Chemical genetics of regeneration: Contrasting temporal effects of CoCl2 on axolotl tail regeneration.

BACKGROUND: Histone deacetylases (HDACs) regulate transcriptional responses to injury stimuli that are critical for successful tissue regeneration. Previously we showed that HDAC inhibitor romidepsin potently inhibits axolotl tail regeneration when applied for only 1-minute postamputation (MPA). RESULTS: Here we tested CoCl2, a chemical that induces hypoxia and cellular stress, for potential to reverse romidepsin inhibition of tail regeneration. Partial rescue of regeneration was observed among embryos co-treated with romidepsin and CoCl2 for 1 MPA, however, extending the CoCl2 dosage window either inhibited regeneration (CoCl2 :0 to 30 MPA) or was lethal (CoCl2 :0 to 24 hours postamputation; HPA). CoCl2 :0 to 30 MPA caused tissue damage, tissue loss, and cell death at the distal tail tip, while CoCl2 treatment of non-amputated embryos or CoCl2 :60 to 90 MPA treatment after re-epithelialization did not inhibit tail regeneration. CoCl2 -romidepsin:1 MPA treatment partially restored expression of transcription factors that are typical of appendage regeneration, while CoCl2 :0 to 30 MPA significantly increased expression of genes associated with cell stress and inflammation. Additional experiments showed that CoCl2 :0 to 1 MPA and CoCl2 :0 to 30 MPA significantly increased levels of glutathione and reactive oxygen species, respectively. CONCLUSION: Our study identifies a temporal window from tail amputation to re-epithelialization, within which injury activated cells are highly sensitive to CoCl2 perturbation of redox homeostasis.

HDAC Regulates Transcription at the Outset of Axolotl Tail Regeneration.

Tissue regeneration is associated with complex changes in gene expression and post-translational modifications of proteins, including transcription factors and histones that comprise chromatin. We tested 172 compounds designed to target epigenetic mechanisms in an axolotl (Ambystoma mexicanum) embryo tail regeneration assay. A relatively large number of compounds (N = 55) inhibited tail regeneration, including 18 histone deacetylase inhibitors (HDACi). In particular, romidepsin, an FDA-approved anticancer drug, potently inhibited tail regeneration when embryos were treated continuously for 7 days. Additional experiments revealed that romidepsin acted within a very narrow, post-injury window. Romidepsin treatment for only 1-minute post amputation inhibited regeneration through the first 7 days, however after this time, regeneration commenced with variable outgrowth of tailfin tissue and abnormal patterning. Microarray analysis showed that romidepsin altered early, transcriptional responses at 3 and 6-hour post-amputation, especially targeting genes that are implicated in tumor cell death, as well as genes that function in the regulation of transcription, cell differentiation, cell proliferation, pattern specification, and tissue morphogenesis. Our results show that HDAC activity is required at the time of tail amputation to regulate the initial transcriptional response to injury and regeneration.

Sal-Site: research resources for the Mexican axolotl.

Sal-Site serves axolotl research efforts by providing Web access to genomic data and information, and living stocks that are reared and made available by the Ambystoma Genetic Stock Center (AGSC). In this chapter, we detail how investigators can search for genes of interest among Sal-Site resources to identify orthologous nucleotide and protein-coding sequences, determine genome positions within the Ambystoma meiotic map, and obtain estimates of gene expression. In the near future, additional genomic resources will be made available for the axolotl, including a listing of genes that are partially or wholly contained within Bacterial Artificial Chromosome (BAC) vectors, a prioritized collection of deeply sequenced BAC clones, chromosome-specific assemblies of genomic DNA, and transgenic axolotls that are engineered using TALENs and CRISPRs. Also, services provided by the AGSC will be expanded to include microinjection of user constructs into single cell embryos and distribution of axolotl tissues, DNA, and RNA. In conclusion, Sal-Site is a useful resource that generates, shares, and evolves Ambystoma associated information and databases to serve research and education.

Thujone corrects cholesterol and triglyceride profiles in diabetic rat model.

Thujone, which is the major constituent in Salvia sp. (Lamiaceae), was found to correct the lipid profile (cholesterol and triglycerides) in diabetic rats. Oral treatment with thujone (5 mg kg⁻¹ body weight dose) significantly adjusted cholesterol and triglyceride levels in diabetic rats (p ≤ 0.05) to normal levels compared to diabetic untreated rats. This provides a premise in the field of finding new agents to treat diabetic complications.