Meet the authors: Jonathan Philpott and Carrie L. Partch.

Here, Molecular Cell talks to first author Jonathan Philpott and co-corresponding author Carrie Partch about their paper, "PERIOD phosphorylation leads to feedback inhibition of CK1 activity to control circadian period" (in this issue of Molecular Cell) and their scientific journeys until now.

PERIOD phosphorylation leads to feedback inhibition of CK1 activity to control circadian period.

PERIOD (PER) and Casein Kinase 1δ regulate circadian rhythms through a phosphoswitch that controls PER stability and repressive activity in the molecular clock. CK1δ phosphorylation of the familial advanced sleep phase (FASP) serine cluster embedded within the Casein Kinase 1 binding domain (CK1BD) of mammalian PER1/2 inhibits its activity on phosphodegrons to stabilize PER and extend circadian period. Here, we show that the phosphorylated FASP region (pFASP) of PER2 directly interacts with and inhibits CK1δ. Co-crystal structures in conjunction with molecular dynamics simulations reveal how pFASP phosphoserines dock into conserved anion binding sites near the active site of CK1δ. Limiting phosphorylation of the FASP serine cluster reduces product inhibition, decreasing PER2 stability and shortening circadian period in human cells. We found that Drosophila PER also regulates CK1δ via feedback inhibition through the phosphorylated PER-Short domain, revealing a conserved mechanism by which PER phosphorylation near the CK1BD regulates CK1 kinase activity.

Biochemical mechanisms of period control within the mammalian circadian clock.

Genetically encoded biological clocks are found broadly throughout life on Earth, where they generate circadian (about a day) rhythms that synchronize physiology and behavior with the daily light/dark cycle. Although the genetic networks that give rise to circadian timing are now fairly well established, our understanding of how the proteins that constitute the molecular 'cogs' of this biological clock regulate the intrinsic timing, or period, of circadian rhythms has lagged behind. New studies probing the biochemical and structural basis of clock protein function are beginning to reveal how assemblies of dedicated clock proteins form and evolve through post-translational regulation to generate circadian rhythms. This review will highlight some recent advances providing important insight into the molecular mechanisms of period control in mammalian clocks with an emphasis on structural analyses related to CK1-dependent control of PER stability.

Massive intercostal hemorrhage after implantation of an intrapericardial ventricular assist device: A case report.

Left ventricular assist devices (LVADs) have become integral to the treatment of advanced heart failure. Surgical bleeding is a known complication of LVAD placement but is most associated with intraperitoneal pump locations. Here we describe a case of massive postoperative hemorrhage secondary to erosion of an intrapericardial LVAD into an intercostal artery with an associated rib fracture.

Surgical Ablation of Cardiac Tissue with Nanosecond Pulsed Electric Fields in Swine.

BACKGROUND: Myocardial tissue can be ablated by the application nanosecond pulsed fields (nsPEFs). The applied electric fields irreversibly permeabilize cell membranes and thereby kill myocytes while leaving the extracellular matrix intact. METHODS: In domestic pigs (n = 10), hearts were exposed via sternotomy and either ablated in vivo ([Formula: see text] = 5) or in excised, Langendorff-perfused hearts ([Formula: see text] = 5). The nsPEFs consisted of 6-36 pulses of 300 ns each, delivered at 3-6 Hz; the voltage applied varied from 10 to 12 kV. Atrial lesions were either created after inserting the bottom jaw of the bipolar clamp into the atrium via a purse string incision (2-3 lesions per atrium) or by clamping a double layer of tissue at the appendages (one lesion per atrium). Ventricular lesions were created after an incision at the apex. The transmurality of each lesion was determined at three points along the lesion using a triphenyl tetrazolium chloride (TTC) stain. RESULTS: All 27 atrial lesions were transmural. This includes 13/13 purse string lesions (39/39 sections, tissue thickness 2.5-4.5 mm) and 14/14 appendage lesions (42/42 sections, tissue thickness 8-12 mm). All 3 right ventricular lesions were transmural (9/9 sections, 18 pulses per lesion). Left ventricular lesions were always transmural for 36 pulses (3/3 lesions, 9/9 sections). All lesions have highly consistent width across the wall. There were no pulse-induced arrhythmias or other complications during the procedure. CONCLUSIONS: nsPEF ablation reliably created acute lesions in porcine atrial and ventricular myocardium. It has far better penetration and is faster than both radiofrequency ablation and cryoablation and it is free from thermal side effects.

Casein kinase 1 dynamics underlie substrate selectivity and the PER2 circadian phosphoswitch.

Post-translational control of PERIOD stability by Casein Kinase 1δ and ε (CK1) plays a key regulatory role in metazoan circadian rhythms. Despite the deep evolutionary conservation of CK1 in eukaryotes, little is known about its regulation and the factors that influence substrate selectivity on functionally antagonistic sites in PERIOD that directly control circadian period. Here we describe a molecular switch involving a highly conserved anion binding site in CK1. This switch controls conformation of the kinase activation loop and determines which sites on mammalian PER2 are preferentially phosphorylated, thereby directly regulating PER2 stability. Integrated experimental and computational studies shed light on the allosteric linkage between two anion binding sites that dynamically regulate kinase activity. We show that period-altering kinase mutations from humans to Drosophila differentially modulate this activation loop switch to elicit predictable changes in PER2 stability, providing a foundation to understand and further manipulate CK1 regulation of circadian rhythms.

Metastatic Hurthle Cell Carcinoma of the thyroid presenting as a Breast Lump: A Case Report.

BACKGROUND: Hurthle cell carcinoma of the thyroid is a rare form of thyroid cancer. It may present as a low grade tumour or can present as a more aggressive metastatic carcinoma. Hurthle cell carcinoma has the highest incidence of metastasis among all differentiated thyroid cancers. Most commonly haematogenous spread to lungs, bones and brain, however spread to regional lymph nodes is not uncommon. The breast is a rare site for metastasis from extramammary sources. We present the first case of breast metastasis from Hurthle cell carcinoma of the thyroid. CASE PRESENTATION: We report a 77 year old lady who had total thyroidectomy and bilateral neck dissection followed by radiotherapy for a high grade metastatic Hurthle cell carcinoma of the thyroid. Ten months later she presented to the breast clinic with left breast lump and a lump at the left axilla. Fine needle aspiration cytology of the lumps and histology after wide local excision of the breast lump confirmed metastatic Hurthle cell carcinoma. CONCLUSION: The presence of breast lumps in patients with history of extramammary cancer should raise the possibility of metastasis.

Low-energy defibrillation with nanosecond electric shocks.

AIMS: Reliable defibrillation with reduced energy deposition has long been the focus of defibrillation research. We studied the efficacy of single shocks of 300 ns duration in defibrillating rabbit hearts as well as the tissue damage they may cause. METHODS AND RESULTS: New Zealand white rabbit hearts were Langendorff-perfused and two planar electrodes were placed on either side of the heart. Shocks of 300 ns duration and 0.3-3 kV amplitude were generated with a transmission line generator. Single nanosecond shocks consistently induced waves of electrical activation, with a stimulation threshold of 0.9 kV (over 3 cm) and consistent activation for shock amplitudes of 1.2 kV or higher (9/9 successful attempts). We induced fibrillation (35 episodes in 12 hearts) and found that single shock nanosecond-defibrillation could consistently be achieved, with a defibrillation threshold of 2.3-2.4 kV (over 3 cm), and consistent success at 3 kV (11/11 successful attempts). Shocks uniformly depolarized the tissue, and the threshold energy needed for nanosecond defibrillation was almost an order of magnitude lower than the energy needed for defibrillation with a monophasic 10 ms shock delivered with the same electrode configuration. For the parameters studied here, nanosecond defibrillation caused no baseline shift of the transmembrane potential (that could be indicative of electroporative damage), no changes in action potential duration, and only a brief change of diastolic interval, for one beat after the shock was delivered. Histological staining with tetrazolium chloride and propidium iodide showed that effective defibrillation was not associated with tissue death or with detectable electroporation anywhere in the heart (six hearts). CONCLUSION: Nanosecond-defibrillation is a promising technology that may allow clinical defibrillation with profoundly reduced energies.

The Society of Thoracic Surgeons 2017 Clinical Practice Guidelines for the Surgical Treatment of Atrial Fibrillation.

EXECUTIVE SUMMARY: Surgical ablation for atrial fibrillation (AF) can be performed without additional risk of operative mortality or major morbidity, and is recommended at the time of concomitant mitral operations to restore sinus rhythm. (Class I, Level A) Surgical ablation for AF can be performed without additional operative risk of mortality or major morbidity, and is recommended at the time of concomitant isolated aortic valve replacement, isolated coronary artery bypass graft surgery, and aortic valve replacement plus coronary artery bypass graft operations to restore sinus rhythm. (Class I, Level B nonrandomized) Surgical ablation for symptomatic AF in the absence of structural heart disease that is refractory to class I/III antiarrhythmic drugs or catheter-based therapy or both is reasonable as a primary stand-alone procedure, to restore sinus rhythm. (Class IIA, Level B randomized) Surgical ablation for symptomatic persistent or longstanding persistent AF in the absence of structural heart disease is reasonable, as a stand-alone procedure using the Cox-Maze III/IV lesion set compared with pulmonary vein isolation alone. (Class IIA, Level B nonrandomized) Surgical ablation for symptomatic AF in the setting of left atrial enlargement (≥4.5 cm) or more than moderate mitral regurgitation by pulmonary vein isolation alone is not recommended. (Class III no benefit, Level C expert opinion) It is reasonable to perform left atrial appendage excision or exclusion in conjunction with surgical ablation for AF for longitudinal thromboembolic morbidity prevention. (Class IIA, Level C limited data) At the time of concomitant cardiac operations in patients with AF, it is reasonable to surgically manage the left atrial appendage for longitudinal thromboembolic morbidity prevention. (Class IIA, Level C expert opinion) In the treatment of AF, multidisciplinary heart team assessment, treatment planning, and long-term follow-up can be useful and beneficial to optimize patient outcomes. (Class I, Level C expert opinion).

The ABLATE Trial: Safety and Efficacy of Cox Maze-IV Using a Bipolar Radiofrequency Ablation System.

BACKGROUND: The Cox Maze-IV procedure (CMP-IV) has replaced the Cox Maze-III procedure as the most common approach for the surgical treatment of atrial fibrillation (AF). The Food and Drug Administration-regulated AtriCure Bipolar Radiofrequency Ablation of Permanent Atrial Fibrillation (ABLATE) trial sought to demonstrate the safety and efficacy of the CMP-IV performed with the Synergy ablation system (AtriCure, Inc, Cincinnati, OH). METHODS: Fifty-five patients (aged 70.5 ± 9.3 years), 92.7% of whom had nonparoxysmal AF, underwent CMP-IV to terminate AF during a concomitant cardiac surgical procedure. Lesions were created using the AtriCure Synergy bipolar radiofrequency ablation system. All patients were seen for follow-up visits after 30 days, 3 months, and 6 months, with 24-hour Holter monitoring at 6 months. Late evaluation was performed by 48-hour Holter monitoring at an average of 21 months. RESULTS: The primary efficacy endpoint, absence of AF (30 seconds or less) at 6-month follow-up off antiarrhythmic medications (Heart Rhythm Society definition), indicated 76% (38 of 50) were AF free (95% confidence interval: 62.6% to 85.7%). The primary safety endpoint, the rate of major adverse events within 30 days, was 9.1% (5 of 55; 95% confidence interval: 3.9% to 19.6%), with 3.6% mortality (2 of 55). Secondary efficacy endpoints included being AF free with antiarrhythmic drugs (6 months, 84%; 21 months, 75%), successful pulmonary vein isolation (100%), and AF burden at 6 and 21 months. The results, together with those for the secondary safety endpoint (6-month major adverse events), demonstrated that the Synergy system performs comparably to the cut-and-sew Cox Maze-III procedure. CONCLUSIONS: The CMP-IV using the AtriCure Synergy system was safe and effective for cardiac surgical patients who had persistent and longstanding persistent AF.

Combined minimally invasive mitral valve repair and direct coronary artery bypass: a new alternative to sternotomy.

A case is presented in which significant single-vessel coronary artery disease and severe mitral valve regurgitation were successfully managed using combined minimally invasive direct coronary artery bypass and mitral valve repair. Although the management of coronary artery disease with simultaneous mitral valve disease has traditionally been approached using a median sternotomy, this combined minimally invasive approach led to a successful outcome and may serve as an alternative methodology for patients who are appropriate candidates.

Isolated internal iliac artery aneurysm resection and reconstruction: operative planning and technical considerations.

Isolated iliac artery aneurysms are rare but dangerous aneurysms associated with a high incidence of rupture (between 14 and 70%). Rupture is frequently associated with an exceedingly high mortality primarily because of the elusive nature of the presenting symptoms and the resulting major delays in treatment. Accordingly these aneurysms are best managed aggressively. Although emerging endovascular techniques show promise surgical resection and reconstruction remains the gold standard for definitive management and has withstood the test of time with excellent durable and unparalleled results. That said, from an operative perspective these aneurysms are technically demanding and remain one of the more formidable technical challenges in vascular surgery. To highlight the key elements involved in a successful repair we present a right internal iliac artery aneurysm with an associated contralateral common iliac artery occlusion, review the necessary preoperative planning and the available surgical treatment options, and detail the technical steps leading to a successful reconstruction. Careful operative planning is critical. Inadequate preoperative studies, inadequate preoperative decision making, and a poorly formulated operative strategy can lead to catastrophic results. Some of the most feared complications include pelvic venous injury with resulting massive hemorrhage and postoperative pelvic ischemia (with resulting rectal and/or spinal cord ischemia) which occurs as a result of inadequate contralateral collateral pelvic blood flow when the internal iliac artery is not reimplanted. Accordingly the preoperative workup must include a careful analysis of the adequacy of the contralateral pelvic blood flow to supply collateral flow in the event that the internal iliac is not reimplanted. In the presence of compromised contralateral internal iliac perfusion, resection and reconstruction or an alternative form of pelvic revascularization is mandatory. Excellent and unencumbered exposure is mandatory for a safe and successful repair. The retroperitoneal approach as illustrated in this case is strongly recommended. Although it is challenging excellent results can be achieved by resection of the aneurysm and reconstruction.

Onlay patch for complete intercostal artery preservation during thoracic and thoracoabdominal aortic aneurysm repair.

BACKGROUND: Replacement of the thoracic aorta is associated with a potential for interruption of the blood supply to the spinal cord leading to paralysis. Techniques have been proposed to ameliorate this risk, including reimplantation of the intercostal arteries. We present a technique to simplify this approach. METHODS: In patients with extensive aneurysmal disease, a standard approach to the thoracic aorta via a left thoracotomy is performed. The patient is placed on full cardiopulmonary bypass with moderate hypothermia. The proximal anastomosis is performed unclamped with circulatory arrest. After completing the proximal and distal anastomosis separately, an onlay patch of Dacron is created and placed along the entire back wall of the aorta to cover all of the intercostal arteries. A side-to-side anastomosis between the patch and the distal graft is then performed and subsequently the anastomosis tested by retrograde flow. RESULTS: The technique allows direct inspection of all suture lines, tested to an adequate pressure, so that postoperative bleeding is minimal. CONCLUSION: Techniques to lessen the risk of paraplegia associated with aortic surgery include reimplantation of the intercostal arteries. This technique allows each suture line to be tested and easily visually inspected prior to closure of the chest.

Ureteral stenting in the management of urinoma after severe blunt renal trauma in children.

Posttraumatic urinomas are well-described complications associated with the nonoperative management of major blunt renal injuries. Urinoma drainage using a percutaneously placed catheter has been the traditional method used to alleviate symptoms and promote resolution without the need for open intervention. The authors describe 2 pediatric cases in which urinomas associated with grade IV renal lacerations were treated successfully utilizing internal ureteral stents.