Characteristic bimodal profiles of RNA polymerase II at thousands of active mammalian promoters.

BACKGROUND: In mammals, ChIP-seq studies of RNA polymerase II (PolII) occupancy have been performed to reveal how recruitment, initiation and pausing of PolII may control transcription rates, but the focus is rarely on obtaining finely resolved profiles that can portray the progression of PolII through sequential promoter states. RESULTS: Here, we analyze PolII binding profiles from high-coverage ChIP-seq on promoters of actively transcribed genes in mouse and humans. We show that the enrichment of PolII near transcription start sites exhibits a stereotypical bimodal structure, with one peak near active transcription start sites and a second peak 110 base pairs downstream from the first. Using an empirical model that reliably quantifies the spatial PolII signal, gene by gene, we show that the first PolII peak allows for refined positioning of transcription start sites, which is corroborated by mRNA sequencing. This bimodal signature is found both in mouse and humans. Analysis of the pausing-related factors NELF and DSIF suggests that the downstream peak reflects widespread pausing at the +1 nucleosome barrier. Several features of the bimodal pattern are correlated with sequence features such as CpG content and TATA boxes, as well as the histone mark H3K4me3. CONCLUSIONS: We thus show how high coverage DNA sequencing experiments can reveal as-yet unnoticed bimodal spatial features of PolII accumulation that are frequent at individual mammalian genes and reminiscent of transcription initiation and pausing. The initiation-pausing hypothesis is corroborated by evidence from run-on sequencing and immunoprecipitation in other cell types and species

Genetic Analysis of Consanguineous Pakistani Families with Congenital Stationary Night Blindness

Introduction: Congenital stationary night blindness (CSNB) is a rare, largely nonprogressive, inherited retinal disorder that can be clinically classified on the basis of fundus and electroretinogram abnormalities. Methods: We analyzed four large consanguineous families from the Southern Punjab region of Pakistan including multiple individuals affected with CSNB. Exome sequencing was performed in probands of all four families; Sanger sequencing was performed in additional members to test co-segregation of the variants identified. Results: We identified two novel and likely pathogenic variants in two pedigrees, namely, NM_002905.4:c.668A>C (p.Gln223Pro) in RDH5 and NM_022567.2:c.908del (p.Gly303ValfsTer45) in NYX. In the two other families, the variants NM_002905.4:c.319G>C (p.Gly107Arg) in RDH5 and NM_000541.5:c.874C>T (p.Arg292Ter) in SAG were identified. These latter mutations have been reported previously, but not in the Pakistani population. Conclusions: Our findings expand the mutational spectrum of CSNB, in particular within the population of Southern Punjab

Multiple myeloma presenting with external ear canal mass

The manifestations of multiple myeloma are protean and related to bony osteolytic lesions, and to medullar and renal insufficiency. We report a patient who presented with otalgia as the inaugural symptom of multiple myeloma. Local irradiation combined with systemic chemotherapy led to the disappearance of the temporal bone mass and the accompanying symptoms. To date, 24 months after the diagnosis, the patient is still in remission. The literature on otological involvement in multiple myeloma is reviewed. Symptoms are non-specific and include hearing loss, tinnitus, dizziness, facial paralysis, and otalgia. The diagnosis of multiple myeloma should be considered in the presence of a temporal bone mas

Exploring the Genetic Landscape of Retinal Diseases in North-Western Pakistan Reveals a High Degree of Autozygosity and a Prevalent Founder Mutation in ABCA4.

Variants in more than 271 different genes have been linked to hereditary retinal diseases, making comprehensive genomic approaches mandatory for accurate diagnosis. We explored the genetic landscape of retinal disorders in consanguineous families from North-Western Pakistan, harboring a population of approximately 35 million inhabitants that remains relatively isolated and highly inbred (~50% consanguinity). We leveraged on the high degree of consanguinity by applying genome-wide high-density single-nucleotide polymorphism (SNP) genotyping followed by targeted Sanger sequencing of candidate gene(s) lying inside autozygous intervals. In addition, we performed whole-exome sequencing (WES) on at least one proband per family. We identified 7 known and 4 novel variants in a total of 10 genes (ABCA4, BBS2, CNGA1, CNGA3, CNGB3, MKKS, NMNAT1, PDE6B, RPE65, and TULP1) previously known to cause inherited retinal diseases. In spite of all families being consanguineous, compound heterozygosity was detected in one family. All homozygous pathogenic variants resided in autozygous intervals ≥2.0 Mb in size. Putative founder variants were observed in the ABCA4 (NM_000350.2:c.214G>A; p.Gly72Arg; ten families) and NMNAT1 genes (NM_022787.3:c.25G>A; p.Val9Met; two families). We conclude that geographic isolation and sociocultural tradition of intrafamilial mating in North-Western Pakistan favor both the clinical manifestation of rare "generic" variants and the prevalence of founder mutations

Hydrodynamic stress in orbitally shaken bioreactors

Orbitally shaken bioreactors (OSRs) of nominal volume from 50 mL to 2’000 L have been developed for the cultivation of suspension-adapted mammalian cells. Here we study the hydrodynamics of OSRs for mammalian cells. The results are expected to allow the determination of key parameters for cell cultivation conditions and will facilitate the scale-up of OSRs

Numerical simulation of orbitally shaken viscous fluids with free surface

Orbitally shaken bioreactors are an emerging alternative to stirred-tank bioreactors for large-scale mam- malian cell culture, but their fluid dynamics is still not well defined. Among the theoretical and practical issues that remain to be resolved, the characterization of the liquid free surface during orbital shaking remains a major challenge because it is an essential aspect of gas transfer and mixing in these reactors. To simulate the fluid behavior and the free surface shape, we developed a numerical method based on the finite element framework. We found that the large density ratio between the liquid and the gas phases induced unphysical results for the free surface shape. We therefore devised a new pressure correction scheme to deal with large density ratios. The simulations operated with this new scheme gave values of wave amplitude similar to the ones mea- sured experimentally. These simulations were used to calculate the shear stress and to study the mixing principle in orbitally shaken bioreactorsPeer ReviewedPostprint (author’s final draft

The first genetic landscape of inherited retinal dystrophies in Portuguese patients identifies recurrent homozygous mutations as a frequent cause of pathogenesis.

Inherited retinal diseases (IRDs) are a group of ocular conditions characterized by an elevated genetic and clinical heterogeneity. They are transmitted almost invariantly as monogenic traits. However, with more than 280 disease genes identified so far, association of clinical phenotypes with genotypes can be very challenging, and molecular diagnosis is essential for genetic counseling and correct management of the disease. In addition, the prevalence and the assortment of IRD mutations are often population-specific. In this work, we examined 230 families from Portugal, with individuals suffering from a variety of IRD diagnostic classes (270 subjects in total). Overall, we identified 157 unique mutations (34 previously unreported) in 57 distinct genes, with a diagnostic rate of 76%. The IRD mutational landscape was, to some extent, different from those reported in other European populations, including Spanish cohorts. For instance, the EYS gene appeared to be the most frequently mutated, with a prevalence of 10% among all IRD cases. This was, in part, due to the presence of a recurrent and seemingly founder mutation involving the deletion of exons 13 and 14 of this gene. Moreover, our analysis highlighted that as many as 51% of our cases had mutations in a homozygous state. To our knowledge, this is the first study assessing a cross-sectional genotype-phenotype landscape of IRDs in Portugal. Our data reveal a rather unique distribution of mutations, possibly shaped by a small number of rare ancestral events that have now become prevalent alleles in patients

AutoMap is a high performance homozygosity mapping tool using next-generation sequencing data.

Homozygosity mapping is a powerful method for identifying mutations in patients with recessive conditions, especially in consanguineous families or isolated populations. Historically, it has been used in conjunction with genotypes from highly polymorphic markers, such as DNA microsatellites or common SNPs. Traditional software performs rather poorly with data from Whole Exome Sequencing (WES) and Whole Genome Sequencing (WGS), which are now extensively used in medical genetics. We develop AutoMap, a tool that is both web-based or downloadable, to allow performing homozygosity mapping directly on VCF (Variant Call Format) calls from WES or WGS projects. Following a training step on WES data from 26 consanguineous families and a validation procedure on a matched cohort, our method shows higher overall performances when compared with eight existing tools. Most importantly, when tested on real cases with negative molecular diagnosis from an internal set, AutoMap detects three gene-disease and multiple variant-disease associations that were previously unrecognized, projecting clear benefits for both molecular diagnosis and research activities in medical genetics

Higher-Order Inter-chromosomal Hubs Shape 3D Genome Organization in the Nucleus

Eukaryotic genomes are packaged into a 3-dimensional structure in the nucleus. Current methods for studying genome-wide structure are based on proximity ligation. However, this approach can fail to detect known structures, such as interactions with nuclear bodies, because these DNA regions can be too far apart to directly ligate. Accordingly, our overall understanding of genome organization remains incomplete. Here, we develop split-pool recognition of interactions by tag extension (SPRITE), a method that enables genome-wide detection of higher-order interactions within the nucleus. Using SPRITE, we recapitulate known structures identified by proximity ligation and identify additional interactions occurring across larger distances, including two hubs of inter-chromosomal interactions that are arranged around the nucleolus and nuclear speckles. We show that a substantial fraction of the genome exhibits preferential organization relative to these nuclear bodies. Our results generate a global model whereby nuclear bodies act as inter-chromosomal hubs that shape the overall packaging of DNA in the nucleus

SARS-CoV-2 disrupts splicing, translation, and protein trafficking to suppress host defenses

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a recently identified coronavirus that causes the respiratory disease known as coronavirus disease 2019 (COVID-19). Despite the urgent need, we still do not fully understand the molecular basis of SARS-CoV-2 pathogenesis. Here, we comprehensively define the interactions between SARS-CoV-2 proteins and human RNAs. NSP16 binds to the mRNA recognition domains of the U1 and U2 splicing RNAs and acts to suppress global mRNA splicing upon SARS-CoV-2 infection. NSP1 binds to 18S ribosomal RNA in the mRNA entry channel of the ribosome and leads to global inhibition of mRNA translation upon infection. Finally, NSP8 and NSP9 bind to the 7SL RNA in the signal recognition particle and interfere with protein trafficking to the cell membrane upon infection. Disruption of each of these essential cellular functions acts to suppress the interferon response to viral infection. Our results uncover a multipronged strategy utilized by SARS-CoV-2 to antagonize essential cellular processes to suppress host defenses