Hypoxia-inducible factor 1α protein expression is controlled by oxygen-regulated ubiquitination that is disrupted by deletions and missense mutations

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that mediates cellular and systemic homeostatic responses to reduced O(2) availability in mammals, including angiogenesis, erythropoiesis, and glycolysis. HIF-1 activity is controlled by the O(2)-regulated expression of the HIF-1α subunit. Under nonhypoxic conditions, HIF-1α protein is subject to ubiquitination and proteasomal degradation. Here we report that missense mutations and/or deletions involving several different regions of HIF-1α result in constitutive expression and transcriptional activity in nonhypoxic cells. We demonstrate that hypoxia results in decreased ubiquitination of HIF-1α and that missense mutations increase HIF-1α expression under nonhypoxic conditions by blocking ubiquitination

A fully implantable pacemaker for the mouse: from battery to wireless power.

Animal models have become a popular platform for the investigation of the molecular and systemic mechanisms of pathological cardiovascular physiology. Chronic pacing studies with implantable pacemakers in large animals have led to useful models of heart failure and atrial fibrillation. Unfortunately, molecular and genetic studies in these large animal models are often prohibitively expensive or not available. Conversely, the mouse is an excellent species for studying molecular mechanisms of cardiovascular disease through genetic engineering. However, the large size of available pacemakers does not lend itself to chronic pacing in mice. Here, we present the design for a novel, fully implantable wireless-powered pacemaker for mice capable of long-term (>30 days) pacing. This design is compared to a traditional battery-powered pacemaker to demonstrate critical advantages achieved through wireless inductive power transfer and control. Battery-powered and wireless-powered pacemakers were fabricated from standard electronic components in our laboratory. Mice (n = 24) were implanted with endocardial, battery-powered devices (n = 14) and epicardial, wireless-powered devices (n = 10). Wireless-powered devices were associated with reduced implant mortality and more reliable device function compared to battery-powered devices. Eight of 14 (57.1%) mice implanted with battery-powered pacemakers died following device implantation compared to 1 of 10 (10%) mice implanted with wireless-powered pacemakers. Moreover, device function was achieved for 30 days with the wireless-powered device compared to 6 days with the battery-powered device. The wireless-powered pacemaker system presented herein will allow electrophysiology studies in numerous genetically engineered mouse models as well as rapid pacing-induced heart failure and atrial arrhythmia in mice

Comparison of battery-powered and wireless-powered pacemakers.

<p>Comparison of battery-powered and wireless-powered pacemakers.</p

Assembly process of wireless powered pacemaker.

<p>(a) Platinum wire is attached to the circuit board, wound together, and coiled with a 0.5 cc syringe. (b) A bead of Silastic is placed on a piece of parafilm(1). The device is placed on the bead(2), coated with an additional layer of Silastic(3), and topped with a piece of gas permeable film(4). (c) Final product. (d) Artistic rendering of external transmitter interacting with abdominally implanted receiver in mouse.</p

Bench top and <i>in vivo</i> testing of battery powered pacemaker.

<p>(a) Current (blue) and voltage (gray) traces from the pacing catheter. (b) Frequency Response Analysis of distal and proximal pacing catheter electrodes (c) Lead II ECG recording in a mouse heart during sinus rhythm and right ventricular pacing by the battery-powered pacemaker over 5 days.</p

<i>In vivo</i> testing of wireless pacemaker.

<p>(a) Lead II ECG during normal sinus rhythm (top) and during LV apical pacing (bottom). (b) Pacing pulse width threshold of wireless device over 30 days for all mice with stable capture. Solid red line shows linear regression on mean pulse width thresholds. Dashed black lines show 95% confidence interval bounds for the regression.</p

Layout of the wireless-powered pacemaker.

<p>(a) Circuit layout of transmitter (top) and receiver (bottom). (b) Pulsed input into transmitter from pulse generator. (c) Output from transmitter. (d) Uncapped output from receiver. (e) Capped output from receiver. (f) Receiver output decreases minimally up to 5 cm from the transmitter coil. See text for further details.</p

Parts list for wireless transmitter and receiver circuits.

<p>Parts list for wireless transmitter and receiver circuits.</p