👤 P E M Taschner

The CLN3 gene is involved in juvenile neuronal ceroid lipofuscinosis (JNCL), or Batten-Spielmeyer-Vogt disease, a severe hereditary neurodegenerative lysosomal storage disorder characterized by progressive disease pathology, with loss of vision as the first symptom. Another characteristic of JNCL is the lysosomal accumulation of autofluorescent lipopigments, forming fingerprint storage patterns visible by electron microscopy. The function of the CLN3 protein is still unknown, although the evolutionarily conserved CLN3 protein is being functionally analysed using different experimental models. We have explored the potential of the nematode Caenorhabditis elegans as a model for Batten disease in order to bridge the gap between the unicellular yeast and very complex mouse JNCL models. C. elegans has three genes homologous to CLN3, for each of which deletion mutants were isolated. Cln-3.1 deletion mutants have a decreased lifespan, and cln-3.2 deletion mutants a decreased brood size. However, the neuronal or movement defects and aberrant lipopigment distribution or accumulation observed in JNCL were not found in the worms. To detect possible redundancy, single deletion mutants were crossed to obtain double and triple mutants, which were viable but showed no JNCL-specific defects. The cln-3 triple mutants show a more prominent decrease in lifespan and brood size, the latter most conspicuously at the end of the egg-laying period, suggesting premature ageing. To focus our functional analysis we examined the C. elegans cln-3 expression patterns, using promoter-GFP (green fluorescent protein) gene fusions. Fluorescence patterns suggest cln-3.1 expression in the intestine, cln-3.2 expression in the hypoderm, and cln-3.3 expression in intestinal muscle, male-specific posterior muscle and hypoderm. Further life stage- and tissue-specific analysis of the processes causing the phenotype of the cln-3 triple mutants may provide more information about the function of the cln-3 protein and contribute to a better understanding of the basic processes affected in Batten disease patients. Show less

The neuronal ceroid lipofuscinoses (NCL) are worldwide the most common lysosomal storage disorders of childhood. Clinical features often include progressive visual impairment, seizures, psychomotor deterioration, dementia, and premature death. Most NCL cases are caused by mutations in the CLN1, CLN2 and CLN3 genes, which play an essential role in lysosomal protein degradation. Laboratory diagnostics for a patient suspected of NCL should start with enzyme analysis in the case of INCL and LINCL and investigation of lymphocyte vacuolisation for JNCL. Diagnosis at the protein level is not available for JNCL, but CLN3 mutation analysis is possible. The carrier status of healthy relatives in families with known mutations in either CLN1, CLN2, CLN3 or CLN6 can be determined with certainty by mutation analysis. Show less

Thirty-eight mutations and seven polymorphisms have recently been reported in the genes underlying the neuronal ceroid lipofuscinoses (NCLs) including 11 new mutations described here. A total of 114 mutations and 28 polymorphisms have now been described in the five human genes identified which cause NCL. Thirty-eight mutations are recorded for CLN1/PPT; 40 for CLN2/TTP-1, 31 for CLN3, four for CLN5, one for CLN8. Two mutations have been described in animal genes (cln8/mnd, CTSD). All mutations in NCL genes are contained in the NCL Mutation Database (http://www.ucl.ac.uk/NCL). Show less

Neuronal ceroid lipofuscinoses (NCLs) are the most common hereditary neurodegenerative disorders of childhood. The first symptom of this heterogeneous group of devastating lysosomal storage diseases is progressive visual failure. The different forms of NCL can be distinguished by age of onset, clinical features and the characteristics of the accumulated materials. The juvenile form, Batten-Spielmeyer-Vogt disease which is caused by mutations in the CLN3 gene, is the most frequent form of the disease in which loss of vision becomes apparent around the age of 5-8 years. The gene was found to encode a novel integral membrane protein localizing to the lysosomes, confirming that the primary defect in NCL is in lysosomal function. The CLN3 protein function is still unknown, and is examined in several model organisms. We are studying the nematode Caenorhabditis elegans, and have identified three CLN3 homologues. In order to investigate the role of the CLN3 protein in C. elegans, Cecln-3 deletion mutants are being isolated from an ethyl methanesulphonate (EMS)-induced deletion mutant library. Examination of these mutants may provide us with information that will help in dissecting the processes in which the CLN3 protein is involved. In this library two mutated C. elegans Cln-3 loci have been identified, of which one mutant, NL748, was isolated. This mutant contains a deletion of the whole gene. The deletion mutant was characterized with regard to life expectancy, and showed no significant differences when compared with wild-type. Show less

Batten disease, a degenerative neurological disorder with juvenile onset, is the most common form of the neuronal ceroid lipofuscinoses. Mutations in the CLN3 gene cause Batten disease. To facilitate studies of Batten disease pathogenesis and treatment, a murine model was created by targeted disruption of the Cln3 gene. Mice homozygous for the disrupted Cln3 allele had a neuronal storage disorder resembling that seen in Batten disease patients: there was widespread and progressive intracellular accumulation of autofluorescent material that by EM displayed a multilamellar rectilinear/fingerprint appearance. Inclusions contained subunit c of mitochondrial ATP synthase. Mutant animals also showed neuropathological abnormalities with loss of certain cortical interneurons and hypertrophy of many interneuron populations in the hippocampus. Finally, as is true in Batten disease patients, there was increased activity in the brain of the lysosomal protease Cln2/TPP-1. Our findings are evidence that the Cln3-deficient mouse provides a valuable model for studying Batten disease. Show less

JNCL is a neurodegenerative disease of childhood caused by mutations in the CLN3 gene. A mouse model for JNCL was created by disrupting exons 1-6 of Cln3, resulting in a null allele. Cln3 null mice appear clinically normal at 5 months of age; however, like JNCL patients, they exhibit intracellular accumulation of autofluorescent material. A second approach will generate mice in which exons 7 and 8 of Cln3 are deleted, mimicking the common mutation in JNCL patients. Show less

The recent isolation of the CLN3 gene involved in Batten disease (juvenile neuronal ceroid lipofuscinosis) creates possibilities for direct detection of mutations which can confirm or indicate the clinical diagnosis of Batten disease. We have designed a rapid and reliable allele specific PCR test for the detection of the major deletion, which can be used in carrier diagnosis, presymptomatic diagnosis, and prenatal diagnosis. Show less

Batten disease (juvenile-onset neuronal ceroid lipofuscinosis [JNCL]) is an autosomal recessive condition characterized by accumulation of lipopigments (lipofuscin and ceroid) in neurons and other cell types. The Batten disease gene, CLN3, was recently isolated, and four disease-causing mutations were identified, including a 1.02-kb deletion that is present in the majority of patients (The International Batten Disease Consortium 1995). One hundred eighty-eight unrelated patients with JNCL were screened in this study to determine how many disease chromosomes carried the 1.02-kb deletion and how many carried other mutations in CLN3. One hundred thirty-nine patients (74%) were found to have the 1.02-kb deletion on both chromosomes, whereas 49 patients (41 heterozygous for the 1.02-kb deletion) had mutations other than the 1.02-kb deletion. SSCP analysis and direct sequencing were used to screen for new mutations in these individuals. Nineteen novel mutations were found: six missense mutations, five nonsense mutations, three small deletions, three small insertions, one intronic mutation, and one splice-site mutation. This report brings the total number of disease-associated mutations in CLN3 to 23. All patients homozygous for mutations predicted to give rise to truncated proteins were found to have classical JNCL. However, a proportion of the patients (n = 4) who were compound heterozygotes for a missense mutation and the 1.02-kb deletion were found to display an atypical phenotype that was dominated by visual failure rather than by severe neurodegeneration. All missense mutations were found to affect residues conserved between the human protein and homologues in diverse species. Show less

We recently cloned a cDNA for CLN3, the gene for juvenile-onset neuronal ceroid lipofuscinosis or Batten disease. To resolve the genomic organization we used a cosmid clone containing CLN3 to sequence the entire gene in addition to 1.1 kb 5' of the start of the published CLN3 cDNA and 0.3 kb 3' to the polyadenylation site. CLN3 is organized into at least 15 exons spanning 15 kb and ranging from 47 to 356 bp. The 14 introns vary from 80 to 4227 bp, and all exon/intron junction sequences conform to the GT/AG rule. Numerous repetitive Alu elements are present within the introns and 5'- and 3'-untranslated regions. The 5' region of the CLN3 gene contains several potential transcription regulatory elements but no consensus TATA-1 box was identified. CLN3 is homologous to 27 deposited human ESTs, and sequence comparisons suggest alternative splicing of the gene and the existence of transcribed sequences upstream to the start of the published CLN3 cDNA. Show less

A murine cDNA clone was isolated by screening a mouse cDNA library with the human CLN3 cDNA. Sequence analysis indicates that the corresponding CLN3 proteins are highly homologous. We have compared these with recently identified CLN3 sequences from the dog, the nematode C. elegans, and baker's yeast S. cerevisiae. The CLN3 protein is remarkably conserved across eukaryotic species. Several protein modification sites which may be crucial for the function of the protein are conserved. Show less

A strategy for detection of mutations in CLN3, the gene for Batten disease or juvenile onset neuronal ceroid lipofuscinosis, has been devised using a technique which detects conformation polymorphisms and direct sequencing of genomic DNA fragments. We define two mutations found uniquely in Finnish patients, one a large deletion (2.8 kb), the other a point mutation affecting the 5'splice donor site of an intron. Show less

The genomic sequence of the human CLN3 gene, which is defective in juvenile onset neuronal ceroid lipofuscinosis (Batten disease) is being delineated using a variety of methods. A Saccharomyces cerevisiae gene, YHC3 (for Yeast Homologue to human CLN3), which is highly similar to the human disease gene, has been identified by computer-aided homology searching. Topology predictions indicate the CLN3 protein contains six transmembrane segments. Most similarity between the human and yeast proteins lies either in the transmembrane segments or along one face of the predicted protein structure. Show less

A yeast artificial chromosome (YAC) contig has been constructed in 16p12.1-p11.2 that encompasses three loci (D16S288, D16S299, and D16S298) closely linked to the gene causing Batten disease or juvenile-onset neuronal ceroid lipofuscinosis (CLN3). The physical map has been ordered using 42 sequence tagged sites. Four genes, interleukin-4 receptor (IL4R), phenol-preferring phenol sulfotransferase (STP), monoamine-preferring phenol sulfotransferase (STM), and sialophorin (SPN), have been mapped to the YAC contig. A partial genomic restriction map has been constructed to confirm the order and distances between D16S298, predicted to be the locus closest to CLN3. The overlapping genomic clones are a valuable resource for cloning the Batten gene (CLN3) and other genes in the region. Show less

Accurate diagnosis of neuronal ceroid lipofuscinosis (NCL) is important for a correct prognosis of the disease and for genetic counseling. Up to now, no direct diagnostic test has been available for NCL. The clinical diagnosis is made on the basis of symptoms, neurophysiological, neuroradiological, and specific lipopigment pattern data. Recent advances in the genetics of NCL have enabled us to use polymorphic DNA markers linked to the CLN1 and CLN3 loci as a tool in the differential diagnosis of NCL. We have applied genetic analysis with polymorphic DNA markers flanking the CLN3 gene on chromosome 16 to two consanguineous families in which NCL occurs. In the first family, which is of Turkish extraction, two patients suffering from a protracted form of juvenile NCL previously had been diagnosed with juvenile NCL. Haplotypes from this family indicate that the patients and their healthy sibling are haplo-identical, suggesting that this protracted form of juvenile NCL is not linked to the CLN3 locus. In the second family, which is of Moroccan origin, one patient suffers from the early juvenile variant of NCL (Lake-Cavanagh). In this family, the patient and one of the healthy siblings have identical haplotypes, excluding linkage of early juvenile NCL to the CLN3 locus on 16p12.1-11.2. Therefore, these cases from different populations demonstrate that haplotype analysis can be used as an additional method to exclude the diagnosis of juvenile NCL. Show less

Batten disease, or the juvenile form of neuronal ceroid lipofuscinosis, is an autosomal recessive neurodegenerative disorder manifesting with progressive blindness, seizures, and dementia, leading to an early death. The CLN3 locus which is involved in Batten disease had been localized to chromosome 16p11.2. Linkage disequilibrium has been observed between CLN3 and polymorphic microsatellite markers D16S288, D16S299, and D16S298, making carrier detection and prenatal diagnosis by haplotype analysis possible. For the purpose of carrier detection, haplotypes from Dutch Batten patients and their families were constructed. Most patients share the same D16S298 allele, suggesting the presence of a founder effect in the Dutch population. In a large inbred Dutch family, in which Batten disease occurs with high frequency, haplotype analysis has been carried out with high accuracy for carrier detection. Show less

CLN3 has been mapped genetically to 16p12, to the interval between D16S288 and D16S383, a sex-averaged genetic distance of 2.1 cM. Analysis of disease haplotypes for four microsatellite markers in this interval, D16S288, D16S299, D16S298, and SPN, has shown significant allelic association between one allele at each of these loci and CLN3. All four of the associated markers were used as nucleation sites in the isolation of genomic clones (YACs). A contig was assembled which contains 3 of the 4 associated markers and which confirmed the relative order of these markers. Marker D16S272 has been located on the physical map between D16S288 and D16S299. Restriction mapping has demonstrated the location of possible CpG islands. One gene, STP, has been localised on the YAC contig proximal to D16S298 and is therefore a candidate for CLN3. Other genes, including IL4R, SGLT2, and UQCRC2, have been excluded from this region. Show less

Haplotype analysis in a collaborative collection of 143 families with juvenile-onset neuronal ceroid lipofuscinosis (JNCL) or Batten (Spielmeyer-Vogt-Sjögren) disease has permitted refined localization of the disease gene, CLN3, which was assigned to chromosome 16 in 1989. Recombination events in four maternal meioses delimit new flanking genetic markers for CLN3 which localize the gene to the chromosome interval 16p12.1-11.2 between microsatellite markers D16S288 and D16S383. This narrows the position of CLN3 to a region of 2.1 cM, a significant reduction from the previous best interval. Using haplotypes, analysis of the strong linkage disequilibrium that exists between genetic markers within the D16S288-D16S383 interval and CLN3 shows that CLN3 is in closest proximity to loci D16S299 and D16S298. Analysis of markers across the D16S288-D16S383 region in four families with a variant form of JNCL characterized histologically by cytosomal granular osmiophilic deposits (GROD) has excluded linkage of the gene locus to the CLN3 region of chromosome 16, suggesting that JNCL with GROD is not an allelic form of JNCL. Show less

The juvenile-onset subtype of the neuronal ceroid lipofuscinoses (JNCL) is well known [Hofman, ISBN90-71534-19-7 1990] and ultrastructurally characterized by fingerprints and/or curvilinear bodies in many cell types. Linkage studies indicated a most likely location for CLN3, the gene involved in JNCL, in the interval between loci D16S297 and D16S57, within close proximity of the loci D16S298 and D16S299 [Mitchison et al., Genomics 22:465-468, 1993]. We present two sibs with a late onset progressive disease of mental deterioration, progressive macular degeneration, motor disturbances, and epilepsy. Histological symptoms of neuronal ceroid lipofuscinosis and ultrastructural granular osmiophilic deposits (GROD) in lymphocytes and neurons are found. Individual haplotypes at polymorphic marker loci on chromosome 16 were constructed to determine whether JNCL with GROD is linked to the CLN3 locus. Show less

The gene that is involved in juvenile neuronal ceroid lipofuscinosis (JNCL), or Batten disease--CLN3--has been localized to 16p12, and the mutation shows a strong association with alleles of microsatellite markers D16S298, D16S299, and D16S288. Recently, haplotype analysis of a Batten patient from a consanguineous relationship indicated homozygosity for a D16S298 null allele. PCR analysis with different primers on DNA from the patient and his family suggests the presence of a cytogenetically undetectable deletion, which was confirmed by Southern blot analysis. The microdeletion is embedded in a region containing chromosome 16-specific repeated sequences. However, putative candidates for CLN3, members of the highly homologous sulfotransferase gene family, which are also present in this region in several copies, were not deleted in the patient. If the microdeletion in this patient is responsible for Batten disease, then we conclude that the sulfotransferase genes are probably not involved in JNCL. By use of markers and probes flanking D16S298, the maximum size of the microdeletion was determined to be approximately 29 kb. The microdeletion may affect the CLN3 gene, which is expected to be in close proximity to D16S298. Show less

The gene for Batten disease (juvenile-onset neuronal ceroid lipofuscinosis, or Spielmeyer-Sjögren disease), CLN3, maps to 16p11.2-12.1. Four microsatellite markers--D16S288, D16S299, D16S298, and SPN--are in strong linkage disequilibrium with CLN3 in 142 families from 16 different countries. These markers span a candidate region of approximately 2.1 cM. CLN3 is most prevalent in northern European populations and is especially enriched in the isolated Finnish population, with an incidence of 1:21,000. Linkage disequilibrium mapping was applied to further refine the localization of CLN3 in 27 Finnish families by using linkage disequilibrium data and information about the population history of Finland to estimate the distance of the closest markers from CLN3. CLN3 is predicted to lie 8.8 kb (range 6.3-13.8 kb) from D16S298 and 165.4 kb (132.4-218.1 kb) from D16S299. Enrichment of allele "6" at D16S298 (on 96% of Finnish and 92% of European CLN3 chromosomes) provides strong evidence that the same major mutation is responsible for Batten disease in Finland as in most other European countries and that it is therefore not a Finnish mutation. Genealogical studies show that Batten disease is widespread throughout the densely populated regions of Finland. The ancestors of two Finnish patients carrying rare alleles "3" and "5" at D16S298 in heterozygous form originate from the southwestern coast of Finland, and these probably represent other foreign mutations. Analysis of the number and distribution of CLN3 haplotypes from 12 European countries provides evidence that more than one mutation has arisen in Europe. Show less

CLN3, the gene for juvenile-onset neuronal ceroid lipofuscinosis (JNCL) or Batten disease, has been localized by genetic linkage analysis to chromosome 16p between loci D16S297 and D16S57. We have now further refined the localization of CLN3 by haplotype analysis using two new microsatellite markers from loci D16S383 and SPN in the D16S297-D16S57 interval on a larger collaborative family resource consisting of 142 JNCL pedigrees. Crossover events in 3 maternal meioses define new flanking markers for CLN3 and localize the gene to the interval at 16p12.1-p11.2 between D16S288 and D16S383, which corresponds to a genetic distance of 2.1 cM. Within this interval 4 microsatellite loci are in strong linkage disequilibrium with CLN3, and extended haplotype analysis of the associated alleles indicates that CLN3 is in closest proximity to loci D16S299 and D16S298. Show less