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International audience; Mitochondrial DNA (mtDNA) differences between humpback whales on different feeding groundscan reflect the cultural transmission of migration destinations over generations, and thereforerepresent one of the very few cases of gene-culture coevolution identified in the animal kingdom.In Russian Pacific waters, photo-identification (photo-ID) studies have shown minimal interchangebetween whales feeding off the Commander Islands and those feeding in the Karaginsky Gulf,regions that are separated by only 500 km and have previously been lumped together as a singleRussian feeding ground. Here, we assessed whether genetic differentiation exists between these2 groups of humpback whales. We discovered a strong mtDNA differentiation between the 2feeding sites (FST = 0.18, ΦST = 0.14, P < 0.001). In contrast, nuclear DNA (nuDNA) polymorphisms,determined at 8 microsatellite loci, did not reveal any differentiation. Comparing our mtDNA resultswith those from a previous ocean-basin study reinforced the differences between the 2 feedingsites. Humpback whales from the Commanders appeared most similar to those of the westernGulf of Alaska and the Aleutian feeding grounds, whereas Karaginsky differed from all other NorthPacific feeding grounds. Comparison to breeding grounds suggests mixed origins for the 2 feedingsites; there are likely connections between Karaginsky and the Philippines and to a lesser extentto Okinawa, Japan, whereas the Commanders are linked to the Mexican breeding grounds. ThemtDNA differentiation between the Commander Islands and Karaginsky Gulf suggests a case ofgene-culture coevolution, correlated to fidelity to a specific feeding site within a particular feedingground. From a conservation perspective, our findings emphasize the importance of consideringthese 2 feeding sites as separate management units.

International audience; Background. Susceptibility to infection is in part genetically driven, and C57BL/6 mice resist various pathogens through the proinflammatory response of their M1 macrophages (MPs). However, they are susceptible to plague. It has been reported elsewhere that Mus spretus SEG mice resist plague and develop an immune response characterized by a strong recruitment of MPs. Methods. The responses of C57BL/6 and SEG MPs exposed to Yersinia pestis in vitro were examined. Results. SEG MPs exhibit a stronger bactericidal activity with higher nitric oxide production, a more proinflammatory polarized cytokine response, and a higher resistance to Y. pestis-induced apoptosis. This response was not specific to Y. pestis and involved a reduced sensitivity to M2 polarization/signal transducer and activator of transcription 6 activation and inhibition of caspase 8. The enhanced M1 profile was inducible in C57BL/6 MPs in vitro, and when transferred to susceptible C57BL/6 mice, these MPs significantly increased survival of bubonic plague. Conclusions. MPs can develop an enhanced functional profile beyond the prototypic M1, characterized by an even more potent proinflammatory response coordinated with resistance to killing. This programming plays a key role in the plague-resistance phenotype and may be similarly significant in other highly lethal infections, suggesting that orienting the MP response may represent a new therapeutic approach.

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Assessing the movement patterns and key habitat features of breeding humpback whales is a prerequisite for the conservation management of this philopatric species. To investigate the interactions between humpback whale movements and environmental conditions off Madagascar, we deployed 25 satellite tags in the northeast and southwest coast of Madagascar. For each recorded position, we collated estimates of environmental variables and computed two behavioural metrics: behavioural state of ‘transiting’ (consistent/directional) versus ‘localized’ (variable/non-directional), and active swimming speed (i.e. speed relative to the current). On coastal habitats (i.e. bathymetry aconcentrations. Active swimming speed accounts for a large proportion of observed movement speed; however, breeding humpback whales probably exploit prevailing ocean currents to maximize displacement. This study provides evidence that coastal areas, generally subject to strong human pressure, remain the core habitat of humpback whales off Madagascar. Our results expand the knowledge of humpback whale habitat use in oceanic habitat and response to variability of environmental factors such as oceanic current and chlorophyll level.

There are two recognized species in the genus Berardius, Baird’s and Arnoux’s beaked whales. In Japan, whalers have traditionally recognized two forms of Baird’s beaked whales, the common “slate-gray” form and a smaller, rare “black” form. Previous comparison of mtDNA control region sequences from three black specimens to gray specimens around Japan indicated that the two forms comprise different stocks and potentially different species. We have expanded sampling to include control region haplotypes of 178 Baird’s beaked whales from across their range in the North Pacific. We identified five additional specimens of the black form from the Aleutian Islands and Bering Sea, for a total of eight “black” specimens. The divergence between mtDNA haplotypes of the black and gray forms of Baird’s beaked whale was greater than their divergence from the congeneric Arnoux’s beaked whale found in the Southern Ocean, and similar to that observed among other congeneric beaked whale species. Taken together, genetic evidence from specimens in Japan and across the North Pacific, combined with evidence of smaller adult body size, indicate presence of an unnamed species of Berardius in the North Pacific.

In recent decades, grey seals (Halichoerus grypus) and harbour porpoises (Phocoena phocoena) have become more numerous along the coasts of Brittany in northwestern France. Their interactions with fisheries are of increasing concern and diet analyses are becoming a requirement to determine the actual overlap between species targeted by fisheries and marine mammal prey. However, as only a few stranded or by-caught animals are available to investigate the diet of these top predators, it is necessary to optimize the results obtained from each animal sampled by increasing the rate of prey species determination in stomach contents. We used a combined analysis of stomach contents, based on prey hard remains and, in parallel, a simple DNA barcoding approach to identify the soft remains. Seven grey seal stomachs and three harbour porpoise stomachs have been analysed. The combined approach, making use of visual observation as well as DNA analysis, increased the identification of prey items by around 32% for...

International audience; The constantly growing amount ofWeb content and the success of the SocialWeb lead to increasing needs for Web archiving. These needs go beyond the pure preservationo of Web pages. Web archives are turning into “community memories” that aim at building a better understanding of the public view on, e.g., celebrities, court decisions and other events. Due to the size of the Web, the traditional “collect-all” strategy is in many cases not the best method to build Web archives. In this paper, we present the ARCOMEM (From Future Internet 2014, 6 689 Collect-All Archives to Community Memories) architecture and implementation that uses semantic information, such as entities, topics and events, complemented with information from the Social Web to guide a novel Web crawler. The resulting archives are automatically enriched with semantic meta-information to ease the access and allow retrieval based on conditions that involve high-level concepts.

In the last ten years, 14 species of cetaceans and five species of pinnipeds stranded along the Atlantic coast of Brittany in the North West of France. All species included, an average of 150 animals strand each year in this area. Based on reports from the stranding network operating along this coast, the most common stranding events comprise six cetacean species (Delphinus delphis, Tursiops truncatus, Stenella coeruleoalba, Globicephala melas, Grampus griseus, Phocoena phocoena) and one pinniped species (Halichoerus grypus). Rare stranding events include deep-diving or exotic species, such as arctic seals. In this study, our aim was to determine the potential contribution of DNA barcoding to the monitoring of marine mammal biodiversity as performed by the stranding network.We sequenced more than 500 bp of the 5’ end of the mitochondrial cox1 gene of 89 animals of 15 different species (12 cetaceans, and three pinnipeds). Except for members of the Delphininae, all species were unambiguously discriminated on the basis of their cox1 sequences. We then applied DNA barcoding to identify some “undetermined” samples. With again the exception of the Delphininae, this was successful using the BOLD identification engine. For samples of the Delphininae, we sequenced a portion of the mitochondrial control region (MCR), and using a non-metric multidimentional scaling plot and posterior probability calculations we were able to determine putatively each species. We then showed, in the case of the harbour porpoise, that cox1 polymorphisms, although being lower than MCR ones, could also be used to assess intraspecific variability. All these results show that the use of DNA barcoding in conjunction with a stranding network could clearly increase the accuracy of the monitoring of marine mammal biodiversity.

International audience; Recurrent spontaneous abortion (RSA) is defined as the loss of three or more consecutive pregnancies during the first trimester of embryonic intrauterine development. This kind of human infertility is frequent among the general population since it affects 1 to 5% of women. In half of the cases the etiology remains unelucidated. In the present study, we used interspecific recombinant congenic mouse strains (IRCS) in the aim to identify genes responsible for embryonic lethality. Applying a cartographic approach using a genotype/phenotype association, we identified a minimal QTL region, of about 6 Mb on chromosome 1, responsible for a high rate of embryonic death (,30%). Genetic analysis suggests that the observed phenotype is linked to uterine dysfunction. Transcriptomic analysis of the uterine tissue revealed a preferential deregulation of genes of this region compared to the rest of the genome. Some genes from the QTL region are associated with VEGF signaling, mTOR signaling and ubiquitine/proteasome-protein degradation pathways. This work may contribute to elucidate the molecular basis of a multifactorial and complex human disorder as RSA.

The harbour porpoise(Phocoena phocoena)is one of the common small cetaceans of European waters. This discreet and undemonstrative species is strongly represented throughout the cold waters of the northern hemisphere, and is the most abundant cetacean in the North Sea. In the last few years, some observations and studies indicate a shift of harbour porpoise distribution in European waters, from northern regions of the North Sea to the southern North Sea, English Channel and Celtic Sea. This shift may include a comeback around the coasts of France. Harbour porpoises inhabit shelf-waters and are often observed in shallow waters, conditions offered for instance by the coasts of Brittany in north-western France. We used opportunistic sightings, aerial survey and a ten-year strandings database to study the presence of harbour porpoises along the coasts of Brittany. Opportunistic sightings made by non-specialists did not confirm a strong presence of harbour porpoises along the Brittany coasts, most probably because of the undemonstrative behaviour of this cetacean. However, aerial survey and stranding analysis indicate that harbour porpoises have become natural inhabitants of the Brittany coasts once more: 68.6% of cetacean school sightings made during a 1578 km aerial survey of the Brittany coasts concerned harbour porpoises, with an encounter rate of 1.5 individuals per 100 km that peaked to 5.8 per 100 km to the top of the shallow waters of the south-western Western English Channel. The number of harbour porpoise strandings increased each year from 1997 to 2007, making a total of 135 along the coasts of Brittany. Other cetaceans did not show such an increase during the same period. Strandings of harbour porpoises were also characterized by an apparent increase as a proportion in relation to all the cetacean strandings during the months of September to January, by a marked impact of by-catch during winter, and by an almost total absence of stranded calves. The comeback of the harbour porpoise along Brittany coasts is clearly confirmed by our data, and a stable population seems to be established again along the coasts of Brittany. This tends to confirm the shift of the distribution of the species in certain European waters. Long term monitoring, diet and genetic studies are now planned for a better understanding of this shift, and for the effective implementation of a conservation plan.

The aim of this work was to study the in vitro effect of T-2 toxin on human monocyte differentiation into macrophages and dendritic cells. Cytotoxicity of T-2 toxin on monocytes, on monocytes in differentiation process into macrophages or dendritic cells, and on immature dendritic cells and macrophages was evaluated to determine IC50. Monocytes are more sensitive to T-2 toxin than to differentiate cells. IC50 were equal to 0.11 nM for monocyte, to 45 and 30 nM for monocyte during differentiation process for 24 and 48 h of incubation, respectively, to 38 and 20 nM for immature dendritic cells after 24 and 48 h of incubation, and to 22 and 20 nM for macrophages after 24 and 48 h of incubation. T-2 toxin effects on monocyte differentiation process into macrophages have been explored: according to phenotypic expressions (CD71, CD14, CD11a, CD80, CD86, HLA-DR and CD64), endocytic capacity, phagocytosis, burst respiratory activity and TNF-alpha secretion. In the presence of 10 nM of T-2 toxin (no cytotoxic concentration), CD71 expression is downregulated compared to control. Endocytosis and phagocytosis capacities are less effective as burst respiratory activity and TNF-alpha secretion. Monocyte differentiation process into dendritic cells in the presence of 10 nM T-2 toxin is also markedly disturbed. Expression of CD1a (specific dendritic cells marker) is downregulated while that of CD14 (specific monocyte marker) is upregulated. CD11a, CD80, CD86, HLA-DR and CD64 expressions did not change. These results show that T-2 toxin disturbs human monocytes differentiation process into macrophages and dendritic cells. These results could significantly contribute to immunosuppressive properties of this alimentary toxin.

Axonal degeneration represents one of the earliest pathological features in motor neuron diseases. We here studied the underlying molecular mechanisms in progressive motor neuronopathy (pmn) mice mutated in the tubulin-specific chaperone TBCE. We demonstrate that TBCE is a peripheral membrane-associated protein that accumulates at the Golgi apparatus. Inpmnmice, TBCE is destabilized and disappears from the Golgi apparatus of motor neurons, and microtubules are lost in distal axons. The axonal microtubule loss proceeds retrogradely in parallel with the axonal dying back process. These degenerative changes are inhibited in a dose-dependent manner by transgenic TBCE complementation that restores TBCE expression at the Golgi apparatus. In cultured motor neurons, thepmnmutation, interference RNA-mediated TBCE depletion, and brefeldin A-mediated Golgi disruption all compromise axonal tubulin routing. We conclude that motor axons critically depend on axonal tubulin routing from the Golgi apparatus, a process that involves TBCE and possibly other tubulin chaperones.

Patients with deficiency in ferrochelatase (FECH), the last enzyme of the heme biosynthetic pathway, experience a painful type of skin photosensitivity called erythropoietic protoporphyria (EPP), which is caused by the excessive production of protoporphyrin IX (PPIX) by erythrocytes. Controversial results have been reported regarding hematologic status and iron status of patients with EPP. We thoroughly explored these parameters in Fechm1Pas mutant mice of 3 different genetic backgrounds. FECH deficiency induced microcytic hypochromic anemia without ringed sideroblasts, little or no hemolysis, and no erythroid hyperplasia. Serum iron, ferritin, hepcidin mRNA, and Dcytb levels were normal. The homozygous Fechm1Pas mutant involved no tissue iron deficiency but showed a clear-cut redistribution of iron stores from peripheral tissues to the spleen, with a concomitant 2- to 3-fold increase in transferrin expression at the mRNA and the protein levels. Erythrocyte PPIX levels strongly correlated with serum transferrin levels. At all stages of differentiation in our study, transferrin receptor expression in bone marrow erythroid cells in Fechm1Pas was normal in mutant mice but not in patients with iron-deficiency anemia. Based on these observations, we suggest that oral iron therapy is not the therapy of choice for patients with EPP and that the PPIX–liver transferrin pathway plays a role in the orchestration of iron distribution between peripheral iron stores, the spleen, and the bone marrow.

Background: Helicobacter pylori infection is associated with gastric cancer. Study with the Big Blue mouse model has reported a mutagenic effect associated with the H. pylori infection, as a result in part of oxidative DNA damage. The present work investigates the consequences of a deficiency in the OGG1 DNA glycosylase, responsible for the excision of 8-oxo guanine, on the inflammatory and genotoxic host response to the infection. Materials and Methods: Big Blue Ogg1–/– C57BL/6 mice were orally inoculated with H. pylori strain SS1 or vehicle only, and sacrificed after 1, 3, or 6 months. The serologic response, histologic lesions, mutant frequency, and spectra of mutations were assessed in the stomach and compared to what observed in the wild-type (Wt) context. Results: Inflammatory lesions induced in the gastric mucosa of H. pylori-infected mice, corresponding to a moderate gastritis, were less severe in Ogg1–/– than in Wt Big Blue mice. Analysis of antimicrobial humoral immunity exhibited a lower IgG2a serum level (Th1 response) after 6 months of infection in Ogg1–/– than in the Wt mice. In these conditions, the H. pylori-SS1 infection in the Ogg1–/– mice did not induce a mutagenic effect at the gastric epithelial cells level, either after 3 or 6 months. Conclusions: The inactivation of the OGG1 DNA glycosylase in mouse leads to less severe inflammatory lesions and abolished the mutagenic effect at the gastric epithelial cells level, induced by the H. pylori infection. These data suggest for the OGG1deficiency a protective role against inflammation and genotoxicity associated to the H. pylori infection.

International audience; Erythropoietic protoporphyria (EPP) is an inherited disorder of heme biosynthesis caused by partial ferrochelatase deficiency, resulting in protoporphyrin overproduction which is responsible for painful skin photosensitivity. Chronic liver disease is the most severe complication of EPP, requiring liver transplantation in some patients. Data from a mouse model suggest that cytotoxic bile formation with high concentrations of bile salts and protoporphyrin may cause biliary fibrosis by damaging bile duct epithelium. In humans, cholestasis is a result of intracellular and canalicular precipitation of protoporphyrin. To limit liver damage two strategies may be considered: the first is to reduce protoporphyrin production and the second is to enhance protoporphyrin excretion. Bile salts are known to increase protoporphyrin excretion via the bile, while heme arginate is used to decrease the production of porphyrins in acute attacks of hepatic porphyrias. The Griseofulvin-induced protoporphyria mouse model has been used to study several aspects of human protoporphyria including the effects of bile salts. However, the best EPP animal model is an ethylnitrosourea-induced point mutation with fully recessive transmission, named ferrochelatase deficiency (Fech(m1Pas)). Here we investigate the effect of early ursodesoxycholic acid (UDCA) administration and heme-arginate injections on the ferrochelatase deficient EPP mouse model. In this model UDCA administration and heme-arginate injections do not improve the protoporphyric condition of Fech(m1Pas)/Fech(m1Pas) mice.

International audience; Erythropoietic protoporphyria is an inherited disorder of heme biosynthesis caused by partial ferrochelatase deficiency, resulting in protoporphyrin (PP) overproduction by erythrocytes. In humans, it is responsible for painful skin photosensitivity and, occasionally, liver failure due to accumulation of PP in the liver. The ferrochelatase deficiency mouse mutation is the best animal model available for human erythropoietic protoporphyria. The original description, based on mice with a BALB/cByJCrl genetic background, reported a disease resembling the severe form of the human disease, with anemia, jaundice, and liver failure. Using congenic strains, we investigated the effect of genetic background on the severity of the phenotype. Compared with BALB/cByJCrl, C57BL/6JCrl mice developed moderate but increasing anemia and intense liver accumulation of PP with severe hepatocyte damage and loss. Bile excretory function was not affected, and bilirubin remained low. Despite the highest PP concentration in erythrocytes, anemia was mild and there were few PP deposits in the liver in SJL/JOrlCrl homozygotes. Discriminant analysis using six hematologic and biochemical parameters showed that homozygotes of the three genetic backgrounds could be clustered in three well-separated groups. These three congenic strains provide strong evidence for independent genetic control of bone marrow contribution of PP overproduction to development of liver disease and biliary PP excretion. They provide a tool to investigate the physiological mechanisms involved in these phenotypic differences and to identify modifying genes.

International audience; The sequencing of the human and the mouse genomes has shown that the chromosomes of these two species contain approximately 30000 genes. The biological systems that can be studied in an individual or in a tissue result from complex interactions within this multitude of genes. Before describing these interactions, it is necessary to understand the function of each gene. In the mouse, congenic strains are developed to introduce a chromosomal segment in a given inbred genetic background. One can then compare the biological effects of different alleles at the same locus in the same genetic background or the effect of a given allele in different genetic backgrounds. One can also introduce into different congenic strains with the same genetic background genes which control a complex genetic trait, then combine these genes by appropriate crosses to study their interactions. Although the chromosomal segment transferred into a congenic strain usually contains up to several hundreds of genes, molecular markers can be used to reduce this number as well as the number of crosses required for the development of congenic strains.; Le séquençage du génome de l’homme et de la souris a montré que le patrimoine génétique de ces deux espèces comporte environ 30 000 gènes. Les phénomènes biologiques que l’on peut étudier dans un organisme ou un tissu résultent d’interactions complexes au sein de cette multitude de gènes. Avant de décrire ces interactions, il faut pouvoir comprendre la fonction de chaque gène. Chez la souris, les lignées congéniques permettent d’introduire un segment chromosomique dans un fonds génétique consanguin déterminé. On peut alors comparer les effets de différents allèles d’un même locus dans un fonds génétique identique ou l’effet d’un même allèle dans différents fonds génétiques. On peut également isoler dans des lignées congéniques différentes possédant le même fonds génétique les gènes contrôlant un caractère génétique complexe, puis combiner ces gènes par des croisements pour en étudier les interactions. Si le segment transféré dans une lignée congénique contient généralement plusieurs centaines de gènes, l’utilisation de marqueurs génétiques permet de réduire ce nombre, ainsi que le nombre de croisements nécessaire.

International audience; Genetic interaction between a maternal factor and the zygotic genome controls the intestine length in PRM/Alf mice. Physiol Genomics 16: 82–89, 2003. First published October 14, 2003; 10.1152/physiolgenomics.00106.2003.—Postoperative management of small and large bowel resections would be helped by use of intestinotrophic molecules. Here, we present a mouse inbred strain called PRM/Alf that is characterized by a selective intestinal lengthening. We show that PRM/Alf intestine is one-third longer compared with other inbred strains. The phenotype is acquired mostly during the postnatal period, before weaning. Its genetic determinism is polygenic, and involves a strong maternal effect. Cross-fostering experiments revealed that the dam’s genotype acts synergistically with the offspring’s genotype to confer the longest intestine. Moreover, genes in the offspring have a direct effect on intestine length. Possible involvement of milk growth factors and identification of candidate genes are discussed.

International audience; During the course of a study aimed at isolating transcripts specifically or preferentially expressed in the inner ear, we identified a novel gene, encoding a fibrocyte-derived protein, that we named Fdp. Fdp is predicted to be a secreted 128-amino acid protein, which is highly homologous to the melanoma-inhibiting activity/cartilage-derived retinoic acid-sensitive protein (MIA/CD-RAP), a cartilage-specific protein also expressed in several tumors. Fdp and MIA/CD-RAP thus define a new family of proteins. Fdp is expressed from embryonic day 10.5 in the mesenchyme surrounding the otic epithelium. During development, these cells progressively aggregate, condense, and differentiate into cartilaginous cells forming the otic capsule, which no longer expresses Fdp, and into fibrocytes surrounding the epithelia, which strongly express Fdp. In order to address the function of Fdp, we developed an in vitro antisense oligonucleotide approach using microdissected periotic mesenchyme micromass cultures, and showed that Fdp antisense oligonucleotide treatment results in a significant reduction in chondrogenesis. Our results demonstrate that Fdp plays a role in the initiation of periotic mesenchyme chondrogenesis. Accordingly, Fdp and its human ortholog FDP, which map to chromosome 2 and band 20p11, respectively, could be candidate genes for forms of deafness associated with malformations of the otic capsule.

International audience; Theiler's virus persists in the white matter of the spinal cord of genetically susceptible mice and causes primary demyelination. The virus persists in macrophages/microglial cells, but also in oligodendrocytes, the myelin-forming cells. Susceptibility/resistance to this chronic infection has been mapped to several loci including one tentatively located in the telomeric region of chromosome 18, close to the myelin basic protein locus (Mbp locus). To determine if the MBP gene influences viral persistence, we inoculated C3H mice bearing the shiverer mutation, a 20-kb deletion in the gene. Whereas control C3H mice were of intermediate susceptibility , C3H mice heterozygous for the mutation were very susceptible, and those homozygous for the mutation were completely resistant. This resistance was not immune mediated. Furthermore, C3H/101H mice homozy-gous for a point mutation in the gene coding for the proteolipid protein of myelin, the rumpshaker mutation, were resistant. These results strongly support the view that oligodendrocytes are a necessary viral target for the establishment of a persistent infection by Theiler's virus.

A new autosomal recessive mutation of the house mouse developed generalized alopecia associated with breakage of abnormal hair shafts. This mutation, named ‘lanceolate hair' (symbol: lah ), arose in a mutagenesis experiment using ethylnitrosourea. Hair shafts were short with a focal degeneration at the breakpoint characterized by a pronounced enlargement at the apex, resembling a lance head. Plucked hair fibers were 2.0 to 3.5mm in length with a normal base, suggesting that there was a synchronized developmental defect. Histologic examination of anagen follicles revealed abnormal cornification of the matrix region with degeneration resulting in the focal hair shaft deformity. Catagen follicles showed pronounced follicular dystrophy but telogen follicles were almost normal. There was a marked, persistent thickening of the epidermis associated with a non-scarring, relatively non-inflammatory ichthyosiform dermatitis. These features are found in the Netherton's syndrome of the human, for which this mouse mutation may represent a model. The lah mutation has been localized to the centromeric end of mouse Chromosome 18.

International audience; Theiler's murine encephalomyelitis virus is responsible for a chronic inflammatory demyelinating disease of the central nervous system of the mouse. The disease is associated with persistent viral infection of the spinal cord. Some strains of mice are susceptible to viral infection, and other strains are resistant. The effect of the genetic background of the host on viral persistence has not been thoroughly investigated. We studied the amount of viral RNA in the spinal cords of 17 inbred strains of mice and their F1 crosses with the SJL/J strain and observed a large degree of variability among strains. The pattern of viral persistence among mouse strains could be explained by the interaction of two loci. One locus is localized in the H-2D region of the major histocompatibility complex, whereas the other locus is outside this complex and is not linked to the Tcrb locus on chromosome 6.

The expression of the class I genes encoding for histocompatibility Ag is complex both in adult and during development. Although ubiquitously expressed in the adult, the mRNA level of class I genes is variable from one organ to another. During development, H-2K mRNA expression has two phases: the first from blastocyst to day 11, where H-2K mRNA level is extremely low, and the second, beginning after day 11, when H-2K mRNA expression increases first dramatically (10x) and then progressively to birth. To localize the sequences responsible for the regulation of H-2K gene expression in the adult and during development, we have constructed a series of transgenic strains carrying 1) a 9-kb native H-2K gene, H-2K LF, corresponding to the entire H-2Kb gene with 2 kb of upstream sequences and 3 kb of downstream sequences, and 2) two hybrid constructs linking the same 5'-flanking region of H-2Kb gene to two reporter genes, the human growth hormone and the human c-myc proto-oncogene. Expression of the transgenes was compared with that of the endogeneous H-2K gene in adult organs and during development of the different transgenic strains. In the adult, the three constructs behave almost like the endogeneous H-2K gene, but the H-2K LF construct is the only one whose expression is independent of the integration site and related to the copy number. During development, both fusion genes are barely expressed in the embryo as well as in the extra-embryonic tissues, whereas the H-2K LF transgene expression parallels that of the endogeneous class I gene. Therefore, our results show that H-2K developmental regulatory sequences are not included in the region that controls H-2K mRNA expression in the adult, indicating that H-2K class I gene expression in adult organs and in development is regulated by different mechanisms.

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