At this point the exploration of other genes on the X chromosome became necessary, a task which was able to be carried out thanks to two research projects initiated by the Basque Foundation for Health Innovation and Research, employing the income obtained from the telemarathon solidarity events of the Basque Public Broadcasting Corporation some years ago and which was channelled into research into limited intellectual disability and rare diseases.
The team led by Isabel Tejada then decided to apply a technique known as CNV (copy number variants), "observing deletions and duplications of the genome not visible with the microscope". To this end, "we used a a technique known as MLPA (Multiplex ligation-dependent probe amplification) involving a number of probes or fragments of the genome we wished to analyse, given that there had been three known similar cases with the common factor of maternal inheritance. To our surprise we spotted a duplication of a very small region, hitherto undescribed, and which contained 7 genes of which only one - the RPS6KA3 is related to mental retardation", pointed out the geneticist.
Nevertheless, mutations in this gene produce another type of syndrome which was not the case in this patient. "This fact made us think that we had something novel in front of us and that, as happens with other syndromes, the duplication of the gene or genes produces a pathological effect opposite to and/or different from isolated deletions or mutations, given that it is not the deficiency of one or various proteins, but their over-expression, that produces the pathological effect".
Finally, the hypothesis was tested "with other, complementary tests, such as CGH (comparative genomic hybridisation) arrays and studies of messenger RNA and protein expression".
|Contact: Oihane Lakar|