Enhanced detection of viral RNA species using fokI-assisted digestion of DNA duplexes and DNA/RNA hybrids

The accurate detection of nucleic acids from certain biological pathogens is critical for the diagnosis of human diseases. However, amplified detection of RNA molecules from a complex sample by direct detection of RNA/DNA hybrids remains a challenge. Here, we show that type IIS endonuclease FokI is able to digest DNA duplexes and DNA/RNA hybrids when assisted by a dumbbell-like fluorescent sensing oligonucleotide. As proof of concept, we designed a battery of sensing oligonucleotides against specific regions of the SARS-CoV-2 genome and interrogated the role of FokI relaxation as a potential nicking enzyme for fluorescence signal amplification. FokI-assisted digestion of SARS-CoV-2 probes increases the detection signal of ssDNA and RNA molecules and decreases the limit of detection more than 3.5-fold as compared to conventional molecular beacon approaches. This cleavage reaction is highly specific to its target molecules, and no detection of other highly related B-coronaviruses was observed in the presence of complex RNA mixtures. In addition, the FokI-assisted reaction has a high multiplexing potential, as the combined detection of different viral RNAs, including different SARS-CoV-2 variants, was achieved in the presence of multiple combinations of fluorophores and sensing oligonucleotides. When combined with isothermal rolling circle amplification technologies, FokI-assisted digestion reduced the detection time of SARS-CoV-2 in COVID-19-positive human samples with adequate sensitivity and specificity compared to conventional reverse transcription polymerase chain reaction approaches, highlighting the potential of FokI-assisted signal amplification as a valuable sensing mechanism for the detection of human pathogens.Funding was provided by the ISCIII (COV00624 to J.R.T. andM.F.F., PI18/01527 and PI21/01067 to M.F.F.), CSIC (202020E092 to M.F.F), the European Commission NextGenerationEU, through CSIC’s Global Health Platform (PTI Salud Global) and the Spanish Ministry of Science and Innovation through the Recovery, Transformation and Resilience Plan (GL2021-03-39 and GL2021-03-040), the PCTI from the Asturias Government, co-funded by 2018−2022/FEDER (IDI/2018/146 to M.F.F.), the AECC (PROYE18061FERN to M.F.F), ISPA-Janssen (048-Intramural Nov-Tevar to J.R.T.) and the IUOPA. J.R.T is supported by a JdC fellowship from the Spanish Ministry of Science and Innovation (IJC2018-36825-I). R.F.P. and P.S.O. are supported by the Severo Ochoa program (BP17-114 and BP17-165). A.P. is supported by the PFIS program (ISCIII, FI19/ 00085). J.J.A.L. is supported by the AECC fellowship. C.M. and V.L. are supported by IUOPA, and R.G.U. is supported by CIBERER.Peer reviewe

Physical exercise shapes the mouse brain epigenome

[Objective]: To analyze the genome-wide epigenomic and transcriptomic changes induced by long term resistance or endurance training in the hippocampus of wild-type mice.[Methods]: We performed whole-genome bisulfite sequencing (WGBS) and RNA sequencing (RNA-seq) of mice hippocampus after 4 weeks of specific training. In addition, we used a novel object recognition test before and after the intervention to determine whether the exercise led to an improvement in cognitive function.[Results]: Although the majority of DNA methylation changes identified in this study were training-model specific, most were associated with hypomethylation and were enriched in similar histone marks, chromatin states, and transcription factor biding sites. It is worth highlighting the significant association found between the loss of DNA methylation in Tet1 binding sites and gene expression changes, indicating the importance of these epigenomic changes in transcriptional regulation. However, endurance and resistance training activate different gene pathways, those being associated with neuroplasticity in the case of endurance exercise, and interferon response pathways in the case of resistance exercise, which also appears to be associated with improved learning and memory functions.[Conclusions]: Our results help both understand the molecular mechanisms by which different exercise models exert beneficial effects for brain health and provide new potential therapeutic targets for future research.This work was supported by the Spanish Association Against Cancer (PROYE18061FERN to M.F.F.), the Asturias Government (PCTI) co-funding 2018-2022/FEDER (IDI/2018/146 to M.F.F.), the Fundación General CSIC (0348_CIE_6_E to M.F.F.), the Health Institute Carlos III (Plan Nacional de I+D+I) co-funding FEDER (PI18/01527 to M.F.F and A.F.F.), the MINECO (DEP2015-69980-P to B.F.G.), and the Fundación Tatiana Pérez de Guzmán el Bueno (“Ayudas a Proyectos de Investigación en Neurociencia-2020” to C.T.Z and E.I.G.). R.G.U. is supported by the Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER). J.R.T. is supported by a Juan de la Cierva fellowship from the Spanish Ministry of Science and Innovation MCIN/AEI /10.13039/501100011033 (IJC2018-036825-I). R.F.P. is supported by the Severo Ochoa program (BP17-114). P.P.H. is supported by Ayudas para la realización de Tesis Doctorales. Modalidad A fellowship from the University of Oviedo (PAPI-20-PF-19). We also acknowledge support from the IUOPA-ISPA-FINBA (the IUOPA is supported by the Obra Social Cajastur-Liberbank, Spain).Peer reviewe

Classification of follicular-patterned thyroid lesions using a minimal set of epigenetic biomarkers

[Objective]: The minimally invasive fine-needle aspiration cytology (FNAC) is the current gold standard for the diagnosis of thyroid nodule malignancy. However, the correct discrimination of follicular neoplasia often requires more invasive diagnostic techniques. The lack of suitable immunohistochemical markers to distinguish between follicular thyroid carcinoma and other types of follicular-derived lesions complicates diagnosis, and despite most of these tumours being surgically resected, only a small number will test positive for malignancy. As such, the development of new orthogonal diagnostic approaches may improve the accuracy of diagnosing thyroid nodules.[Design]: This study includes a retrospective, multi-centre training cohort including 54 fresh-frozen follicular-patterned thyroid samples and two independent, multi-centre validation cohorts of 103 snap-frozen biopsies and 33 FNAC samples, respectively.[Methods]: We performed a genome-wide genetic and epigenetic profiling of 54 fresh-frozen follicular-patterned thyroid samples using exome sequencing and the Illumina Human DNA Methylation EPIC platform. An extensive validation was performed using the bisulfite pyrosequencing technique.[Results]: Using a random forest approach, we developed a three-CpG marker-based diagnostic model that was subsequently validated using bisulfite pyrosequencing experiments. According to the validation cohort, this cost-effective method discriminates between benign and malignant nodules with a sensitivity and specificity of 97 and 88%, respectively (positive predictive value (PPV): 0.85, negative predictive value (NPV): 0.98).[Conclusions]: Our classification system based on a minimal set of epigenetic biomarkers can complement the potential of the diagnostic techniques currently available and would prioritize a considerable number of surgical interventions that are often performed due to uncertain cytology.[Significance statement]: In recent years, there has been a significant increase in the number of people diagnosed with thyroid nodules. The current challenge is their etiological diagnosis to discount malignancy without resorting to thyroidectomy. The method proposed here, based on DNA pyrosequencing assays, has high sensitivity (0.97) and specificity (0.88) for the identification of malignant thyroid nodules. This simple and cost-effective approach can complement expert pathologist evaluation to prioritize the classification of difficult-to-diagnose follicular-patterned thyroid lesions and track tumor evolution, including real-time monitoring of treatment efficacy, thereby stimulating adherence to health promotion programs.Peer reviewe

CRISPR/dCAS9-mediated DNA demethylation screen identifies functional epigenetic determinants of colorectal cancer

Abstract Background Promoter hypermethylation of tumour suppressor genes is frequently observed during the malignant transformation of colorectal cancer (CRC). However, whether this epigenetic mechanism is functional in cancer or is a mere consequence of the carcinogenic process remains to be elucidated. Results In this work, we performed an integrative multi-omic approach to identify gene candidates with strong correlations between DNA methylation and gene expression in human CRC samples and a set of 8 colon cancer cell lines. As a proof of concept, we combined recent CRISPR-Cas9 epigenome editing tools (dCas9-TET1, dCas9-TET-IM) with a customized arrayed gRNA library to modulate the DNA methylation status of 56 promoters previously linked with strong epigenetic repression in CRC, and we monitored the potential functional consequences of this DNA methylation loss by means of a high-content cell proliferation screen. Overall, the epigenetic modulation of most of these DNA methylated regions had a mild impact on the reactivation of gene expression and on the viability of cancer cells. Interestingly, we found that epigenetic reactivation of RSPO2 in the tumour context was associated with a significant impairment in cell proliferation in p53−/− cancer cell lines, and further validation with human samples demonstrated that the epigenetic silencing of RSPO2 is a mid-late event in the adenoma to carcinoma sequence. Conclusions These results highlight the potential role of DNA methylation as a driver mechanism of CRC and paves the way for the identification of novel therapeutic windows based on the epigenetic reactivation of certain tumour suppressor genes