Centromeric DNA break in a 10;16 reciprocal translocation associated with trisomy 16 confined placental mosaicism and maternal uniparental disomy forchromosome 16

Stable centromeric breakage in nonacrocentric chromosomes and balanced reci procal translocation mosaicism are both rare events. We studied a family in which the mother had mosaicism for a balanced reciprocal translocation bet ween chromosomes 10 and 16 which was associated with a break in chromosome 16 centromere alpha-satellite DNA {46,XX,t(10;16)(q11.2;q11.1) [29]/46,XX[2 5]}. The derivative chromosome 16 contained only a very small amount of 16 alpha-satellite DNA while the derivative 10 contained all of the 10 alpha-s atellite DNA as well as a large amount of the 16 alpha-satellite DNA. The s ame translocation was present in all cells in her son who was found prenata lly to have trisomy 16 mosaicism (46,XY,t(10;16) (q11.2;q11.1)mat[22]/47,id em,+16[4]). Trisomy 16 cells were subsequently determined to be confined to the placenta. DNA polymorphism analyses in the family demonstrated materna l uniparental disomy for chromosome 16 in the diploid child. The child, at age 7 months, had minor facial anomalies similar to a previously reported c ase of maternal uniparental disomy for chromosome 16. In addition to illust rating several rare events, this family further demonstrated that substanti al deletion of the centromeric alpha-satellite DNA does not impair centrome re function and both mitotic and meiotic stability are retained in such cas es. Am. J. Med. Genet. 80:418-422, 1998. (C) 1998 Wiley-Liss, Inc.