Project description:During embryonic and postnatal development, organs and tissues grow steadily to achieve their final size at the end of puberty. However, little is known about the cellular dynamics that mediate postnatal growth. By combining in vivo clonal lineage tracing, proliferation kinetics, single-cell transcriptomics, and in vitro micro-pattern experiments, we resolved the cellular dynamics taking place during postnatal skin epidermis expansion. Our data revealed that harmonious growth is engineered by a single population of developmental progenitors presenting a fixed fate imbalance of self-renewing divisions with an ever-decreasing proliferation rate. Single-cell RNA sequencing revealed that epidermal developmental progenitors form a more uniform population compared with adult stem and progenitor cells. Finally, we found that the spatial pattern of cell division orientation is dictated locally by the underlying collagen fiber orientation. Our results uncover a simple design principle of organ growth where progenitors and differentiated cells expand in harmony with their surrounding tissues.
Project description:The purpose of this study was to define, at the single cell level, the transcriptionnal profile of murine tail epidermal basal cells during potsnatal growth and to compare with adult homeostatic basal cells. The analysis was performed on Lgr5DTR-EGFP mice (Tian et al., 2011)(knockin mice containing an Enhanced Green Fluorescent Protein (EGFP) under the control of the Lgr5 regulatory region), allowing to identify and exclude Lgr5-expressing cells of the bulge and basal cells of the interfollicular epidermis were enriched using EGFP negative, CD34 negative, alpha6 integrin positive gating. Our single-cell RNA sequencing revealed that epidermal basal cells at P7 form a more uniform population compared to adult basal cells and that heterogeneity starts to appear around P30.
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:Mammalian epidermis consists of three self-renewing compartments: the hair follicle, sebaceous gland and interfollicular epidermis. We generated knock-in alleles of murine Lgr6, a close relative to the Lgr5 stem cell gene. Lgr6 was expressed in the earliest embryonic hair placodes. In adult hair follicles, Lgr6+ cells resided in a previously uncharacterized region directly above the follicle bulge. They expressed none of the known bulge stem cell markers. Prenatal Lgr6+ cells established the hair follicle, sebaceous gland and interfollicular epidermis. Postnatally, Lgr6+ cells generated sebaceous gland and interfollicular epidermis, while contribution to hair lineages gradually diminished with age. Adult Lgr6+ cells executed long-term wound repair, including the formation of new hair follicles. We conclude that Lgr6 marks the most primitive epidermal stem cell.
Project description:Mammalian epidermis consists of three self-renewing compartments: the hair follicle, sebaceous gland and interfollicular epidermis. We generated knock-in alleles of murine Lgr6, a close relative to the Lgr5 stem cell gene. Lgr6 was expressed in the earliest embryonic hair placodes. In adult hair follicles, Lgr6+ cells resided in a previously uncharacterized region directly above the follicle bulge. They expressed none of the known bulge stem cell markers. Prenatal Lgr6+ cells established the hair follicle, sebaceous gland and interfollicular epidermis. Postnatally, Lgr6+ cells generated sebaceous gland and interfollicular epidermis, while contribution to hair lineages gradually diminished with age. Adult Lgr6+ cells executed long-term wound repair, including the formation of new hair follicles. We conclude that Lgr6 marks the most primitive epidermal stem cell. For the Lgr5 and Lgr6 stem cell comparison RNA was isolated from sorted GFPhi cell fractions of dorsal skin from Lgr5-EGFP-ires-CreERT2 mice and Lgr6-EGFP-ires-CreERT2, respectively (3 mice per group per sort).
