Biology subjects

Perez, R.

Publications and source records attributed to Perez, R..

27 records · Page 2Linked to original sources

bioRxiv2021

SARS-CoV-2 RBD-Tetanus toxoid conjugate vaccine induces a strong neutralizing immunity in preclinical studies

Controlling the global COVID-19 pandemic depends, among other measures, on developing preventive vaccines at an unprecedented pace. Vaccines approved for use and those in development intend to use neutralizing antibodies to block viral sites binding to the hosts cellular receptors. Virus infection is mediated by the spike glycoprotein trimer on the virion surface via its receptor binding domain (RBD). Antibody response to this domain is an important outcome of the immunization and correlates well with viral neutralization. Here we show that macromolecular constructs with recombinant RBD conjugated to tetanus toxoid induce a potent immune response in laboratory animals. Some advantages of the immunization with the viral antigen coupled to tetanus toxoid have become evident such as predominant IgG immune response due to affinity maturation and long-term specific B-memory cells. This paper demonstrates that subunit conjugate vaccines can be an alternative for COVID-19, paving the way for other viral conjugate vaccines based on the use of small viral proteins involved in the infection process.

immunology↗

bioRxiv2020

Lifetime genealogical divergence within plants leads to epigenetic mosaicism in the long lived shrub Lavandula latifolia (Lamiaceae)

O_LIEpigenetic mosaicism is a possible source of within-plant phenotypic heterogeneity, yet its frequency and developmental origin remain unexplored. This study examines whether the extant epigenetic heterogeneity within long-lived Lavandula latifolia (Lamiaceae) shrubs reflects recent epigenetic modifications experienced independently by different plant parts or, alternatively, it is the cumulative outcome of a steady lifetime process. C_LIO_LILeaf samples from different architectural modules were collected from three L. latifolia plants and characterized epigenetically by global DNA cytosine methylation and methylation state of methylation-sensitive amplified fragment length polymorphism markers (MS-AFLP). Epigenetic characteristics of modules were then assembled with information on the branching history of plants. Methods borrowed from phylogenetic research were used to assess genealogical signal of extant epigenetic variation and reconstruct within-plant genealogical trajectory of epigenetic traits. C_LIO_LIPlants were epigenetically heterogeneous, as shown by differences among modules in global DNA methylation and variation in the methylation states of 6-8% of MS-AFLP markers. All epigenetic features exhibited significant genealogical signal within plants. Events of epigenetic divergence occurred throughout the lifespan of individuals and were subsequently propagated by branch divisions. C_LIO_LIInternal epigenetic diversification of L. latifolia individuals took place steadily during their development, a process which eventually led to persistent epigenetic mosaicism. C_LI

plant biology↗

bioRxiv2020

Principal component analysis of RNA-seq data unveils a novel prostate cancer-associated gene expression signature

Prostate cancer (Pca) is a highly heterogeneous disease and the second more common tumor in males. Molecular and genetic profiles have been used to identify subtypes and guide therapeutic intervention. However, roughly 26% of primary Pca are driven by unknown molecular lesions. We use Principal Component Analysis (PCA) and custom RNAseq-data normalization to identify a gene expression signature which segregates primary PRAD from normal tissues. This Core-Expression Signature (PRAD-CES) includes 33 genes and accounts for 39% of data complexity along the PC1-cancer axis. The PRAD-CES is populated by protein-coding (AMACR, TP63, HPN) and RNA-genes (PCA3, ARLN1), validated/predicted biomarkers (HOXC6, TDRD1, DLX1), and/or cancer drivers (PCA3, ARLN1, PCAT-14). Of note, the PRAD-CES also comprises six over-expressed LncRNAs without previous Pca association, four of them potentially modulating drivers genes TMPRSS2, PRUNE2 and AMACR. Overall, our PCA capture 57% of data complexity within PC1-3. GO enrichment and correlation analysis comprising major clinical features (i.e., Gleason Score, AR Score, TMPRSS2-ERG fusion and Tumor Cellularity) suggest that PC2 and PC3 gene signatures may describe more aggressive and inflammation-prone transitional forms of PRAD. Of note, surfaced genes may entail novel prognostic biomarkers and molecular alterations to intervene. Particularly, our work uncovered RNA genes with appealing implications on Pca biology and progression.

cancer biology↗

bioRxiv2020

Maturation of Purkinje cell firing properties relies on granule cell neurogenesis

Preterm infants that suffer cerebellar insults often develop motor disorders and cognitive difficulty. Granule cells are especially vulnerable, and they likely instigate disease by impairing the function of Purkinje cells. Here, we use regional genetic manipulations and in vivo electrophysiology to test whether granule cells help establish the firing properties of Purkinje cells during postnatal mouse development. We generated mice that lack granule cell neurogenesis and tracked the structural and functional consequences on Purkinje cells in these agranular pups. We reveal that Purkinje cells fail to acquire their typical connectivity and morphology, and the formation of characteristic Purkinje cell firing patterns is delayed by one week. We also show that the agranular pups have impaired motor behaviors and vocal skills. These data argue that granule cell neurogenesis sets the maturation time window for Purkinje cell function and refines cerebellar-dependent behaviors.

neuroscience↗

bioRxiv2020

Double-stranded RNA bending by AU-tract sequences

Sequence-dependent structural deformations of the DNA double helix (dsDNA) have been extensively studied, where adenine tracts (A-tracts) provide a striking example for global bending in the molecule. In contrast to dsDNA, much less is known about how the nucleotide sequence affects bending deformations of double-stranded RNA (dsRNA). Using all-atom microsecond long molecular dynamics simulations we found a sequence motif consisting of alternating adenines and uracils, or AU-tracts, that bend the dsRNA helix by locally compressing the major groove. We experimentally tested this prediction using atomic force microscopy (AFM) imaging of long dsRNA molecules containing phased AU-tracts. AFM images revealed a clear intrinsic bend in these AU-tracts molecules, as quantified by a significantly lower persistence length compared to dsRNA molecules of arbitrary sequence. The bent structure of AU-tracts here described might play a role in sequence-specific recognition of dsRNAs by dsRNA-interacting proteins or impact the folding of RNA into intricate tertiary and quaternary structures.

biophysics↗

bioRxiv2019

Understanding the paradoxical mechanical response of in-phase A-tracts at different force regimes

A-tracts are A:T rich DNA sequences that exhibit unique structural and mechanical properties associated with several functions in vivo. The crystallographic structure of A-tracts has been well characterized. However, their response to forces remains unknown and the variability of their flexibility reported for different length scales has precluded a comprehensive description of the mechanical properties of these molecules. Here, we rationalize the mechanical properties of A-tracts across multiple length scales using a combination of single-molecule experiments and theoretical polymer models applied to DNA sequences present in the C. elegans genome. Atomic Force Microscopy imaging shows that phased A-tracts induce long-range ([~]200 nm) bending. Moreover, the enhanced bending originates from an intrinsically bent structure rather than as a consequence of larger flexibility. In support of this, our data were well described with a theoretical model based on the worm-like chain model that includes intrinsic bending. Magnetic tweezers experiments confirm that the observed bent is intrinsic to the sequence and does not rely on particular ionic conditions. Using optical tweezers, we assess the local rigidity of A-tracts at high forces and unravel an unusually stiff character of these sequences, as quantified by their large stretch modulus. Our work rationalizes the complex multiscale flexibility of A-tracts, shedding light on the cryptic character of these sequences.

biophysics↗

bioRxiv2019

Enabling community-based metrology for wood-degrading fungi

Lignocellulosic biomass could support a greatly-expanded bioeconomy. Current strategies for using biomass typically rely on single-cell organisms and extensive ancillary equipment to produce precursors for downstream manufacturing processes. Alternative forms of bioproduction based on solid-state fermentation and wood-degrading fungi can enable more direct means of manufacture. However, such practices are often ad hoc and not readily reproducible. We sought to develop standard reference strains, substrates, measurements, and methods sufficient to begin to enable reliable reuse of mycological materials and products. Specifically, we show that a widely-available and globally-regularized consumer product (Pringles) can support the growth of wood-degrading fungi, and that growth on Pringles can be correlated with growth on a fully-traceable and compositionally characterized substrate (NIST Reference Material 8492 Eastern Cottonwood Biomass). So established, five laboratories were able to compare measurements of wood-fungus performance via a simple radial extension growth rate assay. Reliable reuse of materials, measures, and methods is necessary to enable distributed bioproduction processes that can be adopted at all scales, from local to industrial.

synthetic biology↗

bioRxiv2019

Optimal design of single-cell RNA sequencing experiments for cell-type-specific eQTL analysis

Single-cell RNA-sequencing (scRNA-Seq) is a compelling approach to simultaneously measure cellular composition and state which is impossible with bulk profiling approaches. However, it has not yet become a widely used tool in population-scale analyses, due to its prohibitively high cost. Here we show that given the same budget, the statistical power of cell-type-specific expression quantitative trait loci (eQTL) mapping can be increased through low-coverage per-cell sequencing of more samples rather than high-coverage sequencing of fewer samples. We also show that multiple experimental designs with different numbers of samples, cells per sample and reads per cell could have similar statistical power, and choosing an appropriate design can yield large cost savings especially when multiplexed workflows are considered. Finally, we provide a practical approach on selecting cost-effective designs for maximizing cell-type-specific eQTL power.

bioinformatics↗

bioRxiv2018

DNA crookedness regulates DNA mechanical properties at short length scales

Sequence-dependent DNA conformation and flexibility play a fundamental role in specificity of DNA-protein interactions. Here we quantify the DNA crookedness: a sequence-dependent deformation of DNA that consists on periodic bends of the base pair centers chain. Using molecular dynamics simulations, we found that DNA crookedness and its associated flexibility are bijective: unveiling a one-to-one relation between DNA structure and dynamics. This allowed us to build a predictive model to compute DNA stretching stiffness from solely its structure. Sequences with very little crookedness show extremely high stiffness and have been previously shown to form unstable nucleosomes and promote gene expression. Interestingly, the crookedness can be tailored by epigenetic modifications, known to affect gene expression. Our results rationalize the idea that the DNA sequence is not only a chemical code, but also a physical one that allows to finely regulate its mechanical properties and, possibly, its 3D arrangement inside the cell.

biophysics↗