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

Homozygous CNP Mutation and Neurodegeneration in Weimaraners: Myelin Abnormalities and Accumulation of Lipofuscin-like Inclusions

A progressive neurological disorder was observed in a male neutered Weimaraner. Clinical signs included fecal incontinence, lethargy, moderate paraparesis, proprioceptive pelvic limb ataxia, falling, cognitive decline, incoordination, decreased interest in food, changes in posture, and episodes of trance-like behavior. Neurologic signs were first observed at approximately 4 years, 10 months of age and progressed slowly. Magnetic resonance imaging showed generalized brain atrophy with areas of white matter pathology. Humane euthanasia was elected at 6 years, 7 months of age due to increasing severity of the neurological signs. Autofluorescent intracellular granules were observed in the cerebral and cerebellar cortexes, optic nerve, and cardiac muscle of the affected dog. These abnormal inclusions in the cerebral cortex and cardiac muscle immunolabeled with antibodies to mitochondrial ATP synthase subunit c protein, like that observed in the neuronal ceroid lipofuscinosis group of lysosomal storage diseases. Immunolabeling also demonstrated pronounced neuroinflammation in brain tissues. The ultrastructural appearances of the disease-related inclusion bodies in the brain and optic nerve were quite variable. The ultrastructure and locations of many of the inclusions in the nervous tissues suggested that they were derived, at least in part, from the myelin surrounding axons. The storage bodies in the cardiac muscle were located in mitochondria-rich regions and consisted of parallel arrays of membrane-like components interspersed with electron-dense flocculent material. The disease was characterized by pronounced abnormalities in the myelin of the brain and optic nerve consisting of distinctive areas of ballooning between the layers of myelin. The whole genome sequence generated from the affected dog contained a homozygous G-to-A missense mutation in CNP, which encodes proteins with CNPase enzyme activity and a structural role in myelin. The mutation predicts a Thr42Met amino acid sequence substitution. Genotyping of archived Weimaraner DNA samples identified an additional G > A variant homozygote with a clinical history and brain lesions similar to those of the proband. Of 304 Weimaraners and over 4000 other dogs of various breeds, the proband and the other Weimaraner that exhibited similar signs were the only two that were homozygous for the CNP missense variant. CNPase immunolabeling was widespread in brain tissues from normal dogs but was undetectable in the same tissues from the proband. Based on the clinical history, fluorescence and electron-microscopy, immunohistochemistry, and molecular genetic findings, the late-onset Weimaraner disorder likely results from the missense mutation that results in CNPase deficiency, leading to myelin abnormalities, accumulation of lysosomal storage bodies, and brain atrophy. Similar disorders have been associated with different CNP variants in Dalmatians and in human subjects.

Gait phenotype in Batten disease: A marker of disease progression

BACKGROUND

Gait impairment and its etiologic correlate has not previously been subject of special attention in Batten disease.

METHODS

In the present review, the clinical picture of gait phenotype during Batten disease course accompanied by descriptions of the known concomitant patho-anatomical changes is presented.

RESULTS

In CLN1 a non-rhythmic gait is seen around 1-1½ years of age. Shortly after, postural hypotonia and exaggerated tendon reflexes develop. The disease reaches a burnt-out stage during the third year of age and subsequently the children are almost without voluntary movements. The existing literature indicates that gait phenotype in CLN1 is caused by early involvement of the spinal interneurons followed by impact of the cortex and the cortico-spinal tracts. The earliest walking abnormality in children with CLN2 is a clumsy, ataxic, and spastic gait, which is in accordance with the existing imaging and histologic studies showing early involvement of the cerebellum and the cortico-spinal pathways. In CLN3, a reduction in walking speed is present at the age of 7-8 years. It occurs simultaneously with a reduction in the white matter microstructure and brain connectivity networks. Functional impairment of the basal ganglia contributing to a parkinsonian gait phenotype occurs in the mid-teens. In the late teens and early twenties involvement of the peripheral nerves, neurogenic musculoskeletal atrophy, loss of tendon reflexes and postural control are seen.

CONCLUSION

The progressively impaired gait function in Batten disease is related to timing of damage of distinct areas of the nervous system depending on subtype and is a powerful marker of disease progression.

Genetic modulation of apoptotic pathways fails to alter disease course in tripeptidyl-peptidase 1 deficient mice

Late-infantile neuronal ceroid lipofuscinosis (LINCL) is a fatal, incurable neurodegenerative disease of children caused by the loss of the lysosomal protein tripeptidyl-peptidase 1 (TPP1). Previous studies have suggested that Bcl-2-dependent apoptotic pathways are involved in neuronal cell death in LINCL patients and, as a result, anti-apoptotic treatments that increase Bcl-2 activity have been proposed as a potential therapeutic approach. In this study, we have directly investigated whether targeting anti-apoptotic pathways may be of value in LINCL in a mouse model of this disease that lacks TPP1 and which recapitulates many aspect of the human disease, including a greatly shortened life-span. Our approach was to genetically modify apoptotic pathways and determine the effects of these changes on the severe neurodegenerative phenotype of the LINCL mouse. LINCL mice were generated that either lacked the pro-apoptotic p53 or had increased levels of anti-apoptotic Bcl-2, changes that would exacerbate or ameliorate neuronal death, respectively, should pathways involving these proteins be important. Neither modification affected the shortened life-span of the LINCL mouse. These results suggest that either neuronal death in LINCL does not occur via apoptosis or that it occurs via apoptotic pathways not involving p53 or Bcl-2. Alternatively, pathways involving p53 and/or Bcl-2 may be involved in neuronal death under normal circumstances but may not be the only routes to this end. Importantly, our findings suggest that targeting pathways of cell death involving p53 or Bcl-2 do not represent useful directions for developing effective treatment.

Mechanisms of neurodegeneration in neuronal ceroid-lipofuscinoses

Neuronal ceroid-lipofuscinoses (NCL) are a group of neurodegenerative diseases and autosomal recessive lysosomal storage disorders. We examined the involvement of cell death, oxidative stress, and glutamate excitotoxicity using immunohistochemistry against Bcl-2, Bcl-x, oxidative products to proteins, lipids and DNA, calcium-binding proteins (calbindin-D28K, parvalbumin, calretinin), and glial glutamate transporters (excitatory amino acid transporters 1 and 2), in addition to terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) in the brains from three cases of late infantile form of NCL (LINCL) and one case of juvenile form of NCL (JNCL) to investigate the neurodegenerative mechanisms. In the cerebral and cerebellar cortex, all of three LINCL cases demonstrated neurons with TUNEL-immunoreactive nuclei, whereas the JNCL case did not show TUNEL-immunoreactive nuclei. The coexistence of the nuclear TUNEL-immunoreactivity nuclei and cytoplasmic deposition of 4-hydroxy-2-nonenal-modified protein in the frontal cortex and hypoglossal nucleus may suggest a possible interrelationship between DNA fragmentation and lipid oxidation in LINCL. Additionally, glycoxidation of protein and oxidative stress to DNA seemed to be involved in the cerebellar and cerebral degeneration, respectively. Interneurons immunoreactive for calbindin-D28K and parvalbumin were severely reduced in the cerebral cortex, whereas those for calretinin were comparatively well preserved in LINCL, indicating the possibility of altered GABAergic system. The disturbance of expression of glial glutamate transporters seemed to be heterogeneous and mild. These findings suggest the possibility of new treatments for neurodegeneration in LINCL using antioxidative agents and/or GABAergic medications.

Immunohistological study of globoid cell leukodystrophy

We examined three autopsy cases of globoid cell leukodystrophy (GLD) with different survival, using immunohistochemistry and in situ nick end labeling (ISEL). The white matter lesion was pronounced in the corona radiata, corpus callosum and cerebellar peduncles in three cases, where a spongy state developed, in addition to the neuronal loss in the thalamus, cerebellum and inferior olivary nucleus. Ramified microglia, being immunoreactive for ferritin and HLA-DR alpha, were scattered in the white matter, and some of them also had immunoreactivity for TNF-alpha. Both the small-sized and large-sized globoid cells showed immunoreactivity for ferritin KP-1 and NCAM, while some of the small-sized globoid cells were also immunoreactive for HLA-DR alpha and TNF-alpha. As the survival became longer, the occurrence of the globoid cells decreased, however, they were commonly observed in the corpus callosum and cerebellar peduncle in three cases. T lymphocytes immunoreactive for LCA, UCHL-1 and CD3 were increased around the vessels in the white matter. ISEL stained nuclei of mononuclear cells in the white matter in two cases with short survival, although the cell origin was not verified. ISEL also visualized a few nuclei of the small-sized globoid cells in one case. On the other hand, immunostainings against cell death proteins such as bcl-2 family members and p53 failed to identify any significant changes. These data suggest that the immunological step and to a lesser extent the apoptotic process may partly be involved in the myelin breakdown and glial pathology in GLD, as reported in the twitcher mouse, a murine model of GLD.

Serial MRI findings in the Costa Rican variant of neuronal ceroid-lipofuscinosis

Widespread cerebral atrophy and basal ganglia involvement are highly suggestive imaging features of the variants of late infantile type neuronal ceroid-lipofuscinosis. In the presence of clinical findings indicative of neuronal ceroid-lipofuscinosis, neuroimaging procedures are highly recommended to differentiate the variants from classic late infantile neuronal ceroid-lipofuscinosis. The clinical features and follow-up magnetic resonance imaging studies in a patient with the Costa Rican variant of late infantile neuronal ceroid-lipofuscinosis is presented. These procedures were of the utmost importance to observe the progression of the neurologic ailment and the extent of the cerebral and cerebellar abnormalities.