Incoherent Feedforward Regulation via Sox9 and ERK Underpins Mouse Tracheal Cartilage Development

Abstract

Tracheal cartilage provides architectural integrity to the respiratory airway, and defects in this structure during embryonic development cause severe congenital anomalies. Previous genetic studies have revealed genes that are critical for the development of tracheal cartilage. However, it is still unclear how crosstalk between these proteins regulates tracheal cartilage formation. Here we show a core regulatory network underlying murine tracheal chondrogenesis from embryonic day (E) 12.5 to E15.5, by combining volumetric imaging of fluorescence reporters, inhibitor assays, and mathematical modeling. We focused on SRY-box transcription factor 9 (Sox9) and extracellular signal-regulated kinase (ERK) in the tracheal mesenchyme, and observed a synchronous, inverted U-shaped temporal change in both Sox9 expression and ERK activity with a peak at E14.5, whereas the expression level of downstream cartilage matrix genes, such as collagen II alpha 1 (Col2a1) and aggrecan (Agc1), monotonically increased. Inhibitor assays revealed that the ERK signaling pathway functions as an inhibitory regulator of tracheal cartilage differentiation during this period. These results suggest that expression of the cartilage matrix genes is controlled by an incoherent feedforward loop via Sox9 and ERK, which is supported by a mathematical model. Furthermore, the modeling analysis suggests that a Sox9-ERK incoherent feedforward regulation augments the robustness against the variation of upstream factors. The present study provides a better understanding of the regulatory network underlying the tracheal development and will be helpful for efficient induction of tracheal organoids.

Wnt-Dependent Activation of ERK Mediates Repression of Chondrocyte Fate during Calvarial Development

“…One study showed that ERK signaling is required for initial SOX9 activation in primary chondrocytes and C3H10T1/2 cells in vitro [ 30 ] while another noted that ERK activation during late chondrogenic differentiation resulted in increased chondrogenesis in limb bud mesenchyme, but only in the presence of p38/MapK signaling [ 31 ]. Recent studies have identified a unique relationship between ERK signaling and tracheal chondrogenic differentiation, demonstrating the existence of an incoherent feed forward loop where chondrogenesis is activated by SOX9 and simultaneously repressed by ERK [ 32 ]. The role ERK signaling plays during calvarial osteoblast fate decisions is unclear.…”

ERK-mediated Curvature Feedback Regulates Branching Morphogenesis in Lung Epithelial Tissue

“…The genetic inactivation of either Mek1/2 or Erk1/2 specifically in the airway epithelium results in lung agenesis 19 , implying that ERK and its activation were essential for lung development 20 . Previously, immunofluorescence staining results suggested that the phosphorylation of ERK was most likely to occur in the distal tips of the lung epithelium, and may thus be involved in the budding process during lung development [21][22][23] .…”

Noise suppression in stochastic genetic circuits using PID controllers

“…However, in this work we consider the simplified case where incoherent regulation is fed back on to Y itself to give derivative action. Incoherent feedforward motifs are known to be abundant in E. coli and higher organisms [105][106][107][108]. One can speculate that at least some of these motifs are part of feedback circuits, however a rigorous bioinformatic analysis would have to be done to show this.…”