LINCL. On the other hand, alpha-fucosidase, beta-mannosidase, and sulfatase were unaffected in NCLs brains. Thus, the present data indicate NCLs related abnormalities in some of the acid hydrolases in brain gray matter, which are primarily glycoproteins of lysosomal origin. These data in conjuction with the reported association of sphingolipid activator proteins (SAP) A and D and lysosomal glycoproteins with NCL storage bodies imply abberations in the glycoconjugate metabolism and lysosomal function.