Development and application of multiple internal reference (housekeeper) gene assays for accurate normalisation of canine gene expression studies

Measurement of mRNA expression by real-time RT-PCR (QRT-PCR) has proven to be an important and powerful tool for the investigation of the pathogenesis of inflammatory and immune-mediated diseases in many species. This methodology has proven particularly valuable in the dog, a species for which there are currently few specific antibodies for measurement of relevant proteins. Internal control (housekeeper) mRNAs are widely used for normalisation of QRT-PCR results. The validation and use of multiple internal control mRNAs for increased accuracy of normalisation has been described for humans and rodents. The aims of this study were to develop QRT-PCR assays for 11 potential internal control mRNAs in the dog (ACTB, B(2)M, G3PDH, HMBS, HPRT1, RPL13A, RPL32, RPS18, SDHA, TBP and YWAZ) and validate their use with bone marrow, colon, duodenum, heart, kidney, liver, lung, lymph node, skeletal muscle, pancreas, spleen and stomach from seven dogs. Endoscopic biopsies of the superficial duodenal mucosa were also obtained from nine dogs suffering from chronic gastro-oesophageal disease. The most stably expressed genes varied in the tissues examined. RPL13A and RPL32 (both components of the 60S ribosomal subunit) were the most stably expressed genes in the majority of the tissues examined, whereas ACTB and B(2)M were the least stable. Distinct internal control genes were shown to be most appropriate for use in full-thickness versus superficial mucosal biopsies of the duodenum. The results of this study indicate that there are no universal control genes for gene expression studies in canine tissues. It is important to use multiple internal control genes based upon a survey of potential control genes applied to representative samples from different disease groups, culture conditions and/or time points in an experimental study.     

Haemoplasma infection is not a common cause of canine immune-mediated haemolytic anaemia in the UK

Objective : The aim of this study was to investigate whether the two canine haemoplasma species, Mycoplasma haemocanis and “Candidatus Mycoplasma haematoparvum,” are commonly associated with immune-mediated haemolytic anaemia (IMHA) in UK dogs. Methods : Three groups of dogs were recruited to the study: anaemic dogs with primary IMHA (n=37); anaemic dogs not meeting the inclusion criteria for primary IMHA (n=77) and non-anaemic dogs (n=113). DNA was extracted from 100 μl of blood and subjected to real-time quantitative polymerase chain reaction (qPCR) assays for both species of Mycoplasma. Each assay incorporated co-amplification of canine glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as an endogenous internal control. Results : Canine GAPDH was successfully amplified by qPCR from all 227 canine blood samples but none contained M. haemocanis or “Candidatus M. haematoparvum” DNA. Clinical Significance : Haemoplasma infection is uncommon in dogs in the UK and no evidence was found that these organisms act as triggers for IMHA.     

Array-based comparative genomic hybridization-guided identification of reference genes for normalization of real-time quantitative polymerase chain reaction assay data for lymphomas, histiocytic sarcomas, and osteosarcomas of dogs

Objective-To identify suitable reference genes for normalization of real-time quantitative PCR (RT-qPCR) assay data for common tumors of dogs. Sample-Malignant lymph node (n = 8), appendicular osteosarcoma (9), and histiocytic sarcoma (12) samples and control samples of various nonneoplastic canine tissues. Procedures-Array-based comparative genomic hybridization (aCGH) data were used to guide selection of 9 candidate reference genes. Expression stability of candidate reference genes and 4 commonly used reference genes was determined for tumor samples with RT-qPCR assays and 3 software programs. Results-LOC611555 was the candidate reference gene with the highest expression stability among the 3 tumor types. Of the commonly used reference genes, expression stability of HPRT was high in histiocytic sarcoma samples, and expression stability of Ubi and RPL32 was high in osteosarcoma samples. Some of the candidate reference genes had higher expression stability than did the commonly used reference genes. Conclusions and Clinical Relevance-Data for constitutively expressed genes with high expression stability are required for normalization of RT-qPCR assay results. Without such data, accurate quantification of gene expression in tumor tissue samples is difficult. Results of the present study indicated LOC611555 may be a useful RT-qPCR assay reference gene for multiple tissue types. Some commonly used reference genes may be suitable for normalization of gene expression data for tumors of dogs, such as lymphomas, osteosarcomas, or histiocytic sarcomas.     

草地早熟禾荧光定量PCR分析中内参基因的筛选

为筛选出草地早熟禾实时荧光定量中的最适内参基因,利用实时荧光定量PCR技术,分析检测6个传统内参基因ACT、GAPDH、UBQ、EF-1α、18s rRNA和β-tublin在草地早熟禾不同组织器官、叶片不同发育期、非生物胁迫和不同激素诱导下mRNA的表达差异情况。利用geNorm、NormFinder和BestKeeper软件综合评价6个候选内参基因的表达稳定性。结果表明,在不同组织、叶片不同发育期、激素诱导和非生物胁迫下,候选内参基因的表达稳定性存在差异。GAPDH在草地早熟禾不同组织器官中表达最为稳定;EF-1α在非生物胁迫下表达最为稳定;不同激素下首选β-tublin;在叶片不同发育期ACT表达最为稳定。综上所述,通过筛选出不同条件下适宜的内参基因不仅有助于提高草地早熟禾基因表达分析的准确性,也为早熟禾属植物其他内参基因的开发提供了理论参考。     

A validation of 10 feline reference genes for gene expression measurements in snap-frozen tissues

For a proper determination of relative mRNA expression levels with real-time quantitative PCR (Q-PCR) internal standards, such as the expression of reference genes, are of utmost importance. For cats, in contrast to dogs, no validation of reference genes has been published. Our goal was to evaluate frequently used reference genes for the analysis of relative mRNA levels from feline tissues in a SYBR Green-based Q-PCR protocol. First, primers were optimized on mRNA-derived cDNA from liver and kidney tissues of randomly chosen (healthy and diseased) cats. Then, the expression variation and stability of each reference gene within a specific tissue was determined. Dental roots and crowns, heart (left ventricle), renal, liver, lung, and mammary gland tissues from 3 to 11 cats of different breeds, sexes, ages, and disease status were included in this study. Averaging relative stabilities over these six tissues revealed the usefulness of each tested gene as reference gene. In order to compensate for the expression variation of a reference gene within a specific tissue, as much as six reference genes (e.g. RPL17, RPL30, RPS7, YWHAZ, and HPRT) were required to obtain highly reliable data in cat tissues. The optimal set of reference genes depended on the tissue analyzed and should, ideally, be selected and evaluated at the start of each experimental condition. A comparison with a similar evaluation in dogs revealed three issues: (i) most ribosomal genes are suitable in both species; (ii) good non-ribosomal reference genes differ; (iii) more feline than canine reference genes are required for proper analysis.     

鹿茸组织中内参基因的筛选和验证

为筛选在不同生长时期鹿茸组织中稳定表达的内参基因,试验以不同生长时期(分别为脱盘后10、20、40和60 d)的鹿茸组织为材料,采用实时荧光定量PCR(qRT-PCR)方法分析甘油醛-3-磷酸脱氢酶(GAPDH)、β2-微球蛋白(B2M)、还原型辅酶Ⅰ(NADH)、60S 核糖体蛋白L40(RPL40)、谷胱甘肽还原酶7(GPx)和β肌动蛋白(ACTB)6个看家基因的表达情况,并运用 geNorm和NormFinder 两个程序综合分析6个看家基因的表达稳定性.结果显示,GAPDH、ACTB、RPL40表达稳定性较好,可用作鹿茸基因表达研究的内参基因,而NADH和GPx的稳定性最差,不适合作内参基因.通过对鹿茸生长相关基因(ANXA5、HSP27、PRD2、CRABP1、LGALS1)表达分析,进一步验证了上述结果,并且发现这5种基因均在脱盘后10 d的鹿茸组织中高表达.该研究结果为鹿茸快速生长及骨化相关基因的研究奠定了一定基础.     

Stability of expression of reference genes in porcine peripheral blood mononuclear and dendritic cells

Real-time quantitative PCR (RT-qPCR) is a critical tool used to evaluate changes in gene expression. The precision of this tool is reliant upon the selection of reference genes whose expression remains unaltered in culture conditions and following stimulation. Stably expressed reference genes are used to normalize data so observed changes in expression are not due to artifacts but rather reflect physiological changes. In this study, we examined the expression stability of the porcine genes glyceraldehyde 3-phosphate dehydrogenase (GAPDH), succinate dehydrogenase complex subunit A (SDHA), eukaryotic elongation factor 1 gamma-like protein (eEF1), ribosomal protein L19 (RPL19), beta-actin (ACTB) and ATP synthase mitochondrial F0 complex (ATP5G1) in peripheral blood mononuclear cells (PBMCs), monocytes, monocyte-derived dendritic cells (MoDCs), blood isolated dendritic cells (BDCs) and T cells with or without stimulation with lipolysaccharide (LPS). An M value was used as a measure of gene stability as determined using geNORM software. Recommendations for the use of reference genes include using GAPDH and B-actin in PBMCs: RPL19 and SDHA in T cells; RPL19 and B-actin in monocytes; RPL-19 and SDHA in BDCs: and RPL-19 and ATP5GA in MoDCs.     

Screening of the Reference Genes for the Study of Peripheral Blood Mononuclear Cells by Quantitative Real-time PCR in Min Pigs

Min pig is a local pig breed in Northeast China. It has been well-adapted to the local cold weather,but few genes related to its environmental adaptation have been studied. For studies about environmental adaptation of Min pig on molecular level,it is important to have proper reference genes for quantification of gene expression by quantitative Real-time PCR. In this study,12 reference genes (B2M,ACTB,RPL11,RPL4,YWHAZ,GAPDH,HPRT1,SDHA,HMBS,IDH3B,TUBB2B and TBP1) were evaluated for their potential as the reference gene in Min pig peripheral blood mononuclear cells under different temperatures. Blood samples were collected from 3 Min pigs which were under -25,5,10 and 30℃,respectively. Mononuclear cells were separated using density gradient centrifugation. Statistical algorithms including geNorm,Normfinder and BestKeeper were employed to assess the stabilities of these genes. Analysis of geNorm and Normfinder revealed that all these 12 genes were highly stable. However,ACTB,GAPDH,SDHA,HPRT1,TBP1 and YWHAZ genes (SD<1) were found to be more stable than other six genes (SD>1),of which TBP1 was the most stable one using BestKeeper program. To summarize,ACTB,GAPDH,SDHA,HPRT1, TBP1 and YWHAZ genes were suitable to be the reference genes,with TBP1 was the best one.     

民猪外周血单核细胞实时荧光定量PCR内参基因的筛选

民猪是能够适应东北地区寒冷环境的地方猪种,但目前对其环境适应性相关基因的研究较少,也没有确定适合此研究所需的实时荧光定量PCR的内参基因。因此,本试验通过研究常用的12个内参基因（B2M、ACTB、RPL11、RPL4、YWHAZ、GAPDH、HPRT1、SDHA、HMBS、IDH3B、TUBB2B和TBP1）在不同环境温度下民猪外周血单核细胞中的表达稳定性,旨在确定合适的内参基因进行相关研究。分别在-25、5、10和30℃采集3头民猪耳静脉血分离出单核细胞,利用geNorm、NormFinder、BestKeeper 3种软件分析12个候选内参基因的Ct值,筛选出表达稳定的基因作为内参基因。经geNorm和NormFinder计算获得各候选基因的M值发现,12个候选基因的表达均相对稳定,而BestKeeper的分析则显示ACTB、GAPDH、SDHA、HPRT1、TBP1、YWHAZ基因的SD值均<1,可用作本研究条件下的内参基因,而另外6个基因SD值则>1,不符合作为内参基因的标准。综合3种分析的结果,在本研究条件下,TBP1基因的稳定性最高,ACTB、GAPDH、SDHA、HPRT1和YWHAZ基因也符合作为内参基因的标准,都可研究在不同环境温度下民猪外周血单核细胞中基因表达时作为内参基因。     

Widespread expression of SAA and Hp RNA in bovine tissues after evaluation of suitable reference genes

The serum amyloid A (SAA) and haptoglobin (Hp) are the most prominent acute phase proteins (APPs) in cow. Liver mainly produces APPs, but extra hepatic expression has also been demonstrated in some tissues. The major aim of the present study was to assess the constitutive SAA and Hp mRNA expression by quantitative PCR (qPCR) in a wide panel of 33 bovine tissues, including gastrointestinal tract, respiratory system, urogenital system, mammary gland, hematopoietic system, central nervous system, eye, thyroid and heart. Normalization of gene expression in different samples requires reference genes, which are stably expressed. Therefore, seven reference genes were investigated (ACTB, GAPDH, HMBS, SDHA, YWHAZ, SF3A1, EEF1A2) and three genes, namely SF3A1, HMBS and ACTB, were selected after assessing their stability with geNorm? and NormFinder^© softwares.The qPCR analysis confirmed liver as the principal source of SAA and Hp, but also identified both APPs’ mRNA in almost all tissues.The highest expression rate of SAA was found in thyroid, followed by pancreas and submandibulary gland. Hp mRNA expression was detected at high concentration in pancreas and submandibulary gland.The present data indicated a widespread expression of SAA and Hp also in non pathological conditions, thus envisaging a possible role as immunomodulatory and protective molecules. To understand where SAA and Hp come from is the prerequisite to their utilization as Acute Phase Reaction biomarkers.     

Validation of candidate bovine reference genes for use with real-time PCR

Accurate quantification with real-time PCR requires the use of stable endogenous controls. Recently, there has been much debate concerning the stability of commonly used reference or housekeeping genes. To address this concern, a number of statistical approaches have been designed to analyse data and assist in determining the most appropriate reference genes for experimental comparisons. In this study, three programs, BestKeeper, Norm Finder, and geNorm were used to assess four candidate reference genes: 18S rRNA, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), acidic ribosomal protein large (RPLP0) and beta-actin, for use in expression profiling of individuals from divergent cattle genotypes subject to parasitic challenge with the cattle tick Boophilus microplus. Results demonstrated beta-actin and GAPDH were the most suitable reference genes in blood and could be used either individually or combined as an index to normalise data. RPLP0 was identified as the least stable gene, while 18S rRNA was omitted as being too highly expressed. As the recommendations on the most suitable reference genes varied between the programs, it is recommended that more than one should be utilised, to ensure the most robust experimental tools are selected.     

角蛋白26基因在超细型和细型细毛羊皮肤组织中的表达差异

采用超细型和细型细毛羊皮肤组织为试验材料,以18S rRNA、β-actin、GAPDH等基因为内参,角蛋白26(keratin 26,KRT26)为目的基因,建立了基于SYBR Green Ⅰ染料技术的Real-time PCR检测体系,并分析KRT26基因在不同细度绵羊皮肤组织中的表达差异。结果表明,以cDNA为模板建立的标准曲线循环阈值(Ct)与标准cDNA模板在一定浓度范围内呈良好的线性关系,当以18S rRNA、β-actin、GAPDH作为内参基因时,KRT26基因在超细型细毛羊皮肤组织中的表达水平是细型细毛羊皮肤组织中的1.5倍。初步确定KRT26基因与毛细度具有相关性,这将为进一步研究分子育种和绵羊毛纤维细度性状的改良提供依据。     

Development and use of real-time PCR to detect and quantify Mycoplasma haemocanis and “Candidatus Mycoplasma haematoparvum” in dogs

Two canine haemoplasma species have been recognised to date; Mycoplasma haemocanis (Mhc), which has been associated with anaemia in splenectomised or immunocompromised dogs, and “Candidatus Mycoplasma haematoparvum” (CMhp), recently described in an anaemic splenectomised dog undergoing chemotherapy. The study aim was to develop quantitative real-time PCR assays (qPCRs) incorporating an endogenous internal control to detect Mhc and CMhp and to apply these assays to DNA samples extracted from canine blood collected in Northern Tanzania (n = 100) and from dogs presented to a Trinidadian veterinary hospital (n = 185).QPCRs specific for Mhc and CMhp were designed using 16S rRNA gene sequence data, and each was duplexed with an assay specific for canine glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The assays detected ≤10 copies of a sequence-specific haemoplasma plasmid per reaction and neither assay showed cross-reactivity with 10⁶ copies of the sequence-specific plasmid from the non-target canine haemoplasma species.Nineteen of the 100 Tanzanian samples (19%) were positive for Mhc alone and one (1%) was dually infected. One Trinidadian sample was negative for canine GAPDH DNA and was excluded from the study. Of the 184 remaining Trinidadian samples, nine (4.9%) were positive for Mhc alone, five (2.7%) for CMhp alone, and two (1.1%) dually infected.This is the first report of canine haemoplasma qPCR assays that use an internal control to confirm the presence of amplifiable sample DNA, and their application to prevalence studies. Mhc was the most commonly detected canine haemoplasma species.     

Quantification of MDR-1 gene expression in canine tissues by real-time reverse transcription quantitative polymerase chain reaction

MDR-1 gene product mediated multidrug resistance is thought to play a major role in the outcome of chemotherapy in some canine tumors, especially malignant lymphoma. In the present study, MDR-1 RNA expression in normal lymph node and liver tissue as well as in tumor biopsies from 23 dogs with lymphomas and two dogs with liver tumors was measured by real-time RT-quantitative PCR. MDR-1 gene expression was detected in all samples analyzed. Comparably high MDR-1 RNA levels were measured in all normal liver tissues, one of the lymphomas and a cholangiocarcinoma. MDR-1 expression levels in canine lymphomas were found to vary over a wide range with most tumors expressing relative low levels. Interestingly, gastrointestinal lymphomas expressed higher MDR-1 RNA levels than multicentric lymphomas (p = 0.03). In conclusion, real-time RT-quantitative PCR appears to be a suitable method for sensitive and quantitative determination of MDR-1 gene expression in canine normal and neoplastic tissues.