How many genes cause Batten disease?
In the early 1990s it was thought that there were four main types of NCL that began in infancy (between 6-18 months), late infancy (2-4 years), at a juvenile age (6-10 years) or in adulthood. Since it was clear from the inheritance pattern that the NCLs were genetic diseases caused by the presence of two faulty copies of a gene, it was thought that there were therefore four genes that could cause NCL. These were called CLN1 (causing infantile NCL), CLN2 (causing late infantile NCL), CLN3 (causing juvenile NCL) and CLN4 (causing adult NCL,). By comparing the DNA from families with the same type of NCL, it is possible to pinpoint the position on the chromosome of the faulty gene. This is a process called genetic mapping. From this it is then possible to identify the gene. In 1995 the first genes that cause NCL were identified. Since then using this and other scientific methods, more NCL genes have been identified. During this work it became clear that more than four genes cause NCL. By 2
