Further, ARNTL2 expression correlated positively with the expression of CRY1 (.715; p<0.05), CRY2 (.951; p<0.001), PER2 (.862; p<0.01), BHLHE40 (.936; p<0.001) and BHLHE41 (.785; p<0.01) only in RA. The gene discussed is PER2; the disease is rheumatoid arthritis.