We developed Huntington's disease (HD)-modeling induced pluripotent stem cells (iPSCs) by genome engineering of iPSCs from healthy donors. For this, we established a homologous-recombination-based biallelic substitution technique called the allele-specific universal knock-in system (asUKiS). asUKiS allows for scarless and allele-by-allele substitution of the entire region encompassing not only the polyQ repeat but also the associated genetic modifiers surrounding the repeat region, allowing us to generate five iPSC lines with identical genetic modifiers on both alleles, differing only in polyQ repeat numbers. All cell lines were validated by allele-specific genotyping to confirm the precise engineering of both alleles. Even for modeling autosomal dominant diseases, our approach of employing biallelic modification offers the distinct advantage of enabling investigation of the effects of specific genomic mutations with minimal interference from genetic background noise.

RNA sequencing analysis was performed to develop 16 novel expressed sequence tag-simple sequence repeat (EST-SSR) markers to evaluate genetic variation in the near-threatened halophyte Artemisia fukudo Makino, which inhabits riversides and tidal muds affected by brackish water at high tide. In the four populations examined, the total number of alleles at each locus ranged from two to 13, with an average of 4.3. The observed and expected heterozygosity ranged from 0.05 to 0.64 and 0.06 to 0.72, respectively. These newly developed EST-SSR markers will support the understanding of the population genetic structure of A. fukudo and contribute to the conservation of this species.

We aimed to identify new mutants resulting from ONSEN transposition in Arabidopsis thaliana by subjecting nrpd1 mutant seedlings to heat stress. We isolated a mutant with a significantly elongated hypocotyl, named Long hypocotyl in ONSEN-inserted line 1 (hyo1). This phenotype was heritable, with progeny consistently displaying longer hypocotyls than the wild type. Genetic analysis revealed that this trait was due to a single recessive mutation. Further mapping and sequencing identified the insertion of ONSEN into the HY2 gene, a crucial regulator of hypocotyl elongation. The insertion disrupted HY2 transcription, as confirmed by quantitative PCR, leading to the observed phenotype. To assess any influence of the nrpd1 background, we generated lines backcrossed twice to wild-type Col-0, and the results were consistent with those observed in the original mutant lines. Furthermore, we examined the effect of HY2 and HYO1 mutations on flowering time by analyzing the expression levels of FT. The hyo1 mutant exhibited earlier flowering compared to both wild type and the nrpd1 mutant, with increased FT expression levels. This research highlights the impact of ONSEN transposition on gene function and phenotypic variation in A. thaliana, providing new insights into the mutagenic potential of transposons and their role in shaping plant traits.

The mitochondrial cytochrome b gene (Cytb) of the Japanese field vole (Microtus montebelli), an herbivorous rodent, was subjected to an analysis of sequence variation with the objective of elucidating the population histories of this species. Construction of a phylogenetic tree revealed the existence of several region-specific lineages in Honshu and Kyushu, which were evenly separated from each other. In consideration of the documented time-dependent evolutionary rates of rodents, the estimated divergence times indicate that the region-specific lineages of M. montebelli emerged 160,000-300,000 years ago. In a haplotype network, the region-specific lineages from northern and central Honshu tended to show star-shaped clusters, with additional internal star-shaped clusters, indicative of two periods of population expansion. The onsets of these expansions were estimated to have occurred 15,000 and 10,000 years ago, respectively, suggestive of association with the two periods of rapid warming following the last glacial maximum (LGM). In contrast, such predicted post-LGM expansion events were less pronounced in the southern lineages, implying latitudinal dependence of the effect of the LGM on population dynamics. Sado Island haplotypes exhibited a network with a star-shaped pattern and a 10,000-year-old expansion signal, surrounded by a Honshu haplotype cluster with a 15,000-year-old expansion signal, suggesting that post-LGM expansion events contributed to the formation of the Sado population. A reanalysis of Cytb sequences of the Japanese hare (Lepus brachyurus), which has a similar geographic range to the voles, yielded results that were consistent with those of the vole analysis, confirming that the characteristics of the post-LGM expansion event were dependent on latitude, involved two successive expansion events, and enabled migration across deep straits. It seems reasonable to infer that the environmental changes that occurred during the warm periods following the LGM were a contributing factor in the expansion of the distribution range of newly emerged haplotype groups.

Centromeres are essential for chromosome segregation, yet they are among the most rapidly evolving regions of the genome. The mechanisms driving this rapid evolution of centromeric sequences are still not well understood. In this study, we identified the centromeric sequences of a wheat-infecting Pyricularia oryzae strain (Br48) using CENP-A chromatin immunoprecipitation followed by high-throughput sequencing. The Br48 centromeres range from 71 kb to 101 kb in length and are highly AT-rich (72.1-75.5%) and repeat-rich (63.4-85.0%). These regions are also enriched in H3K9me3 and 5-methylcytosine but depleted of H3K4me2 and H3K27me3. During the analysis of repetitive sequences in the Br48 centromere, we identified a stretch of approximately 530 bp that is tightly associated with centromeres in the Pyricularia fungus. We designated this element as the centromere-associated IR element (CenIR), as it often forms inverted repeat structures with two elements adjacent in reverse orientation. A comparison of putative centromere sequences across phylogenetically distinct P. oryzae strains suggests that changes in centromeric sequences are non-uniform across chromosomes and do not always align with the fungal phylogenetic relationships. Repeat-induced point mutation (RIP)-like CG to TA transitions likely accelerate base substitutions in the centromeres of Pyricularia fungi.

Maintenance DNA methylation is essential for the stable inheritance of epigenetic information in vertebrates. While DNMT1 has long been recognized as the principal maintenance methyltransferase, recent studies have shown that its activity critically depends on ubiquitin signaling. Specifically, the E3 ligase UHRF1 enables DNMT1 recruitment and activation at hemimethylated sites through dual monoubiquitylation of both replication-associated and histone substrates. These insights have revised classical models of maintenance methylation and revealed new layers of regulation involving chromatin context, histone modifications and nucleosome remodeling. In this review, we summarize the current understanding of the molecular mechanisms underlying DNMT1-mediated maintenance methylation, with a particular focus on ubiquitin-dependent pathways and their interplay with chromatin architecture.

A hemizygous 1.5-3.0-Mb microdeletion of human chromosome 22q11.2 with the loss of multiple genes including histone cell cycle regulator (HIRA) causes 22q11.2 deletion syndrome (22q11.2 DS), a common disorder with variable manifestations including congenital malformations affecting the heart, palate and kidneys in association with neurodevelopmental, psychiatric, endocrine and autoimmune abnormalities. The aim of this study was to develop a TaqMan-based dosage analysis PCR (TaqMan qPCR) for use as a rapid, cost-effective test for clinically suspected patients fulfilling previously described criteria for molecular diagnosis of 22q11.2 DS in a lower middle-income country where the cost of testing limits its use in routine clinical practice. Nineteen patients were recruited with informed consent following ethical approval from the Ethics Review Committee, Lady Ridgeway Hospital for Children, Colombo. Dosage analysis of extracted DNA was performed using a TaqMan qPCR assay by amplifying regions within the target (HIRA) and control (testin LIM domain protein (TES)) genes of suspected patient (P) and unaffected person (N) samples. For detection of a deletion, the normalized value (HIRA/TES dosage) of a P sample was compared with that of an N sample. A ratio of P:N of 0.5 confirmed the presence of a deletion while a ratio of 1.0 refuted this. Seven of the 19 patients were found to have a HIRA deletion, confirming the diagnosis of 22q11.2 DS, with these results being in complete agreement with those of fluorescence in situ hybridization (FISH) (performed in nine of the 19 cases) and whole-exome sequencing (all 19 samples tested). This TaqMan qPCR assay was able to reliably distinguish HIRA-deleted cases from non-deleted ones. The assay was both cheaper and faster compared to commercially available alternatives in our setting, including FISH and multiple ligation-dependent probe amplification.

Ancient dispersal events from the Korean Peninsula to the Japanese main islands of Honshu, Shikoku and Kyushu (HSK), and from the Eurasian continent to Hokkaido via Sakhalin, have played a critical role in shaping the mammalian diversity of the Japanese archipelago. However, the timing and dynamics of these events remain incompletely understood across different taxa. In addition, the 100,000-year climatic cycles of glacial and interglacial periods during the Middle and Late Quaternary likely influenced intraspecific genetic diversity, although the mechanisms driving these changes remain unclear. In this study, we analyzed mitochondrial cytochrome b gene sequences from Japanese shrews (Sorex and Crocidura) and other small mammals from HSK and Hokkaido. Using an evolutionary rate of 0.029 substitutions/site/million years, we inferred that ancestral lineages of HSK species diverged during critical periods in the early Quaternary, such as around 2.4 and 1.7 million years ago (Ma), potentially in response to major climatic transitions. Notably, dispersal events of the Laxmann's shrew (S. caecutiens) and dark red-backed vole (Myodes rex) into Hokkaido around 1.7 Ma were also suggested. Regarding intraspecific mitochondrial DNA (mtDNA) lineages, species with broad distributions in HSK typically exhibit a north-south structure, characterized by two major lineages, as well as additional ancient lineages in surrounding offshore islands. Comparative analysis revealed that divergence among these lineages occurred at approximate intervals of 100,000 years. Our results indicate that the mtDNA genetic structure of HSK small mammals reflects geographic substructures shaped by climate-driven dispersal. Regions that facilitated rapid expansion during favorable climatic periods likely acted as centers of dispersal, from which haplotypes spread toward peripheral areas. As haplotypes radiated outward from these core regions, distinct mtDNA lineages became established across different geographic zones, giving rise to the spatial distribution patterns observed today.