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While studying c-Myc protein expression in several Burkitt lymphoma cell lines and in lymph nodes from a mouse model bearing a translocated

The mutation T3811 → G3811 (TG3811) discovered in the myostatin gene of the Blonde d’Aquitaine breed is suspected of contributing to the outstanding muscularity of this breed. An experiment was designed to estimate the effect of this mutation in an F2 and back-cross Blonde d’Aquitaine × Holstein population. By genotyping all known mutations in the myostatin gene, it was ensured that the TG3811 mutation was indeed the only known mutation segregating in this population. Fifty-six calves (43 F2, 13 back-cross) were intensively fattened and slaughtered at 24.0 ± 1.4 wk of age. The effects of the mutation were estimated by comparing the calves with the [T/T] (n = 18), [T/G] (n = 30), and [G/G] (n = 8) genotypes. Highly significant substitution effects (P < 0.001), above + 1.2 phenotypic SD, were shown on carcass yield and muscularity scores. Birth weight (P < 0.001) was positively affected by the mutation (+0.8 SD) but not growth rate (P = 0.97), while carcass length (P = 0.03), and fatness (P ≤ 0.03) were negatively affected (–0.5 to –0.7 SD). The characteristics of the Triceps brachii muscle were affected by the mutation (P < 0.001), with lower ICDH activity (oxidative) and a higher proportion of myosin type 2X muscle fibers (fast twitch). The effects of the TG3811 mutation were similar to those of other known myostatin mutations, although the Blonde d’Aquitaine animals, which are predominantly [G/G] homozygous, do not exhibit extreme double muscling.

The agouti locus encodes the agouti signalling protein (ASIP) which is involved in determining the switch from eumelanin to pheomelanin synthesis in melanocytes. In the domestic rabbit (Oryctolagus cuniculus) early studies indicated three alleles at this locus: A, light-bellied agouti (wild type); at, black and tan; a, black nonagouti. We characterized the rabbit ASIP gene and identified the causative mutation (an insertion in exon 2) of the black nonagouti allele whose frequency was evaluated in 31 breeds. Phylogenetic analysis of ASIP sequences from Oryctolagus and 9 other species of the family Leporidae placed Oryctolagus as sister species to Pentalagus and Bunolagus. Transcription analysis in wild type agouti rabbits revealed the presence of two major transcripts with different 5′-untranslated regions having ventral or dorsal skin specific expression. ASIP gene transcripts were also detected in all examined rabbit tissues distinguishing the rabbit expression pattern from what was observed in wild type mice.

In mammals, male fertility is a quantitative feature determined by numerous genes. Until now, several wide chromosomal regions involved in fertility have been defined by genetic mapping approaches; unfortunately, the underlying genes are very difficult to identify. Here, 53 interspecific recombinant congenic mouse strains (IRCSs) bearing 1–2% SEG/Pas (Mus spretus) genomic fragments disseminated in a C57Bl/6J (Mus domesticus) background were used to systematically analyze male fertility parameters. One of the most prominent advantages of this model is the possibility of analyzing stable phenotypes in living animals. Here, we demonstrate the possibility in one-step fine mapping for several fertility traits. Focusing on strains harboring a unique spretus fragment, we could unambiguously localize two testis and one prostate weight-regulating QTL (Ltw1, Ltw2, and Lpw1), four QTL controlling the sperm nucleus shape (Sh1, Sh2, Sh3, and Sh4), and one QTL influencing sperm survival (Dss1). In several cases, the spretus DNA fragment was small enough to propose sound candidates. For instance, Spata1, Capza, and Tuba7 are very strong candidates for influencing the shape of the sperm head. Identifying new genes implied in mammalian fertility pathways is a necessary prerequisite for clarifying their molecular grounds and for proposing diagnostic tools for masculine infertilities.

International audience

Myostatin (MSTN), a negative regulator of skeletal muscle development in mammals, represents a key target for genetic investigations in meat-producing animals, with mutations responsible for increased skeletal-muscle mass currently described in several livestock species. Dromedary camels play a major economic role as suppliers of meat for human consumption across several countries. Notwithstanding, a comprehensive characterization of the sequence variability at the Camelus dromedarius MSTN locus was still lacking. Here we present the first extensive sequence and polymorphism analysis of the MSTN gene in the Camelus dromedarius species. Out of more than 3.6 kb of nucleotide sequence screened on 22 animals from 3 different Northern African regions, only 3 variant sites in the first intron were detected. The low observed diversity may reflect the evolutionary history of the species, likely developed as domesticates from a low variable wild ancestor population. Sequence identity among Camelus dromedarius and other Cetartiodactyla highlighted a tree topology consistent with previous reports of a closer relationship between Tylopoda and Suiformes. A close similarity between C. ferus and Camelus dromedarius was observed within Tylopoda. A markedly higher sequence identity between Camelus dromedarius and the other vertebrate species was observed at the MSTN locus compared to other genes, thus confirming it as a highly conserved target across mammals.

Myostatin is essential for proper regulation of myogenesis, and inactivation of Myostatin results in muscle hypertrophy. Here, we identified an unexpected mutation in the myostatin gene which is almost fixed in Blonde d'Aquitaine cattle. In skeletal muscle, the mutant allele was highly expressed leading to an abnormal transcript consisting of a 41-bp inclusion and premature termination codons and to residual levels of a correctly spliced transcript. This expression pattern, caused by a leaky intronic mutation with regard to spliceosome activity and its apparent stability with regard to surveillance mechanisms, could contribute to the moderate muscle hypertrophy in this cattle breed. This finding is of importance for genetic counseling for meat quantity and quality in livestock production and possibly to manipulate myostatin pre-mRNA in human muscle diseases.

To investigate the synthesis of alpha2-fucosylated epitopes in the bovine species, we have characterized cDNAs from various tissues. We found three distinct alpha2-fucosyltransferase genes, named bovine fut1, fut2, and sec1 which are homologous to human FUT1, FUT2, and Sec1 genes, respectively. Their open reading frames (ORF) encode polypeptides of 360 (bovine H), 344 (bovine Se), and 368 (bovine Sec1) amino acids, respectively. These enzymes transfer fucose in alpha1,2 linkage to ganglioside GM(1)and galacto- N -biose, but not to the phenyl-beta-D-galactoside, type 1 or type 2 acceptors, suggesting that their substrate specificity is different and more restricted than the other cloned mammalian alpha2-fucosyltransferases. Southern blot analyses detected four related alpha2-fucosyltransferase sequences in the bovine genome while only three have been described in other species. The supernumerary entity seems to be related to the alpha2-fucosyltransferase activity which can also use type 1 and phenyl-beta-D-galactoside substrate acceptors. It was exclusively found in bovine intestinal tract. Our results show that, at least in one mammalian species, four alpha2-fucosyltransferases are present, three adding a fucose on alpha1,2 linkage on type 3/4 acceptor (Galbeta1-3GalNAc) and another able to transfer also fucose on phenyl-beta-D-galactoside and type 1 (Galbeta1-3GlcNAc) acceptors. The phylogenetic tree of the enzymes homologous to those encoded by the bovine fut1, fut2, and sec1 genes revealed two main families, one containing all the H-like proteins and the second containing all the Se-like and Sec1-like proteins. The Sec1-like family had a higher evolutionary rate than the Se-like family.

Only one bovine gene, corresponding to the human cluster of genes FUT3-FUT5-FUT6, was found by Southern blot analysis. The cognate bovine alpha(1,3)-fucosyltransferase shares 67.3, 69.0, and 69.3% amino acid sequence identities with human FUC-T3, FUC-T5, and FUC-T6 enzymes, respectively. As revealed by protein sequence alignment, potential sites for asparagine-linked glycosylation and conserved cysteines, the bovine enzyme is an intermediate between FUC-T3, FUC-T5, and FUC-T6 human enzymes. Transfected into COS-7 cells, the bovine gene induced the synthesis of an alpha(1, 3)-fucosyltransferase enzyme with type 2 substrate acceptor pattern specificity and induced expression of fucosylated type 2 epitopes (Lex and sialyl-Lex), but not of type 1 structures (Lea or sialyl-Lea), suggesting that it has an acceptor specificity similar to the human plasma FUC-T6. However, no enzyme activity was detected in bovine plasma. Gene transcripts are detected on tissues such as bovine liver, kidney, lung, and brain. The type 2 sialyl-Lex epitope was found in renal macula densa and biliary ducts, and Lex and Ley epitopes were detected on the brush border of epithelial cells of small and large intestine, suggesting a tissue distribution closer to human FUC-T3, but fucosylated type 1 structures (Lea, Leb, or sialyl-Lea) were not detected at all in any bovine tissue. Analysis of genetic distances on a combined phylogenetic tree of fucosyltransferase genes suggests that the bovine gene is the orthologous homologue of the ancestor of human genes constituting the present FUT3-FUT5-FUT6 cluster.

Chantier qualité GA; International audience; Differential expression of the ASIP gene and its interaction with MC1R have provided basic insight into pigment-type switching in mammals. Here, we report the characterization of a specific red-haired skin transcript and a specific black-haired skin transcript in the ASIP gene in the black-and-tan Doberman Pinscher. It is also shown that the brindle-haired skin of the Boxer exhibits a deregulated expression resulting in various 5'-untranslated exons. Comparative sequence analysis revealed a short interspersed element and a poly(A) stretch inserted within the promoter region of the ASIP in the Boxer. Genotyping studies have shown that both insertions are also present in brindle and fawn animals of the Boxer and Great Dane breeds. Furthermore, we genotyped MC1R and K loci for their known variants that affect coat color in dogs. As expected, all animals were homozygotes (E(M) /E(M) ) for the mask mutation, and fawn animals were k(y) /k(y) . Unexpectedly, we found that all brindle animals were heterozygotes k(B) /k(y) . Our results suggest that differential expression of ASIP determine pigment-type switching in a MC1R and K allele-dependent manner in dogs.

[EN] Classical genetic studies have identified different coat colour loci in rabbit and comparative analyses have established corresponding loci across species. In particular, the rabbit dilute locus is determined by a recessive coat colour mutation that modifies the basic colours influenced by the agouti and extension mutations. In mice, similar phenotypic effects are determined by a similarly named locus. This locus encodes the myosin VA (Myo5a) gene, whose protein product is an unconventional myosin that plays an essential role in melanosome transport in the melanocytes. We selected the same gene as a strong candidate for explaining the dilute coat colour in rabbit. To this end, 1399 bp were re-sequenced, spanning 4 exons out of 41 exons and a portion of intronic regions of the rabbit MYO5A gene to identify polymorphisms that could be useful to confirm or exclude this gene as causative of the rabbit dilute locus. Nine polymorphisms were identified, one of which was used to follow the segregation of the blue and black colours in a Checkered Giant F1 family. The single nucleotide polymorphism (SNP) analysed did not co-segregate with the two colours. These results excluded the MYO5A gene as determinant of the dilute locus in rabbit. The two alleles of this SNP were also present in several other breeds with different coat colours, further indicating that this marker is not associated with the dilute mutation in rabbits. Other candidates should be investigated to identify the causative gene of this locus in rabbit., We thank several rabbit breeders and Associazione Nazionale Coniglicoltori Italiani (ANCI) for their collaboration in the sampling of biological materials. This work was supported by RFO and FAGenomicH project funds from the University of Bologna.

For several decades, tremendous advances in studying skin and hair pigmentation of mammals have been made using Mendelian genetics principles. A number of loci and their associated traits have been extensively examined, crossings performed, and phenotypes well documented. Continuously improving PCR techniques allowed the molecular cloning and sequencing of the first pigmentation genes at the end of the 20th century, a period followed by an intense effort to detect and describe polymorphisms in the coding regions and correlate allelic combinations with the observed melanogenic phenotypes. However, a number of phenotypes and biological events could not be elucidated solely by analysis of the coding regions of genes. Messenger RNA isolation, characterization and quantification techniques allowed groups to move ahead and investigate molecular mechanisms whose secrets lay within the noncoding regions of pigmentation genes transcripts such as MC1R, ASIP, or Mitf. The untranslated elements contain specific nucleotidic sequences and structures that dramatically influence the mRNA half-life and processing thus impacting protein translation and melanin production. As we are progressively uncovering the complex processes regulating melanocyte biology, unraveling complete mRNA structures and understanding mechanisms beyond coding regions has become critical.

Background In the domestic rabbit (Oryctolagus cuniculus), classical genetic studies have identified five alleles at the Extension locus: ED (dominant black), ES (steel, weaker version of ED), E (wild type, normal extension of black), eJ(Japanese brindling, mosaic distribution of black and yellow) and e (non-extension of black, yellow/red with white belly). Sequencing almost the complete coding sequence (CDS) of the rabbit MC1R gene, we recently identified two in-frame deletions associated with dominant black (c.280_285del6; alleles ED or ES) and recessive red (c.304_333del30; allele e) coat colours. It remained to characterize the eJallele whose phenotypic effect is similar to the Orange and Sex-linked yellow loci of cat and Syrian hamster. Results We sequenced the whole CDS in 25 rabbits of different coat colours including 10 Japanese and 10 Rhinelander (tricolour) rabbits and identified another 6 bp-in frame deletion flanked by a G > A transition in 5' (c.[124G>A;125_130del6]) that was present in all animals with Japanese brindling coat colour and pattern. These mutations eliminate two amino acids in the first transmembrane domain and, in addition, cause an amino acid substitution at position 44 of the wild type sequence. Genotyping 371 rabbits of 31 breeds with different coat colour this allele (eJ) was present in homozygous state in Japanese, Rhinelander and Dutch tricolour rabbits only (except one albino rabbit). Rabbits with eJ/eJ genotype were non fixed at the non-agouti mutation we previously identified in the ASIP gene. Segregation in F1 and F2 families confirmed the order of dominance already determined by classical genetic experiments with a possible dose effect evident comparing eJ/eJ and eJ/e animals. MC1R mRNA was expressed in black hair skin regions only. Conclusions The c.[124A;125_130del6] allele may be responsible for a MC1R variant determining eumelanin production in the black areas. However, the mechanism determining the presence of both red and black hairs in the same animal seems more complex. Expression analyses of the c.[124A;125_130del6] allele suggest that MC1R transcription may be regulated epigenetically in rabbits with the Japanese brindling phenotype. Further studies are needed to clarify this issue.

The ERG12 gene of Saccharomyces cerevisiae has been cloned by complementation of an erg12-1 mutation affecting mevalonate kinase. From the 2.8-kb insert isolated, the functional gene has been localized on a DNA fragment of 2.1 kb. The mRNA is 1.45 kb long. Gene disruption shows that the ERG12 gene is essential in yeast, both for spore germination and vegetative growth.

Mammalian pigmentation is controlled by the concerted action of Tyr, Tyrp1 and Dct producing eumelanin and/or pheomelanin in melanocytes. The ratio of these two pigments is determined by the agonist alpha-melanocyte stimulating hormone and the antagonist Agouti protein acting on the Mc1r. Here we show that the Agouti gene is over-expressed in Normande breed compared with Prim'Holstein breed. The Normande cattle have a characteristic coat color phenotype with a variable presence of black (eumelanin) hair over a red/brown background. We have found a previously undescribed full-length L1-BT element inserted in the 5'-genomic sequence of the Agouti gene in Normande cattle which promotes the over-expression of alternative transcripts. The variable expression of the alternative transcript directed by the long interspersed nuclear element promoter may be the origin of the brindle coat color pattern of the Normande breed. This new bovine Agouti allele isolated in Normande breed has been named Abr. Finally, as ectopic over-expression of Agouti in Ay mice is responsible for the obesity syndrome, we discuss the possible consequences of Abr for meat and milk production in cattle.

Background In chickens, three mutant alleles have been reported at the C locus, including the albino mutation, and the recessive white mutation, which is characterized by white plumage and pigmented eyes. The albino mutation was found to be a 6 bp deletion in the tyrosinase (TYR) gene. The present work describes an approach to identify the structural rearrangement in the TYR gene associated with the recessive white mutation. Results Molecular analysis of the chicken TYR gene has revealed a major structural difference (Restriction Fragment Length Polymorphism, RFLP) in the genomic DNA of the recessive white chicken. A major size difference of 7.7 kb was found in intron 4 of the TYR gene by long-range PCR. Molecular cloning and sequencing results showed the insertion of a complete avian retroviral sequence of the Avian Leukosis Virus (ALV) family. Several aberrant transcripts of the tyrosinase gene were found in 10 week old recessive white chickens but not in the homozygous wild type colored chicken. We established a rapid genotyping diagnostic test based on the discovery of this retroviral insertion. It shows that all homozygous carriers of this insertion had a white plumage in various chicken strains. Furthermore, it was possible to distinguish heterozygous carriers from homozygous normal chickens in a segregating line. Conclusion In this study, we conclude that the insertion of a complete avian retroviral sequence in intron 4 of the tyrosinase gene is diagnostic of the recessive white mutation in chickens. This insertion causes aberrant transcripts lacking exon 5, and we propose that this insertion is the causal mutation for the recessive white allele in the chicken.

In wild-type mice, it is well known that Agouti is only expressed in skin where it controls the banded-hair phenotype. As a first step to investigate the physiological role of Agouti in cattle, we isolated the corresponding gene and studied its expression pattern. We found no evidence of coding-region sequence variation within and between eight breeds representing a large panel of coat colour phenotypes. We detected by northern hybridization two Agouti mRNA isoforms in brain, heart, lung, liver, kidney, spleen and a third in skin. We characterized the full-length Agouti transcript in skin and isolated the 5'UTR of two mRNAs expressed in the other tissues. The three mRNAs have the same coding region but differ by their 5' untranslated regions. Upstream regulatory sequences display two alternative promoters involved with the broad expression in tissues other than skin. Interestingly, these sequences are highly homologous to upstream sequences of the orthologous human (76-85% identity) and pig (82-86% identity) ASIP genes. In addition to its potential role in pigmentation (as seen in mice), we suggest that bovine Agouti could be involved in various physiological functions. Furthermore, the significant homology between cattle, pig and human regulatory sequences indicate that these orthologous genes are regulated alike. Lastly, since the 5'UTR of many eukaryotic mRNAs are physiologically relevant, their impact on bovine Agouti mRNA performance is discussed.

In this study we report the isolation of full-length cDNAs and the expression patterns of TYR, TYRP1 and DCT in four e/e cattle breeds exhibiting different pheomelanic coat colours ranging from reddish brown to creamy white phenotypes. Predicted proteins encoded by bovine TYR, TYRP1 and DCT display high levels of homology and contain all characteristic domains shared between their mouse and human counterparts. The full expression of these three genes is observed in melanocytes of black areas of E(D)/E(D) Prim'Holstein's animals. On the other hand, e/e melanocytes of animals belonging to the Blonde d'Aquitaine (blond), Limousine (red) and Salers (reddish brown) breeds present different levels of down-regulated TYR and DCT expression and a complete repression of TYRP1. Surprisingly, e/e melanocytes of animals belonging to the Charolais breed (creamy white) present an inverse relationship between TYR, TYRP1 and DCT expression and its lower melanogenic activity. The sum of these results shows that the dilution of the coat colour in French cattle breeds is not correlated with a transcription level of TYR family genes. Other possible modifier loci are suggested.

International audience; The seven transmembrane domain melanocortin-1 receptor (Mc1r) encoded by the coat color extension gene ($E$) plays a key role in the signaling pathway of melanin synthesis. Upon the binding of agonist (melanocortin hormone, $\alpha$-MSH) or antagonist (Agouti protein) ligands, the melanosomal synthesis of eumelanin and/or phaeomelanin pigments is stimulated or inhibited, respectively. Different alleles of the extension gene were cloned from unrelated animals belonging to French cattle breeds and sequenced. The wild type $E$ allele was mainly present in Normande cattle, the dominant $E^{\rm D}$ allele in animals with black color (i.e. Holstein), whereas the recessive $e$ allele was identified in homozygous animals exhibiting a more or less strong red coat color (Blonde d'Aquitaine, Charolaise, Limousine and Salers). A new allele, named $E^1$, was found in either homozygous ($E^1/E^1$) or heterozygous ($E^1/E$) individuals in Aubrac and Gasconne breeds. This allele displayed a 4 amino acid duplication (12 nucleotides) located within the third cytoplasmic loop of the receptor, a region known to interact with G proteins. A first genotyping assay of the main French cattle breeds is described based on these four extension alleles.; Premier essai de génotypage de races bovines françaises basé sur un nouvel allèle du gène extension codant pour le récepteur 1 aux mélanocortines (Mc1r). Le récepteur 1 aux mélanocortines (Mc1r), codé par le gène extension, présente sept domaines transmembranaires et joue un rôle clé dans la voie de signalisation de la biosynthèse des mélanines. Lors de la liaison de l'agoniste (hormone "mélanotrope " $\alpha$-MSH) ou de l'antagoniste (la protéine Agouti), la synthèse mélanosomale des pigments eumélaniques (brun / noir) et/ou phaéomélaniques (jaune / rouge) est respectivement stimulée ou inhibée. À partir d'animaux non apparentés provenant de bovins de races françaises, différents allèles ont été clonés et séquencés. L'allèle sauvage $E$ est présent chez la Normande, l'allèle $E^{\rm D}$ chez les bovins à robe noire (par exemple Holstein), alors que l'allèle récessif $e$ a été mis en évidence chez des animaux homozygotes présentant des couleurs de robe basées sur une présence plus ou moins prononcée de pigments phaéomélaniques (Blonde d'Aquitaine, Charolaise, Limousine et Salers). Un nouvel allèle $E^1$ a été découvert à la fois chez des individus homozygotes $E^1/E^1$ ou hétérozygotes $E^1/E$ des races Aubrac et Gasconne. Il possède une duplication de quatre acides aminés (12 nucléotides) localisée dans la troisième boucle cytoplasmique, région du récepteur connue comme interagissant avec les protéines G. Sur la base de ces quatre allèles du gène extension, un premier test de génotypage des principales races bovines françaises est décrit.

Les marqueurs génétiques, qu’ils soient anonymes (microsatellites) ou responsables de phénotypes (gènes de la coloration, par exemple), constituent des outils efficaces pour identifier les individus ou les populations (races) et pour assurer leur traçabilité. On montre ici l’intérêt du gène extension pour le génotypage des bovins.

In this study, we report the first isolation and characterization of a bovine sialyltransferase gene. Bovine cDNAs prepared from different tissues contain an open-reading frame encoding a 405 amino acid sequence showing 83%, 75%, and 60% identity with human, murine, and chicken ST6Gal I (beta-galactoside alpha2,6-sialyltransferase) sequences, respectively. When transfected into COS-7 cells, a recombinant enzyme was obtained which catalyzed the in vitro alpha2, 6-sialylation of LacNAc (NeuAcalpha2-6Galbeta1-4GlcNAc) and LacdiNAc (NeuAcalpha2-6GalNAcbeta1-4GlcNAc) acceptor substrates. The K (m) values were 2.8 and 6.9 mM, respectively. Different relative efficiencies (Vmax/Km) for the two precursors (36 for LacNAc and 4.3 for LacdiNAc) were observed. Bovine ST6Gal I gene consists of four 5'-untranslated exons E(-2) to E(1), and five coding exons from E(2) to E(6). This later carries a 3'-untranslated region of 2. 7 kb. Gene sequence spans at least 80 kb of genomic DNA. Two processed pseudogenes have been identified. They are 94.3 and 95.6% similar to the bovine cDNA, respectively. Three families of mRNA isoforms were isolated. They differed by their 5'-untranslated regions and could be generated by three tissue-specific promoters. Family 1 is made up of exons E(-2) and E(1) to E(6), family 2 of exons E(-1) to E(6), and family 3 of exons E(1) to E(6). Tissular distribution of transcript families appears noticeably different than those described in human and rat.

The futb gene, which encodes the first bovine alpha 3-fucosyltransferase described, consists of five exons (a, b, c, d, and e), the first four being located upstream of the coding exon e. Together with the four introns (i1, i2, i3, and i4) they span a DNA genomic sequence of about 10 kb. futb is expressed as four tissue-specific transcripts differing by their 5'-untranslated (5'-UT) regions, but only one transcript includes all exons, while the other three begin at internal sites of exon c. A short sequence of the latter is homologous to distinct 5'-UT exons of FUT6 (alpha 3-fucosylation) and FUT3 (alpha 4-fucosylation), two human genes whose coding sequences are homologous to coding exon e of futb. Upstream and downstream, the exon c intronic regions of the bovine gene are homologous to 5'-UT exons of human FUT3 (exon B) and FUT6 (exons A, B, and C). Thus, exon c appears to be the most ancestral 5'-UT exon known among these alpha 3-fucosyltransferase genes. Interestingly, distribution of short interspersed nuclear elements in the i3 intron adjacent to exon c reveals that two repeat sequences are joined to form a reverse-transcriptase-like encoding sequence highly homologous to an open reading frame located at the 3' end of the bovine gamma globin gene. This organization suggests that duplication events that have generated the primate FUT3-FUT5-FUT6 cluster might have occurred through a long-interspersed-nuclear-element-based mechanism of unequal crossing over, as described for the globin cluster. Complete organization of the bovine futb gene reveals that in addition to duplication events, the lineage leading to primate FUT3, FUT5, and FUT6 genes results from rearrangements of intronic sequences which have created for each new gene specific regulatory 5'-UT exonic sequences.

The testis transcriptome of mouse strains containing homozygous segments of Mus spretus origin in a Mus musculus background was analyzed., Background Accumulating evidence points to the mosaic nature of the mouse genome. However, little is known about the way the introgressed segments are regulated within the context of the recipient genetic background. To address this question, we have screened the testis transcriptome of interspecific recombinant congenic mouse strains (IRCSs) containing segments of Mus spretus origin at a homozygous state in a Mus musculus background. Results Most genes (75%) were not transcriptionally modified either in the IRCSs or in the parent M. spretus mice, compared to M. musculus. The expression levels of most of the remaining transcripts were 'dictated' by either M. musculus transcription factors ('trans-driven'; 20%), or M. spretus cis-acting elements ('cis-driven'; 4%). Finally, 1% of transcripts were dysregulated following a cis-trans mismatch. We observed a higher sequence divergence between M. spretus and M. musculus promoters of strongly dysregulated genes than in promoters of similarly expressed genes. Conclusion Our study indicates that it is possible to classify the molecular events leading to expressional alterations when a homozygous graft of foreign genome segments is made in an interspecific host genome. The inadequacy of transcription factors of this host genome to recognize the foreign targets was clearly the major path leading to dysregulation.

A stable GS115 Pichia pastoris recombinant strain was constructed to secrete a truncated form of the human alpha(1,3/4) fucosyltransferase (amino acids 45-361). Enzyme production resulted from a secretory pathway based on the pre-pro- alpha mating factor signal sequence of the yeast Saccharomyces cerevisiae . Following its transit through the Golgi apparatus, the enzyme accumulated in the periplasmic space before its release in the culture broth (about 30 mg/l). Cell-enclosed enzyme ( approximately 0.16%) proved to be fairly stable for many freezing and thawing cycles and could be used several times as an immobilized catalyst. Soluble enzyme (>99.8%) representing the main protein of the culture broth (10%) has been characterized by Western-blotting, substrate specificities and kinetic parameters. The two forms (cell-enclosed and soluble) of recombinant enzyme may be used for in vitro synthesis of Lewisadeterminants.

La myostatine, un membre de la superfamille TGF- β ( Transforming growth factor-beta ) est un régulateur négatif de la croissance et du développe ment musculaire. Depuis sa découverte en 1997, le gène myostatine a été intensément étudié de par ses applications potentielles bénéfiques dans les domai nes de l’élevage et médical. Les mutations pertes de fonctions qui affectent la fonction de la myostatine ou celles qui réduisent son expression conduisent à une hypertrophie musculaire , alors que celle qui engendre une surexpression de la myostatine engendre une réducti on importante de la masse musculaire. Nous avons identifié un allèle inattendu du gène myostatine qui est responsable de l’augmentation de la masse musculaire chez la race bovine Bonde d’Aquitaine. Dans le muscle, cet allèle est fortement exprimé conduisant à la fo rmation d’un transcrit myostatine aberrant avec un codon STOP prématuré de la traduction en plus d’ une quantité résiduelle correctement épissé. Ce profil d’expression qui résulte d’une mutation i ntronique leaky par rapport à l’activité du splicéosome, contribue à l’établissement d’une hype rtrophie modérée qui caractérise la race bovine Blonde d’Aquitaine. Cette découverte est imp ortante dans le domaine de la génétique de l’élevage et potentiellement dans le domaine médica l. Elle permet de concilier à la fois le bien être de l’animal et la production qualitative et qu antitative de la viande. Par ailleurs, le mécanisme est susceptible d’être exploité pour une possible application pour soigner certaines maladies musculaires humaines via une manipulation appropriée des pré-ARNm du gène myostatine ., Myostatin, a member of the TGF- β (Transforming growth factor-beta) superfamily, fun ctions as a negative regulator of skeletal muscle development and growth. Since its discovery in mice in 1997, the myostatin gene has been extensively investigated considering the potential benefits of enhancing mus cle growth in clinical and agricultural settings. Loss-of-function mutations which impair m yostatin function or those which knockdown myostatin gene expression, result in muscle hypertrophy ofte n referred to as ‘‘double-muscling’’ whereas myostatin overexpression induces profound m uscle loss. Here, we identified an unexpected mutation in the myostatin gene that is responsible for increasing muscle mass in Blonde d'Aquitaine cattle breed. In skeletal muscle, the mutant allele was highly expressed leading to an abnormal transcr ipt with a premature termination codon and to residual levels of a correctly spliced transcrip t. This expression pattern, caused by a leaky intronic mutation with regard to spliceosome, could contribute to the moderate muscle hypertrophy in this cattle breed. This finding is o f importance for genetic counseling for meat quantity and quality in livestock production and po ssibly to manipulate myostatin pre-mRNA in human muscle diseases.