Investigating the Genetic Causes of Bone Disease

Phenotypic plasticity, an important source of biodiversity, is the ability for an organism with a single genotype to produce myriad phenotypes in response to different environmental stimuli. The genetic mechanisms involved in phenotypic plasticity and their ability to cause evolutionary change remains poorly understood. Here, we experiment with the cichlid feeding apparatus with a focus on the lower jaw, a widely used model to understand rapid evolutionary divergence and phenotypic plasticity. We first demonstrate that changes in the cis-regulatory landscape of DNA can explain differential gene expression of some genes. This finding expands our understanding of the types of molecular mechanisms involved in phenotypic plasticity. We provide further evidence, via qPCR validation, for dynamic expression of a subset of these bone-marker genes over time, thus highlighting the fact that timing is important in plasticity studies. Finally, we show that morphological changes to the feeding apparatus in response to alternate feeding environments arise after the transcriptional response, and are localized to specific structures involved in foraging; the exact same structures that were used for our genetic studies. Evolutionarily, fish facial anatomy is homologous to human facial anatomy. Load-induced developmental plasticity is known to occur in humans and is the reason why dental interventions, such braces, are effective therapies. It is also the reason why impact exercise is an effective treatment for various degenerative bone diseases. These data further the understanding of phenotypic plasticity in fishes and thereby provide a more general understanding of bone health and diseases.