Biology subjects

Gonzalez-Garcia, E.

Publications and source records attributed to Gonzalez-Garcia, E..

4 recordsLinked to original sources

bioRxiv2026

Engineered microRNA feedback circuits enable tunable and autonomous control of synthetic receptor activity

Synthetic receptors are powerful tools for cellular engineering, yet their utility is often constrained by constitutive activity and the absence of natural feedback mechanisms that maintain cellular homeostasis. To address this, we engineered an autonomous regulatory circuit for synthetic Notch (synNotch) receptor activation using an orthogonal microRNA (miRNA)-mediated negative feedback mechanism in mammalian cells. Specifically, synNotch activation induces the expression of a synthetic miRNA that targets complementary sites engineered into the synNotch transcript, resulting in a self-limiting feedback loop. We demonstrate that synNotch repression positively correlates with the number of miRNA target sites integrated into the receptor transcript, enabling tunable control of receptor expression. Furthermore, flow cytometry and live-cell imaging analyses revealed effective suppression of synNotch expression following activation. Downstream target gene expression peaked at approximately 48 hours post-activation before gradually declining as the feedback circuit engaged. This approach achieves autonomous synthetic receptor regulation--eliminating the need for external intervention--and enables tunable response dynamics through rational circuit design. Our miRNA feedback strategy provides a generalizable platform for engineering self-regulating synthetic receptor systems with improved control and predictability for cellular engineering applications.

synthetic biology↗

bioRxiv2021

Genome-wide analyses reveal a strong association between LEPR gene variants and body fat reserves in ewes

Among the adaptive capacities of animals, the management of energetic body reserves (BR) through the BR mobilization and accretion processes (BR dynamics, BRD) has become an increasingly valuable attribute for livestock sustainability, allowing animals to cope with more variable environments. BRD has previously been reported to be heritable in ruminants. In the present study, we conducted genome-wide studies (GWAS) in sheep to determine genetic variants associated with BRD. BR levels and BR changes over time were obtained through body condition score measurements at eight physiological stages throughout each productive cycle in Romane ewes (n=1034) and were used as phenotypes for GWAS. After quality controls and imputation, 48,513 single nucleotide polymorphisms (SNP) were included in the GWAS. Among the QTLs identified, a major QTL associated with BR levels during pregnancy and lactation was identified on chromosome 1. In this region, several significant SNPs mapped to the leptin receptor gene (LEPR), among which one SNP mapped to the coding sequence. The point mutation induces the p.P1019S substitution in the cytoplasmic domain, close to tyrosine phosphorylation sites. The frequency of the SNP associated with increased BR levels was 32%, and the LEPR genotype explained up to 5% of the variance of the trait. These results provide strong evidence for involvement of LEPR in the regulation of BRD in sheep and highlight it as a major candidate for improving adaptive capacities.

genetics↗

bioRxiv2020

PhenoBR: a model to phenotype body condition dynamics in meat sheep

In situations of negative energy balance (NEB) due to feed scarcity or high physiological demands, body energy reserves (BR), mainly stored in adipose tissues, become the main sources of energy for ruminants. The capacity to mobilize and restore such BRs in response to different challenges is of major concern in the current context of breeding for resilience. Body condition score (BCS) is a common, practical indicator of BR variations throughout successive productive cycles, and quantitative tools for characterizing such dynamics at the individual level are still lacking. The main objective of this work was to characterize body condition dynamics in terms of BR mobilization and accretion capacities of meat sheep during their productive lifespan through a modelling approach. The animal model used in this work was the reproductive meat ewe (n = 1478) reared in extensive rangeland. Regular measurements of BCS for each productive cycle were used as the indicator of BR variations. A hybrid mathematical model and a web interface, called PhenoBR, was developed to characterize ewes BCS variations through four synthetic and biologically meaningful parameters for each productive cycle i: BR accretion rate [Formula], BR mobilization rate [Formula], plus the time of onset and the duration of the BR mobilization, [Formula] and {Delta}Ti, respectively. The model converged for all the ewes included in the analysis. Estimation of the parameters indicated the inter-individual variability for BR accretion and mobilization rates, and for the length of the mobilization period. Body reserve mobilization rates were closely correlated between productive cycles. Significant correlations between BR mobilization and accretion rates suggest that the two processes are biologically linked. Parameters kp and kb decreased as parity increased. BR mobilization rate and duration increased as litter size increased, while BR accretion rate decreased. Individual characterization of animals by these parameters makes it possible to rank them for their efficiency in the use of body reserves when facing NEB challenges. Such parameters could contribute to better management and decision-making by farmers and advisors, e.g. by adapting feeding systems to the individual characteristics of BR dynamics, or by geneticists as criteria to develop future animal breeding programs including BR dynamics for more robust and resilient animals.

physiology↗

bioRxiv2019

Residual feed intake in dairy ewes: an evidence of intraflock variability

This study examined the intraflock variability of feed efficiency in dairy ewes, through monitoring residual feed intakes (RFI). Primiparous lactating ewes (n=43; 57.7{+/-}0.91 kg body weight [BW] at lambing), representative of a French Lacaune dairy flock, were allocated in an equilibrated 2 x 2 factorial design experiment, lasting for 63 days during mid-lactation and combining 2 litter sizes (singletons, SING or twins, TWIN) and 2 daily milking frequencies (once, ONE or twice, TWO). Ewes were individually fed a diet based on ryegrass silage, local hay and supplements. Individual DMI was recorded daily and further used to evaluate (and compare) differences in RFI between ewes at 35, 42, 49, 56, 63, 70, 77, 84, 91 and 98 days relative to lambing (DIM). Total (BW) and metabolic (BW0.75) body weight, BCS, milk yield and plasma NEFA were monitored weekly. Differences in DMI were mainly due to the lactation stage and litter size and were 11% higher in ewes with TWIN compared to SING. This was positively correlated to milk yield and consistent with differences in RFI which varied due to litter size and to the milking frequency x lactation stage interaction. Ewes that lambed SING showed higher feed efficiency ({square}0.13{+/-}0.020 vs. 0.08{+/-}0.015 kg DM/ewe/d of RFI in SING vs. TWIN, respectively), whereas there was no differences in BW or BCS. Milking frequency did not affect DMI but milk yields were higher in TWO, which was related to a higher feed efficiency in this group (0.04{+/-}0.017 vs. {square}0.10{+/-}0.018 kg DM/ewe/d of RFI in ONE vs. TWO, respectively). Average RFI was affected (P <0.0001) by the ewe, thus allowing a ranking among individuals to be established. High (n=22) or low (n=21) feed efficiency ewes averaged {square}0.17{+/-}0.09 or 0.18{+/-}0.09 kg DM/d RFI, respectively. Estimates of RFI were not correlated to the individual milk production potential. Even if no differences in BW, BW0.75 or BCS were detected, high efficiency ewes mobilised almost two-fold their body reserves when compared to the low efficiency group. The observed intraflock variability in feed efficiency of this dairy ewes flock was affected by litter size and milking frequency but also by evident differences between individuals physiologies.

physiology↗