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. 2000 Apr 25;97(9):4826-31.
doi: 10.1073/pnas.97.9.4826.

Conditional expression of a Gi-coupled receptor causes ventricular conduction delay and a lethal cardiomyopathy

C H Redfern  1 , M Y Degtyarev, A T Kwa, N Salomonis, N Cotte, T Nanevicz, N Fidelman, K Desai, K Vranizan, E K Lee, P Coward, N Shah, J A Warrington, G I Fishman, D Bernstein, A J Baker, B R Conklin
Affiliations

Conditional expression of a Gi-coupled receptor causes ventricular conduction delay and a lethal cardiomyopathy

C H Redfern et al. Proc Natl Acad Sci U S A. .

Abstract

Cardiomyopathy is a major cause of morbidity and mortality. Ventricular conduction delay, as shown by prolonged deflections in the electrocardiogram caused by delayed ventricular contraction (wide QRS complex), is a common feature of cardiomyopathy and is associated with a poor prognosis. Although the G(i)-signaling pathway is up-regulated in certain cardiomyopathies, previous studies suggested this up-regulation was compensatory rather than a potential cause of the disease. Using the tetracycline transactivator system and a modified G(i)-coupled receptor (Ro1), we provide evidence that increased G(i) signaling in mice can result in a lethal cardiomyopathy associated with a wide QRS complex arrhythmia. Induced expression of Ro1 in adult mice resulted in a >90% mortality rate at 16 wk, whereas suppression of Ro1 expression after 8 wk protected mice from further mortality and allowed partial improvement in systolic function. Results of DNA-array analysis of over 6,000 genes from hearts expressing Ro1 are consistent with hyperactive G(i) signaling. DNA-array analysis also identified known markers of cardiomyopathy and hundreds of previously unknown potential diagnostic markers and therapeutic targets for this syndrome. Our system allows cardiomyopathy to be induced and reversed in adult mice, providing an unprecedented opportunity to dissect the role of G(i) signaling in causing cardiac pathology.

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Figures

Figure 1
Figure 1
Survival of mice expressing Ro1 in the heart: Kaplan–Meier survival plot of adult mice expressing Ro1. Doxycycline was withdrawn from 15 αMHC-tTA/tetO-Ro1 mice to induce Ro1 expression. All αMHC-tTA/tetO-Ro1 mice survived maximal induction of Ro1 (7–10 days). More than 40% of the mice died after 8 wk of Ro1 expression and 90% after 16 wk. Reinitiation (arrow) of doxycycline at 8 wk prevented further mortality in another group of αMHC-tTA/tetO-Ro1 mice (n = 15). None of the control mice died (αMHC-tTA/tetO-Ro1 on doxycycline for 16 wk, n = 20).
Figure 2
Figure 2
PTX reveals Gi-induced ventricular conduction delay and drug-induced signaling via expression of Ro1. Administration of PTX reduced ECG abnormalities in mice expressing Ro1. (A) Sinus rhythm (heart rate, 600 beats per min) with narrow QRS complex (<15 ms) before Ro1 expression. (B) Irregular rhythm with widened QRS complex (>25 ms) after 20 days of Ro1 expression. (C) Irregular rhythm with widened QRS maintained for 48 h before PTX injection. (D) Sinus rhythm (heart rate, 600 beats per min) with narrow QRS complex (<15 ms) 24 h after PTX injection.
Figure 3
Figure 3
Expression of Ro1 in mouse heart causes a cardiomyopathy. (A and B) Control mouse (A, αMHC-tTA) and Ro1-expressing mouse with anasarca (B). (C and D) Photomicrographs (×5) of hematoxylin/eosin-stained cross sections of mouse heart. The ventricular chambers were larger and the ventricular walls thinner in the mouse expressing Ro1 (D) than in the control mouse (C).
Figure 4
Figure 4
Progression of inducible cardiac pathology in mice expressing Ro1. (A) Photomicrographs (×40) of hematoxylin/eosin-stained sections of myocardium from mice expressing Ro1. Cellular infiltration begins at 2 wk after doxycycline (Doxy) removal and is followed by myofibril disarray at 8 wk. Note the lack of improvement in myocardial histology in mice that had Ro1 expression for 8 wk followed by Ro1 suppression for 4 wk (8 wk + reversal). (B) Photomicrographs (×50) of Sirius red-stained sections of myocardium from mice expressing Ro1. Collagen deposition begins at 4 wk (not shown) and is most prominent at 8 wk. Note lack of improvement in the 8 wk + reversal group.
Figure 5
Figure 5
Echocardiographic evidence of cardiomyopathy and recovery in mice expressing Ro1. (A) LV dimension. Mice expressing Ro1 for 8 wk showed an increase in LV end-systolic diameter (LVESD) (■, Ro1, αMHC-tTA/tetO-Ro1, n = 9; ○, control, αMHC-tTA, n = 9). After administration of doxycycline (Doxy) to these same mice for 4 wk, there was a persistent increase in LVESD and a new increase in LV end-diastolic diameter (LVEDD). (B) Peak flow velocity. After 8 wk of Ro1 expression, aortic peak flow velocity decreased by nearly 40%. After 4 wk of doxycycline administration, peak flow velocity increased significantly. (C) LVFS. After 8 wk of Ro1 expression, LVFS decreased by nearly 40%. LVFS increased significantly after suppression of Ro1 expression but remained less than LVFS in control mice. *, P < 0.05 vs. controls; **, P < 0.001 vs. controls; †, P < 0.05 vs. same mice at the previous time point.
Figure 6
Figure 6
Ro1-induced gene-expression changes in the G protein signaling cascade. All genes known to be downstream of G proteins were mapped, and gene-expression changes were indicated by using GenMAPP (www.GenMAPP.org). Significant changes (P < 0.05) are indicated by colors. The fold change is noted at the right of each box. Genes that are absent on the DNA array are in clear boxes. Nonsignificant (P > 0.05) changes are indicated by yellow. The abbreviation definitions, GenBank numbers, and expression values are all available in an interactive version of this figure and another figure focusing on information in Fig. 8 A and B in the supplemental material at www.pnas.org. Abbreviations include CaL, L-type calcium channel; AC, adenylyl cyclase; PLC, phospholipase C; Rho GEF, rho guanine nucleotide exchange factor; IP3, inositol trisphosphate; DAG, diacylglycerol; PDE, phosphodiesterase; PKA, protein kinase A; PKC, protein kinase C; CalM, calmodulin; Calc, calcineurin; CREB, cAMP response element binding protein; cAMP-dependent transcription factor; NFAT, nuclear factor of activated cells; NHE, Na+/H+ exchanger.
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References

    1. Olson T M, Keating M T. J Clin Invest. 1996;97:528–532. - PMC - PubMed
    1. Schwartz K, Mercadier J-J. Curr Opin Cardiol. 1996;11:227–236. - PubMed
    1. Cohn J N, Bristow M R, Chien K R, Colucci W S, Frazier O H, Leinwand L A, Lorell B H, Moss A J, Sonnenblick E H, Walsh R A, et al. Circulation. 1997;95:766–770. - PubMed
    1. Manolio T A, Baughman K L, Rodeheffer R, Pearson T A, Bristow J D, Michels V V, Abelmann W H, Harlan W R. Am J Cardiol. 1992;69:1458–1466. - PubMed
    1. Xiao H B, Roy C, Gibson D G. Br Heart J. 1994;72:167–174. - PMC - PubMed

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