Cloning of the cDNA encoding a myosin heavy chain B isoform of Xenopus nonmuscle myosin with an insert in the head region.

Bhatia‐Dey, Naina; Adelstein, Robert S.; Dawid, Igor B.

doi:10.1073/pnas.90.7.2856

Cited by 23 publications

(14 citation statements)

References 28 publications

(20 reference statements)

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“…In Xenopus, myosin IIB is the best candidate to be involved in CE because MHC-B mRNA is expressed in dorsal mesoderm and is upregulated by activin in animal cap experiments (Bhatia-Dey et al, 1993;Bhatia-Dey et al, 1998;Kelley et al, 1996), and thus is expressed at the right time and place for involvement in CE of presumptive mesoderm. We find that myosin IIB is required for normal blastopore closure by operating in the process of CE at the dorsal lip.…”

Section: Convergence and Extension At Gastrulation Require A Myosin Imentioning

confidence: 99%

Convergence and extension at gastrulation require a myosin IIB-dependent cortical actin network

et al. 2008

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Force-producing convergence (narrowing) and extension (lengthening) of tissues by active intercalation of cells along the axis of convergence play a major role in axial morphogenesis during embryo development in both vertebrates and invertebrates, and failure of these processes in human embryos leads to defects including spina bifida and anencephaly. Here we use Xenopus laevis, a system in which the polarized cell motility that drives this active cell intercalation has been related to the development of forces that close the blastopore and elongate the body axis, to examine the role of myosin IIB in convergence and extension. We find that myosin IIB is localized in the cortex of intercalating cells, and show by morpholino knockdown that this myosin isoform is essential for the maintenance of a stereotypical, cortical actin cytoskeleton as visualized with time-lapse fluorescent confocal microscopy. We show that this actin network consists of foci or nodes connected by cables and is polarized relative to the embryonic axis, preferentially cyclically shortening and lengthening parallel to the axis of cell polarization, elongation and intercalation, and also parallel to the axis of convergence forces during gastrulation. Depletion of MHC-B results in disruption of this polarized cytoskeleton, loss of the polarized protrusive activity characteristic of intercalating cells, eventual loss of cell-cell and cell-matrix adhesion, and dose-dependent failure of blastopore closure, arguably because of failure to develop convergence forces parallel to the myosin IIB-dependent dynamics of the actin cytoskeleton. These findings bridge the gap between a molecular-scale motor protein and tissue-scale embryonic morphogenesis.

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Section: Convergence and Extension At Gastrulation Require A Myosin Imentioning

confidence: 99%

Convergence and extension at gastrulation require a myosin IIB-dependent cortical actin network

et al. 2008

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“…MHC-IIB(B2) is not expressed in Xenopus tissues, whereas MHC-IIB(B1) is constitutively expressed in all Xenopus tissues (Bhatia-Dey et al, 1993), suggesting that MHC-IIB(B2) might have started to be expressed in the brain, except for the forebrain, after the amphibian period. Thereafter, the distribution of this inserted isoform may have extended to the cerebrum sometime after the appearance of mammals.…”

Section: Discussionmentioning

confidence: 99%

“…They are referred to as MHC-A and MHC-B or MHC-IIA and MHC-IIB. The entire cDNA sequence encoding both isoforms has been determined for the chicken (Shohet et al, 1989;Takahashi et al, 1992), human (Saez et al, 1990;Simons et al, 1991;Toothaker et al, 1991;Phillips et al, 1995), Xenopus (Bhatia-Dey et al, 1993 and the sequence of MHC-IIA alone for the rat (Choi et al, 1996). These two isoforms are expressed in a tissue-dependent manner.…”

Section: Introductionmentioning

confidence: 99%

Species Differences in the Distribution of the Nonmuscle Myosin Heavy Chain IIB Inserted Isoform in the Brain

2001

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The alternatively spliced isoform of the nonmuscle myosin heavy chain IIB (MHC-IIB) with an insert of 21 amino acids near the actin-binding region, MHC-IIB(B2), is expressed specifically in the brain and spinal cord in Mammalia and Aves. We performed immunoblot analyses to elucidate the distribution of MHC-IIB(B2) in the brains of various animals. Nearly half of MHC-IIB existed as the B2 inserted isoform (MHC-IIB(B2)) in the cerebrum of the guinea-pig, rabbit and pig, while the non-B2 inserted isoform (MHCIIB(ΔB2)) was the dominant form in the cerebrum of the rat, mouse and hamster. In the guinea-pig, the amount of MHC-IIB(B2) expressed in the cerebrum was low compared to MHC-IIB(ΔB2) during the first postnatal week, but it increased to comparable levels during postnatal development. In the rat, the amount of MHC-IIB(B2) protein in the cerebrum remains low compared to its expression elsewhere in the brain throughout life. Our results regarding the distribution of MHC-IIB(B2) in the adult brain lead us to classify species into two types; one type expresses significantly less MHC-IIB(B2) in the cerebrum than in other portions of the brain, and the second type expresses it at comparable levels throughout the brain. Based on these results, we hypothesize that MHC-IIB(B2) modulates the role of MHC-IIB(ΔB2) in the regulation of synaptic structure and function in the mature brain, and that the requirements for such function by MHC-IIB(B2) have shifted gradually from the cerebellum to the cerebrum with evolutionary increases in brain size

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“…The insert is located near the so-called 25/50-kDa junction of the myosin head, in a region that is likely to be a flexible loop in the myosin head at one end of the active-site pocket (39). However, small inserts (on the order of 7-10 amino acids) in a similar position have been reported in nonmuscle and smooth muscle myosin Ils (40)(41)(42). The inserts in the myosin Ils appear similar to each other (see figure 3 in ref.…”

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confidence: 99%

Discovery of myosin genes by physical mapping in Dictyostelium.

Titus

Kuspa

Loomis

1994

Proc. Natl. Acad. Sci. U.S.A.

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The diversity of the myosin family in a single organism, Dictyostelium discoideum, has been investigated by a strategy devised to rapidly identify and clone additional members of a gene family. An ordered array of yeast artificial chromosome clones that encompasses the Dictyostelium genome was probed at low stringency with conserved regions of the myosin motor domain to identify all possible myosin loci. The previously identified myosin loci (mchA, myoA-E) were detected by hybridization to the probes, as well as an additional seven previously unidentified loci (referred to as myoF-L). Clones corresponding to four of these additional loci (myoF, myoH-J) were obtained by using the isolated yeast artificial chromosomes as templates in a PCR employing degenerate primers specific for conserved regions of the myosin head. Sequence analysis and physical mapping of these clones confirm that these PCR products are derived from four previously unidentifie myosin genes. Preliminary analysis of these sequences suggests that at least one of the genes (myoJ) encodes a member of a potentially different class of myosins. With The recent discovery of an array of unconventional myosins in a wide variety of organisms and cell types (1, 2) has redefined the traditional view of the nature of cellular actinbased movements. Critical to understanding the range of actin-based movements carried out by a single cell is full knowledge of the myosins expressed by that cell. The highly motile Dictyostelium is ideally suited to studies of the myosin family. A total of six myosin genes have previously been identified, and these fall into two classes, myosin I and the conventional myosin (also referred to as myosin II) (3-7). The conventional myosin has been found to play a key role in cytokinesis, morphogenesis, and capping of cell-surface receptors (8). However, the exclusive role of the conventional myosin in cellular motility has been brought into question by several different investigations. Dictyostelium mutants lacking the conventional myosin heavy chain are still able to move on a substrate and form streams during development, although movement of individual cells is somewhat aberrant (9), suggesting that other motors may play an important role. The individual elimination of two myosin I genes, myoA and myoB, results in similar mild, yet significant, alterations in pseudopod dynamics (10,11), suggesting that these two motor proteins share common roles in the formation ofcellular extensions. The existence ofat least five myosin I genes in this organism, coupled with the existence of additional bands detected on Southern blots that could not be accounted for on the basis of the known myosin genes (5, 6), indicated that the Dictyostelium myosin gene family is large and that all members had not yet been identified. We have investigated the full extent of the myosin gene family in Dictyostelium using a strategy that combines low-stringency hybridization, physical mapping techniques, and the PCR to detect and partially characterize ...

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Cloning of the cDNA encoding a myosin heavy chain B isoform of Xenopus nonmuscle myosin with an insert in the head region.

Cited by 23 publications

References 28 publications

Convergence and extension at gastrulation require a myosin IIB-dependent cortical actin network

Convergence and extension at gastrulation require a myosin IIB-dependent cortical actin network

Species Differences in the Distribution of the Nonmuscle Myosin Heavy Chain IIB Inserted Isoform in the Brain

Discovery of myosin genes by physical mapping in Dictyostelium.

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