Interpreting Science - Frontier! Can the cut-off eye regenerate? True vortex is a magical creature!

Wang Sizhen is responsible for exploring the mysteries of neuroscience with rigorous academic logic thinking. At present, there are many advanced technologies that can accurately present the developmental neuron circuit [1]."guidepost cells" are a kind of special cells that exist briefly in the process of embryonic development. They can be used as intermediate guidance targets of axons, or as scaffolds to promote axon targeting [2].studies have shown that once the loop is formed, most of the steering mechanisms become unnecessary [3].however, some animals can regenerate their nervous system [4].therefore, to some extent, the lack of guidance mechanism limits the regeneration of neuronal patterns.planarian is a kind of planarian belonging to the three intestinal order of planarian.living in fresh water, asexual reproduction is carried out in summer with high water temperature, and transverse division is conducted in front or back of pharynx.sexual reproduction was performed from late autumn to winter and spring.oocysts 2-2.5mm.dark brown or tea brown.the body color is light brown on the back, often mixed with reddish brown and yellow green; the pharynx and genitalia are light.body length: 20-35mm, width: 2.5-4mm.the ability of regeneration and starvation tolerance is very strong.carnivorous, widely distributed in China: clear fresh water ponds and rocks formed by springs in Northeast, North and South China can be harvested [5-6].(photo quoted from:), scientists at the University of Nottingham, UK, discovered that planarian worms have a unique ability to regenerate body parts, including the head and brain, after being cut off.they contain mature stem cells, which often divide into all types of cells that are missing from the body [7].in addition, researchers from Tufts University in the United States also found that not only can a true planarian regenerate a head after its head is cut off, but the regenerated head also contains the same memory as the cut off head [8]. so far, it is not difficult for us to know that the true planarian is a kind of magical creature! It not only has the ability to regenerate a head, but also has a new head. then, if the eyes of a true planarian are cut off, will they also grow new eyes? Or even, will the new eyes retain the memory of the past? Professor Peter w. reddien of Howard Hughes Medical School of Massachusetts Institute of Technology (MIT) has long used molecular genetic techniques (such as RNA interference) to study tissue regeneration (including stem cells with regenerative ability and regeneration regulatory genes) in animals (such as true planarian). their relevant evidence and opinions show that some adult animals (including the true planarian worm) have the ability to regenerate functional neuronal circuits. therefore, these animals must have the mechanism of repairing the neuronal pattern. was published online in science on June 26, 2020 under the title of "muscle and neural guide post like cells facility planar visual system regeneration". The laboratory aims to describe the mechanism of this neuronal pattern repair (or regeneration) by studying the regeneration of the visual system of different damaged true planarians. first of all, by using fluorescence in situ hybridization (FISH), we found a rare subgroup of muscle cells, namely notum +; frizzled 5 / 8-4 +), hereinafter referred to as NMCS. the first group of these cells near the eye, where the visual axons project and form a bundle. the second group of cells was located near the selection point, where the contralateral and ipsilateral axons were classified. both groups of muscle cells are formed during the regeneration of the visual system and are always closely related to axon projection, which is consistent with the potential role of promoting the assembly of the visual system. in addition, we found that a group of dorsal positive neurons located at the junction of the forebrain in adults regenerate before the axonal midline crossing, which is related to the regeneration of optic chiasm. visual axon / photoreceptor neurons (cyan) and landmark cells (purple red) (photo Citation:) in view of the above interesting findings, the first big question the author wants to explore in depth is: do these NMCS affect the distribution of new neurons? First of all, the results showed that the eyes transplanted to the ectopic anatomical position did not form NMCS; at the same time, the authors conducted RNA interference on the eggs of planarians to prevent them from producing eyes, and further found that these planarians could still form NMCS in the correct position. therefore, these results confirm the author's conjecture: if the photoreceptor axon related NMCS have the function of "landmark like", then the formation of NMCS is independent of eye cells. secondly, the authors further found that axons of new eyes project (/ extend) to NMCS, and when axons and NMCS meet, their trajectories will be adjusted and correlated. this confirms another conjecture of the authors: if these special muscle cells, namely NMCS, are indeed some kind of guiding cells, then when the new eye is transplanted into the head of the excised eye, the visual axon trajectory should be associated with the NMCS trajectory. that is to say, when the eyes of one planarian worm are transplanted into the head of another, these new eyes will stretch out neurons towards the NMCS, and adjust the forward direction after contacting these muscle cells, and finally connect with the brain to perform normal visual function. however, when the eyes were transplanted to other body parts of the planarian worm lacking NMCS, the photoreceptor neurons could not be associated with the brain. similarly, similar results can be obtained if NMCS are removed before eye transplantation. the "landmark cells" of euplanaria control regeneration (photo: M. Lucila scimone, et al., science, 2020; 368) the above results suggest that NMCS do affect (/ Guide) the distribution of newborn neurons. the second big question is: where does NMC come from? Further results show that some special signal molecules are secreted in muscle, which can indicate the precise location of the guide cells, that is, to indicate where the guide cells go. if these signal molecules are disturbed, the guide cells will not be able to locate in the correct position and go to the wrong position, and at the same time, it will also direct the nerve to the wrong position. therefore, these results suggest that NMC originates from muscle, and also suggests that there is a set of visual system extracellular mechanism in adults, which can guide the localization of "landmark cells". finally, through single cell RNA sequencing and fluorescence in situ hybridization screening, the authors identified the related molecules and transcription factors expressed in NMCS. RNA interference can reduce or eliminate the muscle or nerve "landmark cell" subsets, and then lead to abnormal axonal trajectory. adult "landmark cells" promote the regeneration of planarian visual system (photo: M. Lucila scimone, et al., science, 2020; 368) conclusion in the absence of embryos, if the adult neuronal model is to be regenerated, the relevant molecular and cellular strategies must overcome the difficulties: damage or loss after injury. therefore, understanding these mechanisms may provide important basis and insights for regenerative medicine. the research team of Professor Peter w. reddien showed that the special "landmark cells" existing in adults can guide the formation and location of transplanted visual system, and promote the regeneration of normal visual system of planarian. [1] D. L. Chao, L. Ma, K. Shen, NAT. Rev. Neurosci.10, 262 (2009). [2] C. M. bate, nature 260, 54 (1976) [3] M. L. scientone et al., science 368, eaba3203 (2020) [2020]. [4] J. n. witcheley, M. Mayer, D. E. Wagner, J. h. Owen, P. w. reddien, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, cell, rep.4, [5] Tang Tao, Zhou Mingcheng, editor in chief, in animal dictionary, remote publishing house, 2005.01, page 180 [6] sluys, R.; Kawakatsu, M.; riuport, M.; Bagu nin224, J. (2009). A new higher classification of planar flowers (Platyhelminthes, tricladidad). Journal of natural history.43 (29-30): 1763 – 1777. [7] Daniel A. Felix, A. Aziz abobaboobaker, N., A. Felix, A. Aziz abobaboobaker,it's a good idea, PLoS Genetics (2010) [8] tal shomrat, Michael Levin, Journal of empirical biology, 216 (2013)