Biology subjects

Negrete, J.

Publications and source records attributed to Negrete, J..

4 recordsLinked to original sources

bioRxiv2025

New minimally invasive techniques for sample collection in Antarctic seals

Remote or minimally invasive sampling techniques are essential in wildlife research, particularly for Antarctic seals. These methods reduce handling time, minimize animal stress, and improve biosecurity by preventing pathogen transmission, especially relevant during the current outbreak of highly pathogenic avian influenza affecting Antarctic megafauna. Research on ice-dependent seals is logistically challenging and often requires chemical immobilization, which is costly, time-consuming, and poses risks to both animals and researchers. To overcome these limitations, we developed a simple, low-cost remote sampling device to collect nasal swabs from seals without physical contact. The device consists of a telescopic pole with a swab attached to its end. Researchers approached seals resting on ice floes or land using inflatable boats, without disembarking, thus minimizing field exposure. Over ten days, we collected ten nasal swabs from leopard seals (Hydrurga leptonyx, n=4), Weddell seals (Leptonychotes weddellii, n=4), and southern elephant seals (Mirounga leonina, n=2). All samples tested negative for avian influenza virus (INF-A) using RT-qPCR. This methodology is adaptable to various species and conditions, requires minimal equipment, and can be implemented by small teams. It provides a safe, efficient tool for disease surveillance in remote polar environments, advancing marine mammal research while minimizing disturbance to wildlife.

zoology↗

bioRxiv2021

Cell-autonomous generation of the wave pattern within the vertebrate segmentation clock

Rhythmic and sequential segmentation of the growing vertebrate body relies on the segmentation clock, a multi-cellular oscillating genetic network. The clock is visible as tissue-level kinematic waves of gene expression that travel through the pre-somitic mesoderm (PSM) and arrest at the position of each forming segment. Here we test how this hallmark wave pattern is driven by culturing single maturing PSM cells. We compare their cell-autonomous oscillatory and arrest dynamics to those we observe in the embryo at cellular resolution, finding similarity in the relative slowing of oscillations and arrest in concert with differentiation. This shows that cell-extrinsic signals are not required by the cells to instruct the developmental program underlying the wave pattern. We show that a cell-autonomous timing activity initiates during cell exit from the tailbud, then runs down in the anterior-ward cell flow in the PSM, thereby using elapsed time to provide positional information to the clock. Exogenous FGF lengthens the duration of the cell-intrinsic timer, indicating extrinsic factors in the embryo may regulate the segmentation clock via the timer. In sum, our work suggests that a noisy cell-autonomous, intrinsic timer drives the slowing and arrest of oscillations underlying the wave pattern, while extrinsic factors in the embryo tune this timers duration and precision. This is a new insight into the balance of cell-intrinsic and -extrinsic mechanisms driving tissue patterning in development.

developmental biology↗

bioRxiv2021

Mechanotaxis directs Pseudomonas aeruginosa twitching motility.

The opportunistic pathogen Pseudomonas aeruginosa explores surfaces using twitching motility powered by retractile extracellular filaments called type IV pili. Single cells twitch by successive pili extension, attachment and retraction. However, whether and how single cells control twitching migration remains unclear. We discovered that P. aeruginosa actively directs twitching in the direction of mechanical input from type IV pili, in a process we call mechanotaxis. The Chp chemotaxis-like system controls the balance of forward and reverse twitching migration of single cells in response to the mechanical signal. On surfaces, Chp senses type IV pili attachment at one pole thereby sensing a spatially-resolved signal. As a result, the Chp response regulators PilG and PilH control the polarization of the extension motor PilB. PilG stimulates polarization favoring forward migration, while PilH inhibits polarization inducing reversal. Subcellular segregation of PilG and PilH efficiently orchestrates their antagonistic functions, ultimately enabling rapid reversals upon perturbations. This distinct localization of response regulators establishes a signaling landscape known as local-excitation, global-inhibition in higher order organisms, identifying a conserved strategy to transduce spatially-resolved signals. Our discovery finally resolves the function of the Chp system and expands our view of the signals regulating motility.

microbiology↗

bioRxiv2020

Theory of genetic oscillations with external noisy regulation

We present a general theory of noisy genetic oscillators with externally regulated production rate. The observables that characterize the genetic oscillator are discussed, and it is shown how their statistics depend on the statistics of the external regulator. We show that these observables have generic features that are observed in two different experimental systems: the expression of the circadian clock genes in fibroblasts, and in the transient and oscillatory dynamics of the segmentation clock genes observed in cells disassociated from zebrafish embryos. Our work shows that genetic oscillations with diverse biological contexts can be understood in a common framework based on delayed negative feedback system, and slow regulator dynamics.

biophysics↗