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OBJECTIVE The excess of visceral adipose tissue might hinder and delay immune response. How people with abdominal obesity (AO) will respond to mRNA vaccines against SARS-CoV-2 is yet to be established. We evaluated SARS-CoV-2 specific antibody responses after the first and second dose of the BNT162b2 mRNA vaccine comparing the response of individuals with AO to those without, discerning between individuals with or without prior infection. METHODS IgG neutralizing antibodies against the Trimeric-complex (IgG-TrimericS) were measured at four time points: at baseline, at day 21 after vaccine dose 1, at one and three months after dose 2. Nucleocapsid antibodies were assessed to detect prior SARS-CoV-2 infection. Waist circumference was measured to determine AO. RESULTS Between the first and third month after vaccine dose 2, the drop in IgG-TrimericS levels was more remarkable in individuals with AO compared to those without AO (2.44 fold [95%CI: 2.22-2.63] vs 1.82 fold [95%CI: 1.69-1.92], respectively, p

ObjectiveThe excess of visceral adipose tissue might hinder and delay the immune response. How people with abdominal obesity will respond to mRNA vaccines against SARS-CoV-2 is yet to be established. We evaluated SARS-CoV-2-specific antibody responses after the first and second dose of the BNT162b2 mRNA vaccine comparing the response of individuals affected by abdominal obesity (AO) to those without, discerning between individuals with or without prior infection.MethodsIgG neutralizing antibodies against the Trimeric complex (IgG-TrimericS) were measured at four time points: at baseline, at day 21 after vaccine dose-1, at one month and three months after dose-2. Nucleocapsid antibodies were assessed to detect prior SARS-CoV-2 infection. Waist circumference was measured to determine abdominal obesity.ResultsBetween the first and third month after vaccine dose-2, the drop in IgG-TrimericS levels was more remarkable in individuals with AO compared to those without AO (2.44 fold [95%CI: 2.22-2.63] vs 1.82 fold [95%CI: 1.69-1.92], respectively, pConclusionsOur findings highlight the need to extend the duration of serological monitoring of antibody levels in infection-naive individuals with abdominal obesity, a higher-risk population category in terms of possible weaker antibody response.

Dysfunctions in the endo-lysosomal system have been hypothesized to underlie neurodegeneration in major neurocognitive disorders due to Alzheimer's disease (AD), Frontotemporal Lobar Degeneration (FTLD), and Lewy body disease (DLB). The aim of this study is to investigate whether these diseases share genetic variability in the endo-lysosomal pathway. In AD, DLB, and FTLD patients and in controls (948 subjects), we performed a targeted sequencing of the top 50 genes belonging to the endo-lysosomal pathway. Genetic analyses revealed (i) four previously reported disease-associated variants in the SORL1 (p.N1246K, p.N371T, p.D2065V) and DNAJC6 genes (p.M133L) in AD, FTLD, and DLB, extending the previous knowledge attesting SORL1 and DNAJC6 as AD- and PD-related genes, respectively; (ii) three predicted null variants in AD patients in the SORL1 (p.R985X in early onset familial AD, p.R1207X) and PPT1 (p.R48X in early onset familial AD) genes, where loss of function is a known disease mechanism. A single variant and gene burden analysis revealed some nominally significant results of potential interest for SORL1 and DNAJC6 genes. Our data highlight that genes controlling key endo-lysosomal processes (i.e., protein sorting/transport, clathrin-coated vesicle uncoating, lysosomal enzymatic activity regulation) might be involved in AD, FTLD and DLB pathogenesis, thus suggesting an etiological link behind these diseases. ispartof: INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES vol:22 issue:24 ispartof: location:Switzerland status: published

Background: Frontotemporal lobar degeneration (FTLD) designates a group of neurodegenerative diseases with remarkable clinical, pathological, and genetic heterogeneity. Mutations in progranulin gene (GRN) are among the most common causes of familial FTLD. The GRN C157KfsX97 mutation is the most frequent mutation occurring in Southern Italy and has been already described in a previous work. Objective: In this study, we reported on additional cases carrying the same mutation and performed a genetic study on the whole cohort, aiming at demonstrating the existence of a founder effect and estimating the age of this mutation. Methods/Results: Based on the haplotype sharing analysis, a founder effect was highly probable, while the age of the mutation, estimated by means of DMLE+ software, resulted in a range between 52 and 82 generations, with the highest frequency at about 62 generations, 1,550 years ago. Conclusion: This is the first study that reports the age estimation of the most recent common ancestor for the GRN C157KfsX97 mutation recurring in Southern Italy. Mutation dating in a geographically restricted population may be useful in order to plan genetic counseling and screening programs in the field of public health.

Myotonic dystrophy type 1 (DM1) is a multi-systemic disorder caused by abnormally expanded stretches of CTG DNA triplets in the DMPK gene, leading to mutated-transcript RNA-toxicity. MicroRNAs (miRNAs) are short non-coding RNAs that, after maturation, are loaded onto the RISC effector complex that destabilizes target mRNAs and represses their translation. In DM1 muscle biopsies not only the expression, but also the intracellular localization of specific miRNAs is disrupted, leading to the dysregulation of the relevant mRNA targets. To investigate the functional alterations of the miRNA/target interactions in DM1, we analyzed by RNA-sequencing the RISC-associated RNAs in skeletal muscle biopsies derived from DM1 patients and matched controls. The mRNAs found deregulated in DM1 biopsies were involved in pathways and functions relevant for the disease, such as energetic metabolism, calcium signaling, muscle contraction and p53-dependent apoptosis. Bioinformatic analysis of the miRNA/mRNA interactions based on the RISC enrichment profiles, identified 24 miRNA/mRNA correlations. Following validation in 21 independent samples, we focused on the couple miR-29c/ASB2 because of the role of miR-29c in fibrosis (a feature of late-stage DM1 patients) and of ASB2 in the regulation of muscle mass. Luciferase reporter assay confirmed the direct interaction between miR-29c and ASB2. Moreover, decreased miR-29c and increased ASB2 levels were verified also in immortalized myogenic cells and primary fibroblasts, derived from biopsies of DM1 patients and controls. CRISPR/Cas9-mediated deletion of CTG expansions rescued normal miR-29c and ASB2 levels, indicating a direct link between the mutant repeats and the miRNA/target expression. In conclusion, functionally relevant miRNA/mRNA interactions were identified in skeletal muscles of DM1 patients, highlighting the dysfunction of miR-29c and ASB2.

Frontotemporal dementia (FTD) is a common form of dementia among early-onset cases. Several genetic factors for FTD have been revealed, but a large proportion of FTD cases still have an unidentified genetic origin. Recent studies highlighted common pathobiological mechanisms among neurodegenerative diseases. In the present study, we investigated a panel of candidate genes, previously described to be associated with FTD and/or other neurodegenerative diseases by targeted next generation sequencing (NGS). We focused our study on sporadic FTD (sFTD), devoid of disease-causing mutations in GRN, MAPT and C9orf72. Since genetic factors have a substantially higher pathogenetic contribution in early onset patients than in late onset dementia, we selected patients with early onset (&lt, 65 years). Our study revealed that, in 50% of patients, rare missense potentially pathogenetic variants in genes previously associated with Alzheimer&rsquo, s disease, Parkinson disease, amyotrophic lateral sclerosis and Lewy body dementia (GBA, ABCA7, PARK7, FUS, SORL1, LRRK2, ALS2), confirming genetic pleiotropy in neurodegeneration. In parallel, a synergic genetic effect on FTD is suggested by the presence of variants in five different genes in one single patient. Further studies employing genome-wide approaches might highlight pathogenic variants in novel genes that explain the still missing heritability of FTD.

Aims Antisense long noncoding RNAs (ncRNAs) are transcripts emerging from the opposite strand of a coding-RNA region and their role in heart failure (HF) is largely unknown. Additionally, HF and Alzheimer's disease (AD) share several non-genetic effectors and risk factors. We investigated the regulation of the β-secretase-1 (BACE1) gene and of its antisense transcript BACE1-AS in ischaemic HF. Methods and results BACE1 and BACE1-AS expression was measured in left ventricle biopsies from 18 patients affected by non-end stage ischaemic HF and 17 matched controls. The levels of both transcripts were increased in HF patients. Likewise, both transcripts increased also in a mouse model of ischaemic HF, and their expression was directly correlated. BACE1-AS was expressed by all cardiac cell types and BACE1-AS up- or down-modulation in cultured cardiomyocytes and endothelial cells induced a concordant regulation of the cognate BACE1 transcript. Interestingly, BACE1 increase also induced the intracellular accumulation of its product β-amyloid. In keeping with these findings, higher BACE1 protein and β-amyloid peptide levels were also observed in HF. Moreover, increased β-amyloid 1-40 was also found in the plasma of HF patients. Transcriptomic changes of BACE1-AS overexpressing and β-amyloid 1-40 treated cells were largely overlapping and indicated changes of relevant biological process such as 'cell cycle and proliferation', 'apoptosis', and 'DNA repair' as well as 'TGFβ-, TNFα-, p38-, EGFR-signalling', suggesting a potential maladaptive role of the BACE1-AS/BACE1/β-amyloid axis. Accordingly, the administration of β-amyloid peptides decreased the cell viability in endothelial cells and in both human IPS-derived and mouse cardiomyocytes. Moreover, both β-amyloid treatment and BACE1-AS overexpression increased endothelial cell apoptosis, and this effect was prevented by BACE1 silencing. Conclusion Given the neurotoxic role of β-amyloid in AD, dysregulation of the BACE1/BACE1-AS/β-amyloid axis might be relevant in HF pathogenesis, further implicating ncRNAs in the complex scenario of proteotoxicity in cardiac dysfunction.

Circular RNAs (circRNAs) constitute a recently re-discovered class of non-coding RNAs functioning as sponge for miRNAs and proteins, affecting RNA splicing and regulating transcription. CircRNAs are generated by “back-splicing”, linking covalently 3’- and 5’-ends of exons. Thus, circRNA levels might be deregulated in conditions associated to altered RNA-splicing. Indeed, increasing evidence indicates their role in human diseases. Specifically, myotonic dystrophy type 1 (DM1) is a multisystemic disorder caused by expanded CTG-repeats in the DMPK gene, resulting in abnormal mRNA-splicing. In this investigation, circRNAs expressed in DM1 skeletal muscles were identified by analyzing RNA-sequencing data-sets followed by qPCR validation. In muscle biopsies, out of 9 tested, 4 transcripts showed an increased circular fraction: CDYL, HIPK3, RTN4_03 and ZNF609. The circular fraction values correlated positively with skeletal muscle strength and Receiver-Operating-Characteristics curves showed that these four circRNAs allow to distinguish DM1 patients from controls. The identified circRNAs were also detectable in peripheral-blood-mononuclear-cells (PBMCs) and plasma of DM1 patients, but they were not regulated significantly, indicating a tissue-selectivity of the identified modulations. Finally, increased circular fractions of RTN4_03 and ZNF609 were also observed in differentiated myogenic cell lines derived from DM1 patients. In conclusion, this proof-of-principle study identified circRNA dysregulation in DM1 patients.

The Hippo/YAP signaling pathway is a crucial regulator of tissue growth, stem cell activity, and tumorigenesis. However, the mechanism by which YAP controls transcription remains to be fully elucidated. Here, we utilize global chromatin occupancy analyses to demonstrate that robust YAP binding is restricted to a relatively small number of distal regulatory elements in the genome. YAP occupancy defines a subset of enhancers and superenhancers with the highest transcriptional outputs. YAP modulates transcription from these elements predominantly by regulating promoter-proximal polymerase II (Pol II) pause release. Mechanistically, YAP interacts and recruits the Mediator complex to enhancers, allowing the recruitment of the CDK9 elongating kinase. Genetic and chemical perturbation experiments demonstrate the requirement for Mediator and CDK9 in YAP-driven phenotypes of overgrowth and tumorigenesis. Our results here uncover the molecular mechanisms employed by YAP to exert its growth and oncogenic functions, and suggest strategies for intervention.

SummaryThe role of the Hippo pathway effector YAP1 in soft tissue sarcomas is poorly defined. Here we report that YAP1 activity is elevated in human embryonal rhabdomyosarcoma (ERMS). In mice, sustained YAP1 hyperactivity in activated, but not quiescent, satellite cells induces ERMS with high penetrance and short latency. Via its transcriptional program with TEAD1, YAP1 directly regulates several major hallmarks of ERMS. YAP1-TEAD1 upregulate pro-proliferative and oncogenic genes and maintain the ERMS differentiation block by interfering with MYOD1 and MEF2 pro-differentiation activities. Normalization of YAP1 expression reduces tumor burden in human ERMS xenografts and allows YAP1-driven ERMS to differentiate in situ. Collectively, our results identify YAP1 as a potent ERMS oncogenic driver and a promising target for differentiation therapy.

PRDM proteins belong to the SET domain protein family, which is involved in the regulation of gene expression. Although few PRDM members possess histone methyltransferase activity, the molecular mechanisms by which the other members exert transcriptional regulation remain to be delineated. In this study, we find that Prdm5 is highly expressed in mouse embryonic stem (mES) cells and exploit this cellular system to characterize molecular functions of Prdm5. By combining proteomics and next-generation sequencing technologies, we identify Prdm5 interaction partners and genomic occupancy. We demonstrate that although Prdm5 is dispensable for mES cell maintenance, it directly targets genomic regions involved in early embryonic development and affects the expression of a subset of developmental regulators during cell differentiation. Importantly, Prdm5 interacts with Ctcf, cohesin, and TFIIIC and cooccupies genomic loci. In summary, our data indicate how Prdm5 modulates transcription by interacting with factors involved in genome organization in mouse embryonic stem cells.

PRDM proteins are tissue-specific transcription factors often deregulated in diseases, particularly in cancer where different members have been found to act as oncogenes or tumor suppressors. PRDM5 is a poorly characterized member of the PRDM family for which several studies have reported a high frequency of promoter hypermethylation in cancer types of gastrointestinal origin. We report here the characterization of Prdm5 knockout mice in the context of intestinal carcinogenesis. We demonstrate that loss of Prdm5 increases the number of adenomas throughout the murine small intestine on an Apc(Min) background. By using the genome-wide ChIP-seq (chromatin immunoprecipitation (ChIP) followed by DNA sequencing) and transcriptome analyses we identify loci encoding proteins involved in metabolic processes as prominent PRDM5 targets and characterize monoacylglycerol lipase (Mgll) as a direct PRDM5 target in human colon cancer cells and in Prdm5 mutant mouse intestines. Moreover, we report the downregulation of PRDM5 protein expression in human colon neoplastic lesions. In summary, our data provide the first causal link between Prdm5 loss and intestinal carcinogenesis, and uncover an extensive and novel PRDM5 target repertoire likely facilitating the tumor-suppressive functions of PRDM5.

Background RNAseq provides remarkable power in the area of biomarkers discovery and disease stratification. The main technical steps affecting the results of RNAseq experiments are Library Sample Preparation (LSP) and Bioinformatics Analysis (BA). At the best of our knowledge, a comparative evaluation of the combined effect of LSP and BA was never considered and it might represent a valuable knowledge to optimize alternative splicing detection, which is a challenging task due to moderate fold change differences to be detected within a complex isoforms background. Results Different LSPs (TruSeq unstranded/stranded, ScriptSeq, NuGEN) allow the detection of a large common set of isoforms. However, each LSP also detects a smaller set of isoforms, which are characterized both by lower coverage and lower FPKM than that observed for the common ones among LSPs. This characteristic is particularly critical in case of low input RNA NuGEN v2 LSP. The effect on statistical detection of alternative splicing considering low input LSP (NuGEN v2) with respect to high input LSP (TruSeq) on statistical detection of alternative splicing was studied using a benchmark dataset, in which both synthetic reads and reads generated from high (TruSeq) and low input (NuGEN) LSPs were spiked-in. Statistical detection of alternative splicing (AltDE) was done using prototypes of BA for isoform-reconstruction (Cuffdiff) and exon-level analysis (DEXSeq). Exon-level analysis performs slightly better than isoform-reconstruction approach although at most only 50% of the spiked-in transcripts are detected. Both isoform-reconstruction and exon-level analysis performances improve by rising the number of input reads. Conclusion Data, derived from NuGEN v2, are not the ideal input for AltDE, specifically when exon-level approach is used. It is notable that ribosomal depletion, with respect to polyA+ selection, reduces the amount of coding mappable reads resulting detrimental in the case of AltDE. Furthermore, we observed that both isoform-reconstruction and exon-level analysis performances are strongly dependent on the number of input reads.

BACKGROUND: Non-small cell lung cancer (NSCLC) accounts for 81% of all cases of lung cancer and they are often fatal because 60% of the patients are diagnosed at an advanced stage. Besides the need for earlier diagnosis, there is a high need for additional effective therapies. In this work, we investigated the feasibility of a lung cancer progression mouse model, mimicking features of human aggressive NSCLC, as biological reservoir for potential therapeutic targets and biomarkers.,RESULTS: We performed RNA-seq profiling on total RNA extracted from lungs of a 30 week-old K-ras(LA1)/p53(R172H?g) and wild type (WT) mice to detect fusion genes and gene/exon-level differential expression associated to the increase of tumor mass. Fusion events were not detected in K-ras(LA1)/p53(R172H?g) tumors. Differential expression at exon-level detected 33 genes with differential exon usage. Among them nine, i.e. those secreted or expressed on the plasma membrane, were used for a meta-analysis of more than 500 NSCLC RNA-seq transcriptomes. None of the genes showed a significant correlation between exon-level expression and disease prognosis. Differential expression at gene-level allowed the identification of 1513 genes with a significant increase in expression associated to tumor mass increase. 74 genes, i.e. those secreted or expressed on the plasma membrane, were used for a meta-analysis of two transcriptomics datasets of human NSCLC samples, encompassing more than 900 samples. SPP1 was the only molecule whose over-expression resulted statistically related to poor outcome regarding both survival and metastasis formation. Two other molecules showed over-expression associated to poor outcome due to metastasis formation: GM-CSF and ADORA3. GM-CSF is a secreted protein, and we confirmed its expression in the supernatant of a cell line derived by a K-ras(LA1)/p53(R172H?g) mouse tumor. ADORA3 is instead involved in the induction of p53-mediated apoptosis in lung cancer cell lines. Since in our model p53 is inactivated, ADORA3 does not negatively affect tumor growth but remains expressed on tumor cells. Thus, it could represent an interesting target for the development of antibody-targeted therapy on a subset of NSCLC, which are p53 null and ADORA3 positive.,CONCLUSIONS: Our study provided a complete transcription overview of the K-ras(LA1)/p53(R172H?g) mouse NSCLC model. This approach allowed the detection of ADORA3 as a potential target for antibody-based therapy in p53 mutated tumors.

Cardiac overexpression of locally acting muscle-restricted (m)IGF-1 and the consequent downstream activation of NAD+-dependent protein deacetylase sirtuin 1 (SIRT1) trigger potent cardiac antioxidative and antihypertrophic effects. Transient receptor potential (TRP) cation channel A1 (TRPA1) belongs to the TRP ion channel family of molecular detectors of thermal and chemical stimuli that activate sensory neurons to produce pain. Recently, it has been shown that TRPA1 activity influences blood pressure, but the significance of TRPA1 in the cardiovascular system remains elusive. In the present work, using genomic screening in mouse hearts, we found that TRPA1 is a target of mIGF-1/SIRT1 signaling. TRPA1 expression is increased in the heart of cardiac-restricted mIGF-1 transgenic (Tg) mice, both in cardiomyocytes and noncardiomyocytes. In wild-type mice, SIRT1 occupied the TRPA1 promoter, inhibiting its expression, whereas in the presence of the cardiac mIGF-1 transgene, SIRT1 was displaced from the TRPA1 promoter, leading to an increase in its expression. Cardiac-specific ablation of SIRT1 (cardiac-specific knockout) in mIGF-1 Tg mice paradoxically did not increase TRPA1 expression. We have recently reported a systemic “hormetic” effect in mIGF-1 Tg mice, mild hypertension, which was depleted upon cardiac-specific knockout of SIRT1. Administration of the selective TRPA1 antagonist HC-030031 to mIGF-1 Tg mice restored blood pressure to basal levels. We identified TRPA1 as a functional target of the cardiac mIGF-1/SIRT1 signaling pathway, which may have pharmacological implications for the management of cardiovascular stress.

Overexpression of the histone methyltransferase MMSET in t(4;14)+ multiple myeloma patients is believed to be the driving factor in the pathogenesis of this subtype of myeloma. MMSET catalyzes dimethylation of lysine 36 on histone H3 (H3K36me2), and its overexpression causes a global increase in H3K36me2, redistributing this mark in a broad, elevated level across the genome. Here, we demonstrate that an increased level of MMSET also induces a global reduction of lysine 27 trimethylation on histone H3 (H3K27me3). Despite the net decrease in H3K27 methylation, specific genomic loci exhibit enhanced recruitment of the EZH2 histone methyltransferase and become hypermethylated on this residue. These effects likely contribute to the myeloma phenotype since MMSET-overexpressing cells displayed increased sensitivity to EZH2 inhibition. Furthermore, we demonstrate that such MMSET-mediated epigenetic changes require a number of functional domains within the protein, including PHD domains that mediate MMSET recruitment to chromatin. In vivo, targeting of MMSET by an inducible shRNA reversed histone methylation changes and led to regression of established tumors in athymic mice. Together, our work elucidates previously unrecognized interplay between MMSET and EZH2 in myeloma oncogenesis and identifies domains to be considered when designing inhibitors of MMSET function., Author Summary Precise spatial and temporal gene expression is required for normal development, and aberrant regulation of gene expression is a common factor in many diseases, including cancer. Histone modifications contribute to the control of gene expression by altering chromatin structure and affecting the recruitment of transcriptional regulators. In this study, we demonstrate interplay between two oncogenic proteins, MMSET and EZH2, known to methylate histone H3 on lysine 36 (H3K36) and lysine 27 (H3K27), respectively. Overexpression of MMSET in myeloma cells increases global levels of H3K36 methylation, alters its normal distribution throughout the genome and decreases global levels of H3K27 methylation. We found that while the majority of the genome loses H3K27 methylation in the presence of MMSET, certain loci have augmented recruitment of EZH2 and enhanced H3K27 methylation, leading to transcriptional repression. Repression of these genes likely plays an important role in the disease because MMSET-overexpressing cells show higher sensitivity to small molecule inhibitors targeting EZH2-mediated methylation. Thus, our study suggests that the specific local changes may outweigh the gross global changes we frequently observe in cancer and implicates EZH2 as a novel therapeutic target in myeloma cells.

Background. Gene fusions arising from chromosomal translocations have been implicated in cancer. RNA-seq has the potential to discover such rearrangements generating functional proteins (chimera/fusion). Recently, many methods for chimeras detection have been published. However, specificity and sensitivity of those tools were not extensively investigated in a comparative way.Results. We tested eight fusion-detection tools (FusionHunter, FusionMap, FusionFinder, MapSplice, deFuse, Bellerophontes, ChimeraScan, and TopHat-fusion) to detect fusion events using synthetic and real datasets encompassing chimeras. The comparison analysis run only on synthetic data could generate misleading results since we found no counterpart on real dataset. Furthermore, most tools report a very high number of false positive chimeras. In particular, the most sensitive tool, ChimeraScan, reports a large number of false positives that we were able to significantly reduce by devising and applying two filters to remove fusions not supported by fusion junction-spanning reads or encompassing large intronic regions.Conclusions. The discordant results obtained using synthetic and real datasets suggest that synthetic datasets encompassing fusion events may not fully catch the complexity of RNA-seq experiment. Moreover, fusion detection tools are still limited in sensitivity or specificity; thus, there is space for further improvement in the fusion-finder algorithms.

PRDM family members are transcriptional regulators involved in tissue specific differentiation. PRDM5 has been reported to predominantly repress transcription, but a characterization of its molecular functions in a relevant biological context is lacking. We demonstrate here that Prdm5 is highly expressed in developing bones; and, by genome-wide mapping of Prdm5 occupancy in pre-osteoblastic cells, we uncover a novel and unique role for Prdm5 in targeting all mouse collagen genes as well as several SLRP proteoglycan genes. In particular, we show that Prdm5 controls both Collagen I transcription and fibrillogenesis by binding inside the Col1a1 gene body and maintaining RNA polymerase II occupancy. In vivo, Prdm5 loss results in delayed ossification involving a pronounced impairment in the assembly of fibrillar collagens. Collectively, our results define a novel role for Prdm5 in sustaining the transcriptional program necessary to the proper assembly of osteoblastic extracellular matrix., Author Summary Bone provides the essential tensile strength of the skeletal system, constitutes an important storage for minerals, and hosts the initial differentiation stages of the hematopoietic system. In addition, bones are important endocrine organs affecting organismal metabolism. Consequently, many human diseases arise from defects in bone formation or homeostasis. Hence, deciphering the molecular mechanisms underlying bone formation is essential for understanding the basis of bone and extracellular matrix-associated diseases. Here, we provide a detailed characterization of the cellular and molecular functions of the transcription factor Prdm5 during murine bone formation in vivo and find that Prdm5 is expressed in skeletal structures during development and that its loss impacts the ossification process, leading to a decrease in bone mineral density. A genome-wide mapping of Prdm5 binding sites in pre-osteoblastic cells reveals an unprecedented role for a transcription factor in targeting virtually all members of the Collagen and SLRP gene families. Interestingly, Prdm5 predominantly binds exonic regions of collagen genes and associates with RNA Polymerase II to sustain Collagen I transcription.

Background RNA-seq has the potential to discover genes created by chromosomal rearrangements. Fusion genes, also known as "chimeras", are formed by the breakage and re-joining of two different chromosomes. It is known that chimeras have been implicated in the development of cancer. Few publications in the past showed the presence of fusion events also in normal tissue, but with very limited overlaps between their results. More recently, two fusion genes in normal tissues were detected using both RNA-seq and protein data. Due to heterogeneous results in identifying chimeras in normal tissue, we decided to evaluate the efficacy of state of the art fusion finders in detecting chimeras in RNA-seq data from normal tissues. Results We compared the performance of six fusion-finder tools: FusionHunter, FusionMap, FusionFinder, MapSplice, deFuse and TopHat-fusion. To evaluate the sensitivity we used a synthetic dataset of fusion-products, called positive dataset; in these experiments FusionMap, FusionFinder, MapSplice, and TopHat-fusion are able to detect more than 78% of fusion genes. All tools were error prone with high variability among the tools, identifying some fusion genes not present in the synthetic dataset. To better investigate the false discovery chimera detection rate, synthetic datasets free of fusion-products, called negative datasets, were used. The negative datasets have different read lengths and quality scores, which allow detecting dependency of the tools on both these features. FusionMap, FusionFinder, mapSplice, deFuse and TopHat-fusion were error-prone. Only FusionHunter results were free of false positive. FusionMap gave the best compromise in terms of specificity in the negative dataset and of sensitivity in the positive dataset. Conclusions We have observed a dependency of the tools on read length, quality score and on the number of reads supporting each chimera. Thus, it is important to carefully select the software on the basis of the structure of the RNA-seq data under analysis. Furthermore, the sensitivity of chimera detection tools does not seem to be sufficient to provide results consistent with those obtained in normal tissues on the basis of fusion events extracted from published data.