Biology subjects

Rojas, S.

Publications and source records attributed to Rojas, S..

4 recordsLinked to original sources

bioRxiv2024

Planarians Develop Radiotolerance to Recurrent Ionizing Radiation Exposure

Exposure to ionizing radiation can induce DNA fragmentation, leading to double-strand breaks, the most toxic form of DNA damage. Some organisms have developed mechanisms to overcome the adverse effects of ionizing radiation by enhancing DNA protection and repair. However, the underlying mechanisms driving radiation resistance to maintain genomic integrity and function remain poorly understood. Here, we provide evidence for the development of radiotolerance in the flatworm planarian Schmidtea mediterranea. We implemented a strategy to select animals capable of overcoming repeated rounds of ionizing radiation exposure. We demonstrate that planarians initially exposed to higher amounts of sub-lethal radiation can adapt, gaining the ability to recover reproductive capabilities faster than animals initially exposed to lower amounts of sub-lethal radiation. Our findings show that DNA integrity is reestablished in about one week after five cycles of sub-lethal ionizing radiation exposure. Planarian stem cells, known as neoblasts, can repair repeated DNA double-strand breaks by activating Rad51-mediated homologous recombination. The expression of the neoblast marker smedpiwi-1 and the mitotic activity reach levels similar to unirradiated animals between two and three weeks post-radiation. We describe that planarians develop radiotolerance through recurrent ionizing radiation exposure over several years and survive without apparent functional or morphological defects for an undetermined time.

developmental biology↗

bioRxiv2024

The DNA Methyltransferase DMAP1 is Required for Tissue Maintenance and Planarian Regeneration

The precise regulation of transcription is required for embryonic development, adult tissue turnover, and regeneration. Epigenetic modifications play a crucial role in orchestrating and regulating the transcription of genes. These modifications are important in the transition of pluripotent stem cells and their progeny. Methylation, a key epigenetic modification, influences gene expression through changes in histone tails and direct DNA methylation. Work in different organisms has shown that the DNA methyltransferase-1-associated protein (DMAP1) may associate with other molecules to repress transcription through DNA methylation. Thus, DMAP1 is a versatile protein implicated in a myriad of events, including pluripotency maintenance, DNA damage repair, and tumor suppression. While DMAP1 has been extensively studied in vitro, its complex regulation in the context of the adult organism remains unclear. To gain insights into the possible roles of DMAP1 at the organismal level, we used planarian flatworms that possess remarkable regenerative capabilities driven by pluripotent stem cells called neoblast. Our findings demonstrate the evolutionary conservation of DMAP1 in the planarian Schmidtea mediterranea. Functional disruption of DMAP1 through RNA interference revealed its critical role in tissue maintenance, neoblast differentiation, and regeneration in S. mediterranea. Moreover, our analysis unveiled a novel function for DMAP1 in regulating cell death in response to DNA damage and influencing the expression of axial polarity markers. Our findings provide a simplified paradigm for studying DMAP1s epigenetic regulation in adult tissues. HighlightsO_LIEpigenetic regulation through DMAP1 is evolutionarily conserved in Schmidtea mediterranea and is crucial for tissue maintenance and regeneration. C_LIO_LINeoblast differentiation into epithelial, muscle, digestive, and neural fate requires DMAP1. C_LIO_LIDMAP1 regulates DNA stability and cell death during adult cell turnover. C_LIO_LIDMAP1 regulates the spatial expression of axial polarity markers in S. mediterranea. C_LI

developmental biology↗

bioRxiv2023

Cultural use of tropane alkaloids of Brugmansia species and cultivars in Colombia depends on local plant growth environment rather than genetic diversity

Borracheros or Angel Trumpets (Brugmansia spp.) of the Solanaceae plant family are known for producing scopolamine and other tropane alkaloids and are widely used by indigenous communities in the Andes for medicinal and ritual purposes. Growing different varieties has increased the popularity of Brugmansia species in recent years, leading to the promotion of hybridization to get new morphotypes. However, so far no medical or cultural use of plant extracts could be linked to selected Brugmansia species or cultivars. Moreover, until now there is only limited knowledge about the effect of hybridization on tropane alkaloid contents and/or diversity of Brugmansia species or cultivars. Here, a liquid chromatography-mass spectrometry (LC-MS) approach was applied to identify and characterize secondary metabolite contents in various Brugmansia species and hybrids from different geographic origins in Colombia. The analysis of the metabolic data sets revealed that tropane alkaloids and other secondary metabolites accumulate in a leaf and flower specific manner. Although some minor differences were found between Brugmansia subgroups, the only significant difference exists between plants collected in the Sibundoy Valley, where they have been domesticated by indigenous communities since a long time and those, which so far have not been used by humans at all. The different genetic constitutions of Brugmancia species and cultivars are not the dominating reason for their differences in tropane alkaloid contents and medical and cultural usages, as there is no clear taxonomical signature based on the metabolite properties for species segregation. Instead, their use by indigenous communities during ceremonies and for medical treatment such as wound healing, infection control, rheumatism and arthritis is rather caused by the plasticity of the individual plants to react to the local abiotic and biotic environments by the variation of secondary metabolite composition and by the differences in the bioavailability of the active compounds as result of the extraction method.

plant biology↗

bioRxiv2021

Restoration of DNA Integrity and Cell Cycle by Electric Stimulation in Planarian Tissues Damaged by Ionizing Radiation

Exposure to high levels of ionizing {gamma}-radiation leads to irreversible DNA damage and cell death. Here, we establish that exogenous application of electric stimulation enables cellular plasticity to reestablish stem cell activity in tissues damaged by ionizing radiation. We show that sub-threshold direct current stimulation (DCS) rapidly restores pluripotent stem cell populations previously eliminated by lethally {gamma}-irradiated tissues of the planarian flatworm Schmidtea mediterranea. Our findings reveal that DCS enhances DNA repair, transcriptional activity, and cell cycle entry in post-mitotic cells. These responses involve rapid increases in cytosolic [Ca2+] through the activation of L-type Cav channels and intracellular Ca2+ stores leading to the activation of immediate early genes and ectopic expression of stem cell markers in postmitotic cells. Overall, we show the potential of electric current stimulation to reverse damaging effects of high dose {gamma}-radiation in adult tissues. Furthermore, our results provide mechanistic insights describing how electric stimulation effectively translates into molecular responses capable of regulating fundamental cellular functions without the need for genetic or pharmacological intervention.

developmental biology↗