Biology subjects

Kitao, K.

Publications and source records attributed to Kitao, K..

6 recordsLinked to original sources

bioRxiv2026

Long-read sequencing reveals transposable element-derived chimeric transcripts at zygotic genome activation in mammalian embryos

BackgroundTransposable elements (TEs) are mobile genomic sequences that constitute one-third to one-half of the mammalian genome. Recently, TEs have been recognized for their important roles as cis-regulatory elements. TEs are broadly activated during zygotic genome activation (ZGA) in mammalian embryos, where they function as alternative promoters of host genes and drive the transcription of chimeric transcripts. However, the construction of comprehensive chimeric transcript databases based on short-read sequencing remains limited due to the repetitive and abundant nature of TEs in the genome. Here, we used long-read RNA sequencing to construct a comprehensive dataset of chimeric transcripts expressed in ZGA mouse and bovine embryos. ResultsWe identified 11,996 and 4,755 chimeric transcripts variants derived from 2,695 and 1,200 host genes in mouse and bovine, respectively, exceeding the numbers reported in previous short-read-based studies. Among them, 114 orthologous pairs produced chimeric transcripts in both species. Gene Ontology analysis revealed significant enrichment of terms related to transcriptional regulation and protein modification in mouse, whereas no terms were significantly enriched in bovine. Assessment of the protein-coding potential of the TE-driven transcripts using predicted open reading frames (ORFs) revealed that the proportion of "Protein-coding" transcripts was lower, whereas that of "LncRNA" (long non-coding RNA) was higher compared with all transcripts in both species. Among the ORFs classified as "Protein-coding", comparison with canonical ORFs revealed a tendency for the N terminus to be truncated while the C terminus remained intact in both species. TE-derived promoters used in mouse were enriched for mouse-specific TEs, whereas those in bovine were enriched for older TEs conserved among eutherians. In addition, long-read sequencing detected a greater number and proportion of TEs used as promoters in mouse and bovine than short-read sequencing. Although motif analysis identified KLF5 and OTX2 binding sites upstream of TE-derived promoters in both species, the specific TEs containing these motifs differed between the two species. ConclusionsThis study presents the first long-read sequencing analysis of chimeric transcripts in mammalian embryos in two species. Our approach revealed the functional similarities of chimeric transcripts between species, as well as species-specific differences in their TE compositions.

developmental biology↗

bioRxiv2026

Multi-Omic Analyses of Dietary Fatty Acid-Microbe-Host Interactions Reveal Metaorganismal Lipid Metabolic Crosstalk Impacting Cardiometabolic Disease

Following a meal, our gut microbiome and human cells collaborate via metaorganismal metabolic circuits to produce diverse nutrient metabolites that systemically circulate to influence health and disease. Although there are now several examples of bacterial fiber-, amino acid-, and micronutrient-derived metabolites impacting cardiometabolic disease, very little is known in regards to how diet-microbe-host interactions impact lipid homeostasis. Here we address this by defining dietary fatty acid substrate availability in germ-free versus conventionally-raised mice coupled to deep multi-omic metabolic phenotyping. Our data demonstrate that the effects of dietary saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA) on the host lipidome, transcriptome, proteome and metabolome are uniquely impacted by resident microbiota. Also, the hepatic levels of both pro-inflammatory and pro-resolving lipid mediators are strongly influenced by dietary fatty acid-microbe interactions. This study presents a unique resource to the nutrition and metabolism research community to advance our understanding of metaorganismal lipid metabolism. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC="FIGDIR/small/705588v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@4fc7e3org.highwire.dtl.DTLVardef@1cc1dc8org.highwire.dtl.DTLVardef@1b7648dorg.highwire.dtl.DTLVardef@12a8088_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGRAPHICAL ABSTRACTC_FLOATNO C_FIG

biochemistry↗

bioRxiv2024

Birth of protein-coding exons by ancient domestication of LINE retrotransposon

Transposons, occasionally domesticated as novel host protein-coding genes, are responsible for the lineage-specific functions in vertebrates. LINE-1 (L1) is one of the most active transposons in the vertebrate genomes. Despite its abundance, the contribution of L1 to the birth of vertebrate proteins remains unelucidated. Here, we present a novel mechanism for the origination of de novo proteins, in which the L1 retrotransposons are incorporated into host genes as protein-coding exons by alternative splicing. L1 ORF1 protein (ORF1p) is an RNA-binding protein that binds to L1 RNA and is required for retrotransposition by acting as an RNA chaperone. We identified a splicing variant of myosin light chain 4 (MYL4) containing an L1 ORF1-derived exon and encoding a chimeric protein of L1 ORF1p and MYL4, named Lyosin. Molecular evolutionary analysis revealed that Lyosin was acquired in the common ancestor of reptiles and birds during the Paleozoic era. The amino acid sequence of Lyosin had undergone purifying selection although it was lost in some lineages, including the Neognathae birds and snakes. The transcripts encoding Lyosin were expressed in the testes of two lizard species, suggesting that its function is different from that of the canonical MYL4 expressed specifically in the heart. Furthermore, sequence searches revealed other evolutionarily conserved chimeric isoforms fused to the L1 ORF1p in three genes in vertebrates. Our findings suggest a novel evolutionary mechanism for the birth of lineage-specific proteins derived from transposons and implicate the previously unrecognized adaptive functions of L1 ORF1p.

evolutionary biology↗

bioRxiv2022

Dynamic evolution of retroviral envelope genes in egg-laying mammalian genomes

Independently acquired envelope (env) genes from endogenous retroviruses have contributed to the placental trophoblast cell-cell fusion in therian mammals. Egg-laying mammals (monotremes) are an important sister clade for understanding mammalian placental evolution, but the env genes in their genomes have yet to be investigated. Here, env-derived open reading frames (env-ORFs) encoding more than 400 amino-acid lengths were searched in the genomes of two monotremes: platypus and echidna. Only two env-ORFs were present in the platypus genome, whereas 121 env-ORFs were found in the echidna genome. The echidna env-ORFs were phylogenetically classified into seven groups named env-Tac1 to -Tac7. Among them, the env-Tac1 group contained only a single gene, and its amino acid sequence showed high similarity to those of the RD114/simian type D retroviruses. Using the pseudotyped virus assay, we demonstrated that the Env-Tac1 protein utilizes echidna sodium-dependent neutral amino acid transporter type 1 and 2 (ASCT1 and ASCT2) as entry receptors. Moreover, the Env-Tac1 protein caused cell-cell fusion in human 293T cells depending on the expression of ASCT1 and ASCT2. These results illustrate that fusogenic env genes are not restricted to placental mammals, providing insights into the evolution of retroviral genes and the placenta.

genomics↗

bioRxiv2022

Monotreme-specific conserved proteins derived from retroviral reverse transcriptase

Endogenous retroviruses (ERVs) have played an essential role in the evolution of mammals. Many ERV-derived genes are reported in the therians that are involved in placental development. However, the contribution of the ERV-derived genes in monotremes, which are oviparous mammals, remains to be uncovered. Here, we conducted a comprehensive search for possible ERV-derived genes in platypus and echidna genomes and identified three reverse transcriptase-like genes named RTOM1, 2, and 3. They were found to be clustered in the GRIP2 intron. Phylogenetic analysis revealed that RTOM1, 2, and 3 are strongly conserved between these species, and they were generated by tandem duplications before the divergence of platypus and echidna. The RTOM transcripts were specifically expressed in the testis, suggesting the physiological importance of RTOM genes. This is the first study reporting monotreme-specific de novo gene candidates derived from ERVs, which provides new insights into the unique evolution of monotremes.

genomics↗

bioRxiv2021

An ancient retroviral RNA element hidden in mammalian genomes and its involvement in co-opted retroviral gene regulation

Retroviruses utilize multiple unique RNA elements to control several aspects of RNA processing, such as splicing, subcellular export, and translation. However, it is mostly unclear whether such functional RNA elements are present in endogenous retroviruses (ERVs), many of which were inserted into the host genomes millions of years ago. Previously, in human ERV-derived syncytin-1 gene, we found a cis-acting RNA element named SPRE that enhances its protein expression. In this study, we found a 17-nt common sequence in SPRE of syncytin-1 and another ERV-derived gene, syncytin-2, and the sequence is confirmed to be essential for the expression of the proteins. We detected the sequences of SPRE-like elements in 41 ERV families. Though the SPRE-like elements were not found in currently prevailing (i.e. exogenous) viral sequences, more than thousands of copies of the elements were found in several mammalian genomes, suggesting the ancient integration and propagation of the SPRE-harboring retroviruses in mammalian lineages. Indeed, other mammalian ERV-derived genes: mac-syncytin-3 of macaque, syncytin-Ten1 of tenrec, and syncytin-Car1 of Carnivora contain the SPRE-like elements, and we validated their function for efficient protein expression by in vitro assays. A reporter assay revealed that the enhancement of gene expression by SPRE depended on reporter genes. Moreover, the mutation in SPRE did not affect the gene expression in codon-optimized syncytin-2. However, the same mutation in SPRE impaired the gene expression in wild-type syncytin-2, suggesting that the SPRE dependency of Syncytin-2 expression is due to the negative factors such as inefficient codon frequency or repressive elements within the coding sequence. These results provide new implications that ERVs harbor unique RNA elements involved in the regulation of ERV-derived genes.

molecular biology↗