Functional canonical RNAi in mice expressing a truncated Dicer isoform and long dsRNA

• Published in: EMBO reports Vol. 25; no. 7; pp. 2896 - 2913
• Main Authors: Buccheri, Valeria, Pasulka, Josef, Malik, Radek, Loubalova, Zuzana, Taborska, Eliska, Horvat, Filip, Roos Kulmann, Marcos Iuri, Jenickova, Irena, Prochazka, Jan, Sedlacek, Radislav, Svoboda, Petr
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11-07-2024
• Subjects: Animals; Biomedical and Life Sciences; DEAD-box RNA Helicases - genetics; DEAD-box RNA Helicases - metabolism; EMBO36; Female; Life Sciences; Mice; MicroRNAs - genetics; MicroRNAs - metabolism; Protein Isoforms - genetics; Protein Isoforms - metabolism; Ribonuclease III - genetics; Ribonuclease III - metabolism; RNA Interference; RNA, Double-Stranded - genetics; RNA, Double-Stranded - metabolism; RNA, Small Interfering - genetics; RNA, Small Interfering - metabolism; dsRNA; Mirtron; siRNA; Dicer; PKR
• ISSN: 1469-3178; 1469-3178
• DOI: 10.1038/s44319-024-00148-z

Canonical RNA interference (RNAi) is sequence-specific mRNA degradation guided by small interfering RNAs (siRNAs) made by RNase III Dicer from long double-stranded RNA (dsRNA). RNAi roles include gene regulation, antiviral immunity or defense against transposable elements. In mammals, RNAi is constrained by Dicer’s adaptation to produce another small RNA class—microRNAs. However, a truncated Dicer isoform (ΔHEL1) supporting RNAi exists in mouse oocytes. A homozygous mutation to express only the truncated ΔHEL1 variant causes dysregulation of microRNAs and perinatal lethality in mice. Here, we report the phenotype and canonical RNAi activity in
Dicer
ΔHEL1/wt
mice, which are viable, show minimal miRNome changes, but their endogenous siRNA levels are an order of magnitude higher. We show that siRNA production in vivo is limited by available dsRNA, but not by Protein kinase R, a dsRNA sensor of innate immunity. dsRNA expression from a transgene yields sufficient siRNA levels to induce efficient RNAi in heart and muscle.
Dicer
ΔHEL1/wt
mice with enhanced canonical RNAi offer a platform for examining potential and limits of mammalian RNAi in vivo.
Synopsis
Modification of the Dicer gene in mice increases siRNA production in somatic organs, but dsRNA abundancy must be strongly increased for achieving efficient RNAi in vivo. Mice with enhanced RNAi will help to evaluate antiviral potential of mammalian RNAi in vivo.
Mice tolerate the modification of one allele of Dicer to the highly active ΔHEL1 variant.
Dicer
ΔHEL1/wt
mice produce higher levels of mirtrons but affect other miRNAs minimally when a full-length Dicer variant is present.
Dicer
ΔHEL1/wt
mice show an order of magnitude higher siRNA production from long dsRNA but efficient RNAi requires siRNA levels comparable to those of highly abundant miRNAs.
Modification of the Dicer gene in mice increases siRNA production in somatic organs, but dsRNA abundancy must be strongly increased for achieving efficient RNAi in vivo. Mice with enhanced RNAi will help to evaluate antiviral potential of mammalian RNAi in vivo.