Generation of a Mouse Model with Down-Regulated U50 snoRNA (SNORD50) Expression and Its Organ-Specific Phenotypic Modulation

Abstract

Box C/D-type small nucleolar RNAs (snoRNAs) are functional RNAs responsible for mediating 2′-O-ribose methylation of ribosomal RNAs (rRNAs) within the nucleolus. In the past years, evidence for the involvement of human U50 snoRNA in tumorigenesis has been accumulating. We previously identified U50HG, a non-protein-coding gene that hosted a box C/D-type U50 snoRNA, in a chromosomal breakpoint in a human B-cell lymphoma. Mouse genome analysis revealed four mouse U50 (mU50) host-genes: three mU50HG-a gene variants that were clustered in the genome and an mU50HG-b gene that we supposed to be the U50HG ortholog. In this study, to investigate the physiological importance of mU50 snoRNA and its involvement in tumorigenesis, we eliminated mU50 snoRNA sequences from the mU50HG-b gene. The established mouse line (ΔmU50(HG-b)) showed a significant reduction of mU50 snoRNA expression without alteration of the host-gene length and exon-intron structure, and the corresponding target rRNA methylation in various organs was reduced. Lifelong phenotypic monitoring showed that the ΔmU50(HG-b) mice looked almost normal without accelerated tumorigenicity; however, a notable difference was the propensity for anomalies in the lymphoid organs. Transcriptome analysis showed that dozens of genes, including heat shock proteins, were differentially expressed in ΔmU50(HG-b) mouse lymphocytes. This unique model of a single snoRNA knockdown with intact host-gene expression revealed further new insights into the discrete transcriptional regulation of multiple mU50 host-genes and the complicated dynamics involved in organ-specific processing and maintenance of snoRNAs.

The R2TP chaperone complex: its involvement in snoRNP assembly and tumorigenesis

“…In mice, deletion of U50 snoRNA decreased methylation levels of the target rRNA, however, no significant growth phenotype or tumorigenesis were observed. Subtle effects on lymphoid organs such as splenomegaly and swollen lymph nodes were observed more frequently compared to wildtype mice (51). Additionally, other snoRNAs (SNORD43, SNORD44 and SNORD48) are known to have decreased expression levels in cancer cells, although it mechanism has not been elucidated (52).…”

C/D-box snoRNA-derived RNA production is associated with malignant transformation and metastatic progression in prostate cancer

“…Still, several reports show that snoRNAs have tissue-specific expression [ 4 , 5 ], and may present as novel cancer biomarkers. For example, the H/ACA-box snoRNA SNORA42 is commonly overexpressed in non-small cell lung cancer (NSCLC) and its expression is significantly inversely correlated with survival [ 6 , 7 ].…”

The emerging landscape of small nucleolar RNAs in cell biology

“…The biological significance of many of these noncanonical functions still remains unclear and will require further experimentation, including demonstration and characterization in vivo . The small number of snoRNA knockout models and in vivo studies in mouse offer significant insights and new perspectives into the global role of specific snoRNAs on phenotypic, physiological, and molecular levels, including their dynamic expression and target gene modification/expression (rRNA as well as mRNA targets) . Such in vivo models, combined with the ever increasing number of innovative new flavors of high‐throughput sequencing and proteomics methodologies, will undoubtedly contribute to clarifying the cellular roles of this intriguing family of ncRNA over the next few years.…”