Familial Mediterranean fever (FMF) is a recessively inherited disorder 
characterized by recurrent, self-limited attacks of fever and serositis and by 
infiltration of affected tissues by large numbers of neutrophils. A candidate 
gene for FMF was identified by positional cloning and named "MEFV." The 
corresponding protein was named "pyrin." To elucidate the currently unknown 
function of pyrin, we characterized its tissue distribution, regulation of 
expression during hematopoietic differentiation, and subcellular localization. 
Reverse transcription-polymerase chain reaction analysis, followed by 
hybridization with an internal oligonucleotide, demonstrated expression of MEFV 
in different populations of peripheral blood cells. Among hematopoietic cell 
lines, MEFV was almost exclusively expressed in cells of the myeloid lineage. 
Furthermore, MEFV messenger RNA was strongly expressed within 24 hours of 
dimethyl sulfoxide-induced granulocytic differentiation of HL-60 cells. Analysis 
of complementary DNA from human solid tumor-derived cell lines revealed 
expression of MEFV in several cell lines derived from colon and prostate 
cancers. Expression of MEFV fused to enhanced green fluorescent protein showed 
that pyrin localized in distinct patches in the cytoplasm, forming a perinuclear 
cap. Taken together, MEFV is predominantly expressed in myeloid cells and 
upregulated during myeloid differentiation, and the corresponding protein, 
pyrin, is expressed in the cytoplasm. (Blood. 2000;95:1451-1455)