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- Gunnarsson, Ulrika
(författare)
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Genetic Studies of Pigmentation in Chicken
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Domestic animals have been selected by humans for thousands of years, which have drastically altered their genetic constitution and phenotypes. In this thesis, several of the most important genes causing pigmentation differences between the wild red junglefowl (Gallus gallus) and domestic chickens have been identified. Pigmentation phenotypes are easily scored, and the genes underlying these phenotypes are valuable models to study gene function and gene interaction. Dominant white colour is widespread among domestic chickens. The Dominant white allele specifically inhibits the expression of black (eumelanin) pigment and we identified several insertion/deletion mutations in the PMEL17 gene causing the different phenotypes controlled by this locus. The Silver allele on the other hand inhibits the expression of red (pheomelanin) colour and is a genetic variant of the SLC45A2 gene. Silver is the first pheomelanin-specific mutation(s) reported for this gene. An 8 kb deletion, including a conserved enhancer element, 14 kb upstream of the transcription factor SOX10 is causing the Dark brown phenotype. This phenotype restricts the expression of eumelanin and enhances red pheomelanin in specific parts of the plumage. These three gene identifications have extended the knowledge about genes affecting melanocyte function. Carotenoid-based pigmentation is of utmost importance in birds and other animals. The yellow skin allele in chicken allows deposition of carotenoids in skin and explains why most domestic chickens have yellow legs. We demonstrated that the yellow skin phenotype is caused by a tissue specific regulatory mutation in the gene for the enzyme beta-caroten dioxygenase 2 (BCDO2). This was the first identification of a specific gene underlying carotenoid-based pigmentation. Interestingly, the yellow skin haplotype was shown to originate from the grey junglefowl (Gallus sonneratii) and not the red junglefowl as expected, thus presenting the first conclusive evidence for a hybrid origin of the domestic chicken.
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| 4. |
- Eriksson, Jonas, et al.
(författare)
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Identification of the yellow skin gene reveals a hybrid origin of the domestic chicken
- 2008
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Ingår i: PLoS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 4:2, s. e1000010-
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Tidskriftsartikel (refereegranskat)abstract
- Yellow skin is an abundant phenotype among domestic chickens and is caused by a recessive allele (W*Y) that allows deposition of yellow carotenoids in the skin. Here we show that yellow skin is caused by one or more cis-acting and tissue-specific regulatory mutation(s) that inhibit expression of BCDO2 (beta-carotene dioxygenase 2) in skin. Our data imply that carotenoids are taken up from the circulation in both genotypes but are degraded by BCDO2 in skin from animals carrying the white skin allele (W*W). Surprisingly, our results demonstrate that yellow skin does not originate from the red junglefowl (Gallus gallus), the presumed sole wild ancestor of the domestic chicken, but most likely from the closely related grey junglefowl (Gallus sonneratii). This is the first conclusive evidence for a hybrid origin of the domestic chicken, and it has important implications for our views of the domestication process.
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| 5. |
- Gunnarsson, Ulrika, et al.
(författare)
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Mutations in SLC45A2 Cause Plumage Color Variation in Chicken and Japanese Quail
- 2007
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Ingår i: Genetics. - : Oxford University Press (OUP). - 0016-6731 .- 1943-2631. ; 175:2, s. 867-877
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Tidskriftsartikel (refereegranskat)abstract
- S*S (Silver), S*N (wild type/gold), and S*AL (sex-linked imperfect albinism) form a series of alleles at the S (Silver) locus on chicken (Gallus gallus) chromosome Z. Similarly, sex-linked imperfect albinism (AL*A) is the bottom recessive allele at the orthologous AL locus in Japanese quail (Coturnix japonica). The solute carrier family 45, member 2, protein (SLC45A2), previously denoted membrane-associated transporter protein (MATP), has an important role in vesicle sorting in the melanocytes. Here we report five SLC45A2 mutations. The 106delT mutation in the chicken S*AL allele results in a frameshift and a premature stop codon and the corresponding mRNA appears to be degraded by nonsense-mediated mRNA decay. A splice-site mutation in the Japanese quail AL*A allele causes in-frame skipping of exon 4. Two independent missense mutations (Tyr277Cys and Leu347Met) were associated with the Silver allele in chicken. The functional significance of the former mutation, associated only with Silver in White Leghorn, is unclear. Ala72Asp was associated with the cinnamon allele (AL*C) in the Japanese quail. The most interesting feature concerning the SLC45A2 variants documented in this study is the specific inhibition of expression of red pheomelanin in Silver chickens. This phenotypic effect cannot be explained on the basis of the current, incomplete, understanding of SLC45A2 function. It is an enigma why recessive null mutations at this locus cause an almost complete absence of both eumelanin and pheomelanin whereas some missense mutations are dominant and cause a specific inhibition of pheomelanin production.
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| 6. |
- Gunnarsson, Ulrika, et al.
(författare)
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The Dark brown plumage color in chickens is caused by an 8.3 kb deletion upstream of SOX10.
- 2011
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Ingår i: Pigment cell & melanoma research. - 1755-148X .- 1755-1471.
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Tidskriftsartikel (refereegranskat)abstract
- The Dark brown mutation in chickens reduces expression of black eumelanin and enhances expression of red pheomelanin but only in certain parts of the plumage. Here we present genetic evidence that an 8.3 kb deletion upstream of the SOX10 transcription start site is the causal mutation underlying the Dark brown phenotype. The SOX10 transcription factor has a well-established role in melanocyte biology and is essential for melanocyte migration and survival. Previous studies have demonstrated that the mouse homolog of a highly conserved element within the deleted region is a SOX10 enhancer. The mechanism of action of this mutation remains to be established but one possible scenario is that the deletion leads to reduced SOX10 expression which in turn down-regulates expression of key enzymes in pigment synthesis such as tyrosinase. Lower tyrosinase activity leads to a shift towards a more pheomelanistic (reddish) plumage color, which is the characteristic feature of the Dark brown phenotype.
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| 8. |
- Hellström, Anders R., et al.
(författare)
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Sex-linked barring in chickens is controlled by the CDKN2A/B tumour suppressor locus
- 2010
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Ingår i: Pigment Cell and Melanoma Research. - : Blackwell Publishing Group. - 1755-1471 .- 1755-148X. ; 23:4, s. 521-530
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Tidskriftsartikel (refereegranskat)abstract
- Sex-linked barring, a common plumage colour found in chickens, is characterized by black and white barred feathers. Previous studies have indicated that the white bands are caused by an absence of melanocytes in the feather follicle during the growth of this region. Here we show that Sex-linked barring is controlled by the CDKN2A/B locus, which encodes the INK4b and ARF transcripts. We identified two non-coding mutations in CDKN2A that showed near complete association with the phenotype. Also identified were two missense mutations at highly conserved sites, V9D and R10C, and every bird tested with a confirmed Sex-linked barring phenotype carried one of these missense mutations. Further work is required to determine if one of these or a combined effect of two or more CDKN2A mutations is causing Sex-linked barring. This novel finding provides the first evidence that the tumour suppressor locus CDKN2A/B can affect pigmentation phenotypes and sheds new light on the functional significance of this gene.
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| 9. |
- Ka, Sojeong, 1976-, et al.
(författare)
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Proviral integrations and expression of endogenous Avian leucosis virus during long term selection for high and low body weight in two chicken lines
- 2009
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Ingår i: Retrovirology. - : Springer Science and Business Media LLC. - 1742-4690. ; 6, s. 68-
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Tidskriftsartikel (refereegranskat)abstract
- Background:Long-term selection (> 45 generations) for low or high juvenile body weight from a common founder population of White Plymouth Rock chickens has generated two extremely divergent lines, the LWS and HWS lines. In addition to a > 9-fold difference between lines for the selected trait, large behavioural and metabolic differences between the two lines evolved during the course of the selection. We recently compared gene expression in brain tissue from birds representing these lines using a global cDNA array analysis and the results showed multiple but small expression differences in protein coding genes. The main differentially expressed transcripts were endogenous retroviral sequences identified as avian leucosis virus subgroup-E (ALVE). Results: In this work we confirm the differential ALVE expression and analysed expression and number of proviral integrations in the two parental lines as well as in F-9 individuals from an advanced intercross of the lines. Correlation analysis between expression, proviral integrations and body weight showed that high ALVE levels in the LWS line were inherited and that more ALVE integrations were detected in LWS than HWS birds.Conclusion:We conclude that only a few of the integrations contribute to the high expression levels seen in the LWS line and that high ALVE expression was significantly correlated with lower body weights for the females but not males. The conserved correlation between high expression and low body weight in females after 9 generations of intercrosses, indicated that ALVE loci conferring high expression directly affects growth or are very closely linked to loci regulating growth.
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