LH-2: a LIM/homeodomain gene expressed in developing lymphocytes and neural cells

A screen for early markers of B-lymphocyte differentiation has identified a homeobox gene, denoted LH-2, that has a pattern of expression distinct from that of other related genes. The LH-2 cDNA sequence encodes a polypeptide of 426 amino acids that contains a homeodomain and two repeats of a cysteine-rich domain referred to as a LIM domain. The homeodomain of the LH-2 protein is related to that of other LIM/homeodomain proteins, most strikingly with that of the Drosophila apterous protein. Expression of LH-2 was found in B- and T-lymphoid cell lines. Expression in B-cell lines was highest in lines that represent early stages of differentiation, whereas in T-cell lines there was no clear correlation with the stage of differentiation. In embryonic and adult tissues, the highest level of LH-2 expression was found in discrete regions of the developing central nervous system, primarily in diencephalic and telencephalic structures, and in a subset of lymphoid tissues. The expression pattern and structural characteristics of the LH-2 gene suggest that it encodes a transcriptional regulatory protein involved in the control of cell differentiation in developing lymphoid and neural cell types.