Oct-4: More Than A Pluripotent Marker?

oct-4/ pou5f1/ oct-3, a pou domain family protein acts as a crucial transcription factor duringembryonic development. it helps in maintenance of self renewal as well as pluripotentialstate of embryonic stem (es) cells. its expression starts right from 2 cell stage especiallyprior to 8 cell stage till the blastocyst stage where it is strongly expressed in inner cell mass(icm). thereafter, it is located predominantly in primordial germ cells (pgcs) till the birth. ittargets particularly those genes which bear an octameric motif atgcaaat in promoter orenhancer region. most of the target genes of oct-4 are expressed in undifferentiated es cellsand knockdown of oct-4 results in es cell differentiation as a result of down regulation oftargets of oct-4 which are expressed in es cells. since, oct-4 is crucial for embryo survivalits expression needs tight regulation. oct-4 is carefully regulated epigenetically as well asby several other factors. dna methylation and histone modification play an important role inexpression of oct-4 while proximal promoter, enhancer and distal enhancer are the crucialregulatory elements present on oct-4 upstream region. there is increasing evidence thatoct-4 is expressed in adult stem cells and these stem cells can get converted to cancer stemcells. since, it is expressed in germ cells, immunohistochemical localization of oct-4 andthereby its role as a marker for germ cell tumor detection is increasing. thus, role of oct-4 isnot only restricted as a marker for undifferentiated cells; it is also proving to be crucial factorwhich targets several genes involved in es cell survival as well as help in establishing germcell origin of metastatic tumors.abstractreceived: 23/sep/2008, accepted: 23/nov/2008oct-4/ pou5f1/ oct-3, a pou domain family protein acts as a crucial transcription factor duringembryonic development. it helps in maintenance of self renewal as well as pluripotentialstate of embryonic stem (es) cells. its expression starts right from 2 cell stage especiallyprior to 8 cell stage till the blastocyst stage where it is strongly expressed in inner cell mass(icm). thereafter, it is located predominantly in primordial germ cells (pgcs) till the birth. ittargets particularly those genes which bear an octameric motif atgcaaat in promoter orenhancer region. most of the target genes of oct-4 are expressed in undifferentiated es cellsand knockdown of oct-4 results in es cell differentiation as a result of down regulation oftargets of oct-4 which are expressed in es cells. since, oct-4 is crucial for embryo survivalits expression needs tight regulation. oct-4 is carefully regulated epigenetically as well asby several other factors. dna methylation and histone modification play an important role inexpression of oct-4 while proximal promoter, enhancer and distal enhancer are the crucialregulatory elements present on oct-4 upstream region. there is increasing evidence thatoct-4 is expressed in adult stem cells and these stem cells can get converted to cancer stemcells. since, it is expressed in germ cells, immunohistochemical localization of oct-4 andthereby its role as a marker for germ cell tumor detection is increasing. thus, role of oct-4 isnot only restricted as a marker for undifferentiated cells; it is also proving to be crucial factorwhich targets several genes involved in es cell survival as well as help in establishing germcell origin of metastatic tumors.