DNA and enzyme studies on chorionic villi for use in antenatal diagnosis

A study has been undertaken to determine the efficiency of current methods in providing an adequate amount of chorionic villus DNA for antenatal diagnosis using recombinant DNA techniques or enzyme assay. Chorionic biopsies were obtained from 40 women undergoing elective first trimester termination of pregnancy (8-12 weeks) under general anaesthesia. The villus tissue was isolated from maternal tissue under a dissection microscope and the presence of any remaining contamination was ascertained by conventional histology and immuno-cytochemical examinations. A high level of success was achieved in obtaining a pure fetal sample. In the first 20 samples the DNA yield obtained using the method of Williamson et al [1] was found to be 0.5 +/- 0.5 micrograms/mg wet weight of villus tissue (mean +/- 1 SD). In the subsequent 20 biopsies using a modified procedure, the yield was significantly improved to 1.0 +/- 0.65 (p less than 0.002). A normal range for the enzyme iduronate sulphatase, which is deficient in Hunter's syndrome (mucopolysaccharidosis II), is also reported. It is suggested that as little as 20 mg of chorionic villi may be used to provide sufficient material for a reliable study using recombinant DNA or biochemical methods.