Cross-species comparison of site-specific evolutionary-rate variation in influenza haemagglutinin.
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ABSTRACT:
SUBMITTER: Meyer AG
PROVIDER: S-EPMC3678335 | biostudies-literature | 2013 Mar
REPOSITORIES: biostudies-literature
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Project description:Abstract Background: One of the approaches for conducting genomics research in organisms that do not yet have a proper microarray template is to profile their expression patterns by using cross-species hybridization (CSH). Several different studies using spotted microarray for CSH resulted with contradicting conclusions as to the ability of CSH to reflect biological processes. Results: We used a tomato spotted cDNA microarray to examine the ability of CSH to reflect species specific hybridization (SSH) data. Potato RNA was hybridized to spotted cDNA tomato and potato microarrays to generate heterologous and homologous hybridization data, respectively. The results revealed difficulties in obtaining transcriptomics data from CSH that reflected those obtained from SSH. Nevertheless, once the data was filtered for those corresponding to matching probe sets, by restricting proper cutoffs of probe homology, the CSH transcriptomics data better reflected those of the SSH, to an extent that was quantitated by identification of differentially regulated genes. Conclusions: This study enabled us to outline some considerations regarding evaluation of a microarray as candidate platform for CSH study, performance of CSH and proper data analysis that may allow CSH to reflect to some extent a biological process. Keywords: cross-species hybridization; heterologous hybridization
2006-05-30 | GSE3584 | GEO
Project description:BACKGROUND:Reassortment between the RNA segments encoding haemagglutinin (HA) and neuraminidase (NA), the major antigenic influenza proteins, produces viruses with novel HA and NA subtype combinations and has preceded the emergence of pandemic strains. It has been suggested that productive viral infection requires a balance in the level of functional activity of HA and NA, arising from their closely interacting roles in the viral life cycle, and that this functional balance could be mediated by genetic changes in the HA and NA. Here, we investigate how the selective pressure varies for H7 avian influenza HA on different NA subtype backgrounds. RESULTS:By extending Bayesian stochastic mutational mapping methods to calculate the ratio of the rate of non-synonymous change to the rate of synonymous change (d(N)/d(S)), we found the average d(N)/d(S) across the avian influenza H7 HA1 region to be significantly greater on an N2 NA subtype background than on an N1, N3 or N7 background. Observed differences in evolutionary rates of H7 HA on different NA subtype backgrounds could not be attributed to underlying differences between avian host species or virus pathogenicity. Examination of d(N)/d(S) values for each subtype on a site-by-site basis indicated that the elevated d(N)/d(S) on the N2 NA background was a result of increased selection, rather than a relaxation of selective constraint. CONCLUSIONS:Our results are consistent with the hypothesis that reassortment exposes influenza HA to significant changes in selective pressure through genetic interactions with NA. Such epistatic effects might be explicitly accounted for in future models of influenza evolution.
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Project description:Site-specific evolutionary rate shifts are defined as protein sites, where the rate of substitution has changed dramatically across the phylogeny. With respect to a given clade, sites may either undergo a rate acceleration or a rate deceleration, reflecting a site that was conserved and became variable, or vice-versa, respectively. Sites displaying such a dramatic evolutionary change may point to a loss or gain of function at the protein site, reflecting adaptation, or they may indicate epistatic interactions among sites. Here, we analyzed full genomes of HIV and SIV-1 and identified 271 rate-shifting sites along the HIV-1/SIV phylogeny. The majority of rate shifts occurred at long branches, often corresponding to cross-species transmission branches. We noted that in most proteins, the number of rate accelerations and decelerations was equal, and we suggest that this reflects epistatic interactions among sites. However, several accessory proteins were enriched for either accelerations or decelerations, and we suggest that this may be a signature of adaptation to new hosts. Interestingly, the non-pandemic HIV-1 group O clade exhibited a substantially higher number of rate-shift events than the pandemic group M clade. We propose that this may be a reflection of the height of the species barrier between gorillas and humans versus chimpanzees and humans. Our results provide a genome-wide view of the constraints operating on proteins of HIV-1 and SIV.
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Project description:Recombinant proteins are of great interest in glycobiology and proteomics, known especially for their reproducibility and accessibility. However, variation in glycosylation among recombinant glycoproteins is not well understood and may depend on numerous conditions in the biomanufacturing process. In order to confidently assess variation in glycosylation measurements, it is vital to both optimize the measurement of, and determine the degree of variation between, distributions of glycosylation on specific sites of glycoproteins. This is especially important for glycoproteins that are known to have rapid sequence changes, such as with different influenza strains. In this study, eight strains of recombinant influenza hemagglutinin and neuraminidase produced from HEK293 cell line were obtained from four vendors and digestion was conducted using a series of complex multi-enzymatic methods designed to isolate glycopeptide sequons. Site-specific glycosylation profiles of intact glycopeptides were produced using mass spectrometric evaluation on an orbitrap system and compared using spectral similarity scores. Variation in glycan abundances and distribution was most pronounced between different strains of virus (similarity score = 383 out of 1000), whereas replicates resulted in low variation (similarity score = 957 out of 1000). Glycan variation was also measured based on differences between vendors, lots, batches, protease digestion, and intra-protein site. The most abundant glycans in all of these influenza glycoproteins were monofucosylated and complex, as reported by other laboratories. However, it was found that different vendors can produce very different glycan distributions for the same glycosylation site. Notably, it is demonstrated that glycan distributions are similar for conserved regions of influenza glycoproteins. Overall, these methods present a potential use in developing reproducible measurements of glycosylated biologics for quality control or making more informed decisions in biomanufacturing.
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Project description:Comparison of expression in liver samples of human, chimp, orang and rhesus, by using a novel multi-species cDNA array Keywords: other
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