IN SITU HYBRIDIZATION IN PRENATAL DIAGNOSIS

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The goal of this project is to develop significantly improved automated techniques for detecting the most commonly occurring cytogenetic abnormalities in interphase cells obtained by amniocentesis or chorionic villus sampling (CVS). Using DNA probes on interphase cells avoids the culturing required from routine cytogenetic analysis. This can reduce the time and cost of prenatal diagnosis and permit extension of the test to a larger segment of the at-risk population. Such automation will be particularly important when fetal cells can be isolated from maternal blood samples. This would eliminate the risk associated with amniocentesis or CVS and extend fetal aneuploidy screening to virtually all pregnancies. We will fluorescent DNA probe labeling and automated image analysis to count chromosomes 13, 18, 21, X, and Y in interphase cells. We will use (1) a unique new automated microscope and (2) 4-chip CCD camera with recently developed algorithms for (3) correcting digitized color images for spectral overlap, and (4) creating unbiased estimates of dot count proportions, along with (5) new methods for thick specimen imaging and for locating the cell boundary. The five chromosomes mentioned account for the great majority of viable aneuploidies observed at amniocentesis or CVS. Rapid aneuploidy screening and sex determination will also assist diagnosis of newborns with multiple congenital anomalies or ambiguous genitalia. Interphase cell analysis by in situ hybridization could provide a diagnosis is under 24 hours, compared to 48-72 hours for conventional cytogenetics done on peripheral blood and 10-14 days for amniocentesis or CVS. PROPOSED COMMERCIAL APPLICATION: As soon as the techniques are developed and qualified for routine application, they will be incorporated into PSII's PowerGene product line of cytogenetics automation equipment, both in new systems and as an upgrade to existing systems already in use in cytogenetics labs.