Since the synthetic lethal interactions are in general considered to reveal the functional redundancy between pathways [1], [7] [8], the pathways we pursued in this paper followed the first definition.
As to the crosstalk of GO [ 35] functional relationships between these pathways, we identified the accumulative hypergeometric significant GO biological processes in every pathway.
Thus, to show the relationships between the different pathways, we constructed a heatmap of the proportion of shared input genes between the significant pathways.
However, when looking at the general distribution of iHS values between the two parts of the pathway, we can observe that genes in the downstream part have higher values in all of the populations, even though, this differences reach significance only in two continental groups (Sub-Saharan Africans and Europeans).
To further assess the mechanism of crosstalk between the two pathways, we assessed phosphorylation of serine 9 of Gsk3β and serine 473 of Akt.
To test functional interaction between the 2 pathways, we tested whether POm spiking probability changed when the cortical driver pathway was co-stimulated for a range of time intervals relative to whisker stimulation.
To corroborate possible interaction between the two pathways we performed in silico analysis to identify putative TCF-binding elements (TBE) in myostatin promoter, as have been identified in the promoters of Wnt target genes [34].
To distinguish between the two alternative pathways, we evaluated the splice sites, the proto-splice sites and the relative location of the new introns in more detail: (1) We determined scores for reference splice sites and proto-splice sites excluding the central AG/GY motif.
To validate the correlation between clustered pathways, we use the Matlab corrcoeff function.
In order to analyze the crosstalk between the three signaling pathways we experimentally monitored the activity of selected signaling molecules as a function of different activity levels of the three receptors.
