Long Non-Coding RNAs in Allergy

Northwestern University At Chicago, Evanston IL

Investigators

Abstract

PROJECT SUMMARY The overall goal of this proposal is to identify fundamental mechanisms controlling allergic responses by the long non-coding RNA (lncRNA) Morrbid. Type 2 allergic responses are characterized by the generation of CD4+ T helper type 2 (Th2) cells, and the recently identified IL-13+ T follicular helper (Tfh13) cells, which drive production of high-affinity anaphylactic IgE. Given their central role in allergy, understanding how T cells are programmed to become Th2 and Tfh13 cells could allow manipulation of T cell responses to mitigate allergy. Recent work has revealed a critical function for lncRNAs in immunity, opening up an exciting area of research that may uncover new targets and pathways for therapeutic intervention. lncRNAs do not encode proteins; rather, many produce functional RNA transcripts that are powerful regulators of cellular identity, function and survival. Our preliminary data show that the lncRNA Morrbid controls CD4+ T cell function and is required for type 2 immune responses in vivo. Single-cell RNA-sequencing (scRNA-Seq) of CD4+ T cells revealed Morrbid to be most highly expressed in Il13-expressing Th2 and Tfh13 cells, and Tfh13 cells are reduced during type 2 responses in Morrbid-/- mice. Our hypothesis is that Morrbid is an epigenetic regulator of Th2 and Tfh13 differentiation during allergic responses. In Aim 1 we will identify cell types that require Morrbid to generate type 2 immune responses. Using mice with a conditional Morrbid allele crossed to different Cre-expressing lines, we will test the function of Morrbid in dendritic cells, B cells, T cells, and Tfh cells during type 2 responses in vivo. We will analyze expression of human MORRBID in T cells from donors with or without allergies using scRNA-Seq, to determine whether Th2 and Tfh cells overexpress MORRBID in allergy. Finally, using CRISPR/Cas9-based epigenome editing in primary human T cells, we will determine the impact of MORRBID silencing and overexpression on CD4+ T helper cell polarization in vitro. In Aim 2 we will dissect molecular mechanisms by which the Morrbid locus regulates gene expression in T cells. To this end we have developed a novel genetic targeting strategy based on pre-tRNA processing to ablate lncRNA transcripts without blocking transcription in vivo. In Aim 3 we will map the Morrbid interactome to determine how Morrbid controls T cell function. To identify genes directly bound by Morrbid, we will employ a novel method that allows simultaneous mapping of both lncRNA-chromatin interactions and lncRNA-associated chromatin loops genome-wide, called RNA ChIA-PET (RNA-Chromatin Interaction Analysis by Paired-End Tag sequencing). To identify regulatory proteins interacting with Morrbid, we will use RAP-MS (RNA Antisense Purification coupled with Mass Spectrometry). Through completion of these Aims, we will elucidate new regulatory pathways controlling type 2 immunity that could potentially be exploited to treat allergy. In addition, we will have established and validated two novel tools of significant benefit to the research community which suffers from a dearth of standard methodology for analyzing lncRNA function; a lncRNA-specific gene- targeting approach, and a method to map genome-wide lncRNA-associated chromosomal interactions.