2011 — 2015 |
Miller, Craig Thomas |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Developmental Genetics of Tooth Number Variation in Sticklebacks @ University of California Berkeley
DESCRIPTION (provided by applicant): Changes in tooth number are associated with orofacial clefting, the most common craniofacial birth defect in humans. Thus, knowledge of the developmental and genetic basis of tooth number regulation is critical for understanding human craniofacial and dental birth defects, as well as for understanding the fundamental process of tooth number specification. Although genetic studies in mice and humans have identified several signaling pathways involved in tooth development, little is known about the developmental and genetic mechanisms regulating tooth number. Most genetic pathways known to control mammalian craniofacial and tooth development are highly conserved and are also involved in craniofacial and tooth development in lower vertebrates, including fish. Genetic variants underlying natural variation can provide valuable insight into developmental processes and complement more traditional genetic studies of induced mutations in model organisms. Here natural variation in tooth number in the threespine stickleback fish (Gasterosteus aculeatus) is proposed as a new model system to learn how genes regulate tooth number. Different stickleback populations adapted to different diets exhibit dramatic changes in tooth number, with freshwater fish having twice the number of teeth as marine fish. The different forms can be crossed in the lab, enabling detailed forward genetic analyses to map factors controlling the changes in tooth number. Genome-wide linkage mapping has identified ten chromosome regions, or quantitative trait loci (QTL), controlling tooth number in sticklebacks, and methods are in place to identify the underlying genes. To test hypotheses about the developmental and molecular genetic basis of the tooth number differences, three specific aims are proposed. First, the developmental time course of the tooth differences seen in marine and freshwater populations will be determined by analyzing skeletal differentiation in embryos, larvae, and juveniles. Second, gene expression correlates of the tooth number differences will be identified by comparing gene expression patterns in developing craniofacial and dental tissues from marine and freshwater fish. Third, the genetic basis of a QTL on stickleback chromosome 21 controlling tooth gains will be identified by mapping, sequencing, gene expression, and transgenic experiments. PUBLIC HEALTH RELEVANCE: This research will provide fundamental knowledge of how genes control tooth number. This knowledge will help efforts to engineer tooth formation in vitro. In addition, since changes in tooth number are associated with common human craniofacial birth defects, this knowledge will lead to a better understanding and prevention of human craniofacial and dental birth defects.
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2016 — 2021 |
Miller, Craig Thomas |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Development Genetics of Tooth Number Variation in Sticklebacks @ University of California Berkeley
Project Summary The expected overall impact of this project is to identify developmental and genetic mechanisms underlying tooth formation and replacement. Teeth have classically been used as a model to study organogenesis, as teeth, like most organs, develop through reciprocal epithelial-mesenchymal interactions. Furthermore, 30 percent of people worldwide over the age of 65 have no natural teeth. Thus, knowledge of the developmental and genetic basis of tooth formation and replacement has relevance both for understanding organogenesis, as well as for understanding how teeth can be regenerated in vitro and ultimately in vivo. Although genetic studies in mice and humans have identified signaling pathways involved in tooth development, less is known about genetic mechanisms regulating tooth replacement. Fish replace their teeth constantly throughout adult life, and offer powerful systems for genetic analysis. Here, natural variation in tooth number in the threespine stickleback fish (Gasterosteus aculeatus) is leveraged as a new model system to learn how genes regulate tooth number and tooth replacement. Different stickleback populations adapted to different diets exhibit dramatic heritable changes in tooth number. Two different, independently derived freshwater populations have evolved major increases in tooth number compared to ancestral marine fish. In both high-toothed populations, the tooth number increase arises late in development through an accelerated tooth replacement rate. The different forms can be crossed in the lab, enabling detailed forward genetic analyses to map factors controlling the changes in tooth number. New genome editing methods allow functional tests of genes and cis-regulatory elements of interest. A cis-regulatory allele of the Bone Morphogenetic Protein 6 (Bmp6) gene is associated with evolved tooth gain in one high-toothed population. Pharmacological and genetic data suggest BMP signaling and Bmp6 positively regulate primary tooth number, but inhibit tooth replacement. To test hypotheses about the developmental and genetic bases of tooth formation and replacement, three specific aims are proposed. First, we will test whether BMP signaling and Bmp6 regulate dental stem cell quiescence during tooth replacement by BrdU and vital dye pulse-chase labeling, gene expression, and pharmacological experiments. Second, we will identify upstream regulators of two Bmp6 enhancers and determine enhancer and regulator functions during tooth development and replacement by pharmacological, transgenic, and genome editing experiments. Third, we will identify the genetic basis of evolved tooth gain in an independently derived high-toothed freshwater population with a distinct developmental genetic basis by a combination of genetic mapping, genome editing, and gene expression experiments. Together these results will shed new light on developmental and genetic mechanisms underlying tooth replacement.
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