Spatial distributions of Kv4 channels and KChip2 isoforms in the murine heart based on laser capture microdissection.
OBJECTIVE
Regional differences in repolarizing K(+) current densities and expression levels of their molecular components are important for coordinating the pattern of electrical excitation and repolarization of the heart. The small size of hearts from mice may obscure these interventricular and/or transmural expression differences of K(+) channels. We have examined this possibility in adult mouse ventricle using a technology that provides very high spatial resolution of tissue collection.


METHODS
Conventional manual dissection and laser capture microdissection (LCM) were utilized to dissect tissue from distinct ventricular regions. RNA was isolated from epicardial, mid-myocardial and endocardial layers of both the right and left ventricles. Real-time RT-PCR was used to quantify the transcript expression in these different regions.


RESULTS
LCM revealed significant interventricular and transmural gradients for both Kv4.2 and the alpha-subunit of KChIP2. The expression profile of a second K(+) channel transcript, Kir2.1, which is responsible for the inwardly rectifying K(+) current I(k1), showed no interventricular or transmural gradients and therefore served as a negative control.


CONCLUSIONS
Our findings are in contrast to previous reports of a relatively uniform left ventricular transmural pattern of expression of Kv4.2, Kv4.3 and KChIP2 in adult mouse heart, which appear to be different than that in larger mammals. Specifically, our results demonstrate significant epi- to endocardial differences in the patterns of expression of both Kv4.2 and KChIP2.
Teutsch
Christine
C
Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA.
Kondo
Richard P
RP
Dederko
Dorothy A
DA
Chrast
Jacqueline
J
Chien
Kenneth R
KR
Giles
Wayne R
WR
D000818:Animals; D004699:Endocardium / Q000378:metabolism; D015870:Gene Expression; D006352:Heart Ventricles / Q000737:chemistry; D051605:Kv Channel-Interacting Proteins / Q000235:genetics*; D047569:Laser Scanning Cytometry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D042282:Microdissection / Q000379:methods; D009206:Myocardium / Q000737:chemistry*; D010496:Pericardium / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051672:Shal Potassium Channels / Q000235:genetics*
C489461:Kir2.1 channel; D051605:Kv Channel-Interacting Proteins; D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger; D051672:Shal Potassium Channels