Mapping the Naked Neck (NA) and Polydactyly (PO) mutants of the chicken with microsatellite molecular markers

The bulked segregant analysis methodology has been used to map, with microsatellite markers, two morphological mutations in the chicken: polydactyly (PO) and naked neck (NA). These autosomal mutations show partial dominance for NA, and dominance with incomplete penetrance for PO. They were mapped previously to different linkage groups of the classical map, PO to the linkage group IV and NA being linked to the erythrocyte antigen CPPP. An informative family of 70 offspring was produced by mating a sire, heterozygous for each of the mutations, to 7 dams homozygous recessive for each locus. Three DNA pools were prepared, pool PO included 20 chicks exhibiting at least one extra-toe, pool NA included 20 non-polydactyly chicks showing the typical phenotype associated with heterozygosity for the naked neck mutation, and pool NP included 20 chicks exhibiting neither of the mutant phenotypes. Typings were done on an ABI-373 automatic sequencer with 147 microsatellite markers covering most of the genome. An unbalanced distribution of sire marker alleles were detected between pool PO, and pools NA and NP, for two markers of chromosome 2p, MCW0082 and MCW0247. A linkage analysis taking into account the incomplete penetrance of polydactyly (80%) was performed with additional markers of this region and showed that the closest marker to the PO locus was MCW0071 (5 cM, lod score = 9). MCW0071 lies within the engrailed gene EN2 in the chicken. In the mouse, the homologous gene maps on chromosome 5, close to the hemimelic extra-toes mutation Hx. In the case of the NA locus, markers of chromosome 3 were selected because CPPP was mapped on this chromosome. Analysis of individual typings showed a linkage of 5.7 cM (lod score = 13) between the NA locus and ADL0237 in the distal region of chromosome 3q. These results contribute to connecting the former classical map to the molecular genetic map of the chicken, and open the way to the identification of the molecular nature of two developmental mutations of the chicken that are known to occur in many breeds of chickens

Epilepsy Caused by an Abnormal Alternative Splicing with Dosage Effect of the SV2A Gene in a Chicken Model

Photosensitive reflex epilepsy is caused by the combination of an individual's enhanced sensitivity with relevant light stimuli, such as stroboscopic lights or video games. This is the most common reflex epilepsy in humans; it is characterized by the photoparoxysmal response, which is an abnormal electroencephalographic reaction, and seizures triggered by intermittent light stimulation. Here, by using genetic mapping, sequencing and functional analyses, we report that a mutation in the acceptor site of the second intron of SV2A (the gene encoding synaptic vesicle glycoprotein 2A) is causing photosensitive reflex epilepsy in a unique vertebrate model, the Fepi chicken strain, a spontaneous model where the neurological disorder is inherited as an autosomal recessive mutation. This mutation causes an aberrant splicing event and significantly reduces the level of SV2A mRNA in homozygous carriers. Levetiracetam, a second generation antiepileptic drug, is known to bind SV2A, and SV2A knock-out mice develop seizures soon after birth and usually die within three weeks. The Fepi chicken survives to adulthood and responds to levetiracetam, suggesting that the low-level expression of SV2A in these animals is sufficient to allow survival, but does not protect against seizures. Thus, the Fepi chicken model shows that the role of the SV2A pathway in the brain is conserved between birds and mammals, in spite of a large phylogenetic distance. The Fepi model appears particularly useful for further studies of physiopathology of reflex epilepsy, in comparison with induced models of epilepsy in rodents. Consequently, SV2A is a very attractive candidate gene for analysis in the context of both mono- and polygenic generalized epilepsies in humans

Complete association between a retroviral insertion in the tyrosinase gene and the recessive white mutation in chickens

<p>Abstract</p> <p>Background</p> <p>In chickens, three mutant alleles have been reported at the <it>C </it>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 (<it>TYR</it>) gene. The present work describes an approach to identify the structural rearrangement in the <it>TYR </it>gene associated with the recessive white mutation.</p> <p>Results</p> <p>Molecular analysis of the chicken <it>TYR </it>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 <it>TYR </it>gene by long-range PCR. Molecular cloning and sequencing results showed the insertion of a complete avian retroviral sequence of the Avian Leukosis Virus (<it>ALV</it>) 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.</p> <p>Conclusion</p> <p>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.</p

Semen cryopreservation for ex-situ management of genetic diversity in chicken: creation of the French Avian Cryobank

International audienc

Biodiversity of domestic birds

International audienc

Complete association between a retroviral insertion in the tyrosinase gene and the recessive white mutation in chickens-5

<p><b>Copyright information:</b></p><p>Taken from "Complete association between a retroviral insertion in the tyrosinase gene and the recessive white mutation in chickens"</p><p>BMC Genomics 2006;7():19-19.</p><p>Published online 5 Feb 2006</p><p>PMCID:PMC1373650.</p><p>Copyright © 2006 Chang et al; licensee BioMed Central Ltd.</p>n 5 probe. A 4.1 kb HIII band and a 1.8 kb BHI-HIII band were obtained after HIII single digestion and BHI-HIII double digestion in the recessive white mutation

Complete association between a retroviral insertion in the tyrosinase gene and the recessive white mutation in chickens-1

<p><b>Copyright information:</b></p><p>Taken from "Complete association between a retroviral insertion in the tyrosinase gene and the recessive white mutation in chickens"</p><p>BMC Genomics 2006;7():19-19.</p><p>Published online 5 Feb 2006</p><p>PMCID:PMC1373650.</p><p>Copyright © 2006 Chang et al; licensee BioMed Central Ltd.</p>A. The 4.1 kb band was only found in homozygous recessive white chickens while the 2.7 kb band was only found in the wild type chickens

Complete association between a retroviral insertion in the tyrosinase gene and the recessive white mutation in chickens-8

<p><b>Copyright information:</b></p><p>Taken from "Complete association between a retroviral insertion in the tyrosinase gene and the recessive white mutation in chickens"</p><p>BMC Genomics 2006;7():19-19.</p><p>Published online 5 Feb 2006</p><p>PMCID:PMC1373650.</p><p>Copyright © 2006 Chang et al; licensee BioMed Central Ltd.</p>ken was 675 bp

Complete association between a retroviral insertion in the tyrosinase gene and the recessive white mutation in chickens-2

<p><b>Copyright information:</b></p><p>Taken from "Complete association between a retroviral insertion in the tyrosinase gene and the recessive white mutation in chickens"</p><p>BMC Genomics 2006;7():19-19.</p><p>Published online 5 Feb 2006</p><p>PMCID:PMC1373650.</p><p>Copyright © 2006 Chang et al; licensee BioMed Central Ltd.</p>me restriction pattern as the total chicken tyrosinase cDNA probe. A simple HIII digestion yielded 4.1 kb and 2.7 kb fragments in carriers of the recessive white or wild type allele at the locus, respectively. A double digestion with BHI+HIII enzymes yielded a 2.7 kb fragment in chickens carrying the normal allele and a 1.8 kb fragment in chickens carrying the recessive white allele