Biology subjects

Andrade, A.

Publications and source records attributed to Andrade, A..

13 recordsLinked to original sources

bioRxiv2026

Microbial communities in Ornithodoros phacochoerus ticks: spatial structure and influence of African swine fever virus infectious status

AO_SCPLOWBSTRACTC_SCPLOWOrnithodoros phacochoerus are nidicolous soft ticks of the Ornithodoros moubata complex of species known to be vectors of the African swine fever (ASF) virus. These Ornithodoros ticks depend on endosymbionts to produce essential nutrients necessary for their development. However, endosymbionts are only a part of the complex microbiota hosted by the tick. This microbiota often includes primary or secondary endosymbionts, commensal species from the environment, and, most of the time, some pathogens. The present study was performed to understand the organization and spatial distribution of the microbiota of O. phacochoerus. One of the objectives was to investigate if the pathogen of interest (ASF virus) is involved in the organization of the microbiota through pathogen-induced dysbiosis or other interactions. For this purpose, 704 O. phacochoerus ticks were collected from two conservation areas in Mozambique. Sequencing was performed targeting the V3-V4 region of the 16S rRNA gene, and the resulting dataset was processed using FROGS to characterize the bacterial microbiota hosted by the ticks. The results indicate that the microbiota of Ornithodoros phacochoerus contains very low bacterial diversity, with one primary endosymbiont (Francisella-like endosymbiont), one potential secondary endosymbiont (Rickettsiella), and very few environmental or pathogenic bacterial species. We found a clear spatial structure of the microbiota, with ticks from the same sampling site showing similar patterns. On the contrary, no association with the infectious status for African swine fever virus was detected, suggesting that this pathogen does not shape Ornithodoros microbial communities. Our results on tick - microbiota - pathogen - environment interactions in nidicolous soft ticks, showed patterns that differ from most hard tick studies.

microbiology↗

bioRxiv2026

Cacna1b alternative splicing is linked to associative learning

Voltage-gated CaV2.2 channels are essential for neurotransmitter release throughout the nervous system including areas related to learning and memory like the hippocampus. Previous results have shown that CaV2.2 channels are involved in cognitive processes. However, a link between alternative splicing of the Cacna1b (gene that encodes for CaV2.2) pre-mRNA and cognitive processes has not been described. The Cacna1b pre-mRNA undergoes extensive cell-specific alternative splicing. In this body of work, we focus on the cassette exon 18a. Alternative splicing of exon 18a generates two splice variants, +18a-Cacna1b and {Delta}18a-Cacna1b. Exon 18a encodes a 21-amino acid sequence within the SYNaptic PRotein INTeraction (synprint) site. Splice variants containing exon 18a (+18a-CaV2.2) show reduced cumulative inactivation and increased Ca{superscript 2} current density compared to splice variants lacking exon 18a ({Delta}18a-CaV2.2), suggesting functional specialization. We previously showed that +18a-Cacna1b splice variants are enriched in cholecystokinin-expressing interneurons (CCK+INs). This neuronal type is strongly implicated in associative learning. Therefore, we tested whether alternative splicing of exon 18a contributes to associative learning. To test this hypothesis, we used genetically engineered mice that constitutively express either +18a-Cacna1b (+18a) or {Delta}18a-Cacna1b ({Delta}18a). We first validated that restricted splicing of exon 18a did not alter downstream alternative or constitutive spliced exons in the Cacna1b pre-mRNA, nor total CaV2.2 protein levels. We then performed a comprehensive behavioral analysis that included assessment of associate learning. We found that in the trace fear conditioning task, +18a mice exhibited less freezing during the trace interval in both the acquisition and memory phases compared to WT mice. Whereas {Delta}18a mice showed enhanced freezing during the same intervals relative to WT mice. These bidirectional phenotypes reveal that exon 18a shapes aversive associative learning. Furthermore, exon 18a splicing did not influence spatial working memory, spatial navigation under stress, nociceptive responses in basal and inflammatory conditions, overall locomotion or exploratory behavior. These results suggest that the behavioral impact of exon 18a splicing is highly selective. Together, our findings identify alternative splicing of exon 18a as a molecular contributor to associative learning.

neuroscience↗

bioRxiv2025

Charting the Undiscovered Metabolome with Synthetic Multiplexing

Most molecular features detected in untargeted metabolomics remain uncharacterized due to the limited scope of existing spectral reference libraries. We synthesized >100,000 biologically inspired compounds using multiplexed reactions, of which 91% were absent from existing structural databases, and searched the resulting MS/MS library across >1.7 billion public spectra, increasing annotation rates by 17.4%. This approach revealed previously undescribed exposure-derived metabolites, including ibuprofen-carnitine. Because ibuprofen has been linked to rhabdomyolysis, reduced mitochondrial function, and impaired muscle recovery in carnitine-limited contexts, we investigated the functional relevance of this conjugate. Ibuprofen-carnitine reduced carnitine transport via the OCTN2 transporter, and in a postpartum mouse muscle injury model, ibuprofen delayed muscle repair that could be rescued by carnitine supplementation, with urinary ibuprofen-carnitine:carnitine ratios tracking this effect. These findings support a hypothesis whereby NSAID-carnitine conjugates compete for carnitine transport, impairing energy metabolism and muscle recovery in susceptible individuals. Synthetic multiplexing thus provides a scalable route to annotate the dark metabolome and generate experimentally testable biological hypotheses.

biochemistry↗

bioRxiv2025

The migration of an expanding sea turtle population alters the structure of marine megafauna communities

Interactions shape community structures, yet the impact of large migratory influxes on communities, particularly marine ones, remains elusive. Using drone surveys, we investigated changes of marine megafauna communities (e.g., sharks, rays), during the mass migration of loggerhead sea turtles (Caretta caretta) in Cabo Verde, one of the largest, and growing, rookeries globally and a biodiversity hotspot. In high nesting density areas, with over 6,000 turtles detected in-water at the seasons peak, the community structured with sharks distributing between the turtles and the coastline. In low-density areas ([~]500 turtles), no structuring was detected. After the seasons peak, increased shark abundance and shoreward movement suggest they anticipate a nutrient pulse from emerging hatchlings. Our results highlight the role of sea turtle abundance in structuring marine communities, both as a high-quality food resource (hatchlings) and a likely non-consumable species (adults). Overall, we show the significant impact of migratory species on marine megafauna communities.

ecology↗

bioRxiv2025

Trpv1-dependent Cacna1b gene inactivation reveals cell-specific functions of CaV2.2 channels in vivo

Voltage-gated CaV2.2 channels underlie the N-type current, and they regulate calcium entry at many presynaptic nerve endings to control transmitter release. A role for CaV2.2 channels has been well-established in the transmission of pain information using pharmacological and global gene inactivated mouse models. However, investigation of the cell-specific actions of CaV2.2 channels would benefit from the availability of cell-restricted knockout mouse models and particularly in dissecting behavioral responses that depend on CaV2.2 channel activity. Here, we show the importance of CaV2.2 channels in Trpv1-lineage neurons in behavioral responses to sensory stimuli using Cre-dependent inactivation of the Cacna1b gene. Our work shows the cell- type specificity of CaV2.2 channels in mediating rapidly developing heat hypersensitivity and the utility of Cre-dependent inactivation of Cacna1b to discern cell-specific CaV2.2 channel functions.

neuroscience↗

bioRxiv2023

ω-Phonetoxins inhibit voltage-gated calcium CaV2.2 ion channel splice isoforms of dorsal root ganglia

Cell-specific alternative splicing of Cacna1b pre-mRNA generates functionally distinct voltage-gated CaV2.2 channels. CaV2.2 channels mediate the release of glutamate from nociceptor termini in the dorsal horn spinal cord and they are implicated in chronic pain. One alternatively spliced exon in Cacna1b, e37a, is highly expressed in dorsal root ganglia, relative to other regions of the nervous system, and it is particularly important in inflammatory hyperalgesia. Here we studied the effects of two {omega}-phonetoxins, PnTx3-4 and Ph1{beta}, derived from the spider Phoneutria nigriventer on CaV2.2 channel isoforms of dorsal root ganglia (CaV2.2 e37a and CaV2.2 e37b). Both PnTx3-4 and Ph1{beta} are known to have analgesic effects in rodent models of pain and to inhibit CaV2.2 channels. CaV2.2 e37a and CaV2.2 e37b isoforms expressed in a mammalian cell line were inhibited by PnTx3-4 and Ph1{beta} with similar potency and with similar timecourse, although CaV2.2 e37a currents were slightly, but consistently more sensitive to toxin inhibition compared to CaV2.2 e37b. The inhibitory effects of PnTx3-4 and Ph1{beta} on CaV2.2-e37a and CaV2.2-e37b channels were voltage-dependent, and both occlude the inhibitory effects of {omega}-conotoxin GVIA, consistent with a common site of action. The potency of PnTx3-4 and Ph1{beta} on both major splice isoforms in dorsal root ganglia constribute to understanding the analgesic actions of these {omega}-phonetoxins.

neuroscience↗

bioRxiv2020

SMARCA4 deficient tumours are vulnerable to KDM6A/UTX and KDM6B/JMJD3 blockade

Despite the genetic inactivation of SMARCA4, a core component of the SWI/SNF-complex commonly found in cancer, there are no therapies that effectively target SMARCA4-deficient tumours. Here, we show that, unlike the cells with activated MYC oncogene, cells with SMARCA4 inactivation are refractory to the histone deacetylase inhibitor, SAHA, leading to the aberrant accumulation of H3K27me3. This is associated with impaired transactivation and significantly reduced levels of the histone demethylases KDM6A/UTX and KDM6B/JMJD3, which confer a strong dependency on the KDM6s in the SMARCA4-mutant cells, so that its inhibition compromises cell viability. Administering the KDM6 inhibitor GSK-J4 to mice orthotopically implanted with SMARCA4-mutant lung cancer cells or primary small cell carcinoma of the hypercalcaemic type (SCCOHT) had strong anti-tumour effects. Our results highlight the vulnerability of KDM6 inhibitors as a characteristic that could be exploited for treating SMARCA4-mutant cancer patients.

cancer biology↗

bioRxiv2020

N-type calcium channels control GABAergic transmission in brain areas related to fear and anxiety

Presynaptic N-type (Cav2.2) calcium channels are key for action potential evoked transmitter release in the peripheral and central nervous system. Previous studies have highlighted the functional relevance of N-type calcium channels at both the peripheral and central level. In the periphery, the N-type calcium channels regulate nociceptive and sympathetic responses. At the central level, N-type calcium channels have been linked to aggression, hyperlocomotion, and anxiety. Among the areas of the brain that are involved in anxiety are the basolateral amygdala, medial prefrontal cortex, and ventral hippocampus. These three areas share similar characteristics in their neuronal circuitry. Pyramidal projection neurons are under the inhibitory control of a wide array of interneurons including those that express the peptide cholecystokinin. This type of interneuron is well-known to rely on N-type calcium channels to release GABA in the hippocampus, however whether these channels control GABA release from cholecystokinin-expressing interneurons in the basolateral amygdala and medial prefrontal cortex is not known. Here using sophisticated mouse models to genetically label cholecystokinin-expressing interneurons, we found that N-type calcium channels control ~50% of GABA release in basolateral amygdala. By contrast, N-type calcium channels are functionally absent in synapses of cholecystokinin-expressing interneurons of medial prefrontal cortex. Our findings provide insights into the precise localization of N-type calcium channels in synapses of brain areas related to anxiety.

neuroscience↗

bioRxiv2020

The boundaries of State-Space Granger Causality Analysis applied to BOLD simulated data: a comparative modelling and simulation approach

BackgroundThe analysis of connectivity has become a fundamental tool in human neuroscience. Granger Causality Mapping is a data-driven method that uses Granger Causality (GC) to assess the existence and direction of influence between signals, based on temporal precedence of information. More recently, a theory of Granger causality has been developed for state-space (SS-GC) processes, but little is known about its statistical validation and application on functional magnetic resonance imaging (fMRI) data. New MethodWe implemented a new heuristic, focusing on the application of SS-GC with a distinct statistical validation technique - Time Reversed Testing - to generative synthetic models and compare it to classical multivariate computational frameworks. We also test a range of experimental parameters, including block structure, sampling frequency, noise and system mean pairwise correlation, using a statistical framework of binary classification. ResultsWe found that SS-GC with time reversed testing outperforms other frameworks. The results validate the application of SS-GC to generative models. When estimating reliable causal relations, SS-GC returns promising results, especially when considering synthetic data with an high impact of noise and sampling rate. ConclusionsSS-GC with time reversed testing offers a possible framework for future analysis of fMRI data in the context of data-driven causality analysis. HighlightsO_LIState-Space GC was combined with a statistical validation step, using a Time Reversed Testing. C_LIO_LIThis novel heuristic overpowers classical GC, when applied to generative models. C_LIO_LICorrectly identified connections between variables increase with the increase of number of blocks and number of points per block. C_LIO_LISNR and subsampling have a significant impact on the results. C_LI

neuroscience↗

bioRxiv2019

Developmental and cell-specific expression of Cacna1d splice variants

CaV1.3 is an L-type voltage-gated calcium channel implicated in several functions including gene expression, pacemaking activity, and neurotransmitter release. The gene that encodes the CaV1-pore forming subunit of CaV1.3 (Cacna1d) is a multi-exon gene that undergoes extensive alternative splicing, which provides functional versatility to this gene across tissues and cell-types. The function and expression of several Cacna1d splice variants within the C-terminus have been previously characterized. These splice variants differ in their voltage-dependence of activation, Ca2+-dependent inactivation, and their sensitivity to dihydropyridines. However, less is known about alternatively spliced exons in Cacna1d located downstream of domain I and upstream of the C-terminus (e11, e22a/e22, e31a/e31b/e32). Here, we performed a systematic study to determine the developmental and cell-specific expression of several Cacna1d splice variants. We found that the cassette e11 is upregulated during brain development, and in adult cortical tissue is more abundant in excitatory neurons relative to inhibitory interneurons. This exon is also upregulated upon nerve growth factor (NGF) induced differentiation of pheochromocytoma cells, PC12. At the functional level, the splice variants resulting from e11 alternative splicing (+e11-Cacna1d and {Delta}e11-Cacna1d) form functional CaV1.3 channels with similar biophysical properties in expression mammalian systems. Of the pair of mutually exclusive exons, e22a and e22, the later dominates at all stages. However, we observed a slight upregulation of e22 from embryonic to adult human brain. A second pair of mutually exclusive exons, e31a and e31b, was also studied. We found that e31a increases during brain development. Finally, the cassette exon 32 is repressed in adult brain tissue.

neuroscience↗

bioRxiv2019

Tissue and cell-type specific expression of a splice variant in the II-III cytoplasmic loop of Cacna1b

Presynaptic CaV2.2 (N-type) channels are fundamental for transmitter release across the nervous system. The gene encoding CaV2.2 channels, Cacna1b, contains alternatively spliced exons that originate functionally distinct splice variants (e18a, e24a, e31a and 37a/37b). Alternative splicing of the cassette exon 18a generates two mRNA transcripts (+e18a-Cacna1b and {Delta}e18a-Cacna1b). In this study, using novel mouse genetic models and in situ hybridization (BaseScope), we confirmed that +e18a-Cacna1b splice variants are expressed in monoaminergic regions of midbrain. We expanded these studies and identified +e18a-Cacna1b mRNA in deep cerebellar cells and spinal cord motor neurons. Furthermore, we determined that +e18a-Cacna1b is enriched in cholecystokinin expressing interneurons. Our results provide key information to understand cell-specific functions of CaV2.2 channels.

neuroscience↗

bioRxiv2018

A schizophrenia risk gene, NRGN, bidirectionally modulates synaptic plasticity via regulating the neuronal phosphoproteome

NRGN is a schizophrenia risk gene identified in recent genetic studies, encoding a small neuronal protein, neurogranin (Ng). Individuals carrying a risk variant of NRGN showed decreased hippocampal activation during contextual fear conditioning. Furthermore, the expression of Ng was reduced in the post-mortem brains of schizophrenic patients. Using the mouse model, we found that the translation of Ng in hippocampus is rapidly increased in response to novel context exposure, and this up-regulation is required for encoding contextual memory. The extent and degree of the effect that altered Ng expression has on neuronal cellular functions are largely unknown. Here, we found that Ng bidirectionally regulates synaptic plasticity in the hippocampus. Elevated Ng levels facilitated long-term potentiation (LTP), whereas decreased Ng levels impaired LTP. Quantitative phosphoproteomic analysis revealed that decreasing Ng caused a significant shift in the phosphorylation status of postsynaptic density proteins, highlighting clusters of schizophrenia- and autism-related genes. In particular, decreasing Ng led to the hypo-phosphorylation of NMDAR subunit Grin2A at newly identified sites, resulting in accelerated decay of NMDAR-mediated channel currents. blocking protein phosphatase PP2B activity rescued the accelerated synaptic NMDAR current decay and the impairment of LTP caused by decreased Ng levels, suggesting that enhanced synaptic PP2B activity led to the deficits. Taken together, our work suggests that altered Ng levels under pathological conditions affect the phosphorylation status of neuronal proteins by tuning PP2B activity and thus the induction of synaptic plasticity, revealing a novel mechanistic link of a schizophrenia risk gene to cognitive deficits.

neuroscience↗

bioRxiv2018

MRI-related anxiety in healthy individuals, intrinsic BOLD oscillations at 0.1 Hz and heart rate variability in low frequency bands

Participation in a MRI scan is associated with increased anxiety, thus possibly impacting baseline recording for functional MRI studies. We investigated in 23 healthy individuals without any former MRI experience (scanner-naive) the relations between anxiety, 0.1-Hz BOLD oscillations and heart rate variability (HRV) in two separate resting state sessions (R1, R2). BOLD signals were recorded from precentral gyrus (PCG) and insula in both hemispheres. Phase-locking and time delays were computed in the frequency band 0.07-0.13 Hz. Positive (pTD) and negative time delays (nTD) were found. The pTD characterize descending neural BOLD oscillations spreading from PCG to insula and nTD characterize ascending vascular BOLD oscillations related to blood flow in the middle cerebral artery. HRV power in two low frequency bands 0.06-0.1 Hz and 0.1-0.14 Hz was computed. Based on the drop rate of the anxiety level from R1 to R2, two groups could be identified: one with a strong anxiety decline (large drop group) and one with a moderate decline or even anxiety increase (small drop group). A significant correlation was found only between the left-hemispheric time delay (pTD, nTD) of BOLD oscillations and anxiety drop, with a dominance of nTD in the large drop group. The analysis of within-scanner HRV revealed a pronounced increase of low frequency power between both resting states, dominant in the band 0.06-0.1 Hz in the large drop group and in the band 0.1-0.14 Hz in the small drop group. These results suggest different mechanisms related to anxiety processing in healthy individuals. One mechanism (large drop group) could embrace an increase of blood circulation in the territory of the left middle cerebral artery (vascular BOLD) and another (small drop group) translates to rhythmic central commands (neural BOLD) in the frequency band 0.1-0.14 Hz.

neuroscience↗