Transcription profiling of HCN-channel isotypes throughout mouse cardiac development.
Hyperpolarization-activated ion channels, encoded by four mammalian genes (HCN1-4), contribute in an important way to the cardiac pacemaker current I(f). Here, we describe the transcription profiles of the four HCN genes, the NRSF, KCNE2 and Kir2.1 genes from embryonic stage E9.5 dpc to postnatal day 120 in the mouse. Embryonic atrium and ventricle revealed abundant HCN4 transcription but other HCN transcripts were almost absent. Towards birth, HCN4 was downregulated in the atrium and almost vanished from the ventricle. After birth, however, HCN isotype transcription changed remarkably, showing increased levels of HCN1, HCN2 and HCN4 in the atrium and of HCN2 and HCN4 in the ventricle. HCN3 showed highest transcription at early embryonic stages and was hardly detectable thereafter. At postnatal day 10, HCN4 was highest in the sinoatrial node, being twofold higher than HCN1 and fivefold higher than HCN2. In the atrium, HCN4 was similar to HCN1 and sevenfold higher than HCN2. In the ventricle, in contrast, HCN2 was sixfold higher than HCN4, while HCN1 was absent. Subsequently all HCN isotype transcripts declined to lower adult levels, while ratios of HCN isotypes remained stable. In conclusion, substantial changes of HCN isotype transcription throughout cardiac development suggest that a regulated pattern of HCN isotypes is required to establish and ensure a stable heart rhythm. Furthermore, constantly low HCN transcription in adult myocardium may be required to prevent atrial and ventricular arrhythmogenesis.
Universitätsklinikum Heidelberg, Innere Medizin III, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.
Patrick A
PA
Schweizer
Pessah
P
Yampolsky
Rizwan
R
Malik
Dierk
D
Thomas
Joerg
J
Zehelein
Hugo A
HA
Katus
Michael
M
Koenen
D000818:Animals; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000096:biosynthesis / Q000235:genetics; D015870:Gene Expression; D020869:Gene Expression Profiling; D006321:Heart / Q000196:embryology* / Q000254:growth & development*; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D009206:Myocardium / Q000378:metabolism*; D015221:Potassium Channels / Q000096:biosynthesis* / Q000235:genetics*; D024661:Potassium Channels, Inwardly Rectifying / Q000096:biosynthesis / Q000235:genetics; D024642:Potassium Channels, Voltage-Gated / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
D054815:Cyclic Nucleotide-Gated Cation Channels; C578669:HCN3 protein, mouse; C578666:Hcn1 protein, mouse; C578711:Hcn2 protein, mouse; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; C489620:Kcne2 protein, mouse; C489461:Kir2.1 channel; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D024642:Potassium Channels, Voltage-Gated