Steven M Pogwizd — Page 2

PubMed2002

Increased expression of alternatively spliced dominant-negative isoform of SRF in human failing hearts.

Serum response factor (SRF) has been shown to play a key role in cardiac cell growth and muscle gene regulation. To understand the role of SRF in heart failure, we compared its expression pattern between control and failing human heart samples. Western blot analysis of control samples showed expression of four different isoforms of SRF, with ~67-kDa full-length SRF being the predominant isoform. Interestingly, in failing hearts we found robust expression of a low-molecular-mass (~52 kDa) SRF isoform, accompanied by decreased expression of full-length SRF. By RT-PCR and Southern blot analyses, we characterized this ~52-kDa SRF isoform as being encoded by an alternatively spliced form of SRF lacking exons 4 and 5 of the SRF primary RNA transcript (SRF-Delta4,5 isoform). We cloned SRF-Delta4,5 cDNA and showed that overexpression of this isoform into cells inhibits SRF-dependent activation of cardiac muscle genes. These results suggest that expression of SRF-Delta4,5 in failing hearts may in part contribute to impaired cardiac gene expression and consequently to the pathogenesis of heart failure.

Adult↗

PubMedDate not supplied

Gene therapy to develop a genetically engineered cardiac pacemaker.

While cardiac pacemakers are frequently used for the treatment of bradydysrhythmias (from diseases of the cardiac conduction system), their use is still limited by complications that can be life-threatening and expensive. Genetic engineering approaches offer an opportunity to modulate cellular automaticity in a manner that could have significant therapeutic potential. It is well known that ventricular myocytes exhibit a more negative diastolic potential than do pacemaker cells, in large part because of the inward rectifying potassium current/K1 (which pacemaker cells lack). Taking advantage of these intrinsic electrophysiological differences, a biological pacemaker has recently been developed by Miake et al (Nature 2002; 419:132-133) using adenoviral gene transfer approaches. By isolating the gene responsible for/K1 (the Kir2.1 gene), mutating it to make it a dysfunctional channel (a dominant-negative), inserting the mutated gene into an adenoviral vector, and delivering the virus to the hearts of guinea pigs, the investigators were able to successfully convert some ventricular myocytes to pacemaker cells. While issues of safety and long-term efficacy need to be further established, the results of these experiments provide proof of principle that gene transfer offers great promise for treatment of electrophysiological disorders including conduction system disease.

Action Potentials↗