Participants involved: Nijmegen (responsible), Paris, Leuven, Berlin, Tours.
Collaborating institutes: Lyon.

Objectives

1. to identify novel MRX genes by the identification of causative mutations in the MRX candidate genes
2. providing the tools and establishing the conditions for implementation of proven new MRX genes in the DNA-diagnostic routine

Methodology and study materials

Mutation analysis will be performed in one representative patient from each family of the established cohort (work package 1). MRX candidate genes will emerge from the positional and functional studies described in work packages 2, 3 and 4. Additional (positional) candidates will be selected on basis of their co-localisation with the genetic defect in MRX families, as determined in work package 1, and on basis of the known or predicted role in the CNS.

For the actual mutation analysis oligonucleotide primers will be designed and used for the PCR-amplification of gene exon sequences and their flanking introns. The PCR amplicons will be analysed by direct sequence analysis. Initially, only patients will be tested from those families for which the MRX candidate gene is contained in the linkage interval. All patients from the MRX cohort will be tested upon the identification of causative mutations. For this group of almost 350 samples a mutation pre-screening will be applied, using established methodology such as SSCP, DGGE, and DHPLC. For all sequence variations identified, control experiments will be performed to exclude sequence artefacts and harmless polymorphisms: SNP database analysis, segregation studies, testing of healthy individuals.

An overview of all analyses and their results will be made for integration in the database (work package 1). This registration will be regularly updated.

The novel MRX genes which are proven to be causally involved, will be published in the international literature and in the database. Conditions for the implementation of these new MRX genes in the DNA-diagnostic routine will be communicated with centers offering DNA Diagnostic analyses.