Biology subjects

Komissarov, A.

Publications and source records attributed to Komissarov, A..

9 recordsLinked to original sources

bioRxiv2025

The complete genome of a songbird

Bird genomes are the smallest among amniotes, but remain challenging to assemble due to their structural complexity. This study presents the first fully phased, diploid, telomere-to-telomere (T2T) reference genome for the zebra finch (Taeniopygia guttata), a model organism for neuroscience and evolutionary genomics. Combining multiple sequencing strategies resulted in closing nearly all gaps, adding [~]90 Mbp of previously missing sequence (7.8%). This includes T2T assemblies for all microchromosomes, including dot chromosomes, and the previously almost entirely missing chr16. The T2T genome is comprehensively annotated for genes, repeats, structural variants, and long-read methylation calls. Complete centromeric structures were assembled and annotated along with kinetochore binding sites. Relative to the previous high-quality reference of the Vertebrate Genomes Project, 2,778 (8.51%) previously unassembled or unannotated genes were identified, of which 9% overlap with segmental duplications. This first complete genome of a songbird, now the new public reference, illuminates avian genome architecture and function.

genomics↗

bioRxiv2023

Cancer relevance of circulating antibodies against LINE-1 antigens in humans

LINE-1 (L1), the most abundant family of autonomous retrotransposons occupying over 17% of human DNA, is epigenetically silenced in normal tissues but frequently derepressed in cancer, suggesting that L1-encoded proteins may act as tumor-associated antigens recognized by the immune system. Here, we established an immunoassay for detecting circulating autoantibodies against L1 proteins in human blood. Using this assay in >3,000 individuals with or without cancer, we observed significantly higher IgG titers against L1-encoded ORF1p and ORF2p in patients with lung, pancreatic, ovarian, esophageal, and liver cancers compared to healthy individuals. Remarkably, elevated levels of anti-ORF1p-reactive IgG were observed in cancer patients with disease stages 1 and 2, indicating that immune response to L1 antigens can occur at early phases of carcinogenesis. We conclude that the antibody response against L1 antigens could contribute to the diagnosis and determination of immunoreactivity of tumors among cancer types that frequently escape early detection.

cancer biology↗

bioRxiv2022

The first complete mitochondrial genome of Diadema antillarum (Diadematoida, Diadematidae)

The mitochondrial genome of the long-spined black sea urchin, Diadema antillarum, was sequenced using Illumina next generation sequencing technology. The complete mitogenome is 15,708 bp in length, containing 2 rRNA, 22 tRNA and 13 protein-coding genes, plus a non-coding control region of 133 bp. The nucleotide composition includes 18.37% G, 23.79% C, 26.84% A and 30.99% T. The A + T bias is 57.84%. Phylogenetic analysis based on 12 complete mitochondrial genomes of sea urchins including four species of the family Diadematidae supported familial monophyly, however the two Diadema species, D. antillarum and D. setosum were not recovered as sister taxa.

genomics↗

bioRxiv2022

APC couples neuronal mRNAs to multiple kinesins and EB1 for bidirectional mRNA movements along microtubules

Understanding where in the cytoplasm mRNAs are translated is increasingly recognised as being as important as knowing the timing and level of protein expression. mRNAs are localised via active motor-driven transport along microtubules (MTs) but the underlying essential factors and dynamic interactions are largely unknown. Using biochemical in vitro reconstitutions with purified mammalian proteins, multi-colour TIRF-microscopy (TIRF-M), and interaction kinetics measurements, we show that adenomatous polyposis coli (APC) enables kinesin-1- and kinesin-2-based mRNA transport, and that APC is an ideal adaptor for long-range mRNA transport as it forms highly stable complexes with 3UTR fragments of several neuronal mRNAs (APC-RNPs). The kinesin-1 KIF5A binds and transports several neuronal mRNP components such as FMRP, PUR, and mRNA fragments weakly, whereas the transport frequency of the mRNA fragments is significantly increased by APC. APC-RNP-motor complexes can assemble on MTs, generating highly processive mRNA transport events. We further find that EB1 recruits APC-RNPs to dynamically growing MT ends and APC-RNPs track shrinking MTs, producing MT minus-end-directed RNA motility due to the high dwell times of APC on MTs. Our findings establish APC as a versatile mRNA-kinesin adaptor and a key factor for the assembly and bidirectional movement of neuronal transport mRNPs.

biochemistry↗

bioRxiv2021

Transcriptomic analysis of DNA damage response in zebrafish embryos under simulated microgravity

Space is an extremely hostile environment. Traveling to space has numerous effects on the body of the astronauts at a molecular level. As space agencies prepare for long-term missions, it becomes important to investigate these problems and address them. Thus, in the current study, we assessed the impact of simulated microgravity on the basic pathways especially DNA damage response. We identified a total of 7542 significantly differentially expressed genes. Out of these genes, 4504 were found to be up-regulated while 3038 were down-regulated in the simulated microgravity group in comparison to controls. Pathway enrichment analysis revealed that simulated microgravity has an effect on vital basic biological processes like DNA damage repair, peptide transport, and metabolism. To explore if the same pathways were also altered in humans, we explored the NASA twin study data and found that DDR was also significantly affected in the astronaut but due to ionizing radiation. Upon further investigation, we found that 62 genes belonging to the DDR pathway were mutually differentially expressed in Scott Kelly and the zebrafish embryos. However, there were 29 significantly differentially expressed genes belonging to the DDR pathway in zebrafish embryos that were not found to be differentially expressed in Scott Kelly. Out of these 29 genes, 14 were specific to zebrafish. Upon further investigation, we found that the DDR pathway is affected differently in simulated microgravity as compared to ionizing radiation. These observations provide a preliminary look into the difference in DDR induced by the different factors of spaceflight.

bioinformatics↗

bioRxiv2020

Quality control of low-frequency variants in SARS-CoV-2 genomes

During the current outbreak of COVID-19, research labs around the globe submit sequences of the local SARS-CoV-2 genomes to the GISAID database to provide a comprehensive analysis of the variability and spread of the virus during the outbreak. We explored the variations in the submitted genomes and found a significant number of variants that can be seen only in one submission (singletons). While it is not completely clear whether these variants are erroneous or not, these variants show lower transition/transversion ratio. These singleton variants may influence the estimations of the viral mutation rate and tree topology. We suggest that genomes with multiple singletons even marked as high-covered should be considered with caution. We also provide a simple script for checking variant frequency against the database before submission.

genomics↗

bioRxiv2019

Cold and distant: structural features of the nucleoprotein complex of a cold-adapted influenza A virus strain

Two influenza A nucleoprotein variants (wt: G102R; and mutant: G102R and E292G) were studied with regard to macro-molecular interactions in oligomeric form (24-mers). The E292G mutation has been previously shown to provide cold adaptation. Molecular dynamics simulations of these complexes and trajectory analysis showed that the most significant difference between the obtained models was distance differences between nucleoprotein complex strands. Influenza virus nucleoprotein complexes were isolated from strains bearing the corresponding NP amino acid substitutions. The isolated complexes were characterized by transmission electron microscopy and differential scanning fluorimetry (DSF). Presence of the E292G substitution was shown by DSF to affect nucleoprotein complex melting temperature. In the filament interface peptide model, it was shown that the peptide corresponding in primary structure to the wild-type NP (SGYDFEREGYS, wild type peptide) is prone to temperature-dependent self-association, unlike the peptide carrying the substitution corresponding to E292G (SGYDFGREGYS, mutant peptide). It was also shown that the SGYDFEREGYS peptide (wt) is capable of interacting with a recombinant full-size monomeric nucleoprotein (with primary structure corresponding to wild type); this interactions equilibrium dissociation constant is five orders of magnitude lower than for the SGYDFGREGYS peptide. Using small-angle neutron scattering (SANS), the supramolecular structures of isolated complexes of these proteins was studied at temperatures of 15, 32, and 37{degrees}C. SANS data show that the structures of the studied complexes (mutant or normal proteins with RNA) at elevated temperature differ from the rod-like particle model and react differently to temperature changes. The data suggest that the mechanism behind cold adaptation with E292G is associated with a weakening of the interaction between strands of the ribonucleoprotein complex and, as a result, the appearance of inter-chain interface flexibility necessary for complex function at low temperature.

biophysics↗

bioRxiv2019

A reconstituted mammalian APC-kinesin complex selectively transports defined packages of axonal mRNAs

Through the asymmetric distribution of mRNAs cells spatially regulate gene expression to create cyto-plasmic domains with specialized functions. In mammalian neurons, mRNA localization is required for essential processes as cell polarization, migration and synaptic plasticity underlying long-term memory formation. The essential components driving cytoplasmic mRNA transport in neurons and mammalian cells are not known. Here, we report the first reconstitution of a mammalian mRNA transport system revealing that the tumour suppressor adenomatous polyposis coli (APC) forms stable complexes with the axonally localised {beta}-actin and {beta}2B-tubulin mRNAs which are linked to a heterotrimeric kinesin-2 via the cargo adaptor KAP3. APC activates kinesin-2 and both proteins are sufficient to drive specific transport of defined mRNA packages. Guanine-rich sequences located in 3UTRs of axonal mRNAs increase transport efficiency and balance the access of different mRNAs to the transport system. Our findings reveal for the first time a minimal set of proteins capable of driving kinesin-based, mammalian mRNA transport.

biochemistry↗

bioRxiv2017

Innovative assembly strategy contributes to the understanding of evolution and conservation genetics of the critically endangered Solenodon paradoxus from the island of Hispaniola

Solenodons are insectivores living on the Caribbean islands, with few surviving related taxa. The genus occupies one of the most ancient branches among the placental mammals. The history, unique biology and adaptations of these enigmatic venomous species, can be greatly advanced given the availability of genome data, but the whole genome assembly for solenodons has never been previously performed, partially due to the difficulty in obtaining samples from the field. Island isolation has likely resulted in extreme homozygosity within the Hispaniolan solenodon (Solenodon paradoxus), thus we tested the performance of several assembly strategies for performance with genetically impoverished species genomes. The string-graph based assembly strategy seems a better choice compared to the conventional de Brujn graph approach, due to the high levels of homozygosity, which is often a hallmark of endemic or endangered species. A consensus reference genome was assembled from sequences of five individuals from the southern subspecies (S. p. woodi). In addition, we obtained one additional sequence of the northern subspecies (S. p. paradoxus). The resulting genome assemblies were compared to each other, and annotated for genes, with a specific emphasis on the venomous genes, repeats, variable microsatellite loci and other genomic variants. Phylogenetic positioning and selection signatures were inferred based on 4,416 single copy orthologs from 10 other mammals. Patterns of SNP variation allowed us to infer population demography, which indicated a subspecies split within the Hispaniolan solenodon at least 300 Kya.

evolutionary biology↗