Molecular characterization of Barrett’s esophagus at single-cell resolution

Barrett’s esophagus (BE) is categorized, based on morphological appearance, into different stages, which correlate with the risk of developing esophageal adenocarcinoma. More advanced stages are more likely to acquire chromosomal instabilities, but stage-specific markers remain elusive. Here, we performed single-cell DNA-sequencing experiments (scDNAseq) with fresh BE biopsies. Dysplastic BE cells frequently contained chromosomal instability (CIN) regions, and these CIN cells carried mutations corresponding to the COSMIC mutational signature SBS17, which were not present in biopsy-matched chromosomally stable (CS) cells or patient-matched nondiseased control cells. CS cells were predominantly found in nondysplastic BE biopsies. The single-base substitution (SBS) signatures of all CS BE cells analyzed were indistinguishable from those of nondiseased esophageal or gastric cells. Single-cell RNA-sequencing (scRNAseq) experiments with BE biopsies identified two sets of marker genes which facilitate the distinction between columnar BE epithelium and nondysplastic/dysplastic stages. Moreover, histological validation confirmed a correlation between increased CLDN2 expression and the presence of dysplastic BE stages. Our scDNAseq and scRNAseq datasets, which are a useful resource for the community, provide insight into the mutational landscape and gene expression pattern at different stages of BE development.

Oxidative Stress Induces Telomere Dysfunction and Shortening in Human Oocytes of Advanced Age Donors

Research from the past decades provided strong evidence that in humans the pool of oocytes starts to decline already before the birth of a female individual, and from menarche to menopause the oocyte is exposed to different environmental stimuli. Since more and more women of the 21st century in developed countries wish to postpone the first pregnancy to their thirties, higher rates of miscarriage and chromosomal non-disjunction might occur. In oocytes of advanced maternal age, meaning above 35 years of age, characteristics such as chromosomal instabilities/abnormalities, spindle defects, decreased mitochondrial function and telomere shortening become more prevalent than in younger counterparts. Telomere attrition belongs to the so-called “hallmarks of aging” which are also relevant for the female germ-line cells. In oocytes, telomeres shorten with advancing maternal age due to the effects of reactive oxygen species and not upon replicative senescence, similar to how it is common in dividing cells.

RecQ and Fe–S helicases have unique roles in DNA metabolism dictated by their unwinding directionality, substrate specificity, and protein interactions

Helicases are molecular motors that play central roles in nucleic acid metabolism. Mutations in genes encoding DNA helicases of the RecQ and iron–sulfur (Fe–S) helicase families are linked to hereditary disorders characterized by chromosomal instabilities, highlighting the importance of these enzymes. Moreover, mono-allelic RecQ and Fe–S helicase mutations are associated with a broad spectrum of cancers. This review will discuss and contrast the specialized molecular functions and biological roles of RecQ and Fe–S helicases in DNA repair, the replication stress response, and the regulation of gene expression, laying a foundation for continued research in these important areas of study.

Chromosomal Abnormalities in Endometrial and Ovarian Carcinomas

Chromosomal Abnormalities in Endometrial and Ovarian CarcinomasDevelopment and progression of human malignancies involve multiple genetic changes including chromosomal instabilities such as translocations, deletions, and inversions. Chromosomal abnormalities were observed in 23 cases with ovarian and endometrial cancer by cytogenetic studies using a GTG (G bands by trypsin using Giemsa) banding technique. Specific chromosome bands were frequently involved, and were most frequent on chromosomes 1, 2, 3, 5, 12 and 17. Clonal alterations were observed at the cancer breakpoints, such as 1q21, 1q32, 3p21, 7q22, 11q23 in ovarian and 1p36, 1q32, 2p12, 3p21, 7q22, 9q34, 11p15, 11q23, 12q13, 14q11, 14q32, 16p13, 21q22 in endometrial cases. These findings provide evidence that multiple genetic lesions are associated with the pathogenesis of endometrial and ovarian cancer.