Pediatric neurodegenerative diseases are a heterogeneous group of diseases that result from specific genetic and biochemical defects. In recent years, studies have revealed a wide spectrum of abnormal cellular functions that include impaired proteolysis, abnormal lipid trafficking, accumulation of lysosomal content, and mitochondrial dysfunction. Within neurons, elaborated degradation pathways such as the ubiquitin-proteasome system and the autophagy-lysosomal pathway are critical for maintaining homeostasis and normal cell function. Recent evidence suggests a pivotal role for autophagy in major adult and pediatric neurodegenerative diseases. We herein review genetic, pathological, and molecular evidence for the emerging link between autophagy dysfunction and lysosomal storage disorders such as Niemann-Pick type C, progressive myoclonic epilepsies such as Lafora disease, and leukodystrophies such as Alexander disease. We also discuss the recent discovery of genetically deranged autophagy in Vici syndrome, a multisystem disorder, and the implications for the role of autophagy in development and disease. Deciphering the exact mechanism by which autophagy contributes to disease pathology may open novel therapeutic avenues to treat neurodegeneration. To this end, an outlook on novel therapeutic approaches targeting autophagy concludes this review. P ediatric neurodegenerative diseases are a heterogeneous group of diseases that result from specific genetic and biochemical defects. Although the age of onset and the clinical course are variable, neurodegenerative disorders of childhood are characterized by progressive neurologic and cognitive dysfunction with loss of speech, vision, hearing, and motor skills, and a frequent association with seizures, feeding difficulties, and failure to thrive. The degenerative process can affect white and gray matter and spreads in a disease-specific manner. Current genetic and biochemical testing and neuroimaging can establish a diagnosis. The outcome for most diseases, however, is still poor, as therapeutic approaches are limited.Accumulation of proteins, polysaccharides, and lipids are common mechanisms shared by major adult-onset neurodegenerative diseases 1-3 and many neurodegenerative diseases of childhood. 4 These conditions are, therefore, often referred to as "storage diseases" or "proteinopathies. " Cells and postmitotic cells such as neurons, in particular, rely on effective cargo targeting, tagging, transportation, and degradation to maintain intracellular homeostasis under normal conditions and metabolic stress. Within this network, autophagy plays an indispensible role by eliminating misfolded and aggregated proteins, lipids, saccharides, and damaged organelles. Recent evidence suggests that autophagy is dysregulated in a number of pediatric neurodegenerative and metabolic diseases.
AUTOPHAGY: AN OVERVIEWAutophagy describes intracellular pathways that converge into degradation of target material in lysosomes. 5 The route of cargo delivery to the lysosome distinguishes th...