Figure 5. Gene expression can be used to predict organ situs, but is dependent on several factors.

Regression analysis indicates that gene expression data can be used to predict organ situs, but only if the correct analysis is chosen based on timing and animal model. For all panels, total laterality problems are graphed along the X axis. For all graphs in the left column, the Y axis represents all non-left nodal expression (the sum of right, bilateral and absent gene expression). For all graphs in the middle column, the Y axis represents incorrect nodal expression (the sum of right and bilateral expression). For all graphs in the right column, the Y axis represents the predicted organ reversal rate derived from reported localization of Nodal. Yellow panels indicate the best fit regressions for each pathway (CILIA and EARLY) and each animal model. Panels A–C show regressions of all data using the three possible comparisons. Di–iii) The best regression for CILIA treatments is achieved by comparing all non-left nodal expression and total laterality problems. Ei–iii) The best regression for EARLY treatments is achieved by comparing predicted organ reversal rate and total laterality problems, although this relationship did not reach statistical significance. Fi–iii) Data from Xenopus fit two models equally well: regressions comparing all non-left nodal expression and total laterality problems and predicted organ reversal rate and total laterality problems. Gi–iii). Data from fish fit best to the regression between all non-left nodal expression and total laterality problems, but this relationship was not statistically significant. Hi–iii) Unexpectedly, data collected in mouse do not fit any of the regressions well, suggesting poor associations between asymmetric gene expression and organ laterality in this animal model. The best fit was observed between all non-left nodal expression and total laterality problems.