The overall objective in this application is to examine the fundamental mechanisms underlying coronal suture development. We will test the central hypothesis that tissue interaction between tectum transversum (TTR) and coronal sutures interact during development, and a rigorous regulation of Pdgfra activity is required for their interaction. Pdgfra plays a crucial role in craniofacial development, and elevated PDGFRA expression and activity is implicated in human craniosynostosis. We will examine the following specific aims: 1. To examine interaction between TTR and suture cells during embryonic development. In this aim we will test the hypothesis that TTR and suture cells interact during embryogenesis.
In aim 1 a, we will examine the coronal suture development with removal of TTR.
In aim 1 b, we will assess the requirement of coronal sutures on TTR development. We will use genetic tools to ablate coronal sutures specifically and assess TTR development in mouse models. 2. To examine the mechanisms underlying Pdgfra regulation on TTR development. The regulatory mechanisms underlying TTR development has not been illustrated. Alteration of Pdgfra activity causes distinct TTR phenotype, indicating Pdgfra is a critical player in TTR formation. By transcriptome profiling we identified Wnt9a and Sox9 as transcriptional targets of Pdgfra. In this aim we will test the hypothesis that Pdgfra regulates chondrocyte progenitors formation by regulating Sox9 expression via Wnt9a/beta-catenin signaling.
In aim 2 a, we will characterize the role of Pdgfra in TTR development, by analyzing the TTR phenotype in both Pdgfra loss-of-function (LOF) and gain-of-function (GOF) models.
In aim 2 b, we will analyze the role of Pdgfra in controlling chondrocyte progenitor formation.
In aim 2 c, we will examine Wnt9a/beta-catenin pathway as a potential mediator of Pdgfra in controlling Sox9 expression and chondrocyte progenitor formation. 3. To examine the role of Pdgfra in coronal sutural cells development and maintenance. It has been shown that suture contains abundant mesenchymal stem cells (MSCs). Pdgfra is a recognized MSCs marker. Our data show that Pdgfra is expressed in the developing suture. Constitutive activation of Pdgfra leads to abnormal differentiation in the developing sutures.
In aim 3 a, we will trace the suture progenitor cells in both Pdgfra LOF and GOF models by manipulating Pdgfra activity in a tissue-specific manner.
In aim 3 b, we will examine the role for Pdgfra in adult suture MSCs maintenance and their homeostasis using calvarial injury model. By completion of the proposed study, we expect to answer whether tissue interaction between TTR and coronal suture is essential for normal suture development, and what is the specific role for Pdgfra in normal suture development and craniosynostosis formation.
Craniosynostosis is one of the most common birth defects worldwide. The major goal of this proposal is to identify tissue interaction between chondrocytes and suture cells, and to examine role of Pdgfra in their development. Results from proposed studies will shed light on discovery of novel therapeutic targets for patients with craniosynostosis.