The homeotic genes, whose products serve as determinants of embryonic cell fate, are expressed in a series of different
but partially overlapping domains that extend along the anterior-posterior (A-P) axis of the embryo. The Hox genes
share a 180-bp homeo box, which encodes a 60-amino acid homeodomain that binds specifically to DNA. There are 4
Hox gene clusters: HOXA (formerly HOX1) on chromosome 7, HOXB (formerly HOX2) on chromosome 17, HOXC
(formerly HOX3) on chromosome 12, and HOXD (formerly HOX4) on chromosome 2. By sequence comparison, the
genes of each cluster are assigned to 1 of 13 groups. The order of the HOX genes along the chromosome reflects where
they are expressed along the body axis.
General function
Nucleic acid binding, DNA binding, Transcription factor
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Cellular localization
Nuclear
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Ovarian function
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Expression regulated by
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Ovarian localization
Oocyte
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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. Adjaye et al 2000 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.