Highly reproducible spatiotemporal patterns of mammalian embryonic movements at the developmental stage of the earliest spontaneous motility

The principles underlying the variations in patterns of mammalian embryonic movements have not been established. In an attempt to clarify the mechanis m that is responsible for the variations in motor patterns, we carried out a precise quantitative spatiotemporal analysis of movements in mouse embryo s, using a transplacental perfusion method for the in vitro maintenance of live mammalian embryos. Episodes of spontaneous movements at the inception of motility, at embryonic day 12.5, occurred once every few minutes, lasted for several seconds and consisted of successive movements of body regions, the spatiotemporal patterns of which varied from episode to episode. By an alysing and categorizing the patterns of these movements, we found that emb ryonic movements follow relatively few restricted patterns with respect to the order of the movements of body regions. A further analysis of episodes at high spatiotemporal resolution revealed that most of the episodes in a m ajor category could be classified into two distinct subtypes. Each of these subtypes had its own highly reproducible spatiotemporal patterns of moveme nt. Overall, these results show that early embryonic movements follow relat ively few rather stereotyped patterns, and random local fluctuations have l ittle effect on such movement patterns. The appearance of one pattern out o f several rather stereotyped patterns may be the main cause of apparent var iations in patterns of early embryonic movements. The stereotyped patterns may represent important orderly characteristics of spontaneous embryonic ac tivities that may be involved in the development of orderly structures and functions in higher animals.