Smith lab Developmental Biology Laboratory
: Live imaging of mesoderm and cardiac progenitors
Introduction
Our group is interested in understanding how embryonic cells develop into different lineages and go in to form a heart during morphogenesis. Addressing this question has important implications for our understanding of congenital heart diseases and the design of regenerative methods targeting specific populations of heart cells.
Our heart is composed of four chambers, two ventricles and two atria arranged in parallel and driving blood from the body to the lungs and through the rest of the body. We recently established a fate map demonstrating that each group of cells forming the heart have distinct spatial and temporal origins in the primitive streak (the early embryonic structure that gives rise to mesoderm and endoderm tissues). The ventricular progenitors are the first to leave the streak, followed by progenitors contributing to the atrium and outflow tract.
Cells located in distal regions of the primitive streak contribute first to the left ventricle (mid-streak stage), then to the right ventricle (late-streak stage), and finally to the outflow tract (OB-EB stages). Although the outflow and atria leave the primitive streak at similar stages, they arise from different regions. The outflow tract originates from distal locations in the primitive streak while atrial progenitors are positioned more proximally. AHF, anterior heart field; aPS, anterior primitive streak; AVC, atrioventricular canal; cranial pxm, cranial paraxial mesoderm; EB, early bud; epi, epicardium; LV, left ventricle; OB, no bud; OFT, outflow tract; Pha, Pharyngeal arches; PS, primitive streak; pSHF, posterior second heart field; RV, right ventricle.
In our latest work, we established a new live-imaging method to enable the simultaneous recording of cell migration and intracellular signal transduction pathways during gastrulation in the mouse. The analysis is complemented by single-cell RNA sequencing, allowing us to distinguish differentiation trajectories between wildtype and mutant progenitors. We are investigating if depending on timing and sites of ingression through the primitive streak, cardiac progenitors adopt distinct migratory routes that expose them to signalling at distinct developmental time points, thus influencing their cardiac fate.
Videos
2 photon microscopy movie showing single mesodermal cells migrating from the primitive streak towards the anterior aspect of the embryo. The embryo is imaged from embryonic day 7 and oriented laterally. Video generated by Kenzo Ivanovitch (Jim Smith's group), with support from the Crick's advanced light microscopy team.
Zoom on a single cell from Movie1-part1. Single cells can be unambiguously identified and tracked throughout cell division when labelled at low density. Video generated by Kenzo Ivanovitch (Jim Smith's group), with support from the Crick's advanced light microscopy team.
Brightfield movie of a wildtype embryo imaged from embryonic day 6, at the onset of gastrulation, for over 15 hours. Video generated by Kenzo Ivanovitch (Jim Smith's group), with support from the Crick's advanced light microscopy team.
Movie showing the primitive streak in green in an embryonic day 7 mouse embryo. Movie acquired using the Luxendor MuVi light sheet microscope. Video generated by Kenzo Ivanovitch (Jim Smith's group), with support from the Crick's advanced light microscopy team.
Movie showing the cardiac crescent in green over a period of ~6 hours. Luxendor MuVi light sheet microscope. Movie acquired with the Luxendor MuVi light sheet microscope. Video generated by Kenzo Ivanovitch (Jim Smith's group), with support from the Crick's advanced light microscopy team.
Last time point from Movie 4-part2. Video generated by Kenzo Ivanovitch (Jim Smith's group), with support from the Crick's advanced light microscopy team.
