ABCG2 is expressed in the developing human heart. (A) Representative RT-PCR analysis for ABCG2 expression from CS18 (6 weeks pc) through to F5 (13 weeks pc) comparing the expression of ABCG2 mRNA in distinct anatomical cardiac regions. Note at CS18 the expression appears to be similar in all cardiac regions with the exception of the OFT where it is slightly elevated. At CS23 (8 weeks pc) expression is down regulated in the LV compared with the other anatomical regions and in the fetal stages the expression of ABCG2 is reduced in LV, LA compared with the RV, RA and OFT. GapdH was used as a loading control. (B) FACS profile of CSP cells from an F1 heart (9 weeks pc). (C) Inhibition of the SP cell phenotype after addition of FTC. Abbreviations: pc: post conception; SP, side population: RV, right ventricle; LV, left ventricle; RA, right atria; LA, left atria; OFT, outflow tract; FTC, fumitremorgin C; RT-PCR, reverse transcriptase polymerase chain reaction. IHC analysis for ABCG2, ABCG2 expressing cells are located throughout the human embryonic and fetal heart. Shown are representative images taken of cardiac tissue stained with an anti-ABCG2 antisera. (D and F) ABCG2 expressing cells in the embryonic heart at CS23 (8 weeks pc) (D) and in the ventricles at F1 (9 weeks pc) shown here in the LV (F). Note the absence of staining in the no primary negative control (E). ABCG2 was visualised with 3’-diaminobenzidine (brown), all sections were counterstained with haematoxylin (blue). Magnifications: size bar = 10 μm for all images; Abbreviations: pc: post conception; SP, side population: RV, right ventricle; LV, left ventricle; RA, right atria; LA, left atria; OFT, outflow tract; FTC, fumitremorgin C; RT-PCR, reverse transcriptase polymerase chain reaction, IHC, immunohistochemical.