Negative Feedback Loop Mechanism (IMAGE) Biogerontology Research Foundation Caption Negative feedback loop mechanism. If the promoter of HTT is used to drive the shRNA construct, a stoichiometric equivalent of shRNA may be expressed to neutralize mHTT levels. A similar strategy may be employed for constructs activated during autophagy and lysosomal biogenesis, such as PGC1a. Then, the shRNA will be expressed when HTT aggregates have formed to induce autophagy or clearance -- shRNA on demand and only when required by the cell Credit Translational Neuroscience Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.