title: Intracellular calcium plays an essential role in cardiac development.
abstract: Intracellular calcium signaling plays an essential role in cardiac physiology and modulates cardiac gene expression. However, the role that intracellular calcium signaling plays during cardiac development is not known. To address this issue, we examined the effects of altered intracellular calcium levels on cardiac morphogenesis. In acutely cultured mouse embryos, L-type calcium channel blockade decreased resting intracellular calcium levels and inhibited calcium transients. Embryos cultured at embryonic day (E) 7.5-8.5 in the presence of the L-type calcium channel blockers nifedipine and verapamil developed hearts that had a large left ventricle, lacked a right ventricle and had a long, thin outflow tract. If embryos were cultured at E7.5, calcium channel blockade also induced an abnormal, anterior cardiac loop. These alterations in development were not due to altered cardiac function, as heart rates at the end of the culture period were not affected by calcium channel blockade and blood flow was observed. Treatment with nifedipine altered the mRNA expression of the transcription factor Gata4, which was absent in the developing ventricles, and the sarcomeric protein Mylpc (myosin light chain 2V), which was decreased distal to the left ventricle and was absent at the site of the developing right ventricle. In contrast, the expression pattern of other cardiac transcription factor (Hand1, Hand2, Mef2c, Nkx2-5) and cytoskeletal protein (Myhca, Tagln) mRNA did not change with calcium channel blockade. These data demonstrate that proper intracellular calcium signaling is essential for normal cardiac looping, gene expression, and organ development.
authors.affiliation: Yale Child Health Research Center and Department of Pediatrics, Division of Cardiology, Yale University School of Medicine, New Haven, Connecticut 06520-8064, USA. george.porter@yale.edu
authors.forename: George A
authors.initials: GA
authors.lastname: Porter
authors.forename: Ryan F
authors.initials: RF
authors.lastname: Makuck
authors.forename: Scott A
authors.initials: SA
authors.lastname: Rivkees
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics; D050991:GATA4 Transcription Factor; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D006321:Heart / Q000196:embryology*; D006352:Heart Ventricles / Q000196:embryology; D051379:Mice; D008810:Mice, Inbred C57BL; D009543:Nifedipine / Q000494:pharmacology; D009924:Organ Culture Techniques; D014157:Transcription Factors / Q000235:genetics; D014700:Verapamil / Q000494:pharmacology; D015017:Yolk Sac / Q000502:physiology
chemical_list: D002121:Calcium Channel Blockers; D004268:DNA-Binding Proteins; D050991:GATA4 Transcription Factor; D014157:Transcription Factors; D014700:Verapamil; D009543:Nifedipine; D002118:Calcium