Biology subjects

Pickett, B. E.

Publications and source records attributed to Pickett, B. E..

5 recordsLinked to original sources

bioRxiv2026

Host gene expression changes induced by an HIV-1 mutant associated with delayed AIDS progression reveal potential mechanisms

HIV-1 viral protein R (Vpr) is a multifunctional protein central to HIV-1 pathogenesis and progression to AIDS. Polymorphisms in vpr have been linked to varying rates of HIV-1 progression. Of note is the HIV-1 Vpr R77Q mutant, associated with delayed progression to AIDS (also as the long-term non-progressor phenotype, or LTNP). We previously demonstrated that the R77Q mutant promotes a non-inflammatory, apoptotic phenotype in CD4+ T cells. To investigate the mechanism underlying the R77Q-induced apoptotic phenotype, we performed RNA sequencing on a CD4+ T cell line, HUT78, infected with either a replication-competent wild-type strain (NL4-3) or the R77Q mutant. Our results show that at 72 hours post-infection, transcriptomes were heterogeneous, and differential expression analysis identified 289 differentially expressed genes (DEGs) in the R77Q vs. WT comparison. Functional enrichment analysis revealed enriched pathways associated with apoptosis. Gene ontology (GO) terms and GO connections also revealed an apoptotic signature. Although both viral strains upregulated pro-apoptotic genes, the R77Q mutant failed to upregulate some key anti-apoptotic genes such as bcl-2, while WT-infected cells displayed upregulation of those anti-apoptotic genes. Predicted protein-protein interaction within the Bcl-2 family local network also suggests that interactions within this network were substantially affected. Taken together, these findings provide a transcriptomic basis for our previous observations of enhanced apoptosis in R77Q-infected cells and highlight distinct host cell responses that may underlie delayed HIV-1 progression. These results may be useful in identifying new targets to delay AIDS progression. ImportanceThe R77Q mutant has been a long-standing variant of interest because of its association with long-term non-progressors (LTNPs), yet the mechanisms behind this phenotype remain poorly defined. We previously showed that the R77Q mutant is less cytotoxic, killing fewer cells than WT via a non-inflammatory apoptotic pathway while suppressing inflammatory cytokine release, possibly contributing to the LTNP phenotype. Here, we provide a transcriptomic basis for this phenotype and identify a potential novel loss-of-function mechanism in which R77Q-induced apoptosis arises from a failure to upregulate key anti-apoptotic genes. Defining host responses in the context of delayed HIV-1 progression offers novel insights into cellular networks that could inform future therapeutic strategies beyond the current antiviral approaches.

microbiology↗

bioRxiv2023

Genes associated with fitness and disease severity in the pan-genome of mastitis-associated Escherichia coli

Bovine mastitis caused by Escherichia coli may manifest as subclinical through severe acute disease and can be transient or persistent in nature. Little is known about bacterial factors that impact clinical outcomes or allow some strains to outcompete others in the mammary gland (MG) environment. Mastitis-associated E. coli (MAEC) may have distinctive characteristics which may contribute to the varied nature of the disease. In this study, we sequenced the genomes of 96 MAEC strains isolated from cattle with clinical mastitis (CM). We utilized clinical severity data to perform genome-wide association studies to identify accessory genes associated with strains isolated from mild or severe CM, or with high or low competitive fitness during in vivo competition assays. Genes associated with pathogenic or commensal strains isolated from bovine and avian sources were also identified. A type-2 secretion system (T2SS) and a chitinase (ChiA) exported by this system were strongly associated with pathogenic isolates compared with commensal strains. Strains carrying these genes also had higher competitive fitness during experimental intramammary infections. Deletion of chiA from MAEC isolates decreased their adherence to cultured bovine mammary epithelial cells, suggesting that the increased fitness associated with strains possessing this gene may be due to better attachment in the MG. ImportanceBovine mastitis caused by MAEC compromises animal health and inflicts substantial product losses in dairy farming. Given their high levels of intraspecies genetic variability, virulence factors of commonly used MAEC model strains may not be relevant to all members of this group. Here we analyzed clinical data as well as fitness (quantified in a mouse MG model) of diverse MAEC isolates to identify accessory genes that contribute to infection. We demonstrated a novel role for chitinase in promoting attachment to mammary epithelial cells. Reverse genetic approaches can be applied to the collection of strains and their complete genome sequences that we have presented here. Overall, these results provide a much richer understanding of MAEC and suggest bacterial processes that may underlie the clinical diversity associated with mastitis and their adaptation to this unique environment.

microbiology↗

bioRxiv2021

Single-Cell RNA Sequencing Characterizes the Molecular Heterogeneity of the Larval Zebrafish Optic Tectum

The optic tectum (OT) is a multilaminated midbrain structure that acts as the primary retinorecipient in the zebrafish brain. Homologous to the mammalian superior colliculus, the OT is responsible for the reception and integration of stimuli, followed by elicitation of salient behavioral responses. While the OT has been the focus of functional experiments for decades, less is known concerning specific cell types, microcircuitry, and their individual functions within the OT. Recent efforts have contributed substantially to the knowledge of tectal cell types; however, a comprehensive cell catalog is incomplete. Here we contribute to this growing effort by applying single-cell RNA-sequencing (scRNA-seq) to characterize the transcriptomic profiles of tectal cells labeled by the transgenic enhancer trap line y304Et(cfos:Gal4;UAS:Kaede). We sequenced 13,320 cells, a 4X cellular coverage, and identified 25 putative OT cell populations. Within those cells, we identified several mature and developing neuronal populations, as well as non-neuronal cell types including oligodendrocytes, microglia, and radial glia. Although most mature neurons demonstrate GABAergic activity, several glutamatergic populations are present, as well as one glycinergic population. We also conducted Gene Ontology analysis to identify enriched biological processes, and computed RNA velocity to infer current and future transcriptional cell states. Finally, we conducted in situ hybridization to validate our bioinformatic analyses and spatially map select clusters. In conclusion, the larval zebrafish OT is a complex structure containing at least 25 transcriptionally distinct cell populations. To our knowledge, this is the first time scRNA-seq has been applied to explore the OT alone and in depth.

neuroscience↗

bioRxiv2019

Collective interactions augment influenza A virus replication in a host-dependent manner

Infection with a single influenza A virus (IAV) is only rarely sufficient to initiate productive infection. Here, we exploit both single-cell approaches and whole-animal systems to show that IAV reliance on multiple infection can form an important species barrier to infection. Namely, we find that H9N2 subtype viruses representative of those circulating widely at the poultry-human interface exhibit acute dependence on collective interactions in mammalian systems. This need for multiple infection is greatly reduced in the natural host. Quantification of incomplete viral genomes showed that their complementation accounts for the more moderate reliance on coinfection seen in avian cells, but not the added reliance seen in mammalian cells. This finding suggests an additional form of virus-virus interaction is needed to support infection in mammalian cells. Genetic mapping implicated the PA gene segment as a major driver of this phenotype and quantification of viral RNA synthesis indicated that both replication and transcription were affected. These findings indicate that multiple distinct mechanisms underlie IAV reliance on multiple infection and underscore the importance of virus-virus interactions in IAV infection, evolution and emergence.

microbiology↗

bioRxiv2019

Peptide Arrays of Three Collections of Human Sera from Patients Infected with Mosquito-Borne Viruses

Global outbreaks and epidemics caused by emerging or re-emerging mosquito-borne viruses are becoming more common. These viruses belong to multiple genera including Flavivirus and Alphavirus and often cause non-specific or asymptomatic infection, which can confound viral prevalence studies. In addition, many acute phase diagnostic tests rely on the detection of viral components such as RNA or antigen. Standard serological tests are often not reliable for diagnosis after the acute phase due to cross-reactivity among viruses (e.g. flaviviruses). In order to contribute to development efforts for mosquito-borne serodiagnostics, we incubated 137 human sera on individual custom peptide arrays that consisted of over 866 unique peptides in quadruplicate. Our bioinformatics workflow to analyze these data incorporated machine learning, statistics, and B-cell epitope prediction. The unprocessed array data can be useful in separate meta-analyses that can be applicable to diverse efforts including the development of new pan-flavivirus antibodies, more accurate epitope mapping, and vaccine development against these viral pathogens.

microbiology↗