S. mediterranea ETS-1 regulates the function of cathepsin-positive cells and the epidermal lineage landscape via basement membrane remodeling

Abstract

Extracellular matrix (ECM) is an important component of stem cell niche. Remodelling of ECM mediated by ECM regulators such as MMPs plays a vital role in stem cell function. However, the mechanisms that modulate the function of ECM regulators in the stem cell niche are understudied. Here, we explored the role of the transcription factor (TF), ETS-1 expressed in the cathepsin+ cell population in regulating the expression of the ECM regulator, mt-mmpA, thereby modulating basement membrane thickness. In planarians, the basement membrane around the gut/inner parenchyma is thought to act as a niche for pluripotent stem cells. It has been shown that the early epidermal progenitors migrate outward from this region and progressively differentiate to maintain the terminal epidermis. Our data shows thickening of basement membrane in the absence of ets-1 results in defective migration of stem cells progeny. Furthermore, the absence of ets-1 led to a defective epidermal progenitor landscape, in spite of its lack of expression in those cell types. Together, our results demonstrate the active role of ECM remodelling in regulating tissue homeostasis and regeneration in planaria.

Ets-1 transcription factor regulates glial cell regeneration and function in planarians

“…Planarian ets-1 is expressed widely throughout the mesenchyme (Fig 4A) and has been reported to play roles in specification and maintenance of pigment cells and other cathepsin + cell types (Dubey et al ., 2022; He et al ., 2017). Prior studies on planarian ets-1 reported either no role in impacting estrella expression (He et al ., 2017) or decreased calamari expression in the head only (Dubey et al ., 2022). To uncover the full impact of ets-1 on glial cells, we optimized an RNAi paradigm by adjusting numbers and dosage of dsRNA feedings (Fig.…”

“…Continuous knockdown of ets-1 eventually leads to animal death (Fig S5)(Dubey et al ., 2022). This led us to ask how ets-1 affects cell types beyond glia and pigment cells (Dubey et al ., 2022; He et al ., 2017). Single cell RNA sequencing (scRNA-seq) atlases cluster planarian pigment cells and glial cells with other cells that express cathepsin (Fincher et al ., 2018; Plass et al ., 2018)(Fig S6A).…”

“…Our RT-qPCR data thus paint a complex picture of the roles for ets-1 in cathepsin + cell types outside of pigment cells and glia, but we do not see universal downregulation of transcripts that fits neatly with the conclusion that ets- 1 (RNAi) affects all cells in the cathepsin + cluster in the same way. We also re-analyzed previously published RNA-seq data on ets-1 (RNAi) animals that utilized different RNAi and amputation paradigms (Dubey et al ., 2022). We did not see consistent, significant downregulation of genes enriched in cathepsin + cell subtypes that would indicate a uniform loss of some or all cathepsin + cell types (Fig S6F, Table S4).…”

“…Analysis for early time point regeneration of asexual and sexual planarian glial expression was performed from previously published RNA-sequencing data (Davies et al, 2017;Roberts-Galbraith et al, 2016) and plotted using GraphPad Prism9. Reanalysis of ets-1(RNAi) gene expression across different cathepsin + subclusters was performed using previously published RNA-sequencing data (Dubey et al, 2022) and expression profiles provided in previous transcriptome data analysis (Fincher et al, 2018;Plass et al, 2018).…”

“…Human and mouse Ets-1 are expressed in astrocytes of the cortex and are involved in astrocyte differentiation (Amouyel et al ., 1988; Fleischman et al ., 1995). In planarians, previous studies indicate that ets-1 plays roles in several cell types, including pigment cells, glial cells, and other uncharacterized cathepsin + cells (Dubey et al ., 2022; He et al ., 2017), but a definitive function for ets-1 in glia has not yet been clearly established.…”