A myriad of structurally and functionally diverse noncoding RNAs (ncRNAs) have recently been implicated in numerous human diseases including cancer. Small nucleolar RNAs (snoRNAs), the most abundant group of intron-encoded ncRNAs, are classified into two families (box C/D snoRNAs and box H/ACA snoRNAs) and are required for post-transcriptional modifications on ribosomal RNA (rRNA). There is now a growing appreciation that nucleotide modifications on rRNA may impart regulatory potential to the ribosome; however, the functional consequence of site-specific snoRNA-guided modifications remains poorly defined. Discovered almost 20 years ago, H/ACA snoRNAs are required for the conversion of specific uridine residues to pseudouridine on rRNA. Interestingly, recent reports indicate that the levels of subsets of H/ACA snoRNAs required for pseudouridine modifications at specific sites on rRNA are altered in several diseases, particularly cancer. In this review, we describe recent advances in understanding the downstream consequences of H/ACA snoRNA-guided modifications on ribosome function, discuss the possible mechanism by which H/ACA snoRNAs may be regulated, and explore prospective expanding functions of H/ACA snoRNAs. Furthermore, we discuss the potential biological implications of alterations in H/ACA snoRNA expression in several human diseases.

Noncoding RNAs control critical cellular processes, although their contribution to disease remains largely unexplored. Dyskerin associates with hundreds of H/ACA small RNAs to generate a multitude of functionally distinct ribonucleoproteins (RNPs). The DKC1 gene, encoding dyskerin, is mutated in the multisystem disorder X-linked dyskeratosis congenita (X-DC). A central question is whether DKC1 mutations affect the stability of H/ACA RNPs, including those modifying ribosomal RNA (rRNA). We carried out comprehensive profiling of dyskerin-associated H/ACA RNPs, revealing remarkable heterogeneity in the expression and function of subsets of H/ACA small RNAs in X-DC patient cells. Using a mass spectrometry approach, we uncovered single-nucleotide perturbations in dyskerin-guided rRNA modifications, providing functional readouts of small RNA dysfunction in X-DC. In addition, we identified that, strikingly, the catalytic activity of dyskerin is required for accurate hematopoietic stem cell differentiation. Altogether, these findings reveal that small noncoding RNA dysfunctions may contribute to the pleiotropic manifestation of human disease.

Small nucleolar RNAs (snoRNAs) are a diverse group of non-coding RNAs that direct chemical modifications at specific residues on other RNA molecules, primarily on ribosomal RNA (rRNA). SnoRNAs are altered in several cancers; however, their role in cell homeostasis as well as in cellular transformation remains poorly explored. Here, we show that specific subsets of snoRNAs are differentially regulated during the earliest cellular response to oncogenic RASG12V expression. We describe a novel function for one H/ACA snoRNA, SNORA24, which guides two pseudouridine modifications within the small ribosomal subunit, in RAS-induced senescence in vivo. We find that in mouse models, loss of Snora24 cooperates with RASG12V to promote the development of liver cancer that closely resembles human steatohepatitic hepatocellular carcinoma (HCC). From a clinical perspective, we further show that human HCCs with low SNORA24 expression display increased lipid content and are associated with poor patient survival. We next asked whether ribosomes lacking SNORA24-guided pseudouridine modifications on 18S rRNA have alterations in their biophysical properties. Single-molecule Fluorescence Resonance Energy Transfer (FRET) analyses revealed that these ribosomes exhibit perturbations in aminoacyl-transfer RNA (aa-tRNA) selection and altered pre-translocation ribosome complex dynamics. Furthermore, we find that HCC cells lacking SNORA24-guided pseudouridine modifications have increased translational miscoding and stop codon readthrough frequencies. These findings highlight a role for specific snoRNAs in safeguarding against oncogenic insult and demonstrate a functional link between H/ACA snoRNAs regulated by RAS and the biophysical properties of ribosomes in cancer.

Background

The negative symptoms of schizophrenia include deficits in emotional expression and motivation. These deficits are stable over the course of illness and respond poorly to current medications. Previous studies have focused on negative symptoms as a single category; however, individual symptoms might be related to separate neurological disturbances. We analyzed data from the Functional Biomedical Informatics Research Network dataset to explore the relationship between individual negative symptoms and functional brain activity during an auditory oddball task.

Methods

Functional magnetic resonance imaging was conducted on 89 schizophrenia patients and 106 healthy controls during a two-tone auditory oddball task. Blood oxygenation level-dependent (BOLD) signal during the target tone was correlated with severity of five negative symptom domains from the Scale for the Assessment of Negative Symptoms.

Results

The severity of alogia, avolition/apathy and anhedonia/asociality was negatively correlated with BOLD activity in distinct sets of brain regions associated with processing of the target tone, including basal ganglia, thalamus, insular cortex, prefrontal cortex, posterior cingulate and parietal cortex.

Conclusions

Individual symptoms were related to different patterns of functional activation during the oddball task, suggesting that individual symptoms might arise from distinct neural mechanisms. This work has potential to inform interventions that target these symptom-related neural disruptions.

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder.