Maxime Bouchard

Androgen deprivation induces extensive tissue remodelling in the prostate, characterized by epithelial cell attrition and acquisition of a progenitor-like state in residual luminal epithelial cells. The mechanisms driving differentiated epithelial cells toward a progenitor fate remain unclear. Here, we identify that prostate regression is mediated by the engulfment of apoptotic neighbours by epithelial cells and that efferocytosis promotes acquisition of a progenitor-like state. We show that epithelial cells are the predominant phagocytes during regression, engaging in temporally coordinated waves of apoptotic cell clearance. This process is accompanied by marked metabolic reprogramming, including increased aerobic glycolysis and lactate production. This coincides with enhanced histone lysine-lactylation at promoters of genes involved in autophagy, apoptosis regulation, and luminal progenitor identity. Blockade of efferocytosis in vivo via epithelial-specific expression of the dominant negative phosphatidylserine binding protein MFGE8-D89E impaired prostate regression and compromised the induction of the luminal progenitor marker Tacstd2. These findings reveal that epithelial efferocytosis is an essential mechanism that couples cell clearance and epithelial plasticity. This work establishes epithelial efferocytosis as a determinant of cell state transitions in the prostate, with implications for a direct role in castration-resistant prostate cancer and other regenerative or remodelling processes.

The kidney and upper urinary tract develop through reciprocal interactions between the ureteric bud and the surrounding mesenchyme. Ureteric bud branching forms the arborized collecting duct system of the kidney, while ureteric tips promote nephron formation from dedicated progenitor cells. While nephron progenitor cells are relatively well characterized, the origin of ureteric bud progenitors has received little attention so far. It is well established that the ureteric bud is induced from the nephric duct, an epithelial duct derived from the intermediate mesoderm of the embryo. However, the cell state transitions underlying the progression from intermediate mesoderm to nephric duct and ureteric bud remain unknown. Here we show that nephric duct morphogenesis results from the coordinated organization of four major progenitor cell populations. Using single cell RNA-seq and Cluster RNA-seq, we show that these progenitors emerge in time and space according to a stereotypical pattern. We identify the transcription factors Tfap2a/b and Gata3 as critical coordinators of this progenitor cell progression. This study provides a better understanding of the cellular origin of the renal collecting duct system and associated urinary tract developmental diseases, which may inform guided differentiation of functional kidney tissue.

Tissue homeostasis relies on the fine regulation between stem and progenitor cell maintenance and lineage commitment. In the adult prostate, stem cells have been identified in both basal and luminal cell compartments. However, basal stem/progenitor cell homeostasis is still poorly understood. We show that basal stem/progenitor cell maintenance is regulated by a balance between BMP5 self-renewal signal and GATA3 dampening activity. Deleting Gata3 enhances adult prostate stem/progenitor cells self-renewal capacity in both organoid and allograft assays. This phenotype results from a local increase in BMP5 activity in basal cells as shown by the impaired self-renewal capacity of Bmp5-deficient stem/progenitor cells. Strikingly, Bmp5 gene inactivation or BMP signaling inhibition with a small molecule inhibitor are also sufficient to delay prostate and skin cancer initiation of Pten-deficient mice. Together, these results establish BMP5 as a key regulator of basal prostate stem cell homeostasis and identifies a potential therapeutic approach against Pten-deficient cancers.

Summary: Owing to technical advances in single cell biology, the appreciation of cellular heterogeneity has increased, which has aided our understanding of organ function, homeostasis and disease progression. The oviduct (also known as the fallopian tube in humans) is the distal-most portion of the female reproductive tract. It is essential for reproduction and the proposed origin of high grade serous ovarian carcinoma (HGSOC). In mammals, the oviduct is morphologically segmented along the ovary-uterus axis into four evolutionally conserved regions. It is unknown however if there is a diversification of epithelial cell characteristics between these regions. In this study, we identified transcriptionally distinct populations of secretory and multiciliated cells restricted to the distal and proximal regions of the oviduct. We demonstrated that these distal and proximal populations are distinct lineages specified early in Müllerian duct development and are maintained separately. These results aid our understanding of epithelial development, homeostasis and initiation of disease from the oviduct.

Owing to technical advances in single cell biology, the appreciation of cellular heterogeneity has increased, which has aided our understanding of organ function, homeostasis and disease progression. The oviduct (also known as the fallopian tube in humans) is the distal-most portion of the female reproductive tract. It is essential for reproduction and the proposed origin of high grade serous ovarian carcinoma (HGSOC). In mammals, the oviduct is morphologically segmented along the ovary-uterus axis into four evolutionally conserved regions. It is unknown however if there is a diversification of epithelial cell characteristics between these regions. In this study, we identified transcriptionally distinct populations of secretory and multiciliated cells restricted to the distal and proximal regions of the oviduct. We demonstrated that these distal and proximal populations are distinct lineages specified early in Müllerian duct development and are maintained separately. These results aid our understanding of epithelial development, homeostasis and initiation of disease from the oviduct.

The GATA family of transcription factors is of crucial importance during embryonic development, playing complex and widespread roles in cell fate decisions and tissue morphogenesis. GATA proteins are essential for the development of tissues derived from all three germ layers, including the skin, brain, gonads, liver, hematopoietic, cardiovascular and urogenital systems. The crucial activity of GATA factors is underscored by the fact that inactivating mutations in most GATA members lead to embryonic lethality in mouse models and are often associated with developmental diseases in humans. In this Primer, we discuss the unique and redundant functions of GATA proteins in tissue morphogenesis, with an emphasis on their regulation of lineage specification and early organogenesis.

Significance: Apoptotic morphogenesis requires strict regulation as both excessive and insufficient cell death is detrimental to tissue function. Here we use the process of ureter maturation, wherein the ureter connects to the bladder by the apoptosis-mediated removal of the intervening common nephric duct (CND), to investigate this paradigm. We find that LAR family phosphatases antagonize cIAP1 activity by decreasing its stability, thereby releasing the brake on CND elimination. In addition, we demonstrate that Birc2 (cIAP1) mutant embryos exhibit increased CND apoptosis, leading to accelerated ureter maturation and vesicoureteral reflux. Together this highlights the importance of modulating the rate of apoptosis during morphogenesis, which may act as a morphogenetic timer to allow for appropriate tissue rearrangements during embryonic development.

Caudal somites are generated from a pool of progenitor cells located in the tailbud region. These progenitor cells form the presomitic mesoderm that gradually differentiates into somites under the action of the segmentation clock. The signals responsible for tailbud mesoderm progenitor pool maintenance during axial elongation are still elusive. Here, we show that Bmp signaling is sufficient to activate the entire mesoderm progenitor gene signature in primary cultures of caudal mesoderm cells. Bmp signaling acts through the key regulatory genes brachyury (T) and Nkx1-2 and contributes to the activation of several other regulators of the mesoderm progenitor gene network. In the absence of Bmp signaling, tailbud mesoderm progenitor cells acquire aberrant gene expression signatures of the heart, blood, muscle and skeletal embryonic lineages. Treatment of embryos with the Bmp inhibitor noggin confirmed the requirement for Bmp signaling for normal T expression and the prevention of abnormal lineage marker activation. Together, these results identify Bmp signaling as a non-cell-autonomous signal necessary for mesoderm progenitor cell homeostasis.

Martin Zenker, Corinne Antignac, Friedhelm Hildebrandt and colleagues report that mutations in OSGEP, TP53RK, TPRKB and LAGE3, genes encoding KEOPS-complex subunits, cause Galloway–Mowat syndrome, a recessive disease characterized by early-onset steroid-resistant nephrotic syndrome and microcephaly. Functional studies suggest that the phenotypes result from impaired protein translation, thus leading to endoplasmic reticulum stress and apoptosis. Galloway–Mowat syndrome (GAMOS) is an autosomal-recessive disease characterized by the combination of early-onset nephrotic syndrome (SRNS) and microcephaly with brain anomalies. Here we identified recessive mutations in OSGEP, TP53RK, TPRKB, and LAGE3, genes encoding the four subunits of the KEOPS complex, in 37 individuals from 32 families with GAMOS. CRISPR–Cas9 knockout in zebrafish and mice recapitulated the human phenotype of primary microcephaly and resulted in early lethality. Knockdown of OSGEP, TP53RK, or TPRKB inhibited cell proliferation, which human mutations did not rescue. Furthermore, knockdown of these genes impaired protein translation, caused endoplasmic reticulum stress, activated DNA-damage-response signaling, and ultimately induced apoptosis. Knockdown of OSGEP or TP53RK induced defects in the actin cytoskeleton and decreased the migration rate of human podocytes, an established intermediate phenotype of SRNS. We thus identified four new monogenic causes of GAMOS, describe a link between KEOPS function and human disease, and delineate potential pathogenic mechanisms.