Biology subjects

Garrett-Sinha, L. A.

Publications and source records attributed to Garrett-Sinha, L. A..

4 recordsLinked to original sources

bioRxiv2025

Host aging induces a senescent-like phenotype in neutrophils and altered transcriptional responses to Streptococcus pneumoniae

Aging drives increased susceptibility to respiratory infections by Streptococcus pneumoniae (pneumococci). Polymorphonuclear leukocytes (PMNs) are among the first responders in the lung following pneumococcal infection and are required for bacterial clearance. However, PMN antimicrobial function declines with age. To identify mechanisms underlying this decline, we performed RNA sequencing on PMNs in the lungs of young and old mice following pulmonary infection with S. pneumoniae. We observed significant transcriptomic differences across host age. Transcriptional analysis followed by functional validation revealed that in infected mice, PMNs from aged hosts failed to upregulate several effector activities including glycolysis and subsequent mitochondrial reactive oxygen species (ROS) production, which are necessary for bacterial killing by PMNs. Analysis of potential transcription factors controlling these changes indicated differential regulation by E2f2 in aged mice, which was linked to lower PMN differentiation resulting in more immature PMNs in the lungs of aged mice compared to young controls. Conversely, PMNs in aged mice displayed a higher senescence-associated secretory phenotype (SASP) score and upregulated pathways involved in cellular senescence. Follow-up functional characterization found that in uninfected hosts, PMNs in aged mice expressed higher levels of SASP factors IL-10, TNF, and ROS, had lower incidence of apoptosis, and had a higher proportion of cells positive for senescence-associated {beta}-galactosidase, features of a senescent-like phenotype. In conclusion, host aging is associated with altered PMN phenotypes, including a shift toward senescent-like energy-deficient cells, which may contribute to impaired host defense and represent potential targets for improved interventions against infection in older adults.

immunology↗

bioRxiv2024

Sequences within and upstream of the mouse Ets1 gene drive high level expression in B cells, but are not sufficient for consistent expression in T cells

The levels of transcription factor Ets1 are high in resting B and T cells, but are downregulated by signaling through antigen receptors and Toll-like receptors (TLRs). Loss of Ets1 in mice leads to excessive immune cell activation and development of an autoimmune syndrome and reduced Ets1 expression has been observed in human PBMCs in the context of autoimmune diseases. In B cells, Ets1 serves to prevent premature activation and differentiation to antibody-secreting cells. Given these important roles for Ets1 in the immune response, stringent control of Ets1 gene expression levels is required for homeostasis. However, the genetic regulatory elements that control expression of the Ets1 gene remain relatively unknown. Here we identify a topologically-associating domain (TAD) in the chromatin of B cells that includes the mouse Ets1 gene locus and describe an interaction hub that extends over 100 kb upstream and into the gene body. Additionally, we compile epigenetic datasets to find several putative regulatory elements within the interaction hub by identifying regions of high DNA accessibility and enrichment of active enhancer histone marks. Using reporter constructs, we determine that DNA sequences within this interaction hub are sufficient to direct reporter gene expression in lymphoid tissues of transgenic mice. Further analysis indicates that the reporter construct drives faithful expression of the reporter gene in mouse B cells, but variegated expression in T cells, suggesting the existence of T cell regulatory elements outside this region. To investigate how the downregulation of Ets1 transcription is associated with alterations in the epigenetic landscape of stimulated B cells, we performed ATAC-seq in resting and BCR-stimulated primary B cells and identified four regions within and upstream of the Ets1 locus that undergo changes in chromatin accessibility that correlate to Ets1 gene expression. Interestingly, functional analysis of several putative Ets1 regulatory elements using luciferase constructs suggested a high level of functional redundancy. Taken together our studies reveal a complex network of regulatory elements and transcription factors that coordinate the B cell-specific expression of Ets1.

genetics↗

bioRxiv2023

Ets1 and IL17RA cooperate to regulate autoimmune responses as well as skin immunity to Staphylococcus aureus

Ets1 is a lymphoid-enriched transcription factor that regulates B and T cell functions in development and disease. Mice that lack Ets1 (Ets1 KO) develop spontaneous autoimmune disease with high levels of autoantibodies. Naive CD4+ T cells isolated from Ets1 KO mice differentiate more readily to Th17 cells that secrete IL-17, a cytokine implicated in autoimmune disease pathogenesis. To determine if increased IL-17 production contributes to the development of autoimmunity in Ets1 KO mice, we crossed Ets1 KO mice to mice lacking the IL-17 receptor A subunit (IL17RA KO) to generate double knock out (DKO) mice. We found that the absence of IL17RA signaling did not prevent or ameliorate the autoimmune phenotype of Ets1 KO mice, but rather that DKO animals exhibited worse symptoms with striking increases in activated B cells and secreted autoantibodies. This was correlated with a prominent increase in the numbers of T follicular helper (Tfh) cells. In addition to the autoimmune phenotype, DKO mice also showed signs of immunodeficiency and developed spontaneous skin lesions colonized by Staphylococcus xylosus. When DKO mice were experimentally infected with S. aureus they were unable to clear the bacteria, suggesting a general immunodeficiency to Staphylococcal species. {gamma}{delta} T cells are important for control of skin Staphylococcal infections. We found that mice lacking Ets1 have a complete deficiency of the {gamma}{delta} T cell subset dendritic epidermal T cells (DETC), which are involved in skin wound healing responses. To determine if loss of DETC might promote susceptibility to Staph infection, we depleted DETC from IL17RA KO mice and found that the combined loss of DETC and IL-17 signaling leads to a failure to clear the infection. Our studies suggest that defects in wound healing, such as that caused by loss of DETC, can cooperate with impaired IL-17 responses to lead to increased susceptibility to skin Staph infections.

immunology↗

bioRxiv2021

Narcolepsy with cataplexy is caused by epigenetic silencing of hypocretin neurons

Narcolepsy with cataplexy is a chronic sleep disorder characterized by hypocretin deficiency. The condition is believed to result from autoimmune destruction of hypocretin (HCRT) neurons, although direct evidence is lacking and mere Hcrt gene inactivation causes full-blown narcolepsy in mice. Here we show that the expression of another hypothalamic neuropeptide, QRFP, is lost in mouse models with HCRT cell-ablation, but tends to be even increased in Hcrt gene knockout mice, suggesting that QRFP expression can be used as a proxy for the presence or absence of HCRT neurons. Similar to Hcrt knockout mice, narcolepsy patients show intact hypothalamic QRFP expression, and cerebrospinal fluid levels of QRFP peptide are increased, suggesting their HCRT neurons are intact. We show that the human HCRT gene promoter is methylation-sensitive in vitro, and is hypermethylated in the hypothalamus of patients selectively at a putative PAX5:ETS1 binding site within the proximal HCRT promoter. Ets1-KO mice display downregulated Hcrt expression, while pax5-ets1 knockdown in zebrafish causes decreased hcrt expression, decreased activity and sleep fragmentation, similar to narcolepsy patients. Our results suggest that HCRT neurons are alive, but epigenetically silenced, in the hypothalamus of narcolepsy patients, opening the possibility to reverse or cure narcolepsy.

neuroscience↗