Using BAC clones to characterize unbalanced chromosome abnormalities in interphase cells.

Area of Science:

• Genetics
• Reproductive Biology
• Molecular Diagnostics

Background:

• Balanced translocations in carriers can cause infertility and recurrent miscarriages due to embryonic dysfunction.
• Genomic activation during preimplantation development is particularly sensitive to chromosomal abnormalities.
• Preimplantation genetic diagnosis (PGD) is crucial for carriers to select chromosomally normal embryos.

Purpose of the Study:

• To design patient-specific DNA hybridization probes for preimplantation diagnosis of chromosome translocations.
• To enable the selection of chromosomally normal embryos from balanced or unbalanced interphase cells.
• To develop an efficient method for detecting structural chromosomal abnormalities in carrier patients.

Main Methods:

• Utilized bacterial artificial chromosome (BAC)/PAC clones flanking or spanning chromosomal breakpoints.
• Optimized probe design and hybridization conditions using normal and carrier cells.
• Tested breakpoint-spanning BAC DNA probes on interphase cells with known karyotypes.

Main Results:

• Developed patient-specific probes for detecting balanced translocations.
• Achieved high detection rates: 86% for unbalanced, 81% for normal, and 84% for balanced cells.
• Successfully identified cells with structural abnormalities using interphase FISH.

Conclusions:

• Demonstrated the efficacy of breakpoint-spanning BAC probes for detecting chromosomal translocations in interphase cells.
• Validated a novel approach for preconception and preimplantation genetic diagnosis in translocation carriers.
• This method offers a promising tool for improving reproductive outcomes in individuals with chromosomal rearrangements.