Expression of CLN3 in normal and Batten disease affected sheep

Abstract

The Neuronal Ceroid Lipofuscinosis (NCL, Batten disease) are a group of related hereditary neurodegenerative diseases that afflict children and animals. They are characterised by brain atrophy and the accumulation of a hydrophobic protein within lysosome-derived cytosomes. Biochemical studies on a well characterised ovine model of ceroid lipofuscinosis (OCL) established the nature of the storage material. Subunit c of mitochondrial ATP synthase specifically accumulates in OCL and the human diseases except for the infantile onset form. The gene defective in the ovine disease is different to the recently identified gene for a juvenile form of NCL, CLN3. This gene has been sequenced but nothing is known about the CLN3 protein or its function. We studied CLN3 expression in normal and OCL affected sheep to test whether the two genes are cross-regulated. The sheep cDNA sequence was used to generate a probe for Northern blotting and to verify that the amino acid sequence corresponds to that of synthetic peptides used to raise antibodies. CLN3 Northern blot analysis did not reveal a significant difference in the amount of message being present in brain and liver from control and OCL affected animals. No large differences were apparent on Western blots of brain and liver homogenates. Bands of 40, 50 and 90 kD in liver, or 50 and 62 kD in brain were detected in both control and affected animals. No definite band could be assigned to CLN3 which appears to be a differentially spliced gene. In brain, antiserum raised to a C-terminal peptide detects a 50 kD band that is specifically quenched by the peptide used to raise the antibody. Increased 50 kD brain and 90 kD liver immunostaining to this antiserum in three OCL affected sheep compared to normal is the only indication of cross-regulation between the OCL gene and CLN3. The increased potential CLN3 protein activity may reflect an attempt to compensate for the OCL gene defect. Western blotting of subcellular fractions indicated that the CLN3 protein may reside in a soluble compartment.