Abstract
The genetic architecture of skull shape has been extensively studied in mice and the results suggest a highly polygenic and additive basis. In contrast few studies have explored the genetic basis of the skull variability. Canalization and developmental stability are the two components of phenotypic robustness. They have been proposed to be emergent properties of the genetic networks underlying the development of the trait itself, but this hypothesis has been rarely tested empirically. Here we use outbred mice to investigate the genetic architecture of canalization of the skull shape by implementing a genome-wide marginal epistatic test on 3D geometric morphometric data. The same data set had been used previously to explore the genetic architecture of the skull mean shape and its developmental stability. Here, we address two questions: (1) Are changes in mean shape and changes in shape variance associated with the same genomic regions? and (2) Do canalization and developmental stability rely on the same loci and genetic architecture and do they involve the same patterns of shape variation? We found that unlike skull mean shape, among-individual shape variance and fluctuating asymmetry (FA) show a total lack of additive effects. They are both associated with complex networks of epistatic interactions involving many genes (protein-coding and regulatory elements). Remarkably, none of the genomic loci affecting mean shape contribute these networks despite their enrichment for genes involved in craniofacial variation and diseases. We also found that the patterns of shape FA and individual variation are largely similar and rely on similar multilocus epistatic genetic networks, suggesting that the processes channeling variation within and among individuals are largely common. However, the loci involved in these two networks are completely different. This in turn underlines the difference in the origin of the variation at these two levels, and points at buffering processes that may be specific to each level.
Highlights
In recent years, studies exploring the genetic basis of skull shape have proliferated due to advances in high-throughput phenotyping techniques (Bromiley et al, 2014; Young and Maga, 2015) and genomic data collection (Flint and Eskin, 2012)
We address two main questions: (1) is the genetic architecture of the skull mean shape different from that of canalization and developmental stability? (2) Are the phenotypic patterns and the loci involved in the regulation of canalization and developmental stability different, indicative of different biological processes?
No association was found between genetic markers and shape variance when the additive genetic scan was used (Figure 2)
Summary
Studies exploring the genetic basis of skull shape have proliferated due to advances in high-throughput phenotyping techniques (Bromiley et al, 2014; Young and Maga, 2015) and genomic data collection (Flint and Eskin, 2012). Only few studies have explored the association between genetic variation and shape variance (Hallgrímsson et al, 2018), likely because mapping variance is computationally more demanding [but see for example Corty and Valdar (2018) for recent methodological advance] and requires larger sample sizes than the mean. Phenotypic robustness can be defined as the ability of an organism to buffer the impact of internal (e.g., genetic variation) and external factors (e.g., environmental effects) on the phenotype. It has been the subject of a vast literature (reviewed in Debat and David, 2001; De Coster et al, 2013; Hallgrímsson et al, 2018). Canalization has been traditionally quantified by the variation among individuals (e.g., Hallgrímsson et al, 2018)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
