cDNA cloning and expression of the human NOBOX gene in oocytes and ovarian follicles

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).