Fanconi Anemia and the Response of Human Hematopoietic Cells to DNA Damage
Notice bibliographique
Résumé
Abstract Given their critical role in the generation and renewal of the hematopoietic system, we hypothesize that hematopoietic stem and primitive cells employ unusually stringent DNA damage responses to maintain genome stability. We also propose that Fanconi anemia proteins prevent bone marrow failure through their participation in these DNA repair and damage response pathways. We are testing both hypotheses by characterizing cellular responses to DNA double-strand breaks (DSBs) in 3 lineage-negative populations of hematopoietic cells isolated from human umbilical cord blood: hematopoietic stem cell-containing primitive CD34+ CD38− CD45RA−, early progenitor CD34+ CD38+ and late progenitor CD34− CD38+. Two key events in the initial cellular response to DSBs are phosphorylation of H2AX histones in chromatin at or near DSBs, and association of 53BP1 with gamma-H2AX at DSB sites. Once DSBs are detected, they then are repaired by two major pathways: error-prone non-homologous end-joining (NHEJ), utilized throughout the cell cycle, and error-free homologous recombination (HR), used when sister chromatids are present during S/G2 phases of the cell cycle. To study the response to and repair of DSBs in our sorted hematopoietic populations, we exposed quiescent and cytokine-stimulated haematopoietic cells and human fibroblasts to ionizing radiation (IR). Irradiation with 3 Gy rapidly induced formation of 53BP1 foci in all cell types, both cycling and non-cycling. In contrast, X-irradiation only induced foci of the Fanconi anemia protein FANCD2 in cycling cells. The majority of the induced FANCD2 foci colocalized with foci of gamma-H2AX. The subsequent persistence of 53BP1 foci at X-ray induced damage sites differed significantly between the lin− hematopoietic cells and the fibroblasts. During the first 6 hours following IR, cycling primitive and progenitor hematopoietic cells resolved 53BP1 foci more slowly than cycling human primary fibroblasts. In addition, X-ray induced 53BP1 foci persisted even longer in quiescent primitive CD34+ CD38− and early progenitor CD34+ CD38+ cells than in their cycling counterparts, while foci resolution kinetics were similar in quiescent and cycling late progenitor CD34− CD38+ cells and in fibroblasts. We also used a neutral comet assay to determine the kinetics of DSB rejoining following exposure to 15 Gy. We found that resolution of 53BP1 foci is not directly linked to rejoining of DSBs in lin− hematopoietic cells, as they rejoin DSBs more rapidly than primary fibroblasts, yet resolve 53BP1 foci more slowly. The effect is most prominent in primitive CD34− CD38− cells. Both cycling and non-cycling fibroblasts displayed similar kinetics of DSB rejoining. However, quiescent lin− hematopoietic cells displayed persistent breaks compared to cycling counterparts or to fibroblasts. Of particular note, quiescent lin− hematopoietic cells still had not rejoined a significant fraction of induced DSBs 24 hours post irradiation. Our results indicate that human primitive and progenitor hematopoetic cells differ from fibroblasts in their DNA damage responses and DSB repair kinetics. Our findings also suggest that, unlike fibroblasts, progression through the cell cycle plays a key role in the rapid repair of DSBs in hematopoietic cells. Because Lin− hematopoietic cells are more efficient at rejoining DSBs when cycling, we suggest that error-free HR repair plays an important role in DSB repair in these cells. Our detection of DNA damage-induced FANCD2 foci only in cycling lin− hematopoietic cells provides indirect support for this conclusion, as FA proteins are thought to be involved in HR repair. We are currently testing this hypothesis by determining the effect of knocking down FA protein expression on DSB repair and DNA damage responses in our three hematopoietic populations.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».