The EZH2 gene is a homolog of the Drosophila Polycomb group (PcG) gene enhancer 
of zest, a crucial regulator of homeotic gene expression. Several lines of 
evidence suggest a critical role for the EZH2 protein during normal and 
perturbed development of the haematopoietic and central nervous systems. Indeed, 
the EZH2 protein has been shown to associate with the Vav proto-oncoprotein and 
with the XNP protein, the product of a mental retardation gene. The EZH2 gene 
was previously reported to be located on chromosome 21q22 and was proposed as a 
candidate gene for some characteristics of the Down syndrome phenotype. We 
report here the genomic structure and fine mapping of the EZH2 gene. We 
demonstrate that the functional gene actually maps to chromosome 7q35 and that 
the sequence previously isolated from a chromosome 21 cosmid corresponds to a 
pseudogene. Finally, the nature of the EZH2 protein and its mapping to the 
critical region for malignant myeloid disorders lead us to propose the EZH2 gene 
is involved in the pathogenesis of 7q35-q36 aberrations in myeloid leukaemia.