VAMP2 is expressed in myogenic cells during rat development

Vesicle-associated membrane protein 2 (VAMP2) is a member of the SNARE family of proteins that regulate the intracellular vesicle fusion process. This study investigated the developmental expression of VAMP2 in the rat embryo. In the trunk, VAMP2 was primarily found in the heart on embryonic day (E) 10. On E12.5, VAMP2 expression was found in nerve fibers, somites, and heart. In somites, epithelial cells in the dorsomedial lip, and elongated myoblasts in myotome were positive for VAMP2. On E16.5, VAMP2 was expressed in the heart, nerve fibers, and skeletal muscles. In skeletal muscles, multinuclear myotubes were positive for VAMP2. In the head, where muscles are derived both from somitic and non-somitic origin, VAMP2 was found in myotubes of the extrinsic ocular muscles and masseter muscle on E16.5. These findings suggest the involvement of VAMP2 in the development of skeletal muscles of somitic and non-somitic origins.     

经冠脉自体骨髓单个核细胞移植治疗扩张型心肌病的随机对照研究

目的采用随机、对照、前瞻性的临床试验,旨在评价经冠脉自体骨髓单个核细胞(BMMNCs)移植治疗扩张型心肌病的有效性和安全性。方法连续入选26例扩张型心肌病患者,细胞移植组(14例)行经冠脉自体BMMNCs移植联合标准药物治疗;对照组(12例)接受标准药物治疗。结果3个月后,细胞移植组的左室射血分数(LVEF)由(29.21±4.41)%提高至(31.08±4.54)%(P=0.004),与对照组比较,无统计学差异(P=0.216);PET/CT示心肌13N-NH3灌注和18F-FDG代谢显像显著改善;氮末端脑钠素前体(NT-proBNP)、6min步行试验和明尼苏达生活质量评分的改变均具有统计学意义。结论经冠脉自体BMMNCs移植治疗扩张型心肌病安全而有效,可能是通过BMMNCs转分化为心肌细胞和血管内皮细胞而改善心功能。     

Dose-dependent modulation of myogenesis by HGF: implications for c-Met expression and downstream signalling pathways

Abstract

Hepatocyte growth factor (HGF) regulates satellite cell activation, proliferation, and differentiation. We analyzed the dose-dependent effects of HGF on myogenesis. Murine C2C12 and human donor-derived skeletal muscle myoblasts were treated with 0, 2, or 10?ng/ml HGF followed by assessment of proliferation and differentiation. HGF (2?ng/ml) significantly promoted cell division, but reduced myogenic commitment and fusion. Conversely, 10?ng/ml HGF reduced proliferative capability, but increased differentiation. c-Met expression analysis revealed significantly decreased expression in differentiating cells cultured with 2?ng/ml HGF, but increased expression in proliferating cells with 10?ng/ml HGF. Mitogen-activated protein kinase (MAPKs: ERK, JNK, or p38K) and phosphatidylinositol-3-kinase (PI3K) inhibition abrogated the HGF-stimulated increase in cell number. Interestingly, PI3K and p38 kinase facilitated the negative effect of HGF on proliferation, while ERK inhibition abrogated the HGF-mediated decrease in differentiation. Dose-dependent effects of HGF are mediated by changes in c-Met expression and downstream MAPK and PI3K signalling.     

小鼠舌肌发育相关基因的功能聚类分析

目的：研究小鼠舌肌发育的分子调控机制。方法：取胚胎第13．25天（E13．25）及 E15．5小鼠舌组织。应用 Affy-metrix Mouse GeneChip,对胎鼠舌发育过程中的差异基因进行筛选。应用 DAVID 网络分析工具对基因进行功能和聚类分析。结果：基因功能和聚类分析表明,在 E13．25高表达的基因主要与细胞周期相关因子（Exo1、Gsk3B、Kif20b、Skp2）和细胞粘附因子（Neo1、lama1）等相关。在 E15．5高表达的基因主要与细胞骨架（titin、Hspb7）相关。结论：小鼠舌组织增殖和特化与细胞周期和细胞粘附基因相关,舌组织分化和成熟主要与细胞骨架相关。     

Overexpression of the immunoglobulin superfamily members CDO and BOC enhances differentiation of the human rhabdomyosarcoma cell line RD

Rhabdomyosarcoma is a childhood tumor of the skeletal muscle lineage in which cells display defects in both biochemical and morphological aspects of differentiation. The immunoglobulin superfamily members CDO and BOC are components of a cell surface receptor that positively regulates myogenesis in vitro. Expression of Cdo and Boc in myoblast cell lines is downregulated by the ras oncogene, and forced re-expression of either Cdo or Boc can override ras-induced inhibition of myogenic differentiation [Kang et al., J Cell Biol 1998; 143:403-413; Kang et al., EMBO J 2002; 21:114-124]. The current study sought to test whether the promyogenic properties of CDO and BOC could be extended to a human rhabdomyosarcoma cell line, RD. Stable overexpression of CDO or BOC in RD cells led to enhanced expression of two markers of muscle cell differentiation, troponin T and myosin heavy chain, and to increased formation of elongated, myosin heavy chain-positive myotubes. These observations are consistent with the notion that CDO and BOC play a role in the inverse relationship between differentiation and transformation of cells in the skeletal muscle lineage.     

Deletion of Pax7 changes the tunica muscularis of the mouse esophagus from an entirely striated into a mixed phenotype

The mechanisms responsible for the different amounts of striated muscle in mammalian esophagi are still enigmatic. A recent ultrastructural analysis in mouse esophagus pointed to a particular role of satellite cells during postnatal growth of striated muscle. The aim of this study was to investigate satellite cell development and the influence of Pax7 on this process. Developing and adult esophagi of wild‐type and mice carrying a targeted mutation in Pax7 were analyzed by electron microscopy. We found a gene dose‐dependent delayed development of striated muscle and a severe loss of satellite cells in Pax7^+/? and Pax7^?/? esophagi. In contrast to the entirely striated wild‐type esophagus, Pax7^?/? mutants developed a mixed phenotype with predominantly smooth muscle caudally. We conclude that Pax7‐dependent myogenic progenitor cells are of prime importance for striated muscle formation and the degree of smooth‐to‐striated muscle conversion during esophageal ontogeny. Developmental Dynamics 238:864–874, 2009. © 2009 Wiley‐Liss, Inc.     

Follow-up studies in a case of unusual congenital myopathy,suggestive of nemaline type

Summary A 20-month-old boy — offspring of consanguinous parents, whose mother presumably had subclinical myopathy — presented with clinical signs of congenital non-progressive myopathy, neurogenic-myogenic electromyographic findings and normal motor conduction velocity. Biopsy of quadriceps muscle showed fiber-type disproportion with hypotrophic type 1, hypertrophic 2A and absent 2B fibers. Subsarcolemmal segmental foci of abnormally, in part regularly arranged bundles of mostly thin myofilaments were found in 13% of hypotrophic type 1 fibers. Rods were seen in only 1 fiber out of 20 tissue blocks. Reexamination 6 years later revealed slightly increased muscle force, myopathic EMG pattern and borderline motor and sensory nerve conduction velocities. Biopsy specimen from deltoid muscle consisted of untypable fibers of varying diameters with jagged Z-lines and increased variability of myofibrillar diameters. Multiple rods were present in 1% of the fibers, the formerly seen segmental foci in 0.1% only. Several intramuscular nerves were normal. The case contributes some new features to the spectrum of congenital myopathies of the nemaline type and suggests different stages of arrested maturation of type 1 fibers at least in this particular case.     

Expression of myogenic regulatory factors in chicken embryos during somite and limb development

The expression of the myogenic regulatory factors (MRFs), Myf5, MyoD, myogenin (Mgn) and MRF4 have been analysed during the development of chicken embryo somites and limbs. In somites, Myf5 is expressed first in somites and paraxial mesoderm at HH stage 9 followed by MyoD at HH stage 12, and Mgn and MRF4 at HH stage 14. In older somites, Myf5 and MyoD are also expressed in the ventrally extending myotome prior to Mgn and MRF4 expression. In limb muscles a similar temporal sequence is observed with Myf5 expression detected first in forelimbs at HH stage 22, MyoD at HH stage 23, Mgn at HH stage 24 and MRF4 at HH stage 30. This report describes the precise time of onset of expression of each MRF in somites and limbs during chicken embryo development, and provides a detailed comparative timeline of MRF expression in different embryonic muscle groups.     

Regulation of p53 is critical for vertebrate limb regeneration

Extensive regeneration of the vertebrate body plan is found in salamander and fish species. In these organisms, regeneration takes place through reprogramming of differentiated cells, proliferation, and subsequent redifferentiation of adult tissues. Such plasticity is rarely found in adult mammalian tissues, and this has been proposed as the basis of their inability to regenerate complex structures. Despite their importance, the mechanisms underlying the regulation of the differentiated state during regeneration remain unclear. Here, we analyzed the role of the tumor-suppressor p53 during salamander limb regeneration. The activity of p53 initially decreases and then returns to baseline. Its down-regulation is required for formation of the blastema, and its up-regulation is necessary for the redifferentiation phase. Importantly, we show that a decrease in the level of p53 activity is critical for cell cycle reentry of postmitotic, differentiated cells, whereas an increase is required for muscle differentiation. In addition, we have uncovered a potential mechanism for the regulation of p53 during limb regeneration, based on its competitive inhibition by ΔNp73. Our results suggest that the regulation of p53 activity is a pivotal mechanism that controls the plasticity of the differentiated state during regeneration.Unlike mammals, which exhibit limited regenerative abilities, the urodele amphibians—or salamanders—are capable of regenerating an extraordinary range of body structures, including ocular tissues, tail, sections of the heart, parts of the nervous system, and entire limbs (1). In salamanders, such as the newt and axolotl, limb regeneration depends on the formation of a blastema, a mound of progenitor cells of restricted potential that arises after amputation (2–4). Following a period of proliferation, blastema cells redifferentiate and restore the structures of the limb.Extensive evidence indicates that limb regeneration depends on reprogramming of cells in mature limb tissues. Upon amputation, muscle, cartilage, and connective tissue cells underneath the injury site lose their differentiated characteristics and re-enter the cell cycle to give rise to the blastema (5–8). This mechanism has also been observed during zebrafish heart and fin regeneration (9, 10). In contrast, reversals of the differentiated state are rarely observed in mammalian tissues, which led to the suggestion that inability to undergo dedifferentiation could contribute to the failure of regeneration in mammals (11). Despite their significance, the mechanisms underlying regulation of the differentiated state during vertebrate regeneration remain poorly understood.Recently, the tumor suppressor p53, whose best-characterized functions are in the maintenance of genome stability (12), has been implicated in the suppression of artificial cell reprogramming to pluripotency (13–17) and the promotion of differentiation pathways in mammals (18). In addition, it has been observed that inhibiting p53 disrupts limb regrowth in salamanders (19), although its role in this context has remained unknown. It is possible that p53 could play a role in the regulation of dedifferentiation and redifferentiation events intrinsic to vertebrate regeneration. Our results demonstrate that the regulation of p53 activity is critical for limb regeneration by controlling key cell fate decisions throughout this process.