Chromosomal Variation Research Articles

The location and genome origin of alien chromatin in wheat founder parent Xiaoyan 6.

The location of alien chromatin in Xiaoyan 6 was identified using mc-GISH analysis, genetic mapping and whole genome re-sequencing, and its possible origin was discussed. As a founder parent, Xiaoyan 6 has played an important role in distant hybridization breeding in China. Although it came from the cross between common wheat and Thinopyrum ponticum (Podp.) Barkworth and D.R. Dewey, the location of its alien chromatin has not been determined using traditional genomic in situ hybridization (GISH). In the present study, chromosome variation in Xiaoyan 6 was discovered by multicolor GISH analysis. Four alien-specific markers were developed by specific-locus amplified fragment sequencing technique. Their amplified sequences were analyzed by basic local alignment search tool with the reference genome sequences of common wheat Chinese Spring (CS) and Th. elongatum, and the whole genome re-sequencing reads of Th. ponticum and CS. Furthermore, the four markers were mapped on three different chromosomes in two RIL populations. By dissecting the mapped reads depth of the whole genome re-sequencing of Xiaoyan 6, we found that the depth of nine chromosome regions was obviously lower than the average. Among these, three regions on 1A, 3A and 7B were demonstrated as the alien introgressions in Xiaoyan 6 by multiple methods. Finally, the genetic transmission of the alien chromatin was analyzed in a set of wheat-Th. ponticum introgression lines. Some stable QTLs for morphological and physiological traits have been mapped near the alien chromatin.

A novel compound heterozygous mutation in the DYNC2H1 gene in a Chinese family with Jeune syndrome

BackgroundThe dynein cytoplasmic two heavy chain 1 (DYNC2H1) gene encodes a cytoplasmic dynein subunit. Cytoplasmic dyneins transport cargo towards the minus end of microtubules and are thus termed the “retrograde” cellular motor. Mutations in DYNC2H1 are the main causative mutations of short rib-thoracic dysplasia syndrome type III with or without polydactyly (SRTD3). Early diagnosis of SRTD3 prenatally by ultrasound alone is difficult. In this case, a couple who gave birth to three consecutive babies with SRTD3 requested fertility guidance to avoid having another baby with SRTD3.MethodsCytogenetic and molecular genetic analyses of amniotic fluid via whole-genome sequencing (WGS), routine G-banded karyotype analysis, fluorescent quantitative polymerase chain reaction, and whole-exome sequencing (WES) were performed at 19 weeks. Peripheral blood samples from the parents were also screened by Sanger sequencing for SRTD3-related mutations.ResultsTwo compound heterozygous mutations, c.10,594 C > T and c.7720G > A, in the DYNC2H1 gene were identified, which were inherited from the mother and father, respectively. The foetus’s mother is heterozygous for the c.10,594 C > T variant, and the foetus’s father is heterozygous for the c.7720G > A variant. The mutation c.10,594 C > T, which is a nonsense mutation believed to be pathogenic, has been previously reported. The mutation c.7720G > A, which is a missense mutation, has yet to be reported. Moreover, no chromosomal abnormalities or pathogenic copy number variations (CNVs) were detected in the foetus. The patient did not become pregnant after PGT-M and IVF-ET. This family subsequently accepted donated eggs; a successful pregnancy occurred, and a healthy girl was born.ConclusionThe compound heterogeneous mutations in DYNC2H1 ultimately accounts for the diversity of disease phenotypes reported in this study and can be used to guide future pregnancies. Our findings expand the mutation spectrum of DYNC2H1 in this rare disease and highlight the value of WES in the diagnosis of skeletal dysplasia with unclear prenatal indications.

Application of copy number variation sequencing combined with whole exome sequencing in prenatal left–right asymmetry disorders

BackgroundLeft–right (LR) asymmetry disorders present a complex etiology, with genetic factors emerging as a primary contributor. This study aims to explore the genetic underpinnings of chromosomal variants and individual genes in fetuses afflicted with prenatal LR asymmetry disorder.MethodsThrough a retrospective analysis conducted between 2020 and 2023 at Tongji Hospital, Huazhong University of Science and Technology, genetic outcomes of LR asymmetric disorder were scrutinized utilizing copy number variation sequencing (CNV-seq) and whole exome sequencing (WES) methodologies.ResultsWith a combination of CNV-seq and WES, 5 fetuses in 17 patients with LR asymmetry had chromosomal or genetic variants. CNV-seq revealed a 16p11.2 microdeletion syndrome in a situs inversus fetus presenting pathogenic and a 2q36.3 microduplication syndrome in a fetus with Heterotaxy presenting a variant of uncertain significance (VUS). WES identified NM_198075.4:c.755del in the LRRC56 gene and NM_001454.4:c.865_868dup in the FOXJ1 gene in two situs inversus cases, along with two variants in DNAH5 in two other fetuses. Further bioinformatics scrutiny was conducted to assess the protein structure and function prediction of these variants, ultimately indicating their potential pathogenicity.ConclusionThe study highlights that fetuses with LR asymmetric disorders may have copy number variants, underscoring the significance of mutations in LRRC56 and FOXJ1 in the development of LR asymmetry disorders.

Karyotype variation patterns and phenotypic responses of hybrid progenies of triploid loquat (Eriobotrya japonica) provide new insight into aneuploid germplasm innovation

Abstract The sexual reproduction of triploids induces chromosomal karyotype variations, which are significant for germplasm resource innovation. Most triploid plants are with low fertility. Therefore, triploid offspring karyotypes’ variation pattern and phenotypic response remain poorly understood. Here, we employed three diploids with diverse genetic distances as male parents to cross-pollinate the female fertile triploid loquat Q24 to construct three experimental populations. The chromosome numbers of 93.82% of hybrid plants were 34~46 in three hybrid populations. All 168 aneuploids with 160 karyotypes and a small percentage of euploids were detected among 178 hybrids by the improved molecular karyotype analysis method. Further analysis revealed that when being transmitted to offspring, chromosome 5 of Q24 as disomy was with the highest frequency (> 50%), while chromosome 12 was with the lowest frequency (≤ 30%). The frequency of Q24’s chromosomes being transmitted to offspring as disomy was influenced by the gene function on the chromosomes and the number of inter-chromosome collinear gene links. Whole genome resequencing showed that the Q24 alleles exhibited segregation distortions in the offspring aneuploid population. Transgenic experiments demonstrated that the EjRUN1 gene, which was on one segregation distortion region of Q24, promoted the seed viability of triploid Arabidopsis. Furthermore, chromosome number, dosage, and male parent genotype affected the aneuploid phenotype. These findings advance the understanding of genome genetic characteristics of triploid loquat, and provide a reference for germplasm innovation of loquat rapidly through triploid sexual reproduction.

Genomic, transcriptomic, and T cell receptor profiling in stratifying response to first-line chemoradiotherapy or radiotherapy for esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) accounts for 80% of esophageal cancer (EC) worldwide. The molecular characteristics of locally advanced ESCC have been extensively studied. In this study, we investigate the genomic and transcriptomic characteristics and try to provide the basic T-cell receptors (TCRs) dynamics and its genomic and transcriptome association during the radiochemotherapy of ESCC using multi-omics analysis. A total of 23 patients with pathologic diagnoses of locally advanced ESCC were enrolled. The median tumor mutational burden (TMB) of the 23 ESCC patients were 3.47 mutations/ Mb (mega-base). The TP53, RTK/RAS, and NOTCH pathways were concurrently prevalent in ESCC. Besides, some less prevalent pathways, including WNT and HIPPO pathways also exhibited superior frequencies in ESCC. Meantime, we found the immune-hot tumor had higher immune infiltration scores. The median TMB in the progression-free survival (PFS) low group was significantly higher than that in the PFS-high group. The chromosomal copy number variation (CNV) burden of the neutrophil-to-lymphocyte ratio (NLR)-high group appeared to be higher than that of the NLR-low group, and the StromalScore in the NLR-low group was significantly higher. Clonality score was significantly increased from pre-treat to post-treat and from on-treat to post-treat. Shannon index was significantly decreased from pre-treat to post-treat and from on-treat to posttreat. Richness was significantly decreased from pre-treat to post-treat. Multiomics analysis provided the basic TCRs dynamics and their genomic and transcriptome association during the radio-chemotherapy of 23 locally advanced ESCC in China, and provided a valuable insights into the heterogeneity and the tumor microenvironment and treatment responses. Meantimes, the identification of biomarkers and the exploration of their association with treatment outcomes could have important implications for clinical practice.

Trajectory of human migration: insights from autosomal and non-autosomal variant clustering patterns

Genetic variations present in the Y chromosomal and mitochondrial DNA provide the mole-cular basis to support the archeological and anthropological evidence that formulates the theories for describing the trajectory of human migration, which started almost 200,000 years ago out of Africa. These genetic variations have long been used as ancestry informative markers (AIMs) in forensics and evolutionary studies, primarily because of their uniparental inheritance and lack of recombination, despite the fact that gender-specific gene flow and socio-cultural practices may cause discrepancies. Moreover, the genetic markers on the Y chromosome constitute only a minor fraction of the entire human genome. Here, we analyzed over 75 million genetic variants (single nucleotide variants (SNVs) and short insertion-deletion (InDels)) within consecutive 2500000 base pair windows in the autosomal as well as non-autosomal chromosomes of 22 populations in four major geographic regions that are cataloged in the 1000 Genomes Project to understand the clustering patterns of the autosomal and non-autosomal variants. While autosomal and X-chromosomal variants cluster the populations of similar geographic regions together, Y-chromosomal variants constantly place the East Asian Japanese and the European Finnish populations in a single clade in hierarchical clusters. This comprehensive genome-wide analysis essentially introduces new insights into mapping the path of human migration based on the Y-chromosomal and other chromosomal variants.

From Natural Hosts to Agricultural Threats: The Evolutionary Journey of Phytopathogenic Fungi.

Since the domestication of plants, pathogenic fungi have consistently threatened crop production, evolving genetically to develop increased virulence under various selection pressures. Understanding their evolutionary trends is crucial for predicting and designing control measures against future disease outbreaks. This paper reviews the evolution of fungal pathogens from natural habitats to agricultural settings, focusing on eight significant phytopathogens: Pyricularia oryzae, Botrytis cinerea, Puccinia spp., Fusarium graminearum, F. oxysporum, Blumeria graminis, Zymoseptoria tritici, and Colletotrichum spp. Also, we explore the mechanism used to understand evolutionary trends in these fungi. The studied pathogens have evolved in agroecosystems through either (1) introduction from elsewhere; or (2) local origins involving co-evolution with host plants, host shifts, or genetic variations within existing strains. Genetic variation, generated via sexual recombination and various asexual mechanisms, often drives pathogen evolution. While sexual recombination is rare and mainly occurs at the center of origin of the pathogen, asexual mechanisms such as mutations, parasexual recombination, horizontal gene or chromosome transfer, and chromosomal structural variations are predominant. Farming practices like mono-cropping resistant cultivars and prolonged use of fungicides with the same mode of action can drive the emergence of new pathotypes. Furthermore, host range does not necessarily impact pathogen adaptation and evolution. Although halting pathogen evolution is impractical, its pace can be slowed by managing selective pressures, optimizing farming practices, and enforcing quarantine regulations. The study of pathogen evolution has been transformed by advancements in molecular biology, genomics, and bioinformatics, utilizing methods like next-generation sequencing, comparative genomics, transcriptomics and population genomics. However, continuous research remains essential to monitor how pathogens evolve over time and to develop proactive strategies that mitigate their impact on agriculture.

Oligo-FISH barcode chromosome identification system provides novel insights into the natural chromosome aberrations propensity in the autotetraploid cultivated alfalfa.

Alfalfa is one of the most economically valuable forage crops in the world. However, molecular cytogenetic studies in alfalfa lag far behind other cash crops and have reached a bottleneck. Here, we developed a novel chromosome identification system by designing 21 oligo probes in specific regions of each chromosome, which can be used as a barcode to simultaneously distinguish all chromosomes in a cell. Using this system, we revealed the chromosome karyotype features and evolutionary differences among 10 cultivated alfalfa varieties. Interestingly, we also found two chromosomal variation types, i.e. aneuploidy and large chromosomal segment deletions in the seeds of three alfalfa varieties. Variation frequency analysis showed that only 7/173 seeds in those three alfalfa varieties had chromosome aberrations, which indicated that the inheritance and meiosis of alfalfa had evolved to a relatively stable state. Remarkably, 4/7 variation seeds were chromosome 2 aberrations, suggesting that chromosome 2 appears to be more susceptible to natural chromosomal aberrations than other chromosomes during inheritance. DNA sequence variation analysis showed that the difference of presence and absence variations (PAVs) among homologous copies of chromosome 2 was larger than that of the other seven chromosomes. We suggest that such large PAV divergence among homologous copies may provide the physical basis for natural chromosome 2 aberrations propensity. Our study provides a valuable and efficient tool for alfalfa's molecular cytogenetics and sheds new insights into the propensity for natural chromosome aberrations during autopolyploid inheritance.

Genome alteration of Leishmania orientalis under Amphotericin B inhibiting conditions.

Amphotericin B (AmB) is a potent antifungal and antiparasitic medication that exerts its action by disrupting the cell membrane of the leishmanial parasite, leading to its death. Understanding the genetic alterations induced by Amphotericin B is crucial for gaining insights into drug resistance mechanisms and developing more effective treatments against Leishmania infections. As a new Leishmania species, the molecular response of Leishmania orientalis to anti-leishmanial drugs has not been fully explored. In this study, Leishmania orientalis strain PCM2 culture was subjected to AmB exposure at a concentration of 0.03 uM over 72 hours compared to the control. The genomic alteration and transcriptomic changes were investigated by utilising the whole genome and RNA sequencing methods, followed by the analysis of single nucleotide polymorphisms (SNPs), differential gene expression, and chromosomal copy number variations (CNVs) assessed using read depth coverage (RDC) values across the entire genome. The chromosomal CNV analysis showed no significant difference between L. orientalis from the control and AmB-treated groups. The distribution of SNPs displayed notable variability, with higher SNP incidence in the control group compared to the AmB-treated group. Gene ontology analysis unveiled functions of the SNPs -associated genes involved in transporter function, genetic precursor synthesis, and purine nucleotide metabolism. Notably, the impact of AmB treatment on the L. orientalis gene expression profiles exhibited diverse expressional alterations, particularly the downregulation of pivotal genes such as the tubulin alpha chain gene. The intricate interplay between SNPs and gene expression alterations might underscore the complex regulatory networks underlying the AmB resistance of L. orientalis strain PCM2.

Mechanisms, Machinery, and Dynamics of Chromosome Segregation in Zea mays.

Zea mays (maize) is both an agronomically important crop and a powerful genetic model system with an extensive molecular toolkit and genomic resources. With these tools, maize is an optimal system for cytogenetic study, particularly in the investigation of chromosome segregation. Here, we review the advances made in maize chromosome segregation, specifically in the regulation and dynamic assembly of the mitotic and meiotic spindle, the inheritance and mechanisms of the abnormal chromosome variant Ab10, the regulation of chromosome-spindle interactions via the spindle assembly checkpoint, and the function of kinetochore proteins that bridge chromosomes and spindles. In this review, we discuss these processes in a species-specific context including features that are both conserved and unique to Z. mays. Additionally, we highlight new protein structure prediction tools and make use of these tools to identify several novel kinetochore and spindle assembly checkpoint proteins in Z. mays.

Proband-Only Exome Sequencing for Intellectual Disability in Iran: Diagnostic Yield and Genetic Insights.

Intellectual disability (ID) is a leading cause for referral to genetic services, with the most severe cases typically attributed to single genetic defects. This study aimed to evaluate the diagnostic yield of cost-effective proband-only exome sequencing for individuals diagnosed with ID within the Iranian population for the first time where a high rate of parental consanguinity exists. A total of 99 unrelated patients with ID were investigated by exome sequencing during 8 years. As a result, 43 pathogenic/likely pathogenic variants were identified in 40 patients, indicating a molecular diagnostic rate of 40.4% (40/99). The inclusion of five chromosomal copy number variations in the subsequent analysis increased the diagnostic rate of proband-only exome sequencing to 45.4% (45/99). Additionally, parental testing revealed five de novo variants. This contributed to a total diagnostic rate of 50.5% (50/99). In our study, proband-only exome sequencing achieved a remarkable diagnostic rate, identifying nearly half of the ID cases. This rate of diagnosis could be primarily attributed to prevalent consanguineous marriage in the Iranian population and the rare identification of de novo variants. With the ongoing advancements in neurogenetics, proband-only exome sequencing demonstrates significant potential as a future cost-effective diagnostic approach in Iran.

Chromosome X-wide common variant association study in autism spectrum disorder.

Autism spectrum disorder (ASD) displays a notable male bias in prevalence. Research into rare (<0.1) genetic variants on the X chromosome has implicated over 20 genes in ASD pathogenesis, such as MECP2, DDX3X, and DMD. The "female protective effect" in ASD suggests that females may require a higher genetic burden to manifest symptoms similar to those in males, yet the mechanisms remain unclear. Despite technological advances in genomics, the complexity of the biological nature of sex chromosomes leaves them underrepresented in genome-wide studies. Here, we conducted an X-chromosome-wide association study (XWAS) using whole-genome sequencing data from 6,873 individuals with ASD (82% males) across Autism Speaks MSSNG, Simons Simplex Collection (SSC), and Simons Powering Autism Research (SPARK), alongside 8,981 population controls (43% males). We analyzed 418,652 X chromosome variants, identifying 59 associated with ASD (p values 7.9×10-6 to 1.51×10-5), surpassing Bonferroni-corrected thresholds. Key findings include significant regions on Xp22.2 (lead SNP rs12687599, p= 3.57×10-7) harboring ASB9/ASB11 and another encompassing DDX53 and the PTCHD1-AS long non-coding RNA (lead SNP rs5926125, p= 9.47×10-6). When mapping genes within 10 kb of the 59 most significantly associated SNPs, 91 genes were found, 17 of which yielded association with ASD (GRPR, AP1S2, DDX53, HDAC8, PCDH19, PTCHD1, PCDH11X, PTCHD1-AS, DMD, SYAP1, CNKSR2, GLRA2, OFD1, CDKL5, GPRASP2, NXF5, and SH3KBP1). FGF13 emerged as an X-linked ASD candidate gene, highlighted by sex-specific differences in minor allele frequencies. These results reveal significant insights into X chromosome biology in ASD, confirming and nominating genes and pathways for further investigation.

Neo-Sex Chromosome Evolution in Treehoppers Despite Long-Term X Chromosome Conservation.

Sex chromosomes follow distinct evolutionary trajectories compared to the rest of the genome. In many cases, sex chromosomes (X and Y or Z and W) significantly differentiate from one another resulting in heteromorphic sex chromosome systems. Such heteromorphic systems are thought to act as an evolutionary trap that prevents subsequent turnover of the sex chromosome system. For old, degenerated sex chromosome systems, chromosomal fusion with an autosome may be one way that sex chromosomes can "refresh" their sequence content. We investigated these dynamics using treehoppers (hemipteran insects of the family Membracidae), which ancestrally have XX/X0 sex chromosomes. We assembled the most complete reference assembly for treehoppers to date for Umbonia crassicornis and employed comparative genomic analyses of 12 additional treehopper species to analyze X chromosome variation across different evolutionary timescales. We find that the X chromosome is largely conserved, with one exception being an X-autosome fusion in Calloconophora caliginosa. We also compare the ancestral treehopper X with other X chromosomes in Auchenorrhyncha (the clade containing treehoppers, leafhoppers, spittlebugs, cicadas, and planthoppers), revealing X conservation across more than 300 million years. These findings shed light on chromosomal evolution dynamics in treehoppers and the role of chromosomal rearrangements in sex chromosome evolution.

Rapid Sex Chromosome Turnover in African Clawed Frogs (Xenopus) and the Origins of New Sex Chromosomes.

Sex chromosomes of some closely related species are not homologous, and sex chromosome turnover is often attributed to mechanisms that involve linkage to or recombination arrest around sex-determining loci. We examined sex chromosome turnover and recombination landscapes in African clawed frogs (genus Xenopus) with reduced representation genome sequences from 929 individuals from 19 species. We recovered extensive variation in sex chromosomes, including at least eight nonhomologous sex-associated regions-five newly reported here, with most maintaining female heterogamety, but two independent origins of Y chromosomes. Seven of these regions are found in allopolyploid species in the subgenus Xenopus, and all of these reside in one of their two subgenomes, which highlights functional asymmetry between subgenomes. In three species with chromosome-scale genome assemblies (Xenopus borealis, Xenopus laevis, and Xenopus tropicalis), sex-specific recombination landscapes have similar patterns of sex differences in rates and locations of recombination. Across these Xenopus species, sex-associated regions are significantly nearer chromosome ends than expected by chance, even though this is where the ancestral recombination rate is highest in both sexes before the regions became sex associated. As well, expansions of sex-associated recombination arrest occurred multiple times. New information on sex linkage along with among-species variation in female specificity of the sex-determining gene dm-w argues against a "jumping gene" model, where dm-w moves around the genome. The diversity of sex chromosomes in Xenopus raises questions about the roles of natural and sexual selection, polyploidy, the recombination landscape, and neutral processes in driving sex chromosome turnover in animal groups with mostly heterogametic females.

Mosaic variegated aneuploidy in development, ageing and cancer.

Mosaic variegated aneuploidy (MVA) is a rare condition in which abnormal chromosome counts (that is, aneuploidies), affecting different chromosomes in each cell (making it variegated) are found only in a certain number of cells (making it mosaic). MVA is characterized by various developmental defects and, despite its rarity, presents a unique clinical scenario to understand the consequences of chromosomal instability and copy number variation in humans. Research from patients with MVA, genetically engineered mouse models and functional cellular studies have found the genetic causes to be mutations in components of the spindle-assembly checkpoint as well as in related proteins involved in centrosome dynamics during mitosis. MVA is accompanied by tumour susceptibility (depending on the genetic basis) as well as cellular and systemic stress, including chronic immune response and the associated clinical implications.

Investigation of chromosomal anomalies and copy number variations in children diagnosed with autism spectrum disorder by array CGH method.

This study aimed to identify the chromosomal anomalies and copy number variations (CNVs) in autism spectrum disorder (ASD) and to provide genotype/phenotype correlations. Fifty-four patients diagnosed with ASD between March 2021 and June 2022 were included in the study. Patients were evaluated by cytogenetic analysis and array comparative genomic hybridisation analysis (aCGH). The structural and numerical chromosomal anomaly was detected in 3.7%, and the CNVs were identified in 18.52% of patients. Of the CNVs detected, 27.3% were identified as pathogenic, 18.2% as likely pathogenic and 54.5% as VUS. The copy number gain rate of the detected CNVs was higher than the copy number losses rate, 70% and 30% respectively. As an important finding in the study, a new pathogenic CNV with a 6.3-mb copy number gain in the 3p22.3p22.2 region, whose gene region had not been previously defined in OMIM, was detected. Identifying a genetic aetiology may provide clinicians with more information about disease prognosis and risk of recurrence.

Preimplantation genetic testing for inborn errors of metabolism: observations from a reproductive genetic laboratory in China.

In this study, we aimed to apply preimplantation genetic testing for monogenic disorders (PGT-M) based on mutated allele revealed by sequencing with aneuploidy and linkage analyses (MARSALA) to block the transmission of inborn errors of metabolism (IEMs). After the disease-causing variants were identified through genetic testing, four carrier couples having children affected with IEMs, including methylmalonic aciduria, glutaric acidemia type 1, beta-ketothiolase deficiency, and ornithine transcarbamylase deficiency, sought PGT-M. A series of PGT procedures involving intracytoplasmic sperm injection, blastocyst culture, biopsy of trophectoderm cells, and next-generation sequencing (NGS)-based MARSALA, was performed to provide comprehensive chromosome screening and variant gene analysis. Finally, embryos were selected for transfer, and prenatal diagnosis was conducted to confirm the PGT-M results. All four carrier couples obtained transferrable embryos after PGT. The results of the prenatal diagnosis were consistent with the PGT results, and all couples gave birth to healthy babies free of IEMs. The results of this study confirm that NGS-based MARSALA is an effective approach for families with IEMs to prevent the subsequent transmission of pathological genetic variants to the next generation.

Genetic analysis of 280 children with unexplained developmental delay or intellectual disability using whole exome sequencing

IntroductionDevelopmental delay (DD) and intellectual disability (ID) are key manifestations of neurodevelopmental disorders (NDDs), characterized by considerable clinical and genetic variability, which complicates genetic diagnosis. Whole exome sequencing (WES) has become an effective method for uncovering genetic causes in patients with unexplained DD/ID.MethodsWe retrospectively analyzed WES data from 280 patients diagnosed with unexplained DD/ID. Demographic information and genetic variants identified through WES were assessed, along with an evaluation of clinical factors that might influence the detection of genetic causes.ResultsPathogenic variants were detected in 73 cases (36.07%), including 25 cases involving pathogenic chromosomal copy number variations. Clinical factors such as age, sex, gestational age, birth weight, anoxia, jaundice, associated symptoms, family history, muscle strength, muscle tone, epilepsy, brain MRI findings, EEG results, and the severity of DD/ID did not significantly impact the WES outcomes. However, a significant correlation was observed between delivery mode and positive WES results, with a higher diagnostic yield among patients delivered via caesarean section.ConclusionsWES is a valuable approach for identifying genetic causes in patients with unexplained DD/ID, providing benefits for patient management, family genetic counseling, and long-term prognosis assessment.Clinical trial numberNot applicable.

Phylogenomics resolves key relationships in Rumex and uncovers a dynamic history of independently evolving sex chromosomes

Abstract Sex chromosomes have evolved independently many times across eukaryotes. Despite a considerable body of literature on sex chromosome evolution, the causes and consequences of variation in their formation, degeneration, and turnover remain poorly understood. Chromosomal rearrangements are thought to play an important role in these processes by promoting or extending the suppression of recombination on sex chromosomes. Sex chromosome variation may also contribute to barriers to gene flow, limiting introgression among species. Comparative approaches in groups with sexual system variation can be valuable for understanding these questions. Rumex is a diverse genus of flowering plants harboring significant sexual system and karyotypic variation, including hermaphroditic and dioecious clades with XY (and XYY) sex chromosomes. Previous disagreement in the phylogenetic relationships among key species has rendered the history of sex chromosome evolution uncertain. Resolving this history is important for investigating the interplay of chromosomal rearrangements, introgression, and sex chromosome evolution in the genus. Here, we use new transcriptome assemblies from 11 species representing major clades in the genus, along with a whole-genome assembly generated for a key hermaphroditic species. Using phylogenomic approaches, we find evidence for the independent evolution of sex chromosomes across two major clades, and introgression from unsampled lineages likely predating the formation of sex chromosomes in the genus. Comparative genomic approaches revealed high rates of chromosomal rearrangement, especially in dioecious species, with evidence for a complex origin of the sex chromosomes through multiple chromosomal fusions. However, we found no evidence of elevated rates of fusion on the sex chromosomes in comparison with autosomes, providing no support for an adaptive hypothesis of sex chromosome expansion due to sexually antagonistic selection. Overall, our results highlight a complex history of karyotypic evolution in Rumex, raising questions about the role that chromosomal rearrangements might play in the evolution of large heteromorphic sex chromosomes.

Abstract 4136501: Machine Learning Uncovers the Contribution of Rare Genetic Variants and Enhances Risk Prediction for Coronary Artery Disease in the Japanese Population

Background: Genome-wide association studies (GWASs) have enhanced our understanding of the genetic basis of coronary artery disease (CAD), and polygenic risk scores (PRSs) have facilitated the assessment of genetic risk. However, these methods predominantly focus on common variants due to statistical power, potentially leaving rare variants insufficiently analyzed and thus limiting the predictive performance of PRS. Methods: We conducted whole genome sequencing (WGS) of 1,752 Japanese early-onset myocardial infarction (MI) patients and 3,019 controls from Biobank Japan (BBJ). We performed case-control association studies including GWAS and gene-based tests, as well as a novel machine learning-based framework. In this framework, we developed a penalized regression model to predict the CAD status from genome-wide rare nonsynonymous variants. The model identified the minimal set of most distinguishing features (genes) and generated a rare variant-based risk score (RVS). The RVS was evaluated on an independent validation WGS cohort of 200 cases and 824 controls. We also derived a PRS based on CAD-GWAS (25,668 CAD cases vs 141,667 controls from BBJ) to compare the properties and performance between the RVS and PRS. Results: In the case-control studies, only two common variants in chromosome 12 were identified in GWAS, with no genes in gene-based analysis (SKAT-O), suggesting the challenges in rare variant analysis. On the other hand, our machine-learning framework identified 59 CAD-related genes, including LDLR , a causal gene of familial hypercholesteremia. Functional analyses revealed that various biological pathways, including lipid metabolism, immune system, and vessel development, are involved in CAD. For the genetic risk prediction, RVS significantly predicted CAD (area under the curve [AUC], 0.58; p=0.001, pseudo-R 2 , 0.051; p=7.92*10 -9 ). RVS was significantly associated with LDL cholesterol levels and coagulation function (Pearson’s r, 0.21; p=4.5*10 -5 and 0.10; p=0.03, respectively) and MI patients with high RVS (top 5%) showed higher cardiovascular mortality rate (p=0.03, log-rank test), highlighting the clinical importance of RVS. Finally, the combined risk score (CRS) of RVS and PRS significantly improved CAD prediction compared to PRS (AUC, 0.66 (CRS) vs 0.61 (PRS); p=0.007, pseudo-R 2 , 0.093 (CRS) vs 0.040 (PRS); p=0.0018, Figure ). Conclusions: Our machine learning framework successfully characterized rare variants and enhanced genetic risk prediction in CAD.