NKX2-5 and systemic lupus erythematosus: The effect of NKX2-5 on gene expression has been previously described [15] and SNPs within NKX2-5 binding sites have been reported to be functional for complex genetic diseases as systemic lupus erythematosus, rheumatoid arthritis, and graves disease in man as the mutations lead to a reduced expression of the respective gene [16].