Having a vertebral column endows vertebrates with many similar characteristics and one of these is bilateral or left-right symmetry. For instance, if we draw an imaginary line dividing a vertebrate’s body from head to tail through the centre, we will see symmetrically placed eyes, limbs, etc. To ask how this symmetric body structure comes into being means going to the embryonic stage and see how the precursors of the skeleton and muscles, known as somites, develop. The question then is – does the left-right symmetry seen in the somites develop through some inbuilt mechanism of genetic regulation or is it a physical property of the tissues making up the somites? A group of researchers studying zebrafish model embryos find that it is in fact surface tension that shapes these cells and not any genetic regulatory mechanism. The results of their study are published in Nature.
“A key insight of this study is the realisation that the precise patterns we see in developing organisms are not solely due to detailed genetic regulation, but rely on very generic physical properties of tissues,” says Andrew C. Oates from the Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland, in whose lab the study was carried out, in an email to The Hindu. According to him, this has implications for understanding normal development, as well as birth deformities, and also for the precision of engineered tissues for patients from stem cells.
The group studied the development of somites in zebrafish embryos. “We were interested in understanding how a left-right symmetric muscle and skeletal system emerges from embryonic development,” says Sundar Naganathan, who was a post doc in Prof. Oates’ lab at the time the work was carried out. He is the first author of the paper. They noticed that even though at the beginning the somites are not perfectly arranged and some even violate the left–right symmetry, they eventually change shape, without a change in volume and adopt a perfectly symmetrical arrangement. The group deduces that this is surface tension at play in the tissues of the somites.
The main challenge was in imaging left and right sides of the embryo simultaneously, for which the researchers used a multi-view light-sheet microscope where the sample was rotated and imaged from multiple angles. “The second challenge was developing data analysis tools, because each movie that we acquired using the light-sheet microscope was about 500 GB in size, and we had to come up with new tools to process these large data sets,” says Dr Naganathan.
Disturbance of left–right symmetry in individuals is seen in a condition called scoliosis where the backbone gets curved , either before birth itself or later, during active development as during adolescence. Scoliosis patients show a lack of left–right symmetry in their ribs, muscle and skeleton. “Our work provides a way forward to enable a fundamental understanding of how the left and right sides of the embryo form symmetrically, which in the long-term will hopefully help us understand the etiology behind scoliosis,” says Dr. Naganathan.
- Having a vertebral column endows vertebrates with many similar characteristics and one of these is a bilateral or left–right symmetry
- For instance, if we draw an imaginary line dividing a vertebrate’s body from head to tail through the centre, we will see symmetrically placed eyes, limbs, etc
- To ask how this symmetric body structure comes into being means going to the embryonic stage and see how the precursors of the skeleton and muscles, known as somites, develop
