Micromanipulation of gametes and embryos: Biopsy of a blastomere from an 8-cell human embryo.

Abstract

The preimplantation diagnosis of genetic disease in preimplantation human embryos was introduced several years ago. It involves removing one or more cells from a cleaving embryo or a blastocyst, and then assessing the isolated cells for evidence of chromosomal anomalies or genetic disease, usually by means of fluorescence in-situ hybridization (FISH), the polymerase chain reaction (PCR) and variants of it. The whole diagnostic procedure can be completed within one day, and correctly diagnosed embryos then replaced in the mother’s uterus. The number of correctly-diagnosed children is now accumulating as more clinics introduce this procedure into their practice. Details of PCR and FISH can be found in various publications (e.g. Delhanty and Handyside,1995). One form of operation is to remove a single blastomere from an 8-cell embryo, and this is the procedure shown in this video. This procedure is demonstrated on two approximately 8-cell human embryos growing in vitro. A series of steps are involved in the process. The initial step is to make a hole in the zona pellucida, and so permit the passage of pipettes through this investment. Access is thus gained to the enclosed embryo. Two examples are shown on this video. The first example illustrates a standard operation, from the drilling of the zona pellucida to the gentle loosening and withdrawal of a single blastomere. The second example is concerned with the problems arising when the first blastomere is damaged during the procedure, and it becomes essential to biopsy a second blastomere.