The genetic analysis of the Foxa genes in both total and conditional mutant mice 
has clearly established that organogenesis of multiple systems is controlled by 
this subfamily of winged helix transcription factors. These discoveries followed 
the establishment of the conceptional framework of the mechanism of action of 
the FoxA proteins as 'pioneer factors' that can engage chromatin before other 
transcription factors. Recent molecular and genomic studies have also shown that 
FoxA proteins can facilitate binding of several nuclear receptors to their 
respective targets in a context-dependent manner, greatly increasing the range 
and importance of FoxA factors in biology.