Cartilage subpopulation in PPB
The other clusters were developing in the direction toward chondrocytes.
Clusters 0, 1, 3, 7, 8, 10, and 11 (5 806 cells in total) exhibited high
expression of TWIST1 , ANK3 , HTRA1 , and BMP4 ,
which are markers of osteogenesis (Fig.3A, Supporting Information Figure
S3). Subsets of chondrocytes were distinguished based on further
markers. A mature minor subset (cluster 7, 617 cells) was defined by
chondrocyte markers that emerge in late differentiation, such asITM2A , MGP , and OGN . Cluster 10 (402 cells) was
characterized by DKK2 and TNMD , which was possibly also at
the terminal stage of their trajectory with the same status as cluster
7. Another major stem cell subset, clusters 1, 3, 8, and 11, expressed
decisive genes in early chondrogenesis, including SOX9 andSOX9 -coordinated factor-like PAX1 , PAX9 and they
maybe were a group of prechondrocytes. Notably, these cartilages were
more naïve in their differentiation compared with the muscle
subpopulation. Additionally, the characteristic cartilage structure was
not observed pathologically and the tumor was negative for
immunohistochemical staining of S100 protein. GO analysis of these
clusters validated our presumed results. These cells participated in
development of the skeletal system and functions such as maintenance and
rebuilding of the extracellular matrix17 (Fig.3B).