BCL11B expression in intramembranous osteogenesis during murine craniofacial suture development

https://doi.org/10.1016/j.gep.2014.12.001Get rights and content

Highlights

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    BCL11B expression is integral to murine intramembranous craniofacial bone development.

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    BCL11B expression characterizes suture mesenchyme.

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    BCL11B is excluded from more differentiated osteoblasts.

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    BCL11B is absent from cartilage and osteoblasts in cranial endochondral ossification.

Abstract

Sutures, where neighboring craniofacial bones are separated by undifferentiated mesenchyme, are major growth sites during craniofacial development. Pathologic fusion of bones within sutures occurs in a wide variety of craniosynostosis conditions and can result in dysmorphic craniofacial growth and secondary neurologic deficits. Our knowledge of the genes involved in suture formation is poor. Here we describe the novel expression pattern of the BCL11B transcription factor protein during murine embryonic craniofacial bone formation. We examined BCL11B protein expression at E14.5, E16.5, and E18.5 in 14 major craniofacial sutures of C57BL/6J mice. We found BCL11B expression to be associated with all intramembranous craniofacial bones examined. The most striking aspects of BCL11B expression were its high levels in suture mesenchyme and increasingly complementary expression with RUNX2 in differentiating osteoblasts during development. BCL11B was also expressed in mesenchyme at the non-sutural edges of intramembranous bones. No expression was seen in osteoblasts involved in endochondral ossification of the cartilaginous cranial base. BCL11B is expressed to potentially regulate the transition of mesenchymal differentiation and suture formation within craniofacial intramembranous bone.

Section snippets

Results

It is known that Bcl11b is diffusely expressed in the distal mandibular and facial mesenchyme during early embryogenesis, including murine embryonic day (E) 12.5 (Chan et al, 2007, Leid et al, 2004). We used an established antibody to BCL11B (Arlotta et al, 2005, Kyrylkova et al, 2012, Senawong et al, 2003, Topark-Ngarm et al, 2006) to determine the relationship between BCL11B expression and craniofacial bone formation during embryonic mouse development, starting at E14.5, when most

Discussion

While the existence of Bcl11b expression in the early facial mesenchyme was previously known (Chan et al, 2007, Leid et al, 2004), the recent demonstrations of midfacial hypoplasia in Bcl11b−/− mice suggest a later role for this transcription factor in craniofacial development (Golonzhka et al, 2009b, Katsuragi et al, 2013). Indeed, we have found BCL11B expression to be intimately associated with suture formation and osteoblast differentiation during intramembranous craniofacial bone

Animals

Animal experiments were in compliance with animal welfare guidelines mandated by the Institutional Animal Care and Use Committee of the Icahn School of Medicine at Mount Sinai. Timed matings of wild-type C57BL/6J mice (Stock # 000664, The Jackson Laboratory) were made to obtain the appropriate embryonic ages for histology and immunohistochemistry.

Histology and immunohistochemistry

Heads were fixed in 4% PFA in 1× PBS overnight at 4 °C, washed in 1× PBS, and embedded in paraffin. Three sections per slide were cut at 5 µm. Every

Acknowledgements

The work was supported by grants, NIH/NIDCR 1 R01 DE022988 and NIH/NIDCR 1 U01 DE024448.

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