Molecular characterization of the BTG2 and BTG3 genes in fetal muscle development of pigs

miR-103-3p Regulates the Proliferation and Differentiation of C2C12 Myoblasts by Targeting BTG2

Skeletal muscle, a vital and intricate organ, plays a pivotal role in maintaining overall body metabolism, facilitating movement, and supporting normal daily activities. An accumulating body of evidence suggests that microRNA (miRNA) holds a crucial role in orchestrating skeletal muscle growth. Therefore, the primary aim of this study was to investigate the influence of miR-103-3p on myogenesis. In our study, the overexpression of miR-103-3p was found to stimulate proliferation while suppressing differentiation in C2C12 myoblasts. Conversely, the inhibition of miR-103-3p expression yielded contrasting effects. Through bioinformatics analysis, potential binding sites of miR-103-3p with the 3'UTR region of BTG anti-proliferative factor 2 (BTG2) were predicted. Subsequently, dual luciferase assays conclusively demonstrated BTG2 as the direct target gene of miR-103-3p. Further investigation into the role of BTG2 in C2C12 myoblasts unveiled that its overexpression impeded proliferation and encouraged differentiation in these cells. Notably, co-transfection experiments showcased that the overexpression of BTG2 could counteract the effects induced by miR-103-3p. In summary, our findings elucidate that miR-103-3p promotes proliferation while inhibiting differentiation in C2C12 myoblasts by targeting BTG2.

Global Long Noncoding RNA Expression Profiling of MSTN and FGF5 Double-Knockout Sheep Reveals the Key Gatekeepers of Skeletal Muscle Development

Improving livestock and poultry growth rates and increasing meat production are urgently needed worldwide. Previously, we produced a myostatin (MSTN) and fibroblast growth factor 5 (FGF5) double-knockout (MF^-/-) sheep by CRISPR Cas9 system to improve meat production, and also wool production. Both MF^-/- sheep and the F1 generation (MF^+/-) sheep showed an obvious "double-muscle" phenotype. In this study, we identified the expression profiles of long noncoding RNAs (lncRNAs) in wild-type and MF^+/- sheep, then screened out the key candidate lncRNAs that can regulate myogenic differentiation and skeletal muscle development. These key candidate lncRNAs can serve as critical gatekeepers for muscle contraction, calcium ion transport and skeletal muscle cell differentiation, apoptosis, autophagy, and skeletal muscle inflammation, further revealing that lncRNAs play crucial roles in regulating muscle phenotype in MF^+/- sheep. In conclusion, our newly identified lncRNAs may emerge as novel molecules for muscle development or muscle disease and provide a new reference for MSTN-mediated regulation of skeletal muscle development.

Common protein-coding variants influence the racing phenotype in galloping racehorse breeds

Selection for system-wide morphological, physiological, and metabolic adaptations has led to extreme athletic phenotypes among geographically diverse horse breeds. Here, we identify genes contributing to exercise adaptation in racehorses by applying genomics approaches for racing performance, an end-point athletic phenotype. Using an integrative genomics strategy to first combine population genomics results with skeletal muscle exercise and training transcriptomic data, followed by whole-genome resequencing of Asian horses, we identify protein-coding variants in genes of interest in galloping racehorse breeds (Arabian, Mongolian and Thoroughbred). A core set of genes, G6PC2, HDAC9, KTN1, MYLK2, NTM, SLC16A1 and SYNDIG1, with central roles in muscle, metabolism, and neurobiology, are key drivers of the racing phenotype. Although racing potential is a multifactorial trait, the genomic architecture shaping the common athletic phenotype in horse populations bred for racing provides evidence for the influence of protein-coding variants in fundamental exercise-relevant genes. Variation in these genes may therefore be exploited for genetic improvement of horse populations towards specific types of racing.

Exogenous insulin promotes the expression of B-cell translocation gene 1 and 2 in chicken pectoralis

B-cell translocation genes (BTG) have been proved to play important roles in carbohydrate metabolism through modifying insulin homeostasis and glucose metabolism. This study, therefore, was conducted to investigate the effects of exogenous insulin on the expression of BTG1 and BTG2 in chickens. Twenty-four-day-old broilers and layers were fasted for 16 h and randomly assigned to insulin treatment group (subcutaneously injected with 5 IU/kg body weight) or control group (received an equivalent volume of phosphate-buffered saline). Blood glucose concentration was measured, and it showed that the blood glucose concentrations in the layers were significantly (P < 0.05) higher than that in the broilers under fasting state. Response to exogenous insulin, the blood glucose concentrations were greatly reduced in both breeds. Of note, the blood glucose concentration restored to 62% of the basal state at 240 min (P < 0.05) after insulin stimulation in layers, whereas it was still in low level until 240 min in broilers (under fast state). Tissue profiling revealed that both BTG1 and BTG2 were abundantly expressed in the skeletal muscles of broilers. A negative correlation was observed between blood glucose and BTG1 (ρ = −0.289, P = 0.031) /BTG2 (ρ = −0.500, P < 0.001) in pectoralis, and BTG1 (ρ = −0.462, P < 0.001) in pancreas. As blood glucose decreased due to exogenous insulin administration (under fast state), the expression of both BTG1 and BTG2 notably upregulated in birds’ pectoralis at 120 min and/or 240 min, meanwhile pancreas BTG1 was also upregulated. Re-feeding at 120 min elevated the blood glucose and reduced the expression of BTG genes in pectoralis generally. In addition, the change of BTG1 and BTG2 expression showed distinct difference between layers and broilers at 120 min and 240 min after insulin stimulation in pectoralis, pancreas and heart tissue; even after re-feeding at 120 min, BTG2 expression at 240 min after insulin injection was downregulated in the pectoralis of layers, while it was upregulated in that broilers. Collectively, these results indicated that response to exogenous insulin, chicken blood glucose exhibited breed-specific dynamic change, and meanwhile the expressions of both BTG1 and BTG2 genes in chickens were significantly altered by exogenous insulin in a breed- and tissue-specific manner. BTG1 and BTG2 genes may negatively regulate bird's blood glucose by promoting the glucose uptake corporately in pectoralis, and through regulating the insulin secretion in pancreas (especially BTG1).

Concordant and Heterogeneity of Single-Cell Transcriptome in Cardiac Development of Human and Mouse

Normal heart development is vital for maintaining its function, and the development process is involved in complex interactions between different cell lineages. How mammalian hearts develop differently is still not fully understood. In this study, we identified several major types of cardiac cells, including cardiomyocytes (CMs), fibroblasts (FBs), endothelial cells (ECs), ECs/FBs, epicardial cells (EPs), and immune cells (macrophage/monocyte cluster, MACs/MONOs), based on single-cell transcriptome data from embryonic hearts of both human and mouse. Then, species-shared and species-specific marker genes were determined in the same cell type between the two species, and the genes with consistent and different expression patterns were also selected by constructing the developmental trajectories. Through a comparison of the development stage similarity of CMs, FBs, and ECs/FBs between humans and mice, it is revealed that CMs at e9.5 and e10.5 of mice are most similar to those of humans at 7 W and 9 W, respectively. Mouse FBs at e10.5, e13.5, and e14.5 are correspondingly more like the same human cells at 6, 7, and 9 W. Moreover, the e9.5-ECs/FBs of mice are most similar to that of humans at 10W. These results provide a resource for understudying cardiac cell types and the crucial markers able to trace developmental trajectories among the species, which is beneficial for finding suitable mouse models to detect human cardiac physiology and related diseases.

An Integrative Analysis of Transcriptome and GWAS Data to Identify Potential Candidate Genes Influencing Meat Quality Traits in Pigs

Understanding the genetic factors behind meat quality traits is of great significance to animal breeding and production. We previously conducted a genome-wide association study (GWAS) for meat quality traits in a White Duroc × Erhualian F2 pig population using Illumina porcine 60K SNP data. Here, we further investigate the functional candidate genes and their network modules associated with meat quality traits by integrating transcriptomics and GWAS information. Quantitative trait transcript (QTT) analysis, gene expression QTL (eQTL) mapping, and weighted gene co-expression network analysis (WGCNA) were performed using the digital gene expression (DGE) data from 493 F2 pig's muscle and liver samples. Among the quantified 20,108 liver and 23,728 muscle transcripts, 535 liver and 1,014 muscle QTTs corresponding to 416 and 721 genes, respectively, were found to be significantly (p < 5 × 10^-4) correlated with 22 meat quality traits measured on longissiums dorsi muscle (LM) or semimembranosus muscle (SM). Transcripts associated with muscle glycolytic potential (GP) and pH values were enriched for genes involved in metabolic process. There were 42 QTTs (for 32 genes) shared by liver and muscle tissues, of which 10 QTTs represent GP- and/or pH-related genes, such as JUNB, ATF3, and PPP1R3B. Furthermore, a genome-wide eQTL mapping revealed a total of 3,054 eQTLs for all annotated transcripts in muscle (p < 2.08 × 10^-5), including 1,283 cis-eQTLs and 1771 trans-eQTLs. In addition, WGCNA identified five modules relevant to glycogen metabolism pathway and highlighted the connections between variations in meat quality traits and genes involved in energy process. Integrative analysis of GWAS loci, eQTL, and QTT demonstrated GALNT15/GALNTL2 and HTATIP2 as strong candidate genes for drip loss and pH drop from postmortem 45 min to 24 h, respectively. Our findings provide valuable insights into the genetic basis of meat quality traits and greatly expand the number of candidate genes that may be valuable for future functional analysis and genetic improvement of meat quality.

Comparative Transcriptome Profile Analysis of Longissimus dorsi Muscle Tissues From Two Goat Breeds With Different Meat Production Performance Using RNA-Seq

Carcass weight, meat quality and muscle components are important traits economically and they underpin most of the commercial return to goat producers. In this study, the Longissimus dorsi muscle tissues were collected from five Liaoning cashmere (LC) goats and five Ziwuling black (ZB) goats with phenotypic difference in carcass weight, some meat quality traits and muscle components. The histological quantitative of collagen fibers and the transcriptome profiles in the Longissimus dorsi muscle tissues were investigated using Masson-trichrome staining and RNA-Seq, respectively. The percentage of total collagen fibers in the Longissimus dorsi muscle tissues from ZB goats was less than those from LC goats, suggesting that these ZB goats had more tender meat. An average of 15,919 and 15,582 genes were found to be expressed in Longissimus dorsi muscle tissues from LC and ZB goats, respectively. Compared to LC goats, the expression levels of 78 genes were up-regulated in ZB goats, while 133 genes were down-regulated. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the differentially expressed genes (DEGs) were significantly enriched in GO terms related to the muscle growth and development and the deposition of intramuscular fat and lipid metabolism, hippo signaling pathway and Jak-STAT signaling pathway. The results provide an improved understanding of the genetic mechanisms regulating meat production performance in goats, and will help us improve the accuracy of selection for meat traits in goats using marker-assisted selection based on these differentially expressed genes obtained.

Myosin heavy chain-embryonic regulates skeletal muscle differentiation during mammalian development

Myosin heavy chain-embryonic (MyHC-emb) is a skeletal muscle-specific contractile protein expressed during muscle development. Mutations in MYH3, the gene encoding MyHC-emb, lead to Freeman-Sheldon and Sheldon-Hall congenital contracture syndromes. Here, we characterize the role of MyHC-emb during mammalian development using targeted mouse alleles. Germline loss of MyHC-emb leads to neonatal and postnatal alterations in muscle fiber size, fiber number, fiber type and misregulation of genes involved in muscle differentiation. Deletion of Myh3 during embryonic myogenesis leads to the depletion of the myogenic progenitor cell pool and an increase in the myoblast pool, whereas fetal myogenesis-specific deletion of Myh3 causes the depletion of both myogenic progenitor and myoblast pools. We reveal that the non-cell-autonomous effect of MyHC-emb on myogenic progenitors and myoblasts is mediated by the fibroblast growth factor (FGF) signaling pathway, and exogenous FGF rescues the myogenic differentiation defects upon loss of MyHC-emb function in vitro Adult Myh3 null mice exhibit scoliosis, a characteristic phenotype exhibited by individuals with Freeman-Sheldon and Sheldon-Hall congenital contracture syndrome. Thus, we have identified MyHC-emb as a crucial myogenic regulator during development, performing dual cell-autonomous and non-cell-autonomous functions.This article has an associated 'The people behind the papers' interview.

Effects of long-term feeding of rapeseed meal on skeletal muscle transcriptome, production efficiency and meat quality traits in Norwegian Landrace growing-finishing pigs

This study was performed to investigate the effects of dietary inclusion of 20% rapeseed meal (RSM) as an alternative to soybean meal (SBM) in a three-month feeding experiment with growing finishing pigs. Dietary alteration affected growth performance, several carcass traits and transcriptional responses in the skeletal muscle, but did not affect measured meat quality traits. In general, pigs fed the RSM test diet exhibited reduced growth performance compared to pigs on SBM control diet. Significant transcriptional changes in the skeletal muscle of growing pigs fed RSM diet were likely the consequence of an increased amount of fiber and higher polyunsaturated fatty acids, and presence of bioactive phytochemicals, such as glucosinolates. RNAseq pipeline using Tophat2-Cuffdiff identified 57 upregulated and 63 downregulated genes in RSM compared to SBM pigs. Significantly enriched among downregulated pathways was p53-mediated signalling involved in cellular proliferation, while activation of negative growth regulators (IER5, KLF10, BTG2, KLF11, RETREG1, PRUNE2) in RSM fed pigs provided further evidence for reduced proliferation and increased cellular death, in accordance with the observed reduction in performance traits. Upregulation of well-known metabolic controllers (PDK4, UCP3, ESRRG and ESRRB), involved in energy homeostasis (glucose and lipid metabolism, and mitochondrial function), suggested less available energy and nutrients in RSM pigs. Furthermore, several genes supported more pronounced proteolysis (ABTB1, OTUD1, PADI2, SPP1) and reduced protein synthesis (THBS1, HSF4, AP1S2) in RSM muscle tissue. In parallel, higher levels of NR4A3, PDK4 and FGF21, and a drop in adropin, ELOVL6 and CIDEC/FSP27 indicated increased lipolysis and fatty acid oxidation, reflective of lower dressing percentage. Finally, pigs exposed to RSM showed greater expression level of genes responsive to oxidative stress, indicated by upregulation of GPX1, GPX2, and TXNIP.

Genome Analysis Reveals Genetic Admixture and Signature of Selection for Productivity and Environmental Traits in Iraqi Cattle

The Near East cattle are adapted to different agro-ecological zones including desert areas, mountains habitats, and humid regions along the Tigris and Euphrates rivers system. The region was one of the earliest and most significant areas of cattle husbandry. Currently, four main breeds of Iraqi cattle are recognized. Among these, the Jenoubi is found in the southern more humid part of Iraq, while the Rustaqi is found in the middle and drier region of the country. Despite their importance, Iraqi cattle have up to now been poorly characterized at the genome level. Here, we report at a genome-wide level the diversity and signature of positive selection in these two breeds. Thirty-five unrelated Jenoubi cattle, sampled in the Maysan and Basra regions, and 60 Rustaqi cattle, from around Baghdad and Babylon, were genotyped using the Illumina Bovine HD BeadChip (700K). Genetic population structure and diversity level were studied using principal component analysis (PCA), expected heterozygosity (He), observed heterozygosity (Ho), and admixture. Signatures of selection were studied using extended haplotype homozygosity (EHH) (iHS and Rsb) and inter-population Wright's Fst. The results of PCA and admixture analysis, including European taurine, Asian indicine, African indicine, and taurine indicate that the two breeds are crossbreed zebu × taurine, with more zebu background in Jenoubi cattle compared with Rustaqi. The Rustaqi has the greatest mean heterozygosity (He = 0.37) among all breeds. iHS and Rsb signatures of selection analyses identify 68 candidate genes under positive selection in the two Iraqi breeds, while Fst analysis identifies 220 candidate genes including genes related to the innate and acquired immunity responses, different environmental selection pressures (e.g., tick resistance and heat stress), and genes of commercial interest (e.g., marbling score).

Overexpression of Tbx20 in Adult Cardiomyocytes Promotes Proliferation and Improves Cardiac Function After Myocardial Infarction

BACKGROUND

Adult mammalian cardiomyocytes (CMs) have the potential to proliferate, but this is not sufficient to generate adequate CMs after myocardial infarction (MI). The transcription factor Tbx20 is required for CM proliferation during development and adult CM homeostasis. The ability of Tbx20 overexpression (Tbx20(OE)) to promote adult CM proliferation and to improve cardiac function after MI was examined.

METHODS AND RESULTS

Tbx20(OE) was induced specifically in adult mouse differentiated CMs. Increased CM proliferation and fetal-like characteristics were found in Tbx20(OE) hearts compared with controls without causing pathology 4 weeks after Tbx20(OE) at baseline. Moreover, Tbx20(OE) in adult CM after MI significantly improved survival, cardiac function, and infarct size 4 weeks after MI. Improved cardiac repair, as indicated by increased CM proliferation and capillary density, was observed in the MI border zone of Tbx20(OE) hearts compared with controls. Expression of proliferation activator (cyclin D1, E1, and IGF1) and fetal contractile protein (ssTNI, βMHC) mRNA was increased whereas negative cell-cycle regulators (p21, Meis1) were decreased in Tbx20(OE) hearts compared with controls under both baseline and MI conditions. Tbx20(OE) in adult hearts activates multiple proproliferation pathways, including Akt, YAP and BMP. Interestingly, p21, Meis1, and a novel cell-cycle inhibitory gene, Btg2, are directly bound and repressed by Tbx20 with induction of proliferation in neonatal CM.

CONCLUSIONS

Tbx20(OE), specifically in adult CM, activates multiple cardiac proliferative pathways, directly represses cell-cycle inhibitory genes p21, Meis1, and Btg2, promotes adult CM proliferation; and preserves cardiac performance after MI.

MiR-21 Protected Cardiomyocytes against Doxorubicin-Induced Apoptosis by Targeting BTG2

Doxorubicin (DOX) is an anthracycline drug with a wide spectrum of antineoplastic activities. However, it causes cardiac cytotoxicity, and this limits its clinical applications. MicroRNA-21 (miR-21) plays a vital role in regulating cell proliferation and apoptosis. While miR-21 is preferentially expressed in adult cardiomyocytes and involved in cardiac development and heart disease, little is known regarding its biological functions in responding to DOX-induced cardiac cytotoxicity. In this study, the effects of DOX on mouse cardiac function and the expression of miR-21 were examined in both mouse heart tissues and rat H9C2 cardiomyocytes. The results showed that the cardiac functions were more aggravated in chronic DOX injury mice compared with acute DOX-injury mice; DOX treatment significantly increased miR-21 expression in both mouse heart tissue and H9C2 cells. Over-expression of miR-21 attenuated DOX-induced apoptosis in cardiamyocytes whereas knocking down its expression increased DOX-induced apoptosis. These gain- and loss- of function experiments showed that B cell translocation gene 2 (BTG2) was a target of miR-21. The expression of BTG2 was significantly decreased both in myocardium and H9C2 cells treated with DOX. The present study has revealed that miR-21 protects mouse myocardium and H9C2 cells against DOX-induced cardiotoxicity probably by targeting BTG2.

Identification of common regulators of genes in co-expression networks affecting muscle and meat properties

Understanding the genetic contributions behind skeletal muscle composition and metabolism is of great interest in medicine and agriculture. Attempts to dissect these complex traits combine genome-wide genotyping, expression data analyses and network analyses. Weighted gene co-expression network analysis (WGCNA) groups genes into modules based on patterns of co-expression, which can be linked to phenotypes by correlation analysis of trait values and the module eigengenes, i.e. the first principal component of a given module. Network hub genes and regulators of the genes in the modules are likely to play an important role in the emergence of respective traits. In order to detect common regulators of genes in modules showing association with meat quality traits, we identified eQTL for each of these genes, including the highly connected hub genes. Additionally, the module eigengene values were used for association analyses in order to derive a joint eQTL for the respective module. Thereby major sites of orchestrated regulation of genes within trait-associated modules were detected as hotspots of eQTL of many genes of a module and of its eigengene. These sites harbor likely common regulators of genes in the modules. We exemplarily showed the consistent impact of candidate common regulators on the expression of members of respective modules by RNAi knockdown experiments. In fact, Cxcr7 was identified and validated as a regulator of genes in a module, which is involved in the function of defense response in muscle cells. Zfp36l2 was confirmed as a regulator of genes of a module related to cell death or apoptosis pathways. The integration of eQTL in module networks enabled to interpret the differentially-regulated genes from a systems perspective. By integrating genome-wide genomic and transcriptomic data, employing co-expression and eQTL analyses, the study revealed likely regulators that are involved in the fine-tuning and synchronization of genes with trait-associated expression.

Dietary fatty acids alter left ventricular myocardial gene expression in Wistar rats

Obesity increases the risk for cardiomyopathy in the absence of comorbidities. Myocardial structure is modified by dietary fatty acids. Left ventricular hypertrophy is associated with Western (WES) diet consumption, whereas intake of n-3 polyunsaturated fatty acids is associated with antihypertrophic effects. We previously observed no attenuation of left ventricular thickening after 3 months of docosahexaenoic acid (DHA) supplementation of a WES diet, compared with WES diet intake alone, in rats that had similar weight, adiposity, and insulin sensitivity to control animals. The objective of this study was to define left ventricular gene expression in these animals to determine whether diet alone was associated with a physiologic or pathologic hypertrophic response. We hypothesized that WES diet consumption would favor a pathologic or maladaptive myocardial gene expression pattern and that DHA supplementation would favor a physiologic or adaptive response. Microarray analysis identified 64 transcripts that were differentially expressed (P ≤ .001) within one or more treatment comparisons. Using quantitative real-time polymerase chain reaction, 29 genes with fold change at least 1.74 were successfully validated; all but 3 had similar directionality to that observed using microarray, and 2 genes, connective tissue growth factor and cathepsin M, were differentially expressed according to diet. WES blot analysis was performed on 4 proteins relevant to myocardial hypertrophy and metabolism. Acyl-CoA thioesterase 1, B-cell translocation gene 2, and carbonic anhydrase III showed directional change consistent with gene expression. Retinol saturase (all-trans-retinol 13,14-reductase), although not consistent with gene expression, was different according to diet, with increased concentrations in WES-fed rats compared with control and DHA-supplemented animals. Diet did not distinguish a transcriptome reflecting physiologic or pathologic myocardial hypertrophy; furthermore, the modest changes observed suggest that obesity and associated comorbidities may play a larger role than mere dietary fatty acid composition in development of cardiomyopathy.

Six placenta permeability-related genes: molecular characterization and expression analysis in pigs

The nutrient transportation ability of placenta depends on placental size, vascular density and permeability. Regulation of angiogenesis in the placenta is critical for successful gestation. Placenta vascularity exhibits disparity in different gestation stages and different pig breeds. To investigate the expression of genes related to permeability in the porcine placenta of different gestation stages and breeds, molecular cloning and gene expression analysis of six porcine genes, vascular endothelial growth factor (VEGF), VEGF-R1, VEGF-R2, endothelial nitric oxide synthase (eNOS), vascular endothelial cadherin (CDH5) and β-arrestin2 (Arrb2), were performed in this study. The results demonstrated that from gestation day 33 to day 90, Landrace exhibited significant increase (P < 0.05) in placental VEGF and Arrb2 mRNA expression. Moreover, expression levels of VEGF, VEGF-R1, VEGF-R2 and eNOS mRNA were higher (P < 0.01) in the placenta of Erhualian than those in Landrace on day 90 of gestation. In contrast, CDH5 placental mRNA expression level exhibited significant decrease (P < 0.05) from day 33 to day 90 gestation in Landrace. Erhualian placental CDH5 and Arrb2 expression levels were significantly lower (P < 0.01) than those in Landrace conceptuses on day 90 of gestation. Our study offered new data on the expression of genes in VEGF signal transduction pathway in porcine placenta.

Molecular characterization of Tob1 in muscle development in pigs

Cell proliferation is an important biological process during myogenesis. Tob1 encoded a member of the Tob/BTG family of anti-proliferative proteins. Our previous LongSAGE (Long Serial Analysis of Gene Expression) analysis suggested that Tob1 was differentially expressed during prenatal skeletal muscle development. In this study, we isolated and characterized the swine Tob1 gene. Subsequently, we examined Tob1 chromosome assignment, subcellular localization and dynamic expression profile in prenatal skeletal muscle (33, 65 and 90 days post-conception, dpc) from Landrace (lean-type) and Tongcheng pigs (obese-type). The Tob1 gene was mapped to pig chromosome 12 (SSC12). The Tob1 protein was distributed throughout the nucleus and cytoplasm of PK15 cells. During prenatal skeletal muscle development, Tob1 was up-regulated and highly expressed in skeletal muscle at 90 dpc in Tongcheng pigs but peaked at 65 dpc in Landrace pigs. This result suggested that there were different proliferation patterns during myogenesis between Tongcheng and Landrace pigs. During postnatal skeletal muscle development, the expression of Tob1 increased with aging, indicating that the proliferation potential of myoblasts decreased in postnatal muscle development. In tissues of adult wuzhishan miniature pigs, the Tob1 gene was highly expressed in skeletal muscle. The expression of Tob1 was significantly increased at day 6 during C2C12 differentiation time, suggesting a possible role in skeletal muscle development. Therefore, this study indicated that Tob1 perhaps played an important role in skeletal muscle development.

Molecular characterization of caveolin-1 in pigs infected with Haemophilus parasuis

Caveolin-1 (Cav1) plays a critical role in the invasion of pathogenic microbes into host cells, yet little is known about porcine Cav1. In this study, we provide the molecular characterization of Cav1 in pigs following stimulation with LPS/polyinosinic-polycytidylic acid as well as during infection with Haemophilus parasuis. The porcine Cav1 gene is 35 kb long and is located at SSC18q21; two isoforms (Cav1-α and Cav1-β) are produced by alternative splicing. Three point mutations were identified in the coding region of the gene, two of which were significantly associated with nine immunological parameters in Landrace pigs, including the Ab response against porcine reproductive and respiratory syndrome virus and lymphocyte counts. Promoter analysis indicated that NF-κB activates both Cav1 transcripts, but the forkhead gene family specifically regulates Cav1-β in the pig. Porcine Cav1 is expressed ubiquitously, with Cav1-α more abundantly expressed than Cav1-β in all tissues investigated. Basal expression levels of Cav1 in PBMCs are relatively similar across different pig breeds. LPS and polyinosinic-polycytidylic acid markedly induced the expression of Cav1 in porcine kidney-15 cells in vitro, likely through NF-κB activation. Pigs infected with H. parasuis exhibited decreased expression of Cav1, particularly in seriously impaired organs such as the brain. This study provides new evidence that supports the use of Cav1 as a potential diagnostic and genetic marker for disease resistance in animal breeding. In addition, our results suggest that Cav1 may be implicated in the pathogenesis of Glasser's disease, which is caused by H. parasuis.

Molecular characterization, expression pattern and association analysis of the porcine BTG2 gene

B-cell translocation gene 2 (BTG2), a member of the B-cell translocation gene family with anti-proliferative properties, have been characterized to be involved in cell growth, differentiation and survival. In this study, we cloned the full length sequences of cDNA and genomic DNA of BTG2 gene from the porcine skeletal muscle. Spatial expression analysis showed that the porcine BTG2 gene is expressed predominantly in muscle. Temporal expression analysis in longissimus dorsi muscle demonstrated that the expression of BTG2 gene has the highest expression at 60 days old in Large White while with a peak expression at 120 days old in Meishan. Temporal analysis also revealed that the expression of BTG2 gene is generally higher in Large White than in Meishan at all the developmental stages tested (65 days of conception and 3, 35, 60, 120, and 180 days of postnatal). A single nucleotide polymorphism (G417C) in the intron of BTG2 gene was then detected by PCR-RFLP in Large White × Meishan F2 resource population and association analysis suggested that this polymorphic site had significant association (P < 0.05) with the buttock fat thickness, fat percentage, lean muscle percentage, ratio of lean to fat and carcass length.

A robust linkage map of the porcine autosomes based on gene-associated SNPs

BACKGROUND

Genetic linkage maps are necessary for mapping of mendelian traits and quantitative trait loci (QTLs). To identify the actual genes, which control these traits, a map based on gene-associated single nucleotide polymorphism (SNP) markers is highly valuable. In this study, the SNPs were genotyped in a large family material comprising more than 5,000 piglets derived from 12 Duroc boars crossed with 236 Danish Landrace/Danish Large White sows. The SNPs were identified in sequence alignments of 4,600 different amplicons obtained from the 12 boars and containing coding regions of genes derived from expressed sequence tags (ESTs) and genomic shotgun sequences.

RESULTS

Linkage maps of all 18 porcine autosomes were constructed based on 456 gene-associated and six porcine EST-based SNPs. The total length of the averaged-sex whole porcine autosome was estimated to 1,711.8 cM resulting in an average SNP spacing of 3.94 cM. The female and male maps were estimated to 2,336.1 and 1,441.5 cM, respectively. The gene order was validated through comparisons to the cytogenetic and/or physical location of 203 genes, linkage to evenly spaced microsatellite markers as well as previously reported conserved synteny. A total of 330 previously unmapped genes and ESTs were mapped to the porcine autosome while ten genes were mapped to unexpected locations.

CONCLUSION

The linkage map presented here shows high accuracy in gene order. The pedigree family network as well as the large amount of meiotic events provide good reliability and make this map suitable for QTL and association studies. In addition, the linkage to the RH-map of microsatellites makes it suitable for comparison to other QTL studies.

In silico identification and molecular characterization of genes predominantly expressed in the fish oocyte

Background

In fish, molecular mechanisms that control follicle-enclosed oocyte progression throughout oogenesis and oocyte developmental competence acquisition remain poorly understood. Existing data in mammals have indicated that the so called "oocyte-specific" genes play an important role in oogenesis, fertilization, and early embryo development. In teleost species, very little is known about "oocyte-specific" genes. The present study therefore aimed at identifying and characterizing oocyte-specific genes in fish.

Results

Using digital differential display PCR, mouse ESTs exhibiting an oocyte-predominant expression were identified. Those murine ESTs were subsequently used to identify cognate rainbow trout (Oncorhynchus mykiss) ESTs using a reciprocal Blast search strategy. In the present study we report the identification of five previously uncharacterized rainbow trout cDNAs exhibiting a oocyte-specific, oocyte-predominant, or gonad-specific expression: zygote arrest 1 (zar1), v-mos Moloney murine sarcoma viral oncogene-like protein (mos), B-cell translocation gene (btg3), growth differentiation factor 9 (gdf9), and mutS homolog 4 (msh4). The orthology relationship of each of these genes with vertebrate counterparts was verified by phylogenetic analysis. Among those five genes, three had never been characterized in any fish species. In addition, we report the oocyte-predominant expression of btg3 for the first time in any vertebrate species. Finally, those five genes are present in unfertilized eggs as maternally-inherited mRNAs thus suggesting that they could participate in ovarian folliculogenesis as well as early embryonic development.

Conclusion

The expression patterns of zar1, mos, btg3, gdf9 and msh4 in rainbow trout and the functions of their orthologs in higher vertebrates strongly suggest that they might play an important role in follicle-enclosed oocyte development, meiosis control and early embryonic development in fish. Future investigations are however required to unravel the participation of those strong candidates in the molecular processes that control folliculogenesis and/or oocyte developmental competence in fish.

Btg1 and Btg2 gene expression during early chick development

Btg/Tob genes encode for a new family of proteins with antiproliferative functions, which are also able to stimulate cell differentiation. Btg1 and Btg2 are the most closely related members in terms of gene sequence. We analyzed their expression patterns in avian embryos by in situ hybridization, from embryonic day 1 to 3. Btg1 was distinctively expressed in the Hensen's node, the notochord, the cardiogenic mesoderm, the lens vesicle, and in the apical ectodermal ridge and mesenchyme of the limb buds. On the other hand, Btg2 expression domains included the neural plate border, presomitic mesoderm, trigeminal placode, and mesonephros. Both genes were commonly expressed in the myotome, epibranchial placodes, and dorsal neural tube. The results suggest that Btg1 and Btg2 are involved in multiple developmental processes. Overlapping expression of Btg1 and Btg2 may imply redundant functions, but unique expression patterns suggest also differential regulation and function.