Transcriptional control of mesodermal cell differentiation in vertebrates
Lead Research Organisation:
University of Cambridge
Department Name: Physiology
Abstract
Cells of an early vertebrate embryo have the ability to form many different tissue types, but as the embryo develops - and tissue-specific genes are activated - embryonic cells become increasingly more restricted in what types of cells they can form. Each cell follows a particular path of gene activation as it moves towards becoming a particular tissue. Ultimately one would like to have a ‘map‘ of the cascades of gene activity that are set in motion when a sperm fertilizes an egg, and which eventually lead to the formation of a complex animal with many tissue types.
This project sets out to describe the map of gene activity that initiates when cells in the early vertebrate embryo form ‘mesoderm‘, a basic cell type that will eventually develop into tissues like blood, heart and kidney. The results will then be applied to understanding the maps that underlie mesoderm formation from embryonic stem cells. This work is important not only because it will give us insights into basic processes that occur during early vertebrate embryogenesis, but because the knowledge gained from this project will inform the efforts of researchers in re-programming human embryonic stem cells for tissue replacement therapy.
This project sets out to describe the map of gene activity that initiates when cells in the early vertebrate embryo form ‘mesoderm‘, a basic cell type that will eventually develop into tissues like blood, heart and kidney. The results will then be applied to understanding the maps that underlie mesoderm formation from embryonic stem cells. This work is important not only because it will give us insights into basic processes that occur during early vertebrate embryogenesis, but because the knowledge gained from this project will inform the efforts of researchers in re-programming human embryonic stem cells for tissue replacement therapy.
Technical Summary
This project will provide new insight into how cells in the early vertebrate embryo begin to differentiate into mesodermal cell types by studying the gene regulatory programs that underlie their formation. The project builds on my recent work in defining transcriptional programs in embryonic mesoderm formation using genome-wide and unbiased approaches, and applies this work towards understanding the role mesodermal programs play in stem cell differentiation.
The first aim is to explore how different T-domain transcription factors recognize their distinct and common target genes during embryogenesis. Ntl and Spt are T-domain factors that act in concert to control most mesoderm formation. To date, the activities of these factors have been investigated at a single gene or morphological level. I will employ chromatin immunoprecipitation combined with genomic microarrays (ChIP-chip) to globally identify the direct transcriptional targets for Ntl and Spt in developing zebrafish embryos. I will then ask how they distinguish between different targets by identifying whether a ‘binding code‘ exists and by isolating potential binding partners that may co-regulate the activity of Ntl.
The second aim is to ask whether the same mesodermal pathways controlled Brachyury (the mammalian Ntl orthologue) are used during embryonic stem cell (ESC) differentiation. In this study I will ask which mesodermal tissues require Brachyury in differentiating ESCs, identify genome-wide direct targets of Brachyury, and then test which targets are required for mesoderm formation in ESCs.
Because transcriptional control of differentiation in stem cells is an emerging field of study, this project will substantially inform efforts to reconstruct tissue differentiation programs. Prominent efforts are in place to manipulate ESCs into medically applicable cell types, such as cardiac muscle cells. Unfortunately, our current knowledge of methods to induce differentiation programs is empirical, and does not reflect a detailed knowledge of the gene regulatory events underlying development. Understanding how both true embryonic cells and embryonic stem cells assume a mesodermal fate can answer outstanding questions surrounding whether ES cells follow, or are capable of following, embryonic pathways - an understanding required to rationally and reliably reconstitute specific tissues for clinical use.
The first aim is to explore how different T-domain transcription factors recognize their distinct and common target genes during embryogenesis. Ntl and Spt are T-domain factors that act in concert to control most mesoderm formation. To date, the activities of these factors have been investigated at a single gene or morphological level. I will employ chromatin immunoprecipitation combined with genomic microarrays (ChIP-chip) to globally identify the direct transcriptional targets for Ntl and Spt in developing zebrafish embryos. I will then ask how they distinguish between different targets by identifying whether a ‘binding code‘ exists and by isolating potential binding partners that may co-regulate the activity of Ntl.
The second aim is to ask whether the same mesodermal pathways controlled Brachyury (the mammalian Ntl orthologue) are used during embryonic stem cell (ESC) differentiation. In this study I will ask which mesodermal tissues require Brachyury in differentiating ESCs, identify genome-wide direct targets of Brachyury, and then test which targets are required for mesoderm formation in ESCs.
Because transcriptional control of differentiation in stem cells is an emerging field of study, this project will substantially inform efforts to reconstruct tissue differentiation programs. Prominent efforts are in place to manipulate ESCs into medically applicable cell types, such as cardiac muscle cells. Unfortunately, our current knowledge of methods to induce differentiation programs is empirical, and does not reflect a detailed knowledge of the gene regulatory events underlying development. Understanding how both true embryonic cells and embryonic stem cells assume a mesodermal fate can answer outstanding questions surrounding whether ES cells follow, or are capable of following, embryonic pathways - an understanding required to rationally and reliably reconstitute specific tissues for clinical use.