Neuronal ceroid lipofuscinoses in childhood

Human INCL fibroblasts display abnormal mitochondrial and lysosomal networks and heightened susceptibility to ROS-induced cell death

Infantile Neuronal Ceroid Lipofuscinosis (INCL) is a pediatric neurodegenerative disorder characterized by progressive retinal and central nervous system deterioration during infancy. This lysosomal storage disorder results from a deficiency in the Palmitoyl Protein Thioesterase 1 (PPT1) enzyme—a lysosomal hydrolase which cleaves fatty acid chains such as palmitate from lipid-modified proteins. In the absence of PPT1 activity, these proteins fail to be degraded, leading to the accumulation of autofluorescence storage material in the lysosome. The underlying molecular mechanisms leading to INCL pathology remain poorly understood. A role for oxidative stress has been postulated, yet little evidence has been reported to support this possibility. Here we present a comprehensive cellular characterization of human PPT1-deficient fibroblast cells harboring Met1Ile and Tyr247His compound heterozygous mutations. We detected autofluorescence storage material and observed distinct organellar abnormalities of the lysosomal and mitochondrial structures, which supported previous postulations about the role of ER, mitochondria and oxidative stress in INCL. An increase in the number of lysosomal structures was found in INCL patient fibroblasts, which suggested an upregulation of lysosomal biogenesis, and an association with endoplasmic reticulum stress response. The mitochondrial network also displayed abnormal spherical punctate morphology instead of normal elongated tubules with extensive branching, supporting the involvement of mitochondrial and oxidative stress in INCL cell death. Autofluorescence accumulation and lysosomal pathologies can be mitigated in the presence of conditioned wild type media suggesting that a partial restoration via passive introduction of the enzyme into the cellular environment may be possible. We also demonstrated, for the first time, that human INCL fibroblasts have a heightened susceptibility to exogenous reactive oxygen species (ROS)-induced cell death, which suggested an elevated basal level of endogenous ROS in the mutant cell. Collectively, these findings support the role of intracellular organellar networks in INCL pathology, possibly due to oxidative stress.

Gene correction of the CLN3 c.175G>A variant in patient-derived induced pluripotent stem cells prevents pathological changes in retinal organoids

Background

Mutations in CLN3 cause Batten disease, however non‐syndromic CLN3 disease, characterized by retinal‐specific degeneration, has been also described. Here, we characterized an induced pluripotent stem cell (iPSC)‐derived disease model derived from a patient with non‐syndromic CLN3‐associated retinopathy.

Methods

Patient‐iPSC, carrying the 1 kb‐deletion and c.175G>A variants in CLN3, coisogenic iPSC, in which the c.175G>A variant was corrected, and control iPSC were differentiated into neural retinal organoids (NRO) and cardiomyocytes. CLN3 transcripts were analyzed by Sanger sequencing. Gene expression was characterized by qPCR and western blotting. NRO were characterized by immunostaining and electron microscopy.

Results

Novel CLN3 transcripts were detected in adult human retina and control‐NRO. The major transcript detected in patient‐NRO displayed skipping of exons 2 and 4–9. Accumulation of subunit‐C of mitochondrial ATPase (SCMAS) protein was demonstrated in patient‐derived cells. Photoreceptor progenitor cells in patient‐NRO displayed accumulation of peroxisomes and vacuolization of inner segments. Correction of the c.175G>A variant restored CLN3 mRNA and protein expression and prevented SCMAS and inner segment vacuolization.

Conclusion

Our results demonstrate the expression of novel CLN3 transcripts in human retinal tissues. The c.175G>A variant alters splicing of the CLN3 pre‐mRNA, leading to features consistent with CLN3 deficiency, which were prevented by gene correction.

Spinal manifestations of CLN1 disease start during the early postnatal period

Aim

To understand the progression of CLN1 disease and develop effective therapies we need to characterize early sites of pathology. Therefore, we performed a comprehensive evaluation of the nature and timing of early CLN1 disease pathology in the spinal cord, which appears especially vulnerable, and how this may affect behaviour.

Methods

We measured the spinal volume and neuronal number, and quantified glial activation, lymphocyte infiltration and oligodendrocyte maturation, as well as cytokine profile analysis during the early stages of pathology in Ppt1‐deficient (Ppt1^−/−) mouse spinal cords. We then performed quantitative gait analysis and open‐field behaviour tests to investigate the behavioural correlates during this period.

Results

We detected significant microglial activation in Ppt1^−/− spinal cords at 1 month. This was followed by astrocytosis, selective interneuron loss, altered spinal volumes and oligodendrocyte maturation at 2 months, before significant storage material accumulation and lymphocyte infiltration at 3 months. The same time course was apparent for inflammatory cytokine expression that was altered as early as one month. There was a transient early period at 2 months when Ppt1^−/− mice had a significantly altered gait that resembles the presentation in children with CLN1 disease. This occurred before an anticipated decline in overall locomotor performance across all ages.

Conclusion

These data reveal disease onset 2 months (25% of life‐span) earlier than expected, while spinal maturation is still ongoing. Our multi‐disciplinary data provide new insights into the spatio‐temporal staging of CLN1 pathogenesis during ongoing postnatal maturation, and highlight the need to deliver therapies during the presymptomatic period.

A multimodal approach to identify clinically relevant biomarkers to comprehensively monitor disease progression in a mouse model of pediatric neurodegenerative disease

While research has accelerated the development of new treatments for pediatric neurodegenerative disorders, the ability to demonstrate the long-term efficacy of these therapies has been hindered by the lack of convincing, noninvasive methods for tracking disease progression both in animal models and in human clinical trials. Here, we unveil a new translational platform for tracking disease progression in an animal model of a pediatric neurodegenerative disorder, CLN6-Batten disease. Instead of looking at a handful of parameters or a single "needle in a haystack", we embrace the idea that disease progression, in mice and patients alike, is a diverse phenomenon best characterized by a combination of relevant biomarkers. Thus, we employed a multi-modal quantitative approach where 144 parameters were longitudinally monitored to allow for individual variability. We use a range of noninvasive neuroimaging modalities and kinematic gait analysis, all methods that parallel those commonly used in the clinic, followed by a powerful statistical platform to identify key progressive anatomical and metabolic changes that correlate strongly with the progression of pathological and behavioral deficits. This innovative, highly sensitive platform can be used as a powerful tool for preclinical studies on neurodegenerative diseases, and provides proof-of-principle for use as a potentially translatable tool for clinicians in the future.

Topological Alterations of the Structural Brain Connectivity Network in Children with Juvenile Neuronal Ceroid Lipofuscinosis

BACKGROUND AND PURPOSE

We used diffusion MR imaging to investigate the structural brain connectivity networks in juvenile neuronal ceroid lipofuscinosis, a neurodegenerative lysosomal storage disease of childhood. Although changes in conventional MR imaging are typically not visually apparent in children aged <10 years, we previously found significant microstructural abnormalities by using diffusion MR imaging. Therefore, we hypothesized that the structural connectivity networks would also be affected in the disease.

MATERIALS AND METHODS

We acquired diffusion MR imaging data from 14 children with juvenile neuronal ceroid lipofuscinosis (mean ± SD age, 9.6 ± 3.4 years; 10 boys) and 14 control subjects (mean ± SD age, 11.2 ± 2.3 years; 7 boys). A follow-up MR imaging was performed for 12 of the patients (mean ± SD age, 11.4 ± 3.2 years; 8 boys). We used graph theoretical analysis to investigate the global and local properties of the structural brain connectivity networks reconstructed with constrained spherical deconvolution-based whole-brain probabilistic tractography.

RESULTS

We found significantly increased characteristic path length (P = .003) and decreased degree (P = .003), which indicated decreased network integration and centrality in children with juvenile neuronal ceroid lipofuscinosis. The findings were similar for the follow-up MR imaging, and there were no significant differences between the two acquisitions of the patients. In addition, we found that the disease severity correlated negatively (P < .007) with integration, segregation, centrality, and small-worldness of the networks. Moreover, we found significantly (P < .0003) decreased local efficiency in the left supramarginal gyrus and temporal plane, and decreased strength in the right lingual gyrus.

CONCLUSIONS

We found significant global and local network alterations in juvenile neuronal ceroid lipofuscinosis that correlated with the disease severity and in areas related to the symptomatology.

Global and Widespread Local White Matter Abnormalities in Juvenile Neuronal Ceroid Lipofuscinosis

BACKGROUND AND PURPOSE

Juvenile neuronal ceroid lipofuscinosis is a progressive neurodegenerative lysosomal storage disease of childhood. It manifests with loss of vision, seizures, and loss of cognitive and motor functions leading to premature death. Previous MR imaging studies have reported cerebral and cerebellar atrophy, progressive hippocampal atrophy, thalamic signal intensity alterations, and decreased white matter volume in the corona radiata. However, conventional MR imaging findings are usually normal at younger than 10 years of age. The purpose of our study was to investigate whether diffusion MR imaging could reveal changes in white matter microstructure already present at a younger age.

MATERIALS AND METHODS

We investigated global and local white matter abnormalities in 14 children with juvenile neuronal ceroid lipofuscinosis (mean age, 9.6 ± 3.4 years; 10 boys) and 14 control subjects (mean age, 11.2 ± 2.3 years; 7 boys). Twelve patients underwent follow-up MR imaging after 2 years (mean age, 11.4 ± 3.2 years; 8 boys). We performed a global analysis using 2 approaches: white matter tract skeleton and constrained spherical deconvolution-based whole-brain tractography. Then, we investigated local microstructural abnormalities using Tract-Based Spatial Statistics.

RESULTS

We found globally decreased anisotropy (P = .000001) and increased diffusivity (P = .001) in patients with juvenile neuronal ceroid lipofuscinosis. In addition, we found widespread increased diffusivity and decreased anisotropy in, for example, the corona radiata (P < .001) and posterior thalamic radiation (P < .001). However, we found no differences between the first and second acquisitions.

CONCLUSIONS

The patients with juvenile neuronal ceroid lipofuscinosis exhibited global and local abnormalities in white matter microstructure. Future studies could apply more specific microstructural models and study whether these abnormalities are already present at a younger age.

Further delineation of eye manifestations in homozygous 15q13.3 microdeletions including TRPM1: a differential diagnosis of ceroid lipofuscinosis

The 15q13.3 heterozygous microdeletion is a fairly common microdeletion syndrome with marked clinical variability and incomplete penetrance. The average size of the deletion, which comprises six genes including CHRNA7, is 1.5 Mb. CHRNA7 has been identified as the gene responsible for the neurological phenotype in this microdeletion syndrome. Only seven patients with a homozygous microdeletion that includes at least CHRNA7, and is inherited from both parents have been described in the literature. The aim of this study was to further describe the distinctive eye manifestations from the analysis in the three French patients diagnosed with the classical 1.5 Mb homozygous microdeletion. Patients' ages ranged from 30 months to 9 years, and included one sib pair. They all displayed a remarkably severe identifiable clinical phenotype that included congenital blindness and convulsive encephalopathy with inconstant abnormal movements. The ophthalmological examination revealed a lack of eye tracking, optic nerve pallor, an immature response with increased latencies with no response to the checkerboard stimulations at the visual evoked potential examination, and a distinctive retina dystrophy with a negative electroretinogram in which the "b" wave was smaller than the "a" wave after a dark adapted pupil and bright flash in all patients. Clear genotype-phenotype correlations emerged, showing that this eye phenotype was secondary to homozygous deletion of TRPM1, the gene responsible for autosomal recessive congenital stationary night blindness. The main differential diagnosis is ceroid lipofuscinosis.

In a model of Batten disease, palmitoyl protein thioesterase-1 deficiency is associated with brown adipose tissue and thermoregulation abnormalities

Infantile neuronal ceroid lipofuscinosis (INCL) is a fatal neurodegenerative disorder caused by a deficiency of palmitoyl-protein thioesterase-1 (PPT1). We have previously shown that children with INCL have increased risk of hypothermia during anesthesia and that PPT1-deficiency in mice is associated with disruption of adaptive energy metabolism, downregulation of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), and mitochondrial dysfunction. Here we hypothesized that Ppt1-knockout mice, a well-studied model of INCL that shows many of the neurologic manifestations of the disease, would recapitulate the thermoregulation impairment observed in children with INCL. We also hypothesized that when exposed to cold, Ppt1-knockout mice would be unable to maintain body temperature as in mice thermogenesis requires upregulation of Pgc-1α and uncoupling protein 1 (Ucp-1) in brown adipose tissue. We found that the Ppt1-KO mice had lower basal body temperature as they aged and developed hypothermia during cold exposure. Surprisingly, this inability to maintain body temperature during cold exposure in Ppt1-KO mice was associated with an adequate upregulation of Pgc-1α and Ucp-1 but with lower levels of sympathetic neurotransmitters in brown adipose tissue. In addition, during baseline conditions, brown adipose tissue of Ppt1-KO mice had less vacuolization (lipid droplets) compared to wild-type animals. After cold stress, wild-type animals had significant decreases whereas Ppt1-KO had insignificant changes in lipid droplets compared with baseline measurements, thus suggesting that Ppt1-KO had less lipolysis in response to cold stress. These results uncover a previously unknown phenotype associated with PPT1 deficiency, that of altered thermoregulation, which is associated with impaired lipolysis and neurotransmitter release to brown adipose tissue during cold exposure. These findings suggest that INCL should be added to the list of neurodegenerative diseases that are linked to alterations in peripheral metabolic processes. In addition, extrapolating these findings clinically, impaired thermoregulation and hypothermia are potential risks in patients with INCL.

Infantile neuronal ceroid lipofuscinosis: follow-up on a Spanish series

Infantile neuronal ceroid lipofuscinosis (INCL; NCL1, Haltia-Santavuori disease) is caused by mutations in the CLN1/PPT gene which are associated with an early onset INCL phenotype. The most detailed descriptions of INCL have come from Finland and a few series have been reported from southern European countries. Clinical course and follow-up of six Spanish patients with INCL are reported with the aim of assessing the chronological evolution and severity of this disease. The age at disease onset ranged from 8 to 15 months. Delayed motor skills were the initial symptom when the disease began before 12 months of age, and ataxia was the first sign when the disease began later. Cognitive decline, which is described between 12 and 18 months of age, occurred from 16 to 20 months of age. In our series early stage is characterized by motor impairment, cognitive decline and autistic features. Visual failure may appear simultaneously with the neurological symptoms, leading quickly to blindness. As reported, psychomotor regression appeared between 2 and 3 years of age. Myoclonic jerks occurred after 24 months of age and epilepsy was the last symptom of the disease. We report two novel mutations in a patient without epilepsy to date and describe the features of two siblings homozygous for the V181M (c.541G>A) mutation, associated with the most severe INCL phenotype. The clinical evolution might be helpful to identify patients affected by this rare disease. Early diagnosis is essential in order to provide genetic counselling to affected families. Our series may contribute to the study of the genotype-phenotype INCL correlation in the Mediterranean countries.

Juvenile neuronal ceroid lipofuscinosis: clinical course and genetic studies in Spanish patients

BACKGROUND

Juvenile neuronal ceroid lipofuscinosis (JNCL, NCL3, Batten disease) is usually caused by a 1.02-kb deletion in the CLN3 gene. Mutations in the CLN1 gene may be associated with a variant form of JNCL (vJNCL). We report the clinical course and molecular studies in 24 patients with JNCL collected from 1975 to 2010 with the aim of assessing the natural history of the disorder and phenotype/genotype correlations.

PATIENTS AND METHODS

Patients were classified into the groups of vJNCL with mutations in the CLN1 gene and/or granular osmiophilic deposit (GROD) inclusion bodies (n = 11) and classic JNCL (cJNCL) with mutations in the CLN3 gene and/or fingerprint (FP) profiles (n = 13). Psychomotor impairment included regression of acquired skills, cognitive decline, and clinical manifestations of the disease. We used Kaplan-Meier analyses to estimate the age of onset of psychomotor impairment.

RESULTS

Patients with vJNCL showed learning delay at an earlier age (median 4 years, 95% confidence interval [CI] 3.1-4.8) than those in the cJNCL group (median 8 years, 95% CI 6.2-9.7) (P = 0.001) and regression of acquired skills at a younger age. Patients with vJNCL showed a more severe and progressive clinical course than those with cJNCL. There may be a Gypsy ancestry for V181L missense mutation in the CLN1 gene.

CONCLUSIONS

The rate of disease progression may be useful to diagnose vJNCL or cJNCL, which should be confirmed by molecular studies in CLN1/CLN3 genes. Further studies of genotype/phenotype correlation will be helpful for understanding the pathogenesis of this disease.

Molecular correlates of axonal and synaptic pathology in mouse models of Batten disease

Neuronal ceroid lipofuscinoses (NCLs; Batten disease) are collectively the most frequent autosomal-recessive neurodegenerative disease of childhood, but the underlying cellular and molecular mechanisms remain unclear. Several lines of evidence have highlighted the important role that non-somatic compartments of neurons (axons and synapses) play in the instigation and progression of NCL pathogenesis. Here, we report a progressive breakdown of axons and synapses in the brains of two different mouse models of NCL: Ppt1^−/− model of infantile NCL and Cln6^nclf model of variant late-infantile NCL. Synaptic pathology was evident in the thalamus and cortex of these mice, but occurred much earlier within the thalamus. Quantitative comparisons of expression levels for a subset of proteins previously implicated in regulation of axonal and synaptic vulnerability revealed changes in proteins involved with synaptic function/stability and cell-cycle regulation in both strains of NCL mice. Protein expression changes were present at pre/early-symptomatic stages, occurring in advance of morphologically detectable synaptic or axonal pathology and again displayed regional selectivity, occurring first within the thalamus and only later in the cortex. Although significant differences in individual protein expression profiles existed between the two NCL models studied, 2 of the 15 proteins examined (VDAC1 and Pttg1) displayed robust and significant changes at pre/early-symptomatic time-points in both models. Our study demonstrates that synapses and axons are important early pathological targets in the NCLs and has identified two proteins, VDAC1 and Pttg1, with the potential for use as in vivo biomarkers of pre/early-symptomatic axonal and synaptic vulnerability in the NCLs.

A novel mutation in the MFSD8 gene in late infantile neuronal ceroid lipofuscinosis

Neuronal ceroid lipofuscinoses (NCL) are lysosomal storage disorders and constitute the most common group of progressive neurodegenerative diseases in childhood. Most NCLs are inherited in a recessive manner and are clinically characterised by a variable age at onset, epileptic seizures, psychomotor decline, visual impairment and premature death. To date, eight causative genes have been identified to underlie various clinical forms of NCL. We performed a genome-wide linkage analysis followed by sequencing the recently described NCL gene MFSD8 in three affected and three unaffected members of a consanguineous Egyptian family with an autosomal recessively inherited progressive neurodegenerative disorder. The clinical picture of the patients was compatible with a late infantile NCL (LINCL); however, impairment of the visual system was not a cardinal symptom in the respective family. By linkage analysis, we identified two putative loci on chromosome 1p36.11-p35.1 and 4q28.1-q28.2. The latter locus (4q28.1-q28.2) contained the MFSD8 gene, comprising a novel homozygous missense mutation in exon 5 (c.362a>g /p.Tyr121Cys), which segregated with the disease in the three affected sibs. We describe a novel mutation in the previously identified MFSD8 gene in a family with a common phenotype of LINCL, but no clinical report of vision loss. Our results enlarge the mutational and perhaps the nosological spectrum of one of the recently identified subtypes of NCL, called CLN7.