Compact Zone Research Articles

Growing Academic Physiatry: The Impact of the Baruch's Grants on Harvard Medical School and Columbia College of Physicians and Surgeons. Part II.

Growing Academic Physiatry: The Impact of the Baruch's Grants on Harvard Medical School and Columbia College of Physicians and Surgeons. Part II.

A study of a quasilinear model of the particles of a suspension that are aggregated and settled in an inhomogeneous field

The mathematical model of the sedimentation process of suspension particles is usually a quasilinear hyperbolic system of partial differential equations, supplemented by initial and boundary conditions. In this work, we study a complex model that takes into account the aggregation of particles and the inhomogeneity of the field of external mass forces. The case of homogeneous initial conditions is considered, when all the parameters of the arising motion depend on only one spatial Cartesian coordinate x and on time t. In contrast to the known formulations for quasilinear systems of equations (for example, as in gas dynamics), the solutions of which contain discontinuities, in the studied formulation the basic system of equations occurs only on one side of the discontinuity line in the plane of variables (t; x). On the opposite side of the discontinuity surface, the equations have a different form in general. We will restrict ourselves to considering the case when there is no motion in a compact zone occupied by settled particles, i.e. all velocities are equal to zero and the volumetric contents of all phases do not change over time. The problem of erythrocyte sedimentation in the field of centrifugal forces in a centrifuge, with its uniform rotation with angular velocity ω = const is considered. We have studied the conditions for the existence of various types of solutions. One of the main problems is the evolution (stability) problem of the emerging discontinuities. The solution of this problem is related to the analysis of the relationships for the characteristic velocities and the velocity of the discontinuity surface. The answer depends on the number of characteristics that come to the jump, and the number of additional conditions set on the interface. The discontinuity at the lower boundary of the area occupied by pure plasma is always stable. But for the surface separating the zones of settled and of moving particles, the condition of evolution may be violated. In this case, it is necessary to adjust the original mathematical model.

Solid Waste Management and Incineration Practice: A Study of Bangladesh

Considering the geographical location and one of the very densely populated countries in the world, Bangladesh is very vulnerable to climate change and its adaptability. This paper has been designed with an attempt to inform the policy maker of Bangladesh regarding the potentiality of MSW as a renewable source of energy in Bangladesh. It deals with modern waste collection, management and incineration practices based on densely populated cities or towns like Bogura Municipality and Chattogram City Corporation. Waste to Energy (WtE) conversions not only reduce the land pressure problem in urban areas, but also generate electricity and heat to supply to the surrounding urban areas. The increase in generation of methane (CH4) from municipal solid wastes (MSW) alarms the world to take suitable initiative for the sustainable management of MSW, as it is stronger than carbon dioxide (CO2). By burning one mole of CH4, 890 kJ·mol-1 heat is produced which is a major source of energy. This treatment technology is used in destruction of solid waste by controlled burning at high temperatures. With the release of heat, it can be accompanied and this heat from combustion can be converted into energy. This type of incineration is a high-quality treatment for Municipal or City Corporation solid waste like Bangladesh where were over crowded cities, towns and it can reduce the quantity and volume of a large amount of waste to landfill, which can recover energy and dispose in the compact zone. The results also examined that the total amount of solid waste produced in Bogura municipality is lower than that of Chattogram City Corporation. The percentage compositions of waste patterns are shown in both the Cities. The paper discusses these problems, analyses and finally, a recommendation has been proposed in order to understand the industrial situation enhanced.

The entropy wave generation in a heated one-dimensional duct

This paper presents a theoretical analysis on entropy wave generation in a heated one-dimensional duct, which is a simple thermoacoustic model of a combustor. Following a new observation that an entropy wave is caused by the fluctuations of heat/flow power ratio, the entropy transport equation is analytically solved for a heat input uniformly distributed over an acoustically compact zone. Investigating transfer functions from heat and acoustic fluctuations to the entropy wave, we obtain a deeper understanding on the low-pass filtering property of entropy waves with a closed-form expression of the entropic cutoff frequency. A theoretical explanation on why a thinner flame generally results in a stronger entropy wave is also given. These findings are extended to a general flame distribution from a temporal-spatial filtering interpretation of the entropy transport equation. Furthermore, the thin flame limits of our entropy wave models are compared with a popular entropy model based on the thin flame assumption and jump conditions. A numerical example supporting our theoretical findings is also presented.

Inversions of time-domain spectral induced polarization data using stretched exponential

SUMMARY We provide a two-stage approach to extract spectral induced polarization (SIP) information from time-domain IP data. In the first stage we invert dc data to recover the background conductivity. In the second, we solve a linear inverse problem and invert all time channels simultaneously to recover the IP parameters. The IP decay curves are represented by a stretched exponential (SE) rather than the traditional Cole–Cole model, and we find that defining the parameters in terms of their logarithmic values is advantageous. To demonstrate the capability of our simultaneous SIP inversion we use synthetic data simulating a porphyry mineral deposit. The challenge is to image a mineral body that is hosted within an alteration halo having the same chargeability but a different time constant. For a 2-D problem, we were able to distinguish the body using our simultaneous inversion but we were not successful in using a sequential (or conventional) SIP inversion approach. For the 3-D problem we recovered 3-D distributions of the SIP parameters and used those to construct a 3-D rock model having four rock units. Three chargeable units were distinguished. The compact mineralization zone, having a large time constant, was distinguished from the circular alteration halo that had a small time constant. Finally, to promote the use of the SIP technique, and to have further development of SIP inversion, all examples presented in this paper are available in our open source resources (https://github.com/simpeg-research/kang-2018-spectral-inducedpolarization).

High-Frequency Ground Motion and Source Characteristics of the 2008 Wenchuan and 2013 Lushan, China, Earthquakes

The 2008 MW7.9 Wenchuan and the 2013 MW6.6 Lushan earthquakes, which both occurred on the Longmen Shan thrust belt, show some interesting similarities and differences. Whereas the Wenchuan earthquake entailed a rupture zone that extended about 300 km northeastward, with fault slip extending to the surface, the Lushan earthquake was the result of a buried and much more compact zone of rupture. The high-frequency ground motions, however, for these two earthquakes, as measured by the peak ground acceleration, were evidently influenced by neither the extent of rupture nor the presence or absence of surface rupture. The source parameters for these two earthquakes tend to confirm the idea that high-frequency ground motion is controlled by stress changes in the rupture zone that give rise to the radiated ground acceleration. The apparent stresses for the Wenchuan and Lushan earthquakes are about 0.5 and 0.75 MPa, respectively, and the stress drops, in the same order, are about 2.5 and 3.5 MPa. The ratios of average stress drop to apparent stress are in the range 4.5–5 for both events, consistent with expectations based on the Brune (J Geophys Res 75(26):4997–5009, 1970) source model.

Effect of rheumatoid arthritis and age on metacarpal bone shaft geometry and density: A longitudinal pQCT study in postmenopausal women

ObjectiveThis study aimed to elucidate the effects of changes in the geometry and density of the metacarpal bone of patients with rheumatoid arthritis (RA). MethodsThis prospective study included consecutive postmenopausal RA patients who met the American College of Rheumatology Criteria and healthy controls (HC). Peripheral quantitative computed tomography scans at 50% of the total metacarpal shaft (third metacarpal bone) were obtained at baseline and follow-ups. Use of bisphosphonates (BP), glucocorticoids (GC), biologics, and disease-modifying anti-rheumatic drugs (DMARD) was monitored (baseline to follow-up). Total cross-sectional area (CSA), cortical-transitional zone and compact zone CSA, cortical volumetric bone mineral density, and compact cortex porosity were measured. A linear mixed-effects model was used to determine significant differences in the rate of change in the RA and control groups and in RA patient subgroups. ResultsThirty-nine RA patients and 42 consecutive postmenopausal HC were followed for 63 months. RA and HC depicted a time-dependent increase of medullary CSA (+0.41 mm2/year, P < 0.0001), while total CSA remained stable (P = 0.2). RA status was associated with a loss of cortical bone mineral density (interaction: −3.08 mg/mm3; P = 0.014). In RA subgroup analysis, GC use ≥5 mg/day was positively correlated with a fourfold increase of medullary CSA (0.67 mm2/year P = 0.009), which resulted in a three- to fourfold loss of cortical density (−6.6 mg/mm3/year; P = 0.002) and cortical CSA (−0.57 mm2/year, P = 0.004). Patients with high disease activity and high GC dose at baseline demonstrated an increase in the total CSA (0.29 mm2/y; P = 0.049) and a loss of cortical BMD (−5.73 mg/mm3/y; P = 0.05) despite good clinical response. ConclusionIncrease in medullary metacarpal CSA and thinning of the cortical CSA are physiological and time dependent. RA status is associated with loss in cortical density. Even upon biological therapy, low glucocorticoid dose affects metacarpal bone shaft geometry and density over time.

The total number of white matter interstitial neurons in the human brain.

In the adult human brain, the interstitial neurons (WMIN) of the subcortical white matter are the surviving remnants of the fetal subplate zone. It has been suggested that they perform certain important functions and may be involved in the pathogenesis of several neurological and psychiatric disorders. However, many important features of this class of human cortical neurons remain insufficiently explored. In this study, we analyzed the total number, and regional and topological distribution of WMIN in the adult human subcortical white matter, using a combined immunocytochemical (NeuN) and stereological approaches. We found that the average number of WMIN in 1 mm3 of the subcortical white matter is 1.230±549, which translates to the average total number of 593811183.6±264849443.35 of WMIN in the entire subcortical telencephalic white matter. While there were no significant differences in their regional distribution, the lowest number of WMIN has been consistently observed in the limbic cortex, and the highest number in the frontal cortex. With respect to their topological distribution, the WMIN were consistently more numerous within gyral crowns, less numerous along gyral walls and least numerous at the bottom of cortical sulci (where they occupy a narrow and compact zone below the cortical-white matter border). The topological location of WMIN is also significantly correlated with their morphology: pyramidal and multipolar forms are the most numerous within gyral crowns, whereas bipolar forms predominate at the bottom of cortical sulci. Our results indicate that WMIN represent substantial neuronal population in the adult human cerebral cortex (e.g. more numerous than thalamic or basal ganglia neurons) and thus deserve more detailed morphological and functional investigations in the future.

Recent insights on the role and regulation of retinoic acid signaling during epicardial development.

The vitamin A metabolite, retinoic acid, carries out essential and conserved roles in vertebrate heart development. Retinoic acid signals via retinoic acid receptors (RAR)/retinoid X receptors (RXRs) heterodimers to induce the expression of genes that control cell fate specification, proliferation, and differentiation. Alterations in retinoic acid levels are often associated with congenital heart defects. Therefore, embryonic levels of retinoic acid need to be carefully regulated through the activity of enzymes, binding proteins and transporters involved in vitamin A metabolism. Here, we review evidence of the complex mechanisms that control the fetal uptake and synthesis of retinoic acid from vitamin A precursors. Next, we highlight recent evidence of the role of retinoic acid in orchestrating myocardial compact zone growth and coronary vascular development.

Differential roles of insulin like growth factor 1 receptor and insulin receptor during embryonic heart development

BackgroundThe embryonic day E10–13 period of mouse heart development is characterized by robust cardiomyocyte proliferation that creates the compact zone of thickened ventricular wall myocardium. This process is initiated by the formation of the epicardium on the outer heart surface, which releases insulin-like growth factor 2 (IGF2) as the primary cardiomyocyte mitogen. Two receptors mediate IGF2 signaling, the IGF1R and the insulin receptor (INSR).ResultsIn this study, we addressed the relative roles of the two IGF2 receptors in mouse heart development. We find that both receptors are expressed in the mouse heart during the E10–13 period, although IGF1R is much more prominently activated by IGF2 than INSR. Genetic manipulation indicates that only Igf1r is required for embryonic ventricular wall morphogenesis. INSR is not hyperactivated in the absence of IGF1R, and INSR does not compensate functionally for IGF1R in the absence of the latter.ConclusionsThese results define the molecular components that are responsible for a major burst of cardiomyocyte proliferation during heart development. These results may also be relevant to understanding the efficiency of regeneration of the mammalian heart after neonatal and adult injury.

First Observation of the Oscillation Effect in the Neutrino-4 Experiment on the Search for the Sterile Neutrino

We present the results of the Neutrino-4 experiment on search for a sterile neutrino. The experiment has been carried out on the SM-3 reactor having a compact active zone of $42\times42\times35\textrm{cm}^3$ and operating on the highly enriched uranium-235 at 90 MW thermal power. We report the results of the Neutrino-4 experiment of measurements of reactor antineutrino flux and spectrum dependence on the distance in the range 6-12 meters from the center of the reactor core. Using the measured spectrum and the distance dependence of antineutrino flux, we performed the model independent analysis of restrictions on the oscillation parameters $\Delta m^2_{14}$ and $\sin^2 2\theta_{14}$. The method of coherent addition of results of measurements is proposed. It allows us to directly observe the effect of oscillations. We observed the oscillation effect at CL $3.5\sigma$ in the vicinity of $\Delta m^2_{14} \approx 7.26\textrm{eV}^2$ and $\sin^2 2\theta_{14} \approx 0.38$. Combining the result of the Neutrino-4 experiment and the result of the gallium anomaly effect we obtained value $\sin^2 2\theta_{14} \approx 0.35 \pm 0.07 (5\sigma)$. The analysis of systematics effects is presented. Comparison with results of other experiments is presented. Future prospect of the experiment is discussed. It is necessary to notice that obtained values $\sin^2 2\theta_{14} \approx 0.35 \pm 0.07 (5\sigma)$ and $\Delta m^2_{14} \approx (7.3 \pm 0.7)\textrm{eV}^2$ allow make assessment on the mass of a neutrino: $m_{\beta} \approx 0.8\textrm{eV}$.

Nowe dane na temat obrządku pogrzebowego kultury amfor kulistych z zachodniej Lubelszczyzny

The discovery of the Naleczow type grave in Konskowola as well as the reinterpreta-tion of the grave from Pulawy-Wlostowice has shed new light on the funeral rite and range of influences of the Naleczow subgroup of the Globular Amphora culture in the western part of the Lublin region. Both sites are located outside the compact zone where features of this site occur and outside the upland area of the Naleczow Plateau. The graves from Pulawy-Wlostowiceand Konskowola differ slightly from the “classic” features of the Naleczow type in terms of their burial goods, and in Konskowola, the raw material used for the construction of the burial cham-ber. They most likely represent the youngest phase of settlement of the Naleczow subgroup in the Globular Amphorae culture. Translator: Andrzej Leligdowicz

Potential Common Pathogenic Pathways for the Left Ventricular Noncompaction Cardiomyopathy (LVNC).

Ventricular trabeculation and compaction are two essential morphogenetic events for generating a functionally competent ventricular wall. A significant reduction in trabeculation is usually associated with hypoplastic wall and ventricular compact zone deficiencies, which commonly leads to embryonic heart failure and early embryonic lethality. In contrast, the arrest of ventricular wall compaction (noncompaction) is believed to be causative to the left ventricular noncompaction (LVNC), a genetically heterogeneous disorder and the third most common cardiomyopathy among pediatric patients. After critically reviewing recent findings from genetically engineered mouse models, we suggest a model which proposes that defects in myofibrillogenesis and polarization in trabecular cardiomyocytes underly the common pathogenic mechanism for ventricular noncompaction.

Micro-anatomical structure of the first spine of the dorsal fin of Atlantic bluefin tuna, Thunnus thynnus (Osteichthyes: Scombridae)

The first spine of the first dorsal fin (FS) of the Atlantic bluefin tuna (ABFT), Thunnus thynnus, is customarily used in age determination research because its transverse sections display well-defined growth marks. In this paper the FS structure was studied to explain its known dramatic age- and season-related morphological modifications, which are evidently caused by bone remodeling. Cross sections of samples from six adult ABFT were in part decalcified to be stained with histological, histochemical and immunohistochemical methods, and in part embedded in methyl-methacrylate to be either observed under a linear polarized light or microradiographed. FS showed an external compact bone zone and an inner trabecular bone zone. The compact bone zone consisted of an outer non-osteonic primary bone layer (C1) and an inner osteonic bone layer (C2). C1 was in turn characterized by alternate translucent and opaque bands. Evidence of spine bone remodeling was shown by the presence of osteoclasts and osteoblasts as well as by tartrate-resistant acid phosphatase (TRAP) positive bands at the boundary between old and newly formed bone. The examination of plain, i.e. not-fixed and not-decalcified, FS from 28 ABFT showed that the average thickness of C1 remained fairly constant during fish growth, whereas C2 increased significantly, indicating that the periosteal primary bone apposition is counterbalanced by the parallel bone remodeling occurring inside the compact bone zone. The present study revealed the structure of the ABFT FS and the pattern of its bone remodeling. Both of them underlay phenomena, never examined in detail before, such as the appearance followed by the progressive disappearance of growth bands.

Role of Retinoic Acid Signaling in Epicardial‐Related Events During Late Heart Development

BackgroundDuring the final stages of heart development, the myocardium grows and becomes vascularized with the aid of paracrine factors and cell progenitors derived from the epicardium. Here, we study the involvement of retinoic acid (RA), a metabolite of vitamin A, in epicardial‐related developmental processes involving the formation of the coronary vasculature and the growth of the ventricular compact zone.MethodsTo explore the developmental consequences of altered RA signaling in late cardiogenic events, we employed a previously characterized model of embryonic RA excess based on mouse embryos deficient in the retinaldehyde reductase DHRS3. We also employed a complementary model based on embryonic RA deficiency generated by administering WIN 18,446, a bis(dichloroacetyl)diamine inhibitor of RA synthesis to pregnant dams. Using these two models we studied the formation of the coronary plexus and the formation and recruitment of epicardial‐derived mural cells by coronary vessels. We further explored the effect of altered RA in vitro by studying the epicardial epithelial‐to‐mesenchymal transition (EMT), and the formation, migration and differentiation of epicardial‐derived precursor cells (EPDCs).ResultsOur results demonstrated that both excess and deficiency of embryonic RA‐signaling led to a thin ventricular myocardium and aberrant coronary vessel formation and remodeling. In the case of both excess, or deficient RA‐signaling, the endothelial tubes did not become invested with epicardial‐derived vascular smooth muscle cells (VSMCs). In vitro assays of epicardial EMT combined with transcriptomic and proteomic analyses revealed that RA signaling not only affects the differentiation of EPDCs, but also controls the cytoskeletal reorganization and secretion of angiogenic and cardiotrophic factors by the epicardium.ConclusionWe report that RA signaling affects epicardial signaling and plays critical roles in the development of the myocardium and the coronary vasculature.Support or Funding InformationThis work was supported in part by the grant R01HD077260 (ARM, MAK) from the National Institutes of Health and by a Fulbright U.S. Scholar Award to ARM funded by the U.S. Department of State's Bureau of Educational and Cultural Affairs, the Commission for Educational Exchange between the United States of America and Brazil and CAPES, the Brazilian Federal Agency for Support and Evaluation of Graduate Education. Additional support to MAK was provided by the University of Maryland School of Pharmacy Mass Spectrometry Center (SOP1841‐IQB2014) and by startup funds to ARM from the Northern Ontario School of Medicine. Conflicts of interest: none.

Mechanisms of Trabecular Formation and Specification During Cardiogenesis

Trabecular morphogenesis is a key morphologic event during cardiogenesis and contributes to the formation of a competent ventricular wall. Lack of trabeculation results in embryonic lethality. The trabecular morphogenesis is a multistep process that includes, but isnot limited to, trabecular initiation, proliferation/growth, specification, and compaction. Although a number of signaling molecules have been implicated in regulating trabeculation, the cellular processes underlying mammalian trabecular formation are not fully understood. Recent works show that the myocardium displays polarity, and oriented cell division (OCD) and directional migration of the cardiomyocytes in the monolayer myocardium are required for trabecular initiation and formation. Furthermore, perpendicular OCD is an extrinsic asymmetric cell division that contributes to trabecular specification, and is a mechanism that causes the trabecular cardiomyocytes to be distinct from the cardiomyocytes in compact zone. Once the coronary vasculature system starts to function in the embryonic heart, the trabeculae will coalesce with the compact zone to thicken the heart wall, and abnormal compaction will lead to left ventricular non-compaction (LVNC) and heart failure. There are many reviews about compaction and LVNC. In this review, we will focus on the roles of myocardial polarity and OCD in trabecular initiation, formation, and specification.

Notch signaling regulates Hey2 expression in a spatiotemporal dependent manner during cardiac morphogenesis and trabecular specification

Hey2 gene mutations in both humans and mice have been associated with multiple cardiac defects. However, the currently reported localization of Hey2 in the ventricular compact zone cannot explain the wide variety of cardiac defects. Furthermore, it was reported that, in contrast to other organs, Notch doesn’t regulate Hey2 in the heart. To determine the expression pattern and the regulation of Hey2, we used novel methods including RNAscope and a Hey2CreERT2 knockin line to precisely determine the spatiotemporal expression pattern and level of Hey2 during cardiac development. We found that Hey2 is expressed in the endocardial cells of the atrioventricular canal and the outflow tract, as well as at the base of trabeculae, in addition to the reported expression in the ventricular compact myocardium. By disrupting several signaling pathways that regulate trabeculation and/or compaction, we found that, in contrast to previous reports, Notch signaling and Nrg1/ErbB2 regulate Hey2 expression level in myocardium and/or endocardium, but not its expression pattern: weak expression in trabecular myocardium and strong expression in compact myocardium. Instead, we found that FGF signaling regulates the expression pattern of Hey2 in the early myocardium, and regulates the expression level of Hey2 in a Notch1 dependent manner.

Effects of Quercetin on Neurodegenerative and Compensatory Processes in the Nigrostriatal System in a Model of the Preclinical Stage of Parkinson’s Disease in Rats

Data obtained over the last ten years on the involvement of molecular chaperones of the heat shock protein 70 (HSP70) family in the pathogenesis of Parkinson’s disease (PD) do not provide an answer to the question of whether a decrease in the expression of stress-inducible Hsp70 in the brain is one of the causes of progression of neurodegeneration in PD. The present study used the HSP expression inhibitor quercetin in a model of proteasomal dysfunction in the nigrostriatal system in rats created by microinjection of the proteasome inhibitor lactacystin into the compact zone of the substantia nigra (SNc). This model reproduces subthreshold levels of nigrostriatal system degradation and neurochemical changes present in the preclinical stage of PD. We provide the first demonstration that preventive administration of quercetin prevents LC-induced Hsp70 expression in SNc neurons and leads to a 1.5-fold increase in the degeneration of dopaminergic neurons in the SNc and a 2.7-fold increase in the number of dopaminergic neuron axons in the striatum, with depletion of compensation processes and HSP70 reserves in SNc neurons. Signs of motor dysfunction typical of the clinical stage of PD were seen. The study results confirm the important role of Hsp70 in the mechanisms of protection of the nigrostriatal system in proteasomal dysfunction typical of the preclinical stage of PD. These data may provide scientific grounds for developing new techniques for the early treatment of PD based on Hsp70 preparations.

Lime-based plasters with combined expanded clay-silica aggregate: Microstructure, texture and engineering properties

Plasters containing lightweight aggregates are mostly characteristic by low bulk density and low thermal conductivity but these favorable properties are often achieved at the expense of mechanical strength. In this paper, lightweight lime-based plasters are designed which have good thermal and mechanical properties at the same time. As their supposed applications include the renovation of surface layers of historical buildings, burnt clay shale is used as pozzolanic admixture to lime. The volumetric ratio of silica sand and expanded clay aggregate (ECA) is varied over a wide range to analyze the effect of ECA on microstructure, texture, and mechanical, thermal and hygric parameters of investigated plasters. The microstructural studies show a more compact interfacial transition zone between the basic lime-pozzolan matrix and ECA, as compared with silica sand, which is the most important factor affecting the properties of studied plasters. Apparently, the surface roughness of ECA grains at first makes possible easier formation of hydration products and later it can support the growth of calcite crystals and CSH amorphous phases. The textural analysis together with the measurement of basic physical properties reveals, as the second principal factor, a substantial increase of open porosity with the increasing ECA dosage; the added pores are mostly within the range of 10 nm to 1 μm. The assessment of the wide range of engineering properties of designed plasters leads to the identification of the lime-pozzolan plaster with the volumetric ratio of 1: 1 between silica sand and ECA as the most appropriate solution. The thermal conductivity of this plaster is two times lower than of the lime-pozzolan plaster with silica aggregates, while the changes in compressive and bending strengths are only marginal. The favorable hygric properties can be considered as another asset. Faster water vapor transport, together with the higher water vapor adsorption capability, can decrease a risk of water condensation and moderate the effects of both exterior and interior climate, the relatively slow liquid water transport is a limiting factor for rainwater penetration. The economical parameters of the plaster with the best functional properties are also very good. According to the current situation on the Czech market, the price increase is only 3%, as compared with the reference mix.

Abstract 231: A Hand1 Left Ventricular Enhancer that is Associated With Prolonged QRS Interval

Throughout the process of cardiogenesis, dynamic changes in cardiomyocyte morphology are defined by gene regulatory networks that drive atrial, ventricular, septal, compact zone or trabecular cardiomyocyte cellular identity. The bHLH transcription factors Hand1 and Hand2 are both critical for heart development. We have isolated a 750 bp evolutionarily conserved non-coding sequence 5’ to the Hand1 transcription start site that is necessary and sufficient to drive left ventricle (LV)-specific Hand1 expression. Regulatory cis -elements include Gata and T-box binding sights. We show this enhancer as necessary and sufficient for LV expression using CrispR/Cas9 deletion. Mice homozygous for this enhancer deletion ( Hand1 αLV/ αLV ) are viable and fertile. Adult Hand1 αLV/ αLV mice exhibit a prolonged QRS interval. Interestingly, human HAND1 SNPs associated with prolonged QRS are located near the LV enhancer, but these SNP sequences are not conserved in mice. More refined examination of the human sequences revealed additional prolonged QRS-associated human nucleotide changes occurring directly within the conserved enhancer that alter cis -element DNA binding. Ventricular conduction system gene expression is altered in Hand1 enhancer deletion mice, validating in vivo a human GWAS association study that links Hand1 function to the development and perhaps maintenance of the LV purkinje fiber network. Additionally, using the Hand1 LV-enhancer, we have generated a novel Cre transgenic mouse line ( Hand1 LV -Cre ), in which LV-specific recombination is observed. We use this Cre to delete both cardiomyocytes and Hand genes from the developing LV, discovering that specification of subpopulations of ventricular cardiomyocytes regulates myocardial growth and, thereby, cardiac function.