Specialized replication mechanisms maintain genome stability at human centromeres.

The high incidence of whole-arm chromosome aneuploidy and translocations in tumors suggests instability of centromeres, unique loci built on repetitive sequences and essential for chromosome separation. The causes behind this fragility and the mechanisms preserving centromere integrity remain elusive. We show that replication stress, hallmark of pre-cancerous lesions, promotes centromeric breakage in mitosis, due to spindle forces and endonuclease activities. Mechanistically, we unveil unique dynamics of the centromeric replisome distinct from the rest of the genome. Locus-specific proteomics identifies specialized DNA replication and repair proteins at centromeres, highlighting them as difficult-to-replicate regions. The translesion synthesis pathway, along with other factors, acts to sustain centromere replication and integrity. Prolonged stress causes centromeric alterations like ruptures and translocations, as observed in ovarian cancer models experiencing replication stress. This study provides unprecedented insights into centromere replication and integrity, proposing mechanistic insights into the origins of centromere alterations leading to abnormal cancerous karyotypes.

Evaluation of the Aptima™ HBV Quant Dx assay for semi-quantitative HBV viral load from dried blood spots.

BACKGROUND: The detection and quantification of hepatitis B virus (HBV) DNA from dried blood spots (DBS) is a major tool for chronic hepatitis B management in resource-limited settings. This strategy fits in perfectly with the hepatitis control plan promoted by the World Health Organization. However, few commercial methods are validated for viral load (VL) measurement on DBS. OBJECTIVES: Our objective was to evaluate the performance of the HBV VL measurement of the Aptima™ HBV Quant Dx assay on DBS compared to plasma samples on the Panther® platform (Hologic). STUDY DESIGN: 266 whole blood samples for routine measurement were included. Five spots of 75 µL of whole blood were loaded onto a card before centrifugation and plasma settling. RESULTS: 149 samples were quantifiable and 117 were not detected. We achieved excellent linearity (r²â€¯= 0.994) over a wide range of measurements suitable for clinical practice, and a 95 % lower limit of detection (LLOD-95 %) at 2.65 log10 IU/mL (445 IU/mL). A good performance of this assay was observed for samples with HBV VL > LLOD-95 % and 100 % of samples were detected if HBV VL was above 2.95 log10 IU/mL. The correlation between the two matrices for quantitative VLs was good (r²â€¯= 0.978) with a very low bias (-0.002 log10 IU/mL). CONCLUSION: The Aptima™ assay can properly detect and quantify HBV DNA in DBS, providing a satisfactory use in clinical monitoring and therapeutic decisions. DBS represents an excellent alternative to plasma, especially in resource-limited countries, while maintaining the performance and advantages of an automated technique.