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Engineered Zinc Finger Proteins make the Heart Beat Stronger

 
  November, 22 2005 23:54
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Sangamo BioSciences presented data at the Scientific Sessions of the American Heart Association in Dallas, TX (Nov 16th, 2005). In the presentation Sangamo showed data from their program to develop a zinc finger protein therapeutic (ZFP) for congestive heart failure. The studies presented demonstrate that the ZFP transcription factors bind and repress the phospholamban gene in human cells and in rat cardiomyocytes with spectacular specificity.

Sangamo’s platform centers on the design of synthetic zinc finger proteins; the largest class of endogenous DNA binding proteins identified in vivo. Each finger of a ZFP binds to a three base pair target site in DNA with high specificity. Forming arrays of zinc fingers within a single protein allows the recognition of longer DNA sequences and, consequently, vastly improved selectivity. Taking this powerful technology a step further, the Company has fused these DNA binding domains to various transcriptional regulatory peptides allowing activation or repression of any gene bound by the ZFP. The whole expression cassette can then be cloned into a plasmid under the control of a powerful promoter and delivered either as a plasmid or via a viral intermediate to the target tissue of interest. In this case Sangamo have targeted the Phospholamban (PLN) gene for repression as therapy for congestive heart failure (CHF).

Phospholamban (PLN) is the regulator of the SR Ca2+ATPase (SERCA2a) activity in cardiac, slow-twitch skeletal and smooth muscle sarcoplasmic reticulum. Dephosphorylated phospholamban inhibits the affinity of SR Ca2+ATPase for Ca2+, whereas phosphorylation removes this inhibition; allowing reuptake of Calcium to sarcoplasmic stores.

CHF is a fatal disease more common among the elderly because of accumulated heart damage. It is a syndrome in which elevated pressure inside the heart causes fluid to back up in the body. CHF can be caused by prior heart attack, long-standing high blood pressure, diabetes, or a tight or leaky heart valve. A person age 40 or older has a one-in-five chance of developing congestive heart failure.

Both reduced fractional shortening and reduced velocity of contraction characterize myocardial failure in CHF. A basic feature of CHF seems to be a reduced Ca2+ load of the sarcoplasmic reticulum (SR) mainly due to a low phosphorylation level of phospholamban. In order to relieve this inhibition, the ZFP-TF repressor inhibits the expression of PLN, removes the inhibition of SERCA2a, and enhances the cardiac muscle function

When administered as a construct into the hearts of adult rats, a ZFP-TF PLN repressor improved calcium flux and enhanced both the rate and extent of relaxation and contraction cycles of the in vivo cardiomyocytes. Moreover, in a rat model of heart failure, treatment with the same repressor demonstrated improved contractility and hemodynamics in the disease-model hearts.


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