Project description:Basal cell carcinoma initiating cells undergo profound and rapid reprogramming into embryonic hair follicle progenitor like fate upon SmoM2 expression. Activation of Wnt/M-NM-2-catenin signaling pathways is required in a cell autonomous manner for the reprogramming of adult IFE progenitors into EHFP-like fate as well as for tumor initiation. We used MA to define the molecular changes that occur in basal cell carcinoma initiating cells form the first oncogenic hit to the development of invasive tumor and further on to investigate the role of Wnt/M-NM-2-catenin signaling activation in molecular changes occurring early during BCC development. Basal interfollicular cells expressing SmoM2 were FACS isolated at different stages of tumor development and in M-NM-2-catenin LOF condition for RNA extraction and hybridization on Affymetrix microarrays. By comparing the transcriptional profile of SmoM2 expressing cells with FACS-isolated cells from littermate control mice, we determined a list of genes differentially regulated by SmoM2 expression as specific SmoM2 signature.
Project description:Basal cell carcinoma initiating cells undergo profound and rapid reprogramming into embryonic hair follicle progenitor like fate upon SmoM2 expression. Activation of Wnt/β-catenin signaling pathways is required in a cell autonomous manner for the reprogramming of adult IFE progenitors into EHFP-like fate as well as for tumor initiation. We used MA to define the molecular changes that occur in basal cell carcinoma initiating cells form the first oncogenic hit to the development of invasive tumor and further on to investigate the role of Wnt/β-catenin signaling activation in molecular changes occurring early during BCC development.
Project description:Sox9 is a transcription factor expressed in most solid tumors. However, the molecular mechanisms underlying Sox9 function during tumorigenesis remain unclear. Here, using a genetic mouse model of basal cell carcinoma (BCC), the most frequent cancer in human, we show that Sox9 is expressed from the earliest step of tumor formation in a Wnt/β-catenin dependent manner. Deletion of Sox9 together with the constitutive activation of Hedgehog (HH) signaling completely prevents BCC formation and leads to a progressive loss of oncogene expressing cells. Transcriptional profiling of oncogene expressing cells with Sox9 deletion, combined with in vivo ChIP-sequencing uncovers a cancer-specific gene network regulated by Sox9 that promotes stemness, extracellular matrix (ECM) deposition and cytoskeleton remodeling while repressing epidermal differentiation. Our study identifies the molecular mechanisms regulated by Sox9 that links tumor initiation and invasion. Sox9 ChIP-seq analysis in K14CreER SmoM2 cells.
Project description:The skin epidermis is a highly compartmentalised tissue consisting of a cornifying epithelium called the interfollicular epidermis (IFE) and associated hair follicles (HFs). Several stem cell populations have been described that mark specific sub compartments in the skin but none of them is IFE-specific. Here we identify Troy as a marker of IFE and HF infundibulum basal layer cells in embryonic and adult human and mouse epidermis. Genetic lineage-tracing experiments demonstrate that Troy-expressing basal cells contribute to long-term renewal of all layers of the cornifying epithelium. Single-cell transcriptomics and organoid assays of Troy-expressing cells as well as their progeny confirmed stem cell identity as well as the ability to generate differentiating daughter cells. In conclusion, we define Troy as a marker of epidermal basal cells that govern interfollicular epidermal renewal and cornification.
Project description:Here, we report a discrete population of keratinocytes, marked by Thy1, in the basal layer of the IFE. We find that basal keratinocytes expressing differential levels of Thy1 display distinct transcriptional signatures. Thy1+ keratinocytes do not express T cell markers, express a unique transcriptional profile, cycle significantly slower than epidermal progenitors and display significant expansion potential in vitro. Collectively, these results reveal a distinct stem cell population that plays a critical role in epidermal homeostasis and repair.
Project description:The skin interfollicular epidermis (IFE) is the first barrier against the external environment and its maintenance is critical for survival. Two seemingly opposite theories have been proposed to explain IFE homeostasis. One posits that IFE is maintained by a long-lived slow-cycling stem cell (SC) population that give rise to short-lived transit-amplifying (TA) cell progeny, while the other suggests that homeostasis is achieved by a single committed progenitor (CP) that balances stochastic fate. Here, we probed the cellular heterogeneity within the IFE using two different inducible CREER targeting IFE progenitors. Quantitative analysis of clonal fate data and proliferation dynamics demonstrate the existence of two distinct proliferative cell compartments composed of slow-cycling SC and CP, both of which undergo population asymmetric self-renewal. However, following wounding, only SCs contribute substantially to the repair and long-term regeneration of the tissue, while CP cells make a minimal and transient contribution. Transcriptional profile of InvCREER/RosaYFP and K14CREER/RosaYFP targeted FACS-isolated alpha6 integrin-high CD34-neg basal cells from mouse tail epidermis. Skin epidermis was removed from tail bone and incubated overnight in HBSS (Gibco) 0.25% trypsin (Gibco) at 4M-BM-0C. Epidermis was separated from the dermis and incubated on a rocking plate (100 rpm) at room temperature for 5 min. Basal cells were mechanically separated from the epidermis by flushing 10 times under the epidermis. Tissues were then cut in pieces of 1 mm2 with scalpel, and trypsin was neutralized by adding DMEM medium (Gibco) supplemented with 2% Chelex Fetal Calf Serum (FCS). Samples were filtrated on 70 and 40M-BM-5m filter (Falcon). Immunostaining was performed using biotin-conjugated anti-CD34 (clone RAM34; BD Biosciences) PE-conjugated anti-M-NM-16-integrin (clone GoH3; BD biosciences). Primary antibodies were washed with 2% FCS/PBS and cells were incubated for 30 min in APC conjugated streptavidin (BD Biosciences) secondary antibodies, on ice, with shaking every 10 min. Living K14- and involucrin-expressing epidermal cells were gated by forward scatter, side scatter, negative staining for Hoechst dye and by following the YFP signal. Basal cells from the interfollicular epidermis were targeted using CD34 negative alpha 6 high gating. Fluorescence-activated cell sorting analysis was performed using FACSAria I at high pressure (70 psi) and FACSDiva software (BD Biosciences). Sorted cells were harvested directly in the lysis buffer provided by the RNeasy microkit (QIAGEN) supplemented with 1M-BM-5l of beta-mercaptoethanol for every 100M-BM-5l of lysis buffer. RNA extraction was performed on freshly sorted cells according to the manufacturerM-bM-^@M-^Ys protocol.
Project description:We report global transcriptional profiles of epidermal basal cells from plantar skin of control mice, high fat diet-fed (HFD) mice and aged mice. By RNA-sequencing of FACS-isolated interfollicular epidermal (IFE) basal cells, we revealed that calcium signal-associated genes, which regulate differentiatin of keratinocytes,were enriched in the plantar skin of HFD and aged mice.
Project description:Although interfollicular epidermal (IFE) differentiation is thought to be stepwise as reflected in sharp boundaries between the basal, spinous, granular and cornified layers, this prediction has not been studied at a single cell resolution. We used single cell RNA-seq to show that IFE differentiation is best described as a single step gradualistic process with a large number of transition cells between the basal and spinous layer. RNA-velocity analysis identifies a commitment point that separates the plastic basal and transition cell state from the unidirectionally differentiating cells. We also show that GRHL3, best known for promoting IFE terminal differentiation, has a major function in suppressing epidermal stem cell expansion and the emergence of an abnormal stem cell state by suppressing Wnt signaling in stem cells.
Project description:The skin epidermis is constantly renewed throughout life. Disruption of the balance between renewal and differentiation can lead to uncontrolled growth and tumor initiation. Basal cell carcinoma (BCC) is the most frequent cancer in human. Cell competition is a biological process that leads to the elimination of cells by winner cells, which have been proposed to be important for tumour initiation. Recent studies identified somatic mutations in cancer drivers in normal tissues that get colonized by clones carrying oncogenic mutations. However, how the different oncogenic mutations impact the balance between renewal and differentiation and lead to clonal expansion, cell competition, tissue colonization and tumor development is currently unknown. Here, using multidisciplinary approaches combining in vivo clonal analysis using intra-vital microscopy, single cell analysis, and functional analysis, we defined at a single cell resolution in living animals how mutations associated with BCC development (SmoM2) affect clonal competition and tumor initiation in real time. We found that SmoM2 expression in the ear epidermis induces a stereotypical pattern of cell competition with clonal expansion leading tumor initiation and invasion. In contrast, SmoM2 expression in the back skin epidermis led to a similar clonal expansion that induces lateral cell competition but without inducing dermal invasion and tumor formation. Single cell analysis showed that oncogene expression is associated with a cellular reprogramming of adult interfollicular cells into embryonic hair follicle progenitor (EHFP) state in the ear but not in the back skin. Comparison between ear and back skin epidermis revealed a very different composition of the dermis with increased stiffness and a denser collagen 1 network in the back skin. Decreasing Collagen 1 expression in the back skin overcame the natural resistance of these cells to undergo EHFP reprogramming and tumor initiation following SmoM2 expression. Altogether our study demonstrates that ECM composition controls the mode of clonal competition and competence to undergo oncogenic transformation upon oncogene expression.
Project description:Sox9 is a transcription factor expressed in most solid tumors. However, the molecular mechanisms underlying Sox9 function during tumorigenesis remain unclear. Here, using a genetic mouse model of basal cell carcinoma (BCC), the most frequent cancer in human, we show that Sox9 is expressed from the earliest step of tumor formation in a Wnt/β-catenin dependent manner. Deletion of Sox9 together with the constitutive activation of Hedgehog (HH) signaling completely prevents BCC formation and leads to a progressive loss of oncogene expressing cells. Transcriptional profiling of oncogene expressing cells with Sox9 deletion, combined with in vivo ChIP-sequencing uncovers a cancer-specific gene network regulated by Sox9 that promotes stemness, extracellular matrix (ECM) deposition and cytoskeleton remodeling while repressing epidermal differentiation. Our study identifies the molecular mechanisms regulated by Sox9 that links tumor initiation and invasion.