Transcription of homeobox-containing genes detected in cDNA libraries derived from human unfertilized oocytes and preimplantation embryos

Genes containing the evolutionarily conserved homeodomain sequence encode a family of DNA-binding transcription factors whose functions are crucial for embryonic development in vertebrates, invertebrates and plants. We describe the detection and analysis of transcripts of homeobox-containing genes present in cDNA libraries generated from human unfertilized oocytes, single cleavage stage embryos (2-cell, 4-cell, 8-cell and blastocyst) and a 10-week old whole fetus. Using degenerate primers derived from sequences within helix 1 and helix 3 of the highly conserved region of the Antennapedia-class homeodomain, a 166 bp band was detected in all the cDNA libraries tested. Subcloning of the oocyte-derived band revealed that it contained a heterogeneous group of 166 bp fragments. Sequence analysis of 40 independent clones demonstrated the presence of HOXA7, HOXD8, and HOXD1 sequences, the ubiquitously expressed POU family member, OCT1, and HEX, a homeotic gene expressed in haematopoietic cells.