A FISHstudy ofchromosome fusion intheICF syndrome: involvement ofparacentric heterochromatin butnotofthecentromeres themselves

We haveuseddoublefluorescence insitu hybridisation tostudytheinvolvement of centromeresand paracentromeric heterochromatin inthechromosomeabnormalities seenintheICFsyndrome. To detectcentromeres, we useda probe whichlabelled alphoid satellite DNA,and fortheparacentromeric heterochromatin a probeforclassical satellite II.Our results showthatitisalways theparacentromeric heterochromatin oftherelevant chromosomes thatbecomesdecondensed in thissyndromeand whichfusesto produce multiradial configurations. However,thecentromeric regions, identified bytheir content ofalphoid satellite DNA, appearnevertobecomedecondensed and alwaysremainoutsidetheregions of chromosomefusion inthemultiradials. (U7Med Genet1998;35:833-835)