Biology subjects

Mahe, K.

Publications and source records attributed to Mahe, K..

4 recordsLinked to original sources

bioRxiv2025

Impact of port conditions and acclimation capacity of common two-banded seabream juveniles in the bay of Toulon: implications for nursery rehabilitation efforts

Ports are heavily anthropized coastal environments characterized by intense pollution and habitat alterations, creating challenging living conditions for marine organisms, particularly juvenile fish that rely on these areas as nurseries. While recent rehabilitation efforts of the nursery function in ports have focused on structural modifications, the impacts of port chemical and physical pollution are currently disregarded. Using field sampling and caging experiments, we examined the physiological (growth, lipid content, CYP1A-dependent biotransformation activity) and molecular (RNA-seq) responses of juvenile two-banded sea bream (Diplodus vulgaris) by comparing one port site with two adjacent sites from outside of the port, assessing their potential for short-term acclimation to port conditions. Results from individuals sampled in the field revealed distinct physiological and transcriptomic profiles in port juveniles, indicating specific responses to this environment. Notably, alterations related to lipid accumulation, detoxification, hypoxia, and circadian regulation were observed. After one month of caging all the individuals from different locations in the port, juveniles originating from outside the port exhibited stronger transcriptional responses compared to individuals that grew within the port, with higher expression of genes involved in detoxification and lipid metabolism, and a strong overexpression of oncogenes, while individuals originating from the port upregulated genes involved in energy metabolism, suggesting some capacity for short-term acclimation in port-resident juvenile fish. These findings highlight the potential impact of port conditions on juvenile fish health, with implications for the effectiveness of rehabilitation efforts. This study emphasizes the need for further research to inform nursery rehabilitation strategies in polluted ports.

physiology↗

bioRxiv2021

Release of endogenous dynorphin opioids in the prefrontal cortex disrupts cognition

Following repeated opioid use, some dependent individuals experience persistent cognitive deficits that contribute to relapse of drug-taking behaviors, and one component of this response may be mediated by the endogenous dynorphin/kappa opioid system in neocortex. In mice, we find that acute morphine withdrawal evokes dynorphin release in the medial prefrontal cortex (PFC) and disrupts cognitive function by activation of local kappa opioid receptors (KORs). Immunohistochemical analyses using a phospho-KOR antibody confirmed that both withdrawal-induced and optically evoked dynorphin release activated KOR in PFC. Using a genetically encoded sensor based on inert KOR (kLight1.2a), we revealed the in vivo dynamics of endogenous dynorphin release in the PFC. Local activation of KOR in PFC produced multi-phasic disruptions of memory processing in an operant delayed alternation behavioral task, which manifest as reductions in response number and accuracy during early and late phases of an operant session. Local pretreatment in PFC with the selective KOR antagonist norbinaltorphimine (norBNI) blocked the disruptive effect of systemic KOR activation during both early and late phases of the session. The early, but not late phase disruption was blocked by viral excision of PFC KORs, suggesting an anatomically dissociable contribution of pre- and postsynaptic KORs. Naloxone-precipitated withdrawal in morphine-dependent mice or optical stimulation of pdynCre neurons using Channelrhodopsin-2 (ChR2) disrupted delayed alternation performance, and the dynorphin-induced effect was blocked by local norBNI. Our findings describe a mechanism for control of cortical function during opioid dependence and suggest that KOR antagonism could promote abstinence.

neuroscience↗

bioRxiv2020

Condensation of pericentrin proteins in human cells illuminates phase separation in centrosome assembly

AbstractAt the onset of mitosis, centrosomes expand the pericentriolar material (PCM) to maximize their microtubule-organizing activity. This step, termed centrosome maturation, ensures proper spindle organization and faithful chromosome segregation. However, as the centrosome expands, how PCM proteins are recruited and held together without membrane enclosure remains elusive. We found that endogenously expressed pericentrin (PCNT), a conserved PCM scaffold protein, condenses into dynamic granules during late G2/early mitosis before incorporating into mitotic centrosomes. Furthermore, the N-terminal portion of PCNT--enriched with conserved coiled-coils (CCs) and low-complexity regions (LCRs)--phase separates into dynamic condensates that selectively recruit PCM proteins and nucleate microtubules in cells. We propose that CCs and LCRs, two prevalent sequence features in the centrosomal proteome, are preserved under evolutionary pressure in part to mediate liquid-liquid phase separation, a process that bestows upon the centrosome distinct properties critical for its assembly and functions.

cell biology↗

bioRxiv2017

Co-translational protein targeting facilitates centrosomal recruitment of PCNT during centrosome maturation

As microtubule-organizing centers of animal cells, centrosomes guide the formation of the bipolar spindle that segregates chromosomes during mitosis. At mitosis onset, centrosomes maximize microtubule-organizing activity by rapidly expanding the pericentriolar material (PCM). This process is in part driven by the large PCM protein pericentrin (PCNT), as its level increases at the PCM and helps recruit additional PCM components. However, the mechanism underlying the timely centrosomal enrichment of PCNT remains unclear. Here we show that PCNT is delivered co-translationally to centrosomes during early mitosis by cytoplasmic dynein, as evidenced by centrosomal enrichment of PCNT mRNA, its translation near the centrosome, and requirement of intact polysomes for PCNT mRNA localization. Additionally, the microtubule minus-end regulator, ASPM, is also targeted co-translationally to mitotic spindle poles. Together, these findings suggest that co-translational targeting of cytoplasmic proteins to specific subcellular destinations may be a generalized protein targeting mechanism.

cell biology↗