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Summary of research activities

There are an estimated 150 genes on the X-chromosome which are involved in XLMR. Up till date, 82 of those genes have been identified. We want to discover exactly what role these genes, and the ones yet to be identified, play in the development of XLMR.

To this aim, the EURO-MRX has DNA and pedigrees of over 600 XLMR families at its disposal. There are strong clues that the mental handicap in these families are caused by a defect in a gene or genes on the X-chromosome.

Mutation-analysis for 21 of the 82 known genes has been carried out on the DNA of the families. Also, 74 candidate-genes have been tested on a part of the collection of families. This has resulted in the following findings:

  • Almost all known XLMR genes only make a small contribution (<1%) to the development of XLMR
  • Many more families will have to be tested in order to discover the unknown genes

Due to the low mutation frequency, we are now developing diagnostic tools to analyse all genes on the X chromosome in one step.