Tcf21 as a Founder Transcription Factor in Specifying Foxd1 Cells to the Juxtaglomerular Cell Lineage.

ABSTRACT

Renin is crucial for blood pressure regulation and electrolyte balance, and its expressing cells arise from Foxd1+ stromal progenitors. However, the factors guiding these progenitors toward the renin-secreting cell fate are not fully understood. Tcf21, a basic helix-loop-helix (bHLH) transcription factor, is essential in kidney development. Utilizing Foxd1 Cre/+ ;Tcf21 f/f and Ren1 dCre/+ ;Tcf21 f/f mouse models, we investigated the role of Tcf21 in the differentiation of Foxd1+ progenitor cells into juxtaglomerular (JG) cells. Immunostaining and in-situ hybridization demonstrated significantly fewer renin-positive areas and altered renal arterial morphology in Foxd1 Cre/+ ;Tcf21 f/f kidneys compared with controls, indicating Tcf21's necessity for renin cell emergence. However, Tcf21 inactivation in renin-expressing cells ( Ren1 dCre/+ ;Tcf21 f/f ) did not recapitulate this phenotype, suggesting Tcf21 is dispensable once renin cell identity is established. Integrated analysis of single-cell RNA sequencing (scRNA-seq) and single-cell assay for transposase-accessible chromatin sequencing (scATAC-seq) on GFP+ cells (stromal lineage) from E12, E18, P5, and P30 Foxd1 Cre/+ ;Rosa26 mTmG control kidneys revealed that Tcf21 expression peaks at embryonic day 12, crucial for early JG cell specification. Subsequent analyses confirmed Tcf21's critical role in early kidney development, with expression declining as development progresses. Our results highlight the temporal and spatial dynamics of Tcf21, showing its importance in the early specification of Foxd1+ cells into JG cells. These findings provide new insights into the molecular mechanisms governing JG cell differentiation and underscore Tcf21's pivotal role in kidney development. The data suggest that Tcf21 expression in Foxd1+ progenitors is essential for the specification of renin-expressing JG cells, but once renin cell identity is assumed, Tcf21 becomes redundant. NEW & NOTEWORTHY This manuscript provides novel insights into the role of Tcf21 in the differentiation of Foxd1+ cells into JG cells. Utilizing integrated scRNA-seq and scATAC-seq, the study reveals that Tcf21 expression is crucial during early embryonic stages, with its peak at embryonic day 12. The findings demonstrate that inactivation of Tcf21 leads to fewer renin-positive areas and altered renal arterial morphology, underscoring the importance of Tcf21 in the specification of renin-expressing JG cells and kidney development.