The NCLs include eight forms that result from genetic deficiency on genes CLN(1) to CLN(8), respectively: four classic forms with clinical onset at varying ages-infantile (INCL), late-infantile (LINCL), juvenile (JNCL), and adult (ANCL)-and four variants of late-infantile onset-the Finnish variant LINCL (fLINCL), Portuguese variant LINCL (pLINCL), Turkish variant LINCL (tLINCL), and progressive epilepsy with mental retardation (EPMR).
A homozygous mutation in the orthologous mouse gene (Cln8) underlies the phenotype of a naturally occurring NCL model, the motor neuron degeneration mouse (mnd).
Neuropathological findings have shown that EPMR is a new member (CLN8) of the neuronal ceroid lipofuscinosis (NCL) group of neurodegenerative disorders.The CLN8 gene was identified recently.
It displays 82% nucleotide identity with CLN8, conservation of the codon harbouring the human mutation and is localized to the same region as the motor neuron degeneration mouse, mnd, a naturally occurring mouse NCL (ref.4).