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Mammalian Embryogenesis (mammalian + embryogenesi)
Selected AbstractsRegulation of the Nanog gene by both positive and negative cis -regulatory elements in embryonal carcinoma cells and embryonic stem cellsMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 2 2009Brian Boer Abstract The transcription factor Nanog is essential for mammalian embryogenesis, as well as the pluripotency of embryonic stem (ES) cells. Work with ES cells and embryonal carcinoma (EC) cells previously identified positive and negative cis -regulatory elements that influence the activity of the Nanog promoter, including adjacent cis -regulatory elements that bind Sox2 and Oct-3/4. Given the importance of Nanog during mammalian development, we examined the cis -regulatory elements required for Nanog promoter activity more closely. In this study, we demonstrate that two positive cis -regulatory elements previously shown to be active in F9 EC cells are also active in ES cells. We also identify a novel negative regulatory region that is located in close proximity to two other positive Nanog cis -regulatory elements. Although this negative regulatory region is active in F9 EC cells and ES cells, it is inactive in P19 EC cells. Furthermore, we demonstrate that one of the positive cis -regulatory elements active in F9 EC cells and ES cells is inactive in P19 EC cells. Together, these and other studies suggest that Nanog transcription is regulated by the interplay of positive and negative cis -regulatory elements. Given that P19 appears to be more closely related to a later developmental stage of mammalian development than F9 and ES cells, differential utilization of cis -regulatory elements may reflect mechanisms used during development to achieve the correct level of Nanog expression as embryogenesis unfolds. Mol. Reprod. Dev. 76: 173,182, 2009. © 2008 Wiley-Liss, Inc. [source] Distal enhancer of the mouse FGF-4 gene and its human counterpart exhibit differential activity: Critical role of a GT boxMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 3 2005Brian Boer Abstract Previous studies have shown that there is a strict requirement for fibroblast growth factor-4 (FGF-4) during mammalian embryogenesis, and that FGF-4 expression in embryonic stem (ES) cells and embryonal carcinoma (EC) cells are controlled by a powerful downstream distal enhancer. More recently, mouse ES cells were shown to express significantly more FGF-4 mRNA than human ES cells. In the work reported here, we demonstrate that mouse EC cells also express far more FGF-4 mRNA than human EC cells. Using a panel of FGF-4 promoter/reporter gene constructs, we demonstrate that the enhancer of the mouse FGF-4 gene is approximately tenfold more active than its human counterpart. Moreover, we demonstrate that the critical difference between the mouse and the human FGF-4 enhancer is a 4 bp difference in the sequence of an essential GT box. Importantly, we demonstrate that changing 4 bp in the human enhancer to match the sequence of the mouse GT box elevates the activity of the human FGF-4 enhancer to the same level as that of the mouse enhancer. We extended these studies by examining the roles of Sp1 and Sp3 in FGF-4 expression. Although we demonstrate that Sp3, but not Sp1, can activate the FGF-4 promoter when artificially tethered to the FGF-4 enhancer, we show that Sp3 is not essential for expression of FGF-4 mRNA in mouse ES cells. Finally, our studies with human EC cells suggest that the factor responsible for mediating the effect of the mouse GT box is unlikely to be Sp1 or Sp3, and this factor is either not expressed in human EC cells or it is not sufficiently active in these cells. Mol. Reprod. Dev. © 2005 Wiley-Liss, Inc. [source] Roles of the conserved CCAAT and GC boxes of the human and mouse type II transforming growth factor-, receptor genesMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2003Cory T. Bernadt Abstract Embryonal carcinoma (EC) cells are used widely to study the molecular mechanisms that regulate the transcription of genes during mammalian embryogenesis. The type II transforming growth factor-, receptor (T,R-II) gene is expressed at very low levels by mouse EC cells prior to differentiation. Differentiation of EC cells results in increases of both the steady-state levels of T,R-II mRNA and the activity of the T,R-II promoter. Several cis -regulatory elements have been shown previously to regulate the T,R-II gene. This study focuses on the role of a CCAAT box and three GC boxes in the regulation of the human and mouse T,R-II promoters in EC-differentiated cells. We demonstrate that the CCAAT box and two flanking GC boxes, Sp A and Sp B, function as positive regulatory elements in the human T,R-II promoter, and that the transcription factor complex NF-Y positively regulates the human T,R-II promoter through the CCAAT box motif. We also show that the CCAAT box and the downstream GC box Sp B, which are conserved between the human and mouse promoters, behave as positive regulatory elements in the mouse T,R-II promoter. In addition, we demonstrate that the transcription factor Sp1 can bind to the Sp B GC box in vitro. Finally, we show that a GC box located 25 bp upstream of the major transcription start site of the T,R-II gene plays a minimal role in the function of the T,R-II promoter in EC-differentiated cells. Together, our studies highlight important differences and similarities in the cis -regulatory elements that regulate the human and mouse T,R-II promoters. Mol. Reprod. Dev. 65: 353,365, 2003. © 2003 Wiley-Liss, Inc. [source] Distinct migratory behavior of early- and late-born neurons derived from the cortical ventricular zoneTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 1 2004Yumiko Hatanaka Abstract Time-lapse studies indicate that ventricular zone (VZ)-derived cells show two migratory modes in the cerebral cortex at different stages of mammalian embryogenesis: somal translocation and locomotion. We carried out a systematic analysis to examine whether the migratory behavior of cortical neurons derived from the cortical VZ is stage-dependent. We labeled VZ cells of mouse embryos with green fluorescent protein (gfp) -encoding plasmids by in utero electroporation and evaluated the labeled cells after appropriate survival periods. After electroporation at either embryonic day (E) 12.5 or E15.5, GFP+ VZ cells were initially spindle-shaped and radially oriented. After leaving the VZ, they transformed into round or horizontally oriented fusiform neurons with many short processes. They then seemed to gradually change into radially oriented bipolar cells as they moved upward. Whereas the earliest emigrants from the VZ labeled at E12.5 (early-born neurons) reached the top of the cortical plate (CP) after these changes, VZ cells labeled at E15.5 (late-born neurons) further migrated along the length of radial fibers to reach the top of the CP. A dominant negative form of the gene for cyclin-dependent kinase 5 (Cdk5DN) was then introduced into VZ cells. Transfection of E12.5 VZ with cdk5dn did not disrupt the migration of the early-born neurons. However, this caused a failure in migration of the late-born neurons, although they transformed into bipolar shapes in the intermediate zone. Thus, there appear to be at least two distinct migratory phases of cortical neurons: one common to the early- and late-born neurons, and the other specific to late-born neurons and Cdk5-dependent. J. Comp. Neurol. 479:1,14, 2004. © 2004 Wiley-Liss, Inc. [source] | ||||||||||