Simon Andrews

Reciprocal transcription factor networks govern tissue-resident ILC3 subset function and identity.
Fiancette R, Finlay CM, Willis C, Bevington SL, Soley J, Ng STH, Baker SM, Andrews S, Hepworth MR, Withers DR

Innate lymphoid cells (ILCs) are guardians of mucosal immunity, yet the transcriptional networks that support their function remain poorly understood. We used inducible combinatorial deletion of key transcription factors (TFs) required for ILC development (RORγt, RORα and T-bet) to determine their necessity in maintaining ILC3 identity and function. Both RORγt and RORα were required to preserve optimum effector functions; however, RORα was sufficient to support robust interleukin-22 production among the lymphoid tissue inducer (LTi)-like ILC3 subset, but not natural cytotoxicity receptor (NCR) ILC3s. Lymphoid tissue inducer-like ILC3s persisted with only selective loss of phenotype and effector functions even after the loss of both TFs. In contrast, continued RORγt expression was essential to restrain transcriptional networks associated with type 1 immunity within NCR ILC3s, which coexpress T-bet. Full differentiation to an ILC1-like population required the additional loss of RORα. Together, these data demonstrate how TF networks integrate within mature ILCs after development to sustain effector functions, imprint phenotype and restrict alternative differentiation programs.

Nature immunology, 1, 1, 23 Sep 2021

TGFβ signalling is required to maintain pluripotency of human naïve pluripotent stem cells.
Osnato A, Brown S, Krueger C, Andrews S, Collier AJ, Nakanoh S, Quiroga Londoño M, Wesley BT, Muraro D, Brumm AS, Niakan KK, Vallier L, Ortmann D, Rugg-Gunn PJ

The signalling pathways that maintain primed human pluripotent stem cells (hPSCs) have been well characterised, revealing a critical role for TGFβ/Activin/Nodal signalling. In contrast, the signalling requirements of naive human pluripotency have not been fully established. Here, we demonstrate that TGFβ signalling is required to maintain naive hPSCs. The downstream effector proteins - SMAD2/3 - bind common sites in naive and primed hPSCs, including shared pluripotency genes. In naive hPSCs, SMAD2/3 additionally bind to active regulatory regions near to naive pluripotency genes. Inhibiting TGFβ signalling in naive hPSCs causes the downregulation of SMAD2/3-target genes and pluripotency exit. Single-cell analyses reveal that naive and primed hPSCs follow different transcriptional trajectories after inhibition of TGFβ signalling. Primed hPSCs differentiate into neuroectoderm cells, whereas naive hPSCs transition into trophectoderm. These results establish that there is a continuum for TGFβ pathway function in human pluripotency spanning a developmental window from naive to primed states.

eLife, 10, 1, 31 08 2021

IL-7R signaling activates widespread V and D gene usage to drive antibody diversity in bone marrow B cells.
Baizan-Edge A, Stubbs BA, Stubbington MJT, Bolland DJ, Tabbada K, Andrews S, Corcoran AE

Generation of the primary antibody repertoire requires V(D)J recombination of hundreds of gene segments in the immunoglobulin heavy chain (Igh) locus. The role of interleukin-7 receptor (IL-7R) signaling in Igh recombination has been difficult to partition from its role in B cell survival and proliferation. With a detailed description of the Igh repertoire in murine IL-7Rα bone marrow B cells, we demonstrate that IL-7R signaling profoundly influences V gene selection during V-to-DJ recombination. We find skewing toward 3' V genes during de novo V-to-DJ recombination more severe than the fetal liver (FL) repertoire and uncover a role for IL-7R signaling in D-to-J recombination. Transcriptome and accessibility analyses suggest reduced expression of B lineage transcription factors (TFs) and targets and loss of D and V antisense transcription in IL-7Rα B cells. Thus, in addition to its roles in survival and proliferation, IL-7R signaling shapes the Igh repertoire by activating underpinning mechanisms.

Cell reports, 36, 2, 13 Jul 2021