Project description:Runx2 and Axin2 regulate skeletal development. We recently determined that Axin2 and Runx2 molecularly interact in differentiating osteoblasts to regulate intramembranous bone formation, but the relationship between these factors in endochondral bone formation was unresolved. To address this, we examined the effects of Axin2 deficiency on the cleidocranial dysplasia (CCD) phenotype of Runx2+/- mice, focusing on skeletal defects attributed to improper endochondral bone formation. Axin2 deficiency unexpectedly exacerbated calvarial components of the CCD phenotype in the Runx2+/- mice; the endocranial layer of the frontal suture, which develops by endochondral bone formation, failed to mineralize in the Axin2-/-:Runx2+/-mice, resulting in a cartilaginous, fibrotic and larger fontanel than observed in Runx2+/- mice. Transcripts associated with cartilage development (e.g., Acan, miR140) were expressed at higher levels, whereas blood vessel morphogenesis transcripts (e.g., Slit2) were suppressed in Axin2-/-:Runx2+/-calvaria. Cartilage maturation was impaired, as primary chondrocytes from double mutant mice demonstrated delayed differentiation and produced less calcified matrix in vitro. The genetic dominance of Runx2 was also reflected during endochondral fracture repair, as both Runx2+/- and double mutant Axin2-/-:Runx2+/- mice had enlarged fracture calluses at early stages of healing. However, by the end stages of fracture healing, double mutant animals diverged from the Runx2+/- mice, showing smaller calluses and increased torsional strength indicative of more rapid end stage bone formation as seen in the Axin2-/- mice. Taken together, our data demonstrate a dominant role for Runx2 in chondrocyte maturation, but implicate Axin2 as an important modulator of the terminal stages of endochondral bone formation. 4 mice per genotype X 4 genotypes: wildtype (WT), Runx2+/- (R-Het), Axin2-/- (A-KO), Axin2-/-:Runx2+/- (A-KO:R-Het). Total = 16 samples
Project description:Runx2 and Axin2 regulate skeletal development. We recently determined that Axin2 and Runx2 molecularly interact in differentiating osteoblasts to regulate intramembranous bone formation, but the relationship between these factors in endochondral bone formation was unresolved. To address this, we examined the effects of Axin2 deficiency on the cleidocranial dysplasia (CCD) phenotype of Runx2+/-M-BM- mice, focusing on skeletal defects attributed to improper endochondral bone formation. Axin2 deficiency unexpectedly exacerbated calvarial components of the CCD phenotype in the Runx2+/-M-BM- mice; the endocranial layer of the frontal suture, which develops by endochondral bone formation, failed to mineralize in the Axin2-/-:Runx2+/-mice, resulting in a cartilaginous, fibrotic and larger fontanel than observed in Runx2+/-M-BM- mice. Transcripts associated with cartilage development (e.g., Acan, miR140) were expressed at higher levels, whereas blood vessel morphogenesis transcripts (e.g., Slit2) were suppressed in Axin2-/-:Runx2+/-calvaria. Cartilage maturation was impaired, as primary chondrocytes from double mutant mice demonstrated delayed differentiation and produced less calcified matrix in vitro. The genetic dominance of Runx2 was also reflected during endochondral fracture repair, as both Runx2+/-M-BM- and double mutant Axin2-/-:Runx2+/-M-BM- mice had enlarged fracture calluses at early stages of healing. However, by the end stages of fracture healing, double mutant animals diverged from the Runx2+/-M-BM- mice, showing smaller calluses and increased torsional strength indicative of more rapid end stage bone formation as seen in the Axin2-/-M-BM- mice. Taken together, our data demonstrate a dominant role for Runx2 in chondrocyte maturation, but implicate Axin2 as an important modulator of the terminal stages of endochondral bone formation. 4 mice per genotype X 4 genotypes: wildtype (WT), Runx2+/- (R-Het), Axin2-/- (A-KO), Axin2-/-:Runx2+/- (A-KO:R-Het). Total = 16 samples
Project description:Runx2 and Axin2 regulate skeletal development. We recently determined that Axin2 and Runx2 molecularly interact in differentiating osteoblasts to regulate intramembranous bone formation, but the relationship between these factors in endochondral bone formation was unresolved. To address this, we examined the effects of Axin2 deficiency on the cleidocranial dysplasia (CCD) phenotype of Runx2+/- mice, focusing on skeletal defects attributed to improper endochondral bone formation. Axin2 deficiency unexpectedly exacerbated calvarial components of the CCD phenotype in the Runx2+/- mice; the endocranial layer of the frontal suture, which develops by endochondral bone formation, failed to mineralize in the Axin2-/-:Runx2+/-mice, resulting in a cartilaginous, fibrotic and larger fontanel than observed in Runx2+/- mice. Transcripts associated with cartilage development (e.g., Acan, miR140) were expressed at higher levels, whereas blood vessel morphogenesis transcripts (e.g., Slit2) were suppressed in Axin2-/-:Runx2+/-calvaria. Cartilage maturation was impaired, as primary chondrocytes from double mutant mice demonstrated delayed differentiation and produced less calcified matrix in vitro. The genetic dominance of Runx2 was also reflected during endochondral fracture repair, as both Runx2+/- and double mutant Axin2-/-:Runx2+/- mice had enlarged fracture calluses at early stages of healing. However, by the end stages of fracture healing, double mutant animals diverged from the Runx2+/- mice, showing smaller calluses and increased torsional strength indicative of more rapid end stage bone formation as seen in the Axin2-/- mice. Taken together, our data demonstrate a dominant role for Runx2 in chondrocyte maturation, but implicate Axin2 as an important modulator of the terminal stages of endochondral bone formation.
Project description:Runx2 and Axin2 regulate skeletal development. We recently determined that Axin2 and Runx2 molecularly interact in differentiating osteoblasts to regulate intramembranous bone formation, but the relationship between these factors in endochondral bone formation was unresolved. To address this, we examined the effects of Axin2 deficiency on the cleidocranial dysplasia (CCD) phenotype of Runx2+/- mice, focusing on skeletal defects attributed to improper endochondral bone formation. Axin2 deficiency unexpectedly exacerbated calvarial components of the CCD phenotype in the Runx2+/- mice; the endocranial layer of the frontal suture, which develops by endochondral bone formation, failed to mineralize in the Axin2-/-:Runx2+/-mice, resulting in a cartilaginous, fibrotic and larger fontanel than observed in Runx2+/- mice. Transcripts associated with cartilage development (e.g., Acan, miR140) were expressed at higher levels, whereas blood vessel morphogenesis transcripts (e.g., Slit2) were suppressed in Axin2-/-:Runx2+/-calvaria. Cartilage maturation was impaired, as primary chondrocytes from double mutant mice demonstrated delayed differentiation and produced less calcified matrix in vitro. The genetic dominance of Runx2 was also reflected during endochondral fracture repair, as both Runx2+/- and double mutant Axin2-/-:Runx2+/- mice had enlarged fracture calluses at early stages of healing. However, by the end stages of fracture healing, double mutant animals diverged from the Runx2+/- mice, showing smaller calluses and increased torsional strength indicative of more rapid end stage bone formation as seen in the Axin2-/- mice. Taken together, our data demonstrate a dominant role for Runx2 in chondrocyte maturation, but implicate Axin2 as an important modulator of the terminal stages of endochondral bone formation.
Project description:Summary: RNAseq analysis of Axin2+ and Axin2- endometrial epithelial cells shows that Axin2+ cells have a distinct gene expression profile compared to Axin2- cells. Methods: Four-week-old Axin2rtTA; tetOH2BJGFP mice (n=3) were ovariectomized. After 2 weeks of rest, H2BJGFP was induced in Axin2+ cells by a single dose of doxycycline administered intraperitoneally and uteri were collected 4 days post-doxycycline administration. Endometrial epithelial cells were isolated, digested into single cell suspension and Axin2+ (GFPhigh) and Axin2- (GFP-) cells were FACS sorted. The respective Axin2+ and Axin2- cells from each of the three mice used in this experiment were pooled together (Axin2- cells = C1, C2, C3; Axin2+ cells = M1, M2, M3, Arabic numeral represents the mouse number). Total RNA was isolated using RNeasy Micro kit (Qiagen) as per manufacturer instructions. RNA quality and concentration were determined using Nanodrop ND-1000 Spectrophotometer. RNAseq profiles were generated using Illumina NovaSeq platform. The reads were mapped to the mouse genome (Build version mm10) using the STAR aligner (v2.5.3a) and differential gene expression analysis was performed using edgeR (version 3.22.5) tool. Results: Differential gene expression analysis using edgeR identified 4458 genes that were differentially expressed by more than twofold in the Axin2high population compared with Axin2- population. Several of these differentially expressed genes include some of the well-known stem cell markers.
Project description:Wnt signaling is a crucial developmental pathway involved in early development as well as stem cell maintenance in adults and its misregulation leads to numerous diseases. Thus, understanding the regulation of this pathway becomes vitally important. Axin2 and Nkd1 are widely utilized negative feedback regulators in Wnt signaling where Axin2 functions to destabilize cytoplasmic β-catenin, and Nkd1 functions to inhibit the nuclear localization of β-catenin. Here, we set out to further understand how Axin2 and Nkd1 regulate Wnt signaling by creating axin2-/-, nkd1-/- single mutants and axin2-/-;nkd1-/- double mutant zebrafish using sgRNA/Cas9. All three Wnt regulator mutants were viable and had impaired heart looping, neuromast migration defects, and behavior abnormalities in common, but there were no signs of synergy in the axin2-/-;nkd1-/- double mutants. Further, Wnt target gene expression by qRT-PCR, and RNA-seq analysis and protein expression by mass spec demonstrated that the double axin2-/-;nkd1-/- mutant resembled the nkd1-/- phenotype demonstrating that Axin functions upstream of Nkd1 and that loss of Nkd1 is dominant over the loss of Axin2. In support of this, the data further demonstrates that Axin2 uniquely alters the properties of β-catenin-dependent transcription having novel readouts of Wnt activity compared to nkd1-/- or the axin2-/-;nkd1-/- double mutant. We also tested the sensitivity of the Wnt regulator mutants to exacerbated Wnt signaling, where the single mutants displayed characteristic heightened Wnt sensitivity, resulting in an eyeless phenotype. Surprisingly, this phenotype was rescued in the double mutant, where we speculate that cross-talk between Wnt/β-catenin and Wnt/Planar Cell Polarity pathways could lead to altered Wnt signaling in some scenarios. Collectively, the data emphasizes both the commonality and the complexity in the feedback regulation of Wnt signaling.
Project description:Progenitor cells of the first and second heart fields (FHF and SHF) depend on cardiac-specific transcription factors for their differentiation. In mouse mutant embryos, we define the hierarchy of signaling events that controls the expression of cardiac-specific transcription factors during commitment of SHF progenitors at E9.25. Wnt and Bmp act downstream of Notch/RBPJ at this developmental stage. Mutation of Axin2, the negative regulator of canonical Wnt signaling, enhances Wnt and Bmp signals and suffices to rescue the cardiac differentiation arrest caused by loss of RBPJ. By analysis of isolated cardiac progenitors, embryo cultures in the presence of pharmacological inhibitors, and Bmp triple mutants, we could classify the expression of heart-specific transcription factors of SHF progenitors according to their dependence on either Wnt or Bmp signals, Nkx2-5, Isl1, Baf60c and Gata4, SRF, Mef2c, respectively. Total RNA from whole embryonic hearts of control mice was compared to MesP1-cre:RBPJlox/lox (KO), MesP1-cre:RBPJlox/lox//Axin2-/- (DKO), MesP1-cre:RBPJlox/+//Axin2-/- (hetDKO) and MesP1-cre:RBPJlox/lox//Axin2+/- (DKOhet) mutant mouse embryos.