Recent advances in the molecular genetics of the neuronal ceroid lipofuscinoses

Murine cathepsin F deficiency causes neuronal lipofuscinosis and late-onset neurological disease

Cathepsin F (cat F) is a widely expressed lysosomal cysteine protease whose in vivo role is unknown. To address this issue, mice deficient in cat F were generated via homologous recombination. Although cat F-/- mice appeared healthy and reproduced normally, they developed progressive hind leg weakness and decline in motor coordination at 12 to 16 months of age, followed by significant weight loss and death within 6 months. cat F was found to be expressed throughout the central nervous system (CNS). cat F-/- neurons accumulated eosinophilic granules that had features typical of lysosomal lipofuscin by electron microscopy. Large amounts of autofluorescent lipofuscin, characteristic of the neurodegenerative disease neuronal ceroid lipofuscinosis (NCL), accumulated throughout the CNS but not in visceral organs, beginning as early as 6 weeks of age. Pronounced gliosis, an indicator of neuronal stress and neurodegeneration, was also apparent in older cat F-/- mice. cat F is the only cysteine cathepsin whose inactivation alone causes a lysosomal storage defect and progressive neurological features in mice. The late onset suggests that this gene may be a candidate for adult-onset NCL.

Neuronal ceroid lipofuscinoses: a clinical and morphological study of 17 patients from southern Brazil

The neuronal ceroid lipofuscinoses (NCL) are a group of inherited progressive neurodegenerative disorders with presentation from infancy to adulthood. Three main childhood forms can be established on the basis of age of onset, clinical course, and ultrastructural morphology: infantile (INCL), late infantile (LINCL), and juvenile (JNCL). Several variant subtypes have been described. Genetic and biochemical analysis are helping to better understand, diagnose and classify these disorders. We report on clinical, neurophysiological, neuroradiological, and morphological data from 17 patients with different forms (infantile, late infantile, and juvenile ) of neuronal ceroid lipofuscinoses (NCL) evaluated at Hospital de Clínicas de Porto Alegre, Southern Brazil, during 6 years (1992-1997). Seven cases were infantile; 5 were late infantile; and 5 were juvenile NCL. Gender ratio was male:female, 11:6. Age at presentation varied from 2-24 months for INCL; 2,5 to 5 years for LINCL; and 4-10 years for the JNCL cases. Seizures (6 patients) and psychomotor retardation (1 patient) were the initial symptoms in the INCL group. All the patients in the group of LINCL had the usual findings. JNCL patients manifested different initial symptoms, although tending to follow a similar clinical picture within familial cases. Epidemiological data on the prevalence of NCLs in Brazil are not available, we expect this series of cases to contribute to further research in our population.

The neuronal ceroid-lipofuscinoses (Batten disease): a new class of lysosomal storage diseases

The neuronal ceroid-lipofuscinoses (Batten disease) are a group of severe neurodegenerative disorders characterized clinically by visual loss, seizures and psychomotor degeneration, and pathologically by loss of neurons and lysosomal accumulation of autofluorescent storage material resembling ageing pigment. To date, eight genetic loci have been identified (CLN1-8). Four CLN genes have been isolated (CLN1, CLN2, CLN3 and CLN5) and their gene products have been characterized. CLN1 is a lysosomal palmitoyl-protein thioesterase (PPT) and CLN2 is a lysosomal pepstatin-insensitive peptidase. CLN3 and CLN5 are proteins with multiple membrane-spanning regions and have no homologies to other proteins that would suggest their function. The CLN3 protein is associated with lysosomal membranes and the intracellular location of the CLN5 protein is unknown. Therefore, there is ample evidence that the neuronal ceroid-lipofuscinoses represent a new class of lysosomal storage disorders.

A murine model for juvenile NCL: gene targeting of mouse Cln3

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.

Normal ascorbic acid in cerebrospinal fluid of patients with infantile neuronal ceroid-lipofuscinosis

Neuronal ceroid-lipofuscinoses (NCL) are a group of neurodegenerative disorders. There is much evidence for a role of peroxidation processes in the pathogenesis of NCL, although this would certainly be indirect. Reduced total antioxidant activity of cerebrospinal fluid (CSF) has been reported in NCL. Since ascorbic acid represents a major antioxidant in CSF, we have now determined this parameter in CSF of two patients with the infantile form of NCL (Santavuori-Haltia disease). However, the ascorbic acid values obtained (103.6 and 181.3 microM) are comparable with control values from the literature as well as with those measured in groups of children with neurologic/psychiatric diseases other than NCL (mean +/- standard deviation: 137.1+/-41.3 microM), with suspected (but excluded) meningitis (124.1+/-34.0 microM) and acute lymphoblastic leukemia (131.7+/-17.0 microM). Our results indicate that CSF ascorbic acid concentrations are not affected by peroxidation processes in infantile NCL, but reveal a sharply decreased ascorbic acid concentration in one of the non-NCL patients, possibly associated with his convulsions and/or his anticonvulsant therapy.

Pathological study on sibling autopsy cases of the late infantile form of neuronal ceroid lipofuscinosis

We report autopsy cases of two brothers with the late infantile form of neuronal ceroid lipofuscinosis (LINCL) and examine apoptotic cell death in autopsied brains. Both patients showed psychomotor developmental delay, cerebellar ataxia, convulsions, visual disturbance and myoclonus, and they became bedridden around the age of 6-7 years. Macular changes, mimicking cherry-red spots, were observed on funduscopy, but conjunctival biopsy failed to disclose storage materials. In these cases, the autopsies demonstrated severe atrophy with neuronal loss and gliosis throughout the brain and spinal cord, except the hypothalamic neurons and motor neurons in the brain-stem and spinal cord, and autofluorescent lipofuscin-like materials of two types, fine granular deposits and coarse round bodies, were stored in the remaining neurons and glial cells, and in the epithelial cells of various visceral organs. Immunostaining for mitochondrial subunit C visualized the fine granular deposits but not the coarse round bodies. The nuclei of neurons and glia cells were stained by in situ nick end labeling, which was more pronounced in the younger case, although the expression of both bcl-2 and bcl-x was not significantly altered in these cases. It is suggested that immunohistochemistry for subunit C may be useful for diagnosis of NCL, and further investigations are necessary to clarify the relationship between LINCL and apoptosis, especially in severely affected cases.

Batten disease: four genes and still counting

The neuronal ceroid lipofuscinoses (NCLs, also known as Batten disease) are the most common childhood neurodegenerative disease. They are a group of inherited neurodegenerative disorders characterized by the accumulation of autofluorescent storage material in many cell types. Clinical features include seizures, psychomotor deterioration, and blindness, the ages and order of onset of which differ for each NCL type. An increasing number of subtypes caused by mutations in different genes are now recognized. With the advent of molecular genetics the basic genetic defect underlying each NCL phenotype is being determined, thus shedding light on the molecular basis of the NCLs and opening the way for the development of effective treatment. Four genes have been identified to date. The function of two of these is known and suggests that the primary defect in the NCLs lies in lysosomal proteolysis, the first example of this type of disease. However, since the function of the other two genes remains elusive, and at least four more genes remain to be identified, the molecular basis underlying the NCLs may be more complex than originally predicted.

Neuronal ceroid lipofuscinosis in the Czech Republic: analysis of 57 cases. Report of the 'Prague NCL group'

A series of 57 patients (from 51 families) with neuronal ceroid lipofuscinosis (NCL) has been diagnosed during the last 25 years. Using clinical and electrophysiological criteria together with results of ultrastructural, histochemical, immunohistochemical and neuropathological analyses it has been possible to classify the following NCL types. Two cases were of the infantile type (CLN1), one case of the juvenile (CLN3) type and one case of the adult (CLN4) type. The bulk of the series was represented by 26 cases of the late infantile (CLN2) type and by 27 cases of the early juvenile (CLN6) type (also called non-Finnish variant late infantile, or Lake-Cavanagh). Besides the infantile form, microcephaly was a relatively frequent finding (nine cases) in the late infantile and early juvenile NCLs. In more than half of the late infantile and early juvenile cases there was a significant reduction of the nerve conduction velocity. The early juvenile CLN6 type was found to have a relatively high incidence in the Romany population (12 cases in nine families). Incidence of NCL in the Czech republic is estimated to be 1.3:100,000.