Breakpoints of the t(11;18)(q21;q21) in mucosa-associated lymphoid tissue (MALT) lymphoma lie within or near the previously undescribed gene MALT1 inchromosome 18

Lymphomas arising in mucosa-associated lymphoid tissue (MALT) are indolent B-cell tumors that have a predilection for epithelial sites and often devel op in a setting of chronic inflammation or autoimmunity, As many as 50% of low-grade MALT Lymphomas contain an (11;18)(q21;q21) chromosomal translocat ion, Using fluorescence in situ hybridization, we have analyzed the positio n of recombination within chromosome 18 DNA in three examples of MALT lymph oma bearing this translocation. In all three cases, the breakpoint maps to DNA in BAC b357H2, covering about 150 kb of sequence. A previously undescri bed, ubiquitously expressed gene, which we refer to as MALT1, was identifie d within this sequence and was found to be broken in one case for which we have definitively located the position of recombination between chromosomes 18 and 11, The sequence of this gene indicates the presence of two immunog lobulin-like C2 domains and a region of partial homology to caspases, sugge sting a possible role for MALT1 in the regulation of apoptosis.