Biology subjects

Suyama, M.

Publications and source records attributed to Suyama, M..

7 recordsLinked to original sources

bioRxiv2025

Repressive S-adenosylmethionine biosynthesis status inhibits transcription of HeT-A retrotransposon in the germline of Drosophila.

S-adenosylmethionine (SAM) is the principal cellular donor of methyl moiety in the methylation reaction and regulates gene expression by regulating methylation-related cellular events, such as epigenetic status. Although SAM biosynthesis affects a variety of biological phenomena including disease and aging, whether cell-specific SAM biosynthesis status is present and how it contributes to cellular function are largely unknown. Here, we firstly showed that the Drosophila germline in gametogenesis has a repressive SAM biosynthesis status through the observation of SAM synthetase (Sam-S), a key enzyme for SAM biosynthesis. In addition, our study showed that germline-unique repressive SAM biosynthesis status contributes to inhibition of retrotransposon expression; enhancement of SAM biosynthesis in germline caused excessive expression of retrotransposons including HeT-A, a telomere-specific retroelement, as the most affected target. We found that the promoter activity of HeT-A is enhanced in SAM increased condition with increased accumulation of 6mA DNA methylation, the major DNA methylation modification in the Drosophila genome. Interestingly, the enhanced 6mA enrichment and gene expression in enriched loci were not correlated in other retrotransposons or structural genes. Taken together, our results suggest that SAM-deficient status in the germline uniquely regulates HeT-A transcription via 6mA methylation modification. Thus, our study provides a new understanding of how germline unique metabolic status contributes to regulation of the retrotransposon.

developmental biology↗

bioRxiv2024

Comparative transcriptome and variant analyses of the pancreatic islets of a rat model of obese type 2 diabetes identifies a frequently distributed nonsense mutation in the lipocalin 2 gene

We have recently established the Zucker fatty diabetes mellitus (ZFDM) rat as a novel model of obese type 2 diabetes (T2D), originating from the obese Zucker fatty (ZF) rat harboring a missense mutation in the leptin receptor gene. Pathogenesis of dysfunction of the pancreatic islets and genetic factors of T2D in ZFDM rats remain unknown. Here, we perform comparative transcriptome and variant analyses of the pancreatic islets between the two strains. Among differentially expressed genes irrespective of obesity and glucose intolerance states, we identify a nonsense mutation, c.409C>T (p.Gln137X), in the lipocalin 2 (Lcn2) gene which encodes a secreted protein called neutrophil gelatinase-associated lipocalin, a well-known biomarker for inflammation. Interestingly, we find that the Lcn2 mutation is distributed widely in rat species, such as commonly used DA and F344 strains. We examine the Lcn2 mutation as a strong candidate gene for T2D in ZFDM rats by using genome editing of ZFDM rats in which the nonsense mutation is replaced with a wild-type nucleotide. We find that the genome editing well works but also observe that there is no significant difference in the development of T2D between genome-edited and original ZFDM rats. Finally, we perform a genetic linkage analysis by using backcross progeny between ZF and ZFDM rats and confirm that the Lcn2 mutation exhibits no significant association with the onset of T2D. Our data indicate that several rat strains would serve as Lcn2 deficient models, contributing to elucidate pathophysiological roles of Lcn2 in a wide variety of phenotypes.

genetics↗

bioRxiv2023

The anti-tumor effect of trifluridine via induction of aberrant mitosis is unaffected by mutations modulating p53 activity

The fluorinated thymidine analogue trifluridine (FTD) is a chemotherapeutic drug commonly used to treat cancer; however, the mechanism by which FTD induces cytotoxicity is not fully understood. In addition, the effect of gain-of-function (GOF) missense mutations of the TP53 gene (encoding p53), which promote cancer progression and chemotherapeutic drug resistance, on the chemotherapeutic efficacy of FTD is unclear. Here, we revealed the mechanisms by which FTD induced aberrant mitosis and contributed to cytotoxicity in both p53-null and p53-GOF missense mutant cells. In p53-null mutant cells, FTD induced DNA double-stranded breaks, single-stranded DNA accumulation, and the associated DNA damage repair responses during G2 phase. Nevertheless, FTD-induced DNA damage and the related responses were not sufficient to trigger strict G2/M checkpoint arrest. Thus, these features were carried over into mitosis, resulting in chromosome breaks and bridges, and subsequent cytokinesis failure. Improper mitotic exit eventually led to cell apoptosis, caused by the accumulation of extensive DNA damage and the presence of micronuclei encapsulated in the disrupted nuclear envelope. Upon FTD treatment, the behavior of the p53-GOF-missense-mutant, isogenic cell lines, generated by CRISPR/Cas9 genome editing, was similar to that of p53-null mutant cells. Thus, our data suggest that FTD treatment overrode the effect on gene expression induced by p53-GOF mutants and exerted its anti-tumor activity in a manner that was independent of p53 function.

cell biology↗

bioRxiv2022

Exome-wide benchmark of difficult-to-sequence regions using short-read next-generation DNA sequencing

Next-generation DNA sequencing (NGS) in short-read mode has been recently used for genetic testing in various clinical settings. NGS data accuracy is crucial in clinical settings, and several reports regarding quality control of NGS data, focusing mostly on establishing NGS sequence read accuracy, have been published thus far. Variant calling is another critical source of NGS errors that remains mostly unexplored despite its established significance. In this study, we used a machine-learning-based method to establish an exome-wide benchmark of difficult-to-sequence regions using 10 genome sequence features on the basis of real-world NGS data accumulated in The Genome Aggregation Database (gnomAD) of the human reference genome sequence (GRCh38/hg38). We used the obtained metrics, designated "UNMET score," along with other lines of structural information of the human genome to identify difficult-to-sequence genomic regions using conventional NGS. Thus, the UNMET score could provide appropriate caveats to address potential sequential errors in protein-coding exons of the human reference genome sequence GRCh38/hg38 in clinical sequencing.

genomics↗

bioRxiv2022

Genome-wide identification of loss of heterozygosity reveals its association with spatial positioning of chromosomes

Loss of heterozygosity (LOH) is a genetic alteration that results from the loss of one allele at a heterozygous locus. Some LOH events are generated by mitotic homologous recombination after monoallelic defection, then the novel homozygous locus has two copies of the normal counterpart allele. This phenomenon can serve as a source of genome diversity and is associated with various diseases. To clarify the nature of the LOH such as the frequency, genomic distribution, and inheritance pattern, we made use of whole-genome sequencing data of the three-generation CEPH/Utah family cohort, with the pedigree consisting of grandparents, parents, and offspring. We identified an average of 40.7 LOH events per individual taking advantage of 285 healthy individuals from 33 families in the cohort. On average 65% of them were classified as gonosomal-mosaicism-associated LOH, which exists in both germline and somatic cells. We also confirmed that the incidence of the LOH has little to do with the parents age and sex. Furthermore, through the analysis of the genomic region including the LOH, we found that the chance of the occurrence of the LOH tends to increase at the GC-rich locus and/or on the chromosome having a relatively close inter-homolog distance. We expect that these results provide significant insights into the association between genetic alteration and spatial position of chromosomes as well as the intrinsic genetic property of the LOH. Author SummaryLoss of heterozygosity (LOH) is a common genetic alteration that a heterozygous locus becomes a homozygous locus. In some cases, if a monoallelic defection accompanying homologous recombination between inter-homolog occurs, it results in copy-neutral LOH having two copies of the allele. Although the LOH is potentially important in understanding pathogenesis of various diseases, its fundamental features have received scant attention. To characterize the nature of the LOH, data from single individuals and their parents are required. This is because it would be difficult to discriminate between the LOH and a normal homozygous allelic state using genomic data obtained only from a single individual. Whole-genome sequencing data of 33 CEPH/Utah families, which comprise large three-generation family units, motivated us to perform a genome-wide identification of the LOH. Using this dataset, we successfully identified the LOH and analyzed its frequency, genomic distribution, and inheritance pattern. Moreover, we revealed that the occurrence of the LOH was affected by the inter-homolog distances, which reflect the chromosome territory. Our findings pertaining to the LOH provide insight into the association between genetic alteration and spatial positioning of chromosomes.

genomics↗

bioRxiv2022

Mapping of promoter usage QTL using RNA-seq data reveals their contributions to complex traits

Genomic variations are associated with gene expression levels, which are called expression quantitative trait loci (eQTL). Most eQTL may affect the total gene expression levels by regulating transcriptional activities of a specific promoter. However, the direct exploration of genomic loci associated with promoter activities using RNA-seq data has been challenging because eQTL analyses treat the total expression levels estimated by summing those of all isoforms transcribed from distinct promoters. Here we propose a computational framework for identifying genomic loci associated with promoter activities, called promoter usage quantitative trait loci (puQTL), using conventional RNA-seq data. By leveraging public RNA-seq datasets from the lymphoblastoid cell lines of 438 individuals from the GEUVADIS project, we obtained promoter activity estimates and mapped 2,592 puQTL at the 10% FDR level. The results of puQTL mapping enabled us to interpret the manner in which genomic variations regulate gene expression. We found that 310 puQTL genes (16.1%) were not detected by eQTL analysis, suggesting that our pipeline can identify novel variant-gene associations. Furthermore, we identified genomic loci associated with the activity of "hidden" promoters, which the standard eQTL studies have ignored. We found that most puQTL signals were concordant with at least one genome-wide association study (GWAS) signal, enabling novel interpretations of the molecular mechanisms of complex traits. Our results emphasize the importance of the re-analysis of public RNA-seq datasets to obtain novel insights into gene regulation by genomic variations and their contributions to complex traits.

genomics↗

bioRxiv2021

Functional variants in hematopoietic transcription factor footprints and their roles in the risk of immune system diseases

Genome-wide association studies (GWAS) have been performed to identify thousands of variants in the human genome as disease risk markers, but functional variants that actually affect gene regulation and their genomic features remain largely unknown. Here we performed a comprehensive survey of functional variants in the regulatory elements of the human genome. We integrated hematopoietic transcription factor (TF) footprints datasets generated by ENCODE project with multiple quantitative trait locus (QTL) datasets (eQTL, caQTL, bQTL, and hQTL) and investigated the associations of functional variants and immune system disease risk. We identified candidate regulatory variants highly linked with GWAS lead variants and found that they were strongly enriched in active enhancers in hematopoietic cells, emphasizing the clinical relevance of enhancers in disease risk. Moreover, we found some strong relationships between traits and hematopoietic cell types or TFs. We highlighted some credible regulatory variants and found that a variant, rs2291668, which potentially functions in the molecular pathogenesis of multiple sclerosis, is located within a TF footprint present in a protein-coding exon of the TNFSF14 gene, indicating that protein-coding exons as well as noncoding regions can possess clinically relevant regulatory elements. Collectively, our results shed light on the molecular pathogenesis of immune system diseases. The methods described in this study can readily be applied to the study of the risk factors of other diseases.

genomics↗