The neuronal ceroid- lipofuscinoses (NCL) are a group of inherited brain disorders, characterized by the accumulation in neurons, and in many other cell types, of autofluorescent cytoplasmic deposits. Three childhood forms of NCL are distinguished, all showing progressive intellectual and motor deterioration, loss of vision and premature death.In the most severe form of NCL, infantile NCL (INCL), storage of the autofluorescent material is associated with a rapid and almost total loss of cerebral and cerebellar cortical neurons. The primary biochemical defect is so- far unknown in all forms of NCL. However, accumulation of subunit c of mitochondrial ATP synthase, a very hydrophobic protein, has been found in most other forms of NCL but not in INCL. These investigators have recently shown that the storage cytosomes in INCL also largely consist of small very hydrophobic proteins, identified as sphingolipid activator proteins (SAPs) (saposins) A and D, involved in the degradation of glycosphingolipids. In addition, there is modest accumulation of lipids. The working hypothesis is that there is a defect in a degradative pathway, either in the degradation of hydrophobic proteins or glycospbingolipids. In order to substantiate this concept, it is proposed to: 1) To study the structure and processing of SAPs in INCL patients and normal controls. These studies will include detailed characterization of the stored SAps by protein chemical and immunological methods, a search for possible posttranslational modifications, and analysis of the processing of the SAP precursor protein in cultured INCL fibroblasts; 2) to study the degradation of lipids in INCL, including identification of the accumulating lipids using thin layer chromatography, gas-liquid chromatography and nuclear magnetic resonance spectroscopy, as well as analysis of the activities of lysosomal hydrolases involved in glycosphingolipid degradation; 3) to compare the different forms of human and animal NCL using the antiserum raised against purified INCL storage bodies, which this group developed; and 4) to study the pathogenesis of INCL using our new ovine model at the early stages of the disease. Particular attention will be paid to possible exploitation of the findings for early diagnosis, heterozygote detection and therapy.
