title: Prx1 and 3.2kb Col1a1 promoters target distinct bone cell populations in transgenic mice.
abstract: Bones consist of a number of cell types including osteoblasts and their precursor cells at various stages of differentiation. To analyze cellular organization within the bone, we generated Col1a1CreER-DsRed transgenic mice that express, in osteoblasts, CreER and DsRed under the control of a mouse 3.2kb Col1a1 promoter. We further crossed Col1a1CreER-DsRed mice with Prx1CreER-GFP mice that express CreER and GFP in osteochondro progenitor cells under the control of a 2.4kb Prx1 promoter. Since the 3.2kb Col1a1 promoter becomes active in osteoblasts at early stages of differentiation, and Prx1CreER-GFP-expressing periosteal cells show endogenous Col1a1 expression, we expected to find a cell population in which both the 2.4kb Prx1 promoter and the 3.2kb Col1a1 promoter are active. However, our histological and flow cytometric analyses demonstrated that these transgenes are expressed in distinct cell populations. In the periosteum of long bones, Col1a1CreER-DsRed is expressed in the innermost layer directly lining the bone surface, while Prx1CreER-GFP-expressing cells are localized immediately outside of the Col1a1CreER-DsRed-expressing osteoblasts. In the calvaria, Prx1CreER-GFP-expressing cells are also localized in the cranial suture mesenchyme. Our experiments further showed that Col1a1CreER-DsRed-expressing cells lack chondrogenic potential, while the Prx1CreER-GFP-expressing cells show both chondrogenic and osteogenic potential. Our results indicate that Col1a1CreER-DsRed-expressing cells are committed osteoblasts, while Prx1CreER-GFP-expressing cells are osteochondro progenitor cells. The Prx1CreER-GFP and Col1a1CreER-DsRed transgenes will offer novel approaches for analyzing lineage commitment and early stages of osteoblast differentiation under physiologic and pathologic conditions.
authors: Department of Orthopaedics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
authors: Zhufeng
authors: Z
authors: Ouyang
authors: Department of Orthopaedics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
authors: Zhijun
authors: Z
authors: Chen
authors: Department of Medicine, Cardiovascular Institute, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
authors: Masakazu
authors: M
authors: Ishikawa
authors: Department of Orthopaedics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
authors: Xiuzhen
authors: X
authors: Yue
authors: Department of Orthopaedics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
authors: Aya
authors: A
authors: Kawanami
authors: Division of General Medical Sciences, Oncology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
authors: Patrick
authors: P
authors: Leahy
authors: Department of Orthopaedics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Division of General Medical Sciences, National Center for Regenerative Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
authors: Edward M
authors: EM
authors: Greenfield
authors: Department of Orthopaedics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Division of General Medical Sciences, National Center for Regenerative Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Department of Genetics and Genomic Sciences, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA. Electronic address: shun@case.edu.
authors: Shunichi
authors: S
authors: Murakami
keywords: Col1a1; Cranial suture mesenchyme; Osteoblasts; Periosteum; Prx1