Case Report: Application of whole exome sequencing for accurate diagnosis of rare syndromes of mineralocorticoid excess [version 2; referees: 2 approved]

Syndromes of mineralocorticoid excess (SME) are closely related clinical manifestations occurring within a specific set of diseases. Overlapping clinical manifestations of such syndromes often create a dilemma in accurate diagnosis, which is crucial for disease surveillance and management especially in rare genetic disorders. Here we demonstrate the use of whole exome sequencing (WES) for accurate diagnosis of rare SME and report that p.R337C variation in the HSD11B2 gene causes progressive apparent mineralocorticoid excess (AME) syndrome in a South Indian family of Mappila origin

Human 45,X fibroblast transcriptome reveals distinct differentially expressed genes including long noncoding RNAs potentially associated with the pathophysiology of Turner syndrome.

Turner syndrome is a chromosomal abnormality characterized by the absence of whole or part of the X chromosome in females. This X aneuploidy condition is associated with a diverse set of clinical phenotypes such as gonadal dysfunction, short stature, osteoporosis and Type II diabetes mellitus, among others. These phenotypes differ in their severity and penetrance among the affected individuals. Haploinsufficiency for a few X linked genes has been associated with some of these disease phenotypes. RNA sequencing can provide valuable insights to understand molecular mechanism of disease process. In the current study, we have analysed the transcriptome profiles of human untransformed 45,X and 46,XX fibroblast cells and identified differential expression of genes in these two karyotypes. Functional analysis revealed that these differentially expressing genes are associated with bone differentiation, glucose metabolism and gonadal development pathways. We also report differential expression of lincRNAs in X monosomic cells. Our observations provide a basis for evaluation of cellular and molecular mechanism(s) in the establishment of Turner syndrome phenotypes

Case Report: Whole exome sequencing reveals a novel frameshift deletion mutation p.G2254fs in COL7A1 associated with autosomal recessive dystrophic epidermolysis bullosa [version 2; referees: 2 approved, 1 approved with reservations]

Dystrophic epidermolysis bullosa simplex (DEB) is a phenotypically diverse inherited skin fragility disorder. It is majorly manifested by appearance of epidermal bullae upon friction caused either by physical or environmental trauma. The phenotypic manifestations also include appearance of milia, scarring all over the body and nail dystrophy. DEB can be inherited in a recessive or dominant form and the recessive form of DEB (RDEB) is more severe. In the present study, we identify a novel p.G2254fs mutation in COL7A1 gene causing a sporadic case of RDEB by whole exome sequencing (WES). Apart from adding a novel frameshift Collagen VII mutation to the repertoire of known mutations reported in the disease, to the best of our knowledge, this is the first report of a genetically characterized case of DEB from India

RNA secondary structure profiling in zebrafish reveals unique regulatory features

Abstract Background RNA is known to play diverse roles in gene regulation. The clues for this regulatory function of RNA are embedded in its ability to fold into intricate secondary and tertiary structure. Results We report the transcriptome-wide RNA secondary structure in zebrafish at single nucleotide resolution using Parallel Analysis of RNA Structure (PARS). This study provides the secondary structure map of zebrafish coding and non-coding RNAs. The single nucleotide pairing probabilities of 54,083 distinct transcripts in the zebrafish genome were documented. We identified RNA secondary structural features embedded in functional units of zebrafish mRNAs. Translation start and stop sites were demarcated by weak structural signals. The coding regions were characterized by the three-nucleotide periodicity of secondary structure and display a codon base specific structural constrain. The splice sites of transcripts were also delineated by distinct signature signals. Relatively higher structural signals were observed at 3’ Untranslated Regions (UTRs) compared to Coding DNA Sequence (CDS) and 5’ UTRs. The 3′ ends of transcripts were also marked by unique structure signals. Secondary structural signals in long non-coding RNAs were also explored to better understand their molecular function. Conclusions Our study presents the first PARS-enabled transcriptome-wide secondary structure map of zebrafish, which documents pairing probability of RNA at single nucleotide precision. Our findings open avenues for exploring structural features in zebrafish RNAs and their influence on gene expression

A genome-wide map of circular RNAs in adult zebrafish

Circular RNAs are a new addition to the growing list of diverse species of RNAs that are formed by covalent linked 3' and 5' end forming a closed loop structure. Circular RNAs are characteristically resistant to exonuclease treatment and are relatively stable to linear transcripts. Circular RNAs are formed by alternate splicing mechanism but do not follow the canonical order of exons. Backsplice junctions are unique to circRNAs.  CircRNAs are shown to possess potential to act as miRNA sponges and control transcription of mRNAs. CircRNAs are also reported as biomarkers for the disease like Alzheimer's, Parkinson's and cancer. A huge number of circRNA transcripts have been identified in model organisms including C.elegans, mouse, Drosophila as well as human. But there are no circular RNAs reported in zebrafish that is a very good model to study developmental stages, cardiovascular and blood-related disorders. In order to use zebrafish as a model organism and study the role of circRNAs in disease, we have used in-house generated RNA-sequencing data for five tissues including blood, brain, muscle, gills and heart. We discarded the reads mapped contiguously and full length over reference genome and identified back-splice junctions for putative circRNA transcripts. We identified a total of 3428 circRNA junctions out of which 78% were tissue specific. We validated 22 selected candidates for 5 tissues based on literature significance. We quantitatively analysed 5 tissue-enriched candidates using Real-time PCR. We also observed that major proportion of circRNAs is originating from protein coding loci. These circRNAs could be used to further study their role in hematopoietic and cardiovascular diseases

Case Report: Whole exome sequencing identifies a novel frameshift insertion c.1325dupT (p.F442fsX2) in the tyrosine kinase domain of BTK gene in a young Indian individual with X-linked agammaglobulinemia [version 2; referees: 2 approved]

X-linked agammaglobulinemia (XLA) is an extremely rare inherited primary immunodeficiency characterized by recurrent bacterial infections, decrease in number of mature B cells and low serum immunoglobulins. XLA is caused by mutations in the gene encoding Bruton's tyrosine kinase. We report a case of a young Indian boy suspected to have XLA. Immunophenotyping was performed for the affected child using CD20, CD19 and CD3 antibodies. Whole exome sequencing was performed using trio-based approach. The variants were further analyzed using capillary sequencing in the trio as well as maternal grandmother. Initial immunophenotyping in the affected child showed decreased count of CD19+ B cells. To strengthen the clinical findings and confirm the diagnosis of XLA, we performed whole exome sequencing. Our analysis identified a novel frameshift insertion (c.1325dupT) in the BTK gene, which was further validated by Sanger sequencing. Our approach shows the potential in using whole exome sequencing to pinpoint the molecular lesion, enabling timely diagnosis and genetic counseling, and potentially offering prenatal genetic testing for the family

Differentially expressed long non-coding RNAs in 45,X and 46,XX fibroblast cells at P value<0.001 and FDR (q) value<0.05.

<p>Differentially expressed long non-coding RNAs in 45,X and 46,XX fibroblast cells at P value<0.001 and FDR (q) value<0.05.</p

Heat Map depicting the expression levels 116 significantly differentially expressed genes in 45,X and 46,XX fibroblast cells.

<p>Heat Map depicting the expression levels 116 significantly differentially expressed genes in 45,X and 46,XX fibroblast cells.</p