McCauley Tod C, Mazza M R, Didion Brad A, Mao J, Wu G, Coppola G, Coppola G F, Di Berardino D, Day Billy N
Department of Animal Sciences, University of Missouri, 159 ASRC, Columbia, MO 65211, USA.
Theriogenology. 2003 Nov;60(8):1569-80. doi: 10.1016/s0093-691x(03)00172-9.
A cytogenetic study was undertaken to quantify, by chromosomal karyotyping, the incidence and type of chromosomal abnormalities present in Day-6 in vitro-produced (IVP) porcine embryos. Morphologically normal Day-6 blastocysts (n=318) were fixed and grouped into six classes according to the number of total cells (from < or =20 to 61-70). Of 248 embryos suitable for analysis, 97 (39.1%) displayed chromosomal abnormalities. The abnormalities included haploidy (9.3%), polyploidy (71.1%) and mixoploidy (19.6%). Within polyploid embryos, triploidy and tetraploidy showed the highest incidence (56.5 and 27.5%, respectively); among mixoploid embryos, diploid-triploid embryos (2n/3n) were prevalent (36.8%). Overall, the mean cell number was 34.3 +/- 12.1 and the mitotic index was 8.6 +/- 6.1. Chromosomally abnormal embryos had fewer (P<0.01) total cells compared to normal (2n) embryos (31.8 +/- 1.3 versus 35.9 +/- 1.0). In addition, the incidence of polyploidy decreased as the number of cells increased, while that of mixoploidy did not differ. These data indicate that polyploidy affects a large percentage of IVP porcine embryos capable of developing to blastocysts and the incidence of chromosomal abnormalities is much higher than that reported previously in in vivo embryos in this species. Given the ability of morphologically normal embryos with an abnormal chromosome complement to undergo preimplantation development in vitro, and the inability to identify blastocysts with abnormal karyotype without cytogenetic analysis, careful consideration should be given to factors affecting ploidy of IVP embryos, especially the incidence of polyspermic fertilization, when evaluating criteria of a porcine in vitro embryo production scheme.
开展了一项细胞遗传学研究，通过染色体核型分析对体外生产（IVP）的第6天猪胚胎中存在的染色体异常的发生率和类型进行量化。将形态正常的第6天囊胚（n = 318）固定，并根据总细胞数（从≤20到61 - 70）分为六类。在248个适合分析的胚胎中，97个（39.1%）显示出染色体异常。异常包括单倍体（9.3%）、多倍体（71.1%）和混倍体（19.6%）。在多倍体胚胎中，三倍体和四倍体的发生率最高（分别为56.5%和27.5%）；在混倍体胚胎中，二倍体 - 三倍体胚胎（2n/3n）最为普遍（36.8%）。总体而言，平均细胞数为34.3±12.1，有丝分裂指数为8.6±6.1。与正常（2n）胚胎相比，染色体异常的胚胎总细胞数更少（P<0.01）（31.8±1.3对35.9±1.0）。此外，多倍体的发生率随着细胞数的增加而降低，而混倍体的发生率则没有差异。这些数据表明，多倍体影响了很大比例的能够发育到囊胚阶段的体外生产猪胚胎，并且染色体异常的发生率远高于该物种先前报道的体内胚胎。鉴于染色体组成异常但形态正常的胚胎能够在体外进行植入前发育，并且在没有细胞遗传学分析的情况下无法识别核型异常的囊胚，在评估猪体外胚胎生产方案的标准时，应仔细考虑影响体外生产胚胎倍性的因素，尤其是多精受精的发生率。
