Understanding embryonic protein production
For an embryo to develop properly, it must produce proteins at the right time and place. This is determined by translation, the final step of gene expression – the process through which a gene uses its information to produce proteins. Scientists have learned much about other steps of gene expression during embryonic development. Yet much less is known about when and where proteins are actually produced, due to the challenge of measuring translation at sufficient spatial and temporal resolution in living vertebrate embryos. “To fully understand how an embryo develops, we therefore need to observe protein production directly,” says Maëlle Bellec(opens in new window), postdoctoral fellow at the Max Planck Institute for Heart and Lung Research(opens in new window). Through the LivAdapt project, which was funded by the Marie Skłodowska-Curie Actions(opens in new window) programme, Bellec and her colleagues combined genome engineering with a suite of imaging and analytical techniques to directly visualise translation in living zebra fish embryos(opens in new window). “Our findings open up the possibility of studying this additional layer of gene regulation directly in live vertebrate embryos,” adds Bellec. “From a biological perspective, this provides a missing layer of information that links gene expression to protein production and developmental outcomes.”
Fluorescent protein labelling
The project focused on a specific molecule known as a morphogen, which provides signals to embryonic cells that will shape the structure of an organism. Morphogens help with the development of the spinal cord and limbs, for example, or with the development of wings in insects. LivAdapt focused on BMP2b, a morphogen that plays a key role in establishing the body plan during early development. The researchers used genome engineering to introduce a tag into the BMP2b gene, so they could fluorescently label nascent proteins as they were being synthesised. They combined this with live lattice light-sheet microscopy, a state-of-the-art imaging technology, to image protein synthesis throughout the embryo. In parallel, they integrated a range of complementary imaging and modelling approaches. “Together, these methods allowed us to quantify translation dynamics at the level of individual mRNAs(opens in new window) and cells, revealing when, where and how efficiently BMP2b is translated during early embryonic development,” explains Bellec.
Unprecedented detail into protein production
One of the most important findings was that translation of BMP2b is primarily regulated at the level of translation initiation, revealing an additional layer of control over protein production. The team also found that BMP2b translation can occur through multiple pathways, suggesting developing embryos can use different strategies to ensure proteins are created. “We hope this work will help the scientific community gain a more complete understanding of how embryos develop,” remarks Bellec. Beyond these biological insights, the technology developed in LivAdapt can be adapted to study other genes, Bellec adds, allowing scientists to investigate how protein synthesis is regulated during different developmental processes.
Broader biomedical implications
A better understanding of translational regulation may also have broader biomedical implications, the team suggests. “Many developmental disorders and other diseases are associated with defects in protein synthesis or its regulation,” notes Bellec. “By studying how translation is controlled in the context of normal development, our work may help provide a framework for understanding how these processes become disrupted in disease.” Bellec will continue the research at her new position in Montpellier, France, building on the potential of the technology demonstrated in the project. “I now plan to apply it to a broader range of genes and developmental processes,” she says.
