Throughout this discovery process there have been many questions that have guided the scientific community towards finding answers. One of the earlier questions was “how does the embryo take form and differentiate to become an organised organism?”
This question began to be answered in 1924, when H Spermann and H mangold published a paper describing their experimentation with newt embryos. They discovered that by taking the dorsal lip and transferring it to the ventral side of a new embryo; it would form a new embryonic axis by instructing surrounding cells to undergo neutralisation and dorsalisation alongside a pre-existing embryo (Spermann & Mangold, 1924). The reason this had such large ...view middle of the document...
It was discovered that lefty contained two closely related genes on the same locus- lefty 1 and lefty 2 (Meno & Saijoh et al, 1995). This was achieved by undertaking a whole mount in situ hybridisation of mice embryos at the 6.0-9.5 d.p.c stage (Meno & Saijoh et al, 1995). In doing so they were able to discover the role lefty plays in left right asymmetry
Nobutaka Hirokawa 1998
They were able to prove that the motile cilia in the node where in fact motile through the use of electron microscopy and show the cilia beating the extra-embryonic fluid in a leftward direction, which they named the nodal flow (Nonaka & Tanaka, 1998). Furthermore, they were able to emphasise the important role of KIF3B in L-R determination (Nonaka & Tanaka, 1998). A number of methods were used to show this discovery. Embryos were analysed during a whole mount in situ hybridisation, and also by histological techniques (Nonaka & Tanaka, 1998). To view the nodal cilia, fluorescent microscopy using a confocal laser microscope, and immunoelectron microscopy using electron microscopy was used without electron staining (Nonaka & Tanaka, 1998). Electron microscopy was also used with electron staining to view the embryo (Nonaka & Tanaka, 1998). Fluorescent latex beads were used to visualise nodal flow, and the image was projected to a camera, where the fluoresced beads could highlight the nodal flow and differentiate it from all other structures (Nonaka & Tanaka, 1998). By comparing wild type mice with KIF3B-deficient mice that lacked nodal cilia, they were able to show the importance of the motile cilia, and that the initial break in symmetry appeared to be when the cilia created the leftward flow of nodal (Nonaka & Tanaka, 1998).
2002 Determination of left–right patterning of the mouse embryo by artificial nodal flow
Were able to impose an articifial flow of nodal on the embryo in the opposite direction and discovered situs inversus occurred. [METHOD AND THE REST OF THE PARAGRAGH]
Tabin and Vogan in 2003 were able to show that there is 2 types of cilia present on the node. The first being motile cilia that beat chemicals and generate a leftward flow. The second is immotile cilia, which was hypothesised to have a mechnosensory role. [METHOD AND THE REST OF THE PARAGRAGH]
Discovered that the cilia move in a clockwise motion, consisting of a power stroke and recovery stroke. The importance of this study was the finding of the cilia generating the leftward flow. Therefore the leftward flow doesn’t give the cilia a posterior tilt, and the cilia are the start of the symmetry breaking. [METHOD AND THE REST OF THE PARAGRAGH]
Were able to demonstrate that the cilia have a posterior tilt, and that most of the cilia appear to be located on the posterior portion of the node. [METHOD AND THE REST OF THE PARAGRAGH]
In 2010 it was obvious that cilia played an important role in the node. It was at this time that Hashimoto and Shinohara et al decided to...