Three TNFalpha single nucleotide polymorphisms in the Japanese population. 
Tumour necrosis factor-alpha (TNFalpha) is an essential regulator of immune responses and is implicated to relate to several types of disease susceptibilities.  Population information on polymorphisms is essential for the study of genetic diseases.  To obtain accurate information about single nucleotide polymorphisms (SNPs) in the TNFalpha gene in the Japanese population.  The entire TNFalpha gene was screened for SNPs by directly sequencing 48 chromosomes derived from 24 unrelated Japanese individuals.  Allele frequencies of each polymorphism were determined and compared with those previously reported in other populations.  Three SNPs, -308G/A at nt -308, IVS1 + 125G/A at nt 492 and IVS3 + 104G/A at nt 1359 were observed, of which one (IVS3 + 104G/A at nt 1359) was novel.  In addition, allele frequencies of -308G/A were remarkably different from those presented in the NCBI dbSNP, indicating a significant ethnic difference.  The polymorphisms and allele frequencies obtained in this study will be useful for genetic studies of common diseases such as osteoporosis and rheumatoid arthritis in the Japanese population.