Distribution and development of CLN2 protein, the late-infantile neuronal ceroid lipofuscinosis gene product

Expression of the late-infantile neuronal ceroid lipofuscinosis (LINCL) gene (CLN2) protein was investigated by immunoblotting and immunohistochemistry in human brains and visceral organs of control individuals and of patients with neuronal ceroid lipofuscinosis (NCL). Immunoblotting analyses showed reactivity in the cerebrum, liver, kidney, heart and colon of controls, whereas CLN2 protein was not detected in these organs in a LINCL patient. Immunohistochemistry showed that the reactivity of the protein was ubiquitous in extracerebral organs as well as within the CNS, apparently corresponding to widely distributed deposition of lipopigments in LINCL. The expression of CLN2 protein in the cerebral cortex increased with development, and reached adult level after the age of 2. This development of expression seemed to be related to the onset of LINCL at 2-4 years of age. We confirmed no immunoreactivity in two of three patients with LINCL, who were diagnosed clinicopathologically. One case showing combined ultrastructural morphology of fingerprint profiles and curvilinear bodies had intermediate reactivity, suggesting heterogeneity in clinical LINCL. Evaluation of the immunoreactivity of the CLN2 protein may be useful for characterization of a variant form.