Infantile neuronal ceroid lipofuscinosis (CLN1): linkage disequilibrium in the Finnish population and evidence that variant late infantile form (variant CLN2) represents a nonallelic locus

Two forms of neuronal ceroid lipofuscinosis (CLN) are enriched in the Finnish population: the infantile form (CLN1), which is the most common progressive encephalopathy of small children, and the variant late infantile form (variant CLN2), which is a rare, atypical form of neuronal ceroid lipofuscinosis. We recently established the linkage of the infantile form (CLN1) to the short arm of chromosome 1 close to the anchor marker D1S7. Here we demonstrate a linkage disequilibrium of CLN1 chromosomes using the two closest markers, DIS62 and L-MYC at the short arm of chromosome 1 (P less than 0.0025). The results of linkage analyses in Finnish variant CLN2 families using the markers linked to CLN1 revealed an exclusion; i.e., this form of CLN is caused by a locus different from that of CLN1. This finding was confirmed with the result of the M-test for heterogeneity. The genealogical data collected further support the molecular genetic findings and provide evidence that the mutation causing CLN1 in Finland is very old, whereas the mutation causing the variant CLN2 could be a result of a younger, i.e., more recent founder effect.     

Pathogenesis and therapies for infantile neuronal ceroid lipofuscinosis (infantile CLN1 disease)

The neuronal ceroid lipofuscinoses (NCL, Batten disease) are a group of inherited neurodegenerative diseases. Infantile neuronal ceroid lipofuscinosis (INCL, infantile Batten disease, or infantile CLN1 disease) is caused by a deficiency in the soluble lysosomal enzyme palmitoyl protein thioesterase-1 (PPT1) and has the earliest onset and fastest progression of all the NCLs. Several therapeutic strategies including enzyme replacement, gene therapy, stem cell-mediated therapy, and small molecule drugs have resulted in minimal to modest improvements in the murine model of PPT1-deficiency. However, more recent studies using various combinations of these approaches have shown more promising results; in some instances more than doubling the lifespan of PPT1-deficient mice. These combination therapies that target different pathogenic mechanisms may offer the hope of treating this profoundly neurodegenerative disorder. Similar approaches may be useful when treating other forms of NCL caused by deficiencies in soluble lysosomal proteins. Different therapeutic targets will need to be identified and novel strategies developed in order to effectively treat forms of NCL caused by deficiencies in integral membrane proteins such as juvenile neuronal ceroid lipofuscinosis. Finally, the challenge with all of the NCLs will lie in early diagnosis, improving the efficacy of the treatments, and effectively translating them into the clinic. This article is part of a Special Issue entitled: The Neuronal Ceroid Lipofuscinoses or Batten Disease.     

The role of ceroid lipofuscinosis neuronal protein 5 (CLN5) in endosomal sorting

Mutations in the gene encoding CLN5 are the cause of Finnish variant late infantile Neuronal Ceroid Lipofuscinosis (NCL), and the gene encoding CLN5 is 1 of 10 genes (encoding CLN1 to CLN9 and cathepsin D) whose germ line mutations result in a group of recessive disorders of childhood. Although CLN5 localizes to the lysosomal compartment, its function remains unknown. We have uncovered an interaction between CLN5 and sortilin, the lysosomal sorting receptor. However, CLN5, unlike prosaposin, does not require sortilin to localize to the lysosomal compartment. We demonstrate that in CLN5-depleted HeLa cells, the lysosomal sorting receptors sortilin and cation-independent mannose 6-phosphate receptor (CI-MPR) are degraded in lysosomes due to a defect in recruitment of the retromer (an endosome-to-Golgi compartment trafficking component). In addition, we show that the retromer recruitment machinery is also affected by CLN5 depletion, as we found less loaded Rab7, which is required to recruit retromer. Taken together, our results support a role for CLN5 in controlling the itinerary of the lysosomal sorting receptors by regulating retromer recruitment at the endosome.     

Kufs disease, the major adult form of neuronal ceroid lipofuscinosis, caused by mutations in CLN6

The molecular basis of Kufs disease is unknown, whereas a series of genes accounting for most of the childhood-onset forms of neuronal ceroid lipofuscinosis (NCL) have been identified. Diagnosis of Kufs disease is difficult because the characteristic lipopigment is largely confined to neurons and can require a brain biopsy or autopsy for final diagnosis. We mapped four families with Kufs disease for whom there was good evidence of autosomal-recessive inheritance and found two peaks on chromosome 15. Three of the families were affected by Kufs type A disease and presented with progressive myoclonus epilepsy, and one was affected by type B (presenting with dementia and motor system dysfunction). Sequencing of a candidate gene in one peak shared by all four families identified no mutations, but sequencing of CLN6, found in the second peak and shared by only the three families affected by Kufs type A disease, revealed pathogenic mutations in all three families. We subsequently sequenced CLN6 in eight other families, three of which were affected by recessive Kufs type A disease. Mutations in both CLN6 alleles were found in the three type A cases and in one family affected by unclassified Kufs disease. Mutations in CLN6 are the major cause of recessive Kufs type A disease. The phenotypic differences between variant late-infantile NCL, previously found to be caused by CLN6, and Kufs type A disease are striking; there is a much later age at onset and lack of visual involvement in the latter. Sequencing of CLN6 will provide a simple diagnostic strategy in this disorder, in which definitive identification usually requires invasive biopsy.     

青少年型神经元蜡样脂褐质沉积病(JNCL)的发病机制

神经元蜡样脂褐质沉积病(Neuronal ceroid lipofuscinosis, NCLs)是一组儿科神经退行性变疾病, 青少年型神经元蜡样脂褐质沉积病(Juvenile neuronal ceroid lipofuscinosis, JNCL)是其中一型。其临床表现包括视网膜退化进而失明、癫痫以及进行性的认知和运动能力的减退。本文综述了其发病机制, 包括凋亡、自噬、质膜相关的功能障碍、氧化应激与NO转导通路受阻、线粒体和溶酶体功能障碍、胞内pH失衡等。其中研究最为清楚的是细胞凋亡和自噬两种方式。在凋亡中, CLN3基因正常功能的缺陷导致神经酰胺的积累, 导致线粒体膜通透性增加(MMP), 并最终引发依赖胱酰蛋白酶(Caspase)以及非依赖胱酰蛋白酶的凋亡。自噬既有发生又有被破坏, 其破坏的主要原因是自噬小泡的不成熟导致自噬不能有效循环。本文对发病机制, 尤其是其细胞死亡的途径的阐述, 将有助于对JNCL等神经退行性病变一类疾病的认识。     

Localization of juvenile, but not late-infantile, neuronal ceroid lipofuscinosis on chromosome 16.

The neuronal ceroid lipofuscinoses (NCL) are a group of progressive neurodegenerative disorders characterized by the deposition of autofluorescent proteinaceous fingerprint or curvilinear bodies. We have found that CLN3, the gene underlying the juvenile form of NCL, is very tightly linked to the dinucleotide repeat marker D16S285 on chromosome 16. Integration of D16S285 into the genetic map of chromosome 16 by using the Centre d'Etude du Polymorphisme Humain panel of reference pedigrees yielded a favored marker order in the CLN3 region of qtel-D16S150-.08-D16S285-.04-D16S148-.02-D16S 67-ptel. The most likely location of the disease gene, near D16S285 in the D16S150-D16S148 interval, was favored by odds of greater than 10(4):1 over the adjacent D16S148-D16S67 interval, which was recently reported as the minimum candidate region. Analysis of D16S285 in pedigrees with late-infantile NCL virtually excluded the CLN3 region, suggesting that these two forms of NCL are genetically distinct.     

Genetic heterogeneity in neuronal ceroid lipofuscinosis (NCL): Evidence that the late-infantile subtype (Jansky-Bielschowsky disease; CLN2) is not an allelic form of the juvenile or infantile subtypes

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders characterized by the accumulation of autofluorescent lipopigment in neurons and other cell types. Inheritance is autosomal recessive. Three main childhood subtypes are recognized: infantile (Haltia-Santavuori disease; MIM 256743), late infantile (Jansky-Bielschowsky disease; MIM 204500), and juvenile (Spielmeyer-Sjögren-Vogt, or Batten, disease; MIM 204200). The gene loci for the juvenile (CLN3) and infantile (CLN1) types have been mapped to human chromosomes 16p and 1p, respectively, by linkage analysis. Linkage analysis of 25 families segregating for late-infantile NCL has excluded these regions as the site of this disease locus (CLN2). The three childhood subtypes of NCL therefore arise from mutations at distinct loci.     

Batten disease (Spielmeyer-Vogt disease, juvenile onset neuronal ceroid-lipofuscinosis) gene (CLN3) maps to human chromosome 16

The ceroid-lipofuscinoses are a group of inherited neurodegenerative disorders characterized by the accumulation of autofluorescent lipopigment in neurons and other cell types. The underlying biochemical defect is unknown. Batten disease (Spielmeyer-Vogt disease, juvenile onset neuronal ceroid-lipofuscinosis) displays autosomal recessive inheritance. Genetic linkage studies were undertaken to determine the chromosomal location of the Batten disease mutation (CLN3). Following identification of linkage to the haptoglobin locus, linkage analysis has been carried out in 42 families by using DNA markers for loci on the long arm of human chromosome 16. The maximal lod score between Batten disease and the locus D16S148 calculated for combined sexes is 6.05 at a recombination fraction theta = 0.00. Multilocus analysis using five loci indicated the most likely order to be HP-D16S151-D16S150-CLN3-D16S148-D16S147. The maximal location score for CLN3 was 48 (equivalent to a lod score of 10.4) in that interval within this fixed marker map.     

A gene for cleidocranial dysplasia maps to the short arm of chromosome 6.

Cleidocranial dysplasia (CCD) is an autosomal dominant generalized bone dysplasia characterized by mild-to-moderate short stature, clavicular aplasia or hypoplasia, supernumerary and ectopic teeth, delayed eruption of secondary teeth, a characteristic craniofacial appearance, and a variety of other skeletal anomalies. We have performed linkage studies in five families with CCD, with 24 affected and 20 unaffected individuals, using microsatellite markers spanning two candidate regions on chromosomes 8q and 6. The strongest support for linkage was with chromosome 6p microsatellite marker D6S282 with a two-point lod score of 4.84 (theta = .03). Furthermore, the multipoint lod score was 5.70 in the interval between D6S282 and D6S291. These data show that the gene for autosomal dominant CCD is located within a 19-cM interval on the short arm of chromosome 6, between D6S282 and D6S291.     

Linkage disequilibrium between the juvenile neuronal ceroid lipofuscinosis gene and marker loci on chromosome 16p 12.1.

The neuronal ceroid lipofuscinoses (NCL; Batten disease) are a collection of autosomal recessive disorders characterized by the accumulation of autofluorescent lipopigments in the neurons and other cell types. Clinically, these disorders are characterized by progressive encephalopathy, loss of vision, and seizures. CLN3, the gene responsible for juvenile NCL, has been mapped to a 15-cM region flanked by the marker loci D16S148 and D16S150 on human chromosome 16. CLN2, the gene causing the late-infantile form of NCL (LNCL), is not yet mapped. We have used highly informative dinucleotide repeat markers mapping between D16S148 and D16S150 to refine the localization of CLN3 and to test for linkage to CLN2. We find significant linkage disequilibrium between CLN3 and the dinucleotide repeat marker loci D16S288 (chi 2(7) = 46.5, P < .005), D16S298 (chi 2(6) = 36.6, P < .005), and D16S299 (chi 2(7) = 73.8, P < .005), and also a novel RFLP marker at the D16S272 locus (chi 2(1) = 5.7, P = .02). These markers all map to 16p12.1. The D16S298/D16S299 haplotype "5/4" is highly overrepresented, accounting for 54% of CLN3 chromosomes as compared with 8% of control chromosomes (chi 2 = 117, df = 1, P < .001). Examination of the haplotypes suggests that the CLN3 locus can be narrowed to the region immediately surrounding these markers in 16p12.1. Analysis of D16S299 in our LNCL pedigrees supports our previous finding that CLN3 and CLN2 are different genetic loci. This study also indicates that dinucleotide repeat markers play a valuable role in disequilibrium studies.     

Tyrosine hydroxylase maps to the short arm of chromosome 11 proximal to the insulin and HRAS1 loci

Tyrosine hydroxylase (TH) is the rate-limiting enzyme for catecholamine biosynthesis and a candidate gene for manic-depressive illness. The TH locus was typed for a BglII RFLP using a cDNA clone Ty7 in four large kindreds. Pairwise analyses and multipoint analyses were carried out to map the TH locus more precisely in the region of the linked markers: D11S12, INS, and HRAS1 on 11p. Results confirm the close linkage between TH with these previously mapped markers and support a most likely ordering which places TH on the side of INS where the centromere lies.     

A missense mutation (c.184C>T) in ovine CLN6 causes neuronal ceroid lipofuscinosis in Merino sheep whereas affected South Hampshire sheep have reduced levels of CLN6 mRNA

The neuronal ceroid lipofuscinoses (NCLs, Batten disease) are a group of fatal recessively inherited neurodegenerative diseases of humans and animals characterised by common clinical signs and pathology. These include blindness, ataxia, dementia, behavioural changes, seizures, brain and retinal atrophy and accumulation of fluorescent lysosome derived organelles in most cells. A number of different variants have been suggested and seven different causative genes identified in humans (CLN1, CLN2, CLN3, CLN5, CLN6, CLN8 and CTSD). Animal models have played a central role in the investigation of this group of diseases and are extremely valuable for developing a better understanding of the disease mechanisms and possible therapeutic approaches. Ovine models include flocks of affected New Zealand South Hampshires and Borderdales and Australian Merinos. The ovine CLN6 gene has been sequenced in a representative selection of these sheep. These investigations unveiled the mutation responsible for the disease in Merino sheep (c.184C>T; p.Arg62Cys) and three common ovine allelic variants (c.56A>G, c.822G>A and c.933_934insCT). Linkage analysis established that CLN6 is the gene most likely to cause NCL in affected South Hampshire sheep, which do not have the c.184C>T mutation but show reduced expression of CLN6 mRNA in a range of tissues as determined by real-time PCR. Lack of linkage precludes CLN6 as a candidate for NCL in Borderdale sheep.     

Use of model organisms for the study of neuronal ceroid lipofuscinosis

Neuronal ceroid lipofuscinoses are a group of fatal progressive neurodegenerative diseases predominantly affecting children. Identification of mutations that cause neuronal ceroid lipofuscinosis, and subsequent functional and pathological studies of the affected genes, underpins efforts to investigate disease mechanisms and identify and test potential therapeutic strategies. These functional studies and pre-clinical trials necessitate the use of model organisms in addition to cell and tissue culture models as they enable the study of protein function within a complex organ such as the brain and the testing of therapies on a whole organism. To this end, a large number of disease models and genetic tools have been identified or created in a variety of model organisms. In this review, we will discuss the ethical issues associated with experiments using model organisms, the factors underlying the choice of model organism, the disease models and genetic tools available, and the contributions of those disease models and tools to neuronal ceroid lipofuscinosis research. This article is part of a Special Issue entitled: The Neuronal Ceroid Lipofuscinoses or Batten Disease.     

Current therapies for the soluble lysosomal forms of neuronal ceroid lipofuscinosis

The NCLs (neuronal ceroid lipofuscinoses) are the most common inherited paediatric neurodegenerative disorder. Although genetically distinct, NCLs can be broadly divided into two categories: one in which the mutation results in a defect in a transmembrane protein, and the other where the defect lies in a soluble lysosomal enzyme. A number of therapeutic approaches are applicable to the soluble lysosomal forms of NCL based on the phenomenon of cross-correction, whereby the ubiquitously expressed mannose 6-phosphate/IGF (insulin-like growth factor) II receptor provides an avenue for endocytosis, trafficking and lysosomal processing of extracellularly delivered enzyme. The present review discusses therapeutic utilization of cross-correction by enzyme-replacement therapy, gene therapy and stem cell therapy for the NCLs, along with an overview of the recent progress in translating these treatments into the clinic.     

Integration of the classical and RFLP linkage maps of the short arm of tomato chromosome 1

The classical map of the short arm of chromosome 1 of tomato (Lycopersicon esculentum) has been shown to contain inaccuracies while the RFLP map of this region is known to be generally accurate. Molecular analysis of populations derived from crosses between L. esculentum lines carrying chromosome 1 classical markers and L. pennellii has enabled us to produce an integrated classical and RFLP marker map of this region. New data concerning the linkage relationships between classical markers have also been combined with previous data to produce a new classical map of the short arm of chromosome 1. The orders of the classical markers on these two new maps are in almost complete agreement and are very different to that shown on the previous classical map.