Biology subjects

Hussaini, A.

Publications and source records attributed to Hussaini, A..

3 recordsLinked to original sources

bioRxiv2021

IL7R is required for hematopoietic stem cell reconstitution of tissue-resident lymphoid cells

Traditional, adult-derived lymphocytes that circulate provide adaptive immunity to infection and pathogens. However, subsets of lymphoid cells are also found in non-lymphoid tissues and are called tissue-resident lymphoid cells (TLCs). TLCs encompass a wide array of cell types that span the spectrum of innate-to-adaptive immune function. Unlike traditional lymphocytes that are continuously generated from hematopoietic stem cells (HSCs), many TLCs are of fetal origin and poorly generated from adult HSCs. Here, we sought to understand the development of murine TLCs across multiple tissues and therefore probed the roles of Flk2 and IL7R, two cytokine receptors with known roles in traditional lymphopoiesis. Using Flk2- and Il7r-Cre lineage tracing models, we found that peritoneal B1a cells, splenic marginal zone B (MZB) cells, lung ILC2s and regulatory T cells (Tregs) were highly labeled in both models. Despite this high labeling, highly quantitative, in vivo functional approaches showed that the loss of Flk2 minimally affected the generation of these cells in situ. In contrast, the loss of IL7R, or combined deletion of Flk2 and IL7R, dramatically reduced the cell numbers of B1a cells, MZBs, ILC2s, and Tregs both in situ and upon transplantation, indicating an intrinsic and more essential role for IL7R. Surprisingly, reciprocal transplants of WT HSCs showed that an IL7R-/- environment selectively impaired reconstitution of TLCs when compared to TLC numbers in situ. Taken together, our data revealed functional roles of Flk2 and IL7R in the establishment of tissue-resident lymphoid cells.

cell biology↗

bioRxiv2020

Interleukin 7 receptor (IL7R) is required for myeloid cell homeostasis and reconstitution by hematopoietic stem cells

Respiratory diseases are a leading cause of death worldwide, with highly varied vulnerability to disease between individuals. The underlying reasons of disease susceptibility are unknown, but often include a variable immune response in lungs. Recently, we identified a surprising novel role of the interleukin 7 receptor (IL7R), a primarily lymphoid-associated regulator, in fetal-specified, lung-resident macrophage development. Here, we report that traditional, hematopoietic stem cell-derived myeloid cells in the adult lung, peripheral blood, and bone marrow also depend on IL7R expression. Using single and double germline knockout models, we found that eosinophil numbers were reduced upon deletion of IL7R. We then employed two Cre recombinase models in lineage tracing experiments to test whether these cells developed through an IL7R+ pathway. Despite the impact of IL7R deletion, IL7R-Cre labeled only a minimal fraction of eosinophils. We therefore examined the intrinsic versus extrinsic requirement for IL7R in the production of eosinophils using reciprocal hematopoietic stem cell transplantation assays. These assays revealed that extrinsic, but not eosinophil-intrinsic, IL7R is required for eosinophil reconstitution by HSCs in the adult lung. To determine which external factors may be influencing eosinophil development and survival, we performed a cytokine array analysis between wild-type and IL7R-deficient mice and found several differentially regulated proteins. These findings expand upon our previous publication that IL7R is required not only for proper lymphoid cell development and homeostasis, but also for myeloid cell homeostasis in tissues. HighlightsO_LILoss of IL7R resulted in significantly fewer eosinophils in adult mice C_LIO_LIIL7R-Cre lineage tracing revealed minimal labeling of eosinophils C_LIO_LIIL7R-deficient HSCs robustly reconstituted eosinophils in a WT host C_LIO_LIWT HSCs failed to fully reconstitute eosinophils in IL7R-/- hosts C_LIO_LISeveral cytokines are differentially expressed in WT and IL7R-deficient mice C_LI

immunology↗

bioRxiv2018

Attenuation of Aβ-associated hyperactivity reduces Aβ and tau pathology along the entorhinal cortex-hippocampal network

High levels of the amyloid-beta (A{beta}) peptide have been shown to disrupt neuronal function and induce hyperexcitability but it is unclear what effects A{beta}-associated hyperexcitability may have on tauopathy pathogenesis or propagation in vivo. Using a novel transgenic mouse line to model the impact of hAPP/A{beta} accumulation on tauopathy in the entorhinal cortex-hippocampal (EC-HIPP) network, we demonstrate that hAPP aggravates EC tau aggregation and accelerates pathological tau spread into the hippocampus. In vivo recordings revealed a strong role for hAPP/A{beta}, but not tau, in the emergence of EC neuronal hyperactivity and impaired theta rhythmicity. Chemogenetic attenuation of A{beta}-associated hyperactivity led to reduced hAPP/A{beta} accumulation and reduction of pathological tau in downstream hippocampus. These data strongly support the hypothesis that in Alzheimers disease (AD), A{beta}-associated hyperactivity accelerates the progression of pathological tau along vulnerable neuronal circuits, and demonstrates the utility of chronic, neuromodulatory approaches in ameliorating AD pathology in vivo.

neuroscience↗