Dr Branko V. Latinkic - PhD
Cardiac precursors are specified during gastrulation, almost simultaneously with major developmental decisions that will shape the embryo. Because of this, it is difficult to specifically manipulate cardiac specification, without affecting other patterning events.
Numerous transcription factors have been implicated in heart development (“cardiogenic factors”), but their precise roles in cardiac specification are unclear, largely because of their involvement in the development of other tissues.
LEFT: Cardiac tissue (dark blue MLC2 expression) in animal cap/anterior endoderm conjugates (st. 34).
RIGHT: Cardiomyocytes (blue) are induced in animal cap cells (red).
Our approach to cardiac specification and the roles of cardiogenic transcription factors takes advantage of several simple assays based on pluripotent animal pole explants derived from blastula stage Xenopus embryos. In isolation these explants normally develop into epidermis, but can be converted into cardiomyocytes in several ways. One is by exposure to cardiogenic signals from the anterior endoderm.
Animal cap cells can also be induced to differentiate as cardiomyocytes by activin/Nodal signalling or by cardiogenic transcription factor GATA4.
Cardiomyocyte differentiation in GATA4-injected animal pole explants revealed by in situ hybridisation for MLC2; anterior half of a stage-control embryo is shown.
These assays represent models of cardiogenesis of decreasing complexity that are considerably simpler than cardiogenesis in vivo. Importantly, cardiogenesis in these assays recapitulates normal course of cardiomyocyte differentiation as it occurs in vivo. Given the ease of experimental manipulation, frog embryo and explants provide powerful models for elucidating cellular and molecular mechanisms of early heart development.
The questions we are addressing using these models include:
- what are the signals that specify cardiac fate and how they work?
- what is the initial, or immediate-early genomic programme activated by cardiac specification?
- how are the genes that comprise this programme regulated?
- how is the cardiogenic programme differentiated from related programmes for early mesoderm and endoderm specification?
- what are the molecular determinants of cardiogenic activity of GATA4?
- British Heart Foundation
Prof. M. Nemer - Ottawa
Dr Nick Allen - Cardiff