Transcriptional regulation of the human pre-implantation embryo

Millions of couples worldwide have difficulties in conceiving a child. These couples, affected by infertility, suffer from symptoms of stress. The causes of infertility are largely unknown and current available treatment, in vitro fertilization has moderate success rates. The in vitro fertilization covers pre-implantation stage of the human embryo development. Better understanding of the molecular mechanisms in the early development might help to improve the in vitro fertilization methods. Much of the knowledge on early development has been gained from model organisms: nematode, fruit fly, zebrafish and mouse. Mouse is a commonly used model organism for mammalian pre-implantation development. Global gene expression studies have been performed on mouse and human. Overall, gene expression changes seem to be similar in principle between the organisms. However, the expression of the first transcribed genes in the early development may not be as conserved between species as other genes expressed later in development. Therefore, human pre-implantation development should also be studied on human material for better translation of the results. Genes with a dynamic expression profile in human pre-implantation development were identified in Paper I. Various criteria such as conservation, expression profile in mouse, relevance in cancer and novelty were applied to choose seventy genes of potential importance in human early development. Expression of those genes was studied in mouse and compared with human orthologues. The results showed differences in the expression profiles between human and mouse. Paper II found novel regulatory elements and potentially important transcription factors from human early development by single-cell RNA sequencing. About 350 of oocytes and blastomeres from early embryos were studied, the promoters of activated genes were analyzed, and many PRD-like homeodomain genes with first-time evidence of expression were cloned. These genes were suggested to