Members of the transforming growth factor β (TGFβ) family, such as activins, growth differentiation factors (GDFs), bone morphogenetic proteins (BMPs), and TGFβs, have been widely implicated to play critical roles during skeletal, craniofacial, and dental tissue development . GDF11, also known as BMP11, and myostatin (MSTN) are closely-related TGFβ family members that share 89% amino acid sequence identity in their mature domain . Despite sharing high sequence similarity, GDF11 and MSTN exert distinct endogenous functions.
Because GDF11 and MSTN have been suggested to play significant roles during craniofacial and dental tissue development, targeting these molecules may have the potential to become an effective therapeutic strategy for tissue regeneration; however, their exact functions in craniofacial and tooth development require further investigation. Recently, we reported that GDF11 and MSTN play opposite roles during vertebral and limb bone development . The goal of this study was to investigate the roles of GDF11 and MSTN in cranial bone and tooth formation, and whether GDF11 and MSTN also play differential functions in these tissues. Because micro-computed tomography (micro-CT) imaging is a relatively inexpensive and simple method that provides high throughput analysis with high resolution, making it ideal for newborn mice phenotyping especially in hard tissues such as bone and tooth, here, we used micro-CT analysis to evaluate cranial bones and lower incisors of mice deficient for
All animal studies were approved by the Institutional Animal Care and Use Committees at Seoul National University.
Micro-CT analysis was performed using Skyscan 1,172 and 1,272 (Bruker-MicroCT) following the manufacturers’ guidelines (provided by Bruker). Skyscan 1,272 was used to generate representative images of calvarial bones, which were taken with a pixel size of 8 μm at 60 kV and 166 μA through 0.25 mm aluminum filter. Skyscan 1,172 was used to generate representative images of lower incisors, which were taken with a pixel size of 4 μm at 50 kV and 200 μA through no filter. Morphometric analyses of cranial bone and lower incisors were performed on samples scanned with Skyscan 1,272 with a pixel size of 8 μm at 60 kV and 166 μA through 0.25 mm aluminum filter. Region of interests for cranial bones and lower incisors were extracted and analyzed using CTAn (v220.127.116.11; Bruker-MicroCT, Konitich, Belgium), a manufacturer-provided software. Lower incisor length was measured using the Dataviewer (v18.104.22.168; Bruker-MicroCT) software. Images were reconstructed and displayed using manufacturer-provided software NRecon (v22.214.171.124; Bruker-MicroCT), CTvox (v3.3.0; Bruker-MicroCT), and CTvol (v126.96.36.199; Bruker-MicroCT).
All values are presented as mean±standard error of the mean (SEM) from at least three independent experiments unless otherwise stated. One-way ANOVA with Tukey’s
GDF11 and MSTN, which share high amino acid sequence identity, play critical, but distinct roles during embryonic development. While MSTN is a potent inhibitor of skeletal muscle growth , GDF11 regulates axial skeletal patterning, organ development, and palatal formation . We previously showed that GDF11, as opposed to MSTN, promotes osteogenesis of the vertebrae and limbs that are developed through endochondral ossification . Here, we focused on the evaluation of membranous ossification of cranial bones in wild-type,
Although GDF11 and MSTN play divergent roles, the existence of some functional redundancy in regulating axial skeletal patterning and cranial development has been reported, as demonstrated by more severe homeotic transformations of
Whether the divergent functions of GDF11 and MSTN simply reflect their distinct expression patterns or reflect differences in their signaling mechanisms remains to be clarified. Both the mature GDF11 and MSTN initially bind to activin type 2 receptors (ACVR2A or ACVR2B) and recruit type 1 receptors (ALK4 or ALK5) to generate downstream signal transduction through SMAD2/3 phosphorylation . More recently, studies have reported that GDF11 can potently activate BMP signaling, phosphorylating SMAD1/5/9 in endothelial cells and calvarial osteoblasts [4,24-26]. Because BMP signaling in differentiated odontoblasts is critical for dentin production in teeth , and
Understanding the pathogenesis of craniofacial abnormalities and dysmorphic tooth formation is essential for the improvement of dental treatment options for these defects. Our results demonstrate that GDF11, unlike MSTN, is an endogenous promoter of cranial bone formation and tooth development. However, due to the perinatal lethality of
No potential conflict of interest relevant to this article was reported.