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M Georges

Publications and source records attributed to M Georges.

At least 19 recordsLinked to original sources
PubMed2006

Measuring the extent of linkage disequilibrium in commercial pig populations.

To evaluate the extent of linkage disequilibrium in domestic pigs, we genotyped 33 and 44 unrelated individuals from two commercial populations for 29 and five microsatellite markers located on chromosomes 15 and 2 respectively. A high proportion of marker pairs up to 40 cM apart exhibited significant linkage disequilibrium in both populations. Pair-wise r(2) values averaged between 0.15 and 0.50 (depending on chromosome and population) for markers <1 cM apart and declined to values of 0.05 for more distant syntenic markers. Our results suggest that both populations underwent a bottleneck approximately 20 generations ago, which reduced the effective population size from thousands to <200 animals.

Alleles↗
PubMed2006

Results of a whole-genome quantitative trait locus scan for growth, carcass composition and meat quality in a porcine four-way cross.

A whole-genome quantitative trait locus (QTL) scan for 31 phenotypes related to growth, carcass composition and meat quality was conducted using 1187 progeny of a commercial four-way cross. Animals were genotyped for 198 microsatellite markers that spanned the entire porcine genome. QTL analysis was conducted to extract information from paternal and maternal meioses separately using a rank-based nonparametric approach for half-sib designs. Nine QTL exceeded genome-wide significance: one QTL affecting growth (average daily gain on SSC1), two QTL influencing carcass composition (fatness on SSC3 and muscle mass on SSC15) and six QTL influencing meat quality (tenderness on SSC4 and SSC14; colour on SSC5, SSC6 and SSCX; and conductivity on SSC16). All but one of these coincided with previously reported QTL. In addition, we present evidence for 78 suggestive QTL with a combined false discovery rate of 40%.

Animals↗
PubMed2006

A 2.5-Mb contig constructed from Angus, Longhorn and horned Hereford DNA spanning the polled interval on bovine chromosome 1.

The polled locus has been mapped by genetic linkage analysis to the proximal region of bovine chromosome 1. As an intermediate step in our efforts to identify the polled locus and the underlying causative mutation for the polled phenotype, we have constructed a BAC-based physical map of the interval containing the polled locus. Clones containing genes and markers in the critical interval were isolated from the TAMBT (constructed from Angus and Longhorn genomic DNA) and CHORI-240 (constructed from horned Hereford genomic DNA) BAC libraries and ordered based on fingerprinting and the presence or absence of 80 STS markers. A single contig spanning 2.5 Mb was assembled. Comparison of the physical order of STSs to the corresponding region of human chromosome 21 revealed the same order of genes within the polled critical interval. This contig of overlapping BAC clones from horned and polled breeds is a useful resource for SNP discovery and characterization of positional candidate genes.

Animals↗
PubMed2006

Proteomic analysis of ovine muscle hypertrophy.

Two-dimensional electrophoresis was used to investigate the effects of a QTL for muscle hypertrophy on sarcoplasmic protein expression in ovine muscles. In the Belgian Texel breed, the QTL for muscle hypertrophy is localized in the myostatin-encoding gene. Based on microsatellite markers flanking the myostatin gene, we compared the hypertrophied genotype with the normal genotype. The average age of the sheep was 3 mo. Among the 4 muscles studied, in the hypertrophied genotype only the vastus medialis was normal, whereas the semimembranosus, tensor fasciae latae, and LM were hypertrophied. In the hypertrophied genotype, these muscles showed upregulation of enzymes involved in glycolytic metabolism together with oxidative metabolism in LM. Certain chaperone proteins, including glutathione S-transferase-Pi, heat shock protein-27, and heat shock cognate-70, were also more highly expressed, probably due to increased use of energetic pathways. Expression of the iron transport protein transferrin was increased. Alpha-1-antitrypsin was the only protein showing a similar pattern of expression (i.e., less expressed) in all 4 muscles of the hypertrophied genotype. It is suggested that transferrin and alpha-1-antitrypsin may interact to reinforce myogenic proliferative signaling.

Animals↗
PubMed2004

Detection and characterization of SNPs useful for identity control and parentage testing in major European dairy breeds.

We propose the use of single nucleotide polymorphisms (SNPs) instead of polymorphic microsatellite markers for individual identification and parentage control in cattle. To this end, we present an initial set of 37 SNP markers together with a gender-specific SNP for identity control and parentage testing in the Holstein, Fleckvieh and Braunvieh breeds. To obtain suitable SNPs, a total of 91.13 kb of random genomic DNA was screened yielding 531 SNPs. These, and 43 previously identified SNPs, were subjected to the following selection criteria: (1) the frequency of the minor allele must be larger than 0.1 in at least two of the three examined breeds, and (2) markers should not be linked closely. Allele frequencies were estimated by analysing sequencing traces of pooled DNA or by genotyping individual DNA samples. The selected SNP loci were physically mapped by radiation hybrid mapping or by fluorescence in situ hybridization, and tested against the neutral mutation hypothesis. The presented marker set theoretically allows probabilities of identity less than 10(-13) for individual verification and exclusion powers exceeding 99.99% for parentage testing.

Agriculture↗
PubMed2004

Effects of a quantitative trait locus for muscle hypertrophy from Belgian Texel sheep on carcass conformation and muscularity.

A QTL for muscle hypertrophy has been identified in the Belgian Texel breed. A population of F2 and backcross lambs created from crosses of Belgian Texel rams with Romanov ewes was studied. Effects on carcass traits and muscle development of the Belgian Texel breed polygenes and Belgian Texel single QTL were compared. In both cases, carcass conformation and muscularity were improved. The Texel polygenic environment improved conformation mainly through changes in skeletal frame shape. Segments were shorter and bone weight lower. Muscles were more compact, shorter, and thicker. The single QTL affected muscle development. Thickness and weight of muscles were increased. Composition in myosin changed toward an increase of fast contractile type. The relative contribution of hind limb joint to carcass weight was increased. Differences in skeletal frame morphology among the three genotypes of the single QTL were small. Conformation scoring was mainly influenced by leg muscularity. Back and shoulder muscle development, which largely contributed to variability of muscularity, were less involved in the conformation scoring. Lastly, the QTL explains a small part of differences between these Belgian Texel and Romanov breeds for conformation or muscle development. A large part of genetic variability remains to be explored.

Animals↗
PubMed2001

Contribution of domestic animals to the identification of new genes involved in sex determination.

Among farm animals, two species present an intersex condition at a relatively high frequency: pig and goat. Both are known to contain XX sex-reversed individuals which are genetically female but with a true hermaphrodite or male phenotype. It has been clearly demonstrated that the SRY gene is not involved in these phenotypes. Consequently, autosomal or X-linked mutations in the sex-determining pathway may explain these sex-reversed phenotypes. A mutation referred to as "polled" has been characterized in goats by the suppression of horn formation and abnormal sexual differentiation. The Polled Intersex Syndrome locus (PIS) was initially located in the distal region of goat chromosome 1. The homologous human region has been precisely identified as an HSA 3q23 DNA segment containing the Blepharophimosis Ptosis Epicanthus locus (BPES), a syndrome combining Premature Ovarian Failure (POF) and an excess of epidermis of the eyelids. In order to isolate genes involved in pig intersexuality, a similar genetic approach was attempted in pigs using genome scanning of resource families. Genetic analyses suggest that pig intersexuality is controlled multigenically. Parallel to this work, gonads of fetal intersex animals have been studied during development by light and electron microscopy. The development of testicular tissue and reduction of germ cell number by apoptosis, which simultaneously occurs as soon as 50 days post coïtum, also suggests that several separate genes could be involved in pig intersexuality.

Animals↗
PubMed2001

Recent progress in livestock genomics and potential impact on breeding programs.

Most of the major livestock breeding organizations in the world are actively involved in using the emerging tools for genome analysis to obtain a better understanding of the molecular architecture of their favourite production traits. This is bound to generate a considerable amount of novel biological information that will provide a competitive advantage to those that have access to it. At present, the preferred avenue to exploit this information is via marker-assisted selection (MAS), and several breeding organisations are starting to implement MAS in breeding programs. However, it seems unlikely that the exploitation of genomics information will be limited to MAS in the future. Even though it is difficult to anticipate the ultimate impact of genomics on animal production, it would be very surprising if it were not to revolutionize this industry as it is already revolutionizing the biomedical and plant breeding industries.

Animals↗
PubMed2001

Fine-mapping and construction of a bovine contig spanning the ovine callipyge locus.

The callipyge (CLPG) gene was fine-mapped by linkage analysis to a 4.6-cM chromosome interval on distal ovine OAR18q, flanked by microsatellite markers IDVGA30 and OY3. The OAR18q linkage map and human HSA14q transcript map were aligned by genotyping two bovine-hamster whole-genome radiation hybrid panels with the microsatellite markers, as well as with sequences corresponding to HSA 14q genes. Using Type I loci mapping to the IDVGA30-OY3 interval as anchor points, we have constructed a 1.4-Mb bovine BAC contig containing the IDVGA30-OY3 interval. We demonstrate that the IDVGA30-OY3 interval spans approximately 770 kb and contains at least four genes: YY1, WARS, DLK1, and GTL2.

Animals↗
PubMed2001

The callipyge mutation enhances the expression of coregulated imprinted genes in cis without affecting their imprinting status.

The callipyge (CLPG) phenotype (from kappa(alpha)lambda(iota), "beautiful," and pi(iota)gamma(epsilon), "buttocks") described in sheep is an inherited muscular hypertrophy that is subject to an unusual parent-of-origin effect referred to as polar overdominance: only heterozygous individuals having inherited the CLPG mutation from their sire exhibit the muscular hypertrophy. The callipyge (clpg) locus was mapped to a chromosome segment of approximately 400 kb (refs. 2-4), which was shown to contain four genes (DLK1, GTL2, PEG11 and MEG8) that are preferentially expressed in skeletal muscle and subject to parental imprinting in this tissue. Here we describe the effect of the CLPG mutation on the expression of these four genes, and demonstrate that callipyge individuals have a unique expression profile that may account for the observed polar overdominance.

Animals↗
PubMed2001

Differential expression of the GTL2 gene within the callipyge region of ovine chromosome 18.

The inheritance pattern of the skeletal muscle hypertrophy phenotype caused by the callipyge gene has been characterized as polar overdominance. We hypothesized that this trait may be caused by a gain or loss of gene expression because of the reversible nature of the phenotype in paternal vs. maternal inheritance. Suppression subtraction cDNA probes were made from skeletal muscle mRNA of normal (NN) and callipyge (C(Pat)N(Mat)) animals and hybridized to Southern blots containing bacterial artificial chromosomes (BACs) that comprise a physical contig of the callipyge region. The CN-NN probes hybridized to two ovine and seven bovine BACs. Sequence analysis of fragments within those BACs indicated short regions of similarity to mouse gene trap locus (gtl2). Northern blots analysis of RNA from hypertrophy-responsive muscles show a population of GTL2 mRNA centred around 2.4 kb that were abundantly expressed in 14-day prenatal NN and C(Pat)N(Mat) lambs but were down-regulated in day 14 and day 56 postnatal NN lambs. The expression of GTL2 remained elevated in 14- and 56-day-old C(Pat)N(Mat) lambs as well as in 56-day-old N(Pat)C(Mat) and CC lambs. Expression of GTL2 in the supraspinatus, which does not undergo hypertrophy, was very low for all genotypes and ages. Isolation of cDNA sequences show extensive alternative splicing and a lack of codon bias suggesting that GTL2 does not encode a protein. The mutation of the callipyge allele has altered postnatal expression of GTL2 in muscles that undergo hypertrophy and will help identify mechanisms involved in growth, genomic imprinting and polar overdominance.

Alternative Splicing↗
PubMed2001

Human-ovine comparative sequencing of a 250-kb imprinted domain encompassing the callipyge (clpg) locus and identification of six imprinted transcripts: DLK1, DAT, GTL2, PEG11, antiPEG11, and MEG8.

Two ovine BAC clones and a connecting long-range PCR product, jointly spanning approximately 250 kb and representing most of the MULGE5-OY3 marker interval known to contain the clpg locus, were completely sequenced. The resulting genomic sequence was aligned with its human ortholog and extensively annotated. Six transcripts, four of which were novel, were predicted to originate from within the analyzed region and their existence confirmed experimentally: DLK1, DAT, GTL2, PEG11, antiPEG11, and MEG8. RT-PCR experiments performed on a range of tissues sampled from an 8-wk-old animal demonstrated the preferential expression of all six transcripts in skeletal muscle, which suggests that they are under control of common regulatory elements. The six transcripts were also shown to be subject to parental imprinting: DLK1, DAT, and PEG11 were shown to be paternally expressed and GTL2, antiPEG11, and MEG8 to be maternally expressed.

Animals↗
PubMed2001

Comparative sequence analysis of the imprinted Dlk1-Gtl2 locus in three mammalian species reveals highly conserved genomic elements and refines comparison with the Igf2-H19 region.

The Dlk1-Gtl2 domain on mouse chromosome 12 contains reciprocally imprinted genes with the potential to contribute to our understanding of common features involved in imprinting control. We have sequenced this conserved region in the mouse and sheep and included the human sequence in a three species comparison. This analysis resulted in a precise conservation map and identification of highly conserved sequence elements, some of which we have shown previously to be differentially methylated in the mouse. Additionally, this analysis facilitated identification of a CpG-rich tandem repeat array located approximately 13-15 kb upstream of Gtl2. Furthermore, we have identified a third imprinted transcript that overlaps with the last Dlk1 exon in the mouse. This transcript lacks a conserved open reading frame and is probably generated by cleavage of extended Dlk1 transcripts. Because Dlk1 and Gtl2 share many of the imprinting properties of the well-characterized Igf2-H19 domain, it has been proposed that the two regions may be regulated in the same way. Comparative genomic examination of the two domains indicates that although there are similarities, other features are very different, including the location of conserved CTCF-binding sites, and the level of conservation at regulatory regions.

Animals↗
PubMed2001

Associations between casein haplotypes and first lactation milk production traits in Finnish Ayrshire cows.

The objective of this study was to estimate the effects of beta-kappa-casein (CN) haplotypes on first-lactation milk production traits. The beta-kappa-CN haplotypes were deduced using information on beta- and kappa-CN genotypes of cows and their sires for 16,973 Finnish Ayrshire cows that had at least nine paternal half sibs. Effects of CN haplotypes on milk production traits were estimated for one haplotype at a time using an animal model, which included the fixed effects for calving year and month, age at calving, days open, beta-lactoglobulin, and a beta-kappa-CN haplotype. Differences in milk production traits were also estimated between haplotype combinations A1A+A2B and A1B+A2A within beta-kappa-CN genotype A1A2AB and between combinations A1E+A2A and A1A+A2E within genotype A1A2AE. The beta-kappa-CN haplotypes A2A and A2B were associated with high milk and protein yields and low fat content, and those that included the beta-CN A1 allele were associated with low yields and high fat content. Protein content was affected by the kappa-CN locus; haplotype A1B was associated with high protein content and A1E was with low protein content. The haplotype combination A1A+A2B was associated with 140 kg more milk yield (P = 0.045) and 0.03 percentage units less protein content (P = 0.055) than combination A1B+A2A, and combination A1A+A2E showed 0.02 percentage units greater protein content (P = 0.098) than A1E+A2A. These results indicate that genes linked to the CN loci contribute to the variation in milk yield and protein content.

Alleles↗