A novel gene named NYGGF4, which was expressed at a higher level in obese subjects, was isolated and characterized. It is a 1527-bp cDNA, containing 753 nucleotides of an ORF (open reading frame) predicting 250 amino acids with a molecular mass of 28.27 kDa. Amino acid sequence analysis revealed NYGGF4 has a phosphotyrosine-binding (PTB) domain. Northern blot analysis revealed NYGGF4 is expressed primarily in adipose tissue, heart, and skeletal muscle but not in any other tissue examined. Confocal imagery analyses with green fluorescent protein-tagged protein transiently expressed in 3T3-L1 preadipocytes and 293-T cells show that NYGGF4 localizes in the cytoplasm. Furthermore, ectopic expression of NYGGF4 dramatically increases the proliferation of 3T3-L1 peadipocytes without affecting adipocytic differentiation. And the NYGGF4 expression 3T3-L1 cells had a greater number of cells in S-phase. Our data suggest that NYGGF4 might be a signaling molecule and could play a role in cell growth and adipogenesis process.