Mechanisms of sex determination underpin female pattern polymorphism in Anolis sagrei
(2024) BION03 20232Degree Projects in Biology
- Abstract
- Anolis sagrei exhibit a female limited dorsal pattern polymorphism with two discrete pattern morphs (chevron or diamond). The underlying genetic basis has been traced to a Mendelian autosomal locus (gene CCDC170) which is adjacent to the gene for estrogen receptor one (ESR1). Thus, this model system gives an excellent opportunity to study the origin and maintenance of new phenotypic variants. In this thesis I attempted to visualize gene expression (ESR1 and CCDC170) during development through whole mount in situ hybridization. In an experimental approach, I explored pattern formation through temperature perturbation and application of exogenous 17β-estradiol during development. Results show that genotyping of the CCDC170 allele do not... (More)
- Anolis sagrei exhibit a female limited dorsal pattern polymorphism with two discrete pattern morphs (chevron or diamond). The underlying genetic basis has been traced to a Mendelian autosomal locus (gene CCDC170) which is adjacent to the gene for estrogen receptor one (ESR1). Thus, this model system gives an excellent opportunity to study the origin and maintenance of new phenotypic variants. In this thesis I attempted to visualize gene expression (ESR1 and CCDC170) during development through whole mount in situ hybridization. In an experimental approach, I explored pattern formation through temperature perturbation and application of exogenous 17β-estradiol during development. Results show that genotyping of the CCDC170 allele do not perfectly predict the phenotypic morph in female A. sagrei and that genotype-phenotype mismatches are more commonly observed for the chevron morph. In addition, the chevron morph becomes more deformed in lower incubation temperatures. Application of 17β-estradiol confirms that developmental pathways for sex-determination are vital to maintain the polymorphism as it leads to the feminization of males and the development of the associated female-specific dorsal pattern. Hormonal application also impacts the qualitative variation of the diamond morph, resulting in a reduced diamond amplitude and the formation of a straighter bar pattern. Thus, my results suggest a close relationship between mechanisms for sex determination and pattern formation. (Less)
- Popular Abstract
- From a young age, most of us notice the beauty of nature through the amazing breath of color and pattern apparent around us. Two obvious questions arise; what is the purpose of all the stripes, spots, and colors that populate the natural world; and second how does such variation arise? The question of the origin of new variation has been my focus, working with the brown anole, a lizard species that features two different back patterns. What makes this species special is that only females show both pattern types, even though both sexes carry the same pattern gene. Females either has a diamond pattern or a chevron pattern running from head to tail. Why would the same genetic “blueprint” lead to wildly different outcomes? One answer is that... (More)
- From a young age, most of us notice the beauty of nature through the amazing breath of color and pattern apparent around us. Two obvious questions arise; what is the purpose of all the stripes, spots, and colors that populate the natural world; and second how does such variation arise? The question of the origin of new variation has been my focus, working with the brown anole, a lizard species that features two different back patterns. What makes this species special is that only females show both pattern types, even though both sexes carry the same pattern gene. Females either has a diamond pattern or a chevron pattern running from head to tail. Why would the same genetic “blueprint” lead to wildly different outcomes? One answer is that the pattern gene is neighbor to a gene more active in females (estrogen gene) and that they as neighbors become entangled and share activity levels, thus the female pattern genes are more active leading to pattern differences.
To explore this explanation, I pursued three lines of inquiry. The first was to map where the relevant genes were active during development by marking them with fluorescent probes, this part of the project failed. Second, I explored how sensitive the pattern formation is to environmental disturbance by incubating eggs in low or high incubation temperatures. Temperature is a key factor as lizards grow from embryos to hatchlings. This showed that the chevron pattern is less robust, partly in that the pattern that forms does not always match the genetic background, and partly because this pattern becomes deformed at lower temperatures.
As a third approach, I applied estradiol to eggs as they developed. The idea here is that this will impact the female active estrogen gene, even in genetic males, which like a domino will activate the pattern gene, thus impacting the patterns we observe. Treating the eggs with estradiol led to males becoming feminized, both in reproductive characters, as well as forming a female-only pattern. The application also changed the way the female-only pattern formed, causing it to lose the wave-like shape, and instead become a straight bar. The result from the estradiol application shows that there’s a close tie between how sex is determined and the pattern formation. By hijacking existing machinery, the difficulty of a new pattern variation appearing is lowered. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9175987
- author
- Westelius, Tyra
- supervisor
- organization
- course
- BION03 20232
- year
- 2024
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9175987
- date added to LUP
- 2024-10-03 13:28:01
- date last changed
- 2024-10-03 13:28:01
@misc{9175987,
abstract = {{Anolis sagrei exhibit a female limited dorsal pattern polymorphism with two discrete pattern morphs (chevron or diamond). The underlying genetic basis has been traced to a Mendelian autosomal locus (gene CCDC170) which is adjacent to the gene for estrogen receptor one (ESR1). Thus, this model system gives an excellent opportunity to study the origin and maintenance of new phenotypic variants. In this thesis I attempted to visualize gene expression (ESR1 and CCDC170) during development through whole mount in situ hybridization. In an experimental approach, I explored pattern formation through temperature perturbation and application of exogenous 17β-estradiol during development. Results show that genotyping of the CCDC170 allele do not perfectly predict the phenotypic morph in female A. sagrei and that genotype-phenotype mismatches are more commonly observed for the chevron morph. In addition, the chevron morph becomes more deformed in lower incubation temperatures. Application of 17β-estradiol confirms that developmental pathways for sex-determination are vital to maintain the polymorphism as it leads to the feminization of males and the development of the associated female-specific dorsal pattern. Hormonal application also impacts the qualitative variation of the diamond morph, resulting in a reduced diamond amplitude and the formation of a straighter bar pattern. Thus, my results suggest a close relationship between mechanisms for sex determination and pattern formation.}},
author = {{Westelius, Tyra}},
language = {{eng}},
note = {{Student Paper}},
title = {{Mechanisms of sex determination underpin female pattern polymorphism in Anolis sagrei}},
year = {{2024}},
}