Biology subjects

Arango, B. G.

Publications and source records attributed to Arango, B. G..

3 recordsLinked to original sources

bioRxiv2026

Molecular signatures and cellular responses underlying hypoxic adaptation in sea turtles

Hypoxia-inducible factors (HIFs) are transcriptional regulators that orchestrate the canonical response to low-oxygen tension in animal cells. Vertebrates possess three HIF- isoforms, which arose from two gene duplication events of the ancestral HIF-1 gene. Here, we examined whether the HIF gene family (HIF-1, HIF-2, HIF-3, and HIF-1N inhibitor) shows evidence of positive selection in hypoxia-tolerant reptiles (Testudines), compared evolutionary patterns within the family, and assessed the transcriptional response to hypoxia in primary cells derived from a hypoxia-tolerant (Caretta caretta) and a non-tolerant (Sceloporus occidentalis) reptile. We found that HIF-1, HIF-2, and HIF-1N are highly conserved across reptiles, whereas HIF-3 is under positive selection in Testudines. We also identified multiple novel regulatory motifs unique to Testudines. Transcriptional signatures of hypoxia exposure indicated stark differences between lizards and turtles. Whereas lizard cells exhibited a canonical response to hypoxia, characterized by enriched cell-survival pathways, sea turtle cells exhibit a robust, distinctive transcriptional response involving enriched pathways related to protein synthesis, quality maintenance, and mitochondrial integrity. Surprisingly, cis-regulatory element analysis did not show HIFs as key regulators of the transcriptional response in either species. Instead, TFDP1 in lizard cells and E2F1 in sea turtle cells emerged as potential key regulators. TFDP1 regulates the cell cycle, specifically DNA synthesis and cell cycle progression, while E2F regulates DNA-damage response, apoptosis, metabolism, and fatty acid biosynthesis. These results suggest that the reptilian response to hypoxia is shaped by transcriptional plasticity, while highlighting key regulatory mechanisms driving hypoxic adaptation in sea turtle cells. However, positive selection of HIF-3 and novel HIF motifs suggest a combined, but yet to be uncovered, contribution of regulatory and coding sequence evolutionary mechanisms shaping hypoxia tolerance in Testudines.

molecular biology↗

bioRxiv2024

Hypoxia exposure fine-tunes mitochondrial function in sea turtle cells

Sea turtles experience extreme fluctuations in oxygen availability derived from extended breath-hold diving, yet the cellular adjustments that underlie hypoxia tolerance in these animals remain poorly understood. Here, we used metabolite profiling, extracellular flux assays, and microscopic analyses of the mitochondrial reticulum to study how primary cells derived from sea turtles and lizards cope with extended hypoxia exposure. Cells from both species proliferate in primary culture, stain positive for fibroblast markers, are metabolically active, and stabilize HIF1- when exposed to chemical or environmental hypoxia. In contrast to lizard cells, sea turtle cells exhibit a faster and more robust response to 1 or 24-hour hypoxia exposure (0.1% O2), upregulating antioxidant pathways and optimizing oxygen use rather than relying on glycolytic metabolism. Similarly, the mitochondrial reticulum is maintained without apparent fragmentation during hypoxia exposure in sea turtle cells. Consistent with these observations, mitochondrial function readily recovers in sea turtle but not lizard cells upon reoxygenation. These findings show that sea turtle cells undergo intrinsic metabolic adjustments to cope with extreme oxygen fluctuations, aligning with the remarkable hypoxic tolerance exhibited by these animals, which can endure up to 7 hours of breath-holding underwater.

physiology↗

bioRxiv2021

Oxidative stress is a potential cost of synchronous nesting in olive ridley sea turtles

Olive ridley sea turtles, Lepidochelys olivacea, exhibit a polymorphic reproductive behaviour nesting in solitary or in mass aggregations termed "arribadas", where thousands of turtles nest at once. Arribadas may provide fitness benefits including mate finding during nearshore aggregations and predator satiation at the time of hatching, but the potential costs of arribada nesting remain understudied. To explore the potential trade-offs of the fitness benefits associated with arribada nesting, we collected blood from olive ridley turtles nesting in arribada and solitary. We measured reproductive and metabolic hormones (progesterone, estradiol, testosterone, thyroxine, and triiodothyronine), triglycerides (TG), non-esterified fatty acids (NEFA) and markers of oxidative damage (4-hydroxynonenal, malondialdehyde, protein carbonyls, and nitrotyrosine). Arribada nesters were bigger and had higher levels of progesterone than solitary nesters. Similarly, thyroid hormones were higher in individuals nesting in arribada than in solitary nesters, while TG and NEFA were positively correlated in arribada but not in solitary nesters. Nesting in arribada was associated with increased lipid peroxidation and protein carbonyls compared to solitary nesting. These results suggest that nesting in arribada is potentially more energetically expensive than nesting solitarily, and that oxidative stress may be a trade-off of the fitness benefits associated with arribada nesting.

physiology↗