Data for: NFATc1 marks articular cartilage progenitors and negatively determines articular chondrocyte differentiation

The origin and differentiation mechanism of articular chondrocytes remain
poorly understood. Broadly, the difference in developmental mechanisms of
articular and growth-plate cartilage is still less elucidated. Here, we
identified that the nuclear factor of activated T-cells cytoplasmic 1
(NFATc1) is a crucial regulator of articular, but not growth-plate,
chondrocyte differentiation during development. At the early stage of
mouse knee development (embryonic day 13.5), NFATc1-expressing cells were
mainly located in the flanking region of the joint interzone. With
development, NFATc1-expressing cells generated almost all articular
chondrocytes, but not chondrocytes in limb growth-plate primordium.
NFATc1-expressing cells displayed prominent capacities for colony
formation and multipotent differentiation. Transcriptome analyses revealed
a set of characteristic genes in NFATc1-enriched articular cartilage
progenitors. Strikingly, the expression of NFATc1 was diminished with
articular chondrocyte differentiation and suppressing NFATc1 expression in
articular cartilage progenitors was sufficient to induce spontaneous
chondrogenesis while overexpressing NFATc1 suppresses chondrogenesis.
Mechanistically, NFATc1 negatively regulated the transcriptional activity
of the Col2a1 gene. Thus, our results reveal that NFATc1
characterizes articular, but not growth-plate, cartilage progenitors
during development and negatively determines articular chondrocyte
differentiation at least partly through regulating COL2A1 gene
transcription.

关节软骨细胞的起源与分化机制至今仍未得到充分阐明。总体而言，关节软骨与生长板软骨的发育机制差异同样鲜有研究得以阐明。本研究发现，活化T细胞核因子胞质1（NFATc1）是发育阶段关节软骨细胞分化的关键调控因子，而对生长板软骨细胞分化无此类调控作用。在小鼠膝关节发育早期（胚胎第13.5天），表达NFATc1的细胞主要定位于关节间区的侧翼区域。随着发育进程推进，表达NFATc1的细胞几乎可分化为所有关节软骨细胞，但无法分化为肢体生长板原基中的软骨细胞。表达NFATc1的细胞展现出显著的集落形成能力与多向分化潜能。转录组分析结果显示，在富集NFATc1的关节软骨祖细胞中存在一组特征性表达基因。值得注意的是，随着关节软骨细胞的分化，NFATc1的表达水平逐渐降低；在关节软骨祖细胞中抑制NFATc1的表达即可诱导自发软骨形成，而过表达NFATc1则会抑制软骨生成过程。从机制层面来看，NFATc1可负向调控Col2a1基因的转录活性。综上，本研究结果表明，NFATc1可作为发育阶段关节软骨（而非生长板软骨）祖细胞的特征标记，并至少通过调控COL2A1基因转录，负向调控关节软骨细胞的分化过程。