Biology subjects

DeFalco, T.

Publications and source records attributed to DeFalco, T..

11 recordsLinked to original sources

bioRxiv2026

Phosphorylation of TTL3 by BIK1 Functions as a Molecular Switch to Control Cellulose Biosynthesis under Salt Stress

Cellulose, a central structural component of plant cell walls, is produced by cellulose synthase complexes (CSCs) at the plasma membrane. Salinity stress is particularly damaging to cellulose biosynthesis, and therefore, plants have developed adaptive mechanisms to cope with these conditions. TETRATRICOPEPTIDE THIOREDOXIN-LIKE (TTL) proteins are essential for growth under salt stress and show a salt-dependent association with CSCs through an as-yet unknown mechanism. Here, we identify a phosphorylation-dependent regulatory mechanism linking salt stress signaling to cellulose biosynthesis through the coordinated action of TTL3 and the receptor-like cytoplasmic kinase BOTRYTIS-INDUCED KINASE 1 (BIK1). Phosphorylation of Serine 93 in the N-terminal intrinsically disordered region of TTL3 controls its localization, retaining it in the cytosol, while dephosphorylation promotes association with CSCs at the plasma membrane. Biochemical and genetic analysis identified BIK1 as the kinase responsible for TTL3-S93 phosphorylation, with bik1 mutants phenocopying the phosphoablative TTL3S93A in vivo. Transcriptomic analyses reveal a strong overlap of differentially expressed genes between bik1 and a cellulose-deficient mutant, supporting a broader role for BIK1 in cell wall regulation. Notably, TTL proteins do not appear to be involved in the assayed canonical immune responses, suggesting pathway specificity downstream of BIK1. Together, these findings define a signaling module that connects salt stress perception to CSCs regulation and establish BIK1-dependent TTL3 phosphorylation as a molecular switch for maintaining cell wall integrity under abiotic stress.

Plant Biology↗

bioRxiv2026

Macrophages regulate meiotic initiation and germ cell clearance in the developing ovary

Tissue-resident macrophages are increasingly recognized for their roles in promoting organogenesis, yet how macrophages are involved in fetal ovarian development remains unclear. In particular, little is known about ovarian macrophage ontogeny and how it relates to germ cell entry into meiosis and establishment of the oocyte reserve. Here we combine temporally-controlled lineage tracing of yolk-sac erythro-myeloid progenitors, fetal HSC-derived progenitors, and postnatal monocytes to map multi-wave seeding and remodeling of ovarian macrophages across fetal and early postnatal life. We identify three major resident subsets defined by MHCII and CSF1R that display distinct expansion kinetics and persistence, and we show that CCR2-dependent monocyte recruitment is required for efficient maturation of postnatal macrophage populations. Functionally, transient or sustained depletion of CSF1R fetal macrophages perturbs ovarian vascular growth and triggers precocious meiotic initiation without overt loss of germ cells, leading to persistent, premature meiotic progression. Extending macrophage depletion into late gestation disrupts perinatal physiological germ cell attrition despite rapid postnatal macrophage repopulation. Together, our findings establish ovarian macrophages as stage-specific regulators that couple immune ontogeny to ovarian morphogenesis and germ cell quality control during establishment of the oocyte reserve. One Sentence SummaryOvarian macrophages are required for the proper timing of germ cell meiotic entry and progression, vascular growth, and for the physiological clearance of germ cells during establishment of the oocyte reserve in perinatal stages.

developmental biology↗

bioRxiv2026

Prenatal corticosteroid exposure disrupts vascular-immune interactions and impairs steroidogenesis in the fetal testis

Antenatal corticosteroid (ACS) therapy, typically using dexamethasone (Dex), is a cornerstone of improving preterm infant survival by accelerating lung maturation. However, its systemic effects on other developing organs remain poorly understood. Here, we reveal a previously unrecognized impact of prenatal Dex exposure on fetal testis development, with implications for long-term male reproductive health. Analysis of fetal testes from a Dex-based ACS mouse model revealed that Dex suppressed androgen synthesis by reducing Leydig cell number and downregulating steroidogenic pathways. Dex also activated immune programs, inducing CD163 M2 macrophages and IL10 signaling, which promoted endothelial expansion. Despite these pro-angiogenic signals, vascular architecture was disrupted: capillary density and pericyte coverage declined, while blood vessel diameter increased. Transcriptomic analyses revealed downregulation of androgen response and cholesterol metabolism pathways, alongside upregulation of immune and coagulation signatures. Analyses of fetal ovaries revealed a sexually dimorphic and organ-specific effect of ACS therapy, in which ovarian gene expression remained unaffected. Our findings uncover an immune-vascular mechanism linking prenatal Dex exposure to impaired steroidogenesis, providing new insight into potentially broad effects of ACS therapy. One Sentence SummaryPrenatal corticosteroid exposure disturbs immune-vascular interactions and suppresses androgen synthesis in the fetal testis, revealing potentially widespread effects of a commonly used therapy.

developmental biology↗

bioRxiv2024

A perivascular niche supports endometrial epithelial regeneration

Endometrial regeneration is essential for reproductive cycles and pregnancies, allowing the endometrium to undergo repair and renewal after menstruation and parturition. Epithelial cells lining the uterine cavity are shed during each cycle, although remnant luminal and glandular epithelial cells can regenerate the lumen lining. It is presumed that adult stem/progenitor cells in the uterine stroma also contribute to this regeneration. However, the specific cell type(s) and the underlying mechanisms have not been determined. Herein, we use genetic lineage tracing assays in mice to identify Nestin+ perivascular cells as active contributors to epithelial regeneration. Notch signaling maintains Nestin+ perivascular cells in a quiescent state but these cells re-enter the cell cycle and differentiate into epithelial cells via estrogen-stimulated suppression of Notch signaling dependent on estrogen receptor alpha (ER/ESR1). These findings demonstrate that perivascular cells support epithelial regeneration and reveal a mechanism regulating the quiescence and activation of uterine perivascular cells.

cell biology↗

bioRxiv2023

Testis morphogenesis and fetal Leydig cell development are mediated through ERK signaling activated by platelet derived growth factor receptor alpha

Platelet derived growth factor receptor alpha (Pdgfra) plays a crucial role in the morphogenesis and differentiation of the fetal testis, but the molecular signaling involved in these processes remains unclear. Here, we use XY Pdgfra-null knock-in (KI) gonads to investigate the molecular mechanisms underlying Pdgfra-mediated testis cord formation and development of fetal Leydig cells (FLCs). The extracellular signal-regulated kinase (ERK) pathway, a well-known mitogen-activated protein kinase signaling pathway, was significantly inhibited in XY Pdgfra KI gonads, suggesting that ERK signaling is activated downstream of PDGFRA. Using ex vivo whole-organ culture, small interfering RNA (siRNA) cell culture methods, transwell assays and a genetic mouse model to disrupt ERK signaling in gonadal cells, we found that the ERK pathway promoted testis cord formation via early growth response 1 (Egr1)-mediated cell migration and regulated the expression of steroidogenic enzymes in FLCs via activating the transcription factor cAMP responsive element binding protein 1 (CREB; official name CREB1). These findings highlight the significance of PDGFRA and its downstream signaling in fetal testis morphogenesis and cellular differentiation, thus providing insights into the etiology of and potential therapeutic targets for disorders related to gonadal development.

developmental biology↗

bioRxiv2022

Testicular macrophages are recruited during a narrow time window by fetal Sertoli cells to promote organ-specific developmental functions

While macrophages are most commonly known for their roles in innate immunity, a growing body of evidence supports the idea that fetal-derived tissue-resident macrophages play developmental roles during organogenesis. In the testis, it has long been proposed that macrophages are important players in steroidogenesis and other testicular functions, but which macrophage populations are involved is unclear. We previously showed that macrophages play critical roles in fetal testis morphogenesis and reported the presence of 2 unique adult testicular macrophage populations, interstitial and peritubular. There has been some debate regarding the hematopoietic origins of testicular macrophages and whether distinct macrophage populations promote specific testicular functions. Here we have undertaken an extensive lineage-tracing study of mouse hematopoietic cells. We found that, while yolk-sac-derived macrophages comprise the earliest testicular macrophages, fetal hematopoietic stem cells (HSCs) give rise to monocytes that colonize the gonad during a narrow time window in mid-gestation, after which time HSCs no longer contribute to testicular macrophages. These long-lived monocytes, over the course of fetal and postnatal life, differentiate into testicular macrophages. Our data indicate that Sertoli cells, and not germ cells, are required for recruitment of immune cells and peritubular macrophage differentiation. Finally, we show that yolk-sac-derived macrophages and HSC-derived macrophages play distinct roles in testis cord morphogenesis, whereas interstitial macrophages promote adult Leydig cell proliferation and steroid production. Overall, our findings offer clarity regarding the origins of testicular macrophages and provide insight into the diversity of their tissue-specific developmental roles.

developmental biology↗

bioRxiv2021

Perivascular cells support folliculogenesis in the developing ovary

Granulosa cells, supporting cells of the ovary, are essential for ovarian differentiation by providing a nurturing environment for oogenesis. Sufficient numbers of granulosa cells are vital for establishment of follicles and the oocyte reserve; therefore, identifying the cellular source from which granulosa cells are derived is critical for understanding basic ovarian biology. One cell type that has received little attention in this field is the perivascular cell. Here we use lineage tracing and organ culture techniques in mice to identify ovarian Nestin+ perivascular cells as multipotent progenitors that contribute to granulosa, thecal, and pericyte lineages. Maintenance of these progenitors was dependent on vascular-mesenchymal Notch signaling. Ablation of postnatal Nestin+ cells resulted in a disruption of granulosa cell specification and an increased incidence of polyovular ovarian follicles, thus uncovering key roles for vasculature in ovarian differentiation. These findings may provide new insights into the origins of female gonad dysgenesis and infertility.

developmental biology↗

bioRxiv2021

Cdc42 activity in Sertoli cells is essential for maintenance of spermatogenesis

Sertoli cells are highly polarized testicular supporting cells that simultaneously nurture progressively maturing germ cells. Proper localization of polarity protein complexes within Sertoli cells, including those responsible for blood-testis barrier formation, are vital for successful spermatogenesis. However, the mechanisms and developmental timing that underlie the establishment of polarity are poorly understood. To investigate this aspect of testicular function, we conditionally deleted Cdc42, encoding a Rho GTPase involved in regulating cell polarity, specifically in Sertoli cells. Cdc42 deletion disrupted adult Sertoli cell maturation and localization of polarity proteins, but did not affect fetal and early postnatal testicular development, nor the onset of the first wave of spermatogenesis. By early adulthood, however, conditional knockout males exhibited a loss of spermatogenic cells, resulting in a complete lack of sperm. These findings demonstrate that Cdc42 plays an essential role in establishing adult Sertoli cell polarity and, thus, maintaining steady-state spermatogenesis and healthy sperm production.

developmental biology↗

bioRxiv2021

Loss of Mafb and Maf distorts myeloid cell ratios and disrupts fetal mouse testis vascularization and organogenesis

Testis differentiation is initiated when Sry in pre-Sertoli cells directs the gonad toward a male-specific fate. Sertoli cells are essential for testis development, but cell types within the interstitial compartment, such as immune and endothelial cells, are also critical for organ formation. Our previous work implicated macrophages in fetal testis morphogenesis, but little is known about genes underlying immune cell development during organogenesis. Here we examine the role of the immune-associated genes Mafb and Maf in mouse fetal gonad development, and we demonstrate that deletion of these genes leads to aberrant hematopoiesis manifested by supernumerary gonadal monocytes. Mafb;Maf double knockout embryos underwent initial gonadal sex determination normally, but exhibited testicular hypervascularization, testis cord formation defects, Leydig cell deficit, and a reduced number of germ cells. In general, Mafb and Maf alone were dispensable for gonad development; however, when both genes were deleted, we observed significant defects in testicular morphogenesis, indicating that Mafb and Maf work redundantly during testis differentiation. These results demonstrate previously unappreciated roles for Mafb and Maf in immune and vascular development and highlight the importance of interstitial cells in gonadal differentiation. Summary statementDeletion of Mafb and Maf genes leads to supernumerary monocytes in fetal mouse gonads, resulting in vascular, morphogenetic, and differentiation defects during testicular organogenesis.

developmental biology↗

bioRxiv2021

Polycomb suppresses a female gene regulatory network in Sertoli cells

Gonadal sex determination is controlled by the support cells of testes and ovaries. In testes, the epigenetic mechanism that maintains cellular memory to suppress female sexual differentiation remains unknown. Here, we show that Polycomb suppresses a female gene regulatory network in Sertoli cells, the specific support cells for postnatal testes. Through genetic ablation, we removed Polycomb repressive complex 1 (PRC1) from embryonic Sertoli cells after sex determination. PRC1-depleted postnatal Sertoli cells exhibited defective proliferation and cell death, leading to the degeneration of adult testes. In adult Sertoli cells, PRC1 suppressed the specific, critical genes required for granulosa cells, the support cells of ovaries, thereby inactivating the female gene regulatory network. The underlying chromatin of female genes was coated with Polycomb-mediated repressive modifications: PRC1-mediated H2AK119ub and PRC2-mediated H3K27me3. Taken together, we identify a critical mechanism centered on Polycomb that maintains the male fate in adult testes.

developmental biology↗

bioRxiv2020

FERONIA regulates FLS2 plasma membrane nanoscale dynamics to modulate plant immune signaling

Spatial partitioning is a propensity of biological systems orchestrating cell activities in space and time. The dynamic regulation of plasma membrane nano-environments has recently emerged as a key fundamental aspect of plant signaling, but the molecular components governing it are still mostly unclear. The receptor kinase FERONIA (FER) controls complex formation of the immune receptor kinase FLAGELLIN SENSING 2 (FLS2) with its co-receptor BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1 (BAK1), and this function is inhibited by the FER ligand RAPID ALKALANIZATION FACTOR 23 (RALF23). Here, we show that FER regulates the plasma membrane nanoscale organization of FLS2 and BAK1. Our study demonstrates that akin to FER, leucine-rich repeat (LRR) extensin (LRXs) proteins contribute to RALF23 responsiveness, regulate BAK1 nanoscale organization and immune signaling. Furthermore, RALF23 perception leads to rapid modulation of FLS2 and BAK1 nanoscale organization and its inhibitory activity on immune signaling relies on FER kinase activity. Our results suggest that perception of RALF peptides by FER and LRXs actively modulates the plasma membrane nanoscale landscape to regulate cell surface signaling by other receptor kinases.

plant biology↗