Expression of the imprinted tumour-suppressor gene H19 is tightly regulated during normal haematopoiesis and is reduced in haematopoietic precursors of patients with the myeloproliferative disease polycythaemia vera

cDNA subtraction was employed to uncover differences in gene expression between myeloproliferative polycythaemia vera (PV) and normal haematopoietic precursors. Following cDNA subtraction using mRNAs isolated from PV and normal CD34+/CD33- bone-marrow cells, expression of the tumour suppressor H19 was found to be low or absent in the PV sample. Low levels of H19 expression in PV patients were confirmed by in situ hybridization. Using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) to examine expression in the pluripotent haematopoietic cell line FDCP-mix and single bone-marrow precursors, unambiguous IGF2 and H19 expression was demonstrated in normal haematopoietic precursors. Examination of individual bone-marrow precursors revealed that all IGF2-expressing haematopoietic precursors also co-expressed H19, indicating that H19 and IGF2 may be co- ordinately regulated during haematopoiesis. Analysis of FDCP-mix undergoing differentiation and single pluripotent and committed bone-marrow precursors revealed that the pattern of H19 expression coincided with the commitment to a single lineage. Taken together, these observations demonstrate that H19 and IGF2 are specifically expressed during haematopoiesis and that low levels of H19 expression are associated with PV and may contribute to the pathology of the disease.