Pax3 regulation of FGF signaling affects the progression of embryonic progenitor cells into the myogenic program

Pax3/7-dependent stem cells play an essential role in skeletal muscle development. We now show that Fgfr4 lies genetically downstream from Pax3 and is a direct target. In chromatin immunoprecipitation (ChIP)-on-chip experiments, Pax3 binds to a sequence 3' of the Fgfr4 gene that directs Pax3-dependent expression at sites of myogenesis in transgenic mouse embryos. The activity of this regulatory element is also partially dependent on E-boxes, targets of the myogenic regulatory factors, which are expressed as progenitor cells enter the myogenic program. Other FGF signaling components, notably Sprouty1, are also regulated by Pax3. In vivo manipulation of Sprouty expression reveals that FGF signaling affects the balance between Pax-positive progenitor cells and committed myoblasts. These results provide new insight into the Pax-initiated regulatory network that modulates stem cell maintenance versus tissue differentiation.     

REST/NRSF基因shRNA慢病毒载体的构建与鉴定

背景：神经元限制性沉默因子(REST/NRSF)能负向调控神经元及胰岛细胞分化相关基因的表达。 目的：构建并筛选能高效沉默大鼠REST/NRSF基因的shRNA慢病毒载体。 方法：针对REST/NRSF基因设计4组特异性siRNA靶点,合成靶序列的寡核苷酸序列,退火形成双链DNA,与经Hpa Ⅰ 和Xho Ⅰ双酶切后的pFU-GW-RNAi载体连接产生L-shREST/NRSF慢病毒载体,PCR筛选阳性克隆,测序鉴定。包装产生慢病毒颗粒,随后将其感染大鼠骨髓间充质干细胞,采用 Real-time PCR方法检测靶基因在 mRNA 水平的沉默效率。 结果与结论：PCR和测序证实,构建出了REST/NRSF shRNA的慢病毒载体L-shREST/NRSF,并能稳定转染大鼠间充质干细胞,感染效率达100%。4组shRNA序列均有基因沉默效果,并以第3组shRN序列效果最为明显。结果表明,该慢病毒表达载体能够在细胞水平有效沉默靶基因。     

Circadian rhythms of melatonin, cortisol, and clock gene expression during simulated night shift work

STUDY OBJECTIVES: The synchronization of peripheral circadian oscillators in humans living on atypical sleep/wake schedules is largely unknown. In this night shift work simulation, we evaluate clock gene expression in peripheral blood mononuclear cells (PBMCs) relative to reliable markers of the central circadian pacemaker. DESIGN: Participants were placed on a 10-hr delayed sleep/wake schedule simulating nighttime work followed by a daytime sleep episode. SETTING: Baseline, intermediate and final circadian evaluations were performed in the temporal isolation laboratory. PARTICIPANTS: Five healthy candidates, 18-30 years. INTERVENTIONS: Polychromatic white light of (mean +/-SEM) 6,036 +/-326 lux (approximately 17,685 +/-955 W/m2) during night shifts; dim light exposure after each night shift; an 8-hr sleep/darkness episode beginning 2 hrs after the end of each night shift. MEASUREMENTS: Melatonin and cortisol in plasma; clock genes HPER1, HPER2 and HBMAL1 RNA in PBMCs. RESULTS: Following 9 days on the night schedule, hormonal rhythms were adapted to the shifted schedule. HPER1 and HPER2 expression in PBMCs displayed significant circadian rhythmicity, which was in a conventional relationship with the shifted sleep/wake schedule. Changes in the pattern of clock gene expression were apparent as of 3 days on the shifted sleep/wake schedule. CONCLUSIONS: This preliminary study is the first documentation of the effects of a shifted sleep/wake schedule on the circadian expression of both peripheral circadian oscillators in PBMCs and centrally-driven hormonal rhythms. In light of evidence associating clock gene expression with tissue function, the study of peripheral circadian oscillators has important implications for understanding medical disorders affecting night shift workers.     

Time course and side-by-side analysis of mesodermal,pre-myogenic,myogenic and differentiated cell markers in the chicken model for skeletal muscle formation

The chicken is a well-established model for amniote (including human) skeletal muscle formation because the developmental anatomy of chicken skeletal muscle matches that of mammals. The accessibility of the chicken in the egg as well as the sequencing of its genome and novel molecular techniques have raised the profile of this model. Over the years, a number of regulatory and marker genes have been identified that are suited to monitor the progress of skeletal myogenesis both in wildtype and in experimental embryos. However, in the various studies, differing markers at different stages of development have been used. Moreover, contradictory results on the hierarchy of regulatory factors are now emerging, and clearly, factors need to be able to cooperate. Thus, a reference paper describing in detail and side-by-side the time course of marker gene expression during avian myogenesis is needed. We comparatively analysed onset and expression patterns of the key markers for the chicken immature paraxial mesoderm, for muscle-competent cells, for cells committed to myogenesis and for cells entering terminal differentiation. We performed this analysis from stages when the first paraxial mesoderm is being laid down to the stage when mesoderm formation comes to a conclusion. Our data show that, although the sequence of marker gene expression is the same at the various stages of development, the timing of the expression onset is quite different. Moreover, marker gene expression in myogenic cells being deployed from the dorsomedial and ventrolateral lips of the dermomyotome is different from those being deployed from the rostrocaudal lips, suggesting different molecular programs. Furthermore, expression of Myosin Heavy Chain genes is overlapping but different along the length of a myotube. Finally, Mef2c is the most likely partner of Mrf proteins, and, in contrast to the mouse and more alike frog and zebrafish fish, chicken Mrf4 is co-expressed with MyoG as cells enter terminal differentiation.     

Correlative association between circadian expression of mousePer2 gene and the proliferation of the neural stem cells

We examined the circadian expression of mousePeriod (mPer) genes (mPer1 and mPer2) and the proliferation of the neural stem cells in vitro. The neural stem cells from the ganglionic eminence of embryonic mice were expanded by the neurosphere method and then treated with epidermal growth factor (EGF) to stimulate their mitotic activity. The time courses of the proliferation were examined by WST-8 assay and bromodeoxyuridine (BrdU) incorporation assay and the expression of mPer1 and mPer2 genes was examined by RT-PCR and immunocytochemistry. We have found that EGF treatment elicited the circadian change in both the increase in viable cell number and DNA synthesis activity of the neural stem cells. Also, the gene expression of mPer2, but not mPer1, changed rhythmically with a period of 24 h and correlated negatively with the DNA synthesis activity rhythm. Furthermore, the treatment with an antisense oligonucleotide against mPer2 increased the DNA synthesis activity of the neural stem cells. These results suggest that mPer2 might periodically suppress the proliferation of neural stem cells.     

Ink4a and Arf differentially affect cell proliferation and neural stem cell self-renewal in Bmi1-deficient mice

The Polycomb group (PcG) gene Bmi1 promotes cell proliferation and stem cell self-renewal by repressing the Ink4a/Arf locus. We used a genetic approach to investigate whether Ink4a or Arf is more critical for relaying Bmi1 function in lymphoid cells, neural progenitors, and neural stem cells. We show that Arf is a general target of Bmi1, however particularly in neural stem cells, derepression of Ink4a contributes to Bmi1(-/-) phenotypes. Additionally, we demonstrate haploinsufficient effects for the Ink4a/Arf locus downstream of Bmi1 in vivo. This suggests differential, cell type-specific roles for Ink4a versus Arf in PcG-mediated (stem) cell cycle control.