Chang Li-Jung, Chen Shee-Uan, Tsai Yi-Yi, Hung Chia-Cheng, Fang Mei-Ya, Su Yi-Ning, Yang Yu-Shih
Department of Obstetrics and Gynecology, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan.
Clin Exp Reprod Med. 2011 Sep;38(3):126-34. doi: 10.5653/cerm.2011.38.3.126. Epub 2011 Sep 30.
Preimplantation genetic diagnosis (PGD) is gradually widely used in prevention of gene diseases and chromosomal abnormalities. Much improvement has been achieved in biopsy technique and molecular diagnosis. Blastocyst biopsy can increase diagnostic accuracy and reduce allele dropout. It is cost-effective and currently plays an important role. Whole genome amplification permits subsequent individual detection of multiple gene loci and screening all 23 pairs of chromosomes. For PGD of chromosomal translocation, fluorescence in-situ hybridization (FISH) is traditionally used, but with technical difficulty. Array comparative genomic hybridization (CGH) can detect translocation and 23 pairs of chromosomes that may replace FISH. Single nucleotide polymorphisms array with haplotyping can further distinguish between normal chromosomes and balanced translocation. PGD may shorten time to conceive and reduce miscarriage for patients with chromosomal translocation. PGD has a potential value for mitochondrial diseases. Preimplantation genetic haplotyping has been applied for unknown mutation sites of single gene disease. Preimplantation genetic screening (PGS) using limited FISH probes in the cleavage-stage embryo did not increase live birth rates for patients with advanced maternal age, unexplained recurrent abortions, and repeated implantation failure. Polar body and blastocyst biopsy may circumvent the problem of mosaicism. PGS using blastocyst biopsy and array CGH is encouraging and merit further studies. Cryopreservation of biopsied blastocysts instead of fresh transfer permits sufficient time for transportation and genetic analysis. Cryopreservation of embryos may avoid ovarian hyperstimulation syndrome and possible suboptimal endometrium.
植入前基因诊断(PGD)正逐渐广泛应用于预防基因疾病和染色体异常。活检技术和分子诊断已取得很大进展。囊胚活检可提高诊断准确性并减少等位基因脱失。它具有成本效益,目前发挥着重要作用。全基因组扩增允许随后对多个基因座进行个体检测并筛查所有23对染色体。对于染色体易位的PGD,传统上使用荧光原位杂交(FISH),但技术难度较大。阵列比较基因组杂交(CGH)可以检测易位和可能取代FISH的23对染色体。具有单倍型分型的单核苷酸多态性阵列可以进一步区分正常染色体和平衡易位。PGD可能会缩短染色体易位患者的受孕时间并减少流产。PGD对线粒体疾病具有潜在价值。植入前基因单倍型分型已应用于单基因疾病的未知突变位点。在卵裂期胚胎中使用有限的FISH探针进行植入前基因筛查(PGS)并未提高高龄产妇、不明原因反复流产和反复植入失败患者的活产率。极体和囊胚活检可能会规避嵌合现象的问题。使用囊胚活检和阵列CGH进行PGS令人鼓舞,值得进一步研究。对活检的囊胚进行冷冻保存而非新鲜移植可留出足够时间进行运输和基因分析。胚胎冷冻保存可避免卵巢过度刺激综合征和可能的子宫内膜欠佳。