(e) Peak to peak distance in auto-correlation plots of de-trended Venus::HES5 spatial profile in MN and IN domains; this is a measure of spatial period in Venus::HES5 profile along dorsal-ventral axis of spinal cord; grey data points represent mean peak to peak distance of at least 3 slices with left and right ventricle analysed separately in 6 experiments; black dots show median per experiment and line shows overall median; 2-tailed Mann-Whitney test p-values ****p<0.00001. 