| 1. |
- Boije, Henrik, et al.
(författare)
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Sonic Hedgehog-Signalling Patterns the Developing Chicken Comb as Revealed by Exploration of the Pea-comb Mutation
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:12, s. e50890-
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Tidskriftsartikel (refereegranskat)abstract
- The genetic basis and mechanisms behind the morphological variation observed throughout the animal kingdom is stillrelatively unknown. In the present work we have focused on the establishment of the chicken comb-morphology byexploring the Pea-comb mutant. The wild-type single-comb is reduced in size and distorted in the Pea-comb mutant. Peacombis formed by a lateral expansion of the central comb anlage into three ridges and is caused by a mutation in SOX5,which induces ectopic expression of the SOX5 transcription factor in mesenchyme under the developing comb. Analysis ofdifferential gene expression identified decreased Sonic hedgehog (SHH) receptor expression in Pea-comb mesenchyme. Byexperimentally blocking SHH with cyclopamine, the wild-type single-comb was transformed into a Pea-comb-likephenotype. The results show that the patterning of the chicken comb is under the control of SHH and suggest that ectopicSOX5 expression in the Pea-comb change the response of mesenchyme to SHH signalling with altered combmorphogenesis as a result. A role for the mesenchyme during comb morphogenesis is further supported by the recentfinding that another comb-mutant (Rose-comb), is caused by ectopic expression of a transcription factor in combmesenchyme. The present study does not only give knowledge about how the chicken comb is formed, it also adds to ourunderstanding how mutations or genetic polymorphisms may contribute to inherited variations in the human face.
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| 2. |
- Imsland, Freyja, et al.
(författare)
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The Rose-comb Mutation in Chickens Constitutes a Structural Rearrangement Causing Both Altered Comb Morphology and Defective Sperm Motility
- 2012
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Ingår i: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7404 .- 1553-7390. ; 8:6, s. e1002775-
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Tidskriftsartikel (refereegranskat)abstract
- Rose-comb, a classical monogenic trait of chickens, is characterized by a drastically altered comb morphology compared to the single-combed wild-type. Here we show that Rose-comb is caused by a 7.4 Mb inversion on chromosome 7 and that a second Rose-comb allele arose by unequal crossing over between a Rose-comb and wild-type chromosome. The comb phenotype is caused by the relocalization of the MNR2 homeodomain protein gene leading to transient ectopic expression of MNR2 during comb development. We also provide a molecular explanation for the first example of epistatic interaction reported by Bateson and Punnett 104 years ago, namely that walnut-comb is caused by the combined effects of the Rose-comb and Pea-comb alleles. Transient ectopic expression of MNR2 and SOX5 (causing the Pea-comb phenotype) occurs in the same population of mesenchymal cells and with at least partially overlapping expression in individual cells in the comb primordium. Rose-comb has pleiotropic effects, as homozygosity in males has been associated with poor sperm motility. We postulate that this is caused by the disruption of the CCDC108 gene located at one of the inversion breakpoints. CCDC108 is a poorly characterized protein, but it contains a MSP (major sperm protein) domain and is expressed in testis. The study illustrates several characteristic features of the genetic diversity present in domestic animals, including the evolution of alleles by two or more consecutive mutations and the fact that structural changes have contributed to fast phenotypic evolution.
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| 3. |
- Wright, Dominic, et al.
(författare)
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Copy number variation in intron 1 of SOX5 causes the Pea-comb phenotype in chickens
- 2009
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Ingår i: PLoS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 5:6, s. e1000512-
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Tidskriftsartikel (refereegranskat)abstract
- Pea-comb is a dominant mutation in chickens that drastically reduces the size of the comb and wattles. It is an adaptive trait in cold climates as it reduces heat loss and makes the chicken less susceptible to frost lesions. Here we report that Pea-comb is caused by a massive amplification of a duplicated sequence located near evolutionary conserved non-coding sequences in intron 1 of the gene encoding the SOX5 transcription factor. This must be the causative mutation since all other polymorphisms associated with the Pea-comb allele were excluded by genetic analysis. SOX5 controls cell fate and differentiation and is essential for skeletal development, chondrocyte differentiation, and extracellular matrix production. Immunostaining in early embryos demonstrated that Pea-comb is associated with ectopic expression of SOX5 in mesenchymal cells located just beneath the surface ectoderm where the comb and wattles will subsequently develop. The results imply that the duplication expansion interferes with the regulation of SOX5 expression during the differentiation of cells crucial for the development of comb and wattles. The study provides novel insight into the nature of mutations that contribute to phenotypic evolution and is the first description of a spontaneous and fully viable mutation in this developmentally important gene.
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