MATERNAL UNIPARENTAL DISOMY-22 HAS NO IMPACT ON THE PHENOTYPE

A 25-year-old normal healthy male was karyotyped because five of his w ife's pregnancies terminated in spontaneous abortions at 6-14 wk of ge station. Cytogenetic investigation disclosed a de novo balanced Robert sonian t(22q;22q) translocation. Molecular studies revealed maternal o nly inheritance for chromosome 22 markers. Reduction to homozygosity f or all informative markers indicates that the rearranged chromosome is an isochromosome derived from one of the maternal chromosomes 22. Exc ept for the possibility of homozygosity for recessive mutations, mater nal uniparental disomy 22 does not seem to have an adverse impact on t he phenotype, apart from causing reproductive failure. It can be concl uded that no maternally imprinted genes with major effect map to chrom osome 22.