Journal: bioRxiv

Article Title: Quantitative study of the somitogenetic wavefront in zebrafish

doi: 10.1101/419705

Figure Lengend Snippet: (a) A Clock and Wavefront model: antagonistic gradient of Fgf8 (originating from the posterior PSM, green) and RA (originating from the somites, violet) define a wavefront which interacts with a particular phase of the segmentation clock (in the PSM, red) to generate somites at periodic times and positions. (b) Kymograph of somitogenesis from 7 to 20 somites. The tail elongates at a constant rate V tail while the PSM shrinks at a roughly constant rate V PSM resulting in a somite wavefront propagating at a rate V front = V tail -V PSM .

Article Snippet: RT-qPCR was performed using the aforementioned cDNAs with TaqMan Universal PCR Master Mix and TaqMan Gene Expression Assay: Dr03119263_m1(rpl13a) and Dr03105657_m1(fgf8) (Applied Biosystems).

Techniques:

Journal: bioRxiv

Article Title: Quantitative study of the somitogenetic wavefront in zebrafish

doi: 10.1101/419705

Figure Lengend Snippet: Molecular models of the determination wavefront. (a) The Goldbeter, Gonze and Pourquié (G 2 P) model assumes that RA directly affects the translation of Fgf8 mRNA into protein, while Fgf8 represses RA via the activation of its degradation enzyme Cyp26. (b) The modified version of the G 2 P model (mG 2 P) proposed here takes into account the observed positive feedbacks of RA on Fgf8 and of Fgf8 on RaldH and the mutual inhibition of RA on MapK (via the RA-mediated activation of Mkp3) and of MapK on RA (via the MapK-controlled activation of Cyp26). (c) Both models predict a bistability of MapK activity for a certain positional range (in grey).

Article Snippet: RT-qPCR was performed using the aforementioned cDNAs with TaqMan Universal PCR Master Mix and TaqMan Gene Expression Assay: Dr03119263_m1(rpl13a) and Dr03105657_m1(fgf8) (Applied Biosystems).

Techniques: Activation Assay, Modification, Inhibition, Activity Assay

Journal: bioRxiv

Article Title: Quantitative study of the somitogenetic wavefront in zebrafish

doi: 10.1101/419705

Figure Lengend Snippet: Time of appearance of somites (t=0 at 7 somites stage). Notice the linearity of the plot, i.e. the regularity of the period of somitogenesis, in all the conditions studied here: WT (n=8), DEAB (an inhibitor of RaldH; with (n=14) or without (n=12) external RA), morpholinos against Fgf8 (MO-Fgf8; n=16), BCI (an inhibitor of Mkp3; n=16) or activation of exogenous Fgf8 (n=17).

Article Snippet: RT-qPCR was performed using the aforementioned cDNAs with TaqMan Universal PCR Master Mix and TaqMan Gene Expression Assay: Dr03119263_m1(rpl13a) and Dr03105657_m1(fgf8) (Applied Biosystems).

Techniques: Activation Assay

Journal: bioRxiv

Article Title: Quantitative study of the somitogenetic wavefront in zebrafish

doi: 10.1101/419705

Figure Lengend Snippet: (a) Staining of phosphorylated MapK by antibodies against this active form in WT embryos at 10 and 15 somites. Notice the smaller domain of activity at 15s as compared to 10s. (b) The data in was quantified by measuring the fluorescence intensity in a single embryo along the antero-posterior axis and averaged over n=17 (10s) and n=21 (15s) embryos. The averaged data is compared to simulations of the mG 2 P model with the parameters of assuming an exponential decrease (see ) between 7s and 10s (or 15s) of the mRNA Fgf8. The x and y-scales were chosen to fit the data at 10s. The simulation results are in qualitative agreement with the data, even though the latter might not be a perfect reflection of the MapK activity level (which depends on the efficiencies of staining and washing).

Article Snippet: RT-qPCR was performed using the aforementioned cDNAs with TaqMan Universal PCR Master Mix and TaqMan Gene Expression Assay: Dr03119263_m1(rpl13a) and Dr03105657_m1(fgf8) (Applied Biosystems).

Techniques: Staining, Activity Assay, Fluorescence

Journal: bioRxiv

Article Title: Quantitative study of the somitogenetic wavefront in zebrafish

doi: 10.1101/419705

Figure Lengend Snippet: (a) Variation with time of Fgf8 concentration versus somite stage and fit to an exponential decay past 5 somites stage. (b) PSM shortening from 7 somites stage (dots and error bars on mean; n=8) and results (continuous line) of a simulation of the mG 2 P model (with the displayed parameters and assuming an exponential decay of Fgf8 with the timescale measured in (a)). Details in Supp.Mat.

Article Snippet: RT-qPCR was performed using the aforementioned cDNAs with TaqMan Universal PCR Master Mix and TaqMan Gene Expression Assay: Dr03119263_m1(rpl13a) and Dr03105657_m1(fgf8) (Applied Biosystems).

Techniques: Concentration Assay

Journal: bioRxiv

Article Title: Quantitative study of the somitogenetic wavefront in zebrafish

doi: 10.1101/419705

Figure Lengend Snippet: Rates of PSM shrinkage (V PSM ), tail growth (V tail ) and wavefront velocity (V front ) in embryos growing (a) without or with morpholinos against Fgf8 (MO-Fgf8; dots and error bars on mean; n=16) injected at one-cell stage or (b) in which an exogenous source of Fgf8 was turned on (n=17). While V PSM is unaffected by MO-Fgf8 and slightly decreases upon over-expression of Fgf8 (in the strong phenotype 2 embryos), V tail decreases in both conditions, resulting in an overall decrease of V front . Continuous lines: simulations of the mG 2 P model with a 60% decrease in Fgf8 mRNA (due to interference with MO-Fgf8; γ=0.8 instead of γ=2 in model, see Supp.Mat.) qualitatively reproduce the data (continuous line in (a)). Similarly simulations with an increasing Fgf8 mRNA of about 2% of the measured increase (see Fig.S7) seem to reproduce the data observed in the strong phenotype 2 case (see Supp.Mat. Fig.S5).

Article Snippet: RT-qPCR was performed using the aforementioned cDNAs with TaqMan Universal PCR Master Mix and TaqMan Gene Expression Assay: Dr03119263_m1(rpl13a) and Dr03105657_m1(fgf8) (Applied Biosystems).

Techniques: Injection, Over Expression

Journal: bioRxiv

Article Title: Quantitative study of the somitogenetic wavefront in zebrafish

doi: 10.1101/419705

Figure Lengend Snippet: (a,c) MapK activity at steady-state from a simulation of mG 2 P model with the parameters shown in the figures and linear gradients of RaldH (parameter α) and Fgf8 mRNA (parameter γ). Notice the existence of a bistability window (between distances: −40 and −32 in (c)). (b,d) Variation with time of the distance from the tail end (at 0) of the rightmost bistability boundary (red vertical line in (a,c)): assuming linear decrease with time of Fgf8 mRNA (red curve; t ∼ 1 - mF0(t)/mF(0)) or exponential decrease with time of Fgf8 mRNA (blue curve, mF0(t) = mF0(0) e -t ). (e,f) Results of simulations with linear gradients of Cyp26 (parameter β) and Fgf8 mRNA (parameter γ). Notice that the MapK activity levels off at the tail end though a bistability window is still present. (g,h) Results of simulations with a linear gradient of Fgf8 mRNA (parameter γ) only. Notice the increasing MapK activity level and the increased PSM shrinkage rate at the tail end (even assuming an exponential decay with time of FgF8 mRNA).

Article Snippet: RT-qPCR was performed using the aforementioned cDNAs with TaqMan Universal PCR Master Mix and TaqMan Gene Expression Assay: Dr03119263_m1(rpl13a) and Dr03105657_m1(fgf8) (Applied Biosystems).

Techniques: Activity Assay