Biology subjects

Fitzgerald, S.

Publications and source records attributed to Fitzgerald, S..

10 recordsLinked to original sources

bioRxiv2026

Epidemiology and phylodynamic analysis of canine distemper virus circulating in Michigan, USA

Canine distemper virus (CDV) is a highly contagious generalist pathogen that can cause significant mortality in domestic dogs and wild mammals. Due to the fast-evolving nature of CDV and its global spread, epizootic events and the emergence of new strains have been frequently reported. In Michigan, CDV surveillance from 2008 to 2018 was previously reported. Here, we combine and extend these data through 2023 to bring together 16 years of CDV surveillance in wild mammals in Michigan. We also sequenced CDV strains originating from both wildlife and domestic dogs to examine viral evolution across host populations. To facilitate interpretation of these data in both local and global contexts, we developed a Nextstrain workflow for CDV, enabling interactive visualization of viral evolution over time and geographic space. Our data show persistence of CDV in Michigan mammals during the study period and point to temporal, geographic, and host factors associated with CDV occurrence. Phylogenetic analysis using the newly built Nextstrain workflow showed that three CDV lineages--America-3, America-5, and Canada-1--are currently circulating in both wild and domestic animals in Michigan. The Nextstrain workflow enables reproducible, scalable integration of genomic sequencing into local surveillance and provides an updateable platform for ongoing and future surveillance efforts. This study demonstrates the value of coupling wildlife surveillance and diagnostic testing with genomic sequencing to identify lineage turnover and anticipate changes in viral behavior.

microbiology↗

bioRxiv2026

Systemic mutagen exposures reported by normal kidney cell genomes

Lifestyle, environmental and other exposures to exogenous mutagens generate somatic mutations in normal human cells in vivo and increase cancer risk. However, the global repertoire of exogenous mutagen exposures is uncertain. The mutational signatures of mutagens in normal tissues offer opportunities to detect such exposures and survey them at population level. Using single-molecule duplex sequencing of normal kidney (n=319) and blood (n=272) samples from 10 countries, we show that normal kidney cell genomes report an extensive repertoire of somatic mutational signatures. Microdissection of kidney structures revealed that proximal tubules exhibit higher mutation rates than other components of the nephron and most normal cell types despite low cell division rates. This is explained by marked enrichment of mutational signatures due to known exogenous carcinogenic mutagens including the plant-derived aristolochic acids, as well as several signatures of unknown causes including an unknown agent prevalent in Japan (SBS12), and signatures of uncertain origins (SBS40b and SBS40c). The results suggest the existence of multiple, common, systemically circulating mutagens affecting human populations and indicate that the genomes of kidney proximal tubule cells report such exposures with high sensitivity.

genomics↗

bioRxiv2025

Evaluating sequencing strategies for endometrial microbiome profiling in endometrial cancer: a comparative study of short- and long-read 16S rRNA approaches

BackgroundEndometrial cancer (EC) is the most common gynaecological malignancy globally, with rising incidence and notable disparities in outcomes. In New Zealand, EC rates have increased significantly, particularly among M[a]ori and Pacific women, who face higher risks of advanced disease and poorer outcomes. Microbial dysbiosis has been implicated in EC pathogenesis, but characterising the uterine microbiome is challenging due to low microbial biomass and high contamination risk. AimsThis study aimed to pilot a protocol that could inform the preparation of a larger cohort trial. Short-read Illumina MiSeq and long-read Oxford Nanopore Technologies (ONT) 16S rRNA gene sequencing were investigated to profile the uterine microbiome in people with EC. Methods and ResultsUterine and vaginal swabs were analysed to assess platform performance in terms of DNA recovery, sequencing success, diversity metrics, and taxonomic resolution. The impact of sample freezing or immediate lysis prior to DNA extraction was also evaluated. ONT sequencing provided enhanced species-level resolution and improved detection of low-abundance taxa but showed variable performance in low-yield samples. Freezing prior to cell DNA extraction modestly increased bacterial 16S copy numbers and improved community consistency. Contamination was a problem across both platforms, particularly in low-biomass samples, but can be minimised during data analysis. ConclusionThis study provides practical guidance for sequencing platform selection and sample handling in uterine microbiome research. Our findings support future efforts to elucidate microbial contributions to EC pathogenesis and highlight the importance of rigorous contamination control. Importantly, this is the first presentation of a New Zealand cohort and contributes valuable data from an underrepresented population and informs future research in diverse clinical settings.

cancer biology↗

bioRxiv2021

Towards Biophysical Markers of Depression Vulnerability

A major difficulty with treating psychiatric disorders is their heterogeneity: different neural causes can lead to the same phenotype. To address this, we propose describing the underlying pathophysiology in terms of interpretable, biophysical parameters of a neural model derived from the electroencephalogram. We analyzed data from a small patient cohort of patients with depression and controls. We constructed biophysical models that describe neural dynamics in a cortical network activated during a task that is used to assess depression state. We show that biophysical model parameters are biomarkers, that is, variables that allow subtyping of depression at a biological level. They yield a low dimensional, interpretable feature space that allowed description of differences between individual patients with depressive symptoms. They capture internal heterogeneity/variance of depression state and achieve significantly better classification than commonly used EEG features. Our work is a proof of concept that a combination of biophysical models and machine learning may outperform earlier approaches based on classical statistics and raw brain data.

neuroscience↗

bioRxiv2020

Prophage-dependent recombination drives genome structural variation and phenotypic heterogeneity in Escherichia coli O157:H7

The human zoonotic pathogen Escherichia coli O157 is defined by its extensive prophage repertoire including those that encode Shiga toxin, the factor responsible for inducing life-threatening pathology in humans. As well as introducing genes that can contribute to the virulence of a strain, prophage can enable the generation of large-chromosomal rearrangements (LCRs) by homologous recombination. This work examines the types and frequencies of LCRs across the major lineages of the O157 serogroup and defines the phenotypic consequences of specific structural variants. We demonstrate that LCRs are a major source of genomic variation across all lineages of E. coli O157 and by using both optical mapping and ONT long-read sequencing demonstrate that LCRs are generated in laboratory cultures started from a single colony and particular variants are selected during animal colonisation. LCRs are biased towards the terminus region of the genome and are bounded by specific prophages that share large regions of sequence homology associated with the recombinational activity. RNA transcriptional profiling and phenotyping of specific structural variants indicated that important virulence phenotypes such as Shiga toxin production, type 3 secretion and motility are affected by LCRs. In summary, E. coli O157 has acquired multiple prophage regions over time that act as genome engineers to continually produce structural variants of the genome. This structural variation is a form of epigenetic regulation that generates sub-population phenotypic heterogeneity with important implications for bacterial adaptation and survival. Author SummaryEscherichia coli has an open genome and has acquired genetic information over evolutionary time, often in the form of bacteriophages that integrate into the bacterial genome (prophages). E. coli O157 is a clonal serogroup that is found primarily in ruminants such as cattle but can cause life-threatening infections in humans. E. coli O157 isolates contain multiple prophages including those that encode Shiga-like toxins which are responsible for the more serious disease associated with human infections. We show in this study that many of these prophages exhibit large regions of sequence similarity that allow rearrangements to occur in the genome generating structural variants. These occur routinely during bacterial culture in the laboratory and the variants are detected during animal colonization. The variants generated can give the bacteria altered phenotypes, such as increased motility or toxin production which can be selected in specific environments and therefore represent a highly dynamic mechanism to generate variation in bacterial populations without a change in overall gene content.

microbiology↗

bioRxiv2019

Enhanced maturation of fast-spiking interneurons driven by mTOR activation

The use of stem cell derived neurons for cell-based therapies is limited by a protracted maturation. We present a novel approach for accelerating the post-mitotic maturation of human stem cell derived interneurons via the activation of mTOR signaling. Lox sites were placed within PTEN, a key mTOR inhibitor, in a cortical interneuron (CIn) reporter line. Following directed differentiation and purification by FACS, the CIns were exposed to Cre-expressing lentivirus, then transplanted into mouse neocortex or plated onto cultured rat neocortex. Input synaptogenesis and dendritogenesis was greatly enhanced in the PTEN-deleted CIns. Whole-cell recording of the PTEN-deleted CIns in slices of transplanted neocortex revealed multiple indices of enhanced maturation. Finally, we observed similar effects using transient, doxycycline-inducible activation of AKT. We thus present an inducible, reversible approach for accelerating the maturation of human stem cell derived CIns, and to study the influences of this disease-related signaling system in human neurons.

neuroscience↗

bioRxiv2019

Expert Curation of the Human and Mouse Olfactory Receptor Gene Repertoires Identifies Conserved Coding Regions Split Across Two Exons

Olfactory receptor (OR) genes are the largest multi-gene family in the mammalian genome, with over 850 in human and nearly 1500 genes in mouse. The expansion of the OR gene repertoire has occurred through numerous duplication events followed by diversification, resulting in a large number of highly similar paralogous genes. These characteristics have made the annotation of the complete OR gene repertoire a complex task. Most OR genes have been predicted in silico and are typically annotated as intronless coding sequences. Here we have developed an expert curation pipeline to analyse and annotate every OR gene in the human and mouse reference genomes. By combining evidence from structural features, evolutionary conservation and experimental data, we have unified the annotation of these gene families, and have systematically determined the protein-coding potential of each locus. We have defined the non-coding regions of many OR genes, enabling us to generate full-length transcript models. We found that 13 human and 41 mouse OR loci have coding sequences that are split across two exons. These split OR genes are conserved across mammals, and are expressed at the same level as protein-coding OR genes with an intronless coding region. Our findings challenge the long-standing and widespread notion that the coding region of a vertebrate OR gene is contained within a single exon.

genomics↗

bioRxiv2019

Systematic re-annotation of 191 genes associated with early-onset epilepsy unmasks de novo variants linked to Dravet syndrome in novel SCN1A exons

The early infantile epileptic encephalopathies (EIEE) are a group of rare, severe neurodevelopmental disorders, where even the most thorough sequencing studies leave 60-65% of patients without a molecular diagnosis. Here, we explore the incompleteness of transcript models used for exome and genome analysis as one potential explanation for lack of current diagnoses. Therefore, we have updated the GENCODE gene annotation for 191 epilepsy-associated genes, using human brain-derived transcriptomic libraries and other data to build 3,550 novel putative transcript models. The extended transcriptional footprint of these genes allowed for 294 intronic or intergenic variants, found in human mutation databases, to be reclassified as exonic, while a further 70 intronic variants were reclassified as splice-site proximal. Using SCN1A as a case study due to its close phenotype/genotype correlation with Dravet syndrome, we screened 122 people with Dravet syndrome, or a similar phenotype, with a panel of novel exon sequences representing eight established genes and identified two de novo SCN1A variants that now, through improved gene annotation can be ascribed to residing among novel exons. These two (from 122 screened patients, 1.6%) new molecular diagnoses carry significant clinical implications. Furthermore, we identified a previously-classified SCN1A intronic Dravet-associated variant that now lies within a deeply conserved novel exon. Our findings illustrate the potential gains of thorough gene annotation in improving diagnostic yields for genetic disorders. We would expect to find new molecular diagnoses in our 191 genes that were originally suspected by clinicians for patients, with a negative diagnosis.

genomics↗

bioRxiv2018

Co-circulating mumps lineages at multiple geographic scales

Despite widespread vaccination, eleven thousand mumps cases were reported in the United States (US) in 2016-17, including hundreds in Massachusetts, primarily in college settings. We generated 203 whole genome mumps virus (MuV) sequences from Massachusetts and 15 other states to understand the dynamics of mumps spread locally and nationally, as well as to search for variants potentially related to vaccination. We observed multiple MuV lineages circulating within Massachusetts during 2016-17, evidence for multiple introductions of the virus to the state, and extensive geographic movement of MuV within the US on short time scales. We found no evidence that variants arising during this outbreak contributed to vaccine escape. Combining epidemiological and genomic data, we observed multiple co-circulating clades within individual universities as well as spillover into the local community. Detailed data from one well-sampled university allowed us to estimate an effective reproductive number within that university significantly greater than one. We also used publicly available small hydrophobic (SH) gene sequences to estimate migration between world regions and to place this outbreak in a global context, but demonstrate that these short sequences, historically used for MuV genotyping, are inadequate for tracing detailed transmission. Our findings suggest continuous, often undetected, circulation of mumps both locally and nationally, and highlight the value of combining genomic and epidemiological data to track viral disease transmission at high resolution.

genomics↗

bioRxiv2017

Recurrent loss of heterozygosity correlates with clinical outcome in pancreatic neuroendocrine cancer

Pancreatic neuroendocrine tumors (pNETs) are uncommon cancers arising from pancreatic islet cells. Analysis of gene mutation, copy number and RNA expression of 57 sporadic pNETs showed that pNET genomes are dominated by aneuploidy. Remarkably, ~25% of pNETs had genomes characterized by recurrent loss of heterozygosity (LoH) of the same 10 chromosomes, accompanied by bi-allelic MEN1 inactivation, and these cases had generally poor clinical outcome. Another ~25% of all pNETs had chromosome 11 LoH and bi-allelic MEN1 inactivation, lacking the recurrent LoH pattern - these had universally good clinical outcome. Some level of aneuploidy was common, and overall ~80% of pNETs had LoH of [≥]1 chromosome. This aneuploidy led to changes in RNA expression at the level of whole chromosomes and allowed pathogenic germline variants (e.g. ATM) to be expressed unopposed, inactivating downstream tumor suppressor pathways. Some pNETs appear to utilize VHL gene methylation or mutation to activate pseudo-hypoxia. Contrary to expectation neither tumor morphology within well-differentiated pNETs nor single gene mutation had significant associations with clinical outcome, nor did expression of RNAs reflecting the activity of immune, differentiation, proliferative or tumor suppressor pathways. MEN1 was the only statistically significant recurrently mutated driver gene in pNETs. Only one pNET had clearly oncogenic and actionable SNVs (in PTEN and FLCN) confirmed by corroborating RNA expression changes. The two distinct patterns of aneuploidy described here, associated with markedly poor and good clinical outcome respectively, define a novel oncogenic mechanism and the first route to genomic precision oncology for this tumor type.

cancer biology↗