Transitions are a hallmark of life. When dormant plants bloom in spring or when a young adult turns out on their own, there is a shift in control. Similarly, there is a transition during early development when an embryo undergoes biochemical changes that shift from being controlled by parent molecules to being controlled by its own genome. For the first time, a team from the Perelman School of Medicine at the University of Pennsylvania found in an embryo that activation of its genome does not occur at once, but instead follows a specific pattern primarily governed by the different sizes of its cells. . The researchers published their findings this week as the cover story in Developmental Cell .
In an early embryo undergoing cell division, maternally charged RNA and proteins regulate the cell cycle. The genes of the zygotes ̵
"How an embryo delivers" control of mother development to zygote is a fundamental issue in developmental biology, "said senior author Matthew C. Good, Ph.D., an assistant professor of cell and developmental biology and biotechnology." It has not been appreciated that different regions of a vertebrate embryo may undergo genomic activation at different times, or where direct cell size regulates the awakening of a zygote genome. "
Various hypotheses have been offered over the past 40 years to explain how embryo distinguishes when to activate the new genome of the individual cells within the zygote, but it was the Penn team that nailed the mechanism and responded to this key problem.
Use of single cell imaging of African globe seed Xenopus laevis) they said that cell size was the key parameter for the onset of activation in zygotes. drying to initiate large-scale transcription of their own proteins. By generating miniature embryos, the team showed that changes in cell size control the timing of activation.
The results of this study have a number of important implications for the basic understanding of how an embryo develops in its early days and for the field of developmental biology in general. The Penn team believes that this finding could affect how other investigators approach their own research through activation and screening for maternal factors needed to control the belief in early embryonic development.
"To gain new insight, zygotic transcription must be measured to a single cell level," said first author Hui Chen, Ph.D., a postdoctoral fellow in Good's lab. "This approach helped us not to overlook the influence of an embryonic cells spatially organizing on the maternal-zygotic transition."
The decision to initiate the zygote genome is made at the level of individual cells, not whole embryos, which have changed the Penn team's view of the development process. "Evolution has co-occupied cell size as a regulatory mechanism to control a critical transition in embryonic development, a paradigm that can extend to other areas of biology where cell size varies," Good said. He and Chen plan to continue this work by measuring by activation in zebrafish and mice to see if this new perspective applies to other species.
Tracking the first step of life: Two molecules & # 39; awaken & # 39; brand new genome
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