Patient-specific probes for preimplantation genetic diagnosis of structural and numerical aberrations in interphase cells

Purpose: Our purpose was to evaluate the utility of translocation breakpoin t-spanning DNA probes for prenatal genetic diagnosis of structural and nume rical chromosome aberrations in interphase cells. Methods: Breakpoint-spanning translocation probes were isolated from large insert DNA libraries and labeled so that the breakpoint regions were staine d in different colors. Hybridization conditions were optimized using blasto meres biopsied from donated embryos. Probes were then applied to analyze pa tient blastomeres. Results: We prepared translocation breakpoint-specific probes for 18 in vit ro fertilization patients. Here. we describe the preparation of probes for two patients carrying balanced translocations involving chromosome 11 [t(11 ;22)(q23;q11), t(6;11)(p22.1;p15.3)]. The breakpoint cloning procedure coul d be accomplished in about 3-5 weeks. Additional time was needed to optimiz e probes. Application of probes demonstrated numerical as well as structura l abnormalities. Conclusions: Breakpoint-spanning probes allow chromosome analysis in interp hase cells as required for preimplantation genetic diagnosis screening of b lastomeres.