High-volume hybridoma sequencing on the NeuroMabSeq platform enables efficient generation of recombinant monoclonal antibodies and scFvs for neuroscience research

The Neuroscience Monoclonal Antibody Sequencing Initiative (NeuroMabSeq) is a concerted effort to determine and make publicly available hybridoma-derived sequences of monoclonal antibodies (mAbs) valuable to neuroscience research. Over 30 years of research and development efforts including those at the UC Davis/NIH NeuroMab Facility have resulted in the generation of a large collection of mouse mAbs validated for neuroscience research. To enhance dissemination and increase the utility of this valuable resource, we applied a high-throughput DNA sequencing approach to determine immunoglobulin heavy and light chain variable domain sequences from source hybridoma cells. The resultant set of sequences was made publicly available as a searchable DNA sequence database (neuromabseq.ucdavis.edu) for sharing, analysis and use in downstream applications. We enhanced the utility, transparency, and reproducibility of the existing mAb collection by using these sequences to develop recombinant mAbs. This enabled their subsequent engineering into alternate forms with distinct utility, including alternate modes of detection in multiplexed labeling, and as miniaturized single chain variable fragments or scFvs. The NeuroMabSeq website and database and the corresponding recombinant antibody collection together serve as a public DNA sequence repository of mouse mAb heavy and light chain variable domain sequences and as an open resource for enhancing dissemination and utility of this valuable collection of validated mAbs.

Long wavelength-sensing cones of zebrafish retina exhibit multiple layers of transcriptional heterogeneity

Introduction

Understanding how photoreceptor genes are regulated is important for investigating retinal development and disease. While much is known about gene regulation in cones, the mechanism by which tandemly-replicated opsins, such as human long wavelength-sensitive and middle wavelength-sensitive opsins, are differentially regulated remains elusive. In this study, we aimed to further our understanding of transcriptional heterogeneity in cones that express tandemly-replicated opsins and the regulation of such differential expression using zebrafish, which express the tandemly-replicated opsins lws1 and lws2.

Methods

We performed bulk and single cell RNA-Seq of LWS1 and LWS2 cones, evaluated expression patterns of selected genes of interest using multiplex fluorescence in situ hybridization, and used exogenous thyroid hormone (TH) treatments to test selected genes for potential control by thyroid hormone: a potent, endogenous regulator of lws1 and lws2 expression.

Results

Our studies indicate that additional transcriptional differences beyond opsin expression exist between LWS1 and LWS2 cones. Bulk RNA-Seq results showed 95 transcripts enriched in LWS1 cones and 186 transcripts enriched in LWS2 cones (FC > 2, FDR < 0.05). In situ hybridization results also reveal underlying heterogeneity within the lws1- and lws2-expressing populations. This heterogeneity is evident in cones of mature zebrafish, and further heterogeneity is revealed in transcriptional responses to TH treatments.

Discussion

We found some evidence of coordinate regulation of lws opsins and other genes by exogenous TH in LWS1 vs. LWS2 cones, as well as evidence of gene regulation not mediated by TH. The transcriptional differences between LWS1 and LWS2 cones are likely controlled by multiple signals, including TH.

NeuroMabSeq: high volume acquisition, processing, and curation of hybridoma sequences and their use in generating recombinant monoclonal antibodies and scFvs for neuroscience research

The Neuroscience Monoclonal Antibody Sequencing Initiative (NeuroMabSeq) is a concerted effort to determine and make publicly available hybridoma-derived sequences of monoclonal antibodies (mAbs) valuable to neuroscience research. Over 30 years of research and development efforts including those at the UC Davis/NIH NeuroMab Facility have resulted in the generation of a large collection of mouse mAbs validated for neuroscience research. To enhance dissemination and increase the utility of this valuable resource, we applied a high-throughput DNA sequencing approach to determine immunoglobulin heavy and light chain variable domain sequences from source hybridoma cells. The resultant set of sequences was made publicly available as searchable DNA sequence database ( neuromabseq.ucdavis.edu ) for sharing, analysis and use in downstream applications. We enhanced the utility, transparency, and reproducibility of the existing mAb collection by using these sequences to develop recombinant mAbs. This enabled their subsequent engineering into alternate forms with distinct utility, including alternate modes of detection in multiplexed labeling, and as miniaturized single chain variable fragments or scFvs. The NeuroMabSeq website and database and the corresponding recombinant antibody collection together serve as a public DNA sequence repository of mouse mAb heavy and light chain variable domain sequences and as an open resource for enhancing dissemination and utility of this valuable collection of validated mAbs.

Sex disparate gut microbiome and metabolome perturbations precede disease progression in a mouse model of Rett syndrome

Rett syndrome (RTT) is a regressive neurodevelopmental disorder in girls, characterized by multisystem complications including gut dysbiosis and altered metabolism. While RTT is known to be caused by mutations in the X-linked gene MECP2, the intermediate molecular pathways of progressive disease phenotypes are unknown. Mecp2 deficient rodents used to model RTT pathophysiology in most prior studies have been male. Thus, we utilized a patient-relevant mouse model of RTT to longitudinally profile the gut microbiome and metabolome across disease progression in both sexes. Fecal metabolites were altered in Mecp2e1 mutant females before onset of neuromotor phenotypes and correlated with lipid deficiencies in brain, results not observed in males. Females also displayed altered gut microbial communities and an inflammatory profile that were more consistent with RTT patients than males. These findings identify new molecular pathways of RTT disease progression and demonstrate the relevance of further study in female Mecp2 animal models.

Establishment of quantitative RNAi-based forward genetics in Entamoeba histolytica and identification of genes required for growth

While Entamoeba histolytica remains a globally important pathogen, it is dramatically understudied. The tractability of E. histolytica has historically been limited, which is largely due to challenging features of its genome. To enable forward genetics, we constructed and validated the first genome-wide E. histolytica RNAi knockdown mutant library. This library allows for Illumina deep sequencing analysis for quantitative identification of mutants that are enriched or depleted after selection. We developed a novel analysis pipeline to precisely define and quantify gene fragments. We used the library to perform the first RNAi screen in E. histolytica and identified slow growth (SG) mutants. Among genes targeted in SG mutants, many had annotated functions consistent with roles in cellular growth or metabolic pathways. Some targeted genes were annotated as hypothetical or lacked annotated domains, supporting the power of forward genetics in uncovering functional information that cannot be gleaned from databases. While the localization of neither of the proteins targeted in SG1 nor SG2 mutants could be predicted by sequence analysis, we showed experimentally that SG1 localized to the cytoplasm and cell surface, while SG2 localized to the cytoplasm. Overexpression of SG1 led to increased growth, while expression of a truncation mutant did not lead to increased growth, and thus aided in defining functional domains in this protein. Finally, in addition to establishing forward genetics, we uncovered new details of the unusual E. histolytica RNAi pathway. These studies dramatically improve the tractability of E. histolytica and open up the possibility of applying genetics to improve understanding of this important pathogen.

Biosolids as a Source of Antibiotic Resistance Plasmids for Commensal and Pathogenic Bacteria

Antibiotic resistance (AR) is a threat to modern medicine, and plasmids are driving the global spread of AR by horizontal gene transfer across microbiomes and environments. Determining the mobile resistome responsible for this spread of AR among environments is essential in our efforts to attenuate the current crisis. Biosolids are a wastewater treatment plant (WWTP) byproduct used globally as fertilizer in agriculture. Here, we investigated the mobile resistome of biosolids that are used as fertilizer. This was done by capturing resistance plasmids that can transfer to human pathogens and commensal bacteria. We used a higher-throughput version of the exogenous plasmid isolation approach by mixing several ESKAPE pathogens and a commensal Escherichia coli with biosolids and screening for newly acquired resistance to about 10 antibiotics in these strains. Six unique resistance plasmids transferred to Salmonella typhimurium, Klebsiella aerogenes, and E. coli. All the plasmids were self-transferable and carried 3-6 antibiotic resistance genes (ARG) conferring resistance to 2-4 antibiotic classes. These plasmids-borne resistance genes were further embedded in genetic elements promoting intracellular recombination (i.e., transposons or class 1 integrons). The plasmids belonged to the broad-host-range plasmid (BHR) groups IncP-1 or PromA. Several of them were persistent in their new hosts when grown in the absence of antibiotics, suggesting that the newly acquired drug resistance traits would be sustained over time. This study highlights the role of BHRs in the spread of ARG between environmental bacteria and human pathogens and commensals, where they may persist. The work further emphasizes biosolids as potential vehicles of highly mobile plasmid-borne antibiotic resistance genes.

The Species-Specific Acquisition and Diversification of a K1-like Family of Killer Toxins in Budding Yeasts of the Saccharomycotina

Killer toxins are extracellular antifungal proteins that are produced by a wide variety of fungi, including Saccharomyces yeasts. Although many Saccharomyces killer toxins have been previously identified, their evolutionary origins remain uncertain given that many of these genes have been mobilized by double-stranded RNA (dsRNA) viruses. A survey of yeasts from the Saccharomyces genus has identified a novel killer toxin with a unique spectrum of activity produced by Saccharomyces paradoxus. The expression of this killer toxin is associated with the presence of a dsRNA totivirus and a satellite dsRNA. Genetic sequencing of the satellite dsRNA confirmed that it encodes a killer toxin with homology to the canonical ionophoric K1 toxin from Saccharomyces cerevisiae and has been named K1-like (K1L). Genomic homologs of K1L were identified in six non-Saccharomyces yeast species of the Saccharomycotina subphylum, predominantly in subtelomeric regions of the genome. When ectopically expressed in S. cerevisiae from cloned cDNAs, both K1L and its homologs can inhibit the growth of competing yeast species, confirming the discovery of a family of biologically active K1-like killer toxins. The sporadic distribution of these genes supports their acquisition by horizontal gene transfer followed by diversification. The phylogenetic relationship between K1L and its genomic homologs suggests a common ancestry and gene flow via dsRNAs and DNAs across taxonomic divisions. This appears to enable the acquisition of a diverse arsenal of killer toxins by different yeast species for potential use in niche competition.

Diversification, Introgression, and Rampant Cytonuclear Discordance in Rocky Mountains Chipmunks (Sciuridae: Tamias)

Evidence from natural systems suggests that hybridization between animal species is more common than traditionally thought, but the overall contribution of introgression to standing genetic variation within species remains unclear for most animal systems. Here, we use targeted exon-capture to sequence thousands of nuclear loci and complete mitochondrial genomes from closely related chipmunk species in the Tamias quadrivittatus group that are distributed across the Great Basin and the central and southern Rocky Mountains of North America. This recent radiation includes six overlapping, ecologically distinct species (T. canipes, T. cinereicollis, T. dorsalis, T. quadrivittatus, T. rufus, and T. umbrinus) that show evidence for widespread introgression across species boundaries. Such evidence has historically been derived from a handful of markers, typically focused on mitochondrial loci, to describe patterns of introgression; consequently, the extent of introgression of nuclear genes is less well characterized. We conducted a series of phylogenomic and species-tree analyses to resolve the phylogeny of six species in this group. In addition, we performed several population genomic analyses to characterize nuclear genomes and infer coancestry among individuals. Furthermore, we used emerging quartets-based approaches to simultaneously infer the species tree (SVDquartets) and identify introgression (HyDe). We found that, in spite of rampant introgression of mitochondrial genomes between some species pairs (and sometimes involving up to three species), there appears to be little to no evidence for nuclear introgression. These findings mirror other genomic results where complete mitochondrial capture has occurred between chipmunk species in the absence of appreciable nuclear gene flow. The underlying causes of recurrent massive cytonuclear discordance remain unresolved in this group but mitochondrial DNA appears highly misleading of population histories as a whole. Collectively, it appears that chipmunk species boundaries are largely impermeable to nuclear gene flow and that hybridization, while pervasive with respect to mtDNA, has likely played a relatively minor role in the evolutionary history of this group.

Wireworm (Coleoptera: Elateridae) genomic analysis reveals putative cryptic species, population structure, and adaptation to pest control

The larvae of click beetles (Coleoptera: Elateridae), known as "wireworms," are agricultural pests that pose a substantial economic threat worldwide. We produced one of the first wireworm genome assemblies (Limonius californicus), and investigated population structure and phylogenetic relationships of three species (L. californicus, L. infuscatus, L. canus) across the northwest US and southwest Canada using genome-wide markers (RADseq) and genome skimming. We found two species (L. californicus and L. infuscatus) are comprised of multiple genetically distinct groups that diverged in the Pleistocene but have no known distinguishing morphological characters, and therefore could be considered cryptic species complexes. We also found within-species population structure across relatively short geographic distances. Genome scans for selection provided preliminary evidence for signatures of adaptation associated with different pesticide treatments in an agricultural field trial for L. canus. We demonstrate that genomic tools can be a strong asset in developing effective wireworm control strategies.

Regeneration associated transcriptional signature of retinal microglia and macrophages

Zebrafish have the remarkable capacity to regenerate retinal neurons following a variety of damage paradigms. Following initial tissue insult and a period of cell death, a proliferative phase ensues that generates neuronal progenitors, which ultimately regenerate damaged neurons. Recent work has revealed that Müller glia are the source of regenerated neurons in zebrafish. However, the roles of another important class of glia present in the retina, microglia, during this regenerative phase remain elusive. Here, we examine retinal tissue and perform QuantSeq. 3'mRNA sequencing/transcriptome analysis to reveal localization and putative functions, respectively, of mpeg1 expressing cells (microglia/macrophages) during Müller glia-mediated regeneration, corresponding to a time of progenitor proliferation and production of new neurons. Our results indicate that in this regenerative state, mpeg1-expressing cells are located in regions containing regenerative Müller glia and are likely engaged in active vesicle trafficking. Further, mpeg1+ cells congregate at and around the optic nerve head. Our transcriptome analysis reveals several novel genes not previously described in microglia. This dataset represents the first report, to our knowledge, to use RNA sequencing to probe the microglial transcriptome in such context, and therefore provides a resource towards understanding microglia/macrophage function during successful retinal (and central nervous tissue) regeneration.

A Rapid Method for Sequencing Double-Stranded RNAs Purified from Yeasts and the Identification of a Potent K1 Killer Toxin Isolated from Saccharomyces cerevisiae

Mycoviruses infect a large number of diverse fungal species, but considering their prevalence, relatively few high-quality genome sequences have been determined. Many mycoviruses have linear double-stranded RNA genomes, which makes it technically challenging to ascertain their nucleotide sequence using conventional sequencing methods. Different specialist methodologies have been developed for the extraction of double-stranded RNAs from fungi and the subsequent synthesis of cDNAs for cloning and sequencing. However, these methods are often labor-intensive, time-consuming, and can require several days to produce cDNAs from double-stranded RNAs. Here, we describe a comprehensive method for the rapid extraction and sequencing of dsRNAs derived from yeasts, using short-read next generation sequencing. This method optimizes the extraction of high-quality double-stranded RNAs from yeasts and 3′ polyadenylation for the initiation of cDNA synthesis for next-generation sequencing. We have used this method to determine the sequence of two mycoviruses and a double-stranded RNA satellite present within a single strain of the model yeast Saccharomyces cerevisiae. The quality and depth of coverage was sufficient to detect fixed and polymorphic mutations within viral populations extracted from a clonal yeast population. This method was also able to identify two fixed mutations within the alpha-domain of a variant K1 killer toxin encoded on a satellite double-stranded RNA. Relative to the canonical K1 toxin, these newly reported mutations increased the cytotoxicity of the K1 toxin against a specific species of yeast.

Comparative Phylogenomic Assessment of Mitochondrial Introgression among Several Species of Chipmunks (Tamias)

Many species are not completely reproductively isolated, resulting in hybridization and genetic introgression. Organellar genomes, such as those derived from mitochondria (mtDNA) and chloroplasts, introgress frequently in natural systems; however, the forces shaping patterns of introgression are not always clear. Here, we investigate extensive mtDNA introgression in western chipmunks, focusing on species in the Tamias quadrivittatus group from the central and southern Rocky Mountains. Specifically, we investigate the role of selection in driving patterns of introgression. We sequenced 51 mtDNA genomes from six species and combine these sequences with other published genomic data to yield annotated mitochondrial reference genomes for nine species of chipmunks. Genomic characterization was performed using a series of molecular evolutionary and phylogenetic analyses to test protein-coding genes for positive selection. We fit a series of maximum likelihood models using a model-averaging approach, assessed deviations from neutral expectations, and performed additional tests to search for codons under the influence of selection. We found no evidence for positive selection among these genomes, suggesting that selection has not been the driving force of introgression in these species. Thus, extensive mtDNA introgression among several species of chipmunks likely reflects genetic drift of introgressed alleles in historically fluctuating populations.

Abstract 562: Oncovirus detection and integration analysis from human tumor samples using targeted massively parallel sequencing

Viruses are a major contributor to oncogenesis, causing 10-15% of human cancers. Molecular pathways involved in malignant transformation are frequently activated by genetic alterations, including but not limited to, somatic mutations, copy number aberrations, structural variants, and oncoviruses. Precision cancer medicine aims to classify tumors by site, histology, and molecular tests to determine an “individualized” profile of cancer alterations. However, clinical tests for these various alterations are sequential, time consuming, and use a lot of material, which is often quite limited (e.g., biopsies). Moreover, tests for the presence of viral sequence are generally performed separately to tests (such as massively parallel sequencing) to detect human genomic alterations. Here we present a hybrid capture and massively parallel sequencing approach to detect viral infection concurrently with targeted genomic analysis, which may decrease assay costs, increase sensitivity and scalability, and detect many types of alterations, thereby providing a more complete tumor genetic profile all from a single sample.

We have created a custom hybrid capture probeset for targeted Illumina sequencing to determine whether oncoviruses are present in tissue samples and also determine if the virus has integrated into the host’s genome. We have created both ‘detection’ and ‘integration’ baits for several oncoviruses, including polyomaviruses, human papilloma viruses, Epstein-Barr virus, human cytomegalovirus, Kaposi sarcoma herpesvirus, human T-lymphotropic virus, and hepatitis B virus. To distinguish between different strains of a single virus, strain-specific detection baits were created to bind to variable regions of viral genomes. The integration bait was designed to bind to regions of the viral genomes that are commonly integrated into the human genome. This baitset can also be combined with other capture panels targeting oncogenes to simultaneously determine infection and integration statuses, as well as somatic mutations, copy number and structural variants.

To detect virus presence, reads were aligned to a hybrid reference of both the human, and targeted virus genomes. Viral integration status and integration loci were determined by leveraging discordant read pairs that aligned to both the human genome and a viral genome. We have tested our techniques on tissue samples that were infected with either Merkel Cell Polyomavirus or Epstein-Barr virus, as determined using quantitative polymerase chain reaction (qPCR) or immunohistochemistry (IHC) techniques, and have successfully detected these viruses and identified viral integration loci. Overall, this viral hybrid capture probeset provides the ability to simultaneously determine a tissue sample’s infection and viral integration status alongside other somatic genomic analyses, saving both time and sample material.

Citation Format: Robert T. Burns, Samuel S. Hunter, Matthew D. Ducar, Aaron R. Thorner, James A. Decaprio, Paul Van Hummelen, Alexander Frieden, Anwesha Nag, Haley A. Coleman, Michael K. Slevin, Andrea Clapp, Samantha D. Drinan, Suzanne R. McShane, Edwin Thai, Priyanka Shivdasani, Joshua Bohannon, Johann Hoeftberger, Reuben Jacobs, Bruce M. Wollison, Neil A. Patel, Monica D. Manam, Phani Davineni, Matthew Meyerson, Laura E. MacConaill. Oncovirus detection and integration analysis from human tumor samples using targeted massively parallel sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 562. doi:10.1158/1538-7445.AM2017-562

Abstract 3644: Optimization of library construction for massively parallel sequencing using low-input, FFPE-derived DNA without additional PCR amplification

Massively parallel sequencing (MPS) is increasingly used in the laboratory and clinic to identify genomic factors contributing to tumorigenesis, such as somatic mutations, DNA insertions and deletions, transcriptome and epigenetic changes, and chromosomal abnormalities. Because tumor specimens are often quite limited or are from rare and precious samples, it is necessary to prepare sequencing libraries from minimal amounts of DNA. Indeed, it can be challenging to extract sufficient amounts of starting material from fresh-frozen paraffin embedded (FFPE) samples for library construction, and frequently samples are not processed because they do not reach minimum requirements. Therefore, it is of great importance to improve currently available protocols to process low yield FFPE-derived DNA for MPS. This will allow for the inclusion of more tumor samples to be sequenced per cohort, resulting in increased ability to identify genomic factors involved in tumorigenesis.

Here, we optimized the KAPA Library Preparation Kit (Kapa Biosystems, Wilmington, MA) to successfully perform library construction from low-yield FFPE and fresh frozen samples. The kit normally requires an input of at least 100 ng of DNA. However, we were able to modify the protocol to prepare libraries from as little as 10 ng of starting material by optimizing the ratio of adapter:input DNA and SPRI-clean-up, performing low-volume reactions, and using IDT universal blockers during hybrid capture. Additional library enrichment PCR was not required. Library yields were sufficient for downstream hybrid capture and sequencing, and sequencing metrics were comparable to samples that were prepped using the manufacturer's recommendations. Experiments are underway to demonstrate that library complexity remains unchanged.

Citation Format: Aaron R. Thorner, Liuda Ziaugra, Matthew D. Ducar, Ling Lin, Angelica Laing, Haley A. Coleman, Suzanne R. McShane, Andrea Clapp, Rachel R. Paquette, Bruce M. Wollison, Johann Hoeftberger, Neil A. Patel, Samuel S. Hunter, Monica D. Manam, Laura E. MacConaill, William C. Hahn, Matthew L. Meyerson, Paul van Hummelen. Optimization of library construction for massively parallel sequencing using low-input, FFPE-derived DNA without additional PCR amplification. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3644.

Evolutionary Paths That Expand Plasmid Host-Range: Implications for Spread of Antibiotic Resistance

The World Health Organization has declared the emergence of antibiotic resistance to be a global threat to human health. Broad-host-range plasmids have a key role in causing this health crisis because they transfer multiple resistance genes to a wide range of bacteria. To limit the spread of antibiotic resistance, we need to gain insight into the mechanisms by which the host range of plasmids evolves. Although initially unstable plasmids have been shown to improve their persistence through evolution of the plasmid, the host, or both, the means by which this occurs are poorly understood. Here, we sought to identify the underlying genetic basis of expanded plasmid host-range and increased persistence of an antibiotic resistance plasmid using a combined experimental-modeling approach that included whole-genome resequencing, molecular genetics and a plasmid population dynamics model. In nine of the ten previously evolved clones, changes in host and plasmid each slightly improved plasmid persistence, but their combination resulted in a much larger improvement, which indicated positive epistasis. The only genetic change in the plasmid was the acquisition of a transposable element from a plasmid native to the Pseudomonas host used in these studies. The analysis of genetic deletions showed that the critical genes on this transposon encode a putative toxin-antitoxin (TA) and a cointegrate resolution system. As evolved plasmids were able to persist longer in multiple naïve hosts, acquisition of this transposon also expanded the plasmid's host range, which has important implications for the spread of antibiotic resistance.

The population genomics of rapid adaptation: disentangling signatures of selection and demography in white sands lizards

Understanding the process of adaptation during rapid environmental change remains one of the central focal points of evolutionary biology. The recently formed White Sands system of southern New Mexico offers an outstanding example of rapid adaptation, with a variety of species having rapidly evolved blanched forms on the dunes that contrast with their close relatives in the surrounding dark soil habitat. In this study, we focus on two of the White Sands lizard species, Sceloporus cowlesi and Aspidoscelis inornata, for which previous research has linked mutations in the melanocortin-1 receptor gene (Mc1r) to blanched coloration. We sampled populations both on and off the dunes and used a custom sequence capture assay based on probed fosmid libraries to obtain >50 kb of sequence around Mc1r and hundreds of other random genomic locations. We then used model-based statistical inference methods to describe the demographic and adaptive history characterizing the colonization of White Sands. We identified a number of similarities between the two focal species, including strong evidence of selection in the blanched populations in the Mc1r region. We also found important differences between the species, suggesting different colonization times, different genetic architecture underlying the blanched phenotype and different ages of the beneficial alleles. Finally, the beneficial allele is dominant in S. cowlesi and recessive in A. inornata, allowing for a rare empirical test of theoretically expected patterns of selective sweeps under these differing models.

Retinoic Acid Signaling Regulates Differential Expression of the Tandemly-Duplicated Long Wavelength-Sensitive Cone Opsin Genes in Zebrafish

The signaling molecule retinoic acid (RA) regulates rod and cone photoreceptor fate, differentiation, and survival. Here we elucidate the role of RA in differential regulation of the tandemly-duplicated long wavelength-sensitive (LWS) cone opsin genes. Zebrafish embryos were treated with RA from 48 hours post-fertilization (hpf) to 75 hpf, and RNA was isolated from eyes for microarray analysis. ~170 genes showed significantly altered expression, including several transcription factors and components of cellular signaling pathways. Of interest, the LWS1 opsin gene was strongly upregulated by RA. LWS1 is the upstream member of the tandemly duplicated LWS opsin array and is normally not expressed embryonically. Embryos treated with RA 48 hpf to 100 hpf or beyond showed significant reductions in LWS2-expressing cones in favor of LWS1-expressing cones. The LWS reporter line, LWS-PAC(H) provided evidence that individual LWS cones switched from LWS2 to LWS1 expression in response to RA. The RA signaling reporter line, RARE:YFP indicated that increased RA signaling in cones was associated with this opsin switch, and experimental reduction of RA signaling in larvae at the normal time of onset of LWS1 expression significantly inhibited LWS1 expression. A role for endogenous RA signaling in regulating differential expression of the LWS genes in postmitotic cones was further supported by the presence of an RA signaling domain in ventral retina of juvenile zebrafish that coincided with a ventral zone of LWS1 expression. This is the first evidence that an extracellular signal may regulate differential expression of opsin genes in a tandemly duplicated array.

Abstract 4867: Comparative analysis of RNA sequencing methods for characterization of cancer transcriptomics

RNA sequencing (RNASeq) provides the ability to comprehensively assay the transcriptome in a high-throughput manner. Current there are a variety of library preparation methodologies for measuring and sequencing the transcriptome depending on (a) the sample source and (b) outcomes of interest. Beyond protocol selection, the requisite computational tools and resources are significant considerations in processing, analyzing and reporting the experimental results. While there are many resources readily available to effectively perform RNA-seq experiments, optimal protocols and analysis tools for the cancer domain remain to be developed.

We have developed and characterized a set of protocols and analysis procedures that comprise an RNA-seq pipeline that can effectively be used in a cancer research setting. The analysis pipeline consists of a sequence of functions and tools to process and clean the raw data, generate quality control and summary metrics, and perform secondary analyses that include expression quantification, fusion detection and somatic mutation calling. We applied this pipeline to three different RNAseq strategies (whole-transcriptome, exome, and targeted RNA-seq) and performed an in-depth comparative analysis to investigate the implications of the choice of strategy on the downstream analysis and results. More specifically, we investigated the impact of library preparation methods on the dynamic range and expression profiles, variant calling and fusion detection. While the data indicated that capture-based protocols provided efficient methods for sampling transcripts as compared to whole-transcriptome RNA-seq, there are considerations in its use, particularly for duplicate reads and uncaptured transcripts. We illustrate the implications of these issues on downstream analysis, such as somatic mutation and fusion calling and differential expression.

In summary, we have described a RNA-seq analysis platform that provides a varied set of library preparations and analytical components for large-scale clinical or research transcriptomics. Our analysis has characterized the technical features of the different library preparations, providing a necessary understanding of the costs and benefits of each method and the potential effects on the downstream analyses.

Citation Format: Ryan P. Abo, Ling Lin, Samuel S. Hunter, Deniz N. Dolcen, Rachel R. Paquette, Angelica Laing, Luc de Waal, Aaron R. Thorner, Matthew D. Ducar, Liuda Ziaugra, William C. Hahn, Matthew L. Meyerson, Laura E. MacConaill, Paul Van Hummelen. Comparative analysis of RNA sequencing methods for characterization of cancer transcriptomics. [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 4867. doi:10.1158/1538-7445.AM2015-4867

Retinal regeneration is facilitated by the presence of surviving neurons

Teleost fish regenerate their retinas after damage, in contrast to mammals. In zebrafish subjected to an extensive ouabain-induced lesion that destroys all neurons and spares Müller glia, functional recovery and restoration of normal optic nerve head (ONH) diameter take place at 100 days postinjury. Subsequently, regenerated retinas overproduce cells in the retinal ganglion cell (RGC) layer, and the ONH becomes enlarged. Here, we test the hypothesis that a selective injury, which spares photoreceptors and Müller glia, results in faster functional recovery and fewer long-term histological abnormalities. Following this selective retinal damage, recovery of visual function required 60 days, consistent with this hypothesis. In contrast to extensively damaged retinas, selectively damaged retinas showed fewer histological errors and did not overproduce neurons. Extensively damaged retinas had RGC axons that were delayed in pathfinding to the ONH, and showed misrouted axons within the ONH, suggesting that delayed functional recovery following an extensive lesion is related to defects in RGC axons exiting the eye and/or reaching their central targets. The atoh7, fgf8a, Sonic hedgehog (shha), and netrin-1 genes were differentially expressed, and the distribution of hedgehog protein was disrupted after extensive damage as compared with selective damage. Confirming a role for Shh signaling in supporting rapid regeneration, shha(t4) +/- zebrafish showed delayed functional recovery after selective damage. We suggest that surviving retinal neurons provide structural/molecular information to regenerating neurons, and that this patterning mechanism regulates factors such as Shh. These factors in turn control neuronal number, retinal lamination, and RGC axon pathfinding during retinal regeneration.

SlopMap: a software application tool for quick and flexible identification of similar sequences using exact k-mer matching

With the advent of Next-Generation (NG) sequencing, it has become possible to sequence a entire genomes quickly and inexpensively. However, in some experiments one only needs to extract and assembly a portion of the sequence reads, for example when performing transcriptome studies, sequencing mitochondrial genomes, or characterizing exomes. With the raw DNA-library of a complete genome it would appear to be a trivial problem to identify reads of interest. But it is not always easy to incorporate well-known tools such as BLAST, BLAT, Bowtie, and SOAP directly into a bioinformatics pipelines before the assembly stage, either due to incompatibility with the assembler's file inputs, or because it is desirable to incorporate information that must be extracted separately. For example, in order to incorporate flowgrams from a Roche 454 sequencer into the Newbler assembler it is necessary to first extract them from the original SFF files. We present SlopMap, a bioinformatics software utility that allows quickly identification similar to the provided reference reads from either Roche 454 or Illumnia DNA library. With simple and intuitive command-line interface along with file output formats compatible to assembly programs, SlopMap can be directly embedded to biological data processing pipeline without any additional programming work. In addition, SlopMap preserves flowgram information needed for Roche 454 assembler.

Comparative genome analysis of an avirulent and two virulent strains of avian Pasteurella multocida reveals candidate genes involved in fitness and pathogenicity

BACKGROUND

Pasteurella multocida is the etiologic agent of fowl cholera, a highly contagious and severe disease of poultry causing significant mortality and morbidity throughout the world. All types of poultry are susceptible to fowl cholera. Turkeys are most susceptible to the peracute/acute forms of the disease while chickens are most susceptible to the acute and chronic forms of the disease. The whole genome of the Pm70 strain of P. multocida was sequenced and annotated in 2001. The Pm70 strain is not virulent to chickens and turkeys. In contrast, strains X73 and P1059 are highly virulent to turkeys, chickens, and other poultry species. In this study, we sequenced the genomes of P. multocida strains X73 and P1059 and undertook a detailed comparative genome analysis with the avirulent Pm70 strain. The goal of this study was to identify candidate genes in the virulent strains that may be involved in pathogenicity of fowl cholera disease.

RESULTS

Comparison of virulent versus avirulent avian P. multocida genomes revealed 336 unique genes among the P1059 and/or X73 genomes compared to strain Pm70. Genes of interest within this subset included those encoding an L-fucose transport and utilization system, several novel sugar transport systems, and several novel hemagglutinins including one designated PfhB4. Additionally, substantial amino acid variation was observed in many core outer membrane proteins and single nucleotide polymorphism analysis confirmed a higher dN/dS ratio within proteins localized to the outer membrane.

CONCLUSIONS

Comparative analyses of highly virulent versus avirulent avian P. multocida identified a number of genomic differences that may shed light on the ability of highly virulent strains to cause disease in the avian host, including those that could be associated with enhanced virulence or fitness.

Draft Genome Sequences of Two Virulent Serotypes of Avian Pasteurella multocida

Here we report the draft genome sequences of two virulent avian strains of Pasteurella multocida. Comparative analyses of these genomes were done with the published genome sequence of avirulent P. multocida strain Pm70.

Retinal proliferation response in the buphthalmic zebrafish, bugeye

The zebrafish retina regenerates in response to acute retinal lesions, replacing damaged neurons with new neurons. In this study we test the hypothesis that chronic stress to inner retinal neurons also triggers a retinal regeneration response in the bugeye zebrafish. Mutations in the lrp2 gene in zebrafish are associated with a progressive eye phenotype (bugeye) that models several risk factors for human glaucoma including buphthalmos (enlarged eyes), elevated intraocular pressure (IOP), and upregulation of genes related to retinal ganglion cell pathology. The retinas of adult bugeye zebrafish showed high rates of ongoing proliferation which resulted in the production of a small number of new retinal neurons, particularly photoreceptors. A marker of mechanical cell stress, Hsp27, was strongly expressed in inner retinal neurons and glia of bugeye retinas. The more enlarged eyes of individual bugeye zebrafish showed disrupted retinal lamination, and a persistent reduced density of neurons in the ganglion cell layer (GCL), although total numbers of GCL neurons were higher than in control eyes. Despite the presence of a proliferative response to damage, the adult bugeye zebrafish remained behaviorally blind. These findings suggest the existence of an unsuccessful regenerative response to a persistent pathological condition in the bugeye zebrafish.

Retinal proliferation response in the buphthalmic zebrafish, bugeye

The zebrafish retina regenerates in response to acute retinal lesions, replacing damaged neurons with new neurons. In this study we test the hypothesis that chronic stress to inner retinal neurons also triggers a retinal regeneration response in the bugeye zebrafish. Mutations in the lrp2 gene in zebrafish are associated with a progressive eye phenotype (bugeye) that models several risk factors for human glaucoma including buphthalmos (enlarged eyes), elevated intraocular pressure (IOP), and upregulation of genes related to retinal ganglion cell pathology. The retinas of adult bugeye zebrafish showed high rates of ongoing proliferation which resulted in the production of a small number of new retinal neurons, particularly photoreceptors. A marker of mechanical cell stress, Hsp27, was strongly expressed in inner retinal neurons and glia of bugeye retinas. The more enlarged eyes of individual bugeye zebrafish showed disrupted retinal lamination, and a persistent reduced density of neurons in the ganglion cell layer (GCL), although total numbers of GCL neurons were higher than in control eyes. Despite the presence of a proliferative response to damage, the adult bugeye zebrafish remained behaviorally blind. These findings suggest the existence of an unsuccessful regenerative response to a persistent pathological condition in the bugeye zebrafish.

Orphans as a window on the AIDS epidemic in Sub-Saharan Africa: initial results and implications of a study in Uganda

Provisional estimates from a Save the Children Fund enumeration study in four Ugandan districts indicate that the total number of orphans (one or both parents missing) ranges between 620,000 and 1,200,000. Needs assessments with guardians and local administrators show that although extended family networks are absorbing these children according to traditional rules, they may be vulnerable to increased mortality due to economic and health stresses on their caretakers, many of whom are elderly persons. The orphan burden will increase in Uganda and other Sub-Saharan African countries over the next few years. Allocation of additional national and international resources must be considered to avert breakdowns in community and familial support systems and consequent increases in under 5 mortality. The orphan burden is a window on the potential for massive social breakdown and dislocation in Sub-Saharan Africa resulting from high AIDS-related mortality. Methodologies for data collection and planning that use indigenous political systems must be built quickly to avert disaster.

Levels of health development: a new tool for comparative research and policy formulation

Levels of health development are formed by mathematically clustering countries using six health status indicators: crude birth, crude death, infant mortality and child death rates, and male and female life expectancy. Stratifying two international samples of 128 and 163 countries into levels of health development--groups with similar health status profiles--improves the results of regression analyses used to identify economic, political, social, educational, health and other health determinants. For this reason, health development levels are a systematic framework for delineation of health determinants. Earlier large scale statistical studies have been limited in their success in part because they did not partition their data sets prior to analysis, or used inappropriate criteria that blurred rather than heightened developmental differences in underlying social systems. These developmental differences regulate the way in which health status inputs are converted into health status outputs, defining the relative importance of health determinants at various developmental levels. At lowest health development levels (countries with poorer health status), the under-development of economic, health and educational infrastructures creates a vacuum which allows international intervention (aid, investment, export/import activities) to play a dominant role in health status determination. At middle health development levels, health and educational infrastructures are better developed, but still secondary in importance as health status determinants to basic economic infrastructure. Demographic problems are particularly apparent at these levels. At higher health development levels, education, women's status, and political structure are especially important health status determinants. This research has facilitated the identification of health status determinants for use in health policy analysis. Recommendations for future research include use of findings in health policymaking by individual countries and by comparative researchers, and development of appropriate health systems models for each level of health development.

Marketing and strategic management: integrating skills for a better hospital

Participants in a 1985 one-day seminar sponsored by the American Hospital Association's Society for Hospital Planning and Marketing were asked two questions: How many of the hospitals represented here have conducted marketing surveys in the recent past? How many of you were satisfied with the results of the survey or could integrate it into the strategic management of your institution? While all but two of the 125 participants answered yes to the first question, only two responded affirmatively to the second. A gap between having a survey done and implementing the results had been identified. The administrators had probably rushed into "marketing" with little forethought and even less effort to comprehend how this management skill fits into existing institutional skills, capabilities, roles, and goals. To close the gap between marketing theory and practice an institution must adopt a more far-reaching, proactive stance toward integrating marketing into the management routine at an early stage. This article presents a case study that may help health care administrators rethink the role of marketing in management and its place in the sequence of strategic decision making for their institution.

Historical perspectives on the development of health systems modeling in medical anthropology

The call for macro health systems models which emerged in medical anthropology in the mid-1970s from the field's most respected thinkers has a deep theoretical history and can also be related to theoretical developments in sociology, clinical medicine and international public health. The trends leading to a recognition of the need for modeling by medical anthropologists have been the source of some of medical anthropology's limitations and weaknesses as well, especially the failure to fulfill the field's promise as a biocultural bridge for the parent discipline.