Biology subjects

Faraldo, M. M.

Publications and source records attributed to Faraldo, M. M..

6 recordsLinked to original sources

bioRxiv2025

Single-cell transcriptomics uncover conserved molecular mechanisms and functional diversification in multilayered epithelia

Multilayered epithelia, including skin, cervix, thymus, and prostate, arise from all three germ layers and perform diverse physiological functions, yet share a conserved layered architecture in which a supportive basal layer underlies differentiated suprabasal cells. To determine whether this common organization reflects a shared genetic program or tissue-specific regulation, we assembled a comprehensive single-cell atlas of 14 murine Multilayered epithelia. We identified a conserved p63-Notch axis that universally governs basal cell identity maintenance and suprabasal commitment. The p63-centered transcriptional program is shared, while Notch signaling recruits context-specific transcriptional modules to generate functional diversity. The layered architecture of epithelia spatially and temporally decouples conserved basal from context-specific suprabasal networks, compartmentalizing functional innovation across multilayered epithelia. Comparative genomics traces the p63-Notch axis to the root of vertebrates over 500 million years ago, showing that it was repeatedly co-opted through the incorporation of newly evolved genes in the suprabasal domain to generate novel epithelial functions. Our work establishes that evolution of multilayered epithelia operates through modular, compartmentalized diversification of a conserved scaffold, providing a unifying principle for how complex tissues achieve functional innovation while preserving structural integrity.

cell biology↗

bioRxiv2024

Conserved signals orchestrate self-organization and symmetry breaking of bi-layered epithelia during development and regeneration

Organ development relies on complex molecular mechanisms that guide initially homogeneous populations of stem cells to differentiate into specialized cell types within defined spatial patterns. While stable during homeostasis, the proper spatial organization of cell types must be re-established in case of tissue injury for successful regeneration of organ shape and function. How cells commit to a differentiation path is a central question in stem cell research; however, the coordination between tissue geometry and cell fate specification remains enigmatic. To elucidate the molecular mechanisms instructing self-organization and symmetry breaking of epithelial stem cells, we developed a multi-faceted approach combining in vitro organoids, ex vivo embryonic tissue explants, and single-cell quantitative imaging to investigate the dynamic acquisition of cell fate in four bi-layered epithelia, during embryonic development but also in regeneration. Our findings indicate that tissue architecture is the primary determinant of cell fate decisions in these tissues. Upon the initial cell internalization event, the homogeneous population of stem cell break symmetry. Through genetic and pharmacological perturbations, we have demonstrated that a tightly coordinated interplay between Hippo/YAP and Notch signaling is essential for conveying information from tissue architecture to functional cell differentiation and stem cell potency restriction. Globally, this study uncovers the inherent capacity of stem cells to self-organize into multicellular structures, where the precise position of each differentiated cell is critical to instruct their differentiation choices during embryonic development and regeneration.

developmental biology↗

bioRxiv2024

Contractile fibroblasts are recruited to the growing mammary epithelium to support branching morphogenesis

Fibroblasts are stromal cells found in connective tissue that are critical for organ development, homeostasis, and disease. Single-cell transcriptomic analyses have revealed a high level of inter- and intra-organ heterogeneity of fibroblasts. However, the functional implications and lineage relations of different fibroblast subtypes remain unexplored, especially in the mammary gland. Here we provide a comprehensive characterization of pubertal mammary fibroblasts, achieved using single-cell RNA sequencing, spatial mapping, and in vivo lineage tracing. Notably, we discovered a transient niche-forming population of specialized contractile fibroblasts that exclusively localize around the tips of the growing mammary epithelium and are recruited from the surrounding fat pad. Using functional organoid-fibroblast co-cultures we reveal that different fibroblast populations can acquire contractile features when in direct contact with the epithelium, promoting morphogenesis. In summary, our exhaustive characterization of these specialized cells provides new insights into mammary fibroblast heterogeneity and implicates their functional relevance for branching morphogenesis and lineage hierarchy during mouse mammary gland development.

developmental biology↗

bioRxiv2022

Positional cues underlie cell fate specification during branching morphogenesis of the embryonic mammary epithelium

How cells coordinate morphogenetic cues and fate specification during development is a fundamental question at the basis of tissue formation. Lineage tracing studies have demonstrated that many stratified epithelia, including the mammary gland, first arise from multipotent stem cells, which are progressively replaced by distinct pools of unipotent progenitors that maintain tissue homeostasis postnatally. The lack of specific markers for early fate specification in the mammary gland has prevented the delineation of the features and spatial localization of lineage-committed progenitors that co-exist with multipotent stem cells (MaSCs) during tissue development. Here, using single-cell RNA-sequencing across 4 stages of embryonic development, we reconstructed the differentiation trajectories of multipotent mammary stem cells towards basal and luminal fate. Our data revealed that MaSCs can already be resolved into distinct populations exhibiting lineage commitment at the time coinciding with the first sprouting events of mammary branching morphogenesis (E15.5). By visualizing gene expression across our developmental atlas, we provide novel molecular markers for committed and multipotent MaSCs, and define their spatial distribution within the developing tissue. Furthermore, we show that the mammary embryonic mesenchyme is composed of two spatially-restricted cell populations, representing the sub-epithelial and dermal mesenchyme. Mechanistically, we explored the communication between different subsets of mesenchymal and epithelial cells, using time-lapse analysis of mammary embryonic explant cultures, and reveal that mesenchymal-produced FGF10 accelerates embryonic mammary branching morphogenesis without affecting cell proliferation. Altogether, our data elucidate the spatiotemporal signals underlying lineage specification of multipotent mammary stem cells and uncover the paracrine interactions between epithelial and mesenchymal cells that guide mammary branching morphogenesis.

developmental biology↗

bioRxiv2021

In vivo imaging of mammary epithelial cell dynamics in response to lineage-biased Wnt/Beta-catenin activation

Real-time, in vivo imaging provides an essential window into the spatiotemporal cellular and molecular events contributing to tissue development and pathology. By coupling longitudinal intravital imaging with genetic lineage tracing, here we captured the earliest cellular events underlying the impact of active Wnt/{beta}-catenin signaling on the organization and differentiation of the mammary epithelium. This enabled us to interrogate how Wnt/{beta}-catenin regulates the dynamics of distinct subpopulations of mammary epithelial cells in vivo and in real time. We show that {beta}-catenin stabilization, when targeted to either of the mammary luminal or basal epithelial lineages, invariably leads to cellular rearrangements that precipitate the formation of hyperplastic lesions that undergo squamous transdifferentiation. These results enhance our understanding of the earliest stages of hyperplastic lesion formation in vivo, and reveal that in mammary neoplastic development, {beta}-catenin activation dictates a hair-follicle/epidermal differentiation program independently of the targeted cell of origin.

cell biology↗

bioRxiv2020

RAB6 GTPase is a crucial regulator of the mammary secretory function controlling STAT5 activation

The Golgi-associated RAB GTPases, RAB6A and RAB6A, regulate anterograde and retrograde transport pathways from and to the Golgi. In vitro, RAB6A/A have been reported to be involved in several cellular functions, including, in addition to transport, cell division, migration, adhesion and polarity. However, their role remains poorly described in vivo, in particular in epithelial tissues. Here, we generated BlgCre; Rab6aF/F mouse presenting a specific deletion of Rab6a in the mammary luminal secretory lineage during gestation and lactation. Rab6a loss severely impaired the differentiation, maturation and maintenance of the secretory tissue, compromising lactation. It led to a decreased activation of STAT5, a key regulator of the lactogenic process primarily governed by prolactin. Data obtained with a human mammary epithelial cell line suggested that defective STAT5 activation might originate from a perturbed transport of the prolactin receptor, altering its membrane expression and signaling cascade. Despite the major functional defects observed upon Rab6a deletion, the polarized organization of the mammary epithelial bilayer was preserved. Altogether, our data reveal a crucial role for RAB6A/A in the lactogenic function of the mammary gland. They also suggest that the trafficking pathways controlled by RAB6A/A depend on cell type specialization and tissue context. SUMMARY STATEMENTThis study reveals a role for the Golgi-associated RAB GTPases, RAB6A/A, in the lactogenic function of the mammary gland.

developmental biology↗