Spatial and temporal requirement of Mlp60A isoforms during muscle development and function in Drosophila melanogaster

Many myofibrillar proteins undergo isoform switching in a spatio-temporal manner during muscle development. The biological significance of the variants of several of these myofibrillar proteins remains elusive. One such myofibrillar protein, the Muscle LIM Protein (MLP), is a vital component of the Z-discs. In this paper, we show that one of the Drosophila MLP encoding genes, Mlp60A, gives rise to two isoforms: a short (279 bp, 10 kDa) and a long (1461 bp, 54 kDa) one. The short isoform is expressed throughout development, but the long isoform is adult-specific, being the dominant of the two isoforms in the indirect flight muscles (IFMs). A concomitant, muscle-specific knockdown of both isoforms leads to late pupal lethality, with the surviving flies being majorly flight defective. Mlp60A null flies show developmental lethality, and muscle defects in the individuals surviving till the third instar larval stage. This lethality could be rescued partially by muscle-specific overexpression of the short isoform. Almost 90% of the long isoform-specific P-element insertion mutant flies show a compromised flight ability and have reduced sarcomere length. Hence, our data shows that the two Mlp60A isoforms are functionally specialized, to ensuring normal embryonic muscle development and adult flight muscle function.

Genome-Wide Analysis of H3K27me3 in Porcine Embryonic Muscle Development

The trimethylation of histone H3 lysine 27 (H3K27me3) is one of the most important chromatin modifications, which is generally presented as a repressive mark in various biological processes. However, the dynamic and global-scale distribution of H3K27me3 during porcine embryonic muscle development remains unclear. Here, our study provided a comprehensive genome-wide view of H3K27me3 and analyzed the matching transcriptome in the skeletal muscles on days 33, 65, and 90 post-coitus from Duroc fetuses. Transcriptome analysis identified 4,124 differentially expressed genes (DEGs) and revealed the key transcriptional properties in three stages. We found that the global H3K27me3 levels continually increased during embryonic development, and the H3K27me3 level was negatively correlated with gene expression. The loss of H3K27me3 in the promoter was associated with the transcriptional activation of 856 DEGs in various processes, including skeletal muscle development, calcium signaling, and multiple metabolic pathways. We also identified for the first time that H3K27me3 could enrich in the promoter of genes, such as DES, MYL1, TNNC1, and KLF5, to negatively regulate gene expression in porcine satellite cells (PSCs). The loss of H3K27me3 could promote muscle cell differentiation. Taken together, this study provided the first genome-wide landscape of H3K27me3 in porcine embryonic muscle development. It revealed the complex and broad function of H3K27me3 in the regulation of embryonic muscle development from skeletal muscle morphogenesis to myofiber maturation.

Transcriptome analysis of embryonic muscle development in Chengkou Mountain Chicken

Background Muscle is the predominant portion of any meat product, and growth performance and product quality are the core of modern breeding. The embryonic period is highly critical for muscle development, the number, shape and structure of muscle fibers are determined at the embryonic stage. Herein, we performed transcriptome analysis to reveal the law of muscle development in the embryonic stage of Chengkou Mountain Chicken at embryonic days (E) 12, 16, 19, 21. Results Diameter and area of muscle fibers exhibited significant difference at different embryonic times(P < 0.01). A total of 16,330 mRNAs transcripts were detected, including 109 novel mRNAs transcripts. By comparing different embryonic muscle development time points, 2,262 in E12vsE16, 5,058 in E12vsE19, 6139 in E12vsE21, 1,282 in E16vsE19, 2,920 in E16vsE21, and 646 in E19vsE21differentially expressed mRNAs were identified. It is worth noting that 7,572 mRNAs were differentially expressed. The time-series expression profile of differentially expressed genes (DEGs) showed that the rising and falling expression trends were significantly enriched. The significant enrichment trends included 3,150 DEGs. GO enrichment analysis provided three significantly enriched categories of significantly enriched differential genes, including 65 cellular components, 88 molecular functions, and 453 biological processes. Through KEGG analysis, we explored the biological metabolic pathways involved in differentially expressed genes. A total of 177 KEGG pathways were enriched, including 19 significant pathways, such as extracellular matrix-receptor interactions. Similarly, numerous pathways related to muscle development were found, including the Wnt signaling pathway (P < 0.05), MAPK signalingpathway, TGF-beta signaling pathway, PI3K-Akt signaling pathway and mTOR signaling pathway. Among the differentially expressed genes, we selected those involved in developing 4-time points; notably, up-regulated genes included MYH1F, SLC25A12, and HADHB, whereas the down-regulated genes included STMN1, VASH2, and TUBAL3. Conclusions Our study explored the embryonic muscle development of the Chengkou Mountain Chicken. A large number of DEGs related to muscle development have been identified ,and validation of key genes for embryonic development and preliminary explanation of their role in muscle development. Overall, this study broadened our current understanding of the phenotypic mechanism for myofiber formation and provides valuable information for improving chicken quality.

The landscape of chromatin accessibility in skeletal muscle during embryonic development in pigs

Background The development of skeletal muscle in pigs during the embryonic stage is precisely regulated by transcriptional mechanisms, which depend on chromatin accessibility. However, how chromatin accessibility plays a regulatory role during embryonic skeletal muscle development in pigs has not been reported. To gain insight into the landscape of chromatin accessibility and the associated genome-wide transcriptome during embryonic muscle development, we performed ATAC-seq and RNA-seq analyses of skeletal muscle from pig embryos at 45, 70 and 100 days post coitus (dpc). Results In total, 21,638, 35,447 and 60,181 unique regions (or peaks) were found across the embryos at 45 dpc (LW45), 70 dpc (LW70) and 100 dpc (LW100), respectively. More than 91% of the peaks were annotated within − 1 kb to 100 bp of transcription start sites (TSSs). First, widespread increases in specific accessible chromatin regions (ACRs) from embryos at 45 to 100 dpc suggested that the regulatory mechanisms became increasingly complicated during embryonic development. Second, the findings from integrated ATAC-seq and RNA-seq analyses showed that not only the numbers but also the intensities of ACRs could control the expression of associated genes. Moreover, the motif screening of stage-specific ACRs revealed some transcription factors that regulate muscle development-related genes, such as MyoG, Mef2c, and Mef2d. Several potential transcriptional repressors, including E2F6, OTX2 and CTCF, were identified among the genes that exhibited different regulation trends between the ATAC-seq and RNA-seq data. Conclusions This work indicates that chromatin accessibility plays an important regulatory role in the embryonic muscle development of pigs and regulates the temporal and spatial expression patterns of key genes in muscle development by influencing the binding of transcription factors. Our results contribute to a better understanding of the regulatory dynamics of genes involved in pig embryonic skeletal muscle development.

The landscape of chromatin accessibility in skeletal muscle during embryonic development in pigs

Background: The development of skeletal muscle during the embryonic stage in pigs is precisely regulated by transcriptional mechanisms, which depends on chromatin accessibility. However, the landscape of chromatin accessibility in skeletal muscle during embryonic development in pigs has not been reported. To gain insight into the landscape of chromatin accessibility and the associated genome-wide transcriptome during embryonic muscle development, we performed ATAC-seq and RNA-seq on skeletal muscle of pig embryos at 45, 70 and 100 days post coitus (dpc).Results: In total, 21638, 35447 and 60181 unique regions (or peaks) were found across 45 dpc (LW45), 70 dpc (LW70) and 100 dpc (LW100) embryos, respectively. More than 91% of peaks were annotated within -1 kb to 100 bp of transcription start sites (TSSs). First, widespread increases in specific accessible chromatin regions (ACRs) from 45 to 100 dpc embryos suggested that the regulatory mechanisms became increasingly complicated during embryonic development. Second, the findings of integrated ATAC-seq and RNA-seq analyses showed that not only the numbers but also the peak intensities of ACRs could control the expression of associated genes. Finally, motif screening of stage-specific ACRs revealed some transcription factors that regulated muscle development-related genes, such as MyoD, Mef2c, and Mef2d. Motif screening of DPI of common peaks detected that a potential transcriptional repressor, namely CTCF, was identified among those genes that exhibited different change trends between the ATAC-seq and RNA-seq data.Conclusions: This work indicates that chromatin accessibility plays an important regulatory role in the embryonic muscle development of pigs and regulates the temporal and spatial expression patterns of key genes in muscle development by influencing the binding of transcription factors. Our results contribute to a better understanding of the regulatory dynamics of genes involved in pig embryonic skeletal muscle development.

Transcriptome Analysis of Embryonic Muscle Development in Chengkou Mountain Chicken

Background: Muscle is the predominant portion of any meat product, and growth performance and product quality are the core of modern breeding. The embryonic period is highly critical for muscle development, the number, shape and structure of muscle fibers are determined at the embryonic stage. Herein, we performed transcriptome analysis to reveal the law of muscle development in the embryonic stage of Chengkou Mountain Chicken at embryonic days (E) 12, 16, 19, 21. Results: Diameter and area of muscle fibers exhibited significant difference at different embryonic times(P<0.01). A total of 16,330 mRNAs transcripts were detected, including 109 novel mRNAs transcripts. By comparing different embryonic muscle development time points, 2,251 (E12vsE16), 4,324 (E12vsE19), and 5,224 (E12vsE21), 1,274 (E16vsE19), 2,735 (E16vsE21) and 857 (E19vsE21) differentially expressed mRNAs were identified. It is worth noting that 6,726 mRNAs were differentially expressed. The time-series expression profile of differentially expressed genes (DEGs) showed that the rising and falling expression trends were significantly enriched. The downward trend was the most important and was enriched in 3,963 DEGs. GO enrichment analysis provided three significantly enriched categories of the down-trending genes, including 91 cellular components, 53 molecular functions, and 248 biological processes. Through KEGG analysis, we explored the pathway of downtrend genes. A total of 183 KEGG pathways were enriched, including 17 significant pathways, such as extracellular matrix-receptor interactions. Similarly, numerous pathways related to muscle development were found, including the Wnt signaling pathway (P<0.05), MAPK signalingpathway, TGF-beta signaling pathway, and mTOR signaling pathway. Among the differentially expressed genes, we selected those involved in developing 4-time points; notably, up-regulated genes included MYH1F, SLC25A12, and HADHB, whereas the down-regulated genes included STMN1, VASH2, and TUBAL3. Conclusion: Our study explored the embryonic muscle development of the Chengkou Mountain Chicken. A large number of DEGs related to muscle development have been identified ,and validation of key genes for embryonic development and preliminary explanation of their role in muscle development. Overall, this study broadened our current understanding of the phenotypic mechanism for myofiber formation and provides valuable information for improving chicken quality.

The Landscape of Chromatin Accessibility in Skeletal Muscle During Embryonic Development in Pigs

Background: The development of skeletal muscle during the embryonic stage in pigs is precisely regulated by transcriptional regulation, which depends on chromatin accessibility. However, how chromatin accessibility plays a regulatory role during embryonic skeletal muscle development in pigs has not been reported. To gain insight into the landscape of chromatin accessibility and the associated genome-wide transcriptome during embryonic muscle development, we performed ATAC-seq and RNA-seq on skeletal muscle of pig embryos at 45, 70 and 100 days post coitus (dpc). Results: In total, 21638, 35447 and 60181 unique regions (or peaks) were found across 45 dpc (LW45), 70 dpc (LW70) and 100 dpc (LW100) embryos, respectively. More than 91% of peaks were annotated within -1 kb to 100 bp of transcription start sites (TSSs). First, widespread increases in specific accessible chromatin regions (ACRs) from 45 to 100 dpc embryos suggested that the regulatory mechanisms became increasingly complicated during embryonic development. Second, the findings of integrated ATAC-seq and RNA-seq analyses showed that not only the numbers but also the peak intensities of ACRs could control the expression of associated genes. Finally, motif screening of stage-specific ACRs revealed some transcription factors that regulated muscle development-related genes, such as MyoD, Mef2c, Mef2d and Pax7. Several potential transcriptional repressors, including E2F6, GRHL2, OTX2 and CTCF, were identified among those genes that exhibited different change trends between the ATAC-seq and RNA-seq data. Conclusions: This work indicates that chromatin accessibility plays an important regulatory role in the embryonic muscle development of pigs and regulates the temporal and spatial expression patterns of key genes in muscle development by influencing the binding of transcription factors. Our results contribute to a better understanding of the regulatory dynamics of genes involved in pig embryonic skeletal muscle development.

A novel transcript of MEF2D promotes myoblast differentiation and its variations associated with growth traits in chicken

Background Development of skeletal muscle is closely related to broiler production traits. The myocyte-specific enhancer binding factor (MEF) 2D gene (MEF2D) and its variant transcripts play important parts in myogenesis. Methods To identify the transcript variants of chicken MEF2D gene and their function, this study cloned chicken MEF2D gene and identified its transcript variants from different tissue samples. The expression levels of different transcripts of MEF2D gene in different tissues and different periods were measured, and their effects on myoblast proliferation and differentiation were investigated. Variations in MEF2D were identified and association analysis with chicken production traits carried out. Results Four novel transcript variants of MEF2D were obtained, all of which contained highly conserved sequences, including MADS-Box and MEF2-Domain functional regions. Transcript MEF2D-V4 was expressed specifically in muscle, and its expression was increased during embryonic muscle development. The MEF2D-V4 could promote differentiation of chicken myoblasts and its expression was regulated by RBFOX2. The single nucleotide polymorphism g.36186C > T generated a TAG stop codon, caused MEF2D-V4 to terminate translation early, and was associated with several growth traits, especially on early body weight. Conclusion We cloned the muscle-specific transcript of MEF2D and preliminarily revealed its role in embryonic muscle development.