Biology subjects

Gallardo, C. M.

Publications and source records attributed to Gallardo, C. M..

6 recordsLinked to original sources

bioRxiv2026

Linking anterior cingulate sulcal variability to attention-deficit hyperactivity disorder behavior

Background: The anterior cingulate cortex (ACC) is consistently implicated in attention-deficit/hyperactivity disorder (ADHD). ACC variability, including its most variable structure, the paracingulate sulcus (PCGS), has been known since the late 1800s, and since then, has been linked to cognitive control, impulsivity, and psychiatric conditions comorbid with ADHD, including autism spectrum disorder and schizophrenia. Yet, the role of the PCGS in ADHD remains unexamined at the individual level. Methods: We characterized PCGS incidence, asymmetry, and morphology in 247 children and adolescents (144 ADHD: 10.9 +/- 2.73 years old, 75% male; 103 neurotypical: 12.2 +/- 3.17 years old, 50% male) from the ADHD-200 dataset. The PCGS was manually identified in FreeSurfer cortical surface reconstructions. Morphometric measures, including sulcal length, depth, and cortical thickness, were extracted and normalized to hemisphere-wide variables. Between-group analyses tested whether PCGS presence, asymmetry, and quantitative morphology differed by diagnosis, while behavioral analyses examined associations with inattention, hyperactivity-impulsivity, and cognitive measures. Age and gender were included as covariates. Results: Analyses revealed that, in both NT and ADHD individuals, there was significant leftward asymmetry in PCGS presence. Between groups, the PCGS was less likely to be present in individuals with ADHD in the left hemisphere. Leftward PCGS absence was also associated with significantly higher ADHD index and hyperactivity-impulsivity scores. Conclusions: These findings advance understanding of how early neurodevelopmental variation in cortical folding may serve as a structural intermediary between genetic liability and the behavioral expression of ADHD.

neuroscience↗

bioRxiv2024

MrHAMER2: high-accuracy long-read RNA sequencing to decode isoform-specific variation in viral transcripts during latency

Alternative splicing (AS) greatly expands the repertoire of proteins encoded by the human genome. Viruses have been shown to hijack AS cellular pathways to sustain replication or lead to latency. In HIV-1 infection, the virus integrates into the host genome, becoming a transcriptional unit that directly engages in AS to regulate its gene expression. Sequencing advances have enabled insights into HIV-1 gene expression dynamics during productive replication. However, viral isoform dynamics during latency remain largely uncharacterized due to the low abundance of spliced viral transcripts in associated CD4+ T cell subsets, making their accurate detection and quantification challenging. MrHAMER2 is a high-accuracy long-read RNA sequencing method that leverages dual Unique Molecular Identifier (UMI) tagging of cDNA to accurately capture and quantify full-length isoforms with high dynamic range and 99.968% single-nucleotide accuracy. We used MrHAMER2 to decode the spliced HIV-1 transcriptome in a primary CD4+ T cell model of latency and showed substantial changes in viral isoforms bearing intron retentions accompanied by changes in their potential to generate translatable protein.

genomics↗

bioRxiv2024

APHIX: Analysis Pipeline for HIV-1 Isoform eXploration Using Long-read RNA Sequencing Data

HIV-1 uses 4 major splice donors and 8 major splice acceptors as well as dozens of minor, cryptic, and uncharacterized splice sites to produce over one hundred distinct transcript isoforms from a single 9.2 kb genome. As a result, existing bioinformatic pipelines struggle to accurately analyze spliced HIV sequences due to the complex nature of HIV alternative splicing compared to human mRNA splicing. Previous approaches to identify HIV isoforms from long-read sequencing data used pipelines that are not publicly available, are convoluted to operate, or are locked into a specific HIV strain, which limits their wide adoption to other experimental designs or systems. To address this gap, we have developed a bioinformatic pipeline called APHIX that fully automates spliced isoform assignment, splice site usage quantification, and non-coding exon detection. APHIX takes a FASTQ/A of long-read transcripts and a HIV genome reference sequence and fully automates HIV isoform analysis. APHIX calculates splice site usage counts and percentages for each donor and acceptor site and their pairwise combinations, accurately assigns isoforms, and automatically identifies transcripts containing non-coding exons. APHIX is compatible with long-reads sequences generated from multiple platforms and library preps, including direct DNA and RNA sequencing. APHIX can also be adapted to multiple HIV-1 clades and strains by providing the appropriate reference sequence during bioinformatic processing. Overall, APHIX enables comprehensive processing of spliced sequences with reproducible results in a manner that is faster and easier to run compared to other methods.

bioinformatics↗

bioRxiv2022

Selective Ablation of 3' RNA ends and Processive RTs Facilitate Direct cDNA Sequencing of Full-length Host cell and Viral Transcripts

Alternative splicing (AS) is necessary for viral proliferation in host cells and a critical regulatory component of viral gene expression. Conventional RNA-seq approaches provide incomplete coverage of AS due to their short read-lengths and are susceptible to biases and artifacts introduced in prevailing library preparation methodologies. Moreover, viral splicing studies are often conducted separately from host cell transcriptome analysis, precluding an assessment of the viral manipulation of host splicing machinery. To address current limitations, we developed a quantitative full-length direct cDNA sequencing strategy to simultaneously profile viral and host cell transcripts. This nanopore-based approach couples processive reverse transcriptases with a novel one-step chemical ablation of 3 RNA ends (termed CASPR) which decreases ribosomal RNA reads and enriches for poly-adenylated coding sequences. We extensively validate our approach using synthetic reference transcripts and show CASPR doubles the breadth of coverage per transcript and increases detection of long transcripts (>4kb), while being functionally equivalent to PolyA+ selection for transcript quantification. We used our approach to interrogate host cell and HIV-1 transcript dynamics during viral reactivation and identified novel putative HIV-1 host factors containing exon skipping or novel intron retentions and delineated the HIV-1 transcriptional state associated with these differentially regulated host factors.

genomics↗

bioRxiv2021

Co-variation of viral recombination with single nucleotide variants during virus evolution revealed by CoVaMa

Adaptation of viruses to their environments occurs through the acquisition of both novel Single-Nucleotide Variants (SNV) and recombination events including insertions, deletions, and duplications. The co-occurrence of SNVs in individual viral genomes during their evolution has been well-described. However, unlike covariation of SNVs, studying the correlation between recombination events with each other or with SNVs has been hampered by their inherent genetic complexity and a lack of bioinformatic tools. Here, we expanded our previously reported CoVaMa pipeline (v0.1) to measure linkage disequilibrium between recombination events and SNVs within both short-read and long-read sequencing datasets. We demonstrate this approach using long-read nanopore sequencing data acquired from Flock House virus (FHV) serially passaged in vitro. We found SNVs that were either correlated or anti-correlated with large genomic deletions generated by nonhomologous recombination that give rise to Defective-RNAs. We also analyzed NGS data from longitudinal HIV samples derived from a patient undergoing antiretroviral therapy who proceeded to virological failure. We found correlations between insertions in the p6Gag and mutations in Gag cleavage sites. This report confirms previous findings and provides insights on novel associations between SNVs and specific recombination events within the viral genome and their role in viral evolution.

genetics↗

bioRxiv2021

MrHAMER yields highly accurate single molecule viral sequences enabling analysis of intra-host evolution

Technical challenges remain in the sequencing of RNA viruses due to their high intra-host diversity. This bottleneck is particularly pronounced when interrogating long-range co-evolution given the read-length limitations of next-generation sequencing platforms. This has hampered the direct observation of long-range genetic interactions that code for protein-protein interfaces with relevance in both drug and vaccine development. Here we overcome these technical limitations by developing a nanopore-based long-range viral sequencing pipeline that yields accurate single molecule sequences of circulating virions from clinical samples. We demonstrate its utility in observing the evolution of individual HIV Gag-Pol genomes in response to antiviral pressure. Our pipeline, called Multi-read Hairpin Mediated Error-correction Reaction (MrHAMER), yields >1000s viral genomes per sample at 99.9% accuracy, maintains the original proportion of sequenced virions present in a complex mixture, and allows the detection of rare viral genomes with their associated mutations present at <1% frequency. This method facilitates scalable investigation of genetic correlates of resistance to both antiviral therapy and immune pressure, and enable the identification of novel host-viral and viral-viral interfaces that can be modulated for therapeutic benefit.

genomics↗