PT  - JOURNAL ARTICLE
AU  - Johanna F. B. Pagano
AU  - Mauro D. Locati
AU  - Wim A. Ensink
AU  - Marina van Olst
AU  - Selina van Leeuwen
AU  - Wim C. de Leeuw
AU  - Ulrike Nehrdich
AU  - Herman P. Spaink
AU  - Han Rauwerda
AU  - Martijs J. Jonker
AU  - Rob J. Dekker
AU  - Timo M. Breit
TI  - Maternal- and Somatic-type snoRNA Expression and Processing in Zebrafish Development
AID  - 10.1101/858936
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 858936
4099  - http://biorxiv.org/content/early/2019/11/28/858936.1.short
4100  - http://biorxiv.org/content/early/2019/11/28/858936.1.full
AB  - Small nucleolar RNAs (snoRNAs) are non-coding RNAs that play an important role in the complex maturation process of ribosomal RNAs (rRNAs). SnoRNAs are categorized in classes, with each class member having several variants present in a genome. Similar to our finding of specific rRNA expression types in zebrafish embryogenesis, we discovered preferential maternal- and somatic-expression for snoRNAs. Most snoRNAs and their variants have higher expression levels in somatic tissues than in eggs, yet we identified three snoRNAs; U3, U8 and snoZ30 of which specific variants show maternal- or somatic-type expression. For U3 and U8 we also found small-derived snoRNAs that lack their 5’ rRNA recognition part and are essentially Domain II hairpin structures (U-DII). These U-DII snoRNAs from variants showed similar preferential expression, in which maternal-type variants are prominently expressed in eggs and subsequently replaced by a somatic-type variants during embryogenesis. This differential expression is related to the organization in tandem repeats (maternal type) or solitary (somatic-type) genes of the involved U snoRNA loci. The collective data showed convincingly that the preferential expression of snoRNAs is achieved by transcription regulation, as well as through RNA processing. Finally, we observed small-RNAs derived from internal transcribed spacers (ITSs) of a U3 snoRNA loci that via complementarity binding, may be involved in the biosynthesis of U3-DII snoRNAs. Altogether, the here described maternal- and somatic-type snoRNAs are the latest addition to the developing story about the dual ribosome system in zebrafish development.