Characterization and target genes of nine human PRD-like homeobox domain genes expressed exclusively in early embryos.

Elo Madissoon,Fredrik Lanner,Liselotte Vesterlund,Kaarel Krjutškov,Elisabet Einarsdottir,Virpi Töhönen,Shintaro Katayama,Outi Hovatta,Robert Månsson,Sten Linnarsson,Thomas R Bürglin,Juha Kere,Eeva-Mari Jouhilahti,Sophie Petropoulos

doi:10.1038/srep28995

Abstract

PAIRED (PRD)-like homeobox genes belong to a class of predicted transcription factor genes. Several of these PRD-like homeobox genes have been predicted in silico from genomic sequence but until recently had no evidence of transcript expression. We found recently that nine PRD-like homeobox genes, ARGFX, CPHX1, CPHX2, DPRX, DUXA, DUXB, NOBOX, TPRX1 and TPRX2, were expressed in human preimplantation embryos. In the current study we characterized these PRD-like homeobox genes in depth and studied their functions as transcription factors. We cloned multiple transcript variants from human embryos and showed that the expression of these genes is specific to embryos and pluripotent stem cells. Overexpression of the genes in human embryonic stem cells confirmed their roles as transcription factors as either activators (CPHX1, CPHX2, ARGFX) or repressors (DPRX, DUXA, TPRX2) with distinct targets that could be explained by the amino acid sequence in homeodomain. Some PRD-like homeodomain transcription factors had high concordance of target genes and showed enrichment for both developmentally important gene sets and a 36 bp DNA recognition motif implicated in Embryo Genome Activation (EGA). Our data implicate a role for these previously uncharacterized PRD-like homeodomain proteins in the regulation of human embryo genome activation and preimplantation embryo development.

Highlights

Human preimplantation development, starting with the fusion of egg and sperm and continuing to blastocyst implantation[1] is characterized by drastic changes in gene expression, especially a massive degradation of oocyte transcripts and a gradual, cascade-like initiation of transcription from the embryo genome[2,3]
Our recent study on human preimplantation development revealed the expression of 14 PRD-like homeodomain transcription factors during Embryo Genome Activation (EGA), and we validated the presence of seven factors by cDNA cloning[3]
The homeodomain proteins make up approximately 15–30% of all animal transcription factors[24]

Summary

Introduction

Human preimplantation development, starting with the fusion of egg and sperm and continuing to blastocyst implantation[1] is characterized by drastic changes in gene expression, especially a massive degradation of oocyte transcripts and a gradual, cascade-like initiation of transcription from the embryo genome[2,3]. Recently the PRD-like homeodomain transcription factors were implicated in human EGA and preimplantation development[3]. Homeobox genes are relatively well characterized in several model organisms, especially in Drosophila melanogaster, and several of the PRD-like homeobox genes have previously been suggested to be expressed in the human germline[7]. Our recent study on human preimplantation development revealed the expression of 14 PRD-like homeodomain transcription factors during EGA, and we validated the presence of seven factors by cDNA cloning[3]. Most of these transcription factors had been predicted[7,10], but only a few had been validated on transcript level[11]

Methods

Results

Conclusion