Browsing by Subject "Myogenesis"
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- PublicationOpen AccessFirst ultrastructural differentiation of myoblasts of chicken embryos: appearance of the initial filaments(Murcia : F. Hernández, 1990) González Santander, R.; Martínez Cuadrado, G.; Martínez Alonso, F.J.; Toledo Lobo, M.V.A study is made of the structure and ultrastructure of myoblasts located in the myotome in chicken embryos, between stages 18 and 19, for electron microscope observation of the occurrence of the first myogenetic filamentous molecules. We suggest a hypothesis for the formation of initial filaments consisting of an initial synthesis of actin globular molecules, carried out in the centre of the myoblast, near the nucleus, with the participation of RNA and the ribosomes. These molecules accumulate peripherically in areas below the plasmatic membrane where they polymerize into actin filamentous molecules which form the initial filaments. These move towards the sharp ends of the myoblast, under the plasmatic membrane, and thence to the interior of the cytoplasm, where they are evenly distributed. This genesis of initial filaments is independent of the influence of the nervous system. We postulate the existence of a single type of myoblast, of fibrillar form, with a dark central area containing the nucleus and the cell organelles, and two sharp, light end zones which contain only the initial filaments in a very light cytoplasmic matrix.
- PublicationOpen AccessFusion mechanism of the myoblasts in the myotome of the chick embryo(Murcia : F. Hernández, 1993) González Santander, R.; Toledo Lobo, M.V.; Martínez Alonso, F.J.; Martínez Cuadrado, G.We have studied the fusion process of rnyoblasts in the mytome corresponding to H.H. stages 22, 23 and 24 from calcitonin-treated chick embryos and their untreated controls. The micrograph images of this process were studied to detect the ultrastructural changes in myoblast morphology that could be associated with the known hormonal and biochen~ical changes that take place in preparation of fusion. Once actin and myosin myofilament differentiation and sarcomerogenesis had begun, the myotome myoblasts fused in bundles of 10- 14 myoblasts, and the following was observed during this process: plasmatic membrane interdigitation and invagination; the appearance of cytoplasmic flaps covering other myoblasts and fading at the point of contact; plasmatic membranes that fade and disintegrate; membrane rupturing; double closed lamina; small ringed lamina; large disperse vesicles; small vesicles (liposomes), and semi-dense amorphous material. Seven stages were established: 1.- Membrane rupture; 2.- Double closed and elongated lamina; 3.- Small ringed lamina aligned lengthwise; 4.- Large dispersed vesicles; 5.- Imprecise boundaries with a~norphous material in diffuse areas; 6.- Cytoplasm fusion; and 7.- Prefunctional syncitium. Answers to the questions: <>t he fusion of myoblasts takes place are suggested.
- PublicationOpen AccessHeterotopic neogenesis of skeletal muscle induced in the adult rat diaphragmatic peritoneum. Ultrastructural and transplantation studies(Murcia : F. Hernández, 1999) Drakontides, A.B.; Danon, M.J.; Levine, S.During the course of a mild chemical peritonitis, new skeletal muscle fibers develop and persist over a twelve-month interval in the diaphragmatic peritoneum. Light and electron microscopic studies revealed that the ectopic fibers developed from myoblasts and myotubes to fully differentiated muscle cells in the same manner as normally situated skeletal muscle. The ectopic fibers were separated from the intrinsic muscle by dense connective tissue and an elastic lamina. Diaphragms taken from normal rats and transplanted to the omentum of isogeneic recipients also developed skeletal muscle neogenesis in the same ectopic location as in the normal diaphragm. Satellite cells, reactive fibroblasts in the peritoneum, mesenchymal stem cells or blood-borne myoblast precursor cells could be the source of these ectopic muscle fibers. The results of the present studies, however, cannot provide conclusive evidence for the origin of the new muscle fibers. Regardless of their source, the methods employed may represent a unique model for the development and prolonged maintenance of skeletal muscle fibers in a heterotopic location in vivo.
- PublicationOpen AccessPax genes in myogenesis: Alternate transcripts add complexity(Murcia : F. Hernández, 2004) Lamey, T.M.; Koenders, A.; Ziman, M.Pax3 and Pax7 are powerful myogenic inducers and hence play a critical role in skeletal muscle development and regeneration. In this paper we discuss the role of Pax3 and Pax7 in dorsal patterning of the somite with subsequent determination of myogenic precursor cells for muscle formation within the developing embryo and in adult muscle. Recent evidence of the ability of stem cells to contribute to muscle regeneration in adult tissues, and the role of Pax7 in conversion of multipotent stem cells to the myogenic lineage are also discussed. Several tissue specific Pax7 transcripts that encode isoforms with different DNA binding characteristics and potentially distinct transactivation specificities are identified. The expression of a range of transcripts in the determination of different tissue lineages and distinct cell populations both in the embryo and in the adult indicates an extraordinary level of complexity. A detailed understanding of these molecules and their functions during embryogenesis and adult muscle formation is imperative for future stem cell therapies.
- PublicationOpen AccessRole of skeletal muscle in motor neuron development(Universidad de Murcia. Departamento de Biología Celular e Histología, 2016) Baguma-Nibasheka, Mark; Fracassi, Anna; Costain, Willard J.; Moreno, Sandra; Kablar, BorisThe current paper is a continuation of our work most recently described in Kablar, 2011. Here, we show lists of up- and down-regulated genes obtained by a cDNA microarray analysis that compared developing mouse MyoD-/- limb musculature (MyoD-dependent, innervated by Lateral Motor Column motor neurons) and Myf5-/- back (epaxial) musculature (Myf5-dependent, innervated by Medial Motor Column motor neurons) to the control and to each other, at embryonic day 13.5 which coincides with the robust programmed cell death of motor neurons and the inability of myogenesis to undergo its normal progression in the absence of Myf5 and MyoD that at this embryonic day cannot substitute for each other. We wanted to see if/how the myogenic program couples with the neurotrophic one, and also to separate Lateral from Medial column trophic requirements, potentially relevant to Motor Neuron Diseases with the predilection for the Lateral column. Several follow-up steps revealed that Kif5c, Stxbp1 and Polb, differentially expressed in the MyoD-/- limb muscle, and Ppargc1a, Glrb and Hoxd10, differentially expressed in the Myf5-/- back muscle, are actually regulators of motor neuron numbers. We propose a series of follow-up experiments and various ways to consider our current data
- PublicationOpen AccessSkeletal muscle development in the mouse embryo(Murcia : F. Hernández, 2000) Kablar, B.; Rudnicki, M.A.n this review we discuss the recent findings concerning the mechanisms that restrict somitic cells to the skeletal muscle fate, the myogenic regulatory factors controlling skeletal muscle differentiation and specification of myogenic cell lineages, the nature of inductive signals and the role of secreted proteins in embryonic patterning of the myotome. More specifically, we review data which strongly support the hypothesis that Myf-5 plays a unique role in development of epaxial muscle, that MyoD plays a unique role in development of hypaxial muscles derived from migratory myogenic precursor cells, and that both genes are responsible for development of intercostal and abdominal muscles (hypaxial muscles that develop from the dermatomal epithelia). In addition, while discussing upstream and post-translational regulation of myogenic regulatory factors (MRFs), we suggest that correct formation of the myotome requires a complex cooperation of DNA binding proteins and cofactors, as well as inhibitory function of non-muscle cells of the forming somite, whose proteins would sequester and suppress the transcription of MRFs. Moreover, in the third part of our review, we discuss embryonic structures, secreted proteins and myogenic induction. However, although different signaling molecules with activity in the process of somite patterning have been identified, not many of them are found to be necessary during in vivo embryonic development. To understand their functions, generation of multiple mutants or conditional/tissue-specific mutants will be necessary.
- PublicationOpen AccessStriated-for-smooth muscle replacement in the developing mouse esophagus(Universidad de Murcia. Departamento de Biología Celular e Histología, 2019) Baguma Nibasheka, Mark; Fracassi, Anna; Costain, Willard J.; Moreno, Sandra; Kablar, BorisThe esophagus is a muscular tube which transports swallowed content from the oral cavity and the pharynx to the stomach. Early in mouse development, an entire layer of the esophagus, the muscularis externa, consists of differentiated smooth muscle cells. Starting shortly after mid-gestation till about two weeks after birth, the muscularis externa almost entirely consists of striated muscle. This proximal-to-distal replacement of smooth muscle by the striated muscle depends on a number of factors. To identify the nature of the hypothetical “proximal” (mainly striated muscle originating) and “distal” (mainly smooth muscle originating) signals that govern the striated-for-smooth muscle replacement, we compared the esophagus of Myf5:MyoD null fetuses completely lacking striated muscle to the normal control using cDNA microarray analysis, followed by a comprehensive database search. Here we provide an insight into the nature of “proximal” and “distal” signals that govern the striated-for-smooth muscle replacement in the esophagus.
- PublicationOpen AccessUnorthodox myogenesis, possi ble developmental significance and implications for tissue histogenesis and regeneration(Murcia : F. Hernández, 1997) Cossu, G.During the last few years several reports have described the occurrence of skeletal myogenesis in cells derived from embryonic, fetal and perinatal tissues that usually do not contribute to skeletal muscle in the adult vertebrate body. After a brief description of current ideas on myogenic determination in higher vertebrates, three examples of this unorthodox myogenesis will be described: 1) the occurrence of myogenesis in chick epiblast cells, cultured in isolation in serum-free medium; 2) the presence of cells endowed with myogenic potential in the embryonic mouse neural tube; and 3) the occurrence of spontaneous or induced myogenesis in mesenchymal cells during fetal and postnatal life. A possible embryological basis for unorthodox myogenesis, in relation to gastrulation and morphogenetic fields, is then presented. It is also proposed that unorthodox myogenesis may represent a compensatory mechanism for higher vertebrates that have lost much of the regeneration potential of lower vertebrates.