Developmental stereotypy assessment in ascidian embryos

Embryogenesis, a central focus of developmental biology, is the development of a fertilized egg into tissues and organs. Comparing the development of individual embryos helps identify similarities and variations, providing a starting point to identify constraints acting during embryogenesis. Recent live microscopy techniques allow to acquire temporal series of 3D images, giving an unprecedented means to study developing embryos. This study focuses on ascidian embryos as the cellular stereotypy of their development enables investigations at the cellular level. More precisely, we propose a methodology to assess the extent of variation in the orientation of cell divisions. From a population of imaged embryos, we demonstrate that the cell division orientation of some cells unexpectedly exhibits a bimodal distribution.