Structural and non-coding variants increase the diagnostic yield of clinical whole genome sequencing for rare diseases

BACKGROUND

Whole genome sequencing is increasingly being used for the diagnosis of patients with rare diseases. However, the diagnostic yields of many studies, particularly those conducted in a healthcare setting, are often disappointingly low, at 25-30%. This is in part because although entire genomes are sequenced, analysis is often confined to in silico gene panels or coding regions of the genome.

METHODS

We undertook WGS on a cohort of 122 unrelated rare disease patients and their relatives (300 genomes) who had been pre-screened by gene panels or arrays. Patients were recruited from a broad spectrum of clinical specialties. We applied a bioinformatics pipeline that would allow comprehensive analysis of all variant types. We combined established bioinformatics tools for phenotypic and genomic analysis with our novel algorithms (SVRare, ALTSPLICE and GREEN-DB) to detect and annotate structural, splice site and non-coding variants.

RESULTS

Our diagnostic yield was 43/122 cases (35%), although 47/122 cases (39%) were considered solved when considering novel candidate genes with supporting functional data into account. Structural, splice site and deep intronic variants contributed to 20/47 (43%) of our solved cases. Five genes that are novel, or were novel at the time of discovery, were identified, whilst a further three genes are putative novel disease genes with evidence of causality. We identified variants of uncertain significance in a further fourteen candidate genes. The phenotypic spectrum associated with RMND1 was expanded to include polymicrogyria. Two patients with secondary findings in FBN1 and KCNQ1 were confirmed to have previously unidentified Marfan and long QT syndromes, respectively, and were referred for further clinical interventions. Clinical diagnoses were changed in six patients and treatment adjustments made for eight individuals, which for five patients was considered life-saving.

CONCLUSIONS

Genome sequencing is increasingly being considered as a first-line genetic test in routine clinical settings and can make a substantial contribution to rapidly identifying a causal aetiology for many patients, shortening their diagnostic odyssey. We have demonstrated that structural, splice site and intronic variants make a significant contribution to diagnostic yield and that comprehensive analysis of the entire genome is essential to maximise the value of clinical genome sequencing.

The developing mouse coronal suture at single-cell resolution

Sutures separate the flat bones of the skull and enable coordinated growth of the brain and overlying cranium. The coronal suture is most commonly fused in monogenic craniosynostosis, yet the unique aspects of its development remain incompletely understood. To uncover the cellular diversity within the murine embryonic coronal suture, we generated single-cell transcriptomes and performed extensive expression validation. We find distinct pre-osteoblast signatures between the bone fronts and periosteum, a ligament-like population above the suture that persists into adulthood, and a chondrogenic-like population in the dura mater underlying the suture. Lineage tracing reveals an embryonic Six2+ osteoprogenitor population that contributes to the postnatal suture mesenchyme, with these progenitors being preferentially affected in a Twist1+/-; Tcf12+/- mouse model of Saethre-Chotzen Syndrome. This single-cell atlas provides a resource for understanding the development of the coronal suture and the mechanisms for its loss in craniosynostosis.

The Dynamic Transcriptional Cell Atlas of Testis Development during Human Puberty

The human testis undergoes dramatic developmental and structural changes during puberty, including proliferation and maturation of somatic niche cells, and the onset of spermatogenesis. To characterize this understudied process, we profiled and analyzed single-cell transcriptomes of ∼10,000 testicular cells from four boys spanning puberty and compared them to those of infants and adults. During puberty, undifferentiated spermatogonia sequentially expand and differentiate prior to the initiation of gametogenesis. Notably, we identify a common pre-pubertal progenitor for Leydig and myoid cells and delineate candidate factors controlling pubertal differentiation. Furthermore, pre-pubertal Sertoli cells exhibit two distinct transcriptional states differing in metabolic profiles before converging to an alternative single mature population during puberty. Roles for testosterone in Sertoli cell maturation, antimicrobial peptide secretion, and spermatogonial differentiation are further highlighted through single-cell analysis of testosterone-suppressed transfemale testes. Taken together, our transcriptional atlas of the developing human testis provides multiple insights into developmental changes and key factors accompanying male puberty.

A de novo substitution in BCL11B leads to loss of interaction with transcriptional complexes and craniosynostosis

Craniosynostosis, the premature ossification of cranial sutures, is a developmental disorder of the skull vault, occurring in approximately 1 in 2250 births. The causes are heterogeneous, with a monogenic basis identified in ~25% of patients. Using whole-genome sequencing, we identified a novel, de novo variant in BCL11B, c.7C>A, encoding an R3S substitution (p.R3S), in a male patient with coronal suture synostosis. BCL11B is a transcription factor that interacts directly with the nucleosome remodelling and deacetylation complex (NuRD) and polycomb-related complex 2 (PRC2) through the invariant proteins RBBP4 and RBBP7. The p.R3S substitution occurs within a conserved amino-terminal motif (RRKQxxP) of BCL11B and reduces interaction with both transcriptional complexes. Equilibrium binding studies and molecular dynamics simulations show that the p.R3S substitution disrupts ionic coordination between BCL11B and the RBBP4-MTA1 complex, a subassembly of the NuRD complex, and increases the conformational flexibility of Arg-4, Lys-5 and Gln-6 of BCL11B. These alterations collectively reduce the affinity of BCL11B p.R3S for the RBBP4-MTA1 complex by nearly an order of magnitude. We generated a mouse model of the BCL11B p.R3S substitution using a CRISPR-Cas9-based approach, and we report herein that these mice exhibit craniosynostosis of the coronal suture, as well as other cranial sutures. This finding provides strong evidence that the BCL11B p.R3S substitution is causally associated with craniosynostosis and confirms an important role for BCL11B in the maintenance of cranial suture patency.

Selfish mutations dysregulating RAS-MAPK signaling are pervasive in aged human testes

Mosaic mutations present in the germline have important implications for reproductive risk and disease transmission. We previously demonstrated a phenomenon occurring in the male germline, whereby specific mutations arising spontaneously in stem cells (spermatogonia) lead to clonal expansion, resulting in elevated mutation levels in sperm over time. This process, termed "selfish spermatogonial selection," explains the high spontaneous birth prevalence and strong paternal age-effect of disorders such as achondroplasia and Apert, Noonan and Costello syndromes, with direct experimental evidence currently available for specific positions of six genes (FGFR2, FGFR3, RET, PTPN11, HRAS, and KRAS). We present a discovery screen to identify novel mutations and genes showing evidence of positive selection in the male germline, by performing massively parallel simplex PCR using RainDance technology to interrogate mutational hotspots in 67 genes (51.5 kb in total) in 276 biopsies of testes from five men (median age, 83 yr). Following ultradeep sequencing (about 16,000×), development of a low-frequency variant prioritization strategy, and targeted validation, we identified 61 distinct variants present at frequencies as low as 0.06%, including 54 variants not previously directly associated with selfish selection. The majority (80%) of variants identified have previously been implicated in developmental disorders and/or oncogenesis and include mutations in six newly associated genes (BRAF, CBL, MAP2K1, MAP2K2, RAF1, and SOS1), all of which encode components of the RAS-MAPK pathway and activate signaling. Our findings extend the link between mutations dysregulating the RAS-MAPK pathway and selfish selection, and show that the aging male germline is a repository for such deleterious mutations.

The adult human testis transcriptional cell atlas

Human adult spermatogenesis balances spermatogonial stem cell (SSC) self-renewal and differentiation, alongside complex germ cell-niche interactions, to ensure long-term fertility and faithful genome propagation. Here, we performed single-cell RNA sequencing of ~6500 testicular cells from young adults. We found five niche/somatic cell types (Leydig, myoid, Sertoli, endothelial, macrophage), and observed germline-niche interactions and key human-mouse differences. Spermatogenesis, including meiosis, was reconstructed computationally, revealing sequential coding, non-coding, and repeat-element transcriptional signatures. Interestingly, we identified five discrete transcriptional/developmental spermatogonial states, including a novel early SSC state, termed State 0. Epigenetic features and nascent transcription analyses suggested developmental plasticity within spermatogonial States. To understand the origin of State 0, we profiled testicular cells from infants, and identified distinct similarities between adult State 0 and infant SSCs. Overall, our datasets describe key transcriptional and epigenetic signatures of the normal adult human testis, and provide new insights into germ cell developmental transitions and plasticity.

Chromatin and Single-Cell RNA-Seq Profiling Reveal Dynamic Signaling and Metabolic Transitions during Human Spermatogonial Stem Cell Development

Human adult spermatogonial stem cells (hSSCs) must balance self-renewal and differentiation. To understand how this is achieved, we profiled DNA methylation and open chromatin (ATAC-seq) in SSEA4⁺ hSSCs, analyzed bulk and single-cell RNA transcriptomes (RNA-seq) in SSEA4⁺ hSSCs and differentiating c-KIT⁺ spermatogonia, and performed validation studies via immunofluorescence. First, DNA hypomethylation at embryonic developmental genes supports their epigenetic "poising" in hSSCs for future/embryonic expression, while core pluripotency genes (OCT4 and NANOG) were transcriptionally and epigenetically repressed. Interestingly, open chromatin in hSSCs was strikingly enriched in binding sites for pioneer factors (NFYA/B, DMRT1, and hormone receptors). Remarkably, single-cell RNA-seq clustering analysis identified four cellular/developmental states during hSSC differentiation, involving major transitions in cell-cycle and transcriptional regulators, splicing and signaling factors, and glucose/mitochondria regulators. Overall, our results outline the dynamic chromatin/transcription landscape operating in hSSCs and identify crucial molecular pathways that accompany the transition from quiescence to proliferation and differentiation.

Expression Levels of PIWI-interacting RNA, piR-823, Are Deregulated in Tumor Tissue, Blood Serum and Urine of Patients with Renal Cell Carcinoma

BACKGROUND

Renal cell carcinoma (RCC) is the most common neoplasm of adult kidney accounting for about 3% of adult malignancies. P-Element induced wimpy testis (PIWI)-interacting RNAs (piRNAs) are a new class of naturally occurring, short non-coding RNAs involved in silencing of transposable elements and in sequence-specific chromatin modifications. There were preliminary data published indicating that piR-823 expression is deregulated in circulating tumor cells and tumor tissue in gastric and kidney cancer, respectively.

PATIENTS AND METHODS

In our study, we analyzed piR-823 levels in 588 biological specimens: tumor tissue (N=153), adjacent renal parenchyma (N=121), blood serum (N=178) and urine (N=20) of patients undergoing nephrectomy for RCC; and in blood serum (N=101) and urine (N=15) of matched healthy controls. Expression levels of piR-823 were determined in all biological specimens by quantitative real-time polymerase chain reaction, compared in patients and controls, and correlated with clinicopathological features of RCC.

RESULTS

We identified a significant down-regulation of piR-823 in tumor tissue [p<0.0001, area under the curve (AUC)=0.7945]. On the contrary in blood serum and urine, the expression of piR-823 was significantly higher in patients with RCC compared to healthy individuals (p=0.0005, AUC=0.6264 and p=0.0157, AUC=0.7433, respectively). We further observed higher levels of piR-823 in tumor tissue to be associated with shorter disease-free survival of patients (p=0.0186) and a trend for higher piR-823 levels in serum to be associated with advanced clinical stages of RCC (p=0.0691). There were no other significant associations of piR-823 levels in any type of biological specimen with clinicopathological features of RCC.

CONCLUSION

piR-823 is down-regulated in tumor tissue, but positively correlated with worse outcome, indicating its complex role in RCC pathogenesis. In blood serum, piR-823 is up-regulated, but with unsatisfactory analytical performance. Preliminary data indicate the promising diagnostic utility of urinary piR-823 in patients with RCC.

Epithelial-mesenchymal transition-associated microRNA/mRNA signature is linked to metastasis and prognosis in clear-cell renal cell carcinoma

Clear-cell renal cell carcinomas (ccRCCs) are genetically heterogeneous tumors presenting diverse clinical courses. Epithelial-mesenchymal transition (EMT) is a crucial process involved in initiation of metastatic cascade. The aim of our study was to identify an integrated miRNA/mRNA signature associated with metastasis and prognosis in ccRCC through targeted approach based on analysis of miRNAs/mRNAs associated with EMT. A cohort of 230 ccRCC was included in our study and further divided into discovery, training and validation cohorts. EMT markers were evaluated in ccRCC tumor samples, which were grouped accordingly to EMT status. By use of large-scale miRNA/mRNA expression profiling, we identified miRNA/mRNA with significantly different expression in EMT-positive tumors and selected 41 miRNAs/mRNAs for training phase of the study to evaluate their diagnostic and prognostic potential. Fifteen miRNAs/mRNAs were analyzed in the validation phase, where all evaluated miRNA/mRNA candidates were confirmed to be significantly deregulated in tumor tissue. Some of them significantly differed in metastatic tumors, correlated with clinical stage, with Fuhrman grade and with overall survival. Further, we established an EMT-based stage-independent prognostic scoring system enabling identification of ccRCC patients at high-risk of cancer-related death. Finally, we confirmed involvement of miR-429 in EMT regulation in RCC cells in vitro.

Abstract 237: Piwi genes and tissue/serum piR-651 are related to clinicopathologic features of renal cell carcinoma

Introduction: Piwi-interacting RNAs (piRNAs) consists a newly discovered class of non-coding RNA. PiRNAs were first identified in the germ cells of various animal species. They bind to Piwi proteins which are a subfamily of Argonaut proteins. In humans were identified four Ago genes and four Piwi genes. Human Piwi genes include PIWIL1, PIWIL2, PIWIL3 and PIWIL4. Recent studies suggest that deregulated expression of Piwi proteins is common to many types of tumors and also correlate with clinicopathologic features and worse prognosis in patients with breast, cervical, ovarian, colorectal and other cancers. PiRNAs are short single-stranded RNAs with 26-31 nucleotides in length. They are involved in silencing of transposable elements and it is assumed that also participate in sequence-specific chromatin modifications. The differential expression of piRNAs was found in gastric and breast cancer. In our pilot study we analyzed expression of Piwi genes and piR-651, which was previously found to be deregulated in various types of tumors.

Patients and Methods: In our study, we have used the tumor tissue and the paired renal parenchyma tissue of 56 patients with renal cell carcinoma (RCC). From the tissue was isolated total RNA and by RT-qPCR were examined the expression of Piwi genes and piR-651. For the analysis of circulating piR-651, blood serum samples of 75 patients with RCC and 75 age, gender-matched healthy donors were used. We have compared expression levels of the studied genes in tumor and non-tumor tissues, serum samples, and also correlated them with clinicopathologic features of RCC patients (stage, grade, RFS, OS).

Results: We found a significant down-regulation of PIWIL1 (p&lt;0,0001) and piR-651 (p&lt;0,0001) expression levels in tumor tissue when compared to paired renal parenchyma samples. The expression levels of PIWIL2, PIWIL3 and PIWIL4 were not significantly deregulated in tumor tissue. Interestingly, levels of PIWIL2 and PIWIL4 correlated significantly with the stage (p = 0,002 and p = 0,003, resp.) and grade (p = 0.007 and p&lt;0.0001, resp.) of RCC. We found also a correlation between higher levels of PIWIL1 and overall survival (p&lt;0.05). We have observed significantly decreased expression levels of piR-651 in blood serum samples of RCC patients when compared to healthy donors and accordingly to ROC analysis we were able to distinguish blood serum of RCC patients and control subjects with the sensitivity of 77.33% and a specificity of 72.37%. Expression levels of serum piR-651 were not in correlation with the stage and grade of RCC.

Conclusion: Accordingly to our pilot data expression of Piwi genes is altered in tumor tissue and is correlated to selected clinicopathologic features of RCC. We also suggest the potential of piR-651 in blood serum as novel non-invasive diagnostic biomarker in RCC.

Acknowledgments: IGA MZCR No: NT/13860-4/2012, NT/13549-4/2012, NT/13547-4/2012, NT/13514-4/2012

Citation Format: Robert Iliev, Petra Vychytilova-Faltejskova, Jaroslav Juracek, Hana Mlcochova, Michal Stanik, Jan Dolezel, Michal Fedorko, Dalibor Pacik, Marek Svoboda, Ondrej Slaby. Piwi genes and tissue/serum piR-651 are related to clinicopathologic features of renal cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 237. doi:10.1158/1538-7445.AM2015-237

Abstract 5256: MiRNA-31-5p expression in glioblastoma tissue and effects of its replacement in glioblastoma cells

Introduction:

Glioblastoma multiforme (GBM) is the most malignant primary tumor of the central nervous system of adults. Our previous study has showed significant alterations in expression of microRNAs (miRNAs) in GBM tissue. Some of these miRNAs were also correlated with overall survival, whereas miR-31-5p was the most significant, indicating its tumor suppressive functioning. In this study, miR-31-5p was studied on larger cohort of GBM patients and also in vitro of selected GBM cell lines.

Patients, Cell lines and Methods:

Expression of miR-31-5p was validated on cohort of 58 GBM patients and 10 samples of non-tumor brain tissue. We have increased expression level of miR-31-5p using transient transfection of specific miRNA mimic in GBM cell lines A172, U87MG, T98MG, and U251. Cell viability and proliferation were analyzed using MTT assay and cell counting, respectively. Cell cycle analyses were performed by flow-cytometry using propidium iodide. Migration and invasion potential were measured by the wound healing assay and transwell invasion assay, respectively. Finally, potential targets of miR-31-5p were discovered using combination of bioinformatics algorithms for target prediction and GeneChip Human Gene 2.0 ST Array (Affymetrix) whole-genome expression profiling.

Results:

Down-regulation of miR-31-5p was successfully validated on cohort of 58 GBM patients and 10 samples of non-tumor brain tissue (p&lt;0.001). MiR-31-5p was significantly associated also with progression-free and overall survival of GBM patients. Transient expression of miR-31-5p led to the significant decrease of GBM cell proliferation and viability in A172, U87MG, T98G, and U251 cell lines (t-test; p &lt; 0.05) due to the cell cycle arrest in G1 phase. Moreover, transfected A172 and U251 cells had a lower migration and invasiveness potential in comparison with control cells (t-test; p &lt; 0.05). Finally, analysis of global gene expression profiles together with predicted mRNA targets revealed several interesting targets of miR-31-5p, which are involved in crucial signaling pathways of GBM.

Conclusion:

Taken together, our data suggest that miR-31-5p is not only powerful diagnostic marker as showed previously but seems to be promising therapeutic target in GBM patients. This work was supported by grants of Internal Grant Agency of the Czech Ministry of Health no. NT13514-4/2012, NT/13860-4/2012, NT/13549-4/2012, NT/13547-4/2012; and project “CEITEC - Central European Institute of Technology” (CZ.1.05/1.1.00/02.0068).

Citation Format: Jiri Sana, Andrej Besse, Jakub Ondracek, Marek Vecera, Pavel Fadrus, Leos Kren, Hana Mlcochova, Robert Illiev, Jitka Mlcochova, Petra Vychytilova, Renata Hezova, Jaroslav Juracek, Ondrej Slaby. MiRNA-31-5p expression in glioblastoma tissue and effects of its replacement in glioblastoma cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5256. doi:10.1158/1538-7445.AM2015-5256

Urinary microRNAs as a new class of noninvasive biomarkers in oncology, nephrology, and cardiology

MicroRNAs (miRNAs) are small noncoding RNAs that posttranscriptionally regulate gene expression. In the last decade, number of evidences showing miRNAs contribution to the regulation of apoptosis, cellular proliferation, differentiation, and other important cellular processes is constantly growing. Specific miRNA expression signatures have been identified in variety of human cancers as well as pathologies of cardiovascular and urinary systems. Our chapter focuses on the potential of urinary miRNAs to serve as biomarkers in uro-oncology, nephrology, and cardiology. We discuss in detail recent knowledge about the origin of urinary miRNAs, their stability, quality control, and their utility as a potential new class of biomarkers in medicine. Finally, we summarize the studies focusing on detection and characterization of urinary miRNAs as potential biomarkers in urologic cancers, nephrology, and cardiology.

Urine microRNAs as potential noninvasive biomarkers in urologic cancers

Micro-ribonucleic acids (miRNAs) are small noncoding RNAs that posttranscriptionally regulate gene expression. The ability of miRNAs to inhibit translation of oncogenes and tumor suppressors implies that they may be involved in carcinogenesis. Our review focuses on the potential of urinary miRNAs to serve as biomarkers of urologic cancers. We discuss in detail the recent knowledge about the origin of urinary miRNAs, their stability, quality control, and their utility as a potential new class of biomarkers in urologic cancer. Finally, we summarize the studies focusing on detection and characterization of urinary miRNAs as potential biomarkers in bladder, prostate, and kidney cancers.

Predicting term birth weight using ultrasound and maternal characteristics

OBJECTIVES

The aim of the study was to compare an ultrasound-based prediction formula of Shepard, Hadlock, our new equation and equation of Nahum based on maternal characteristics.

STUDY DESIGN

Two groups of 125 (group A) and 130 (group B) healthy term pregnant women were sampled. Standard ultrasonographic measurements were performed and maternal characteristics recorded. A new birth weight equation was developed by multiple stepwise regression analysis from the group A data and then compared to the different birth weight prediction equations of Hadlock, Shepard and Nahum on group B.

RESULTS

New prediction equation: log(10) EFW=0.64041xBPD-0.03257xBPD(2)+0.00154xACxFL. Our new (Halaska) and Hadlock's ultrasound estimations are comparable. Both equations are superior to Shepard and Nahum's equations. The Nahum equation is comparable to the Shepard estimation. Halaska equation tends to have the highest overall accuracy, Hadlock's estimation predicts better fetuses over 4000g, but this needs to be further validated.

CONCLUSIONS

The Halaska and Hadlock's estimations are comparable to one another; the Nahum equation is comparable to Shepard's and can be used as simple, inexpensive and approximative estimate.