Evaluation of the sustainability of contrasted pig farming systems: the procedure, the evaluated systems and the evaluation tools.

Although a few studies consider the sustainability of animal farming systems along the three classical main pillars (economy, environment and society), most studies on pig farming systems address only one of these pillars. The present paper is the introduction to a series of companion papers presenting the results of a study undertaken within the EU-supported project Q-PorkChains, aiming at building a comprehensive tool for the evaluation of pig farming systems, which is robust to accommodate the large variability of systems existing in Europe. The tool is mostly based on questions to farmers and comprises a total of 37 dimensions distributed along eight themes: Animal Welfare, Animal Health, Breeding Programmes, Environmental Sustainability, Meat Safety, Market Conformity, Economy and Working Conditions. The paper describes the procedure that was used for building the tool, using it on 15 contrasted pig farming systems and analysing the results. The evaluated systems are briefly described and a short overview of the dimensions is provided. Detailed descriptions of the theme-wise tools and results, as well as the results of an integrated evaluation, are available in the companion papers.

Investigation on association and expression of ESR2 as a candidate gene for boar sperm quality and fertility.

ESR2 is involved in oestrogen-related apoptosis in cell cycle spermatogenesis but their effects have not yet confirmed in pig. Therefore, this study was aimed to investigate the association of ESR2 polymorphism with sperm quality and boar fertility traits and to analyse the ESR2 mRNA and protein expressions in boar reproductive tissues. DNA samples from 203 Pietrain (PI) and 100 Pietrain × Hampshire (PIHA) pigs with records of sperm quality [sperm concentration (SCON), motility (MOT), semen volume (VOL), plasma droplet rate (PDR) and abnormal spermatozoa rate (ASR)] and fertility [non-return rate (NRR) and number of piglet born alive (NBA)] traits were available. A SNP in coding region of ESR2 g.35547A>G in exon 5 was associated with MOT and PDR in the PI and with SCON, VOL, MOT and PDR in PIHA population. For mRNA and protein expression study, a total of six boars were divided into two groups with group I (G-I) and group II (G-II) where G-I characterized for relatively a better sperm quality according to the mean of two groups. mRNA expression was higher in brain and testis than that in all parts of epididymis. Both qRT-PCR and western blot analysis revealed that the ESR2 gene expression and protein expression were significantly higher in testis collected from G-II compared with that of G-I boars. Moreover, ESR2 protein localization in germ cell, Leydig and Sertoli cells, epithelial cells and spermatozoa was remarkable, which indicated the important role of ESR2 in spermatogenesis process. These results might shed new light on the roles of ESR2 in spermatogenesis as candidate for boar fertility, but still the lack of association across populations should be considered.

Investigation into association and expression of PLCz and COX-2 as candidate genes for boar sperm quality and fertility.

Phospholipase C zeta (PLCz) and cyclooxygenase isoenzyme type 2 (COX-2) are important in spermatogenesis, but their effect has not yet confirmed in pigs. Therefore, this study was aimed to analyse their association with sperm quality and fertility and to identify the mRNA and protein expression in boars reproductive tissues. DNA samples from 231 Pietrain (PI) and 109 Pietrain × Hampshire (PIHA) pigs with records of sperm quality [sperm concentration (SCON), motility, semen volume, plasma droplet and abnormal spermatozoa rate] and fertility (non-return rate and number of piglet born alive) traits were available. A SNP in non-coding region of PLCz g.158 A > C was associated with SCON (p < 0.05) in PIHA population while the polymorphism of COX-2 g.68 G > A in 3' UTR was not associated with any traits. For mRNA and protein expression study, a total of six boars were divided into two groups with G-I and G-II, where G-I was characterized for relatively better sperm quality. Both genes expressed higher in reproductive tissues compared with non-reproductive tissues. Phospholipase C zeta mRNA expressed higher in testis (p < 0.01), all parts of epididymis and spermatozoa from G-I, while COX-2 expressed higher in testis (p < 0.05), head and body of epididymis (p < 0.01), and spermatozoa from G-II boar. Both proteins were localized in Leydig cells and spermatozoa. These results might shed light on roles of these genes in spermatogenesis as candidate for boar sperm quality and fertility, but still the lack of association across populations should be considered.

Bovine blastocysts with developmental competence to term share similar expression of developmentally important genes although derived from different culture environments.

This study was conducted to investigate the gene expression profile of in vivo-derived bovine embryo biopsies based on pregnancy outcomes after transferring to recipients. For this, biopsies of 30-40% embryos were taken from grade I blastocysts (International Embryo Transfer Society Manual) and the remaining 60-70% of the intact embryos were transferred to recipients. Frozen biopsies were pooled into three distinct groups based on the pregnancy outcome after transferring the corresponding parts, namely those resulting in no pregnancy (NP), pregnancy loss (PL), and calf delivery (CD). Array analysis revealed a total of 41 and 43 genes to be differentially expressed between biopsies derived from blastocysts resulting in NP versus CD and PL versus CD respectively. Genes regulating placental development and embryo maternal interaction (PLAC8) were found to be upregulated in embryo biopsies that ended up with CD. Embryo biopsies that failed to induce pregnancy were enriched with mitochondrial transcripts (Fl405) and stress-related genes (HSPD1). Overall, gene expression profiles of blastocysts resulting in NP and CD shared similar expression profiles with respect to genes playing significant roles in preimplantation development of embryo. Finally, comparing the transcript signatures of in vivo- and in vitro-derived embryos with developmental competence to term revealed a similarity in the relative abundance of 18 genes. Therefore, we were able to present a genetic signature associated with term developmental competence independent of the environmental origin of the transferred blastocysts.

Association of PPARGC1A and CAPNS1 gene polymorphisms and expression with meat quality traits in pigs.

This study aimed to investigate the genes PPARGC1A (peroxisome proliferator-activated receptor gamma-coactivator 1A) and CAPNS1 (calpain small subunit 1) as candidate genes affecting meat quality traits in pigs. Four polymorphisms were identified in PPARCG1A and three in CAPNS1. The PPARGC1A polymorphism c.1288T>A was associated with pH and cooking loss in a F2 Duroc×Pietrain experimental cross (DuPi, n=313) and with pH values in Italian Large White (ILW, n=380) and Italian Landrace (ILA, n=158) populations (P<0.05). The CAPNS1 polymorphism c.429A>C was associated with pH and conductivity in DuPi and with meat color in ILA (P<0.05). PPARGC1A mRNA expression associated with drip loss (P<0.01) and the same tendency was found for CAPNS1 (P=0.06). The promoter methylation profiling suggested that methylation is not involved in CAPNS1 expression regulation. In conclusion, porcine PPARGC1A and CAPNS1 genes may affect meat quality traits, with breed-specific differences, and they could be used as markers for the improvement of meat quality in pigs.

Polymorphism and expression of the porcine Tenascin C gene associated with meat and carcass quality.

The research aimed to screen for polymorphism, expression of Tenascin C (TNC) and association with meat and carcass quality traits. Three single nucleotide polymorphisms were detected. In a Duroc×Pietrain F2 cross (DuPi) population, g.44488C>T was associated with meat color and ham weight; g.68794A>G was associated with pH at 24h post mortem in ham (pH24(H)) and muscle area but g.68841C>T was not statistically associated. Genotyping in a commercial Pietrain (Pi) population showed that g.44488C>T was associated with pH24(H), whereas g.68794A>G was associated with conductivity at 45 min post mortem in loin and backfat thickness. Diplotypes showed significant effects on pH24(H) in both populations. The expression was associated with pH at 45 min post mortem in loin and cooking loss. TNC was significantly higher in animals with higher muscle pH. Linkage analysis revealed four trans-regulated eQTL on four autosomes. These results suggest that TNC could be a potential candidate gene for meat quality traits in pigs.

Investigation on interferon alpha-inducible protein 6 (IFI6) gene as a candidate for meat and carcass quality in pig.

The aim of this research was to screen for polymorphism and to perform an association study of IFI6 with meat and carcass quality traits. A SNP (g.370A>G) was detected which was associated (P<0.05) with meat colour, pH 24h post mortem (p.m.) in ham, conductivity 45 min p.m. in loin and conductivity 24 h p.m. in ham, drip loss and carcass length in Duroc x Pietrain and with meat colour, muscle area and ham percentage in the Pietrain population. Highest expression of IFI6 mRNA was detected in skeletal muscle (longissimus dorsi) by qRT-PCR comparing different tissues. Both qRT-PCR and western blot revealed that the IFI6 gene and protein expressions were significantly (P<0.05) higher in skeletal muscle with low drip loss compared to that of high drip loss. IFI6 protein was localized in the myocytes membrane. Results suggested that IFI6 might play roles in meat and carcass quality and is a potential positional, physiological and functional candidate gene for improving meat quality traits in pigs.

Mapping quantitative trait loci for innate immune response in the pig.

The aim of the present study was to detect quantitative trait loci (QTL) for the serum levels of cytokines and Toll-like receptors as traits related to innate immunity in pig. For this purpose, serum concentration of interleukin 2 (IL2), interleukin 10 (IL10), interferon-gamma (IFNG), Toll-like receptor 2 (TLR2) and Toll-like receptor 9 (TLR9) were measured in blood samples obtained from F(2) piglets (n = 334) of a Duroc × Piétrain resource population (DUPI) after Mycoplasma hypopneumoniae (Mh), tetanus toxoid (TT) and Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) vaccination at 6, 9 and 15 weeks of age. Animals were genotyped at 82 genetic markers covering all autosomes. QTL analysis was performed under the line cross F(2) model using QTL Express and 33 single QTL were detected on almost all porcine autosomes. Among the single QTL, eight, twelve and thirteen QTL were identified for innate immune traits in response to Mh, TT and PRRSV vaccine, respectively. Besides single QTL, six QTL were identified by a two-QTL model, of which two for TLR9_TT were in coupling phase and one for IL10_PRRSV was in repulsion phase. All QTL were significant at 5% chromosome-wide level including one and seven at 5% genome- and 1% chromosome-wide level significance. All innate immune traits are influenced by multiple chromosomal regions implying multiple gene action. Some of the identified QTL coincided with previously reported QTL for immune response and disease resistance, and the newly identified QTL are potentially involved in the immune function. The immune traits were also influenced by environmental factors like year of birth, age, parity and litter size. The results of this work shed new light on the genetic background of innate immune response and these findings will be helpful to identify candidate genes in these QTL regions related to immune competence and disease resistance in pigs.

Association of ZYX polymorphisms with carcass and meat quality traits in commercial pigs.

Zyxin (ZYX) is one of the proteins in focal adhesions along the actin fibers playing a role in actin organization and signal transduction. By radiation hybrid and genetic mapping we assigned ZYX to porcine chromosome 18 in the area of quantitative traits loci for carcass and meat quality and muscle fiber traits and hence considered ZYX a functional positional candidate gene. Analysis of a newly detected SNPs (c.+279 C>T, c.+399 A>G, c.+522 A>G) in pigs from different commercial breeds (Pietrain [Pi], German Landrace [LR], German Large White x German Landrace [F1] and PiF1) revealed a significant association with carcass traits (including: side- and backfat thickness, loin weight and carcass lean content) and meat quality traits (including: pH, color and drip loss). However, the lack of consistent association across all pig populations in this study indicates that the association of the SNPs may be depending on causal mutations in linkage disequilibrium and/or interactions with other loci.

Expression quantitative trait loci analysis of genes in porcine muscle by quantitative real-time RT-PCR compared to microarray data.

Genetic analysis of transcriptional profiling is a promising approach for identifying biological pathways and dissecting the genetics of complex traits. Here, we report on expression quantitative trait loci (eQTL) that were estimated from the quantitative real-time RT-PCR data of 276 F(2) animals and compared with eQTL identified using 74 microarrays. In total, 13 genes were selected that showed trait-dependent expression in microarray experiments and exhibited 21 eQTL. Real-time RT-PCR and microarray data revealed seven cis eQTL in total, of which one was only detected by real-time RT-PCR, one was only detected by microarray analysis, three were consistently found in overlapping intervals and two were in neighbouring intervals on the same chromosome; whereas no trans eQTL was confirmed. We demonstrate that cis regulation is a stable characteristic of individual transcripts. Consequently, a global microarray eQTL analysis of a limited number of samples can be used for exploring functional and regulatory gene networks and scanning for cis eQTL, whereas the subsequent analysis of a subset of likely cis-regulated genes by real-time RT-PCR in a larger number of samples is relevant to narrow down a QTL region by targeting these positional candidate genes. In fact, when modelling SNPs of six genes as fixed effects in the eQTL analysis, eQTL peaks were shifted downwards, experimentally confirming the impact of the respective polymorphic genes, although these SNPs were not located in the regulatory sequence and these shifts occur as a result of linkage disequilibrium in the F(2) population.

Suppression of the transcription factor MSX1 gene delays bovine preimplantation embryo development in vitro.

This study was conducted to investigate the effect of suppressing transcription factor gene MSX1 on the development of in vitro produced bovine oocytes and embryos, and identify its potential target genes regulated by this gene. Injection of long double-stranded RNA (LdsRNA) and small interfering RNA (siRNA) at germinal vesicle stage oocyte reduced MSX1 mRNA expression by 73 and 37% respectively at metaphase II stage compared with non-injected controls. Similarly, injection of the same anti-sense oligomers at zygote stage reduced MSX1 mRNA expression by 52 and 33% at 8-cell stage compared with non-injected controls. Protein expression was also reduced in LdsRNA- and siRNA-injected groups compared with non-injected controls at both stages. Blastocysts rates were 33, 28, 20 and 18% in non-injected control, scrambled RNA (scRNA), LdsRNA- and siRNA-injected groups respectively. Cleavage rates were also significantly reduced in Smartpool siRNA (SpsiRNA)-injected group (53.76%) compared with scRNA-injected group (57.76%) and non-injected control group (61%). Large-scale gene expression analysis showed that 135 genes were differentially regulated in SpsiRNA-injected group compared with non-injected controls, of which 54 and 81 were down- and up-regulated respectively due to suppression of MSX1. Additionally, sequence homology mapping and gene enrichment analysis with known human pathway information identified several functional modules that were affected due to suppression of MSX1. In conclusion, suppression of MSX1 affects oocyte maturation, embryo cleavage rate and the expression of several genes, suggesting its potential role in the development of bovine preimplantation embryos.

Effect of embryo density on in vitro developmental characteristics of bovine preimplantative embryos with respect to micro and macroenvironments.

To overcome developmental problems as a consequence of single embryo culture, the Well of the Well (WOW) culture system has been developed. In this study, we aimed to examine the effect of embryo densities with respect to both microenvironment and macroenvironment on developmental rates and embryo quality to get a deeper insight into developmentally important mechanisms. WOW diameter and depth significantly affected developmental rates (p < 0.05). WOWs with diameter of 500 µm reached significantly higher blastocyst rates (32.5 vs 21.1% vs 20.3%) compared to embryos cultured in WOWs of 300 µm diameter or plain cultured controls. Embryos cultured in WOWs with 700 µm depth reached significant higher developmental rates compared with embryos cultured in WOWs of 300 µm depth and control embryos (30.6 vs 22.6% vs 20.3%). Correlation of the embryo per WOW volume with developmental rates was higher (r(2) = 0.92, p = 0.0004) than correlation of WOW diameter or WOW depth with developmental rates. However, the embryo per WOW volume did not affect differential cell counts. An embryo per culture dish volume of 1 : 30 µl was identified to be optimal when the embryo per WOW volume was 1 : 0.27 µl increasing developmental rates up to the level of mass embryo production. Giving the opportunity to track each embryo over the complete culture period while keeping high developmental rates with normal mitotic dynamics, the results of this work will provide benefit for the single culture of embryos in human assisted reproduction, mammalian embryos with high economic interest as well as for scientific purpose.

Transcriptional analysis of buffalo (Bubalus bubalis) oocytes during in vitro maturation using bovine cDNA microarray.

The need for improving in vitro production of buffalo embryos necessitates a better understanding of the molecular mechanisms regulating early development including oocyte maturation. Here, we used bovine cDNA microarray platform to investigate mRNA abundance of buffalo oocytes before and after in vitro maturation. For this, a total of six pools each contains 50 immature or in vitro matured buffalo oocytes were used for mRNA isolation and subsequent cDNA synthesis. The BlueChip bovine cDNA microarray (with approximately 2000 clones) was used to analyse gene expression profiles between immature and matured oocytes. Statistical analysis of microarray data revealed a total of 104 transcripts to be differentially expressed between the two oocyte groups. Among these, transcription factors (ZFP91), M-phase mitotic cell cycle (MPHOSPH9), growth factor (BMP15) and DNA binding (HMGN2) were found to be up-regulated in immature oocytes. Similarly, matured oocytes were found to be enriched with genes involved in cytoskeleton (ACTB), hydrogen ion transporting (ATP6V1C2) and structural constituent of ribosome (RPS27A). Quantitative real-time polymerase chain reaction validated the expression profile of some selected transcripts during array analysis. In conclusion, to our knowledge, this is the first large-scale expression study to identify candidate genes differentially abundant and with potential role during buffalo oocyte maturation.

Association of parathyroid hormone-like hormone (PTHLH) and its receptor (PTHR1) with the number of functional and inverted teats in pigs.

Parathyroid hormone-like hormone gene (PTHLH) and its receptor, parathyroid hormone/ parathyroid hormone-like hormone receptor 1 (PTHR1), play a role in epithelial mesenchymal interactions during growth and differentiation of different tissues and anatomic structures, including teats. Therefore, PTHLH and PTHR1 were evaluated as functional candidate genes for their effects on number and shape of teats in pigs. In particular, focus was on the occurrence and number of inverted teats, the most frequent and economically relevant teat developmental defect in pigs. For this purpose, association and linkage of the PTHLH gene and the PTHR1 gene with inverted teat defect and the total number of teats and inverted teats were studied in an experimental Duroc and Berlin Miniature pig (DUMI) population. Polymorphism C1819T of PTHR1 was significantly associated with inverted teat phenotype (p = 0.014), total number of teats (p = 0.047) and was close to significance with the number of inverted teats (p = 0.078). Polymorphism C375T of PTHLH was close to significance with the inverted teat phenotype (p = 0.122) and showed no significant association with the total number of teats (p = 0.621) and the number of inverted teats (p = 0.256) in the DUMI population. Association analyses were also performed for combined effects of PTHLH and PTHR1 in order to address potential interaction, however, revealed no indication of effects of interaction. The function, position and the association shown here promote PTHR1 as a candidate gene for number of teats and in particular for affection by and number of inverted teats.

Porcine muscle sensory attributes associate with major changes in gene networks involving CAPZB, ANKRD1, and CTBP2.

Principal component analysis of traits related to carcass and meat properties were combined with microarray expression data for the identification of functional networks of genes and biological processes taking place during the conversion of muscle to meat. Principal components (PCs) with high loadings of meat quality traits were derived from phenotypic data of 572 animals of a porcine crossbreed population. Microarray data of 74 M. longissimus dorsi samples were correlated with PC datasets. Lists of significantly correlated genes were analyzed for enrichment of functional annotation groups as defined in the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases as well as the Ingenuity Pathways Analysis library. Ubiquitination, phosphorylation, mitochondrion dysfunction, actin, integrin, platelet-derived growth factor, epidermal growth factor, vascular endothelial growth factor, and Ca signaling pathways are correlated with meat quality. Among the significantly trait-associated genes, CAPZB, ANKRD1, and CTBP2 are promoted as candidate genes for meat quality that provide a link between the highlighted pathways. Knowledge of the relevant biological processes and the differential expression of members of the pathway will provide tools that are predictive for traits related to meat quality and that may also be diagnostic for many muscle defects or damages including muscle atrophy, dystrophy, and hypoxia.

Evidence for association of lymphoid enhancer-binding factor-1 (LEF1) with the number of functional and inverted teats in pigs.

The lymphoid enhancer-binding factor-1 (LEF1) belongs to a family of regulatory proteins that share homology with the high mobility group protein-1 (HMG1). The LEF1 gene is a mediator in the canonical Wnt-signalling pathway required for morphogenesis of early mammary gland during embryogenesis. Here we describe the molecular characterisation of the porcine LEF1 gene and its association with number of teats and inverted teats in experimental and commercial populations. The 2357-bp cDNA sequence contains an 1197-bp open reading frame encoding a protein of 398 amino acids. The porcine LEF1 protein shares high identity with LEF1 in other mammalian species. The LEF1 gene contains 12 exons and maps to pig chromosome 8 (SSC8). We identified two single nucleotide polymorphisms (SNPs), a T1351C transition and an A1666C transversion, in the 3' end of LEF1. Associations of the SNP A1666C with presence of inverted teats (P

Physiological interactions between the endocrine and immune systems shown in gene analysis in pigs.

A number of observations support the concept of important physiological interactions between the endocrine and immune systems. It could be confirmed that hormones secreted by the neuroendocrine system play an important role in communication and regulation of the cells of the immune system. Among protein hormones, this has been most clearly documented for prolactin (PRL), growth hormone (GH), and insulin-like growth factor 1 (IGF-1). A number of traits of the immune response in a Duroc x Berlin Miniature pig family (DUMI) were examined. The haemolytic complement activity in the classical complement pathway (CH50) and the alternative pathway (AH50)was examined at eight different time points in pigs that were vaccinated with different vaccines. Single nucleotide polymorphism (SNP) genotyping was employed to genotype the DUMI F2 animal for growth hormone (Gh), growth hormone releasing hormone (Ghrh), pituitary-specific transcription factor 1 (Pit1), and prolactin receptor (Prlr) loci, and also a microsatellite within insulin-like growth factor 1 (Igf1). Using a family-based association test (FBAT) program, a highly significant association of Gh, Pit1, and Prlr to AH50 (p < or = 0.01) and a significant association of Pit1 to CH50 (p < or = 0.05) were found. Using the SAS system for mixed model, a highly significant association of Gh, and Igf1 to AH50 and CH50 (p < or = 0.01) was detected, while Prlr and Ghrh had a highly significant association (p < or = 0.01) with CH50 only.

Verification of chromosomal regions affecting the innate immunity in pigs using linkage mapping.

Understanding the genetic control of innate immunity in pigswould offerthe opportunity to utilize natural variation and improve selective breeding programmes. As part of our porcine genome scan to identify quantitative trait loci (QTL) we examined immune response traits in a Duroc x Berlin miniature pig resource family (DUMI). Complement activity via classical (CH50) and alternative (AH50) pathways, antibody response to Mycoplasma hyopneumoniae (Mh), tetanus toxoid (TET) and PRRS virus (PRRSV), the complement component (C3c), and Haptoglobin serum concentration (HP) were used as phenotypes for linkage mapping. A total of 220 backcross animals were used for the QTL analysis. Blood was collected six times from each animal prior to and after vaccinations against Mycoplasma hyopneumoniae, tetanus toxoid and PRRS, respectively. Seventy-four microsatellites from 18 autosomes were used for QTL mapping. The analyses were performed treating the measurements of phenotypes at different time points as single traits. Forty-two significant and 24 highly significant QTL were detected, using the program QTL Express, for all immune traits using the single traits. Most QTL were detected on SSC3, SSC16, and SSC18. No significant F-value corresponded to data for SSC12 and SSC13.

Genetic aspects concerning drip loss and water-holding capacity of porcine meat.

The amount and distribution of water inside the meat has a considerable influence on its properties. High losses of fluid in the form of drip may affect financial output, nutritional value, consumer appeal and/or technological properties of porcine meat. Therefore, a deeper insight into the traits water-holding capacity (WHC) and drip is favourable on behalf of producers, industry and consumers. Similar to most meat quality traits, WHC and drip loss (DRIP) are moderately heritable. The genetic correlation between these two traits is high. Correlation to other meat quality traits, such as pH value, cooking loss, reflectance, etc. is existent as predictable. Two major genes are known, RYR1 on chromosome 6 and RN on chromosome 15, to influence meat quality in general and WHC in particular. Furthermore, a number of candidate genes exist, e.g. phosphoglycerate mutase 2. Within the variety of quantitative trait loci (QTL) experiments, a number of QTL have been identified. QTL for DRIP and/or WHC have been found on chromosome 1, 2, 4, 5, 6, 11, 13, 14, 15, 18; for cooking loss on 7, 14 and18, and for pH value on nearly all chromosomes. Recently, a QTL study for meat quality and body composition traits in a Duroc-Pietrain (DUPI) resource population has been conducted at the University of Bonn, Germany. Four QTL for DRIP were identified on chromosomes 2, 3, 5 and 18. The QTL regions are in agreement with previously published QTL for this and other related traits. Further research and finemapping has begun and candidate genes located within the QTL regions are currently under investigation. Combination and comparison of results should lead to deeper insights in the genetic background of meat quality and DRIP.

Molecular genetic analysis of porcine mannose-binding lectin genes, MBL1 and MBL2, and their association with complement activity.

Mannose-binding lectin (MBL) mediates activation of the complement system via the lectin pathway. Two forms of MBL, MBL-A and MBL-C, were characterized in rodents, rabbits, bovine and rhesus monkeys, whereas only one form was identified in humans, chimpanzees and chickens. The two forms are encoded by two distinct genes named MBL1 and MBL2, which have been identified in many species including the pig. In this report, we studied the two porcine genes MBL1 and MBL2. The porcine MBL genes had higher identities to bovine rather than primate and rodent sequences. Both genes were assigned to chromosome 14 by radiation hybrid panel and linkage mapping. Both MBL genes were highly expressed in liver. MBL1 was also found to be expressed in the lung, testis and brain, whereas low expression of MBL2 was detected in the testis and kidney. New single nucleotide polymorphisms of porcine MBL2 gene were found and genotyped in an experimental F2 pig population, together with a previously reported SNP of MBL1. MBL1 genotypes differed in C3c serum concentration, i.e. in vivo complement activity, at P < 0.1. Correspondingly, linkage analysis revealed a quantitative trait locus for C3c serum level close to the position of the MBL genes. The study thus promotes the porcine MBL genes as functional and positional candidate gene for complement activity.