Identifying an Apical Ectodermal Ridge (AER) signature in embryonic day 11.5 mouse forelimb.
Ontology highlight
ABSTRACT: The apical ectodermal ridge (AER) is a transient ectodermal population of cells that defines the dorso-ventral border of the developing limb bud. It functions as a major signaling centre that, through the secretion of various growth factors including FGF8, instructs the growth and patterning of the developing limb. We have identified that the AER expresses markers of cellular senescence and wanted to examine if there was any overlap with oncogene-induced senescence, an adult form of senescence induced in premalignant lesions. To achieve this, we microdissected the AER from embryonic day 11.5 mouse embryos. In addition, we collected the surface ectoderm from the proximal limb bud, that was not senescent and profiled both populations, to identify those genes that are enriched in the AER The AER was microdissected from embryonic day 11.5 mouse forelimb. Surface ectoderm from the posterior limb was used as a comparative control. Samples from 2-3 mice were pooled for each replicate, for 3-4 replicates.
Project description:The apical ectodermal ridge (AER) is a transient ectodermal population of cells that defines the dorso-ventral border of the developing limb bud. It functions as a major signaling centre that, through the secretion of various growth factors including FGF8, instructs the growth and patterning of the developing limb. We have identified that the AER expresses markers of cellular senescence and wanted to examine if there was any overlap with oncogene-induced senescence, an adult form of senescence induced in premalignant lesions. To achieve this, we microdissected the AER from embryonic day 11.5 mouse embryos. In addition, we collected the surface ectoderm from the proximal limb bud, that was not senescent and profiled both populations, to identify those genes that are enriched in the AER
Project description:Samples used for hybridization consisted of non-pooled (NP) RNA extracts from 8 groups in each of two time periods after drug administration: oil vehicle treated control embryonic limb bud mesoderm and ectoderm, phosphate buffered saline vehicle control embryonic limb bud mesoderm and ectoderm, acetazolamide treated embryonic limb bud mesoderm and ectoderm, and cadmium sulfate treated embryonic limb bud mesoderm and ectoderm. Forty-eight hybridization experiments were on non-pooled (NP) individual RNA extracts. Experiment Overall Design: Samples used for hybridization consisted of non-pooled (NP) RNA extracts from 8 groups in each of two time periods after drug administration: oil vehicle treated control embryonic limb bud mesoderm and ectoderm, phosphate buffered saline vehicle control embryonic limb bud mesoderm and ectoderm, acetazolamide treated embryonic limb bud mesoderm and ectoderm, and cadmium sulfate treated embryonic limb bud mesoderm and ectoderm. Forty-eight hybridization experiments were on non-pooled (NP) individual RNA extracts.
Project description:Samples used for hybridization consisted of non-pooled (NP) RNA extracts from 8 groups in each of two time periods after drug administration: oil vehicle treated control embryonic limb bud mesoderm and ectoderm, phosphate buffered saline vehicle control embryonic limb bud mesoderm and ectoderm, acetazolamide treated embryonic limb bud mesoderm and ectoderm, and cadmium sulfate treated embryonic limb bud mesoderm and ectoderm. Forty-eight hybridization experiments were on non-pooled (NP) individual RNA extracts. Keywords: Cadmium or Acetazolamide drug course over time in embryonic limb mesoderm and ectoderm.
Project description:Vertebrate Hox genes are key players in the establishment of structures during the development of the main body axis. Subsequently, they play important roles either in organizing secondary axial structures such as the appendages, or during homeostasis in postnatal stages and adulthood. Here we set up to analyze their elusive function in the ectodermal compartment, using the mouse limb bud as a model. We report that the HoxC gene cluster was globally co-opted to be transcribed in the distal limb ectoderm, where it is activated following the rule of temporal colinearity. These ectodermal cells subsequently produce various keratinized organs such as nails or claws. Accordingly, deletion of the HoxC cluster led to mice lacking nails (anonychia) and also hairs (alopecia), a condition stronger than the previously reported loss of function of Hoxc13, which is causative of the ectodermal dysplasia 9 (ECTD9) syndrome in human patients. We further identified, in mammals only, two ectodermal-specific enhancers located upstream the gene cluster, which act synergistically to regulate Hoxc genes in these ectodermal organs. Deletion of these enhancers alone or in combination revealed a strong quantitative component in the regulation of these genes in the ectoderm, suggesting that these two enhancers may have evolved along with mammals to provide the level of HOXC proteins necessary for the full development of hairs and nails.
Project description:Vertebrate Hox genes are key players in the establishment of structures during the development of the main body axis. Subsequently, they play important roles either in organizing secondary axial structures such as the appendages, or during homeostasis in postnatal stages and adulthood. Here we set up to analyze their elusive function in the ectodermal compartment, using the mouse limb bud as a model. We report that the HoxC gene cluster was globally co-opted to be transcribed in the distal limb ectoderm, where it is activated following the rule of temporal colinearity. These ectodermal cells subsequently produce various keratinized organs such as nails or claws. Accordingly, deletion of the HoxC cluster led to mice lacking nails (anonychia) and also hairs (alopecia), a condition stronger than the previously reported loss of function of Hoxc13, which is causative of the ectodermal dysplasia 9 (ECTD9) syndrome in human patients. We further identified, in mammals only, two ectodermal-specific enhancers located upstream the gene cluster, which act synergistically to regulate Hoxc genes in these ectodermal organs. Deletion of these enhancers alone or in combination revealed a strong quantitative component in the regulation of these genes in the ectoderm, suggesting that these two enhancers may have evolved along with mammals to provide the level of HOXC proteins necessary for the full development of hairs and nails.
Project description:During skin development, ectoderm-derived cells undergo precisely coordinated proliferation, differentiation, and adhesion to yield stratified epidermis. Disruptions in these processes can result in congenital anomalies including ectodermal dysplasia and harlequin ichthyosis. Protein Arginine Methyl Transferase 5 (PRMT5)—an enzyme responsible for methylating arginine residues in histones and other proteins—maintains progenitor status in germ and limb bud cells. Similarly, in vitro evidence suggests that PRMT5 prevents differentiation of basal keratinocytes, leading us to hypothesize that PRMT5 preserves the stem-cell phenotype of keratinocytes in vivo. To test this possibility, we generated conditional knockout (cKO) mice lacking Prmt5 in early ectoderm (E7.5), impacting the entire epidermis. Prmt5 cKOs exhibited gross skin defects, compromised skin barrier function, and reduced postnatal viability. Histological analyses revealed significant defects in epidermal stratification, without alterations in apoptosis or proliferation. Single-cell RNA and ATAC-seq analysis identified an atypical population of basal keratinocyte-like cells in Prmt5 cKOs, that exhibited a senescence-like program, characterized by increased Cdkn1a (p21), elevated senescence-associated secretory phenotype (SASP) molecules (Igfbp2), and decreased developmental transcription factor (Trp63) expression. Our findings suggest that PRMT5 prevents basal keratinocyte senescence by repressing Cdkn1a, shedding light on the epigenetic regulation of basal keratinocyte maintenance and senescence in congenital skin disorders.
Project description:During skin development, ectoderm-derived cells undergo precisely coordinated proliferation, differentiation, and adhesion to yield stratified epidermis. Disruptions in these processes can result in congenital anomalies including ectodermal dysplasia and harlequin ichthyosis. Protein Arginine Methyl Transferase 5 (PRMT5)—an enzyme responsible for methylating arginine residues in histones and other proteins—maintains progenitor status in germ and limb bud cells. Similarly, in vitro evidence suggests that PRMT5 prevents differentiation of basal keratinocytes, leading us to hypothesize that PRMT5 preserves the stem-cell phenotype of keratinocytes in vivo. To test this possibility, we generated conditional knockout (cKO) mice lacking Prmt5 in early ectoderm (E7.5), impacting the entire epidermis. Prmt5 cKOs exhibited gross skin defects, compromised skin barrier function, and reduced postnatal viability. Histological analyses revealed significant defects in epidermal stratification, without alterations in apoptosis or proliferation. Single-cell RNA and ATAC-seq analysis identified an atypical population of basal keratinocyte-like cells in Prmt5 cKOs, that exhibited a senescence-like program, characterized by increased Cdkn1a (p21), elevated senescence-associated secretory phenotype (SASP) molecules (Igfbp2), and decreased developmental transcription factor (Trp63) expression. Our findings suggest that PRMT5 prevents basal keratinocyte senescence by repressing Cdkn1a, shedding light on the epigenetic regulation of basal keratinocyte maintenance and senescence in congenital skin disorders.
Project description:A fundamental question in biology is how an undifferentiated field of cells acquires spatial pattern and undergoes coordinated differentiation. The development of the vertebrate limb is an important paradigm for understanding these processes. The skeletal and connective tissues of the developing limb all derive from a population of multipotent progenitor cells located in its distal tip. During limb outgrowth, these progenitors segregate into a chondrogenic lineage, located in the center of the limb bud, and soft connective tissue lineages located in its periphery. We report that the interplay of two families of signaling proteins, fibroblast growth factors (FGFs) and Wnts, coordinate the growth of the multipotent progenitor cells with their simultaneous segregation into these lineages. FGF and Wnt signals act together to synergistically promote proliferation while maintaining the cells in an undifferentiated, multipotent state, but act separately to determine cell lineage specification. Withdrawal of both signals results in cell cycle withdrawal and chondrogenic differentiation. Continued exposure to Wnt however, maintains proliferation and re-specifies the cells towards the soft connective tissue lineages. We have identified target genes that are synergistically regulated by Wnts and Fgfs, and show how these factors actively suppress differentiation and promote growth. Finally, we show how the spatial restriction of Wnt and FGF signals to the limb ectoderm and to a specialized region of it, the apical ectodermal ridge, controls the distribution of cell behaviors within the growing limb, and guides the proper spatial organization of the differentiating tissues. Keywords: transcriptional response to growth factor treatment Cells derived from mouse embryonic stage 11.5 limb buds were cultured and treated with purified Wnt3a protein or vehicle controls. The transcriptional response was detected using spotted cDNA microarrays after 2 hrs or 4 hrs of treatment. 4 biological replicates were used per condition.