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Poulin, S.

Publications and source records attributed to Poulin, S..

3 recordsLinked to original sources

Proviruses in CD4+ T cells reactive to autologous antigens contribute to nonsuppressible HIV-1 viremia

Antiretroviral therapy (ART) halts HIV-1 replication, reducing plasma virus levels to below the limit of detection, but it is not curative due to a reservoir of latently infected CD4+ T cells. In some people living with HIV-1 (PLWH), plasma HIV-1 RNA becomes persistently detectable despite optimal ART. This nonsuppressible viremia (NSV) is characterized by identical, non-evolving HIV-1 RNA variants expressed from infected CD4+ T cell clones. The mechanisms driving persistent virus production from a specific population of infected cells are poorly understood. We hypothesized that proviruses in cells responding to chronic immunologic stimuli, including self-associated antigens, may drive viral gene expression and NSV. Here, we demonstrate that stimulation of CD4+ T cells with autologous cell lysates induces virus production in an MHC-II-dependent manner. In 7 of 8 participants with NSV, we recovered viral RNA released ex vivo in response to autologous cell lysates that matched plasma virus. This process involves both defective and replication-competent proviruses residing in conventional T cells, and is also observed in PLWH with undetectable viremia. These findings suggest that recognition of self-associated antigens is an important cause of HIV-1 reservoir expression, which can contribute to persistent systemic inflammation and potential rebound upon ART interruption. One sentence summaryHIV-1 viremia not suppressed by effective ART can be caused by proviruses in CD4+ T cells reactive to autologous antigens.

immunology↗

Structural and genetic determinants of zebrafish functional brain networks

Network science has significantly advanced our understanding of brain networks across species, revealing universal connectivity principles. While human studies based on magnetic resonance imaging (MRI) have established several network principles at macroscopic scales, recent breakthroughs, including high-amplitude regional co-activation patterns and spatially contiguous functional gradients, remain unexplored at cellular resolution in animal models. Here, we employ whole-brain functional imaging at cellular resolution in larval zebrafish, combined with anatomical and spatial genetic expression profile databases, to investigate the structural and genetic basis of functional brain networks. We show that mesoscopic functional connectivity (FC) is a robust measure of brain activity that captures the individuality of larvae. Using a public dataset of thousands of single-neuron reconstructions, we reveal a strong coupling between FC and structural connectivity (SC). Numerous properties of the connectome that account for indirect pathways and diffusion mechanisms individually and collectively predict interregional correlations. The hierarchical modular structure of SC and FC significantly overlaps in space, and modules identified within the connectome constrain the shape of both spontaneous and stimulus-driven activity patterns. Using visual stimuli and tail monitoring, we identify a functional network gradient that maps onto the sensorimotor function of brain regions. Finally, we identify a set of genes whose co-expression in brain regions significantly predicts regional FC. Our findings reproduce several key features of mammalian brain networks in zebrafish, demonstrating the potential for studying large-scale network phenomena in smaller, optically accessible vertebrate brains.

neuroscience↗

Development of sensorimotor responses in larval zebrafish: a comparison between wild-type and GCaMP6s transgenic line

During early development, zebrafish larvae exhibit stereotypical behaviors, which rapidly become more complex. Thus, the generation of mutant transgenic lines that maintain transparency throughout their larval stage and that can be used to record brain activity has offered strategic opportunities to investigate the underlying neural correlates of behavior establishment. However, few studies have documented the behavioral profile of these lines during larval development. Here, we set up a behavioral characterization using diverse stimuli (light and vibration) throughout larval development to compare the responses of a transgenic strain expressing a pan-neuronal calcium indicator (GCaMP6s) with that of a wild-type strain. Interestingly, we report a drastic switch in behavioral responses to light transitions at 11 days post-fertilization (dpf) and to vibration stimuli at 14 dpf in both lines. These data highlight a specific time window of behavioral complexification. Meanwhile, we found no major difference in the maturation of sensorimotor responses between GCaMP6s and wild-type strains. Thus, these results support using GCaMP6s strain in investigating the neural mechanisms underlying the developmental maturation of sensorimotor responses. We observed nevertheless some minor differences that suggest careful attention should be taken when using mutant/transgenic lines for behavioral studies. Highlights- Longitudinal investigation of sensorimotor responses by zebrafish during their larval development - During the second week of development, larval zebrafish switch their motor response to light transition - Pan-neuronal nuclear expression of GCaMP6s has little impact on larval fish response to various stimuli

neuroscience↗