Background: Although runt-related transcription factor 2 (RUNX2) has been considered a determinant of cleidocranial dysplasia (CCD), some CCD patients were free of RUNX2 mutations. CCAAT/enhancer-binding protein beta (Cebpb) is a key factor of Runx2 expression and our previous study has reported two CCD signs including hyperdontia and elongated coronoid process of the mandible in Cebpb deficient mice. Following that, this work aimed to conduct a case-control study of thoracic, zygomatic and masticatory muscular morphology to propose an association between musculoskeletal phenotypes and deficiency of Cebpb, using a sample of Cebpb, Cebpb and Cebpb adult mice. Somatic skeletons and skulls of mice were inspected with soft x-rays and micro-computed tomography (μCT), respectively. Zygomatic inclination was assessed using methods of coordinate geometry and trigonometric function on anatomic landmarks identified with μCT. Masseter and temporal muscles were collected and weighed. Expression of Cebpb was examined with a reverse transcriptase polymerase chain reaction (RT-PCR) technique. Results: Cebpb mice displayed hypoplastic clavicles, a narrow thoracic cage, and a downward tilted zygomatic arch (p < 0.001). Although Cebpb mice did not show the phenotypes above (p = 0.357), a larger mass percentage of temporal muscles over masseter muscles was seen in Cebpb littermates (p = 0.012). The mRNA expression of Cebpb was detected in the clavicle, the zygoma, the temporal muscle and the masseter muscle, respectively. Conclusions: Prospective signs of CCD were identified in mice with Cebpb deficiency. These could provide an additional aetiological factor of CCD. Succeeding investigation into interactions among Cebpb, Runx2 and musculoskeletal development is indicated.
Bibliographical noteFunding Information:
The publication was supported with a Japanese Society for the Promotion of Science (JSPS) Postdoctoral Fellowship (P09741) awarded by the JSPS and the Australian Academy of Science. The authors would like to show appreciation to those staff and students who helped in this project. In addition, the paper is indebted to Professor Jen-Shiang Kenny Yu, Dr Yunlong Kang, Dr Kazumasa Nakao, Dr Noriaki Koyama, Dr Hiroko Tsukamoto and Dr Tomoko Goto for helpful discussions. Special thanks to Dr Mei-lan Chen for her assistance in preparation of electronic artwork.
- Cleidocranial dysplasia
- Temporal muscle
- Thoracic cage
- Zygomatic arch