Biology subjects

Kanoh, J.

Publications and source records attributed to Kanoh, J..

5 recordsLinked to original sources

bioRxiv2026

Evaluating non-lethal tissue suitability for telomere length measurement in the Japanese eel

Telomere length (TL) is increasingly used in ecology as a biomarker of individual quality and environmental stress, yet research on non-model species with complex life histories remains limited. Because TL varies among tissues and across ages in a species-specific manner, identifying non-lethal tissues that reliably reflect whole-organism telomere dynamics is essential for longitudinal telomere studies in the field. This study aimed to evaluate tissue-specific TL in Japanese eel (Anguilla japonica), an endangered catadromous fish. We first mapped the chromosomal distribution of telomeric sequences using fluorescent in situ hybridization (FISH), the first application of this method in this species. We then tested whether muscle and caudal fin, which can be sampled easily and non-lethally, can serve as suitable proxy tissues for TL measurements in wild individuals. Relative telomere length (RTL) was quantified by qPCR in blood, brain, caudal fin, gonads, heart, liver, and muscle. FISH analysis confirmed telomeric repeats at all chromosomal ends, with only weak interstitial signals on three chromosomal pairs unlikely to affect qPCR-based estimates. A generalized additive mixed model and Wilcoxons signed-rank tests revealed significant inter-tissue differences: RTL was shortest in the brain and muscle and longest in liver, blood and caudal fin. Muscle and caudal fin RTL were significantly correlated with RTL in many other tissues, supporting their use as proxy tissues for longitudinal TL monitoring, including responses to environmental variation. Both total length and age were tested as explanatory variables for RTL, and the model including total length showed a better fit than the age-based model. Non-linear relationships between RTL and total length observed in several tissues suggest physiological shifts associated with growth and sexual differentiation. Overall, these findings advance understanding of telomere dynamics in eels and establish muscle and caudal fin as suitable tissues for repeated, non-lethal TL assessment in ecological and conservation contexts.

molecular biology↗

bioRxiv2025

Discrete Subdomains Establish Epigenetic Diversity in Subtelomeric Heterochromatin

Subtelomeres are imperfect repeats adjacent to telomeres that are transcriptionally repressed by heterochromatin. Although essential for genome integrity, their repetitive nature has thwarted dissection of local heterochromatin assembly and maintenance mechanisms. By engineering Schizosaccharomyces pombe strains carrying fluorescent reporters at a single subtelomere, we uncovered distinct subdomains. These subdomains have different silencing requirements: Telomere-proximal regions rely on canonical shelterin- or RNAi-dependent nucleation pathways, whereas telomere-distal regions involve nucleosome remodelers, histone chaperones, and boundary-associated factors. Subdomains also exhibit discrete epigenetic states emerging both at homologous loci on different chromosome arms and along the same subtelomeric sequence. We document these epigenetic states using multi-generational live imaging and targeted perturbations. These analyses show that subtelomeric subdomains display position-specific, clonally variable silencing across a spectrum from robust to fragile epigenetic states. Interestingly, structural variants, common in subtelomeric sequences across eukaryotes, dictate local epigenetic stability. These findings reveal that subtelomeres, long recognized for their sequence variability, form a dynamic mosaic of coexisting epigenetic domains. This implies a wide range of gene-repressive regulatory logic at the chromosome ends, from environmental responsiveness to silencing stability.

genomics↗

bioRxiv2025

Differential quantitative requirements for pre-mRNA splicing-regulated shelterin protein levels in distinct telomere functions

Telomeres perform multiple functions to maintain genome stability, including telomere length regulation, chromosome end protection, and meiotic chromosome dynamics. These functions are governed by shelterin, a telomere-binding protein complex. Here, we show that efficient pre-mRNA splicing of the Schizosaccharomyces pombe shelterin components Rap1 and Poz1 ensures sufficient protein levels, which are critical for telomere maintenance. Our analyses revealed that Tls1 and Cay1 act at distinct steps in splicing, specifically affecting rap1 and poz1 transcripts: Tls1 strongly interacts with Brr2 (a splicing factor), whereas Cay1 preferentially associates with introns. Accordingly, deletion of tls1 and cay1 synergistically impaired splicing of rap1 and poz1 transcripts and reduced their protein levels, leading to abnormal telomere elongation. Removal of introns from the rap1 and poz1 genes restored normal protein levels and telomere length, confirming that defective splicing underlies these defects. Analyses of the phenotypes of single and double tls1{Delta} and cay1{Delta} mutants revealed that different telomere functions vary in their dependence on Rap1 levels: telomere length regulation and, to a lesser extent, meiosis require higher protein abundance, whereas chromosome end protection can be sustained with minimal amounts. These findings reveal a hierarchical requirement for Rap1 across telomere functions and establish a framework for understanding how splicing-dependent regulation of shelterin components coordinates multiple aspects of telomere biology.

molecular biology↗

bioRxiv2024

Subtelomere-specific condensed chromatin is regulated by three different histone modifications

In fission yeast, telomere-adjacent subtelomeres form a subtelomere-specific condensed chromatin structure, referred to as a knob, requiring histone H2A-S121 phosphorylation-dependent localization of Sgo2 at subtelomeres during interphase. However, the mechanism underlying specific Sgo2 localization in subtelomeres remains unclear. Our genetic screen identified Nts1, a histone deacetylase complex component, as a regulator of Sgo2 localization. Nts1 localized to subtelomeres during interphase and influenced histone H4 acetylation. The deletion of both Nts1 and Set2, a histone H3-K36 methyltransferase, led to the loss of Sgo2 at subtelomeres. These findings indicate that H4 deacetylation and H3-K36 methylation redundantly determine Sgo2 localization under H2A-S121 phosphorylation.

genetics↗

bioRxiv2020

Complete sequences of Schizosaccharomyces pombe subtelomeres reveal multiple patterns of genome variation

Genome sequences have been determined for many model organisms; however, repetitive regions such as centromeres, telomeres, and subtelomeres have not yet been sequenced completely. Here, we report the complete sequences of subtelomeric homologous (SH) regions of the fission yeast Schizosaccharomyces pombe. We overcame technical difficulties to obtain subtelomeric repetitive sequences by constructing strains that possess single SH regions. Whole sequences of SH regions revealed that each SH region consists of two distinct parts: the telomere-proximal part with mosaics of multiple common segments showing high variation among subtelomeres and strains, and the telomere-distal part showing high sequence similarity among subtelomeres with some insertions and deletions. The newly sequenced SH regions showed differences in nucleotide sequences and common segment composition compared to those in the S. pombe genome database (PomBase), which is in striking contrast to the regions outside of SH, where mutations are rarely detected. Furthermore, we identified new subtelomeric RecQ-type helicase genes, tlh3 and tlh4, which add to the already known tlh1 and tlh2, and found that the tlh1-4 genes show high sequence variation. Our results indicate that SH sequences are highly polymorphic and hot spots for genome variation. These features of subtelomeres may have contributed to genome diversity and, conversely, various diseases.

genomics↗