Sunday, May 9, 2010


 Osr1 is downregulated by LSJL.  In the gene ontology diagrams, downregulation of Osr1 is involved in the chondrocyte differentiation phase.

Odd-skipped related genes regulate differentiation of embryonic limb mesenchyme and bone marrow mesenchymal stromal cells.

"Osr1 and Osr2, 2 closely related genes encoding zinc finger transcription factors, [are] strongly expressed in irregular connective tissue (ICT) fibroblasts in the chicken embryo, suitable as a developmental marker. Both Osr1 and Osr2 regulate mesenchymal cell-type differentiation. Both Osr1 and Osr2 can promote the formation of ICT, a cell type of so far unknown molecular specification, while suppressing differentiation of other tissues such as cartilage and tendon from uncommitted progenitors. Conversely, knockdown of either Osr gene alone or in combination reverses this effect, thereby leading to decreased differentiation of ICT fibroblasts and increased chondrogenesis in vitro. This indicates that Osr genes play a pivotal role in ICT fibroblast differentiation. Undifferentiated mesenchymal cells reside in the adult body in the form of mesenchymal stem cells in the bone marrow cavity. Using bone marrow stromal cells (BMSCs) isolated from chicken fetal long bones, we show that Osr1 and Osr2 have an intrinsic role in BMSC differentiation similar to their role in early embryonic development, that is, the enforcement of CT fibroblast differentiation and the repression of other cell types as exemplified here by osteoblast differentiation."

"Osr1 and Osr2 expression was not observed in Pax3 positive cells."  Pax3 stimulates muscle tissue differentiation.

"in the forming joints, both genes showed co-expression [with Sox9] at the cartilage/joint interface" but later in development Sox9 was exclusive from Osr1 and Osr2.

Col3a1{up} and Col6a1{up} are also markers of irregular connective tissue.

"Knockdown of Osr1 or Osr2 alone or in combination led to an increase in cartilage differentiation in MM cultures"

"the repressor forms of Osr1 and Osr2 completely inhibited cartilage condensation in the MM cultures"

The downregulation of Osr1 could be a sign of mesenchymal stem cells differentiating into chondrocytes as a result of LSJL.

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