Biology subjects

Ramirez, M. I.

Publications and source records attributed to Ramirez, M. I..

4 recordsLinked to original sources

bioRxiv2026

Seasonal blood-brain barrier plasticity links environmental cues to migratory behavior in monarch butterflies

Seasonal migration requires animals to reversibly switch behavioral states in response to environmental cues, yet the molecular and cellular mechanisms underlying these transitions remain poorly understood. Monarch butterflies provide a powerful model, as Eastern North American populations undergo a long-distance southward migration in the fall followed by a cold-dependent reversal in flight orientation after overwintering each spring. Here, we show that cold exposure induces coordinated transcriptional changes in the monarch brain, marked by attenuated integrin-mediated extracellular matrix (ECM) signaling at the blood-brain barrier (BBB). Cold-exposed monarchs exhibit increased penetration of fluorescent markers into the brain, consistent with increased BBB permeability. Notably, our findings align with previous genomic evidence identifying collagen type IV alpha 1, a major ECM component, as a locus under divergent selection between migratory and non-migratory populations. Together, these results implicate seasonal modulation of BBB permeability as a mechanism linking environmental temperature to plastic migratory behavior and identify the BBB as a dynamic interface through which seasonal cues may reprogram neural function and behavior.

neuroscience↗

bioRxiv2023

Extracellular vesicle-localized miR-203 mediates neural crest-placode communication required for trigeminal ganglia formation

While interactions between neural crest and placode cells are critical for the proper formation of the trigeminal ganglion, the mechanisms underlying this process remain largely uncharacterized. Here, we show that the microRNA-(miR)203, whose epigenetic repression is required for neural crest migration, is reactivated in coalescing and condensing trigeminal ganglion cells. Overexpression of miR-203 induces ectopic coalescence of neural crest cells and increases ganglion size. Reciprocally, loss of miR-203 function in placode, but not neural crest, cells perturbs trigeminal ganglion condensation. Demonstrating intercellular communication, overexpression of miR-203 in the neural crest in vitro or in vivo represses a miR-responsive sensor in placode cells. Moreover, neural crest-secreted extracellular vesicles (EVs), visualized using pHluorin-CD63 vector, become incorporated into the cytoplasm of placode cells. Finally, RT-PCR analysis shows that small EVs isolated from condensing trigeminal ganglia are selectively loaded with miR-203. Together, our findings reveal a critical role in vivo for neural crest-placode communication mediated by sEVs and their selective microRNA cargo for proper trigeminal ganglion formation. SIGNIFICANCE STRATEMENTCellular communication during early development plays a critical role. In this study, we demonstrate a unique role for a microRNA in cell-cell communication between the neural crest (NC) and placode cells (PC) during trigeminal ganglia (TG) formation. By utilizing loss and gain of function experiments in vivo, we demonstrate a requirement for miR-203 during cellular condensation to form the TG. We revealed that NC produces extracellular vesicles, selectively carrying miR-203, which is then taken up by the PC and regulates a sensor vector exclusively expressed in the placode. Taken together, our findings reveal a critical role in TG condensation for miR-203, produced by post-migratory NC and taken up by PC via extracellular vesicles.

developmental biology↗

bioRxiv2020

Active learning tools improve the learning outcomes, scientific attitude and critical thinking in higher education: Experiences in an online course during the COVID-19 pandemic

Active teaching methodologies have been placed as a hope for changing education at different levels, transiting from passive lecture-centered to student-centered learning. With the health measures of social distance, the COVID-19 pandemic forced a strong shift to remote education. With the challenge of delivering quality education through a computer screen, we validated and applied an online course model using active teaching tools for higher education. We incorporated published active-learning strategies into an online construct, with problem-based inquiry and design of inquiry research projects to serve as our core active-learning tool. The gains related to students science learning experiences and their attitudes towards science were assessed by applying questionnaires before, during and after the course. The course counted on the participation of 83 students, most of them (60,8%) from post-graduate students. Our results show that engagement provided by active learning methods can improve performance both in hard and soft skills. Students participation seems to be more relevant when activities require interaction of information, prediction and reasoning, such as open-ended questions and design of research projects. Therefore, our data shows that, in pandemic, active learning tools benefit students and improve their critical thinking and their motivation and positive positioning in science.

scientific communication and education↗

bioRxiv2019

Peptidylarginine Deiminase inhibition abolishesthe production of large extracellular vesicles fromGiardia intestinalis, affecting host-pathogeninteractions by hindering adhesion to host cells.

Giardia intestinalis is an anaerobic protozoan that is an important etiologic agent of inflammation-driven diarrhea worldwide. Although self-limiting, a deep understanding of the factors involved in the pathogenicity that produces the disruption of the intestinal barrier remains unknown. There is evidence that under diverse conditions, the parasite is capable of shedding extracellular vesicles (EVs) which could modulate the physiopathology of giardiasis. Here we describe new insights of G. intestinalis EV production, revealing its capacity to shed two different enriched EV populations (large and small extracellular vesicles) and identified a relevant adhesion function associated only with the larger population. Our work also aimed at assessing the influences of two recently identified inhibitors of EV release in mammalian cells, namely peptidylarginine deiminase (PAD) inhibitor and cannabidiol (CBD), on EV release from Giardia and their putative effects on host-pathogen interactions. PAD-inhibitor Cl-amidine and CBD were both able to effectively reduce EV shedding, the PAD-inhibitor specifically affecting the release of large extracellular vesicles and interfering with in vitro host-pathogen interactions. The strong efficacy of the PAD-inhibitor on Giardia EV release indicates a phylogenetically conserved pathway of PAD-mediated EV release, most likely affecting the Giardia arginine deiminase (GiADI) homolog of mammalian PADs. While there is still much to learn about G. intestinalis interaction with its host, our results suggest that large and small EVs may be differently involved in protozoa communication, and that EV-inhibitor treatment may be a novel strategy for recurrent giardiasis treatment.

microbiology↗