Search Results (606)

Background: Intellectual disability (ID) is a heterogeneous condition caused by diverse genetic factors, including single-nucleotide variants (SNVs) and copy number variants (CNVs). Whole-exome sequencing (WES) and clinical exome sequencing (CES) have become essential tools for identifying pathogenic variants; however, their relative diagnostic performance in ID has not been fully characterized. Methods: Children diagnosed with ID or related neurodevelopmental disorders underwent WES or CES. Identified variants were classified according to ACMG/AMP and ClinGen guidelines, with segregation analysis performed when parental samples were available. Diagnostic yields were compared across demographic, prenatal, and phenotypic subgroups. A multidimensional semi-quantitative scoring system encompassing 15 clinical domains (e.g., age at onset, neuro-motor function, seizures, MRI findings, vision, and dysmorphic features) was developed. Z-scores were calculated for each parameter, followed by hierarchical cluster analysis (HCA) and correlation modeling to define genotype–phenotype associations and pathway-level clustering. Results: A broad spectrum of pathogenic and likely pathogenic variants across multiple genes and biological pathways was identified in our study. CNV-associated cases frequently exhibited prenatal anomalies or multisystem phenotypes associated with large chromosomal rearrangements. Monogenic variants and their corresponding phenotypic profiles were identified through clinical exome sequencing (CES) and whole-exome sequencing (WES). Phenotypic HCA based on Z-scores revealed three major biological groups of patients with coherent genotype–phenotype relationships: Group 1, severe multisystem neurodevelopmental disorders dominated by transcriptional and RNA-processing genes (POLR1C, TCF4, HNRNPU, NIPBL, ACTG1); Group 2, intermediate epileptic and metabolic forms associated with ion-channel and excitability-related genes (SCN2A, PAH, IQSEC2, GNPAT); and Group 3, milder or focal neurodevelopmental phenotypes involving myelination and signaling-related genes (NKX6-2, PLP1, PGAP3, SMAD6, ATP1A3). Gene distribution significantly differed among these biological categories (χ² = 54.566, df = 34, p = 0.0141), confirming non-random, biologically consistent grouping. Higher Z-scores correlated with earlier onset and greater neurological severity, underscoring the clinical relevance of the multidimensional analytical framework. Conclusions: This study highlights the genetic complexity and clinical heterogeneity of intellectual disability and demonstrates the superior diagnostic resolution of WES and CES. Integrating multidimensional phenotypic profiling with genomic analysis enhances genotype–phenotype integration and enables data-driven phenotype stratification and pathway-based re-analysis. This combined diagnostic and analytical framework offers a more comprehensive approach to diagnosing monogenic ID and provides a foundation for future predictive and functional studies. Full article

Acute myeloid leukemia (AML) is an aggressive clonal hematopoietic malignancy, characterized by marked biological heterogeneity and variable clinical outcomes. Among its rarer genetic subsets is AML with rearrangements of the MDS1 and EVI1 complex locus (MECOM), occurring in fewer than 2% of newly diagnosed cases. This review examines the biology and clinical significance of MECOM-rearranged AML, with a focus on its diverse mechanisms of leukemogenesis, including chromosomal inversion and translocation involving 3q26. We discuss how aberrant EVI1/MECOM activity alters gene expression networks and drives malignant transformation. Current therapeutic approaches—including intensive chemotherapy, hypomethylating agents in combination with venetoclax, and allogeneic stem cell transplantation—are evaluated with particular emphasis on inv(3) and other t(3q26) subtypes. Despite these treatment strategies, outcomes remain poor, underscoring the urgent need for novel, more effective therapies for this high-risk form of AML. Full article

In Lolium perenne, a novel growth habit mutant, named VIROIZ, was recovered following colchicine treatment, and it was confirmed to maintain the diploid chromosome number (2n = 2x = 14). The mutation affected the stem morphology by inducing prolific axillary shoot formation at nodal zones, resulting in a spreading growth habit that can extend to ~70 cm in width. Inheritance analysis based on single-plant evaluations in crosses with wild-type plants (F₁, n = 285; F₂, n = 380) and in selfed progeny (S₁, n = 255) consistently showed ~40% expression of the spreading phenotype, deviating from classical Mendelian ratios and indicating complex genetic control. Phenotypic selection further distinguished divergent classes: positively selected lines (C1⁺) averaged 3.90 axillary tillers per stem, whereas negatively selected lines (C1⁻) averaged only 0.22. Partial sequencing of 11 candidate genes implicated in shoot architecture, covering 40–90% of full-length DNA, did not provide a conclusive explanation for the altered stem growth. Notably, a single point mutation was observed in CRT3 (an endoplasmic reticulum chaperone that interacts with brassinosteroid signaling) highlighting it as a primary target for future studies. Cytological analysis of meiosis in F₁ hybrids between VIROIZ and wild-type plants revealed irregular chromosome pairing with persistent univalents (2–4 per cell), supporting the presence of structural chromosomal rearrangements that may disrupt gene organization and function in VIROIZ. The non-Mendelian segregation of the spreading phenotype, together with the observed meiotic irregularities, suggests that the mutation affects regulatory genes responsive to hormonal signals controlling axillary meristem initiation. The mutant represents a valuable resource for turf-type L. perenne breeding and for studying hormonal regulation of shoot morphogenesis in Poaceae. Full article

Gametogenesis is a fundamental biological process that ensures both genetic recombination and the continuity of successive generations. Interspecific hybrids can reproduce through modified mechanisms, such as hybridogenesis, by transmitting clonal, unrecombined genomes of only one of the parental species via their gametes. Pelophylax grafi (RP) is a natural hybrid frog composed of mixed genomes (subgenomes) of two related species, Pelophylax perezi (P) and Pelophylax ridibundus (R), and coexists in populations with P. perezi. This study tested the involvement of programmed genome elimination in gamete production of P. grafi, providing new insight into reproductive mechanisms of hybrid vertebrates. Using comparative genomic hybridization (CGH) and fluorescent in situ hybridization (FISH), we examined the genomic constitution of germline cells in tadpoles and adult male and female P. grafi. Controlled crosses between P. perezi and P. grafi produced F1 hybrid tadpoles, whose genotypes confirmed that P. grafi parents transmitted the R subgenome through their gametes. In the early germline cells (gonocytes) of these tadpoles, P chromosomes were selectively eliminated via micronuclei formation during interphase. The occasional presence of the R genome and mixed R/P genome micronuclei suggests variability and imperfect fidelity in the elimination process. In adult hybrids, the majority of diplotene oocytes, spermatogonial stem cells (SSC) and spermatocytes carried R subgenomes. We demonstrated that programmed genome rearrangement in Pelophylax hybrids is an evolutionarily conserved mechanism underlying this unique reproductive strategy. Full article

Stenotrophomonas maltophilia (S. maltophilia) is a multidrug-resistant opportunistic pathogen. There are an increasing number of case reports on S. maltophilia infections in recent years, and the species is becoming a public health concern. Many studies have focused on profiling and pangenome of the species, particularly on their antibiotic resistance and virulence genes. However, there is a lack of studies on mobile genetic elements (MGEs), a subset of pangenome that significantly contributes to the diversity, stability, and plasticity of a population. In this study, 20 genomes of S. maltophilia were downloaded from the NCBI Genome database. The genomes were subjected to profiling of MGEs, their impact on the population structures, and the evaluation of evolutionary trends of the core genomes. The cataloguing of MGEs indicated active horizontal gene transfer events in the S. maltophilia’s population. Multiple virulence and drug resistance genes were predicted within and outside of the MGEs. We observed multiple chromosomal rearrangements in the genomes, most likely caused by MGEs, affecting up to approximately 50% of a single genome sequence. A high number of linkage disequilibrium sites were also predicted in the core genomes. This study provides insights into stability in the core and plasticity in the accessory regions in the S. maltophilia population. Full article

Childhood cancer is rare, with about 1 in 260 children developing cancer before age 20. However, it remains a leading cause of death for children and adolescents worldwide. The 5-year survival rate for childhood cancer in high-income countries exceeds 80%, but globally, the average survival rate is around 37%, highlighting significant disparities across the globe. Despite the life-saving impact of current treatment regimens, long-term side effects and risks are always concerns. Therefore, there is a continuing urgent need for novel therapies to overcome the limitations of existing approaches and improve patient outcomes. Targeted drug therapies that interfere with cancer-causing genes play a vital role in cancer treatment by specifically targeting cancer cells. TFs are primary drivers of gene expression that are critical in various pediatric cancers. Chromosomal rearrangements, involving changes in chromosome structure such as deletions, duplications, inversions, and translocations, can significantly alter TF activity and downstream gene expression. Dysregulation of TFs disrupts gene expression networks and has been strongly linked to the development and progression of many pediatric cancers, making them promising therapeutic targets. Several approaches targeting TFs, including small-molecule inhibitors designed to block TF-DNA binding, TF-cofactor interactions, or their epigenetic regulation, as well as RNA interference, have been developed. More recently, approaches like PROTACs (Proteolysis-Targeting Chimeras) and molecular glue degraders offer new therapeutic possibilities in pediatric cancers. These innovations represent a paradigm shift in pediatric oncology, offering hope for more targeted, less toxic treatment options. This review discusses the critical role of TFs in childhood cancers and emphasizes the need for evolving therapeutic strategies aimed at targeting these key regulators to improve outcomes for young patients. Full article

Background: Ctenomys is a subterranean rodent genus known for exhibiting the highest levels of chromosome variation, both among species (2n = 10 to 70) and within species. Ctenomys minutus is particularly notable for its extensive chromosomal diversity, comprising the greatest number of described cytotypes within this genus. In contrast, Ctenomys lami presents the highest degree of karyotypic variation within a comparatively restricted geographic range. Both species inhabit the coastal plain of southern Brazil: C. minutus occurs in dunes and sandy fields extending from Laguna (Santa Catarina State) to São José do Norte (Rio Grande do Sul State), whereas C. lami is restricted to the “Coxilha das Lombas” region, which lies parallel to the distribution of C. minutus in Rio Grande do Sul State. Despite their close evolutionary relationship and the absence of external morphological differences, the mechanism underlying their karyotypic divergence remains poorly understood. Methods: In this study, we applied whole-chromosome painting using probes from Ctenomys flamarioni to investigate chromosomal evolution in C. minutus and C. lami. Results: The resulting homology maps revealed a variety of chromosomal rearrangements that differentiate cytotypes both within and between these species. Comparative analyses demonstrated substantial karyotypic divergence from C. flamarioni, although some entire chromosomes and large chromosomal segments remained conserved between C. minutus and C. lami. Our findings underscore the critical role of chromosomal rearrangements in shaping the diversification of Ctenomys. Additionally, we identified shared chromosomal rearrangements in C. minutus and C. lami, which are likely restricted to the torquatus group. Conclusions: These rearrangements provide new insights into the processes driving chromosomal evolution in genus Ctenomys. Full article

Telomere maintenance enables unlimited cell proliferation by counteracting telomere erosion. While the majority of tumors activate telomerase, a significant subset—approximately 10–15%—utilizes alternative lengthening of telomeres (ALT), a recombination-based mechanism. ALT-positive cancers are classically associated with genomic instability, anaphase bridges, chromosomal rearrangements, and resistance to DNA-damaging therapies. This process is closely associated with genetic instability, which contributes to chromosomal rearrangements and tumor evolution. Consequently, ALT has traditionally been considered an adverse prognostic marker in aggressive malignancies such as osteosarcoma, pancreatic neuroendocrine tumors, and high-grade sarcomas. Paradoxically, recent evidence demonstrates that ALT positivity correlates with improved survival in glioblastoma (GBM) and chondrosarcoma, two tumor types that have historically been regarded as immune-cold and therapeutically intractable. This favorable outcome likely reflects a convergence of factors, including replication stress and DNA damage that impose a fitness cost in slow-growing or metabolically constrained tumors. Loss of ATRX/DAXX, while enabling ALT, further amplifies chromatin fragility, and ALT-mediated instability may paradoxically enhance immunogenicity within immune-quiescent microenvironments. Moreover, ALT-positive cells exhibit unique therapeutic vulnerabilities, particularly to ATR and PARP inhibitors. Together, these observations support a context-dependent model in which ALT functions as a double-edged sword, acting as a driver of malignant aggressiveness in rapidly proliferating cancers while serving as a relative liability in slower-growing, immune-cold tumors. Understanding this duality not only refines prognostic stratification but also opens opportunities for precision oncology. By integrating ALT-specific biomarkers into clinical workflows and exploiting ALT-related DNA repair dependencies, clinicians may transform a once uniformly negative prognostic factor into an actionable therapeutic target. Full article

Background/Objectives: Synovial sarcoma (SS) is an aggressive soft-tissue tumor characterized by the chromosomal translocation t(X;18) (p11.2;q11.2), most commonly involving the fusion of the SYT gene on chromosome 18 with the SSX1 or SSX2 genes on chromosome X. This study aims to explore the clinicopathological and molecular characteristics of synovial sarcoma in a cohort of Moroccan patients. Methods: We analyzed 48 cases of synovial sarcoma using formalin-fixed, paraffin-embedded (FFPE) tissue samples. Histological grading was performed according to the FNCLCC system. Immunohistochemical staining was employed to detect cytokeratin (CK) and epithelial membrane antigen (EMA). Molecular analysis included fluorescence in situ hybridization (FISH) to identify SS18 gene rearrangements and reverse transcription–polymerase chain reaction (RT-PCR) to detect SYT-SSX fusion transcripts. Results: Among the cohort, 56% of cases showed SS18 gene rearrangements via FISH, while RT-PCR confirmed the presence of SS18-SSX1 and SS18-SSX2 transcripts in 60% and 32% of cases, respectively. The remainder was classified as undifferentiated sarcoma. Notably, no significant associations were observed between SYT-SSX fusion type and clinicopathological features. Conclusions: These findings underscore the importance of integrating molecular techniques for precise diagnosis in synovial sarcoma. The results align with global patterns, emphasizing the necessity for molecular testing to enhance diagnostic accuracy and informing potential therapeutic advancements. Full article

Background/Objectives: Relapsed acute myeloid leukemia (AML) is often characterized by clonal evolution and acquired genomic abnormalities, which can inform prognosis and direct therapeutic decisions. The emergence of high-risk chromosomal rearrangements during relapse is of particular significance, yet the impact of rare and complex events remains poorly understood. This report details a case of relapsed AML that demonstrated rare MYC and MECOM rearrangements and additional features that were not observed at initial diagnosis, emphasizing the clinical relevance of serial cytogenetic assessments. Case Description: A 70-year-old man was initially diagnosed with AML, exhibiting monocytic differentiation, an 11q23 deletion involving KMT2A loss, and a U2AF1 mutation. After achieving remission with azacitidine and venetoclax, the patient relapsed within ten months, necessitating reevaluation and modification of therapy. Repeat cytogenetic analysis at relapse revealed a distinct t(3;8)(q26.2;q24.3) exhibiting MYC and MECOM rearrangements, features that were absent at initial diagnosis. Conclusions: This case underscores the importance of serial cytogenetic and molecular profiling in relapsed AML. The emergence of new abnormalities upon relapse suggested underlying genomic instability and clonal evolution. MYC rearrangements are notably rare in AML, especially with concurrent MECOM rearrangements, highlighting a unique feature of this case. The identification of novel abnormalities at relapse may carry prognostic and therapeutic significance and may be used to refine risk stratification. Thus, ongoing cytogenetic monitoring is essential to adapt management approaches in evolving disease contexts. Full article

Polemonium caeruleum L. (Polemoniaceae) is a perennial flowering plant native to Eurasia and North America, which is used as a fodder, medicinal, and ornamental plant. Many issues related to the taxonomy and origin of this valuable species still remain unclear. The intraspecific genetic variability of P. caeruleum and chromosomal organization of its genome are insufficiently studied. For the first time, we analyzed NGS genomic data of P. caeruleum using ReapeatExplorer2/TAREAN/DANTE Pipelines. In its repeatome, we identified 66.08% of Class I retrotransposons; 0.57% of Class II transposons; 0.42% of ribosomal DNA; and 0.87% of satellite DNA (six high-confident and three low-confident putative satellite DNAs). FISH chromosome mapping of seven tandem DNAs was carried out in two P. caeruleum varieties and two wild populations. Our results demonstrated the effectiveness of using satDNAs Pol_C 46 and Pol_C 33 in combination with 45S rDNA and 5S rDNA for precise chromosome identification. This approach allowed us to study intraspecific chromosomal variability and detect chromosomal rearrangements in the studied accessions of P. caeruleum, which could be related to the speciation process. These novel molecular markers are important for chromosome studies within Polemonium to clarify its taxonomy and phylogeny, and also, they expand the potential of different breeding programs. Full article

Fanconi anemia (FA) is a genetic disorder characterized by congenital anomalies, bone marrow failure, and cancer predisposition. Among other solid cancers, head and neck squamous cell carcinoma (FA HNSCC) is the most common cancer type in individuals with FA. The FA pathway is required for the complete repair of DNA interstrand crosslinks (ICLs), and unresolved ICLs result in cell cycle arrest, apoptosis, or complex chromosomal rearrangements due to chromosome breaks, ultimately leading to tumorigenesis. FA HNSCCs present earlier (median age of onset in the 30s) and exhibit a more aggressive course with frequent recurrence and second primaries, and entail a poorer survival rate compared to sporadic HNSCC. FA HNSCCs are mostly human papillomavirus (HPV)-negative and frequently carry somatic copy number variations (CNVs), which amplify oncogenes implicated in sporadic HNSCC, but single-nucleotide variants or small insertions and deletions are less frequent than in HPV-negative sporadic HNSCC. A subset of sporadic HNSCC carries pathogenic mutations or promoter methylation in FA genes, which also harbor characteristic somatic CNVs, suggesting shared molecular underpinnings with FA HNSCC. Heightened inflammation from genomic instability and transcriptional activation of retrotransposons contribute to tumorigenesis and increased invasiveness by the epithelial-to-mesenchymal transition. Due to heightened sensitivity to DNA crosslinking agents in patients with FA, platinum-based chemotherapy is generally avoided, which presents a significant hurdle for treatment and thereby leaves limited therapeutic options. Surgical management is the mainstay of therapy if possible, and targeted therapy has been increasingly studied in HNSCC in FA. Full article

Topoisomerase 1 (Top1) removes transcription-related helical torsions and thus plays an important role in preventing genome instability instigated by the formation of non-canonical DNA secondary structures. The genetically tractable Saccharomyces cerevisiae model proved effective in defining the critical function of Top1 to prevent recombination and chromosomal rearrangement at G4-forming genomic loci and studying the human cancer-associated Top1 mutants through the expression of analogous yeast mutants. We previously showed that cleavage-defective Top1 mutants strongly elevate the rate of recombination at G4 DNA, which involves binding to G4 DNA and interaction with the protein nucleolin (Nsr1 in yeast). Here, we further explored the mechanism of genome instability induced by the yeast Top1Y740* mutant, analogous to the human Top1W765Stop mutant conferring resistance to CPT. We show that yTop1Y740* elevates duplications as well as recombination specifically at G4-forming sequences. Interestingly, SUMOylation of yTop1Y740*, which does not affect the G4 DNA-binding or Nsr1-interaction by this mutant, is necessary for such elevated G4-specific genome instability. Many tumors with mutations at the C-terminal residues of Top1, particularly W765, have significantly high G4-associated mutations, underscoring the importance of further investigation into how SUMOylation affects the function of these Top1 mutants at G4 DNA. Full article

Complex chromosomal rearrangements (CCRs) are rare structural abnormalities involving at least three chromosomal breakpoints and often two or more chromosomes. Owing to their inherent genomic complexity, CCRs are frequently associated with abnormal phenotypes, including developmental delay, congenital anomalies, and infertility. In this study, we report four male patients, three of them with de novo rare structural chromosomal rearrangement detected through a combination of Giemsa-Trypsin (GTG) banding, fluorescence in situ hybridization (FISH), and high-resolution microarray techniques (SNP array and array CGH). Each of the four cases turned out to be of a different type: in addition to two exceptional CCRs, an inv dup del 18q and a cluster rearrangement involving the long arm of chromosome 4 were identified. Despite the limitations of the testing methods, we performed a detailed analysis of the relationship between the most detailed genotype data and the associated phenotype. Our study provides further valuable evidence that the use of molecular cytogenetic methods is of paramount importance even in cases with abnormal karyotypes detected by light microscopy, as high-resolution data may reveal unsuspected genomic complexity, which is essential for genetic counseling in these patients. Full article

Chromosomal BCR-ABL1 fusions are the defining molecular lesions of chronic myeloid leukemia (CML) and Philadelphia-positive acute lymphoblastic leukemia, and are rarely observed in acute myeloid leukemia. Their detection have transformed treatment paradigms by enabling effective use of specific tyrosine kinase inhibitors (TKIs). Although many BCR-ABL1 rearrangements are identified by standard cytogenetics, a clinically relevant subset is cryptic and can escape detection. High-depth RNA sequencing assays have improved our capacity to detect expressed fusion transcripts. Here, we introduce two myeloid cases in which cryptic BCR-ABL1 rearrangements and precise breakpoints detection required an integrated molecular approach: we describe the initial diagnostic pitfalls, detail the downstream therapeutic and prognostic implications and offer practical recommendations for integrating targeted sequencing and cytogenetics into routine practice. In the first case, a patient initially diagnosed with a myelodysplastic/myeloproliferative neoplasm was reclassified as CML following the discovery of a cryptic e13a2 BCR-ABL1 rearrangement, enabling effective TKI treatment. In the second case, a previously undetected BCR-ABL1 fusion was identified in a relapsed AML patient, along with additional molecular lesions, underscoring the aggressive nature of the disease. Our findings support a systematic, multimodal screening strategy in patients with atypical presentations to ensure the timely detection of clinically actionable fusion events. Full article