SNORD expression levels during zebrafish development. (A) Relative expression levels of all SNORDs identified in this study that guides methylation in rRNA. (B) Cumulated expression of SNORDs guiding invariable 2′-O-Me sites (Invariable) and sites that exhibit increased methylation during development (Me up). This group comprised SSU-C346, -U354, -G436, LSU-C3916, -G3923, -A4560, and 5.8S-U14 and the cognate SNORDs, SNORD-200, -90, -100, -202, -111, -119, and -71. Asterisks indicate significant differences between the two groups of methylation sites within a given developmental stage. (C) Schematic of the poorly annotated FP101887 host gene with indication of 11 exons based on comparison to the longest annotated transcript that appear to encode a lncRNA. The introns host 10 SNORDs of which nine are related. Two SNORDs are given double names (see text for explanation). (D) Alignment of the SNORDs encoded by the FP101887 gene. Conserved SNORD elements are in bold and the antisense elements are underlined. Nucleotides deviating from the most abundant nucleotide at any given position in the alignment are labeled in red to highlight the relatedness of the SNORDs. (E) Expression data extracted from RiboMeth-seq analysis (low coverage RNA-seq).
