[Search for 22q11 deletion and linkage study in familial cases of non-syndromic conotruncal defects].
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Conotruncal malformations are one of the major criteria of the Di George syndrome. Nearly 90% of subjects with this syndrome have been shown to have a 22q11 deletion of a part of the long arm of chromosome 22. The authors set out to determine the role of the 22q11 region in the genesis of non-syndromic familial conotruncal malformations. The families were selected on the following criteria: at least 2 members affected; the members had to have a "conotruncal malformation" (truncus arteriosus, tetralogy of Fallot, interruption of the aortic arch,...). Typing with a microsatellite (x) marker localised in the region usually deleted, deletion was searched for in affected and non-affected members. A study of the transmission of the alleles from generation to generation was made with x and three other microsatellite markers (w, y, z) which cover the pericentromeric region of 22q. Six families fulfilling the inclusion criteria were presented. Of the 11 affected members, 9 had no deletion in the region where the microsatellite x is localised. In 2 cases it was not possible to arrive at a formal conclusion at this stage of the study. All individuals of the 6 recruited families were typed with the 4 microsatellites. Computer analysis (Linkage program) of the results obtained showed that the markers w and x were very close to each other (a recombination rate between these two markers theta = 0.001). Linkage analysis seems to infirm the 22q11 region in the genesis of conotruncal malformations (total lodscore-2.74 for x, for theta = 0), at least in the 6 families studied to date.(ABSTRACT TRUNCATED AT 250 WORDS)
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