Polymorphisme génétique des lactoprotéines caprines

Abstract

The purpose of this paper is to summarize our current knowledge in the field of genetic polymorphism of the 6 main goat milk proteins: a-Iactalbumin, IHactoglobulin and asl-' a52-, f3- and x-ceseins. Referring to their bovine counterparts, the structural characteristics of these proteine, as weil as the impact of non-genetic factors (essentially post-translational) have been analyzed. This has been followed by a brief review of our current knowledge of the main milk protein gene structure. These structural analyses following genetic studies have led to the demonstration, in the goat, of the existence of a particularly rich and original system which constitutes one of the main subjects of this paper. Goat aS1- casein Is a remarkable model in which a quantitative allelic variability further adds to the classical structural polymorphism. The most recent genomic data show that this extensive and unusual polymorphism is under the control of at least 14 alleles at the as l-Cn locus, distributed in 6 different classes of protein variants, which are divided into 4 levels of expression. The establishment of the overall structural organization of the gene and the partial characterization of most of the known alleles have provided the information necessary for the development of a typing procedure based on the polymerase chain reaction (peRj technique. This procedure, which allows genotyping of animais at birth, and even during embryonic development should aid in increasing the efficiency of selection programmes and thereby contribute to the improvement of the cheese-making quality of goat milks.}, Year = {1993} } @article{g.682, Author = {Pettit, Frank K. and Bare, Emiko and Tsai, Albert and Bowie, James U.}, Title = {HotPatch: A Statistical Approach to Finding Biologically Relevant Features on Protein Surfaces}, Journal = {Journal of Molecular Biology}, Volume = {369}, Number = {3}, Pages = {863-879}, Note = {g.682}, Abstract = {We describe a fully automated algorithm for finding functional sites on protein structures. Our method finds surface patches of unusual physicochemical properties on protein structures, and estimates the patches' probability of overlapping functional sites. Other methods for predicting the locations of specific types of functional sites exist, but in previous analyses, it has been difficult to compare methods when they are applied to different types of sites. Thus, we introduce a new statistical framework that enables rigorous comparisons of the usefulness of different physicochemical properties for predicting virtually any kind of functional site. The program's statistical models were trained for 11 individual properties (electrostatics, concavity, hydrophobicity, etc.) and for 15 neural network combination properties, all optimized and tested on 15 diverse protein functions. To simulate what to expect if the program were run on proteins of unknown function, as might arise from structural genomics, we tested it on 618 proteins of diverse mixed functions. In the higher-scoring top half of all predictions, a functional residue could typically be found within the first 1.7 residues chosen at random. The program may or may not use partial information about the protein's function type as an input, depending on which statistical model the user chooses to employ. If function type is used as an additional constraint, prediction accuracy usually increases, and is particularly good for enzymes, DNA-interacting sites, and oligomeric interfaces. The program can be accessed online (at http://hotpatch.mbi.ucla.edu).}, Keywords = {functional site prediction structural genomics active sites annexin caspase-7}, Year = {2007} } @article{g.683, Author = {Remeuf, F.}, Title = {Influence du polymorphisme génétique de la caséine As1 caprine sur les caractéristiques physico-chimiques et technologiques du lait}, Journal = {Lait}, Volume = {73}, Pages = {511-532}, Note = {g.683}, Abstract = {The present work aimed to study the effet of asl-easein genetic variants on physico-chemical characteristics, cheese-making properties, and heat stability of goat's milk. The study was based on an analysis of 153 individual milk samples which were obtained from 3 types of goats homozygous at the asl-Cn locus: AA, EE and FF (51 samples of each type). Results showed that genotype had a very significant effect (AA > EE> FF) on fat, total nitrogen, protein and casein content, and on casein number (casein Nltotal N). Whereas asl-easein type had a Iimited effect on minerai and salt equilibria, it had a marked influence on micellar size (AA < EE and FF) and to a lesser extent on micellar mineralization. As far as technological properties were concerned, the most important differences were observed with rennet gel strength (AA > EE> FF) and gel strengthening rate (AA > EE and FF). Micro-scale cheese-making carried out on 23 small bulk milks showed that dry matter and nitrogen recovery coefficients were 4 to 5% lower in FF than in AA milks. On the other hand, no difference was found in heat stability between the 3 types of milk.}, Year = {1993} } @article{g.684, Author = {Bernardi, Giorgio}, Title = {The neoselectionist theory of genome evolution}, Journal = {Proceedings of the National Academy of Sciences}, Volume = {104}, Number = {20}, Pages = {8385-8390}, Note = {g.684}, Abstract = {The vertebrate genome is a mosaic of GC-poor and GC-rich isochores, megabase-sized DNA regions of fairly homogeneous base composition that differ in relative amount, gene density, gene expression, replication timing, and recombination frequency. At the emergence of warm-blooded vertebrates, the gene-rich, moderately GC-rich isochores of the cold-blooded ancestors underwent a GC increase. This increase was similar in mammals and birds and was maintained during the evolution of mammalian and avian orders. Neither the GC increase nor its conservation can be accounted for by the random fixation of neutral or nearly neutral single-nucleotide changes (i.e., the vast majority of nucleotide substitutions) or by a biased gene conversion process occurring at random genome locations. Both phenomena can be explained, however, by the neoselectionist theory of genome evolution that is presented here. This theory fully accepts Ohta's nearly neutral view of point mutations but proposes in addition (i) that the AT-biased mutational input present in vertebrates pushes some DNA regions below a certain GC threshold; (ii) that these lower GC levels cause regional changes in chromatin structure that lead to deleterious effects on replication and transcription; and (iii) that the carriers of these changes undergo negative (purifying) selection, the final result being a compositional conservation of the original isochore pattern in the surviving population. Negative selection may also largely explain the GC increase accompanying the emergence of warm-blooded vertebrates. In conclusion, the neoselectionist theory not only provides a solution to the neutralist/selectionist debate but also introduces an epigenomic component in genome evolution.}, Year = {2007} } @article{g.685, Author = {Kouyos, Roger D. and Silander, Olin K. and Bonhoeffer, Sebastian}, Title = {Epistasis between deleterious mutations and the evolution of recombination}, Journal = {Trends in Ecology & Evolution}, Volume = {22}, Number = {6}, Pages = {308-315}, Note = {g.685}, Abstract = {Epistasis and the evolution of recombination are closely intertwined: epistasis generates linkage disequilibria (i.e. statistical associations between alleles), whereas recombination breaks them up. The mutational deterministic hypothesis (MDH) states that high recombination rates are maintained because the breaking up of linkage disequilibria generated by negative epistasis enables more efficient purging of deleterious mutations. However, recent theoretical and experimental work challenges the MDH. Experimental evidence suggests that negative epistasis, required by the MDH, is relatively uncommon. On the theoretical side, population genetic models suggest that, compared with the combined effects of drift and selection, epistasis generates a negligible amount of linkage disequilibria. Here, we assess these criticisms and discuss to what extent they invalidate the MDH as an explanation for the evolution of recombination.}, Year = {2007} } @article{g.686, Author = {Takahata, Naoyuki}, Title = {Molecular Clock: An Anti-neo-Darwinian Legacy}, Journal = {Genetics}, Volume = {176}, Number = {1}, Pages = {1-6}, Note = {g.686}, Year = {2007} } @article{g.687, Author = {McClurg, Phillip and Janes, Jeff and Wu, Chunlei and Delano, David L. and Walker, John R. and Batalov, Serge and Takahashi, Joseph S. and Shimomura, Kazuhiro and Kohsaka, Akira and Bass, Joseph and Wiltshire, Tim and Su, Andrew I.}, Title = {Genomewide Association Analysis in Diverse Inbred Mice: Power and Population Structure}, Journal = {Genetics}, Volume = {176}, Number = {1}, Pages = {675-683}, Note = {g.687}, Abstract = {The discovery of quantitative trait loci (QTL) in model organisms has relied heavily on the ability to perform controlled breeding to generate genotypic and phenotypic diversity. Recently, we and others have demonstrated the use of an existing set of diverse inbred mice (referred to here as the mouse diversity panel, MDP) as a QTL mapping population. The use of the MDP population has many advantages relative to traditional F2 mapping populations, including increased phenotypic diversity, a higher recombination frequency, and the ability to collect genotype and phenotype data in community databases. However, these methods are complicated by population structure inherent in the MDP and the lack of an analytical framework to assess statistical power. To address these issues, we measured gene expression levels in hypothalamus across the MDP. We then mapped these phenotypes as quantitative traits with our association algorithm, resulting in a large set of exp