Source: Okayama University (JAPAN), Public Relations Division
For immediate release: 22 March 2022
Okayama University research: Understanding insect leg regeneration

(Okayama, 22 March) Researchers at Okayama University report in Development the biomolecular mechanisms underlying leg regeneration in the two-spotted cricket, an insect capable of regrowing a leg following amputation.

In organisms, tissue lost by a wound can be partially restored — and sometimes even completely. The ability to regenerate tissue varies across animal species. The regenerative abilities of humans are limited, whereas those of certain insects are such that they can regrow limbs. The latter is possible because at a wound, these insects can form a blastema, a group of special cells that can proliferate and differentiate, that is, change into different cell types. In order to better understand tissue regeneration, it is important to identify the biomolecular mechanisms that govern blastema formation. Now, Senior Lecturer BANDO Tetsuya and OKUMURA Misa (graduate students), Professor OHUCHI Hideyo from Okayama University and colleagues have performed experiments on leg regeneration in the two-spotted cricket (Gryllus bimaculatus), and found which genes and associated signaling pathways play a role in leg regrowth in this type of cricket.

The scientists first looked at the effect of amputating a leg of a two-spotted cricket on gene expression (the production of biomolecules, typically proteins, encoded in the gene). They noted that certain genes from a set known as Toll genes displayed significant upregulated expression for up to 48 hours after leg amputation. Senior Lecturer BANDO and colleagues then applied a technique called RNA interference (RNAi), a gene ‘silencing’ procedure with which the production level of biomolecules associated with a specific gene can be reduced in a controlled way. Applying RNAi targeted at various Toll genes resulted in regrown but sometimes malformed legs, showing how genes affect the phenotype — in this case, leg morphology. From these experiments, it became clear that two genes, labeled Toll2-1 and Toll2-2, play a central role in blastemal formation and leg regeneration.

Further experiments showed that Toll2-2 regulates the accumulation of so-called plasmatocytes into the blastema that forms in the wound region. Plasmatocytes are insect macrophages, cells that can ‘eat’ harmful bacteria or organisms, and as such are an important part of an insect’s immune system. Apart from neutralizing ‘intruders’, macrophages help temper inflammation reactions by releasing cytokines. The latter are relatively small proteins that play important roles in cell signaling — the collective of processes that underlies the communication between different parts of an organism. The researchers found that the Toll2-2-regulated plasmatocyte accumulation triggers, through the release of cytokines, a signaling pathway that ultimately results in the blastemal cell proliferation leading to cricket leg regeneration.

The findings of Senior Lecturer BANDO and colleagues regarding the two-spotted cricket are relevant for the wider class of hemimetabolous insects (insects that do not have a pupal stage in their development, but rather transform gradually from egg to nymph to adult.) Quoting the scientists: “this study provides new insights into the function of Toll-related signaling for leg regeneration via plasmatocytes.”

Background
Regeneration: Biological regeneration refers to the process of restoring damaged or lost tissue. It makes individual cells and whole organisms resilient to natural perturbations or wounding. All species, from bacteria to humans, are capable of regeneration, but to different extents — regeneration can be complete or incomplete. Among the vertebrates, newts and salamanders have high regeneration capabilities; they can indeed regenerate various body parts including eyes, jaws, limbs and tails. Insects also display regeneration; the class of hemimetabolous insects (not undergoing a pupal stage during development) can regrow limbs, but only until the final molt (molting refers to the casting off of an outer layer during development). Senior Lecturer BANDO Tetsuya from Okayama University and colleagues have now investigated limb regeneration in the two-spotted cricket, and identified the genes and the signaling pathways that promote leg regeneration in this type of hemimetabolous insect.

Reference
Tetsuya Bando, Misa Okumura, Yuki Bando, Marou Hagiwara, Yoshimasa Hamada, Yoshiyasu Ishimaru, Taro Mito, Eri Kawaguchi, Takeshi Inoue, Kiyokazu Agata, Sumihare Noji, Hideyo Ohuchi. Toll signalling promotes blastema cell proliferation during cricket leg regeneration via insect macrophages. Development. 2022, 149 (8): dev199916.
DOI：10.1242/dev.199916
https://journals.biologists.com/dev/article-abstract/149/8/dev199916/273331/Toll-signalling-promotes-blastema-cell?redirectedFrom=fulltext

Correspondence to
Senior Lecturer BANDO Tetsuya, Ph.D.
Department of Cytology and Histology,
Graduate School of Medicine, Dentistry and Pharmaceutical
Sciences, Okayama University, 2-5-1, Shikata-cho, Kita-ku,
Okayama 700-8558, Japan
E-mail: tbando@cc.okayama-u.ac.jp
//www.okayama-u.ac.jp/user/anatomy1/index-en.html

Further information
Okayama University
1-1-1 Tsushima-naka , Kita-ku , Okayama 700-8530, Japan
Public Relations Division
E-mail: www-adm(a) adm.okayama-u.ac.jp
For inquiries, please contact us by replacing (a) with the @ mark.
Website: //www.okayama-u.ac.jp/index_e.html
Okayama Univ. e-Bulletin: //www.okayama-u.ac.jp/user/kouhou/ebulletin/
We love OKAYAMA UNIVERSITY: https://www.youtube.com/watch?v=7cXlttQIk3E
Okayama University Image Movie（2020）
https://www.youtube.com/watch?v=BKRoF0tffmA
Okayama University supports the Sustainable Development Goals: https://sdgs.okayama-u.ac.jp/en/

The whole volume : OU-MRU (1- )
Vol.1：Innovative non-invasive ‘liquid biopsy’ method to capture circulating tumor cells from blood samples for genetic testing
Vol.2：Ensuring a cool recovery from cardiac arrest
Vol.3：Organ regeneration research leaps forward
Vol.4：Cardiac mechanosensitive integrator
Vol.5：Cell injections get to the heart of congenital defects
Vol.6：Fourth key molecule identified in bone development
Vol.7：Anticancer virus solution provides an alternative to surgery
Vol.8：Light-responsive dye stimulates sight in genetically blind patients
Vol.9：Diabetes drug helps towards immunity against cancer
Vol.10：Enzyme-inhibitors treat drug-resistant epilepsy
Vol.11：Compound-protein combination shows promise for arthritis treatment
Vol.12：Molecular features of the circadian clock system in fruit flies
Vol.13：Peptide directs artificial tissue growth
Vol.14：Simplified boron compound may treat brain tumours
Vol.15：Metamaterial absorbers for infrared inspection technologies
Vol.16：Epigenetics research traces how crickets restore lost limbs
Vol.17：Cell research shows pathway for suppressing hepatitis B virus
Vol.18：Therapeutic protein targets liver disease
Vol.19：Study links signalling protein to osteoarthritis
Vol.20：Lack of enzyme promotes fatty liver disease in thin patients
Vol.21：Combined gene transduction and light therapy targets gastric cancer
Vol.22：Medical supportive device for hemodialysis catheter puncture
Vol.23：Development of low cost oral inactivated vaccines for dysentery
Vol.24：Sticky molecules to tackle obesity and diabetes
Vol.25：Self-administered aroma foot massage may reduce symptoms of anxiety
Vol.26：Protein for preventing heart failure
Vol.27：Keeping cells in shape to fight sepsis
Vol.28：Viral-based therapy for bone cancer
Vol.29：Photoreactive compound allows protein synthesis control with light
Vol.30：Cancer stem cells’ role in tumor growth revealed
Vol.31：Prevention of RNA virus replication
Vol.32：Enzyme target for slowing bladder cancer invasion
Vol.33：Attacking tumors from the inside
Vol.34：Novel mouse model for studying pancreatic cancer
Vol.35：Potential cause of Lafora disease revealed
Vol.36：Overloading of protein localization triggers cellular defects
Vol.37：Protein dosage compensation mechanism unravelled
Vol.38：Bioengineered tooth restoration in a large mammal
Vol.39：Successful test of retinal prosthesis implanted in rats
Vol.40：Antibodies prolong seizure latency in epileptic mice
Vol.41：Inorganic biomaterials for soft-tissue adhesion
Vol.42：Potential drug for treating chronic pain with few side effects
Vol.43：Potential origin of cancer-associated cells revealed
Vol.44：Protection from plant extracts
Vol.45：Link between biological-clock disturbance and brain dysfunction uncovered
Vol.46：New method for suppressing lung cancer oncogene
Vol.47：Candidate genes for eye misalignment identified
Vol.48：Nanotechnology-based approach to cancer virotherapy
Vol.49：Cell membrane as material for bone formation
Vol.50：Iron removal as a potential cancer therapy
Vol.51：Potential of 3D nanoenvironments for experimental cancer
Vol.52：A protein found on the surface of cells plays an integral role in tumor growth and sustenance
Vol.53：Successful implantation and testing of retinal prosthesis in monkey eyes with retinal degeneration
Vol.54：Measuring ion concentration in solutions for clinical and environmental research
Vol.55：Diabetic kidney disease: new biomarkers improve the prediction of the renal prognosis
Vol.56：New device for assisting accurate hemodialysis catheter placement
Vol.57：Possible link between excess chewing muscle activity and dental disease
Vol.58：Insights into mechanisms governing the resistance to the anti-cancer medication cetuximab
Vol.59：Role of commensal flora in periodontal immune response investigated
Vol.60：Role of commensal microbiota in bone remodeling
Vol.61：Mechanical stress affects normal bone development
Vol.62：3D tissue model offers insights into treating pancreatic cancer
Vol.63：Promising biomarker for vascular disease relapse revealed
Vol.64：Inflammation in the brain enhances the side-effects of hypnotic medication
Vol.65：Game changer: How do bacteria play Tag ?
Vol.66：Is too much protein a bad thing?
Vol.67：Technology to rapidly detect cancer markers for cancer diagnosis
Vol.68：Improving the diagnosis of pancreatic cancer
Vol.69：Early gastric cancer endoscopic diagnosis system using artificial intelligence
Vol.70：Prosthetics for Retinal Stimulation
Vol.71：The nervous system can contribute to breast cancer progression
Vol.72：Synthetic compound provides fast screening for potential drugs
Vol.73：Primary intraocular lymphoma does not always spread to the central nervous system
Vol.74：Rising from the ashes—dead brain cells can be regenerated after traumatic injury
Vol.75：More than just daily supplements — herbal medicines can treat stomach disorders
Vol.76：The molecular pathogenesis of muscular dystrophy-associated cardiomyopathy
Vol.77：Green leafy vegetables contain a compound which can fight cancer cells
Vol.78：Disrupting blood supply to tumors as a new strategy to treat oral cancer
Vol.79：Novel blood-based markers to detect Alzheimer’s disease
Vol.80：A novel 3D cell culture model sheds light on the mechanisms driving fibrosis in pancreatic cancer
Vol.81：Innovative method for determining carcinogenicity of chemicals using iPS cells
Vol.82：Making memories — the workings of a neuron revealed
Vol.83：Skipping a beat — a novel method to study heart attacks
Vol.84：Friend to Foe—When Harmless Bacteria Turn Toxic
Vol.85：Promising imaging method for the early detection of dental caries
Vol.86：Plates and belts — a toolkit to prevent accidental falls during invasive vascular proceduresa
Vol.87：Therapeutic potential of stem cells for treating neurodegenerative disease
Vol.88：Nanotechnology for making cancer drugs more accessible to the brain
Vol.89：Studying Parkinson’s disease with face-recognition software
Vol.90：High levels of television exposure affect visual acuity in children
Vol.91：Meeting high demand: Increasing the efficiency of antiviral drug production in bacteria
Vol.92：Numerical modelling to assist the development of a retinal prosthesis
Vol.93：Repurposing cancer drugs: An innovative therapeutic strategy to fight bone cancer
Vol.94：A berry vine found in Asia proves useful in combating lung cancer
Vol.95：A new avenue for detecting cancer in the blood
Vol.96：Automated cell image analysis
Vol.97：Artificial intelligence helps to determine cancer invasion
Vol.98：Okayama University launches clinical trials of a jawbone regeneration therapy using human BMP-2 transgenic protein derived from Escherichia coli.
Vol.99：A rapid flow process that can convert droplets into multilayer polymeric microcapsules