EXPRESSION OF HOX C HOMEOBOX GENES IN LYMPHOID-CELLS

The class I homeobox genes located in four clusters in mammalian genom es (HOX A, HOX B, HOX C, and HOX D) appear to play a major role in fet al development. Previous surveys of homeobox gene expression in human leukemic cell lines have shown that certain HOX A genes are expressed only in myeloid cell lines, whereas HOX B gene expression is largely r estricted to cells with erythroid potential. We now report a survey of the expression patterns of 9 homeobox genes from the HOX C locus in a panel of 24 human and 7 murine leukemic cell lines. The most striking observation is the lymphoid-specific pattern of expression of HOX C4, located at the 3' end of the locus. A major transcript of 1.9 kilobas es is observed in both T-cell and B-cell lines. HOX C4 expression is a lso detected in normal human marrow and peripheral blood lymphocytes, but not in mature granulocytes or monocytes. HOX C8 is also expressed in human lymphoid cells but is expressed in other blood cell types as well. However, the HOX C8 transcript pattern is lineage specific. Thes e data, in conjunction with earlier findings, suggest that homeobox ge ne expression influences lineage determination during hematopoiesis.