Biomedical subjects

Y Cinnamon

Publications and source records attributed to Y Cinnamon.

7 recordsLinked to original sources

PubMed2001

The third wave of myotome colonization by mitotically competent progenitors: regulating the balance between differentiation and proliferation during muscle development.

The myotome is formed by a first wave of pioneer cells originating from the entire dorsomedial region of epithelial somites and a second wave that derives from all four lips of the dermomyotome but generates myofibers from only the rostral and caudal edges. Because the precedent progenitors exit the cell cycle upon myotome colonization, subsequent waves must account for consecutive growth. In this study, double labeling with CM-DiI and BrdU revealed the appearance of a third wave of progenitors that enter the myotome as mitotically active cells from both rostral and caudal dermomyotome edges. These cells express the fibroblast growth factor (FGF) receptor FREK and treatment with FGF4 promotes their proliferation and redistribution towards the center of the myotome. Yet, they are negative for MyoD, Myf5 and FGF4, which are, however, expressed in myofibers. The proliferating progenitors first appear around the 30-somite stage in cervical-level myotomes and their number continuously increases, making up 85% of total muscle nuclei by embryonic day (E)4. By this stage, generation of second-wave myofibers, which also enter from the extreme lips is still under way. Formation of the latter fibers peaks at 30 somites and progressively decreases with age until E4. Thus, cells in these dermomyotome lips generate simultaneously distinct types of muscle progenitors in changing proportions as a function of age. Consistent with a heterogeneity in the cellular composition of the extreme lips, MyoD is normally expressed in only a subset of these epithelial cells. Treatment with Sonic hedgehog drives most of them to become MyoD positive and then to become myofibers, with a concurrent reduction in the proportion of proliferating muscle precursors.

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PubMed2001

The sub-lip domain--a distinct pathway for myotome precursors that demonstrate rostral-caudal migration.

We have previously reported that the myotome is formed by a first wave of pioneer cells generated from all along the dorsomedial portion of the epithelial somite and a second wave of cells issued from all four edges of the dermomyotome. Cells from the extreme rostral and caudal edges directly generate myofibers that elongate towards the opposite pole of each segment and along the pre-existing myotomal scaffold. In contrast, cells from the dorsomedial and ventrolateral lips first reach the extreme edges and then contribute to myofiber formation. The mechanism by which these epithelial cells translocate remained unknown and was the goal of the present study. We have found that epithelial cells along the dorsomedial and ventrolateral lips of the dermomyotome first delaminate into the immediate underlayer of the corresponding lips, the sub-lip domain, then migrate longitudinally along this pathway until reaching the extreme edges from which they differentiate into myofibers. Cells of the sub-lip domain are negative for Pax3 and desmin but express MyoD, Myf5 and FREK, suggesting that they are specific myogenic progenitors.

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PubMed1999

Myotome formation: a multistage process.

The epaxial muscles of the body are localized in a dorsomedial position with respect to the axial structures, attach to the vertebral column and are concerned with maintenance of posture and movements of the vertebral column. The epaxial musculature derives from the myotome, a transient embryonic structure whose formation is initiated at the epithelial somite stage and is accomplished following complete dissociation of the epithelial dermomyotome. Recent results suggest that myotome development is a multistage process, characterized by addition of sequential waves of muscle progenitors. A first wave originates along the medial part of the epithelial somite and gives rise to a primary myotomal structure; a second wave arises from the rostral and caudal lips of the epithelial dermomyotome and from the dorsomedial lip, which contributes indirectly through the rostral and caudal edges, and a third wave which is composed of mitotically active resident progenitors accounts for significant growth of the myotomal mass and for its transition into epaxial muscle. In this review we discuss the origin, migration and known cellular and molecular features that characterize each wave of progenitors that colonize the myotome.

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PubMed1999

Characterization of the early development of specific hypaxial muscles from the ventrolateral myotome.

We have previously found that the myotome is formed by a first wave of pioneer cells generated along the medial epithelial somite and a second wave emanating from the dorsomedial lip (DML), rostral and caudal edges of the dermomyotome (Kahane, N., Cinnamon, Y. and Kalcheim, C. (1998a) Mech. Dev. 74, 59-73; Kahane, N., Cinnamon, Y. and Kalcheim, C. (1998b) Development 125, 4259-4271). In this study, we have addressed the development and precise fate of the ventrolateral lip (VLL) in non-limb regions of the axis. To this end, fluorescent vital dyes were iontophoretically injected in the center of the VLL and the translocation of labeled cells was followed by confocal microscopy. VLL-derived cells colonized the ventrolateral portion of the myotome. This occurred following an early longitudinal cell translocation along the medial boundary until reaching the rostral or caudal dermomyotome lips from which fibers emerged into the myotome. Thus, the behavior of VLL cells parallels that of their DML counterparts which colonize the opposite, dorsomedial portion of the myotome. To precisely understand the way the myotome expands, we addressed the early generation of hypaxial intercostal muscles. We found that intercostal muscles were formed by VLL-derived fibers that intermingled with fibers emerging from the ventrolateral aspect of both rostral and caudal edges of the dermomyotome. Notably, hypaxial intercostal muscles also contained pioneer myofibers (first wave) showing for the first time that lateral myotome-derived muscles contain a fundamental component of fibers generated in the medial domain of the somite. In addition, we show that during myotome growth and evolution into muscle, second-wave myofibers progressively intercalate between the pioneer fibers, suggesting a constant mode of myotomal expansion in its dorsomedial to ventrolateral extent. This further suggests that specific hypaxial muscles develop following a consistent ventral expansion of a 'compound myotome' into the somatopleure.

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PubMed1998

The origin and fate of pioneer myotomal cells in the avian embryo.

The ontogeny of the myotome was investigated using [3H]thymidine or Brdu treatment in conjunction with 1,1', di-octadecyl-3, 3, 3', 3',-tetramethylindo-carbocyanine perchlorate (DiI) labeling and expression of specific markers. We have identified a subset of early post-mitotic cells that is present in the dorsomedial aspect of epithelial somites and is homogeneously distributed along their entire rostrocaudal extent. The post-mitotic quality of this cell subset enabled us to trace their fate in time-course experiments. Following initial somite dissociation, this epithelial post-mitotic layer bends underneath the medial portion of the nascent dermomyotome. Then, these cells progressively lose epithelial arrangement and migrate in a rostral direction where they accumulate temporarily. Subsequently, these early post-mitotic precursors extend processes that reach both rostral and caudal edges of each segment. Medial somite-derived myofibers also fill the entire mediolateral extent of the segment and reach the dorsomedial lip of the dermomyotome, thus forming the primary myotome. During this process, their large nuclei localize to a narrow stripe in the middle of the nascent myotome. Consistent with the proliferation studies, DiI labeling of the medial epithelial somite cells gave rise to a primary myotomal structure, and continuous pulsing of the DiI-injected embryos with radioactive thymidine revealed that these fibers indeed developed from post-mitotic progenitors. As these early post-mitotic cells that arise prior to somite dissociation are the first wave of progenitors that constitutes the myotome, we have termed them avian muscle pioneers. We propose that the primary myotome formed by the muscle pioneers constitutes a longitudinal scaffold that serves as a substrate for the addition of subsequent waves of myotomal cells.

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PubMed1998

The cellular mechanism by which the dermomyotome contributes to the second wave of myotome development.

We have shown that a subset of early postmitotic progenitors that originates along the medial part of the epithelial somite gives rise to the primary myotome (Kahane, N., Cinnamon, Y. and Kalcheim, C. (1998). Mech. Dev. 74, 59-73). Because of its postmitotic nature, further myotome expansion must be achieved by cell addition from extrinsic sources. Here we investigate the mechanism whereby the dermomyotome contributes to this process. Using several different methods we found that cell addition occurs from both rostral and caudal edges of the dermomyotome, but not directly from its dorsomedial lip (DML). First, labeling of quail embryos with [3H]thymidine revealed a time-dependent entry of radiolabeled nuclei into the myotome from the entire rostral and caudal lips of the dermomyotome, but not from the DML. Second, fluorescent vital dyes were injected at specific sites in the dermomyotome lips and the fate of dye-labeled cells followed by confocal microscopy. Consistent with the nucleotide labeling experiments, dye-labeled myofibers directly emerged from injected epithelial cells from either rostral or caudal lips. In contrast, injected cells from the DML first translocated along the medial boundary, reached the rostral or caudal dermomyotome lips and only then elongated into the myotome. These growing myofibers had always one end attached to either lip from which they elongated in the opposite direction. Third, following establishment of the primary myotome, cells along the extreme dermomyotome edges, but not the DML, expressed QmyoD, supporting the notion that rostral and caudal boundaries generate myofibers. Fourth, ablation of the DML had only a limited effect on myotomal cell number. Thus, cells deriving from the extreme dermomyotome lips contribute to uniform myotome growth in the dorsoventral extent of the myotome. They also account for its expansion in the transverse plane and this is achieved by myoblast addition in a lateral to medial direction (from the dermal to the sclerotomal sides), restricting the pioneer myofibers to the dermal side of the myotome. Taken together, the data suggest that myotome formation is a multistage process. A first wave of pioneers establishes the primary structure. A second wave generated from specific dermomyotome lips contributes to its expansion. Because dermomyotome lip progenitors are mitotically active within the epithelia of origin but exit the cell cycle upon myotome colonization, they can only provide for limited myotome growth and subsequent waves must take over to ensure further muscle development.

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PubMed1996

Origin of primordial germ cells in the prestreak chick embryo.

The temporal and spatial pattern of segregation of the avian germline from the formation of the area pellucida to the beginning of primitive streak formation (stages VII-XIV, EG&K) was investigated using the culture of whole embryos and central and peripheral embryo fragments on vitelline membranes at stages VII-IX, immunohistological analysis of whole mount embryos and sections with monoclonal antibodies MC-480 against stage-specific embryonic antigen-1 (SSEA-1) and EMA-1, and with the culture of dispersed blastoderms at stages IX-XIV with and without on STO feeder layer. Whole embryos at intrauterine stages developed up to the formation of the primitive streak despite the absence of area pellucida expansion. Primordial germ cells (PGCs) appeared in the cultures of whole embryos and only in central fragments containing a partially formed area pellucida at stages VII-IX. When individual stage IX-XIV embryos were dispersed and cultured without a feeder layer, 25-45 PGCs/embryo were detected only with stage X-XIV, but not with stage IX blastoderms. However, the culture of dispersed cells from the area pellucida of stages IX-XIII on STO feeder layers yielded about 150 PGCs/embryo. The carbohydrate epitopes recognized by anti-SSEA-1 and EMA-1 first appeared at stage X on cells in association with polyingressing cells on the ventral surface of the epiblast and later on the dorsal surface of the hypoblast. The SSEA-1-positive hypoblast cells gave rise to chicken PGCs when cultured on a feeder layer of quail blastodermal cells. From these observations, we propose that the segregation and development of avian germline is a gradual, epigenetic process associated with the translocation of SSEA-1/EMA-1-positive cells from the ventral surface of the area pellucida at stage X to the dorsal side of the hypoblast at stages XI-XIV.

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