Biology subjects

Talla, V.

Publications and source records attributed to Talla, V..

7 recordsLinked to original sources

bioRxiv2026

Comparative Evaluation of Adeno-Associated Virus and Lentivirus Mediated Gene Transfer in Adult Rat Optic Nerve

BackgroundThe optic nerve serves as a vital conduit for visual signaling, and its degeneration in optic neuropathy results in irreversible vision loss. It is also a widely used model for studying central nervous system (CNS) injury and repair. Although adeno-associated virus (AAV) and lentivirus are extensively applied in CNS research, their transduction efficiency and cell-type specificity within the optic nerve remain poorly characterized. This study aimed to identify the most effective viral vector, serotype, and promoter for direct gene delivery to the adult rat optic nerve. MethodsSprague-Dawley rats (7-10 weeks) received intra-optic nerve injections of lentiviral or AAV vectors encoding GFP under different promoters (CAG, CMV, or GFAP). Two to three weeks post-injection, optic nerves were collected for immunohistochemistry with markers of oligodendrocytes (Olig2), astrocytes (GFAP, Sox9), and microglia (IBA1). Transduction efficiency and cell-type specificity were assessed using confocal microscopy. ResultsAAV2, AAV5, and lentivirus showed minimal transduction, with only sparse GFP-positive cells observed near injection sites. In contrast, AAV-PHP.eB carrying the CAG promoter yielded robust and widespread GFP expression near the injection site. Quantitative analysis revealed that approximately 90% of transduced cells were Olig2-positive oligodendrocytes, indicating strong tropism for this glial population. ConclusionAAV-PHP.eB driven by the CAG promoter enables efficient gene delivery to the optic nerve, with a predominant tropism for oligodendrocytes. This targeted intra-optic nerve injection approach offers a reliable platform for manipulating oligodendrocytes and investigating mechanisms of CNS development, injury, and repair relevant to both optic neuropathies and other CNS diseases.

neuroscience↗

bioRxiv2026

Neuritin1 Cis-Regulatory Elements Enable Gene Expression Preferentially in Retinal Ganglion Cells

PurposeRetinal ganglion cells (RGCs) are essential for visual signal transmission, yet they are vulnerable to injury and degeneration. Gene modulation in RGCs using adeno-associated virus (AAV) offers a promising avenue for neuroprotection and regeneration, but promoters lack sufficient RGC specificity, limiting precision needed for preclinical studies. This study aims to identify novel promoter-enhancer combinations (PECs) to achieve gene expression preferentially in RGCs. MethodsWe evaluated existing transcriptomic data to identify Neuritin 1(Nrn1) as a gene with highly restricted RGC expression in the retina. Synthetic PECs derived from human and mouse Nrn1 loci were incorporated into AAV2 vectors driving expression of a nuclear-targeted reporter GreenLantern. AAVs were delivered via intravitreal injection into C57BL6/J mice, and transduction efficiency and RGC specificity were evaluated in both young and aged retinas and those subjected to intraorbital optic nerve crush (ONC), using immunohistochemistry and quantitative analysis of RBPMS+ cells. ResultsWe found that AAV2 with a human Nrn1 PEC drives gene expression in RGCs. Quantitative analysis revealed that over 83% of transduced cells were RBPMS-positive, indicating robust RGC selectivity and significantly outperforming ubiquitous promoters. Notably, the Nrn1 PEC retained strong and selective transgene expression in RGCs in aged mice and following ONC, demonstrating its resilience under aged and injury conditions. ConclusionThe Nrn1 PEC enables efficient and injury-resilient gene expression in RGCs, addressing a key limitation in cell-specific targeting. This AAV-incorporated PEC offers a robust platform for evaluating neuroprotective interventions and accelerates translational development of gene therapies for glaucoma and other optic neuropathies.

neuroscience↗

bioRxiv2026

AAV2-Retro-Mediated Gene Transfer Selectively Targets Outer Retinal Cells Following Intravitreal Injection

PurposeTo characterize the cellular tropism and temporal dynamics of adeno-associated virus 2 (AAV2)-retro-mediated gene delivery in the adult mouse retina following intravitreal injection. MethodsAdult C57BL/6J mice received single or sequential intravitreal injections of AAV2-retro carrying the mGreenLantern (mGL) reporter gene. Retinas were collected at 1-, 3-, and 14-days post-injection (dpi) and processed for immunofluorescence analysis. Transduced cell types were identified using cell-type markers, including cone arrestin, RBPMS, and AP-2. The number and distribution of mGL-positive cells were quantified on whole retinas or retinal cross-sections to assess transduction efficiency, specificity, and spatial coverage. ResultsReporter expression was detected in the outer retina at 1 dpi and increased markedly at 3 and 14 dpi. AAV2-retro demonstrated strong tropism for photoreceptors and retinal pigment epithelium (RPE), with robust labeling of both rods and cones. In contrast to the robust outer retinal expression, transduction in the inner nuclear layers was limited to a few retinal ganglion and amacrine cells, reflecting strong cell-type specificity. Reporter expression was distributed widely across the retina, exceeding the localized pattern typically observed following subretinal delivery with conventional AAV2 vectors. Sequential injections further increased reporter expression and spatial coverage compared with single injections. ConclusionsAAV2-retro enables efficient, outer retina-specific gene delivery following intravitreal administration. This approach overcomes the limitations of traditional intravitreal gene transfer and provides a minimally invasive alternative to subretinal injection. AAV2-retro- mediated transduction may facilitate preclinical studies of retinal degeneration and support the development of gene therapies aimed at preserving photoreceptors and RPE function.

neuroscience↗

bioRxiv2024

Gene expression responses to environmental cues shed light on components of the migratory syndrome in butterflies

Migration is a complex behavior involving the synchronisation of many physiological and behavioral processes. Environmental cues must thus be interpreted to make decisions regarding resource allocation between, for example, migration or reproduction. In butterflies, the lack of host plants to sustain a new generation may indicate the need to migrate. Here, we used the painted lady butterfly (Vanessa cardui) as a model to characterize gene expression variation in response to host plant availability. Assessment of the response to host plant availability in adult female butterflies revealed significant modifications in gene expression, particularly within hormonal pathways (ecdysone oxidase and juvenile hormone esterase). We therefore hypothesize that tuning the ecdysone pathway may play a crucial role in regulating the timing of migration and reproduction in adult female painted lady butterflies. In addition, our analysis revealed significant enrichment of genes associated with lipid, carbohydrate, and vitamin biosynthesis, as well as the immune response. As environmental acquisition occurs throughout the life cycle, we also tracked gene expression responses to two other environmental cues across major developmental stages. Differences in both larval crowding and host plant availability during development resulted in significant changes in the expression of genes involved in development, reproduction and metabolism, particularly at the instar V larval stage. In summary, our results offer novel insights into how environmental cues affect expression profiles in migratory insects and highlight candidate genes that may underpin the migratory syndrome in the painted lady butterfly.

evolutionary biology↗

bioRxiv2023

Intercontinental panmixia despite distinct migration distances in the trans-Saharan butterfly migrant Vanessa cardui

The painted lady butterfly Vanessa cardui is renowned for its virtually cosmopolitan distribution and the remarkable long-distance migrations that are part of its annual, multi-generational migratory cycle. Recently, V. cardui individuals were found north and south of the Sahara in the autumn, suggesting distinct migratory behaviours within the species. However, the evolutionary and ecological factors shaping these differences in migratory behaviour remain largely unexplored. Here, we performed whole-genome resequencing and analysed the hydrogen and strontium isotopes of 40 V. cardui individuals simultaneously collected in the autumn from regions both north and south of the Sahara. Our investigation revealed two main migratory groups: (i) short-distance migrants, journeying from temperate Europe to the circum-Mediterranean region and (ii) long-distance migrants, originating from Europe, crossing the Mediterranean Sea and Sahara, and reaching West Africa, covering up to over 4,000 km. Despite these stark differences in migration distance, a genome-wide analysis revealed that both short- and long-distance migrants belong to a single intercontinental panmictic population extending from northern Europe to sub-Saharan Africa. Contrary to common biogeographic patterns, the Sahara is not a catalyst for population structuring in this species. No significant genetic differentiation or signs of adaptation and selection were observed between the two migratory phenotypes (pairwise FST = 0.001 {+/-} 0.006). Nonetheless, two individuals, which were early arrivals to West Africa and covered longer migration distances, exhibited some genetic differentiation. The lack of genetic structure between short- and long-distance migrants suggests that migration distance in V. cardui is a plastic response to environmental conditions. Significance statementAlthough migratory insects dominate living biomass fluxes and impact agriculture, ecosystems, and human communities, little is known about the controls of their migratory behavior. Our study develops an interdisciplinary framework, applied to the migratory butterfly V.cardui, to explore the genetic basis of variation in insect migration behavior. We leverage new generation isotope geolocation techniques to uncover striking differences in butterfly behaviour, with some individuals migrating short distances within the circum-Mediterranean region and others migrating thousands of kilometers across the Mediterranean Sea and Sahara. This major difference does not coincide with genetic differentiation or population structure and is likely a plastic response to environmental cues. This study provides a ground-breaking framework to study migration in insects.

evolutionary biology↗

bioRxiv2022

Migratory behavior is positively associated with genetic diversity in butterflies

Migration is typically associated with risk and uncertainty at the population level, but little is known about its cost and benefit trade-offs at the species level. Migratory insects often exhibit strong demographic fluctuations due to local bottlenecks and outbreaks. Here, we use genomic data to investigate levels of heterozygosity and long-term population size dynamics in migratory insects, as an alternative to classical local and short-term approaches such as regional field monitoring. We analyze whole-genome sequences from 97 Lepidoptera species and show that migratory species have significantly higher levels of genome-wide heterozygosity, a proxy for effective population size, than non-migratory species. Also, we contribute whole-genome data for one of the most emblematic insect migratory species, the painted lady butterfly (Vanessa cardui), sampled across its worldwide distribution range. This species exhibits one of the highest levels of heterozygosity described in Lepidoptera (2.95% {+/-} 0.15). Coalescent modeling (PSMC) shows historical demographic stability in V. cardui, and high effective population size estimates of 2 to 20 million individuals 10,000 years ago. The study reveals that the high risks associated with migration and local environmental fluctuations do not seem to decrease overall genetic diversity and demographic stability in migratory Lepidoptera. We propose a "compensatory" demographic model for migratory r-strategist organisms in which local bottlenecks are counterbalanced by reproductive success elsewhere within their typically large distributional ranges. Our findings highlight that the delimitations of populations are substantially different for sedentary and migratory insects, and that, in the latter, local and even regional field monitoring results may not reflect whole population dynamics. Genomic diversity patterns may elucidate key aspects of an insects migratory nature and population dynamics at large spatiotemporal scales.

evolutionary biology↗

bioRxiv2021

Evaluating the role of coevolution in a horizontally transmitted mutualism

Mutualism depends on the alignment of host and symbiont fitness. Horizontal transmission can readily decouple fitness interests, yet horizontally transmitted mutualisms are common in nature. We hypothesized that pairwise coevolution and specialization in host-symbiont interactions underlies the maintenance of cooperation in a horizontally transmitted mutualism. Alternatively, we predicted selection by multiple host species may select for cooperative traits in a generalist symbiont through diffuse coevolution. We tested for signatures of pairwise coevolutionary change between the squash bug Anasa tristis and its horizontally acquired bacterial symbiont Caballeronia spp. by measuring local adaptation. We found no evidence for local adaptation between sympatric combinations of A. tristis squash bugs and Caballeronia spp. across their native geographic range. To test for diffuse coevolution, we performed reciprocal inoculations to test for specialization between three Anasa host species and Caballeronia spp. symbionts isolated from conspecific hosts. We observed no evidence of specialization across host species. Our results demonstrate generalist dynamics underlie the interaction between Anasa insect hosts and their Caballeronia spp. symbionts. Specifically, diffuse coevolution between multiple host species with a shared generalist symbiont may maintain cooperative traits despite horizontal transmission.

evolutionary biology↗