Molecular approaches to the study of gene expression during human preimplantation development

Understanding of gene expression during the early stages of human development has increased markedly in the last 2 years, as refined and highly sensitive procedures have been developed enabling construction of cDNA libraries from single preimplantation embryos and unfertilized oocytes. The genes identified so far include key regulatory genes such as imprinted genes, transcription factors and cell cycling genes, as well as repetitive sequences, brain transcripts and housekeeping genes. In addition, sequencing of random clones has revealed cDNAs matching known expressed sequence tags in the GenBank and dbEST databases, in addition to novel sequences not currently present in these databases. This article focuses on the various molecular biology techniques applicable to the study of gene expression during human preimplantation development.