Myogenin Research Articles

Genomic loci mispositioning in Tmem120a knockout mice yields latent lipodystrophy

Little is known about how the observed fat-specific pattern of 3D-spatial genome organisation is established. Here we report that adipocyte-specific knockout of the gene encoding nuclear envelope transmembrane protein Tmem120a disrupts fat genome organisation, thus causing a lipodystrophy syndrome. Tmem120a deficiency broadly suppresses lipid metabolism pathway gene expression and induces myogenic gene expression by repositioning genes, enhancers and miRNA-encoding loci between the nuclear periphery and interior. Tmem120a−/− mice, particularly females, exhibit a lipodystrophy syndrome similar to human familial partial lipodystrophy FPLD2, with profound insulin resistance and metabolic defects that manifest upon exposure to an obesogenic diet. Interestingly, similar genome organisation defects occurred in cells from FPLD2 patients that harbour nuclear envelope protein encoding LMNA mutations. Our data indicate TMEM120A genome organisation functions affect many adipose functions and its loss may yield adiposity spectrum disorders, including a miRNA-based mechanism that could explain muscle hypertrophy in human lipodystrophy.

Impact of Physical Activity and Exercise on the Epigenome in Skeletal Muscle and Effects on Systemic Metabolism

Exercise and physical activity induces physiological responses in organisms, and adaptations in skeletal muscle, which is beneficial for maintaining health and preventing and/or treating most chronic diseases. These adaptations are mainly instigated by transcriptional responses that ensue in reaction to each individual exercise, either resistance or endurance. Consequently, changes in key metabolic, regulatory, and myogenic genes in skeletal muscle occur as both an early and late response to exercise, and these epigenetic modifications, which are influenced by environmental and genetic factors, trigger those alterations in the transcriptional responses. DNA methylation and histone modifications are the most significant epigenetic changes described in gene transcription, linked to the skeletal muscle transcriptional response to exercise, and mediating the exercise adaptations. Nevertheless, other alterations in the epigenetics markers, such as epitranscriptomics, modifications mediated by miRNAs, and lactylation as a novel epigenetic modification, are emerging as key events for gene transcription. Here, we provide an overview and update of the impact of exercise on epigenetic modifications, including the well-described DNA methylations and histone modifications, and the emerging modifications in the skeletal muscle. In addition, we describe the effects of exercise on epigenetic markers in other metabolic tissues; also, we provide information about how systemic metabolism or its metabolites influence epigenetic modifications in the skeletal muscle.

Nonsurgical treatment reduces tendon inflammation and elevates tendon markers in early healing.

Operative treatment is assumed to provide superior outcomes to nonoperative (conservative) treatment following Achilles tendon rupture, however, this remains controversial. This study explores the effect of surgical repair on Achilles tendon healing. Rat Achilles tendons (n = 101) were bluntly transected and were randomized into groups receiving repair or non-repair treatments. By 1 week after injury, repaired tendons had inferior mechanical properties, which continued to 3- and 6-weekpost-injury, evidenced by decreased dynamic modulus and failure stress. Transcriptomics analysis revealed >7000 differentially expressed genes between repaired and non-repaired tendons after 1-week post-injury. While repaired tendons showed enriched inflammatory gene signatures, non-repaired tendons showed increased tenogenic, myogenic, and mechanosensitive gene signatures, with >200-fold enrichment in Tnmd expression. Analysis of gastrocnemius muscle revealed elevated MMP activity in tendons receiving repair treatment, despite no differences in muscle fiber morphology. Transcriptional regulation analysis highlighted that the highest expressed transcription factors in repaired tendons were associated with inflammation (Nfκb, SpI1, RelA, andStat1), whereas non-repaired tendons expressed markers associated with tissue development and mechano-activation (Smarca1, Bnc2, Znf521, Fbn1, andGli3). Taken together, these data highlight distinct differences in healing mechanism occurring immediately following injury and provide insights for new therapies to further augment tendons receiving repaired and non-repaired treatments.

CRISPR/Cas9 editing of directly reprogrammed myogenic progenitors restores dystrophin expression in a mouse model of muscular dystrophy.

SummaryGenetic mutations in dystrophin manifest in Duchenne muscular dystrophy (DMD), the most commonly inherited muscle disease. Here, we report on reprogramming of fibroblasts from two DMD mouse models into induced myogenic progenitor cells (iMPCs) by MyoD overexpression in concert with small molecule treatment. DMD iMPCs proliferate extensively, while expressing myogenic stem cell markers including Pax7 and Myf5. Additionally, DMD iMPCs readily give rise to multinucleated myofibers that express mature skeletal muscle markers; however, they lack DYSTROPHIN expression. Utilizing an exon skipping-based approach with CRISPR/Cas9, we report on genetic correction of the dystrophin mutation in DMD iMPCs and restoration of protein expression in vitro. Furthermore, engraftment of corrected DMD iMPCs into the muscles of dystrophic mice restored DYSTROPHIN expression and contributed to the muscle stem cell reservoir. Collectively, our findings report on a novel in vitro cellular model for DMD and utilize it in conjunction with gene editing to restore DYSTROPHIN expression in vivo.

Maternal undernutrition alters the skeletal muscle development and methylation of myogenic factors in goat offspring.

ObjectiveThe effects of maternal undernutrition during midgestation on muscle fiber histology, myosin heavy chain (MyHC) expression, methylation modification of myogenic factors, and the mammalian target of rapamycin (mTOR) signaling pathway in the skeletal muscles of prenatal and postnatal goats were examined.MethodsTwenty-four pregnant goats were assigned to a control (100% of the nutrients requirement, n = 12) or a restricted group (60% of the nutrients requirement, n = 12) between 45 and 100 days of gestation. Descendants were harvested at day 100 of gestation and at day 90 after birth to collect the femoris muscle tissue.ResultsMaternal undernutrition increased (p<0.05) the fiber area of the vastus muscle in the fetuses and enhanced (p<0.01) the proportions of MyHCI and MyHCIIA fibers in offspring, while the proportion of MyHCIIX fibers was decreased (p<0.01). DNA methylation at the +530 cytosine-guanine dinucleotide (CpG) site of the myogenic factor 5 (MYF5) promoter in restricted fetuses was increased (p<0.05), but the methylation of the MYF5 gene at the +274,280 CpG site and of the myogenic differentiation (MYOD) gene at the +252 CpG site in restricted kids was reduced (p<0.05). mTOR protein signals were downregulated (p<0.05) in the restricted offspring.ConclusionMaternal undernutrition altered the muscle fiber type in offspring, but its relationship with methylation in the promoter regions of myogenic genes needs to be elucidated.

A serum-free media formulation for cultured meat production supports bovine satellite cell differentiation in the absence of serum starvation

Cultured meat production requires the robust differentiation of satellite cells into mature muscle fibres without the use of animal-derived components. Current protocols induce myogenic differentiation in vitro through serum starvation, that is, an abrupt reduction in serum concentration. Here we used RNA sequencing to investigate the transcriptomic remodelling of bovine satellite cells during myogenic differentiation induced by serum starvation. We characterized canonical myogenic gene expression, and identified surface receptors upregulated during the early phase of differentiation, including IGF1R, TFRC and LPAR1. Supplementation of ligands to these receptors enabled the formulation of a chemically defined media that induced differentiation in the absence of serum starvation and/or transgene expression. Serum-free myogenic differentiation was of similar extent to that induced by serum starvation, as evaluated by transcriptome analysis, protein expression and the presence of a functional contractile apparatus. Moreover, the serum-free differentiation media supported the fabrication of three-dimensional bioartificial muscle constructs, demonstrating its suitability for cultured beef production.

Laser Environmental Enrichment and Spirulina Algae Improve Broiler Growth Performance and Alter Myogenic Gene Expression and pectoralis major Dimensions

Sustainability in poultry production is evident in efforts to reduce inputs and a focus on bird welfare and livability. Dietary protein alternatives to traditional sources such as soybean meal aim to meet or exceed efficiency benchmarks and be cost-effective. Environmental enrichment encouraging activity may reduce the occurrence of the predominant breast muscle myopathy, woody breast (WB); interventions to minimize muscle damage and economic loss have yet to be established. The study objectives were to maintain or improve broiler performance and breast quality through environmental enrichment and partially replacing dietary soybean meal with Spirulina. Twelve hundred Ross 708 broilers were randomly assigned to enrichment (LASER; laser enrichment, or CON; no laser enrichment) and diet (algae; 2.5% Spirulina algae, or control) in a 2 × 2 factorial design for 49 days. The same 70 randomly selected birds were examined for contact dermatitis wk 1–6. Breast width was measured weekly on 200 growing broilers beginning on d22. On d42 and 49 slaughter, WB score was assigned using a tactile 0–3 scale and the right breast filet was weighed (n = 200). RNA isolated from 30 breast muscle samples each at d42 and 49 was analyzed using real-time qPCR. Laser enrichment increased body weight at all timepoints (d49: 0.148 kg, P &amp;lt; 0.001). Feed conversion ratio was improved in LASER-enriched birds by 3 points in the starter period (P = 0.003). Breast width was increased at all timepoints in LASER-enriched birds compared to CON (d49: 0.47 cm, P &amp;lt; 0.001). Algae inclusion increased body weight at d28 (0.059 kg, P = 0.005). At d42, 12% more LASER-enriched WB scores were 0 (normal) compared to CON, and at d49, 15% more enriched scores were 0. At d42, 5% more algae-fed broiler scores were 0 compared to control. LASER-enriched broiler breast tissue showed upregulated expression of myogenin, muscle regulatory factor 4, insulin-like growth factor 1, and myostatin compared to CON (P &amp;lt; 0.01). Both laser enrichment and algae inclusion improved broiler performance without negatively impacting environmental or physiological outcomes. LASER enrichment decreased severity of WB score and positively shifted myogenic gene expression in the breast muscle at slaughter.

L-Arginine Supplementation for Nulliparous Sows during the Last Third of Gestation.

Simple SummaryNutrition of gestating sows plays an important role in the uteroplacental efficiency, muscle development, birth weight and viability of the piglets. This is especially important for nulliparous sows, since the reproductive performance of nulliparous sows is lower compared to multiparous ones. Previous studies have shown that arginine enhances angiogenesis and placental growth, being beneficial to fetus growth. Because during its formation process skeletal muscle tissue compete for nutrients with other organs also in formation during the intrauterine development, the increase of nutrient flow by enhancing angiogenesis may benefit the skeletal muscle formation during the fetal stage. In this sense, arginine supplementation for sows seems to be a promising nutritional strategy to maximize myogenesis and muscle development of piglets. In the present study, piglets born from sows fed diet with 1.0% L-arginine (ARG) had greater mRNA expression of the gene encoding myoblast determination protein (MYOD) and myogenin (MYOG) compared to the piglets born from sows at the control group. The mRNA expression of IGF-2 gene tended to be greater in piglets born from ARG sows compared to those born from control sows. Despite differences in gene expression, no differences in the histomorphometric variables of skeletal muscle were observed between piglets from arginine-supplemented and control sows. In conclusion, supplementation of 1.0% L-arginine for nulliparous sows from 85 to 114 days of gestation increased mRNA expression of the myogenic regulatory factors MYOD and MYOG and IGF-2 in skeletal muscle of piglets.We evaluated the effects of L-arginine supplementation during the last third of gestation on molecular mechanisms related to skeletal muscle development of piglets and litter traits at birth. Twenty-three nulliparous sows averaging 205.37 ± 11.50 kg of body weight were randomly assigned to the following experimental treatments: control (CON), where pregnant sows were fed diets to meet their nutritional requirements; arginine (ARG), where sows where fed CON + 1.0% L-arginine. Skeletal muscle from piglets born from sows from ARG group had greater mRNA expression of MYOD (p = 0.043) and MYOG (p ≤ 0.01), and tended to present greater mRNA expression (p = 0.06) of IGF-2 gene compared to those born from CON sows. However, there were no differences (p > 0.05) in the histomorphometric variables of fetuses’ skeletal muscle. The total weight of born piglets, total weight of born alive piglets, piglet weight at birth, coefficient of variation of birth weight, and the incidence of intrauterine growth restriction (IUGR) piglets did not differ between groups. No stillborn piglets (p < 0.01) were verified in the ARG sows compared to CON group. The blood levels of estradiol (p = 0.035) and urea (p = 0.03) were higher in ARG sows compared to those from the CON group. In summary, our data show that arginine supplementation of nulliparous sows at late gestation enhance mRNA expression of key myogenic regulatory factors, which likely contribute to improve animal growth rates in later stages of development.

Effect of Actin Alpha Cardiac Muscle 1 on the Proliferation and Differentiation of Bovine Myoblasts and Preadipocytes.

Simple SummaryMarbling is an important factor affecting the quality of beef. The co-culture (myoblast-preadipocytes) system was successfully established in our lab in the early stage to simulate the internal environment of marbling. Within this environment, ACTC1 gene was a differentially expressed gene screened from the co-culture system. The gene was not expressed in monocultured adipocytes but was expressed in co-cultured adipocytes. Therefore, we hypothesize that the ACTC1 gene plays a role in the development of bovine myoblasts and preadipocytes. In this study, we explored the effect of ACTC1 gene on the proliferation and differentiation of bovine myoblasts and preadipocytes, aiming to discover the potential biological function of ACTC1 gene in muscle development and fat deposition. The results showed that ACTC1 could regulate the development of bovine myoblasts and preadipocytes, and ACTC1 could be used as an important target for improving beef quality in the future.Actin Alpha Cardiac Muscle 1 (ACTC1) gene is a differentially expressed gene screened through the co-culture system of myoblasts-preadipocytes. In order to study the role of this gene in the process of proliferation and differentiation of bovine myoblasts and preadipocytes, the methods of the knockdown, overexpression, and ectopic expression of ACTC1 were used in this study. After ACTC1 knockdown in bovine myoblasts and inducing differentiation, the sizes and numbers of myotube formation were significantly reduced compared to the control group, and myogenic marker genes—MYOD1, MYOG, MYH3, MRF4, MYF5, CKM and MEF2A—were significantly decreased (p < 0.05, p < 0.01) at both the mRNA and protein levels of myoblasts at different differentiation stages (D0, D2, D4, D6 and D8). Conversely, ACTC1 overexpression induced the inverse result. After ectopic expression of ACTC1 in bovine preadipocytes and induced differentiation, the number and size of lipid droplets were significantly higher than those of the control group, and the expression of adipogenic marker genes—FABP4, SCD1, PPARγ and FASN—were significantly increased (p < 0.05, p < 0.01) at the mRNA and protein levels of preadipocytes at different differentiation stages. Flow cytometry results showed that both the knockdown and overexpression of ACTC1 inhibited the normal cell cycle of myoblasts; however, ectopic expression of ACTC1 in adipocytes induced no significant cell cycle changes. This study is the first to explore the role of ACTC1 in bovine myogenesis and lipogenesis and demonstrates that ACTC1 promotes the differentiation of bovine myoblasts and preadipocytes, affecting the proliferation of myoblasts.

Decellularized Extracellular Matrix for Cell Biology.

The extracellular matrix (ECM) is an architecture that supports the cells in our bodies and regulates various cell functions. The ECM is composed of many proteins and carbohydrates, and these molecules activate various intracellular signaling pathways orchestrated to decide cell fates. Therefore, it is not enough to study the role of single ECM molecules to understand the roles of the ECM in the regulation of cell functions; it is necessary to understand how the ECM, as an assembly of various molecules, regulates cell functions as a whole. For this purpose, in vitro ECM models mimicking native ECM are required. Here, a decellularization technique is presented to reconstitute native ECM in vitro. In this article, methods for preparing decellularized ECM (dECM) are described for use in tumor and stem cell biology. Additionally, a method for confirmation of decellularization and a dECM modification method are described. These dECM types will be useful for comprehensive studies of ECM roles. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Preparation of in vitro extracellular matrix (ECM) models mimicking native ECM in different malignant tumor tissues Basic Protocol 2: Preparation of in vitro ECM models mimicking native ECM surrounding myoblasts differentiating into myotubes at each myogenic stage Support Protocol 1: Confirmation of myogenic stages by myogenic stages by myogenic gene expression analysis Basic Protocol 3: Confirmation of cell removal Basic Protocol 4: Reduction of chondroitin sulfate chains in cultured cell-derived decellularized ECM Support Protocol 2: Quantification of chondroitin sulfate chain amounts in the decellularized ECM.

Controllable assembly of skeletal muscle-like bundles through 3D bioprinting

3D printing is an effective technology for recreating skeletal muscle tissue in vitro. To achieve clinical skeletal muscle injury repair, relatively large volumes of highly aligned skeletal muscle cells are required; obtaining these is still a challenge. It is currently unclear how individual skeletal muscle cells and their neighbouring components co-ordinate to establish anisotropic architectures in highly homogeneous orientations. Here, we demonstrated a 3D printing strategy followed by sequential culture processes to engineer skeletal muscle tissue. The effects of confined printing on the skeletal muscle during maturation, which impacted the myotube alignment, myogenic gene expression, and mechanical forces, were observed. Our findings demonstrate the dynamic changes of skeletal muscle tissue during in vitro 3D construction and reveal the role of physical factors in the orientation and maturity of muscle fibres.

BAF complexes drive proliferation and block myogenic differentiation in fusion-positive rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a pediatric malignancy of skeletal muscle lineage. The aggressive alveolar subtype is characterized by t(2;13) or t(1;13) translocations encoding for PAX3- or PAX7-FOXO1 chimeric transcription factors, respectively, and are referred to as fusion positive RMS (FP-RMS). The fusion gene alters the myogenic program and maintains the proliferative state while blocking terminal differentiation. Here, we investigated the contributions of chromatin regulatory complexes to FP-RMS tumor maintenance. We define the mSWI/SNF functional repertoire in FP-RMS. We find that SMARCA4 (encoding BRG1) is overexpressed in this malignancy compared to skeletal muscle and is essential for cell proliferation. Proteomic studies suggest proximity between PAX3-FOXO1 and BAF complexes, which is further supported by genome-wide binding profiles revealing enhancer colocalization of BAF with core regulatory transcription factors. Further, mSWI/SNF complexes localize to sites of de novo histone acetylation. Phenotypically, interference with mSWI/SNF complex function induces transcriptional activation of the skeletal muscle differentiation program associated with MYCN enhancer invasion at myogenic target genes, which is recapitulated by BRG1 targeting compounds. We conclude that inhibition of BRG1 overcomes the differentiation blockade of FP-RMS cells and may provide a therapeutic strategy for this lethal childhood tumor.

Epigenetic Regulation of Myogenesis: Focus on the Histone Variants

Skeletal muscle development and regeneration rely on the successive activation of specific transcription factors that engage cellular fate, promote commitment, and drive differentiation. Emerging evidence demonstrates that epigenetic regulation of gene expression is crucial for the maintenance of the cell differentiation status upon division and, therefore, to preserve a specific cellular identity. This depends in part on the regulation of chromatin structure and its level of condensation. Chromatin architecture undergoes remodeling through changes in nucleosome composition, such as alterations in histone post-translational modifications or exchange in the type of histone variants. The mechanisms that link histone post-translational modifications and transcriptional regulation have been extensively evaluated in the context of cell fate and differentiation, whereas histone variants have attracted less attention in the field. In this review, we discuss the studies that have provided insights into the role of histone variants in the regulation of myogenic gene expression, myoblast differentiation, and maintenance of muscle cell identity.

Engineered Myoblast-Laden Collagen Filaments Fabricated Using a Submerged Bioprinting Process to Obtain Efficient Myogenic Activities.

The skeletal muscle tissue comprises a hierarchical fibrous structure with fully aligned myofibers. To obtain a unique aligned engineering construct for regenerating muscle tissue, we adopted a submerged bioprinting process. Here, 3 wt % collagen and 6 wt % alginate solutions were used as a matrix cell-encapsulating bioink and supporting solution in the printing bath, respectively. By manipulating the processing parameters (various alginate weight fractions in the bath, nozzle moving speed, and hydrostatic pressure), cell-laden filaments (∼50 μm in diameter) were successfully fabricated. They presented a high degree of alignment of the fibrillated collagen and meaningful initial viability (∼90%) of the C2C12 myoblasts. In vitro cellular responses indicated that fully aligned F-actin filaments of myoblasts were developed, resulting in a high degree of alignment/formation of myotubes, compared to that in the controls (>100 μm diameter of cell-laden filaments). Furthermore, the expression levels of various myogenic genes (Myod1, Myh2, and Myog) were measured using a reverse transcription polymerase chain reaction on day 21 of the cell culture, and the results showed that the cell-laden filaments with a small diameter had considerably greater gene expression levels (2.2-8-fold) than those with a relatively large diameter. Thus, the printing process described herein can provide a new potential biofabricating platform to obtain cell-laden engineering constructs for various tissues.

Ago1 controls myogenic differentiation by regulating eRNA-mediated CBP-guided epigenome reprogramming.

The role of chromatin-associated RNAi components in the nucleus of mammalian cells and in particular in the context of developmental programs remains to be elucidated. Here, we investigate the function of nuclear Argonaute 1 (Ago1) in gene expression regulation during skeletal muscle differentiation. We show that Ago1 is required for activation of the myogenic program by supporting chromatin modification mediated by developmental enhancer activation. Mechanistically, we demonstrate that Ago1 directly controls global H3K27 acetylation (H3K27ac) by regulating enhancer RNA (eRNA)-CREB-binding protein (CBP) acetyltransferase interaction, a key step in enhancer-driven gene activation. In particular, we show that Ago1 is specifically required for myogenic differentiation 1 (MyoD) and downstream myogenic gene activation, whereas its depletion leads to failure of CBP acetyltransferase activation and blocking of the myogenic program. Our work establishes a role of the mammalian enhancer-associated RNAi component Ago1 in epigenome regulation and activation of developmental programs.

Dietary 25(OH)D3 supplementation to gestating and lactating sows and their progeny affects growth performance, carcass characteristics, blood profiles and myogenic regulatory factor-related gene expression in wean-finish pigs.

ObjectiveThis experiment investigated the effects of supplementing vitamin D3-fortified sow and progeny diets with 25(OH)D3 on growth performance, carcass characteristics, immunity, and pork meat quality.MethodsThe present study involved the assessment of supplementing the diet of sows and their progeny with or without 25 (OH)D3 in a 2×2 factorial arrangement on the performance and production characteristics of wean-finish pigs. Forty-eight multiparous sows were assigned to a basal diet containing 2000 IU/kg vitamin D3 and supplemented without (CON) or with (TRT) 50 μg/kg 25 (OH)D3. At weaning, a total of 80 pigs each from CON and TRT sows were allocated to weaning and growing-finishing basal diets fortified with 2,500 and 1,750 IU/kg vitamin D3 respectively and supplemented without or with 50 μg/kg 25(OH)D3.ResultsSows fed 25(OH)D3-supplemented diets improved pre-weaning growth rate of nursing piglets. A significant sow and pig weaning diet effect was observed for growth rate and feed efficiency (p<0.05) during days 1 to 42 post-weaning. Pigs consuming 25(OH)D3-supplemented diets gained weight faster (p = 0.016), ate more (p = 0.044) and tended to convert feed to gain more efficiently (p = 0.088) than those fed CON diet between days 98 and 140 post-weaning. Supplemental 25(OH)D3 improved water holding capacity and reduced drip loss of pork meat, increased serum 25(OH)D3 level, produced higher interleukin-1 and lower interleukin-6 concentrations in blood circulation, downregulated myostatin (MSTN) and upregulated myogenic differentiation (MYOD) and myogenic factor 5 (MYF5) gene expressions (p<0.05).ConclusionSupplementing vitamin D3-fortified sow and wean-finish pig diets with 50 μg/kg 25(OH)D3 significantly improved production performance suggesting their current dietary vitamin D3 levels are insufficient. In fulfilling the total need for vitamin D, it is strongly recommended to add 50 μg/kg 25(OH)D3 “on top” to practical vitamin D3-fortified sow and wean-finish pig diets deployed under commercial conditions.

Mutual stimulatory signaling between human myogenic cells and rat cerebellar neurons.

Insight into the bidirectional signaling between primary human myogenic cells and neurons is lacking. For this purpose, human myogenic cells were derived from the semitendinosus and gracilis muscles of five healthy individuals and co‐cultured with cerebellar granule neurons from two litters of 7‐day‐old Wistar rat pups, in muscle medium or neural medium, alongside monocultures of myogenic cells or neurons. RT‐PCR was performed to determine human mRNA levels of GAPDH, Ki67, myogenin, and MUSK, and the acetylcholine receptor subtypes CHRNA1, CHRNB1, CHRNG, CHRND, and CHRNE, and rat mRNA levels of GAPDH, Fth1, Rack1, vimentin, Cdh13, and Ppp1r1a. Immunocytochemistry was used to evaluate neurite outgrowth (GAP43) in the presence and absence of myogenic cells. Co‐culture with primary neurons lead to higher myogenic cell gene expression levels of GAPDH, myogenin, MUSK, CHRNA1, CHRNG, and CHRND, compared to myogenic cells cultured alone. It appeared that neurons preferentially attached to myotubes and that neurite outgrowth was enhanced when neurons were cultured with myogenic cells compared to monoculture. In neural medium, rat mRNA levels of GAPDH, vimentin, Cdh13, and Ppp1r1a were greater in co‐culture, versus monoculture, whereas in muscle medium co‐culture lead to lower levels of Fth1, Rack1, vimentin, and Cdh13 than monoculture. These findings demonstrate mutually beneficial stimulatory signaling between rat cerebellar granule neurons and human myogenic cells, providing support for an active role for both the neuron and the muscle cell in stimulating neurite growth and myogenesis. Bidirectional muscle nerve signaling.

97 Awardee Talk: Feeding Essential Fatty Acids to Late-gestating Beef Cows Optimizes Performance and Health Responses of the Offspring

Abstract Option 1, Fetal Programming Only: Non-lactating, pregnant, multiparous Angus × Hereford cows (n = 104) were ranked by pregnancy sire (1 of 2 sires), body weight (BW), and body condition score (BCS) on d -15 of the experiment (d 180 of gestation). Cows were then assigned to receive: (1) 195 g/cow daily of CSSO (n = 52) or 2) 170 g/cow daily of CON (n = 52). Cows received treatments individually from d 0 to calving. Calves were weaned on d 290 of the experiment, preconditioned for 35 d, and placed in a feedyard until slaughter (d 514). Cows receiving CSSO and their calves had greater (P &amp;lt; 0.01) plasma concentrations ω-6 PUFA compared with CON after calving. Colostrum IgG and calf plasma IgG concentrations 24 h after birth were greater (P ≤ 0.02) in CSSO vs. CON cattle. Calves from CSSO cows had greater (P ≤ 0.05) expression of adipogenic and myogenic genes in the longissimus muscle compared with CON. No treatments differences in birth BW, weaning BW, and final preconditioning BW were noted (P ≥ 0.36). Average daily gain and final BW in the feedyard were greater (P ≤ 0.05) in steers from CSSO cows compared with CON. The incidence of calves diagnosed with BRD that required a second antimicrobial treatment was less (P = 0.03) in calves from CSSO cows, resulting in reduced (P = 0.05) need of treatments to regain health compared with CON. Upon slaughter, LM area was greater (P = 0.03) in calves from CSSO cows compared with CON. Collectively, these results are indicative of programming effects on postnatal offspring growth and health resultant from CSSO supplementation to late-gestating cows. Hence, supplementing CSSO to beef cows during pregnancy might be a feasible alternative to optimize offspring productivity and welfare. Option 2, Fetal Programming and Fat Tubs: Two experiments were conducted to evaluate: (1) effects of calcium salts of soybean oil (CSSO) supplementation to late gestating beef cows on the performance of the offspring; (2) the viability of utilizing low-moisture molasses-based blocks (LMB) as a delivery method for CSSO supplementation. In experiment 1, non-lactating, pregnant, multiparous Angus × Hereford cows were assigned to receive: (1) 195 g/cow daily of CSSO (n = 52) or (2) 170 g/cow daily of CON (n = 52) from d 195 of gestation until calving. CSSO cattle had greater (P &amp;lt; 0.01) plasma concentrations ω-6 PUFA; greater (P ≤ 0.02) colostrum and calf plasma IgG concentrations; greater (P ≤ 0.05) expression of adipogenic and myogenic genes in the longissimus muscle (LM); required fewer microbial treatments for BRD (P = 0.05) and had greater LM area compared to CON cohorts. In experiment 2, non-lactating, non-pregnant, multiparous beef cows were allocated to 1 of 9 pens (n = 9 pens; 4 cows/pen) and each pen was assigned to receive: 1) NOSUPP, hay only diet; 2) LMB, self-fed LMB supplement containing 24.7% DM CSSO; 3) CONC, hand-fed supplement identical to LMB. The design was a replicated 3 x 2 Latin square with 2 periods of 42 d, and a 21-d washout interval. Supplement DM intake did not differ (P = 0.39) between LMB and CONC cows from d 14 to 42 as designed, despite a greater variation in daily intake of LMB vs. CONC (treatment × day interaction; P &amp;lt; 0.01). No treatments effects were noted (P ≥ 0.40) for hay intake, BCS, and BW. From d 14 to 42, plasma concentrations of, ω-6 PUFA (P &amp;lt; 0.01) in CONC and LMB vs. NOSUPP cows. Hence, the use of self-fed LMB appears to be a valid strategy to provide CSSO to forage-fed beef cattle.

PSIII-23 Maternal metabolizable protein level and rumen-protected methionine impacts on beef steer progeny gene expression in muscle and liver

Abstract This experiment evaluated how maternal metabolizable protein level and rumen-protected methionine supplementation during late gestation impacts expression of genes associated with fetal programming in beef steer offspring. In a 3 x 2 factorial arrangement, 138 Angus crossbred cows were randomly assigned one of three metabolizable protein (MP) treatments (fed to meet 90, 100, or 110% of MP requirements), with(without) 9 g/d of rumen-protected methionine (MET; Smartamine®M, Adisseo Inc.). The isocaloric diets were fed for the last 8 weeks of gestation. Steer progeny (n = 51) were assigned to one of seven pens by weight and received a common corn-based grower diet (58% corn silage, 26% alfalfa haylage, 15% soybean meal) for 47 days, followed by a finisher diet (78% high moisture corn, 12% alfalfa haylage, 8% soybean meal) for 115 ±31.5 days until slaughter. At slaughter, samples of Sternomandibularis muscle and liver were collected and snap-frozen in liquid nitrogen for RNA isolation and analysis of gene expression for growth, myogenic, and adipogenic genes. Data were analyzed using PROC GLIMMIX in SAS, with maternal MP level and MET supplementation as fixed effects, and pen as a random effect. Exceeding maternal MP requirements increased expression of myogenic regulatory factor, myogenin (MYOG; 90% MP: 0.72, 100% MP: 0.94, and 110% MP: 1.00; SEM = 0.083, respectively; P = 0.02) in muscle from steer progeny at slaughter. Methionine supplementation decreased expression of pyruvate kinase (PKM; MET: 0.81, No MET: 1.16; SEM = 0.092; P = 0.02) in muscle, which is associated with lean tissue growth. Maternal nutritional treatment did not influence hepatic gene expression (P ≥ 0.06). These data suggest that maternal nutrition may impact progeny muscle development, while maintaining metabolic function of the liver.

Fli1 Promotes Vascular Morphogenesis by Regulating Endothelial Potential of Multipotent Myogenic Progenitors.

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