Sex-Based Differences in Cardiac Gene Expression and Function in BDNF Val66Met Mice.

Brain-derived neurotrophic factor (BDNF) is a pleiotropic neuronal growth and survival factor that is indispensable in the brain, as well as in multiple other tissues and organs, including the cardiovascular system. In approximately 30% of the general population, BDNF harbors a nonsynonymous single nucleotide polymorphism that may be associated with cardiometabolic disorders, coronary artery disease, and Duchenne muscular dystrophy cardiomyopathy. We recently showed that transgenic mice with the human BDNF rs6265 polymorphism (Val66Met) exhibit altered cardiac function, and that cardiomyocytes isolated from these mice are also less contractile. To identify the underlying mechanisms involved, we compared cardiac function by echocardiography and performed deep sequencing of RNA extracted from whole hearts of all three genotypes (Val/Val, Val/Met, and Met/Met) of both male and female Val66Met mice. We found female-specific cardiac alterations in both heterozygous and homozygous carriers, including increased systolic (26.8%, p = 0.047) and diastolic diameters (14.9%, p = 0.022), increased systolic (57.9%, p = 0.039) and diastolic volumes (32.7%, p = 0.026), and increased stroke volume (25.9%, p = 0.033), with preserved ejection fraction and fractional shortening. Both males and females exhibited lower heart rates, but this change was more pronounced in female mice than in males. Consistent with phenotypic observations, the gene encoding SERCA2 (Atp2a2) was reduced in homozygous Met/Met mice but more profoundly in females compared to males. Enriched functions in females with the Met allele included cardiac hypertrophy in response to stress, with down-regulation of the gene encoding titin (Tcap) and upregulation of BNP (Nppb), in line with altered cardiac functional parameters. Homozygous male mice on the other hand exhibited an inflammatory profile characterized by interferon-γ (IFN-γ)-mediated Th1 immune responses. These results provide evidence for sex-based differences in how the BDNF polymorphism modifies cardiac physiology, including female-specific alterations of cardiac-specific transcripts and male-specific activation of inflammatory targets.

The BDNF rs6265 Polymorphism is a Modifier of Cardiomyocyte Contractility and Dilated Cardiomyopathy.

Brain-derived neurotrophic factor (BDNF) is a neuronal growth and survival factor that harbors cardioprotective qualities that may attenuate dilated cardiomyopathy. In ~30% of the population, BDNF has a common, nonsynonymous single nucleotide polymorphism rs6265 (Val66Met), which might be correlated with increased risk of cardiovascular events. We previously showed that BDNF correlates with better cardiac function in Duchenne muscular dystrophy (DMD) patients. However, the effect of the Val66Met polymorphism on cardiac function has not been determined. The goal of the current study was to determine the effects of rs6265 on BDNF biomarker suitability and DMD cardiac functions more generally. We assessed cardiovascular and skeletal muscle function in human DMD patients segregated by polymorphic allele. We also compared echocardiographic, electrophysiologic, and cardiomyocyte contractility in C57/BL-6 wild-type mice with rs6265 polymorphism and in mdx/mTR (mDMD) mouse model of DMD. In human DMD patients, plasma BDNF levels had a positive correlation with left ventricular function, opposite to that seen in rs6265 carriers. There was also a substantial decrease in skeletal muscle function in carriers compared to the Val homozygotes. Surprisingly, the opposite was true when cardiac function of DMD carriers and non-carriers were compared. On the other hand, Val66Met wild-type mice had only subtle functional differences at baseline but significantly decreased cardiomyocyte contractility. Our results indicate that the Val66Met polymorphism alters myocyte contractility, conferring worse skeletal muscle function but better cardiac function in DMD patients. Moreover, these results suggest a mechanism for the relative preservation of cardiac tissues compared to skeletal muscle in DMD patients and underscores the complexity of BDNF signaling in response to mechanical workload.

Neuregulin-1ß induces proliferation, survival and paracrine signaling in normal human cardiac ventricular fibroblasts.

Neuregulin-1ß (NRG-1ß) is critical for cardiac development and repair, and recombinant forms are currently being assessed as possible therapeutics for systolic heart failure. We previously demonstrated that recombinant NRG-1ß reduces cardiac fibrosis in an animal model of cardiac remodeling and heart failure, suggesting that there may be direct effects on cardiac fibroblasts. Here we show that NRG-1ß receptors (ErbB2, ErbB3, and ErbB4) are expressed in normal human cardiac ventricular (NHCV) fibroblast cell lines. Treatment of NHCV fibroblasts with recombinant NRG-1ß induced activation of the AKT pathway, which was phosphoinositide 3-kinase (PI3K)-dependent. Moreover, the NRG-1ß-induced PI3K/AKT signaling in these cells required phosphorylation of both ErbB2 and ErbB3 receptors at tyrosine (Tyr)1248 and Tyr1289 respectively. RNASeq analysis of NRG-1ß-treated cardiac fibroblasts obtained from three different individuals revealed a global gene expression signature consistent with cell growth and survival. We confirmed enhanced cellular proliferation and viability in NHCV fibroblasts in response to NRG-1ß, which was abrogated by PI3K, ErbB2, and ErbB3 inhibitors. NRG-1ß also induced production and secretion of cytokines (interleukin-1α and interferon-γ) and pro-reparative factors (angiopoietin-2, brain-derived neurotrophic factor, and crypto-1), suggesting a role in cardiac repair through the activation of paracrine signaling.

ERBB signaling attenuates proinflammatory activation of nonclassical monocytes.

Immune activation in chronic systolic heart failure (HF) correlates with disease severity and prognosis. Recombinant neuregulin-1 (rNRG-1) is being developed as a possible therapy for HF, based on the activation of ERBB receptors in cardiac cells. Work in animal models of HF led us to hypothesize that there may be direct effects of NRG-1 on immune system activation and inflammation. We investigated the expression of ERBB receptors and the effect of rNRG-1 isoform glial growth factor 2 (GGF2) in subpopulations of peripheral blood mononuclear cells (PB MNCs) in subjects with HF. We found that human monocytes express both ERBB2 and ERBB3 receptors, with high interindividual variability among subjects. Monocyte surface ERBB3 and TNF-α mRNA expression were inversely correlated in subjects with HF but not in human subjects without HF. GGF2 activation of ERBB signaling ex vivo inhibited LPS-induced TNF-α production, specifically in the CD14lowCD16+ population of monocytes in a phosphoinositide 3-kinase-dependent manner. GGF2 suppression of TNF-α correlated directly with the expression of ERBB3. In vivo, a single dose of intravenous GGF2 reduced TNF-α expression in PB MNCs of HF subjects participating in a phase I safety study of GGF2. These results support a role for ERBB3 signaling in the regulation of TNF-α production from CD14lowCD16+ monocytes and a need for further investigation into the clinical significance of NRG-1/ERBB signaling as a modulator of immune system function.NEW & NOTEWORTHY This study identified a novel role of neuregulin-1 (NRG-1)/ERBB signaling in the control of proinflammatory activation of monocytes. These results further improve our fundamental understanding of cardioprotective effects of NRG-1 in patients with heart failure.

Differential activation of natriuretic peptide receptors modulates cardiomyocyte proliferation during development.

Organ development is a highly regulated process involving the coordinated proliferation and differentiation of diverse cellular populations. The pathways regulating cell proliferation and their effects on organ growth are complex and for many organs incompletely understood. In all vertebrate species, the cardiac natriuretic peptides (ANP and BNP) are produced by cardiomyocytes in the developing heart. However, their role during cardiogenesis is not defined. Using the embryonic zebrafish and neonatal mammalian cardiomyocytes we explored the natriuretic peptide signaling network during myocardial development. We observed that the cardiac natriuretic peptides ANP and BNP and the guanylate cyclase-linked natriuretic peptide receptors Npr1 and Npr2 are functionally redundant during early cardiovascular development. In addition, we demonstrate that low levels of the natriuretic peptides preferentially activate Npr3, a receptor with Gi activator sequences, and increase cardiomyocyte proliferation through inhibition of adenylate cyclase. Conversely, high concentrations of natriuretic peptides reduce cardiomyocyte proliferation through activation of the particulate guanylate cyclase-linked natriuretic peptide receptors Npr1 and Npr2, and activation of protein kinase G. These data link the cardiac natriuretic peptides in a complex hierarchy modulating cardiomyocyte numbers during development through opposing effects on cardiomyocyte proliferation mediated through distinct cyclic nucleotide signaling pathways.

Effects of vitamin A deficiency in the postnatal mouse heart: role of hepatic retinoid stores.

To determine whether hepatic depletion of vitamin A (VA) stores has an effect on the postnatal heart, studies were carried out with mice lacking liver retinyl ester stores fed either a VA-sufficient (LRVAS) or VA-deficient (LRVAD) diet (to deplete circulating retinol and extrahepatic stores of retinyl esters). There were no observable differences in the weights or gross morphology of hearts from LRVAS or LRVAD mice relative to sex-matched, age-matched, and genetically matched wild-type (WT) controls fed the VAS diet (WTVAS), but changes in the transcription of functionally relevant genes were consistent with a state of VAD in LRVAS and LRVAD ventricles. In silico analysis revealed that 58/67 differentially expressed transcripts identified in a microarray screen are products of genes that have DNA retinoic acid response elements. Flow cytometric analysis revealed a significant and cell-specific increase in the number of proliferating Sca-1 cardiac progenitor cells in LRVAS animals relative to WTVAS controls. Before myocardial infarction, LRVAS and WTVAS mice had similar cardiac systolic function and structure, as measured by echocardiography, but, unexpectedly, repeat echocardiography demonstrated that LRVAS mice had less adverse remodeling by 1 wk after myocardial infarction. Overall, the results demonstrate that the adult heart is responsive to retinoids, and, most notably, reducing hepatic VA stores (while maintaining circulating levels of VA) impacts ventricular gene expression profiles, progenitor cell numbers, and response to injury.

Translating golden retriever muscular dystrophy microarray findings to novel biomarkers for cardiac/skeletal muscle function in Duchenne muscular dystrophy.

BACKGROUND: In Duchenne muscular dystrophy (DMD), abnormal cardiac function is typically preceded by a decade of skeletal muscle disease. Molecular reasons for differences in onset and progression of these muscle groups are unknown. Human biomarkers are lacking. METHODS: We analyzed cardiac and skeletal muscle microarrays from normal and golden retriever muscular dystrophy (GRMD) dogs (ages 6, 12, or 47+ mo) to gain insight into muscle dysfunction and to identify putative DMD biomarkers. These biomarkers were then measured using human DMD blood samples. RESULTS: We identified GRMD candidate genes that might contribute to the disparity between cardiac and skeletal muscle disease, focusing on brain-derived neurotropic factor (BDNF) and osteopontin (OPN/SPP1, hereafter indicated as SPP1). BDNF was elevated in cardiac muscle of younger GRMD but was unaltered in skeletal muscle, while SPP1 was increased only in GRMD skeletal muscle. In human DMD, circulating levels of BDNF were inversely correlated with ventricular function and fibrosis, while SPP1 levels correlated with skeletal muscle function. CONCLUSION: These results highlight gene expression patterns that could account for differences in cardiac and skeletal disease in GRMD. Most notably, animal model-derived data were translated to DMD and support use of BDNF and SPP1 as biomarkers for cardiac and skeletal muscle involvement, respectively.

Neuregulin-1ß induces embryonic stem cell cardiomyogenesis via ErbB3/ErbB2 receptors.

NRG-1ß (neuregulin-1ß) serves multiple functions during embryonic heart development by signalling through ErbB family receptor tyrosine kinases (ErbB2, ErbB3 and ErbB4). Previous studies reported that NRG-1ß induces cardiomyogenesis of mESCs (mouse embryonic stem cells) at the later stages of differen-tiation through ErbB4 receptor activation. In the present study we systematically examined NRG-1ß induction of cardiac myocytes in mESCs and identified a novel time window, the first 48 h, for NRG-1ß-based cardiomyogenesis. At this time point ErbB3, but not ErbB4, is expressed. In contrast with the later differentiation of mESCs in which NRG-1ß induces cardiomyogenesis via the ErbB4 receptor, we found that knocking down ErbB3 or ErbB2 with siRNA during the early differentiation inhibited NRG-1ß-induced cardiomyogenesis in mESCs. Microarray analysis of RNA expression at this early time point indicated that NRG-1ß treatment in mESCs resulted in gene expression changes important to differentiation including up-regulation of components of PI3K (phosphoinositide 3-kinase), a known mediator of the NRG-1ß/ErbB signalling pathway, as well as activation of CREB (cAMP-response-element-binding protein). Further study demonstrated that the NRG-1ß-induced phosphorylation of CREB was required for cardiomyogenesis of mESCs. In summary, we report a previously unrecognized role for NRG-1ß/ErbB3/CREB signalling at the pre-mesoderm stage for stem cell cardiac differentiation.

Embryonic domains of the aorta derived from diverse origins exhibit distinct properties that converge into a common phenotype in the adult.

Vascular smooth muscle cells (VSMCs) are derived from distinct embryonic origins. Vessels originating from differing smooth muscle cell populations have distinct vascular and pathological properties involving calcification, atherosclerosis, and structural defects such as aneurysm and coarctation. We hypothesized that domains within a single vessel, such as the aorta, vary in phenotype based on embryonic origin. Gene profiling and myographic analyses demonstrated that embryonic ascending and descending aortic domains exhibited distinct phenotypes. In vitro analyses demonstrated that VSMCs from each region were dissimilar in terms of cytoskeletal and migratory properties, and retention of different gene expression patterns. Using the same analysis, we found that these same two domains are indistinguishable in the adult vessel. Our data demonstrate that VSMCs from different embryonic origins are functionally distinct in the embryonic mouse, but converge to assume a common phenotype in the aorta of healthy adults. These findings have fundamental implications for aortic development, function and disease progression.

Transcriptional profiling reveals ductus arteriosus-specific genes that regulate vascular tone.

Failure of the ductus arteriosus (DA) to close at birth can lead to serious complications. Conversely, certain profound congenital cardiac malformations require the DA to be patent until corrective surgery can be performed. In each instance, clinicians have a very limited repertoire of therapeutic options at their disposal - indomethacin or ibuprofen to close a patent DA (PDA) and prostaglandin E1 to maintain patency of the DA. Neither treatment is specific to the DA and both may have deleterious off-target effects. Therefore, more therapeutic options specifically targeted to the DA should be considered. We hypothesized the DA possesses a unique genetic signature that would set it apart from other vessels. A microarray was used to compare the genetic profiles of the murine DA and ascending aorta (AO). Over 4,000 genes were differentially expressed between these vessels including a subset of ion channel-related genes. Specifically, the alpha and beta subunits of large-conductance calcium-activated potassium (BKCa) channels are enriched in the DA. Gain- and loss-of-function studies showed inhibition of BKCa channels caused the DA to constrict, while activation caused DA relaxation even in the presence of O2. This study identifies subsets of genes that are enriched in the DA that may be used to develop DA-specific drugs. Ion channels that regulate DA tone, including BKCa channels, are promising targets. Specifically, BKCa channel agonists like NS1619 maintain DA patency even in the presence of O2 and may be clinically useful.

Cross-species transcriptomic approach reveals genes in hamster implantation sites.

The mouse model has greatly contributed to understanding molecular mechanisms involved in the regulation of progesterone (P4) plus estrogen (E)-dependent blastocyst implantation process. However, little is known about contributory molecular mechanisms of the P4-only-dependent blastocyst implantation process that occurs in species such as hamsters, guineapigs, rabbits, pigs, rhesus monkeys, and perhaps humans. We used the hamster as a model of P4-only-dependent blastocyst implantation and carried out cross-species microarray (CSM) analyses to reveal differentially expressed genes at the blastocyst implantation site (BIS), in order to advance the understanding of molecular mechanisms of implantation. Upregulation of 112 genes and downregulation of 77 genes at the BIS were identified using a mouse microarray platform, while use of the human microarray revealed 62 up- and 38 down-regulated genes at the BIS. Excitingly, a sizable number of genes (30 up- and 11 down-regulated genes) were identified as a shared pool by both CSMs. Real-time RT-PCR and in situ hybridization validated the expression patterns of several up- and down-regulated genes identified by both CSMs at the hamster and mouse BIS to demonstrate the merit of CSM findings across species, in addition to revealing genes specific to hamsters. Functional annotation analysis found that genes involved in the spliceosome, proteasome, and ubiquination pathways are enriched at the hamster BIS, while genes associated with tight junction, SAPK/JNK signaling, and PPARα/RXRα signalings are repressed at the BIS. Overall, this study provides a pool of genes and evidence of their participation in up- and down-regulated cellular functions/pathways at the hamster BIS.

Neuregulin as a heart failure therapy and mediator of reverse remodeling.

The beta isoform of Neuregulin-1 (NRG-1ß), along with its receptors (ErbB2-4), is required for cardiac development. NRG-1ß, as well as the ErbB2 and ErbB4 receptors, is also essential for maintenance of adult heart function. These observations have led to its evaluation as a therapeutic for heart failure. Animal studies and ongoing clinical trials have demonstrated beneficial effects of two forms of recombinant NRG-1ß on cardiac function. In addition to the possible role for recombinant NRG-1ßs as heart failure therapies, endogenous NRG-1ß/ErbB signaling appears to play a role in restoring cardiac function after injury. The potential mechanisms by which NRG-1ß may act as both a therapy and a mediator of reverse remodeling remain incompletely understood. In addition to direct effects on cardiac myocytes NRG-1ß acts on the vasculature, interstitium, cardiac fibroblasts, and hematopoietic and immune cells, which, collectively, may contribute to NRG-1ß's role in maintaining cardiac structure and function, as well as mediating reverse remodeling.

Transcriptome analysis of cardiac endothelial cells after myocardial infarction reveals temporal changes and long-term deficits.

Endothelial cells (ECs) have essential roles in cardiac tissue repair after myocardial infarction (MI). To establish stage-specific and long-term effects of the ischemic injury on cardiac ECs, we analyzed their transcriptome at landmark time points after MI in mice. We found that early EC response at Day 2 post-MI centered on metabolic changes, acquisition of proinflammatory phenotypes, initiation of the S phase of cell cycle, and activation of stress-response pathways, followed by progression to mitosis (M/G2 phase) and acquisition of proangiogenic and mesenchymal properties during scar formation at Day 7. In contrast, genes involved in vascular physiology and maintenance of vascular tone were suppressed. Importantly, ECs did not return to pre-injury phenotypes after repair has been completed but maintained inflammatory, fibrotic and thrombotic characteristics and lost circadian rhythmicity. We discovered that the highest induced transcript is the mammalian-specific Sh2d5 gene that promoted migration and invasion of ECs through Rac1 GTPase. Our results revealed a synchronized, temporal activation of disease phenotypes, metabolic pathways, and proliferation in quiescent ECs after MI, indicating that precisely-timed interventions are necessary to optimize cardiac tissue repair and improve outcomes. Furthermore, long-term effects of acute ischemic injury on ECs may contribute to vascular dysfunction and development of heart failure.

Improved mitochondrial function in the hearts of sarcolipin-deficient dystrophin and utrophin double-knockout mice.

Duchenne muscular dystrophy (DMD) is a progressive muscle-wasting disease associated with cardiomyopathy. DMD cardiomyopathy is characterized by abnormal intracellular Ca2+ homeostasis and mitochondrial dysfunction. We used dystrophin and utrophin double-knockout (mdx:utrn-/-) mice in a sarcolipin (SLN) heterozygous-knockout (sln+/-) background to examine the effect of SLN reduction on mitochondrial function in the dystrophic myocardium. Germline reduction of SLN expression in mdx:utrn-/- mice improved cardiac sarco/endoplasmic reticulum (SR) Ca2+ cycling, reduced cardiac fibrosis, and improved cardiac function. At the cellular level, reducing SLN expression prevented mitochondrial Ca2+ overload, reduced mitochondrial membrane potential loss, and improved mitochondrial function. Transmission electron microscopy of myocardial tissues and proteomic analysis of mitochondria-associated membranes showed that reducing SLN expression improved mitochondrial structure and SR-mitochondria interactions in dystrophic cardiomyocytes. These findings indicate that SLN upregulation plays a substantial role in the pathogenesis of cardiomyopathy and that reducing SLN expression has clinical implications in the treatment of DMD cardiomyopathy.

Brain-derived neurotrophic factor rs6265 (Val66Met) single nucleotide polymorphism as a master modifier of human pathophysiology.

Brain-derived neurotrophic factor is the most prevalent member of the nerve growth factor family. Since its discovery in 1978, this enigmatic molecule has spawned more than 27,000 publications, most of which are focused on neurological disorders. Brain-derived neurotrophic factor is indispensable during embryogenesis and postnatally for the normal development and function of both the central and peripheral nervous systems. It is becoming increasingly clear, however, that brain-derived neurotrophic factor likewise plays crucial roles in a variety of other biological functions independently of sympathetic or parasympathetic involvement. Brain-derived neurotrophic factor is also increasingly recognized as a sophisticated environmental sensor and master coordinator of whole organismal physiology. To that point, we recently found that a common nonsynonymous (Val66→Met) single nucleotide polymorphism in the brain-derived neurotrophic factor gene (rs6265) not only substantially alters basal cardiac transcriptomics in mice but subtly influences heart gene expression and function differentially in males and females. In addition to a short description of recent results from associative neuropsychiatric studies, this review provides an eclectic assortment of research reports that support a modulatory role for rs6265 including and beyond the central nervous system.

Lipid-laden foam cells in the pathology of atherosclerosis: shedding light on new therapeutic targets.

INTRODUCTION: Lipid-laden foam cells within atherosclerotic plaques are key players in all phases of lesion development including its progression, necrotic core formation, fibrous cap thinning, and eventually plaque rupture. Manipulating foam cell biology is thus an attractive therapeutic strategy at early, middle, and even late stages of atherosclerosis. Traditional therapies have focused on prevention, especially lowering plasma lipid levels. Despite these interventions, atherosclerosis remains a major cause of cardiovascular disease, responsible for the largest numbers of death worldwide. AREAS COVERED: Foam cells within atherosclerotic plaques are comprised of macrophages, vascular smooth muscle cells, and other cell types which are exposed to high concentrations of lipoproteins accumulating within the subendothelial intimal layer. Macrophage-derived foam cells are particularly well studied and have provided important insights into lipid metabolism and atherogenesis. The contributions of foam cell-based processes are discussed with an emphasis on areas of therapeutic potential and directions for drug development. EXERT OPINION: As key players in atherosclerosis, foam cells are attractive targets for developing more specific, targeted therapies aimed at resolving atherosclerotic plaques. Recent advances in our understanding of lipid handling within these cells provide insights into how they might be manipulated and clinically translated to better treat atherosclerosis.

An isogenetic myoblast expression screen identifies DUX4-mediated FSHD-associated molecular pathologies.

Facioscapulohumeral muscular dystrophy (FSHD) is caused by an unusual deletion with neomorphic activity. This deletion derepresses genes in cis; however which candidate gene causes the FSHD phenotype, and through what mechanism, is unknown. We describe a novel genetic tool, inducible cassette exchange, enabling rapid generation of isogenetically modified cells with conditional and variable transgene expression. We compare the effects of expressing variable levels of each FSHD candidate gene on myoblasts. This screen identified only one gene with overt toxicity: DUX4 (double homeobox, chromosome 4), a protein with two homeodomains, each similar in sequence to Pax3 and Pax7. DUX4 expression recapitulates key features of the FSHD molecular phenotype, including repression of MyoD and its target genes, diminished myogenic differentiation, repression of glutathione redox pathway components, and sensitivity to oxidative stress. We further demonstrate competition between DUX4 and Pax3/Pax7: when either Pax3 or Pax7 is expressed at high levels, DUX4 is no longer toxic. We propose a hypothesis for FSHD in which DUX4 expression interferes with Pax7 in satellite cells, and inappropriately regulates Pax targets, including myogenic regulatory factors, during regeneration.

Sporadic breast cancer patients' germline DNA exhibit an AT-rich microsatellite signature.

Using a custom CGH-like oligonucleotide array to measure the global microsatellite content in the genomes of 72 cancer, cancer-free, and high risk patient and cell line samples (56 germline DNA and 16 in tumor or tumor cell line DNA) we found a unique, reproducible, and statistically significant pattern of 18 motif-specific microsatellite families (out of 962 possible 1-6 mer repeats) in breast cancer patient germline and tumor DNA, but not in germline DNA of cancer-free volunteer controls or in breast cancer patients with BRCA1/2 mutations. These high-similarity A/T rich repetitive motifs were also more pronounced in the germlines and tumors of colon cancer tumor patients (3/6 samples) and microsatellite unstable colon cancer cell lines; however, germline DNA of sporadic breast cancer patients exhibited the largest global content shift for those motifs with extreme AT/GC ratios. These results indicate that global microsatellite variability is complex, suggest the existence of a previously unknown genomic destabilization mechanism in breast cancer patients' germline DNA, and warrant further testing of such microsatellite variability as a predictor of future breast cancer development.

Neuregulin (NRG-1ß) Is Pro-Myogenic and Anti-Cachectic in Respiratory Muscles of Post-Myocardial Infarcted Swine.

Neuregulin-1ß (NRG-1ß) is a growth and differentiation factor with pleiotropic systemic effects. Because NRG-1ß has therapeutic potential for heart failure and has known growth effects in skeletal muscle, we hypothesized that it might affect heart failure-associated cachexia, a severe co-morbidity characterized by a loss of muscle mass. We therefore assessed NRG-1ß's effect on intercostal skeletal muscle gene expression in a swine model of heart failure using recombinant glial growth factor 2 (USAN-cimaglermin alfa), a version of NRG-1ß that has been tested in humans with systolic heart failure. Animals received one of two intravenous doses (0.67 or 2 mg/kg) of NRG-1ß bi-weekly for 4 weeks, beginning one week after infarct. Based on paired-end RNA sequencing, NRG-1ß treatment altered the intercostal muscle gene expression of 581 transcripts, including genes required for myofiber growth, maintenance and survival, such as MYH3, MYHC, MYL6B, KY and HES1. Importantly, NRG-1ß altered the directionality of at least 85 genes associated with cachexia, including myostatin, which negatively regulates myoblast differentiation by down-regulating MyoD expression. Consistent with this, MyoD was increased in NRG-1ß-treated animals. In vitro experiments with myoblast cell lines confirmed that NRG-1ß induces ERBB-dependent differentiation. These findings suggest a NRG-1ß-mediated anti-atrophic, anti-cachexia effect that may provide additional benefits to this potential therapy in heart failure.