sentence: These EC genes included B2M ( beta-2-microglogulin ) [ 5 ] , HPRT ( hypoxanthine guanine phosphoribosyl transferase 1 ) [ 3,28 ] , GAPDH [ 29 ] , ACTB ( beta-actin ) [ 30 ] , PPIA ( peptidyl-prolyl isomerise A ) [ 9 ] and MRPL19 ( mitochondrial ribosomal protein L19 ) [ 9 ] .