Myonuclear dynamics in muscle plasticity and the transcriptional regulation of resistance training induced hypertrophy.

Skeletal muscle is highly responsive to changes in mechanical load or activity and can adjust its morphological, metabolic, and contractile properties accordingly. The remodeling of these characteristics is controlled by the reprogramming of the transcriptional output of the myonuclei along the length of the muscle fiber. To meet the transcriptional demands of growth and increased activity, myonuclei can be added to the existing cytoplasm through the fusion of satellite cells, to support synthetic activity. This project utilises improved methodologies including automated, high-throughput immunohistochemical analysis and bulk RNA-sequencing of skeletal muscle. With these techniques, we define the temporal patterns of myonuclear dynamics and how they correspond to fiber-type specific adaptations in response to loading, unloading, reloading and changes in activity and how the acute transcriptional response is altered, dependent on the training status of the muscle. To induce these modalities of activity or inactivity, we utilised in-vivo models from our lab including, (1) programmed exercise delivered through miniature implanted pulse generators (IPGs) to induce muscle hypertrophy or metabolic adaptation and (2) disuse by means of tetrodotoxin-induced nerve silencing to induce muscle atrophy. We report that the genes that most closely track with changes in muscle mass are controlled centrally by the basic-helix-loop-helix transcription factor Myc, that functions to bind to E-box containing DNA sequences. In addition, we identify 10 other genes that appear as important regulators across species and modalities of exercise that warrant further investigation. Lastly, we investigate a promising marker for specifically identifying myonuclei, pericentriolar material-1 (PCM1), which would allow for deconvolution of mRNA signals from bulk skeletal muscle mRNA analysis, allowing for identification of myogenic and non-myogenic transcriptional changes. In summary, our aim is to provide key mechanistic insights into myonuclear dynamics and how adaptation of skeletal muscle is regulated at the transcriptional level

Novel applications of flow cytometry to assess whole murine skeletal muscle and myonuclei number responses to atrophy and recovery.

This thesis will present an introduction to cellular and molecular adaptation to loading and unloading of skeletal muscle, whilst exploring the advantages and disadvantages of current techniques employed in the field of exercise biochemistry. In response to the current techniques used to assess the signal transduction and protein changes present in response to loading and unloading, we propose a potential, novel method of assessing whole, murine skeletal muscle protein isoforms via flow cytometry. In addition to this, this thesis also explores the changes in morphology and myonuclear number within skeletal muscle following varying periods of atrophy, and recovery from atrophy produced in response to tetrodotoxin administration to silence a motor nerve and therefore muscular contraction in the ankle dorsiflexor muscles of the rat hindlimb

Adaptation of the transcriptional response to resistance exercise over 4 weeks of daily training

We present the time course of change in the muscle transcriptome 1 h after the last exercise bout of a daily resistance training program lasting 2, 10, 20, or 30 days. Daily exercise in rat tibialis anterior muscles (5 sets of 10 repetitions over 20 min) induced progressive muscle growth that approached a new stable state after 30 days. The acute transcriptional response changed along with progressive adaptation of the muscle phenotype. For example, expression of type 2B myosin was silenced. Time courses recently synthesized from human exercise studies do not demonstrate so clearly the interplay between the acute exercise response and the longer-term consequences of repeated exercise. We highlight classes of transcripts and transcription factors whose expression increases during the growth phase and declines again as the muscle adapts to a new daily pattern of activity and reduces its rate of growth. Myc appears to play a central role

Mechanical loading of bioengineered skeletal muscle in vitro recapitulates gene expression signatures of resistance exercise in vivo.

Understanding the role of mechanical loading and exercise in skeletal muscle (SkM) is paramount for delineating the molecular mechanisms that govern changes in muscle mass. However, it is unknown whether loading of bioengineered SkM in vitro adequately recapitulates the molecular responses observed after resistance exercise (RE) in vivo. To address this, the transcriptional and epigenetic (DNA methylation) responses were compared after mechanical loading in bioengineered SkM in vitro and after RE in vivo. Specifically, genes known to be upregulated/hypomethylated after RE in humans were analyzed. Ninety-three percent of these genes demonstrated similar changes in gene expression post-loading in the bioengineered muscle when compared to acute RE in humans. Furthermore, similar differences in gene expression were observed between loaded bioengineered SkM and after programmed RT in rat SkM tissue. Hypomethylation occurred for only one of the genes analysed (GRIK2) post-loading in bioengineered SkM. To further validate these findings, DNA methylation and mRNA expression of known hypomethylated and upregulated genes post-acute RE in humans were also analyzed at 0.5, 3, and 24 h post-loading in bioengineered muscle. The largest changes in gene expression occurred at 3 h, whereby 82% and 91% of genes responded similarly when compared to human and rodent SkM respectively. DNA methylation of only a small proportion of genes analyzed (TRAF1, MSN, and CTTN) significantly increased post-loading in bioengineered SkM alone. Overall, mechanical loading of bioengineered SkM in vitro recapitulates the gene expression profile of human and rodent SkM after RE in vivo. Although some genes demonstrated differential DNA methylation post-loading in bioengineered SkM, such changes across the majority of genes analyzed did not closely mimic the epigenetic response to acute-RE in humans

Lamin-Related Congenital Muscular Dystrophy Alters Mechanical Signaling and Skeletal Muscle Growth

Laminopathies are a clinically heterogeneous group of disorders caused by mutations in the LMNA gene, which encodes the nuclear envelope proteins lamins A and C. The most frequent diseases associated with LMNA mutations are characterized by skeletal and cardiac involvement, and include autosomal dominant Emery–Dreifuss muscular dystrophy (EDMD), limb-girdle muscular dystrophy type 1B, and LMNA-related congenital muscular dystrophy (LMNA-CMD). Although the exact pathophysiological mechanisms responsible for LMNA-CMD are not yet understood, severe contracture and muscle atrophy suggest that mutations may impair skeletal muscle growth. Using human muscle stem cells (MuSCs) carrying LMNA-CMD mutations, we observe impaired myogenic fusion with disorganized cadherin/β catenin adhesion complexes. We show that skeletal muscle from Lmna-CMD mice is unable to hypertrophy in response to functional overload, due to defective fusion of activated MuSCs, defective protein synthesis and defective remodeling of the neuromuscular junction. Moreover, stretched myotubes and overloaded muscle fibers with LMNA-CMD mutations display aberrant mechanical regulation of the yes-associated protein (YAP). We also observe defects in MuSC activation and YAP signaling in muscle biopsies from LMNA-CMD patients. These phenotypes are not recapitulated in closely related but less severe EDMD models. In conclusion, combining studies in vitro, in vivo, and patient samples, we find that LMNA-CMD mutations interfere with mechanosignaling pathways in skeletal muscle, implicating A-type lamins in the regulation of skeletal muscle growth

Perinatal mental ill health - the experiences of women from ethnic minority groups

This study aimed to investigate ethnic minority women’s experiences and opinions of perinatal mental health problems and the provision of perinatal mental health support services. An exploratory survey was undertaken using a questionnaire. Quantitative data were analysed using descriptive statistics and a simple thematic analysis was used for the qualitative data. A total of 51 responses from women of 14 different ethnic minority backgrounds were analysed. Women from minority ethnic groups face barriers to seeking help for perinatal mental ill health as a result of ongoing stigma and the poor attitudes and behaviours of health professionals and inappropriately designed services. Future interventions should focus on providing adequate cultural competency for health care professionals and ensure that all women are able to access culturally appropriate spaces to talk and be listened to within community settings and wider services

A neural oscillations perspective on phonological development and phonological processing in developmental dyslexia

Children’s ability to reflect upon and manipulate the sounds in words (’phonological awareness’) develops as part of natural language acquisition, supports reading acquisition, and develops further as reading and spelling are learned. Children with developmental dyslexia typically have impairments in phonological awareness. Many developmental factors contribute to individual differences in phonological development. One important source of individual differences may be the child’s sensory/neural processing of the speech signal from an amplitude modulation (~ energy or intensity variation) perspective, which may affect the quality of the sensory/neural representations (’phonological representations’) that support phonological awareness. During speech encoding, brain electrical rhythms (oscillations, rhythmic variations in neural excitability) re-calibrate their temporal activity to be in time with rhythmic energy variations in the speech signal. The accuracy of this neural alignment or ’entrainment’ process is related to speech intelligibility. Recent neural studies demonstrate atypical oscillatory function at slower rates in children with developmental dyslexia. Potential relations with the development of phonological awareness by children with dyslexia are discussed.Medical Research Council, G0400574 and G090237

Sensory theories of developmental dyslexia: three challenges for research.

Recent years have seen the publication of a range of new theories suggesting that the basis of dyslexia might be sensory dysfunction. In this Opinion article, the evidence for and against several prominent sensory theories of dyslexia is closely scrutinized. Contrary to the causal claims being made, my analysis suggests that many proposed sensory deficits might result from the effects of reduced reading experience on the dyslexic brain. I therefore suggest that longitudinal studies of sensory processing, beginning in infancy, are required to successfully identify the neural basis of developmental dyslexia. Such studies could have a powerful impact on remediation.This is the accepted manuscript. The final version is available from NPG at http://www.nature.com/nrn/journal/v16/n1/abs/nrn3836.html

The restorative role of annexin A1 at the blood–brain barrier

Annexin A1 is a potent anti-inflammatory molecule that has been extensively studied in the peripheral immune system, but has not as yet been exploited as a therapeutic target/agent. In the last decade, we have undertaken the study of this molecule in the central nervous system (CNS), focusing particularly on the primary interface between the peripheral body and CNS: the blood–brain barrier. In this review, we provide an overview of the role of this molecule in the brain, with a particular emphasis on its functions in the endothelium of the blood–brain barrier, and the protective actions the molecule may exert in neuroinflammatory, neurovascular and metabolic disease. We focus on the possible new therapeutic avenues opened up by an increased understanding of the role of annexin A1 in the CNS vasculature, and its potential for repairing blood–brain barrier damage in disease and aging

Post-mortem assessment in vascular dementia: advances and aspirations.

BACKGROUND: Cerebrovascular lesions are a frequent finding in the elderly population. However, the impact of these lesions on cognitive performance, the prevalence of vascular dementia, and the pathophysiology behind characteristic in vivo imaging findings are subject to controversy. Moreover, there are no standardised criteria for the neuropathological assessment of cerebrovascular disease or its related lesions in human post-mortem brains, and conventional histological techniques may indeed be insufficient to fully reflect the consequences of cerebrovascular disease. DISCUSSION: Here, we review and discuss both the neuropathological and in vivo imaging characteristics of cerebrovascular disease, prevalence rates of vascular dementia, and clinico-pathological correlations. We also discuss the frequent comorbidity of cerebrovascular pathology and Alzheimer's disease pathology, as well as the difficult and controversial issue of clinically differentiating between Alzheimer's disease, vascular dementia and mixed Alzheimer's disease/vascular dementia. Finally, we consider additional novel approaches to complement and enhance current post-mortem assessment of cerebral human tissue. CONCLUSION: Elucidation of the pathophysiology of cerebrovascular disease, clarification of characteristic findings of in vivo imaging and knowledge about the impact of combined pathologies are needed to improve the diagnostic accuracy of clinical diagnoses