IDENTIFICATION OF A NOVEL CDNA, ENCODING A CYTOSKELETAL-ASSOCIATED PROTEIN, DIFFERENTIALLY EXPRESSED IN DIFFUSE LARGE B-CELL LYMPHOMAS

Diffuse large B-cell lymphomas (DLBL) constitute an heterogeneous clin ico-pathological entity. To characterize molecular events related to h istological subtypes, clinical presentation or outcome, we compared th e mRNAs expressed in a limited series of DLBL by Differential display- reverse transcription (DDRT) and cloned a differential cDNA, that we c alled LB1, LB1 open reading frame encodes a 683 amino-acid polypeptide that does not show significant homology upon comparison to protein da tabases, nor any structural domain relating LB1 to an already known pr otein family, Immunofluorescence analysis of transfected COS cells sho wed a cytoplasmic filamentous staining, indicating that LB1 protein is tightly associated with cytoskeletal fibers, Two LB1 transcripts, a m ajor 3,6 - 3.9 Kb and a minor 2.2 Kb transcripts, were detected among human haematopoietic and non-haematopoietic lines and tissues, LB1 tra nscripts were abundant in testis, thymus and in tumour derived cell li nes, while barely detectable in liver, prostate and kidney, Concerning DLBL, LB1 expression was high in two cases of DLBL, and low or undete ctable in four others, confirming the differential expression previous ly observed in the DDRT experiment. Furthermore, LB1 gene mapped to ch romosome 13q14, a region that has been involved as a chromosomal break point in DLBL, The cellular function of LB1 and its relationship with B cell maturation and/or oncogenesis remain to be established.