Relationship between homozygosity at the dopamine D3 receptor gene and schizophrenia

A 25-year-old normal healthy male was karyotyped because five of his wife's pregnancies terminated in spontaneous abortions at 6-14 wk of gestation. Cytogenetic investigation disclosed a de novo balanced Robertsonian t(22q;22q) translocation. Molecular studies revealed maternal only inheritance for chromosome 22 markers. Reduction to homozygosity for all informative markers indicates that the rearranged chromosome is an isochromosome derived from one of the maternal chromosomes 22. Except for the possibility of homozygosity for recessive mutations, maternal uniparental disomy 22 does not seem to have an adverse impact on the phenotype, apart from causing reproductive failure. It can be concluded that no maternally imprinted genes with major effect map to chromosome 22.