Leucine twenty homeobox gene (LEUTX) is a PAIRED (PRD)-like homeobox gene that is expressed nearly exclusively in human preimplantation embryos. We previously identified a novel transcription start site for the predicted human LEUTX gene based on the transcriptional analysis of human preimplantation embryos. The novel variant encodes a protein with a complete homeodomain. Here we provide a detailed description of the molecular cloning of the complete homeodomain-containing LEUTX. Using a human embryonic stem cell overexpression model we show that the complete homeodomain isoform is functional and sufficient to activate the transcription of a large fraction of the genes found upregulated in human embryo genome activation, whereas the previously predicted partial homeodomain isoform is largely inactive. Another PRD-like transcription factor, DPRX, appears as a powerful repressor of transcription. We propose a two-stage model of human EGA in which LEUTX acts as a transcriptional activator at 4-cell stage, and DPRX as a balancing repressor at 8-cell stage. We conclude that LEUTX is a candidate regulator of human embryo genome activation.
- Received January 8, 2016.
- Accepted August 12, 2016.
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