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.
Bedford et al. (1993) cloned an HHEX cDNA, which they termed HEX, from human hematopoietic tissue by PCR using
degenerate primers derived from conserved regions of the homeodomain.
NCBI Summary:
This gene encodes a member of the homeobox family of transcription factors, many of which are involved in developmental processes. Expression in specific hematopoietic lineages suggests that this protein may play a role in hematopoietic differentiation. A second transcript variant has been described, but its full length nature has not been determined.
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.
cDNA cloning and expression of the human NOBOX gene in oocytes and ovarian follicles. Huntriss J et al. Nobox is a homeobox gene that is preferentially expressed in the oocytes and is essential for folliculogenesis and the regulation of oocyte-specific gene expression in the mouse. The likely human homologue has been identified in silico but has not as yet been confirmed experimentally. Here, we present the first cDNA cloning and transcript expression analysis of the human NOBOX gene. Using RT-PCR, we reveal that expression within adult human tissues is limited to the ovary, testis and pancreas. Expression within the ovary is oocyte specific, with expression observed from the primordial stage ovarian follicle through to the metaphase II (MII) oocyte. In complementary studies, we reveal dynamic expression profiles of 14 additional homeobox genes throughout human oogenesis and early development. The expression of HOXA10 is restricted to primordial and early primary follicles. HOXB7 is expressed from primordial and early primary stage follicles through to germinal vesicle (GV) oocytes. Gastrulation brain homeobox 1 (GBX1) and HOXA7 genes are homeobox markers preferentially expressed by GV oocytes. HOXA1 and HEX are homeobox markers preferentially expressed by MII oocytes. In summary, the homeobox gene transcripts that are detected in ovarian follicles and oocytes are distinct from those expressed in human blastocysts (HOXB4, CDX2 and HOXC9) and granulosa cells (HOXC9, HOXC8, HOXC6, HOXA7, HOXA5 and HOXA4).