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PhD Transfer Examination – Debanjan Barua (Winklbauer lab)

December 7, 2015 @ 2:10 pm - 3:10 pm

PhD Transfer Examination

Monday December 7th, 2:10 pm – Ramsay Wright Building, Rm. 432

Debanjan Barua (Winklbauer lab) 

Characterizing the mechanics of tissue separation behaviour at

Brachet’s cleft during gastrulation in Xenopus laevis


Boundary formation between two distinct tissues is a crucial yet still poorly understood developmental process. In contrast to boundaries where cells are intimately attached, cleft-like boundaries allow for movement of tissues while preventing intermixing of the distinct tissues. During gastrulation of the anuran Xenopus laevis, involuting mesoderm cells migrate across the ectodermal blastocoel roof without intruding into the ectodermal cell layer, forming a cleft-like boundary called Brachet’s cleft. Although key molecular factors that play a role in the development and maintenance of Brachet’s cleft have been uncovered, little is known about the mechanics underlying this design. I have recently characterized intercellular contacts at the boundary and found that boundary cells exhibit: close contacts at intercellular distances compatible with cadherin mediated adhesion, intermediate contacts at much greater distances which may be regulated by the ECM, and large gaps, all of which under normal conditions are maintained at a particular ratio. My preliminary data suggests that these types of cell contacts at the cleft are not fundamentally distinct from cell contacts within the boundary tissues, however, there seem to be clear quantitative differences in contact type distribution and tissue cohesion between the ectoderm and mesoderm tissues. Thus, I hypothesize that separation behavior is asymmetric at Brachet’s cleft. More specifically, at the boundary, the mesoderm treats the ectoderm as if it were mesoderm and the ectoderm surface remains unchanged after coming into contact with the mesoderm. In order to test this hypothesis, I will investigate and characterize boundary mechanisms at Brachet’s cleft during gastrulation and present a model of the cleft based on quantifiable mechanics. I hope that my findings will establish a link between the molecular and mechanical aspects of cleft-like boundary formation and contribute to a more comprehensive understanding of this process.

Ramsay Wright is a wheelchair accessible building.



December 7, 2015
2:10 pm - 3:10 pm
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Ramsay Wright Building, Room 432
25 Harbord St.
Toronto, ON M5S 3G5 Canada