Differential expression of the embryo/cancer gene ECS A (DPPA 2), the cancer/testis gene BORIS and the pluripotency structural gene OCT 4, in human preimplantation development

Abstract

In this paper, we examine the expression profiles of two new putative pluripotent stem cell genes, the embryo/cancer sequence A gene (ECSA) and the cancer/testis gene Brother Of the Regulator of Imprinted Sites ( BORIS), in human oocytes, preimplantation embryos, primordial germ cells (PGCs) and embryo stem (ES) cells. Their expression profiles are compared with that of the well-known pluripotency gene, OCT 4, using a primer design that avoids amplification of the multiple OCT4 pseudogenes. As expected, OCT 4 is high in human oocytes, down-regulated in early cleavage stages and then expressed de novo in human blastocysts and PGCs. BORIS and ECS A show distinct profiles of expression in that BORIS is predominantly expressed in the early stages of preimplantation development, in oocytes and 4-cell embryos, whereas ECS A is predominantly expressed in the later stages, blastocysts and PGCs. BORIS is not detected in blastocysts, PGCs or other fetal and adult somatic tissue tested. Thus, BORIS and ECS A may be involved in two different aspects of reprogramming in development, viz., in late gametogenesis, and at the time of formation of the ES cells (inner cell mass (ICM) and PGC), respectively. However, in human ES cells, where a deprogrammed stem cell state is stably established in culture, an immunofluoresence study shows that all three genes are co-expressed at the protein level. Thus, following their derivation from ICM cells, ES cells may undergo further transformation in culture to express a number of embryo and germ line stem cell functions, which, in normal development, show different temporal and spatial specificity of expression. © The Author 2008. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.