Rapid Detection of the Two Most Common CLN2 Mutations Causing Classical Late Infantile Neuronal Ceroid Lipofuscinosis

Abstract

Neuronal ceroid lipofuscinoses (NCLs) are a group of genetically transmitted neurodegenerative disorders characterized clinically by intellectual and motor decline, visual loss, and myoclonic seizures, in most cases preceded by a variable period of apparently normal development. A common pathological feature of all NCLs is the intracellular accumulation of an autofluorescent material resembling ceroid or lipofuscin. Five genes ( CLN1 , CLN2 , CLN3 , CLN5 , and CLN8 ) have been identified that are mutated in different forms of NCL: respectively, infantile NCL (1); late infantile NCL (2)(3); classical juvenile NCL (4)(5)(6); Finnish variant late infantile NCL (7); and the progressive epilepsy with mental retardation (EPMR, also called Northern epilepsy) (8). Adult-onset NCL (CLN4) follows either an autosomal recessive (Kufs disease) or an autosomal dominant (Parry disease) pattern of inheritance and is likely to be linked to different, as yet unknown, gene loci. The classical late infantile and juvenile forms, by far the commonest NCLs reported in different populations, are leading causes of neurodegeneration in childhood and adolescence. More than 30 mutations, scattered along the whole CLN2 gene, have been reported in association with the classical late infantile NCL (cLINCL) phenotype (9)(10). However, studies performed on large groups of cLINCL patients demonstrated that two mutations, 636C→T and T523-1G→C, are particularly common (9)(11). They occur in ∼60% of cLINCL chromosomes, and at least one of these mutations can be identified in >75% of patients (12). We report here (a) successful development of a real-time multiplex fluorescence PCR with two dyes for the rapid detection of these two mutations and (b) genetic analysis of five new cLINCL families from South-Eastern Poland. We obtained DNA samples for genotyping from five previously unreported cLINCL families with 5 cLINCL patients and 18 healthy relatives. Family members gave …