Evaluation and Validation of the Six Housekeeping Genes for Normalizing Mrna Expression in the Ovarian Follicles and Several Tissues in Chicken

Expression of housekeeping genes is relatively constant in different tissues and cells by RT-qPCR analysis. Housekeeping genes (HGs) are usually utilized as the reference to evaluate and compare mRNA expression abundances of target genes in different cells or tissues sampled. However, the expression stabilities of different HGs in diverse samples may appear divergence. Currently, there is no exact reference data of HGs in hen ovarian follicular tissues during egg-laying period available yet. In this study, we detected the expression of 18SrRNA, ACTB, HOXC8, GAPDH, alpha-A, and alpha-D mRNA in the varied-size ovarian follicles (1-8 mm in diameter and F5), hearts, livers, spleens, lungs, and breast muscles of the laying hens by RT-qPCR, to analyze the results via Ct value, geNorm, Normfinder, and Bestkeeper. The data showed that the expression levels of 18SrRNA, alpha-A, and alpha-D transcripts were more significantly stable than the other three genes for normalizing mRNA expression in the hen ovarian follicles examination. Moreover, alpha-D, 18SrRNA, and alpha-A were also most suitable for the expression normalization in the tissues of the heart, liver, spleen, lung and breast muscle. In contrast, 18SrRNA has the most stable mRNA expression levels in all tissues sampled, so it can serve as an excellent inner control for the evaluation of the transcription levels in chickens. It is a remarkable fact that HOXC8 as a candidate reference should be avoided. Our study establishes a set of stably expressed candidate inner references in the hen ovarian follicles and several tissues, it firstly provided an exact data for validation of the inner references in normalizing transcription levels of a target gene in chickens.

Evaluation and Validation of the Six Housekeeping Genes for Normalizing Mrna Expression in the Ovarian Follicles and Several Tissues in Chicken

Expression of housekeeping genes is relatively constant in different tissues and cells by RT-qPCR analysis. Housekeeping genes (HGs) are usually utilized as the reference to evaluate and compare mRNA expression abundances of target genes in different cells or tissues sampled. However, the expression stabilities of different HGs in diverse samples may appear divergence. Currently, there is no exact reference data of HGs in hen ovarian follicular tissues during egg-laying period available yet. In this study, we detected the expression of 18SrRNA, ACTB, HOXC8, GAPDH, alpha-A, and alpha-D mRNA in the varied-size ovarian follicles (1-8 mm in diameter and F5), hearts, livers, spleens, lungs, and breast muscles of the laying hens by RT-qPCR, to analyze the results via Ct value, geNorm, Normfinder, and Bestkeeper. The data showed that the expression levels of 18SrRNA, alpha-A, and alpha-D transcripts were more significantly stable than the other three genes for normalizing mRNA expression in the hen ovarian follicles examination. Moreover, alpha-D, 18SrRNA, and alpha-A were also most suitable for the expression normalization in the tissues of the heart, liver, spleen, lung and breast muscle. In contrast, 18SrRNA has the most stable mRNA expression levels in all tissues sampled, so it can serve as an excellent inner control for the evaluation of the transcription levels in chickens. It is a remarkable fact that HOXC8 as a candidate reference should be avoided. Our study establishes a set of stably expressed candidate inner references in the hen ovarian follicles and several tissues, it firstly provided an exact data for validation of the inner references in normalizing transcription levels of a target gene in chickens.(AU)

PDK2 promotes chondrogenic differentiation of mesenchymal stem cells by upregulation of Sox6 and activation of JNK/MAPK/ERK pathway.

This study was undertaken to clarify the role and mechanism of pyruvate dehydrogenase kinase isoform 2 (PDK2) in chondrogenic differentiation of mesenchymal stem cells (MSCs). MSCs were isolated from femurs and tibias of Sprague-Dawley rats, weighing 300-400 g (5 females and 5 males). Overexpression and knockdown of PDK2 were transfected into MSCs and then cell viability, adhesion and migration were assessed. Additionally, the roles of aberrant PDK2 in chondrogenesis markers SRY-related high mobility group-box 6 (Sox6), type ΙΙ procollagen gene (COL2A1), cartilage oligomeric matrix protein (COMP), aggrecan (AGC1), type ΙX procollagen gene (COL9A2) and collagen type 1 alpha 1 (COL1A1) were measured by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The expressions of c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK) and extracellular regulated protein kinase (ERK) were measured. Overexpressing PDK2 promoted cell viability, adhesion and inhibited cell migration in MSCs (all P<0.05). qRT-PCR assay showed a potent increase in the mRNA expressions of all chondrogenesis markers in response to overexpressing PDK2 (P<0.01 or P<0.05). PDK2 overexpression also induced a significant accumulation in mRNA and protein expressions of JNK, p38MAPK and ERK in MSCs compared to the control (P<0.01 or P<0.05). Meanwhile, silencing PDK2 exerted the opposite effects on MSCs. This study shows a preliminary positive role and potential mechanisms of PDK2 in chondrogenic differentiation of MSCs. It lays the theoretical groundwork for uncovering the functions of PDK2 and provides a promising basis for repairing cartilage lesions in osteoarthritis.

GRK2 desensitizes flow-induced responses in osteoblasts.

Bone desensitization after mechanical loading is essential for bone to adapt to its mechanical environment. However, the desensitization mechanism is unknown. Previous studies suggest that G protein-coupled receptors (GPCRs), including P2Y and parathyroid hormone receptors, play important roles in osteoblast mechanobiology. Thus, for the present research, we examined the role of G protein-coupled receptor kinase 2 (GRK2) in osteoblast desensitization after exposure to mechanical stimulation. We first showed the existence of osteoblast desensitization after mechanical stimulation based on cytosol Ca2+ and phosphorylated ERK1/2 activities, detected using a fluorescent Ca2+-sensitive dye and western blotting, respectively. We then demonstrated that GRK2 overexpression in MC3T3-E1 cells inhibits flow-induced ERK1/2 phosphorylation, while siRNA knockdown of GRK2 enhances ERK1/2 phosphorylation. Additionally, we found that GRK2 overexpression in MC3T3-E1 cells inhibits cyclooxygenase-2 mRNA expression in the short term and alkaline phosphatase activity in the long term. More importantly, we discovered that GRK2 translocated to the cell membrane shortly after flow stimulation - a step necessary for GPCR desensitization. Previously, we have demonstrated that P2Y2 purinergic receptors, one type of GPCRs, are involved in various flow-induced osteoblastic responses. In this research, we also showed that GRK2 overexpression does not affect ATP release. Accordingly, GRK2 is able to inhibit flow-induced osteoblast responses possibly through desensitizing P2Y2 receptors.

Analysis of gene expression patterns and levels in maize hybrids and their parents.

Heterosis has greatly contributed to conventional plant breeding and is widely used to increase crop plant productivity. However, although some studies have explored the mechanisms of heterosis at the genomic and transcriptome level, these mechanisms still remain unclear. The growth and development of maize seedlings and immature embryos have an important impact on subsequent production. This study investigated differentially expressed genes (DEGs) between parents and reciprocal hybrids in the seedling leaves, roots, and immature embryo 15 days after pollination using amplified fragment length polymorphism (AFLP)-based transcript profiling (cDNA-AFLP). We isolated 180, 170, and 108 genes from the leaves, roots, and immature embryos, respectively, that were differentially expressed between hybrids and parents. Sequencing and functional analysis revealed that 107 transcript-derived fragments in the roots and leaves and 90 in the immature embryos were involved in known functions, whereas many DEGs had roles in plant growth and development, photosynthesis, signal transduction, and seed germination. Quantitative reverse-transcription polymerase chain reaction analysis of relative expression levels between reciprocal hybrids and both parental genotypes of selected genes produced results that were consistent with cDNA-AFLP. We validated the expression patterns of 15 selected genes related to heterosis formation and revealed that most showed non-additive expression in one or both hybrids, including dominant, underdominant, and overdominant expression. This indicates that gene-regulatory interactions among parental alleles play an important role in heterosis during the early developmental stages of maize.

Analysis of DNA methylation patterns and levels in maize hybrids and their parents.

Heterosis is the superior performance of heterozygous individuals and has been widely exploited in plant breeding, although the underlying regulatory mechanisms still remain largely elusive. To understand the molecular basis of heterosis in maize, in this study, roots and leaves at the seedling stage and embryos and endosperm tissues 15 days after fertilization of 2 elite hybrids and their parental lines were used to estimate the levels and patterns of cytosine methylation by the methylation-sensitive amplification polymorphism method. The relative total methylation levels were lower in all the tissues of all hybrids than their corresponding mid-parent values, and the number of demethylation events was higher in the hybrids. These results implied that the decreasing trend and demethylation in hybrids relative to their parents may enable the derepression and possibly expression of many genes that were associated with the phenotypic variation in hybrids. To further analyze the observed methylation pattern changes, a total of 63 differentially displayed DNA fragments were successfully sequenced. Basic Local Alignment Search Tool analysis showed that 11 fragments shared similarity with known functional proteins in maize or other plant species, including metabolism, transposon/retrotransposon, development, stress response, and signal transduction, which indicated that these genes might play a significant role in maize hybrid vigor.

Comparative analyses of genetic/epigenetic diversities and structures in a wild barley species (Hordeum brevisubulatum) using MSAP, SSAP and AFLP.

We analyzed genetic diversity and population genetic structure of four artificial populations of wild barley (Hordeum brevisubulatum); 96 plants collected from the Songnen Prairie in northeastern China were analyzed using amplified fragment length polymorphism (AFLP), specific-sequence amplified polymorphism (SSAP) and methylation-sensitive amplified polymorphism (MSAP) markers. Indices of (epi-)genetic diversity, (epi-)genetic distance, gene flow, genotype frequency, cluster analysis, PCA analysis and AMOVA analysis generated from MSAP, AFLP and SSAP markers had the same trend. We found a high level of correlation in the artificial populations between MSAP, SSAP and AFLP markers by the Mantel test (r > 0.8). This is incongruent with previous findings showing that there is virtually no correlation between DNA methylation polymorphism and classical genetic variation; the high level of genetic polymorphism could be a result of epigenetic regulation. We compared our results with data from natural populations. The population diversity of the artificial populations was lower. However, different from what was found using AFLP and SSAP, based on MSAP results the methylation polymorphism of the artificial populations was not significantly reduced. This leads us to suggest that the DNA methylation pattern change in H. brevisubulatum populations is not only related to DNA sequence variation, but is also regulated by other controlling systems.