Deep Cell Movement in Fundulus

Trinkaus and Tickle also studied the deformability of the cell surface of Fundulus deep cells, especially in relation to normal bleb formation, and the extent to which blebs act as organs of locomotion in the movement of deep cells (Trinkaus Archives, Box 10, Folder 23, Tickle's MBL Research Application on Fundulus, 1975). Part of Tickle and Trinkaus’s work on Fundulus’ deep cells during that summer focused on whether the difference between gastrula cells and blastula cells in vitro could be explained by surface adhesiveness alone. Tickle believed that the reason blastula cells retain their rounded shape, while gastrula cells flatten, in in vitro culture, was that gastrula cells exhibited increased cell surface deformability. To test this hypothesis, Tickle created a device to exert negative pressure or suction on the cultured cells. After a few false starts in trying the optimize the necessary equipment for these experiments, Tickle successfully showed that early gastrula cells require less negative pressure to deform in vitro compared to blastula cells. This result corroborated the current understanding of the normal behaviour of deep cells in vivo. Blastula cells form blebs, remain rounded in shape, and are active but do not engage in locomotion, whereas early gastrula cells transform blebs into extended lobopodia and engage in locomotion. The increased deformability of these later stage cells is also associated with the breakdown of the microfilaments in blebs, which allow the flow of cytoplasm into the lobopodia and enables locomotion during gastrulation. Tickle and Trinkaus published their results in a paper titled “Change in the Surface Extensibility of Fundulus Deep Cells During Early Development,” in the Journal of Cell Science.

In the process of conducting the experiments to test their hypotheses about the deformability of the cell surface during different stages of development, Trinkaus and Tickle made another serendipitous discovery about cell behaviour. They noticed that when a cell is nudged to form a bleb, somehow that cell communicates to the adjacent cells to form blebs. That observation led them to hypothesize that there must be some sort of signal transmitted from cell to cell during this process, and that there must be something on the cell surface that allows for this transmission to occur. Tickle and Trinkaus published a short paper on this work in Nature in 1976.

In his autobiography, Trinkaus recalls those summers at the MBL as productive years and praises Tickle as a researcher “with skill, determination, humour, and the legendary British stiff upper lip” (Trinkaus 2003, 235). After her post-doctoral work with Trinkaus, Tickle went on to have a distinguished research career as a developmental biologist and, as of 2015, she is an Emeritus Professor at the University of Bath in the UK.