Pax1

LSJL upregulates Pax1 2.166 fold.

Overexpression of SOX9 in mouse embryonic stem cells directs the immediate chondrogenic commitment.

"Mouse embryonic stem (mES) cells are capable of undergoing chondrogenesis in vitro. Human SOX9 (hSOX9) cDNA was delivered into mES cells. The transcripts of collagen IIA (a juvenile form), aggrecan and Pax1 were expressed in mES-hSOX9 cells grown on feeder layers, suggesting the immediate effect of exogenous SOX9 on chondrogenesis. SOX9 overexpression did not affect the cell cycle distribution in undifferentiated mES cells. Upon differentiation, collagen IIB (an adult form) was detected in day 3 immature embryoid bodies. The overexpression of exogenous SOX9 significantly induced transcriptional activity driven by SOX9 binding site. Constitutive overexpression of exogenous SOX9 in undifferentiated mES cells might have dual potentials to induce both chondrogenic commitment and growth capacity in the undifferentiated status."

"Several transcription factors are expressed in mesenchymal cells during early chondrogenesis, such as high-mobility group (HMG) box protein SOX9, and the paired-box-gene Pax-1"<-the upregulation of Pax1 by LSJL indicates that it induces early chondrogenesis.

"The expression of collagen IIB, an isoform lacking a 69 amino acid cysteine-rich domain encoded by exon 2 is specifically localized in differentiating and adult chondrocytes, indicating the differentiation into functional chondrocytes"<-LSJL did not alter COL2B expression above threshold.

Embryonic stem cell-derived chondrogenic differentiation in vitro: activation by BMP-2 and BMP-4.

"Differentiation of mouse embryonic stem (ES) cells via embryoid bodies was established as a suitable model to study development in vitro.  Differentiation of ES cells in vitro into chondrocytes can be modulated by members of the transforming growth factor-beta family (TGF-beta(1), BMP-2 and -4).  Different stages of cartilage differentiation could be distinguished according to the expression pattern of the transcription factor scleraxis {LSJL upregulates scleraxis}, and the cartilage matrix protein collagen II. The number of Alcian-blue-stained areas decreased slightly after application of TGF-beta(1), whereas BMP-2 or -4 induced chondrogenic differentiation. The inducing effect of BMP-2 was found to be dependent on the time of application, consistent with its role to recruit precursor cells to the chondrogenic fate."

"Genes encoding transcription factors involved in mesenchymal differentiation, such as Pax-1 and Sox-9 as well as extracellular matrix proteins of cartilage tissue, such as collagen II and aggrecan were found to be expressed in EBs during culture"

"During early EB differentiation we found high levels of scleraxis expression in cells that did not produce collagen II and later scleraxis expressing cells were organized in nodules staining positive for Alcian blue, collagen II and COMP characteristic for developing chondrocytes"

Transcriptional control of chondrocyte fate and differentiation.

"The framework of the cartilage matrix is a collagen fiber network that is comprised primarily of type II collagen (encoded by the Col2a1{up in LSJL} gene) and secondarily of type IX collagen (Col9a1{up in LSJL}, Col9a2, and Col9a3{up in LSJL}) and type XI collagen (Col11a1{up in LSJL}, Col11a2). Collagen type X (Col10a1{up in LSJL}) is produced in abundance but exclusively by prehypertrophic and hypertrophic chondrocytes."

"[Pre-cartilage condensations] express extracellular matrix and cell adhesion molecules such as N-cadherin, N-CAM (Ncam1), tenascin C (Tnc){down in LSJL}, versican{up in LSJL}, and thrombospondin-4{up in LSJL}"

"Pax1 and Pax9 are transcriptional activators with a paired box DNA-binding domain, and Nkx3.1 and Nkx3.2 are transcriptional repressors related to the Drosophila bagpipe factor."

"Expression of Pax1 and Pax9 is induced by the signaling molecule Sonic hedgehog (Shh), and expression of Nkx3.2 (possibly Nkx3.1 as well) is induced by Pax1 and Pax9"

"Nkx3.2 and Sox9 are able to induce each other's expression in the presence of Shh, and this positive autoregulatory loop can be maintained by BMP signaling and results in robust chondrogenesis"

"The homeobox transcription factor Barx2{up in LSJL} is highly expressed in precartilaginous mesenchymal condensations of the limb bud, and remains expressed in developing joints and articular cartilage"

"Atf2 transcription factor contributes to stimulate columnar chondroblast proliferation "

"Runx2 is expressed in chondrogenic mesenchymal cells [but] is no longer expressed in chondroblasts. It is reactivated, and Runx3 is activated, when chondroblasts are about to become prehypertrophic, and Runx2, but not Runx3, remains expressed through chondrocyte hypertrophy and terminal differentiation"

"Dlx5 and Dlx6 promote chondrocyte maturation and may cooperate with Runx2 and Runx3 in this function."

"Dlx5 [may] bind to a recognition site in the Col10a1 promoter and to activate a Col10a1 promoter construct"

"A negative modulator of Runx2 function is the histone deacetylase Hdac4"

The concerted action of Meox homeobox genes is required upstream of genetic pathways essential for the formation, patterning and differentiation of somites.

"The induction of Pax1 and Pax9 gene expression by SHH is necessary for vertebral and rib formation"

"Meox1 mutant mice display defects restricted to sclerotomal derivatives, the vertebrae and ribs are fused"

"SHH regulates competence of cells to respond to BMP. In the absence of SHH, BMP signals result in lateral plate gene expression, but following prior exposure to SHH cells respond to BMP by inducing chondrogenesis in explant cultures"