Cloning , Expression , and Chromosomal Localization to llpl 2-13 of a Human LIM / HOMEOBOX Gene , hLim-1

We have identified a putative transcription factor, designated hLim-1, from human fetal brain using degen¬ erate polymerase chain reaction (PCR) and cDNA library screening. The deduced open reading frame, de¬ rived from sequencing a 3.0-kb hLim-1 cDNA, encodes a protein of 384 amino acids with two cysteine-rich LIM domains and one homeobox (HOX) DNA-binding domain. The nucleotide sequence of hLim-1 cDNA is 87% identical to mouse Lim-1 and the predicted amino acid sequence is greater than 97% conserved. Ex¬ pression patterns of hLim-1 were evaluated by Northern analysis and reverse transcription (RT)-PCR cou¬ pled with Southern blotting. HLim-1 expression was observed in human brain, thymus, and tonsillar tissue. Expression of hLim-1 was also observed in 58% of acute myelogenous leukemia (AML) cell lines and in four of five primary samples from patients with chronic myeloid leukemia (CML) in myeloid blast transforma¬ tion. The gene encoding hLim-1 was mapped using fluorescence in situ hybridization (FISH) to human chro¬ mosome 11 12— 13. The expression pattern and structural characteristics of the hLim-1 gene suggest that it encodes a transcriptional regulatory protein involved in the control of differentiation and development of neural and lymphoid cells. Its expression in CML in blast crisis suggests that it may be involved with pro¬ gression in this disease; a prospective study is required to confirm this. INTRODUCTION 1992), mLim-1 (Barnes et al., 1994), rLH2 (Xu et al., 1993), hLH2 (Wu et al, 1996), and mLim-3 (Seidel et al., 1994). Lin Genes containing HOMEODOMAiNS play an important role 11 and mec3 are important in the determination of cell fate in in the growth and differentiation of the developing emmechanosensory neurons and vulval cells, respectively. mLH2 bryo and the adult animal. The genes encoding homeodomain was first identified in developing lymphocytes. The gene is proteins may be broadly classed as either clustered or dispersed, expressed in early precursors and is absent from the mature This latter group of homeotic genes can be further divided based progeny, suggesting a role in the differentiation of the cells (Xu upon the presence of certain functional motifs in addition to the et al, 1993). LH2 is also expressed in pituitary cells and apDNA-binding homeodomain; one such motif is the LIM dopears to have a role in the regulation of expression of pituitary main, first recognized in the Lin 11 gene of Caenorhabditis elglycoprotein hormone a-subunit gene (Roberson et al., 1994). egans (Freyd et al., 1990), isl-1 of mammalian cells (Karlsson mLIM3 is expressed in the neuroepithelium of embryos and in et al, 1990), and mec-3 of C. elegans (Way and Chalfie, 1988). adult life it is expressed in the anterior and intermediate lobes The LIM motif consists of cysteine-rich regions capable of comof the pituitary. xLim-1 is predominantly expressed during du¬ plexing zinc and forming finger-like structures. These zinc finbryogenesis in the gastrula stage and in the adult is expressed ger motifs have been shown to be involved in protein-protein in the brain (Taira et al, 1992). The murine homologue, mLiminteractions; to date, there is no convincing evidence of DNA1, is predominantly expressed in the brain and kidney in the binding activity. embryo and adult (Barnes et al, 1994). Members of the LIM-hox family of genes that have been Using degenerate oligonucleotides, we identified the exidentified include Lin 11, isl-1, mec-3, xLim-1 (Taira et al., pression of mLim-1 in mouse fetal brain, liver and spleen. We 'Ontario Cancer Institute, Princess Margaret Hospital, Departments of Medicine, Medical Biophysics, and Institute of Medical Sciences, Uni¬ versity of Toronto, Canada, M5G 2M9. 2Department of Molecular and Medical Genetics, The Hospital For Sick Children, University of Toronto, Canada M5G 2M9.