다운증후군에서 유전자의 이상상태 규명과 새로운 산전진단법을 개발하기 위하여 정상인(46,XX, 46,XY)의 혈액 10예, 양수 10예와 다운증후군으로 확진된 환자의 혈액 10예, 양수 2예를 대상으로 염색체 21번의 장완 21과 22에 존재하는 D21S11과 SIOOB의 유전자 정량적 중합효소연쇄반응(q-PCR)법으로 증폭한 다음 DNA band를 densitometer로 분석 비교하여 다음과 같은 결과를 얻는다. 1. D21S11 STR 분석에서는 정상검체 20예 중 5예에서 homogenous single band, 15예에서 heterozygous double band가 나타났으며, 다운증후군 검체 21예에서는 equivalent triple band와 unequivalent double band를 나타내었고 unequivalent double band의 peak 면적비율은 약 2.0 이었으며 이염색체성과 삼염색체성의 분별점이 명확하였다. 2. SIOOB 분석에서는다운증후군 검체 12예중 7예에서 SIOOB와 IGF-1의 양적비율이 1.4-1.6, 5예에서 1.4이하였고, 정상검체에서는 대부분 양적비율 1.0에 가가운 값을 나타냈으며 이염색체성과 삼염색체성의 분별점이 D21S11 STR 분석에 비하여 명확하지 않았다. 따라서 다운증후군의 신속정확한 산전진단에 있어서 정량적 중합효소연쇄반응(q-PCR)이 이용될 수 있으며, 더 나아가서 모체 혈액내 태아세포를 이용한 비침윤적 산전진단과 착상전 유전진단에 이용될 것으로 사료된다.

Objectives: Down syndrome is one of major chromosomal anomalies associated with mental retardation. Because the incidence of Down syndrome increases with the maternal age, a rapid and accurate method for prenatal diagnosis is necessary. Recent progress in molecular biological techniques made it possible to define the loci of chromosome 21 responsible to Down syndrome and various primers for the amplification of these loci were developed. This study was performed to devise and evaluate the method for detecting trisomy 21 by semi-quantitative polymerase chain reaction(PCR) of S-IOOB and small tandem repeat(STR) analysis of D21S11. Study design: PCR was performed with DNA template obtained from 20 normal samples(blood 10, amniotic fluid 10) and 12 trisomic samples(blood 10, amniotic fluid 2) with 32P-labeled D21S11 and SIOOB primers. After the PCR products for D21S11 locus were electrophoresed in 6% urea polyacrylamide gel, followed by the exposure to X-ray film, the densities of signals were recorded by densitometer. Agarose gel(2%) electrophoresis for PCR products for SIOOB and IGF-I was performed and the relative amounts of them were determined by counting radioactivities in the products. Results: Analysis of D21S11 STR showed equivalent triplets in 4 cases and 8 cases of unequivalent doublets(1:2) in trisomy 21 group. Normal group showed singlet in 5 cases and equivalent doublets in 15 cases. In the analysis of SIOOB, the ratio of SIOOB to IGF-I was the normal samples showed the ratio of about 1.0. The D21S11 STR analysis distinguished more clearly between normal and trisomic samples. However, the analysis of SIOOB was less clear in quantitation. These methods gave a result within 24 hours. Conclusion: Prenatal diagnosis of trisomy 21 through STR analysis of D21S11 using PCR is an useful, innovative, accurate and rapid diagnostic method within 24 hours, and it can be used in preimplantation diagnosis.