Cytogenetic and Genome Research最新文献

Introduction: Partial trisomy of the 6q24qter region is a rare chromosomal disorder characterized by variable clinical features and poorly understood mechanistic origins.

Case presentation: We describe a de novo complex der(6) chromosome in a patient with features consistent with partial 6q trisomy syndrome, including congenital heart disease, growth restriction, developmental delay, and dysmorphic traits. Molecular Findings: Whole-genome sequencing (WGS) identified duplications of 1.5 Mb on 6p25.3 and 23.3 Mb on 6q24.3-qter. While the 6p duplication appears benign, the phenotype is likely driven by dosage-sensitive 6q genes (ARID1B, TAB2, QKI) and possible additive effects from other duplicated genes. No parental pericentric inversion was detected by classical or molecular cytogenetics, and WGS revealed no inversion-associated breakpoints. Instead, chimeric (q-/q+) and truncated reads at the 6q junction support a replication-based origin, such as reversed template switching. FISH confirmed direct insertion of the 6q segment into 6p25.3, without a del/dup pattern typical of inversion-derived recombinants. Notably, WGS detected no direct 6p-6q junction reads but identified chimeric 6p-15q-6q reads with 2-bp microhomologies, suggesting that chromosome 15 transiently mediated the rearrangement. Interspersed telomeric sequences and flanking Alu elements were also found at both breakpoints.

Conclusion: Altogether, these findings support a model in which replication fork stalling and template switching - potentially facilitated by telomere dynamics and repetitive elements - led to the formation of a recombinant-like der(6) chromosome. This case highlights the mechanistic complexity of structural rearrangements and the role of replication-based errors in shaping human genomic variation.

Introduction: Jumping translocations are rare cytogenetic events in hematologic malignancies, involving nonreciprocal translocation of a donor chromosome onto two or more recipient chromosomes.

Case presentation: In this paper, we report the first-ever case of a jumping translocation involving the long arm of chromosome 3 in a patient with mantle cell lymphoma. The basic clone had the translocation t(11;14)(q13;q32) and a der(13)t(3;13)(q12;p11), and the three subclones had an additional jumping translocation, involving the translocation of 3q12 onto recipient chromosomes 14p, 15p, and der(14)t(11;14), thus resulting in partial trisomy and tetrasomy 3q.

Conclusion: Although the underlying mechanism for the formation of jumping translocations is not well understood, their presence is usually associated with poor prognosis and clonal evolution and additional data are needed for their better clinical management.

Introduction: Idiopathic short stature (ISS) refers to non-syndromic growth failure without chronic disorders. The molecular basis of ISS remains largely unknown. Although a variable number of tandem repeats (VNTR) of 57 nucleotides in ACAN is known to correlate with the height of people in the general population, the role of this genetic variant in the etiology of ISS has not been studied.

Methods: We studied 128 Japanese patients with ISS, including 63 patients with prenatal and postnatal growth failure (small-for-gestational age-SS [SGA-SS]), and 100 control individuals. To examine the repeat numbers of ACAN VNTR, we amplified the VNTR-containing genomic region and analyzed the PCR products by gel electrophoresis. The accuracy of the results was confirmed by long-read next-generation sequencing.

Results: The repeat numbers of the patient group were similarly distributed to those of the control group, and no patient had a very small number. Moreover, the repeat numbers of the shorter and longer alleles in each individual, as well as the average number of the two alleles, were comparable between the two groups. The height standard deviation scores obtained from 106 patients did not correlate with the repeat numbers. There was no difference in the repeat numbers between the SGA-SS or non-SGA ISS groups, and the control group.

Conclusion: The results of this study indicate that reduced repeat numbers of ACAN VNTR do not represent a monogenic cause or a major contributing factor for ISS. Our findings await further validation.

Introduction: Germline restricted chromosomes are considered a rather ancient element in the genomes of passerine birds. Obviously, detailed comparative studies on model groups including closely related species are required for a better understanding of GRC evolution. It is especially interesting if GRCs in such closely related species have acquired significant differences.

Methods: In this work we compared three taxonomically close species of the genus Phylloscopus: Ph. sindianus lorenzii, Ph. collybita menzbieri, and Ph. nitidus, which have differences in morphological manifestation of GRCs: macro- and micro-GRCs. We studied synaptonemal complexes using immunocytochemistry methods.

Results: We were able to trace the morphological transformations of macro-GRC at stages from leptotene to diplotene, and describe the complex structure of this chromosome in Ph. nitidus.

Conclusion: We hope that the taxonomic group under study can become a convenient model for comparative studies of GRCs in closely related species in order to understand the evolution of these unusual chromosomes.

Introduction: X chromosomal structural changes involving PHEX result in X-linked hypophosphatemia (XLH). However, their underlying mechanisms were poorly determined. Moreover, X chromosome inactivation (XCI) statuses in female patients with XLH remain to be studied.

Case presentation: We conducted systematic genomic analyses for a woman with XLH and detected a 3.2 Mb tandem duplication at Xp22.33, a 1.9 Mb tandem duplication at Xp22.31, and a 0.8 Mb deletion involving PHEX at Xp22.11 on the paternally derived chromosome. The fusion junctions contained templated insertions and short nucleotide additions indicative of non-homologous end joining (NHEJ) or alternative NHEJ. The patient had random XCI.

Conclusion: This study provides evidence that PHEX haploinsufficiency leads to typical XLH in women with random XCI and that a 5.9 Mb rearrangement on Xp22 permits random XCI. Our results, together with previous findings, imply that clustered structural changes due to NHEJ/alternative NHEJ are a unique type of human genomic rearrangements.

Introduction: Congenital cardiac defects are defined in cases with the deletion of the short arm of chromosome 5 and the duplication of the long arm of chromosome 4. Septal defects and patent ductus arteriosus are among the most common defects reported in the literature.

Case presentation: We reported on a case with a complex congenital cardiac defect, dysmorphic facial features, cat-like cry, hypotonia, hyporeflexia, weak swallowing and sucking, limb anomalies, and bilateral undescended testicles. A chromosomal microarray (CMA) revealed a duplication of chromosome 4q26q35.2 and a deletion of chromosome 5p15.33p14.3, originating from the balanced maternal translocation 46,XX,t(4;5)(q27;pter). Our patient showed clinical characteristics compatible with both deletion of 5p and duplication of 4q.

Conclusion: We reported a case with a rare chromosomal rearrangement. Similarities and differences between the cases in the literature are discussed. CMA is important to detect multiple copy number variations and genes may be involved. Studies are needed to investigate the genetic and/or epigenetic causes resulting in the clinical findings seen in the combination of deletion of chromosome 5p and duplication of chromosome 4q.

Introduction: Thamnophilidae (typical antbirds) are a diverse family of insectivorous passerine birds restricted to neotropical forests, encompassing 237 species, of which only 5 have been studied cytogenetically.

Methods: To investigate the chromosomal evolution of this group, we applied classical and molecular cytogenetic techniques, including conventional staining, C-banding, and fluorescence in situ hybridization with probes for repetitive telomeric sequences (TTAGGG)₅ and 18S rDNA, in two representative species: Thamnophilus caerulescens and Thamnophilus ruficapillus.

Results: The karyotypes of T. caerulescens and T. ruficapillus comprise 80 and 82 chromosomes, respectively. In addition to a possible fission in T. ruficapillus, morphological differences suggest the occurrence of pericentric inversions in the chromosomes of this species. The patterns of constitutive heterochromatin differed between the species: both showed centromeric markings and heterochromatin on the W chromosome, but T. ruficapillus also exhibited interstitial markings on seven chromosomal pairs. Both species presented interstitial telomeric sequences (ITSs) in the first seven pairs, which corresponded to constitutive heterochromatin in T. ruficapillus. The 18S rDNA probe hybridized to a single pair of microchromosomes in T. caerulescens and two pairs in T. ruficapillus.

Conclusion: This study revealed novel patterns of constitutive heterochromatin in T. ruficapillus and ITSs in both species, which have not been previously observed in Passeriformes. The correspondence between constitutive heterochromatin and ITSs in T. ruficapillus suggests that these sequences are composed of repetitive DNA highly similar to telomeric sequences and/or are remnants of pericentric inversions, whereas in T. caerulescens, other mechanisms seem to be involved. The differences in observed patterns highlight distinct chromosomal evolution between these species, emphasizing the diversity within the family Thamnophilidae and the genus Thamnophilus, in contrast to the conserved patterns typically observed in the class Aves.