Differential Expression and Re-Localization of Potential Cell Fate Determinants in Hematopoietic and Leukemia Stem Cells.
Notice bibliographique
Résumé
The ability of hematopoietic stem cells (HSC) for self-renewal is in part dependent on asymmetric cell divisions (ACD). However, the molecular insights remain elusive. Our current knowledge on mechanisms of ACD is predominantly derived from studies in the invertebrate systems of D. Melanogaster and C.Elegans. These include a cluster of polarity related genes, which function as cell fate determinants (CFD). The identification of Numb as a CFD gene in the mammalian stem cells of the brain and retina, and muscle satellite cells suggests conservation of aspects of ACD. Based on published data, a candidate list of 72 potential CFD genes was chosen for expression profiling. The specific populations of mouse bone marrow cells used for quantitative-PCR (q-PCR) studies were: (1) Long Term Repopulating-HSC (LTR-HSC) sorted for CD150+48−41−Lin− compared to progenitors (CD150+/−48+41+Lin−); (2) LTR-HSC derived from Sca+Kit+Lin−Rholow CD49b− compared to progenitors (Sca+/−Kit+/−Lin-Rhohigh CD49b+/−) and (3) the primary Leukemia Stem Cells (LSC), FLA2 and FLB1 with Leukemia Repopulating Cell (LRC) frequencies of respectively, 1 in 1.4 and 1 in 350 (P. Austin and G.S., unpublished). To validate the purity of LTR-HSC, limiting dilution assays were performed on the sorted populations. RNA obtained from all independent populations were initially pre-amplified before q-PCR. Subsequently, a subset of the highly expressed genes was re-analyzed with non-amplified RNA derived from the FLA2 and FLB1 cells. The q-PCR results from both the LTR-HSC and LSC populations show that a significant number of potential CFD genes, in particular those related to polarity and cytoskeleton function were highly and differentially expressed. It is assumed that the LTR-HSC has predominantly ACD. By using HoxB4 retroviral (MSCV) mediated over-expression to enforce symmetric cell divisions (SCD) and immunofluorescence (IF) analysis, we assessed the endogenous cellular expression of 2 of the highly expressed genes from the aforementioned q-PCR studies namely, Numb and Par6B. In a small cohort of LTR-HSC infected with the MSCV vector alone (representing ACD), the majority of cells expressed both Numb and Par6B in a cortical and asymmetric distribution. In contrast, infection by MSCV-HoxB4 virus of LTR-HSCs (representing SCD) resulted in the re-localization of both Numb and Par6B to be predominantly diffuse and symmetrical. Furthermore, using the FLA2 and FLB1 leukemia, with their respective LRC frequencies (above) as another cohort of cells that represent ACD (FLB1) and SCD (FLA2), similar re-localization results were obtained. Specifically, in FLB1 cells the predominant endogenous expression of Numb and Par6B was cortical and asymmetrical, in comparison to FLA2 cells where it was diffuse and symmetrical. Quantitative analysis of IF data suggested a higher expression of Numb and more so, of Par6B in FLB1 compared to FLA2 cells. Western blot analysis of Par6B in FLB1 and FLA2 cells supported the IF data. These preliminary results show potential CFD genes are highly and differentially expressed in LTR-HSC and LSC. Also, that during ACD there may be an up-regulation of CFDs together with a redistribution of these proteins to the cortical membrane, in either an asymmetrical or symmetrical localization. The inference of re-localization and up-regulation of in particular, Par6B may in itself be deterministic of HSC fate or may reflect a read-out of the cell fate choice, the latter of which could then be utilized to further identify other HSC CFD genes.
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) | 0,002 | 0,001 |
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 ».