Morphometry and muscle gene expression in hypertrophied hearts from polyomavirus large t-antigen transgenic mice . Holder, Emma, Benjamin Mitmaker, Lesley Alpert, and Lorraine Chalifour. Bloomfield Centre for Research in Aging, Lady Davis Institute for Medical Research, Sir Mortimer B. Davis - Jewish General Hospital, 3755 chemin Cte Ste. Catherine, Montr[acute]eal, Qu[acute]ebec, Canada H3T 1E2, The Department of Surgery, McGill University, Sir Mortimer B. Davis -Jewish General Hospital, Lady Davis Institute for Medical Research, The Department of Pathology, McGill University, Sir Mortimer B. Davis-Jewish General Hospital, Lady Davis Institute for Medical Research, The Department of Microbiology and Immunology, McGill Centre for Studies in Aging, Division of Geriatric Medicine and Aging, McGill University, Montr[acute]eal, Qu[acute]ebec, Canada
APStracts 2:0052H, 1995.
Transgenic mice expressing polyomavirus large T-antigen (PVLT) in cardiomyocytes develop a cardiac hypertrophy in adulthood. Morphometric analysis identified cardiomyocytes enlarged up to 9-fold in cross-sectional area in the adult transgenic hearts when compared to normal age-matched non-transgenic hearts. Most enlarged cardiomyocytes were found in the subendocardium whereas normal sized cardiomyocytes were localized to the midmyocardium. Transgenic hearts did not express detectable skeletal muscle actin mRNA or protein, or skeletal troponin I isoform mRNA. Some, but not all, transgenic hearts expressed an increase in the [beta]-myosin heavy chain mRNA. All five transgenic mice tested had increased expression of atrial natriuretic factor mRNA. Whereas normal hearts expressed three myosin light chain proteins of 19, 16 and 15kd, we found that the 19kd myosin light chain was not observed in the transgenic hearts. We conclude that adult, PVLT-expressing, transgenic mice developed enlarged cardiomyocytes with an increase in [beta]-myosin heavy chain and ANF mRNA expression but a widespread skeletal isoform usage was not present in these transgenic mice. The adult transgenic hearts thus display histological and molecular changes similar to those found in hypertrophy induced by a pressure overload in vivo. 

Received 10 June 1994; accepted in final form 2 February 1995.
APS Manuscript Number H516-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 February 1995.