Fig. 4

The expression level of KZFP genes with different gene age grades or SDR grades in mammals. Samples in 7 mammals, including early embryonic development, three directions of ESC differentiation, organs from early organogenesis to adulthood and adult tissues or organs were used in the analysis. Heatmap shows the proportion of three expression level grades of KZFPs with each gene age (a) or SDR grade (b) grade. The number in the box on the left represents the total number of samples. The number of KZFPs and PCGs in each category is in Additional file 10. The category with gene number 0 is displayed in gray. The over/under representation strength shows KZFP genes relative to PCGs with different expression levels in each gene age grade or SDR grade in each sample. Over representation strength: +, P ≥ 0.05; ++, P < 0.05; +++, P < 10^− 10. Under representation strength: −, P ≥ 0.05; −−, P < 0.05; −−−, P < 10^− 10. Gene age grade: CO − Op, Cellular organisms−Opisthokonta; Eu-Ve, Eumetazoa−Vertebrata; Ma, Mammalia. Expression level: L, low-abundant level; M, medium-abundant level; H, high-abundant level