MATERNAL UNIPARENTAL DISOMY FOR CHROMOSOME-14 IN A BOY WITH INTRAUTERINE GROWTH-RETARDATION

Maternal uniparental disomy (UPD) for chromosome 14 [upd(14)mat] may c ause a characteristic phenotype with growth and developmental deficien cy and precocious puberty. We report the case of a Japanese infant wit h an isochromosome 14 [i(14q)] and intrauterine growth retardation (IU GR). The infant is one of triplets comprising a boy (the patient) and two karyotypically normal girls. We analyzed parent-child transmission modes of alleles on the i(14q) at 17 CA-repeat marker loci along the entire length of chromosome 14. Genotypes at 4 proximal and 5 distal l oci on the i(14q) were consistent with maternal isodisomy, whereas tho se at an intervening region indicated maternal heterodisomy. Thus, the derivative chromosome 14 had arisen through a translocation between m aternal homologous chromosomes 14 [t(14;14)(p10;q10)] after at least t wo crossing-over events at the first meiosis. This result also suggest s that there must be maternally imprinted gene(s) on 14q, and that los s of the functionally active, paternally derived allele in the same lo cus may lead to IUGR. Alternatively, IUGR may be an autosomal recessiv e trait. In the latter case, the mother would be a heterozygote and th e putative disease locus would be either at the most proximal or most distal region of 14q.