I am working on Thalassemia patients and want to check their hypoxia status by expression analysis of the concerned genes. Could anyone recommend which gene would be more suitable in this case; HIF1a or HIF2a? Inputs from anyone having experience in hypoxia studies would be highly appreciated.
I think this is a too indirect measure. HIF activity in response to hypoxic conditions is regulated on the protein level (via normal ubiquitilylation and degradation which is blocked in hypoxia leading to an accumulation of active HIF). There is no need to modify the gene expression. And even if the gene expression is altered, it may be a compensatory reaction to a changed regulation status (e.g. the expression may be increased to compensate for a lower sensitivity to hypoxia).
If you really want to assess the hypoxia status, try to measure the status of PHDs and the HIF protein concentration, and also maybe the concentration of oxygen radicals, which are assumed to be increased in hypoxia.
If measureing HIF2 makes sense depends on the cell type, because HIF2 is not expressed in all cells.
Behroz Khan
I have this for you as a mechanism that may point to HIF-1. Hypoxia-inducible factor 1 is a transcription factor that functions as a master regulator of oxygen homeostasis. It consists of two subunits: an inducibly-expressed HIF-1alpha subunit and a constitutively-expressed HIF-1beta subunit. Under normoxia, HIF-1 alpha undergoes hydroxylation at specific prolyl residues which leads to an immediate ubiquitination and subsequent proteasomal degradation of the subunit. In contrast, under hypoxia, HIF-1 alpha subunit becomes stable and interacts with coactivators such as p300/CBP to modulate its transcriptional activity. Eventually, HIF-1 acts as a master regulator of numerous hypoxia-inducible genes under hypoxic conditions. The target genes of HIF-1 encode proteins that increase O2 delivery and mediate adaptive responses to O2 deprivation. Despite its name, HIF-1 is induced not only in response to reduced oxygen availability but also by other stimulants, such as nitric oxide, or various growth factors.
Therefore, in an hypoxic situation such as in thalassemia, HIF-1 may be a useful diagnostic marker.
From my own perspective (cancer area), I have come across usefulness of HIF-1 in hypoxia as targeted way for treatment strategy, knowing well that many genes have pleiotropic effects, you may go for investigating HIF-1 in a related pathological feature.
