Evaluation of the porcine melanocortin 4 receptor (MC4R) gene as a positional candidate for a fatness QTL in a cross between Landrace and Hampshire

Melanocortin 4 receptor (MC4R) is expressed in the appetite-regulating areas of the brain where it is central in the regulation of feed intake and energy balance. A mutation in MC4R causing an Asp298Asn substitution has been associated with fatness, high daily gain and feed intake in the pig. In a previously performed genome scan based on a Hampshire x Landrace cross, we detected one quantitative trait loci (QTL) affecting carcass fat/meat ratio and one QTL affecting the biceps femoris muscle, both close to the position of MC4R on porcine chromosome 1. In this study, the two lines were found to be close to fixation for alternative alleles of the Asp298Asn polymorphism. Additional QTL analyses supported our hypothesis of MC4R as a positional candidate gene but only for the fat/meat QTL. The Asp298Asn polymorphism was also evaluated as a selection target for daily gain in a Danish pig breeding population that included four breeds (Hampshire, Duroc, Landrace and Yorkshire). Over a 12-year period (1990-2002), a significant increase in the allele frequency of 298Asn was found in Landrace and Duroc, whereas a non-significant decrease in the 298Asn allele frequency was observed in Yorkshire. The Hampshire breed was fixed for the 298Asn allele in 1990. The high 298Asn allele frequencies in Hampshire, Landrace and Duroc are most likely due to selection for daily gain, whereas selection for daily gain in the Yorkshire breed apparently focuses on other loci.     

Association between LEPR and MC4R genes polymorphisms and composition of milk from sows of dam line

The polymorphisms of LEPR and MC4R genes are involved in appetite control mechanisms and indirectly associated with level of fat content in pig carcasses. Therefore, the aim of our study was to determine if both polymorphisms have an effect on components of colostrum and milk of sows. In our study we used gilts of two Polish breeds: Polish Landrace and Polish Large White, which belong to dam-line in Polish breeding. Colostrum and milk of sows were collected in 7, 14 and 21 day of lactation to assay solids, total protein, fat and lactose. The obtained results showed, that the observed mutation (G/A 1426 MC4R) had a significant effect mainly on the fat and solids content of colostrum. Animals with the MC4R ^AA genotype had 2.13 and 1.91 % (P ≤ 0.01) lower fat content of colostrum compared to sows with the MC4R ^GG genotype and heterozygous MC4R ^AG. The presence of the MC4R ^A allele in the animals’ genotype contributed to a decrease in fat and solids content of colostrum. The LEPR/HpaII mutation was found to have a considerable effect on the level of most colostrum components (fat, protein and solids) in both pig breeds. Significant decrease in the value of the colostrum components (except lactose) was observed only for animals with the allele LEPR ^B. The results obtained suggest that these genes might be used in selection of dam-line pigs as genetic markers of milk quality.     

Missense mutations in exon 4 of the porcine LEPR gene encoding extracellular domain and their association with fatness traits

Three non-synonymous single nucleotide polymorphisms (T221C, T232A and C233T) were detected in exon 4 of the porcine leptin receptor (LEPR) gene. The T232A substitution could be identified as a (Tsp509I) restriction fragment length polymorphism. The frequency of genotype TT varied in six genetic groups from 0.62 (Duroc) to 0.99 (Polish Large White). Sequencing of exon 4, performed for 30 animals, revealed that only two intragenic haplotypes (TC and AT at nucleotide position 232-233) were present. The phenotypic effect of the Tsp509I polymorphism was tested for the Polish Landrace (n = 241) and a synthetic line 990 (n = 243). There was no statistical evidence for the direct effect of the LEPR polymorphisms on fatness traits. However, in Polish Landrace allele A at position 232 was associated with thicker backfat over shoulder.     

A melanocortin-4 receptor (MC4R) polymorphism is associated with performance traits in divergently selected Large White pig populations

The melanocortin-4 receptor (MC4R) has a vital role in the control of energy balance and the genetic basis of obesity. A polymorphism, which results in the replacement of aspartic acid with asparagine at position 298 of the porcine MC4R gene, within the seventh transmembrane domain, has previously been described. In the current study, allele frequencies for this Asp298Asn polymorphism were investigated in lines of Large White pigs which had been divergently selected for seven generations based on lean food conversion (LFC), lean growth with ad libitum feeding (LGA), lean growth with restricted feeding (LGS) and daily feed intake (DFI). The association of the Asp298Asn polymorphism with performance traits in these lines was assessed. The frequency of Asp298 was higher (P < 0.001) in the LFC high line (0.48) than the low line (0.00), while the frequency of Asn298 was higher (P < 0.01) in the LGA high line (0.22) than the low line (0.04). When analysed across all lines, the Asp298Asn polymorphism was significantly associated with ultrasonic backfat depth, average daily gain and daily feed intake (P < 0.05). Asp298 homozygous animals had mean values of 13.3 mm, 733 g and 1933 g for backfat, average daily gain and daily feed intake respectively, compared with 14.7 mm, 805 g and 2098 g for Asn298 homozygotes. Therefore, the data support a role for the MC4R Asp298Asn polymorphism in the genetic basis of economically important traits in Large White pigs.     

H-FABP、MC4R、ADD1基因多态性在3个猪群中分布及其与肌内脂肪和背膘的相关研究

具有不同遗传特性的猪种具有不同的肉质性状。尤其是地方品种和引进品种间在肉质性状存在极大的差异。在已有的研究中H-FABP,MC4R,ADD1基因同肌内脂肪或背膘相关。利用梅山猪、苏太猪和杜×长×大猪为试验动物,研究上述3个基因的多态性分布和多态性同肌内脂肪和背膘的相关性。结果表明：3个基因的多态性分布在不同猪种间存在极显著的差异,这种差异可能是肌内脂肪（IMF）或背膘（BF）不同的主要原因之一。连锁分析表明：H-FABP和ADD1基因多态性同IMF有显著的相关,但是同BF没有显著的相关;MC4R基因的多态性同IMF和BF都有显著相关性。说明：H-FABP和ADD1基因多态性有可能应用到提高IMF,同时不影响BF的育种实践中。      

SNPs in the porcine <Emphasis Type="Italic">PPARGC1a</Emphasis> gene: Interbreed differences and their phenotypic effects

Due to its function, the peroxisome proliferative activated receptor-γ, coactivator-1α (PPARGC1A) gene is a candidate in the search for genes that may affect production traits in the pig. The purpose of this study was to screen for new SNPs in exon 8 of the porcine PPARGC1A gene and to test their possible association with production traits. Altogether 736 pigs representing five breeds Polish Landrace, n=242; Polish Large White, n=192; Hampshire, n=27; Duroc, 21; Pietrain, n=12) and synthetic line 990 (n=242) were scanned via SSCP assay. Four SNPs were found; two new ones: C/G (His338Gln) and G/A Thr359Thr), and two previously reported ones: C/A (Arg369Arg) and T/A Cys430Ser). The missense T/A and C/G SNPs demonstrated pronounced interbreed variability in terms of allele frequencies, including the exclusive presence of the C/G substitution in the Hampshire breed. The tested SNPs occurred in five putative haplotypes, and their frequency also differed substantially between breeds. The association of the SNPs with production traits was tested for G/A (Thr359Thr), C/A (Arg369Arg) and T/A (Cys430Ser) substitutions in Polish Large White, Polish Landrace and line 990. The analysis revealed only breed-specific associations. The T/A (Cys430Ser) SNP was related to the feed conversion ratio in the Polish Large White (P=0.02), and the silent G/A and C/A substitutions were respectively associated with abdominal fat in line 990 and backfat thickness in Polish Landrace (P=0.04). The combined effects of the substitutions were estimated as haplotype effects. Three significant contrasts between haplotypes were calculated, but the observed associations were again only breed-specific.     

Association od the DdeI growth hormone gene polymorphism with some performance traits in Polish Large White and Czech Large White x Polish Large White pigs

The genotypes of growth hormone gene polymorphisms (GH-DdeI, GH-MspI, GH-HaeII, GH-ApaI, GH-CfoI) were determined in 78 pigs [Czech Large White sires (CLWsire line) x Polish Large White (PLW) sows, Polish Large White sires x Polish Large White sows], by the PCR-RFLP method. Preliminary studies found only GH DdeI polymorphism to be associated with performance traits. The associations of this polymorphism with growth and carcass traits were investigated. The linear model included the effects of candidate genes, genetic groups, sex and linear covariables of age at slaughter and body weight at weaning. The DdeI polymorphism of the GH gene showed associations with carcass length (P 相似文献   

Bovine melanocortin receptor 4: cDNA sequence, polymorphisms and mapping

A cDNA encoding the bovine melanocortin receptor 4 (MC4R) was cloned and sequenced. Comparing human, pig and rat homologues showed a 87, 85 and 89% identity on the DNA level, respectively, and over 90% on the protein level. The bovine MC4R gene was mapped to BTU 24 by radiation hybrid mapping. Two nucleotide changes were identified by single stranded conformation polymorphism (SSCP) and sequencing. The substitutions proved to be a T to C and G (allele B) to A (allele A) resulting, respectively, in a conservative valine to alanine substitution (Val 145 Ala) and an alanine to threonine (Ala 172 Thr). Using PCR-RFLP, 13 different cattle breeds were screened for the presence of the Ala 172 Thr substitution. With the exception of one Red Pied animal, allele A could only be detected in Red Holstein animals.     

Detailed characterization of the porcine MC4R gene in relation to fatness and growth

In contrast to the human MC4R gene, where multiple variants have been described, several of which are associated with appetite and obesity, few MC4R variants have been reported in the pig. The most interesting polymorphism reported to date in the pig is p.Asp298Asn, which is significantly associated with variation in growth and fatness traits in most breeds and crosses. However, some reports have seemingly failed to confirm this association. The discrepancy of p.Asp298Asn associations in some pig populations suggested that further discovery of SNPs in MC4R would be useful. Utilizing the recently released pig genome sequence information, we obtained the whole MC4R genome sequence and detected five additional SNPs, a variable (CA) _n repeat and a C indel in the ISU Berkshire × Yorkshire pig resource family. Linkage disequilibrium (LD) analysis revealed that the additional five SNPs were not in strong LD with p.Asp298Asn, but single marker association analysis indicated that they were significantly ( P  <   0.05) associated with fatness measures and very highly significantly ( P  <   0.0001) associated with average daily gain on test (ADGTEST). Three major haplotypes were identified and the subsequent association analyses suggested that the two non-synonymous SNPs had different effects, e.g. p.Arg236His influenced back fat and growth on test while p.Asp298Asn was primarily associated with variation in growth rate in this population. An interaction effect between these two SNPs was found for ADGTEST, which may partly explain some of the previous discrepancies reported for MC4R in different pig populations . Examination of the p.Arg236His polymorphism in populations where the effect of p.Asp298Asn is limited is warranted.     

兔黑素皮质素受体4(MC4R)基因多态性及其与体重及屠体性状的关联研究

以哈尔滨白兔、天府黑兔、比利时兔、齐卡巨型兔以及加利福尼亚兔5个肉兔品种共220个个体为研究对象, 采用PCR-SSCP技术和克隆测序技术进行SNPs检测和基因型的分析。结果发现兔MC4R基因237位发生转换突变(A→G), 5个品种内的AA基因型和A等位基因频率均分别高于AG基因型和G等位基因, 而哈尔滨白兔、比利时兔以及齐卡巨型兔3个品种兔的AG基因型频率和G等位基因频率明显高于天府黑兔和加利福尼亚兔。单位点基因型与屠体性状、饲料转化率以及熟肉率的最小二乘分析表明; AG基因型与兔的体重、全净膛重以及饲料转化率有显著的关系(P<0.05), 而与熟肉率的关系不显著(P>0.05)。结果表明, MC4R基因可以作为影响和控制兔体重及屠体性状的候选基因。     

A +2138InsCAGACC polymorphism of the melanocortin receptor 3 gene is associated in human with fat level and partitioning in interaction with body corpulence

BACKGROUND: The melanocortin system includes five receptors (MC1R to MC5R), and mouse and human MC4R has been shown to be involved in the regulation of feeding, and mouse MC3R in body composition. To verify a possible similar effect of MC3R in humans, we analyzed one insertion and one single nucleotide polymorphism by restriction fragment length polymorphisms (RFLP), and a microsatellite (D20S32e) in relation to body composition and glucose metabolism. METHODS: Eight hundred twelve subjects of the Québec Family Study (QFS) cohort were analyzed for body composition, food intake, and energy metabolism phenotypes. Southern Blot with the complete MC3R cDNA was used to detect a new +2138InsCAGACC variant by Pst1 restriction. PCR-RFLP with BsaJ1 was used to type amino acid polymorphism V81I arising from a G241A nucleotide change. PCR and automatic DNA sequencers were used for the analysis of the TG dinucleotide repeat D20S32e located between -1933/-1892 of MC3R. In a covariance analysis among genotypes, phenotypes were adjusted for age and sex as covariates. Food intake and energy metabolism phenotypes were also adjusted for body mass index (BMI), and leptin and abdominal fat, as assessed by a computed tomography scan, for fatness using six skinfold thicknesses. RESULTS: An association between the +2138InsCAGACC MC3R polymorphism was observed with fat mass (FM), percent body fat (%FAT), and total abdominal fat (ATF). Homozygote subjects for the +2138 insertion variant allele in normal weight (BMI < 25 kg/m(2)) and overweight (25 < or = BMI < 30 kg/m(2)) subjects showed a similar level of fatness despite the overall difference in BMI. In normal weight, homozygotes for the insertion allele showed higher mean values than heterozygotes and homozygotes for wild-type allele without insertion (%FAT: 24.0 +/- 1.1 versus 19.3 +/- 0.9 and 20.5 +/- 0.8, p = 0.0005; FM: 15.7 +/- 0.9 kg versus 11.7 +/- 0.7 kg and 12.6 +/- 0.6 kg, p = 0.0003). In contrast, overweight subjects homozygote for the variant allele showed lower mean values (%FAT: 27.0 +/- 1.2 versus 31.4 +/- 0.8 and 30.9 +/- 0.7, p = 0.002; FM: 18.3 +/- 1.0 kg versus 22.8 +/- 0.8 kg and 22.0 +/- 0.6 kg, p = 0.0001). This resulted in a similar level of body fat between both BMI groups for subjects homozygote for the insertion allele versus wild-type allele carriers (%FAT: +/-2-3% versus +/-10-12%; FM: +/-2 kg versus +/-9-11 kg). In obese subjects (BMI > or = 30 kg/m(2) ), a lower level of ATF was seen (-15%, p = 0.002). Other polymorphisms and phenotypes tested showed no association. CONCLUSION: A new 12138InsCAGACC MC3R polymorphism is associated with the level of adiposity and with body fat partitioning in interaction with corpulence in humans.     

The Asp298Asn missense mutation in the porcine melanocortin-4 receptor ( MC4R) gene can be used to affect growth and carcass traits without an effect on meat quality

A promising tool to improve daily gain in pigs is the missense mutation (Asp298Asn) in the melanocortin-4 receptor (MC4R) gene, especially in the Belgian pig industry where the slow-growing Piétrain breed is very frequently used as the sire breed. The MC4R is expressed in the appetite-regulating region of the brain where it regulates feed intake and energy balance. The mutation has been associated with differences in fatness, daily gain and feed intake. However, less information on the correlated effects on meat quality is available. In order to evaluate the influence of the MC4R mutation on carcass and meat quality parameters, a total of 1155 pigs of a four-way cross were slaughtered at an average live weight of 109 kg, and data about daily live-weight gain, carcass and meat quality were collected. Allelic frequencies were 0.69 for the G-allele (298Asp variant or well-conserved variant) and 0.31 for the A-allele (298Asn variant or the mutated variant). Barrows and gilts were almost equally distributed in this population with, respectively, 49.9% and 50.1%. Moreover, independent of this mutation, the relationship between average daily gain (ADG) and carcass on the one hand and meat quality traits on the other hand was evaluated in this population. A significant positive influence of the MC4R mutation on ADG (P < 0.001) was found, accompanied by a higher fat thickness (P < 0.05) and a lower carcass lean meat content (P < 0.01), whereas muscle thickness and carcass conformation traits were not affected. The effects on meat quality traits were not significant, except for a lower shear force (P = 0.054) and a higher intramuscular fat content (P = 0.052) in AA animals. In the longissimus, pH and pork quality meter (PQM) values were not influenced, and effects on drip loss and colour were not apparent. Residual correlation coefficients between ADG and carcass lean meat content on the one hand and meat quality traits on the other hand were generally very low (|r|>0.1). Higher ADG, higher carcass fat thickness and lower carcass lean meat content were correlated with slightly lower shear force values (|r|～0.1, P < 0.05). In conclusion, in the studied population, the Asp298Asn mutation in the MC4R gene was associated with improved daily gain, higher carcass fatness and almost no effect on meat quality traits.     

Study of the differential transcription in liver of growth hormone receptor (GHR), insulin-like growth factors (IGF1, IGF2) and insulin-like growth factor receptor (IGF1R) genes at different postnatal developmental ages in pig breeds

The objective of this study was to determine hepatic expression levels of GHR, IGF1R, IGF1 and IGF2 genes in young growing gilts at different developmental ages (60–210 days) in five pig breeds: Polish Large White (PLW), Polish Landrace (PL), Pulawska (Pul), Duroc (Dur) and Pietrain (Pie). We studied the differences among pig breeds as well as within each breed for pigs in different developmental ages. Obtained results revealed major differences among breeds in hepatic gene expression of porcine GHR, IGF1R, IGF1 and IGF2 genes in different developmental ages. The differences among breeds of GHR expression were significantly higher in PLW, PL at the age of 60, 90, 120 days as compared to Pul, Dur and Pie. In turn, the highest level of IGF1R expression was observed in PL at age of 150, 180 and 210 days, whereas in case of IGF1 the highest level was recorded in Pie gilts at the age of 60 and 90 days. Moreover trait associated study revealed highly significant correlations between hepatic expressions of IGF1R and IGF2 genes and carcass composition traits (P < 0.01) The results of study suggest that porcine GHR, IGF1R, IGF1 and IGF2 genes may be potential candidate genes for postnatal growth and carcass composition traits. Therefore, the implementation of the hepatic expression of GH/IGF genes into the pig breeding and gene assisted selection program in different pig breeds should be considered. However, further population wide study is needed to clarify the hepatic expression association with economic traits, such as body growth, meat quality and carcass composition traits.     

Association of a New SNP in Promoter Region of the Porcine FABP3 Gene with Fatness Traits in a Polish Synthetic Line

Associations between FABP3 (alternatively named H-FABP) gene polymorphisms and fatness traits were tested in two pig breeds (Polish Large White and Polish Landrace) and one synthetic line—990. Three known single nucleotide polymorphisms, detected by HinfI, MspI and HaeIII restriction enzymes, were analyzed. Moreover, three new polymorphisms in the 5′ regulatory region were identified: C(–221)T, C(–160)G and T(?158)G, but only the third one was widely distributed and correlated with backfat thickness in line 990. The obtained results suggest that the FABP3 gene is linked with an unknown gene directly affecting backfat thickness, but the analyzed polymorphisms do not influence fatness traits.