Fig. 4

SnoRNA expression strategies ensure low family abundance variability. A Total family abundance tends to vary according to family size. Boxplots showing the total abundance of a family (in TPM) as a function of the number of expressed family members. B The average variability in abundance of individual members is greater than the variability of the family. Scatter plots showing the coefficient of variation of the total abundance of a family across human tissues as a function of the mean coefficient of variation of abundance of all members of the family. Only expressed family members are considered. The families were colored according to their numbers of expressed members. C For most human snoRNA families, members are intronic. As shown with pie charts, while few families (2 for box C/D families and 14 for box H/ACA families) have only intergenic members, most C/D families 64% (81/126) have only intronic members encoded in only coding genes or only noncoding genes. In contrast 55% (50/91) of H/ACA families have members encoded in different genomic context (most of these families with members both in coding and noncoding host genes, i.e. Mixed). The number of families with all their members being only in coding or noncoding genes is also highly increased if only expressed members are considered (compare Expressed vs All). Details are available in Supp Fig. S12, S13. D Different family member expression strategies for C/D and H/ACA families. Pie charts showing the proportion of families with all expressed members encoded in the same host gene or with some expressed members encoded in different host genes. Only families with at least two expressed members were considered. All panels of this figure show C/D families on the left and H/ACA families on the right