Generation of a Dcx-CreERT2 knock-in mouse for genetic manipulation of newborn neurons

A wide variety of CreERT2 driver lines are available for genetic manipulation of adult-born neurons in the mouse brain. These tools have been instrumental in studying fate potential, migration, circuit integration, and morphology of the stem cells supporting lifelong neurogenesis. Despite a wealth of tools, genetic manipulation of adult-born neurons for circuit and behavioral studies has been limited by poor specificity of many driver lines targeting early progenitor cells and by the inaccessibility of lines selective for later stages of neuronal maturation. We sought to address these limitations by creating a new CreERT2 driver line targeted to the endogenous mouse doublecortin locus as a marker of fate-specified neuroblasts and immature neurons. Our new model places a T2A-CreERT2 cassette immediately downstream of the Dcx coding sequence on the X chromosome, allowing expression of both Dcx and CreERT2 proteins in the endogenous spatiotemporal pattern for this gene. We demonstrate that the new mouse line drives expression of a Cre-dependent reporter throughout the brain in neonatal mice and in known neurogenic niches of adult animals. The line has been deposited with the Jackson Laboratory and should provide an accessible tool for studies targeting fate-restricted neuronal precursors.

Speg interactions that regulate the stability of excitation-contraction coupling protein complexes in triads and dyads

Here we show that striated muscle preferentially expressed protein kinase α (Spegα) maintains cardiac function in hearts with Spegβ deficiency. Speg is required for stability of excitation-contraction coupling (ECC) complexes and interacts with esterase D (Esd), Cardiomyopathy-Associated Protein 5 (Cmya5), and Fibronectin Type III and SPRY Domain Containing 2 (Fsd2) in cardiac and skeletal muscle. Mice with a sequence encoding a V5/HA tag inserted into the first exon of the Speg gene (HA-Speg mice) display a >90% decrease in Spegβ but Spegα is expressed at ~50% of normal levels. Mice deficient in both Spegα and Speg β (Speg KO mice) develop a severe dilated cardiomyopathy and muscle weakness and atrophy, but HA-Speg mice display mild muscle weakness with no cardiac involvement. Spegα in HA-Speg mice suppresses Ca2+ leak, proteolytic cleavage of Jph2, and disruption of transverse tubules. Despite it's low levels, HA-Spegβ immunoprecipitation identified Esd, Cmya5 and Fsd2 as Spegβ binding partners that localize to triads and dyads to stabilize ECC complexes. This study suggests that Spegα and Spegβ display functional redundancy, identifies Esd, Cmya5 and Fsd2 as components of both cardiac dyads and skeletal muscle triads and lays the groundwork for the identification of new therapeutic targets for centronuclear myopathy.

Delayed skeletal development and IGF-1 deficiency in a mouse model of lysinuric protein intolerance

SLC7A7 deficiency, or lysinuric protein intolerance (LPI), causes loss of function of the y+LAT1 transporter critical for efflux of arginine, lysine and ornithine in certain cells. LPI is characterized by urea cycle dysfunction, renal disease, immune dysregulation, growth failure, delayed bone age and osteoporosis. We previously reported that Slc7a7 knockout mice (C57BL/6×129/SvEv F2) recapitulate LPI phenotypes, including growth failure. Our main objective in this study was to characterize the skeletal phenotype in these mice. Compared to wild-type littermates, juvenile Slc7a7 knockout mice demonstrated 70% lower body weights, 87% lower plasma IGF-1 concentrations and delayed skeletal development. Because poor survival prevents evaluation of mature knockout mice, we generated a conditional Slc7a7 deletion in mature osteoblasts or mesenchymal cells of the osteo-chondroprogenitor lineage, but no differences in bone architecture were observed. Overall, global Slc7a7 deficiency caused growth failure with low plasma IGF-1 concentrations and delayed skeletal development, but Slc7a7 deficiency in the osteoblastic lineage was not a major contributor to these phenotypes. Future studies utilizing additional tissue-specific Slc7a7 knockout models may help dissect cell-autonomous and non-cell-autonomous mechanisms underlying phenotypes in LPI.

Electrograms guided his bundle pacing implant: moving from radiology to electrical signals

Background

The standard technique to His Bundle Pacing (HBP) based on a fluoroscopic approach might be challenging and fluoro consuming. The electrical signals could lead to a precise and rapid lead implant, thus reducing the fluoroscopy time (FT) and X-ray dose.

Objective

To evaluate the feasibility, efficacy and safety of the electrogram-guided technique to obtain His Bundle pacing (HBP) with minimal or no fluoroscopy use.

Methods

Between October and December 2018, 41 consecutive patients with indication for pacing underwent HBP with the electrogram-guided approach.

Results

Successful HBP was obtained in 39/41 (95%) pts, which is the study population (mean age 78±10 years). S-HBP and NS-HBP were achieved in 23 (59%) and 16 (41%) pts, respectively. Final HBP lead position was achieved in 31/39 (79.4%) pts with zero fluoroscopy, only guided by the electrical signals. In the remaining 8 pts a minimal dose of fluoro (mean 8 sec) has been required to locate the His. Fluoroscopy has been routinely used to remove the sheath and to ensure the slack. The atrial lead has been implanted in a standard fashion. No difference was observed in the FT for HBP lead placement in patients with S-HBP and NS-HBP (mean 8.1±25 sec vs 7.5±20 sec, p=0.8; median value 0 sec vs 0 sec). Moreover, no significant differences were observed in the FT needed for the entire procedure, total Dose Area Product (DAP) and total procedural time among both S-HBP and NS-HBP. The His lead dislodgement occurred in 1 (2.6%) patient one day after the procedure.

Conclusion

HBP could be performed safely and efficiently using the electrograms, with minimal or no fluoroscopy. Fluoroscopy was required during sheath removal and atrial lead placement.

Funding Acknowledgement

Type of funding source: None

The back-up lead in his bundle pacing: evolution over the years

Background

His bundle pacing (HBP) can be affected by high thresholds and low sensing. Thus, in selected patients including a back-up lead is advisable.

Objective

Single-centre retrospective analysis of a large HBP experience, focusing on the back-up lead utilization over the years.

Methods

677 pts (76±8 years; 433 males) were implanted with HBP from 2004 to 2019 July. The pts received S-HBP (67%) or NS-HBP by the 3830 lead. The pacing indications were AV block 54%, sinus node disease 17%, slow atrial fibrillation 23%, heart failure 6%. Ischemic cardiopathy was found in 26%; hypertension in 83%, diabetes in28% pts. Baseline QRS duration was 123±32 ms and EF 56±12%.

Results

266 (39%) pts received the back-up lead. In sinus rhythm we implanted 3-chamber PM (His lead:LV port; VV delay 80 ms: His pulses and apical pacing during the refractory period). 30 pts (11%) received a particular type of 3-chamber PM which provides back-up pacing only if His capture fails, thus saving energy. In atrial fibrillation 2-chamber PM was implanted (His lead: atrial port, DVI). We recorded a significant decrease of back-up lead use over the years, strictly related to operators/centre experience (>70% during the first years, nearly 10% during the last year). The C315 fixed curve sheath, strongly contributed to the rapid reduction of back-up lead use thanks to better lead fixation and stability.

Conclusion

The back-up lead utilization is progressively decreasing. It is strictly related to the operator/centre experience. The presence of the back-up lead could strengthen the Hisian pacing reliability, potentially impacting pacing indication even in advanced conduction disturbances and saving device longevity.

Funding Acknowledgement

Type of funding source: None

A global Slc7a7 knockout mouse model demonstrates characteristic phenotypes of human lysinuric protein intolerance

Lysinuric protein intolerance (LPI) is an inborn error of cationic amino acid (arginine, lysine, ornithine) transport caused by biallelic pathogenic variants in SLC7A7, which encodes the light subunit of the y+LAT1 transporter. Treatments for the complications of LPI, including growth failure, renal disease, pulmonary alveolar proteinosis, autoimmune disorders and osteoporosis, are limited. Given the early lethality of the only published global Slc7a7 knockout mouse model, a viable animal model to investigate global SLC7A7 deficiency is needed. Hence, we generated two mouse models with global Slc7a7 deficiency (Slc7a7em1Lbu/em1Lbu; Slc7a7Lbu/Lbu and Slc7a7em1(IMPC)Bay/em1(IMPC)Bay; Slc7a7Bay/Bay) using CRISPR/Cas9 technology by introducing a deletion of exons 3 and 4. Perinatal lethality was observed in Slc7a7Lbu/Lbu and Slc7a7Bay/Bay mice on the C57BL/6 and C57BL/6NJ inbred genetic backgrounds, respectively. We noted improved survival of Slc7a7Lbu/Lbu mice on the 129 Sv/Ev × C57BL/6 F2 background, but postnatal growth failure occurred. Consistent with human LPI, these Slc7a7Lbu/Lbu mice exhibited reduced plasma and increased urinary concentrations of the cationic amino acids. Histopathological assessment revealed loss of brush border and lipid vacuolation in the renal cortex of Slc7a7Lbu/Lbu mice, which combined with aminoaciduria suggests proximal tubular dysfunction. Micro-computed tomography of L4 vertebrae and skeletal radiographs showed delayed skeletal development and suggested decreased mineralization in Slc7a7Lbu/Lbu mice, respectively. In addition to delayed skeletal development and delayed development in the kidneys, the lungs and liver were observed based on histopathological assessment. Overall, our Slc7a7Lbu/Lbu mouse model on the F2 mixed background recapitulates multiple human LPI phenotypes and may be useful for future studies of LPI pathology.

P6547The energy cost of His bundle pacing can be curtailed

Introduction

His bundle pacing (HBP) allows physiological ventricular activation and prevents the electrical and mechanical desynchronization generally induced by myocardial stimulation, which can increase the risk of atrial fibrillation and heart failure. On the other hand, reliable HBP capture often requires higher energy than conventional myocardial pacing. This reduces the expected life of the stimulator and might limit the diffusion of HBP in the clinical practice.

Purpose

Decreasing HBP current drain by careful management of stimulation safety margin and pulse duration.

Methods

In 28 patients undergoing DDD pacing with HBP, a third lead was implanted in RV apex to provide back-up pacing on demand. HBP and apical leads were connected, respectively, to the V1 and V2 channels of a 3-chamber stimulator. When HBP was effective, apical sensing occurred within the VV delay and prevented V2 stimulation. In contrast, in case of HBP failure, V2 sensing was missing and apical back-up pacing was promptly delivered at the end of the VV delay. The availability of a back-up pulse on demand allowed reducing the HBP safety margin with no risk. Furthermore, the individual HBP strength-duration curve was derived in the aim of optimizing the Hisian pulse parameters, which are the major determinants of the device current drain.

Results

Correct back-up inhibition by successful HBP and stimulation in the event of capture loss was achieved in all the patients. The latency from Hisian pacing to apical sensing averaged 96±14 ms. According to the pacemaker counters, no back-up pulse was delivered in daily life in 59% of patients. In the remaining, the prevalence of back-up stimulation never exceeded 15% of paced ventricular cycles. The high HBP threshold was essentially due to an increased rheobase (1.2±0.6 V), while the chronaxie ranged from 0.30 to 0.53 ms in 71% of patients (median 0.44 ms), exceeding 0.6 ms only in 29% of the cases. An average current saving of 5.4±3.0 μA was obtained at the expense of a mild reduction in HBP safety margin (from 1.6±0.2 to 1.4±0.1 times).

HBP and apical back-up

Conclusions

Back-up stimulation on demand is a reliable option to decrease HBP current drain and prolong the stimulator service life with full safety. In most of the cases, significant saving can be achieved by pulse shortening, as the chronaxie time is in the same range as with myocardial stimulation and longer pulses are not required. A pulse duration exceeding 0.6 ms is indicated in less than 1/3 of the implants.

CRISPR/Cas9-mediated deletion of lncRNA Gm26878 in the distant Foxf1 enhancer region

Recent genome editing techniques, including CRISPR mutagenesis screens, offer unparalleled opportunities to study the regulatory non-coding genomic regions, enhancers, promoters, and functional non-coding RNAs. Heterozygous point mutations in FOXF1 and genomic deletion copy-number variants at chromosomal region 16q24.1 involving FOXF1 or its regulatory region mapping ~300 kb upstream of FOXF1 and leaving it intact have been identified in the vast majority of patients with a lethal neonatal lung disease, alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV). Homozygous Foxf1 ^-/- mice have been shown to die by embryonic day 8.5 because of defects in the development of extraembryonic and lateral mesoderm-derived tissues, whereas heterozygous Foxf1 ^+/- mice exhibit features resembling ACDMPV. We have previously defined a human lung-specific enhancer region encoding two long non-coding RNAs, LINC01081 and LINC01082, expressed in the lungs. To investigate the biological significance of lncRNAs in the Foxf1 enhancer region, we have generated a CRISPR/Cas9-mediated ~2.4 kb deletion involving the entire lncRNA-encoding gene Gm26878, located in the mouse region syntenic with the human Foxf1 upstream enhancer. Very recently, this mouse genomic region has been shown to function as a Foxf1 enhancer. Our results indicate that homozygous loss of Gm26878 is neonatal lethal with low penetrance. No changes in Foxf1 expression were observed, suggesting that the regulation of Foxf1 expression differs between mouse and human.

[Integration of new nurses in nursing units in a university hospital]

The study presented in this article raises the problems of the integration of recently graduated nurses in the hospital from the point of view of a culture difference between the two socialisation worlds: more reflexive standards of behaviour and culture in the schools (emphasis on analysis, knowledge, care actions argumentation...) and more instrumental ones in the hospitals (emphasis on efficiency, work organisation, operationality...). An enquiry by means of interviews with recent graduates from different schools (open, semi-open and closed questions) enables to successively analyse the skills they consider to have acquired at school, the ones they consider as required by the hospital and the differences they feel between hospital and school concerning the enhanced skills. The results show a significant discrepancy between the ideal of the interviewed nurses and the reality of their work within the institutional constraints of the hospital.

Long-term results of functional endoscopic sinus surgery

Although much has been reported on the short-term outcomes of functional endoscopic sinus surgery (FESS), little has been reported with regard to its long-term impact on chronic sinusitis. The senior author (D.W.K.) previously reported detailed subjective and endoscopic follow-up on 120 patients at a mean of 18 months following surgery. This current study represents a long-term follow-up (average, 7.8 years) of 72 patients (60%) from the same cohort. Of patients responding to a question about overall symptoms, 98.4% (n = 66) reported improvement compared with before surgery. There was a trend toward continued subjective improvement in symptom scores with longer follow-up, but the changes did not reach statistical significance. Thirteen patients (18%) required subsequent surgical procedures. Preoperative stage, prior surgery, and other factors that might affect outcome were evaluated. The study demonstrates that excellent subjective results following FESS can be maintained in the long term with appropriate postoperative management. The study also validates the concept that patients in whom the cavity can be normalized following surgery are unlikely to require further surgery.

Nasal airway changes assessed by acoustic rhinometry and mediator release during immediate and late reactions to allergen challenge

BACKGROUND

We have found that acoustic rhinometry is a reliable means of assessing nasal airway caliber changes during the immediate reaction to nasal allergen challenge of sensitive subjects. Comparison of such changes with symptoms and patterns of mediator release could help in the understanding of mechanisms of immediate and late-phase reactions after allergen challenge and their clinical relevance.

METHODS

Nasal minimal cross-sectional area (MCA) was assessed sequentially for 6 hours after two blinded challenges in random order with pollen antigens and buffer diluent in five sensitive human subjects. Comparisons were made with: (1) symptom scores; (2) olfaction changes; and (3) nasal secretion levels of histamine, tryptase, leukotriene C4, serum albumin (a marker of vascular permeability), lactoferrin (a marker of local glandular secretion), and inflammatory cells in nasal scrapings.

RESULTS

In four of five subjects there was a significantly greater decrease in MCA after antigen challenge than after diluent challenge, correlating with the degree of subjective nasal congestion. In two of these four subjects there was a prominent second late-phase decrease in MCA at 3 to 5 hours, whereas the MCA was persistently decreased in an additional subject with accompanying subjective congestion. No significant decrease in olfactory acuity occurred. Levels were significantly higher in nasal secretions obtained after antigen challenge than in those obtained after buffer challenge with histamine (9 +/- 2.7 ng/ml vs 1.2 +/- 0.5 ng/ml; p = 0.04); tryptase (95 +/- 83 ng/ml vs 3 +/- 0.9 ng/ml; p = 0.02), leukotriene C4 (5293 +/- 1385 ng/ml vs 578 +/- 183 ng/ml; p = 0.02), and albumin (123 +/- 9 ng/ml vs 19 +/- 1.6 ng/ml; p = 0.005) but not with lactoferrin (4.6 +/- 1.2 ng/ml vs 4.1 +/- 28 ng/ml; p = not significant). Granulocyte exudation was seen after antigen challenge but not after buffer diluent challenge. However, there was not a precise correlation between decreases in MCA with changes in levels of these mediators in individual subjects.

CONCLUSIONS

Acoustic rhinometry can quantitatively assess congestion during immediate and late-phase reactions after nasal challenge without significant correlation to the degree of individual inflammatory events assessed.

Head and neck manifestations of plasma cell neoplasms

Multiple myeloma, solitary plasmacytoma of bone, and extramedullary plasmacytoma are plasma cell neoplasms. They represent distinct manifestations of a disease continuum, whereby the clinical findings are critical to diagnosis. Plasma cell neoplasms are histologically similar, and distinguishing one from the other has significant implications for treatment and survival. Plasma cell neoplasms are relatively unusual malignancies of the head and neck region. We present a case series of plasma cell neoplasms involving the skull base, paranasal sinus, larynx, and mandible as an introduction to a complete review of the literature on plasma cell neoplasms of the head and neck area.

Use of stress thallium imaging to stratify cardiac risk in patients undergoing vascular surgery

Reduction of the cardiac morbidity associated with major vascular procedures requires identification of high risk patients prior to operation. This retrospective study reviews the records of 126 consecutive patients who underwent 141 major vascular procedures to determine the accuracy of preoperative clinical, laboratory (ECG), and cardiac function testing (stress thallium-201 scintigraphy, left ventricular ejection fraction scan) in predicting perioperative cardiac complications. An abnormality on oral dipyridamole or treadmill thallium imaging was demonstrated prior to 71 (61%) of 116 procedures and included 20 fixed and 51 reperfusion (reversible) defects. No patient died within 30 days of operation, but 11 minor (ventricular arrhythmia) and 15 major (myocardial infarction, ischemic congestive heart failure) cardiac complications occurred. A reperfusion defect on stress thallium imaging accurately (94% sensitivity, 56% specificity, 98% negative predictive value) identified high-risk patients while accepted clinical rating systems (Goldman, Cooperman, Eagle) and preoperative level of left ventricular ejection fraction were less predictive of adverse cardiac events. Patients without myocardium at risk by coronary angiography, but a reperfusion defect on stress thallium imaging were found to be at high risk for a cardiac complication. The study data support the use of stress thallium imaging to stratify cardiac risk prior to major arterial surgery.

Monitoring functional patency of percutaneous transluminal angioplasty

Duplex scanning and Doppler-derived blood pressure measurements were used to serially monitor lower limb hemodynamics in 73 patients who underwent percutaneous transluminal angioplasty. Ninety percutaneous transluminal angioplasty sites judged technically satisfactory by arteriography were evaluated. Significant hemodynamic improvement was seen in 81 (90%) of the 90 limbs, although both hemodynamic and clinical improvement were achieved in only 77 (86%) limbs. Duplex scanning within 1 week of successful angioplasty identified moderate (20% to 49% diameter reduction) or severe (greater than 50% diameter reduction) residual stenosis in 49 (63%) of 77 balloon-dilated arterial segments. The presence of a greater than 50% diameter reduction residual stenosis predicted further restenosis and late clinical failure (11% success rate at 1 year). When the degree of residual stenosis at the percutaneous transluminal angioplasty site was less than 50% diameter reduction by duplex scanning, the procedure was durable (80% success rate at 2 years), even in patients with critical ischemia, poor runoff, or diabetes mellitus.