Detailed characterization of 12 supernumerary ring chromosomes using micro-FISH and search for uniparental disomy

Twelve patients with varying degrees of mosaicism for a supernumerary ring chromosome were studied, The ring chromosomes were characterized using micr odissection in combination with degenerate nucleotide-primed polymerase cha in reaction (PCR) and reverse painting (micro-FISH), This method made it po ssible to determine the chromosomal origin of the ring chromosomes in detai l, and thus to compare the phenotypes of similar cases. Eleven of the marke r chromosomes were derived from the most proximal part of 1p, 3p, 3q, 5p, 7 q, 8p, 8q, 9p, 10p and 20p, One marker chromosome had a complex origin, inc luding the proximal and the most distal part of 20q, Eight of the families were also investigated for uniparental disomy (UPD) using microsatellite an alysis. One case with maternal UPD 9 was found in a child with a ring chrom osome derived from chromosome 9, r(9)(p10p12), (C) 2001 Wiley-Liss, Inc.