Biomedical subjects

M Ruiz-Gómez

Publications and source records attributed to M Ruiz-Gómez.

12 recordsLinked to original sources

PubMed2001

A distinct set of founders and fusion-competent myoblasts make visceral muscles in the Drosophila embryo.

The embryonic Drosophila midgut is enclosed by a latticework of longitudinal and circular visceral muscles. We find that these muscles are syncytial. Like the somatic muscles they are generated by the prior segregation of two populations of cells: fusion-competent myoblasts and founder myoblasts specialised to seed the formation of particular muscles. Visceral muscle founders are of two classes: those that seed circular muscles and those that seed longitudinal muscles. These specialisations are revealed in mutant embryos where myoblast fusion fails. In the absence of fusion, founders make mononucleate circular or longitudinal fibres, while their fusion-competent neighbours remain undifferentiated.

Animals↗

PubMed2000

Drosophila dumbfounded: a myoblast attractant essential for fusion.

Aggregation and fusion of myoblasts to form myotubes is essential for myogenesis in many organisms. In Drosophila the formation of syncytial myotubes is seeded by founder myoblasts. Founders fuse with clusters of fusion-competent myoblasts. Here we identify the gene dumbfounded (duf) and show that it is required for myoblast aggregation and fusion. duf encodes a member of the immunoglobulin superfamily of proteins that is an attractant for fusion-competent myoblasts. It is expressed by founder cells and serves to attract clusters of myoblasts from which myotubes form by fusion.

Amino Acid Sequence↗

PubMed1998

Muscle patterning and specification in Drosophila.

There are obvious differences in the way sense organs and muscles are generated during Drosophila embryogenesis. For example, all the cells that compose the final sense organ are derived from a unique cell through a well-established lineage, whereas each muscle is formed by fusion of myoblasts that belong to two different populations: a founder cell and a pool of fusion competent cells. Despite these differences, similar genes and mechanisms appear to be involved in the generation of the pattern of sense organs and in muscle development. Thus, the process of specifying individual cells and endowing them with the ability to initiate neuronal or muscle development, as well as the acquisition of alternative fates among sibling cells, appear to be under similar genetic control both in neural and muscle development.

Animals↗

PubMed1998

[Type II lissencephaly: presentation of intermediate form].

CLINICAL CASE: A 35-week new born with cerebral dysplasia (type II lissencephaly) and muscular dystrophy is reported. The central nervous system (CNS) findings were typical of those previously described in lissencephalic cerebromuscular disorders, and were characterized by global lissencephaly, hydrocephalus, and cerebral cortical dysplasia. The eyes appeared normal on examination and no encephalocele was found. The changes in the CNS in Walker-Warburg syndrome are similar to, but more severe than those found in Fukuyama congenital muscular dystrophy, and both represent a failure of constraint of neuronal migration. Whether the syndromes characterized by cerebro-ocular dysplasia and muscular dystrophy are genetically heterogeneous or allelic variations is controversial. Our case is a form of presentation between Fukuyama and Walker-Warburg syndrome in a family with fourth affected children. CONCLUSION: In our opinion, cases as the ours supports the theory that Fukuyama and Walker-Warburg could be genetically allelic.

Brain↗

PubMed1997

Specific muscle identities are regulated by Krüppel during Drosophila embryogenesis.

During Drosophila embryogenesis, mesodermal cells are recruited to form a complex pattern of larval muscles. The formation of the pattern is initiated by the segregation of a special class of founder myoblasts. Single founders fuse with neighbouring nonfounder myoblasts to form the precursors of individual muscles. Founders and the muscles that they give rise to have specific patterns of gene expression and it has been suggested that it is the expression of these founder cell genes that determines individual muscle attributes such as size, shape, insertion sites and innervation. We find that the segmentation gene Krüppel is expressed in a subset of founders and muscles, regulates specific patterns of gene expression in these cells and is required for the acquisition of proper muscle identity. We show that gain and loss of Krüppel expression in sibling founder cells is sufficient to switch these cells, and the muscles that they give rise to, between alternative cell fates.

Animals↗

PubMed1995

groucho and hedgehog regulate engrailed expression in the anterior compartment of the Drosophila wing.

Drosophila imaginal discs are divided into units called compartments. Cells belonging to the same compartment are related by lineage and express a characteristic set of 'selector genes'. The borders between compartments act as organizing centres that influence cell growth within compartments. Thus, in the cells immediately anterior to the anterior-posterior compartment boundary the presence of the hedgehog product causes expression of decapentaplegic, which, in turn, influences the growth and patterning of the wing disc. The normal growth of the disc requires that posterior-specific genes, such as hedgehog and engrailed are not expressed in cells of the anterior compartment. Here we show that hedgehog can activate engrailed in the anterior compartment and that both hedgehog and engrailed are specifically repressed in anterior cells by the activity of the neurogenic gene groucho. In groucho mutant discs, hedgehog and engrailed are expressed at the dorsoventral boundary of the anterior compartment, leading to the ectopic activation of decapentaplegic and patched and to a localised increase in cell growth associated with pattern duplications. The presence of engrailed in the anterior compartment causes the transformation of anterior into posterior structures.

Animals↗

PubMed1994

The helix-loop-helix extramacrochaetae protein is required for proper specification of many cell types in the Drosophila embryo.

The Drosophila Extramacrochaetae protein antagonizes the proneural function of the Achaete and Scute proteins in the generation of the adult fly sensory organs. Extra-macrochaetae sequesters these basic-region-helix-loop-helix transcription factors as heterodimers inefficient for binding to DNA. We show that, during embryonic development, the extramacrochaetae gene is expressed in complex patterns that comprise derivatives of the three embryonic layers. Expression of extramacrochaetae often precedes and accompanies morphogenetic movements. It also occurs at regions of specialized cell-cell contact and/or cell recognition, like the epidermal part of the muscle attachment sites and the differentiating CNS. The insufficiency of extramacrochaetae affects most tissues where it is expressed. The defects suggest faulty specification of different cell types and result in impairment of processes as diverse as cell proliferation and commitment, cell adhesion and cell recognition. If Extramacrochaetae participates in cell specification by dimerizing with basic-region-helix-loop-helix proteins, the variety of defects and tissues affected by the insufficiency of extramacrochaetae suggests that helix-loop-helix proteins are involved in many embryonic developmental processes.

Animals↗

PubMed1993

The expression and role of a proneural gene, achaete, in the development of the larval nervous system of Drosophila.

The proneural genes of Drosophila are required for the segregation of neural precursors from the ectoderm. One of the proneural genes, achaete (ac), is responsible for the formation of a subset of larval and adult sense organs. We have examined the pattern of expression of ac and its regulation during embryogenesis. ac is expressed at particular locations of the ectoderm according to a highly dynamic and complex pattern. At each location the expression of ac occurs in two stages. First, ac is expressed in a cluster of cells ('competent' stage). This pattern of expression depends on an array of cis-regulatory sites which promote the expression of ac in clusters of cells at particular locations. Second, one cell of each cluster accumulates ac transcripts at a high level ('determined' stage) and becomes the neural progenitor cell. The restriction of the determined stage to one cell of the cluster requires the gene Notch. The transactivation of ac by sc (scute) or by other genes of the achaete-scute complex (AS-C) plays no role in defining the initial pattern of expression of ac, but might play a role in the shift from the competent to the determined level. We propose that the requirements of particular sense organs for different AS-C genes reflect the organization of this gene complex, rather than functional differences between the genes.

Animals↗

PubMed1993

Molecular characterization of the lethal of scute genetic function.

The lethal of scute (l'sc) genetic function, which plays an essential role in the early development of the central nervous system of the Drosophila embryo, is localized within the achaete-scute complex (AS-C). Several lines of evidence have suggested that the AS-C T3 transcription unit corresponds to the l'sc function. We demonstrate that short fragments of DNA, containing the T3 transcribed region and a few kilobases of flanking sequences, rescue, albeit partially, the lethality and neural phenotype of l'sc deletions. Still, the complex wild-type pattern of expression of T3 is not reproduced by the transduced genes. This depends on cis-control elements scattered within the entire AS-C DNA and intermingled with regulatory elements specific for other AS-C transcription units. These elements are necessary for the initial activation of T3 in the neuroectoderm, probably mediated by axis-patterning genes. The presence of a cluster of E-boxes, upstream of the T3 transcribed region, suggests another level of control of T3 expression by basic-helix-loop-helix proteins, among them its own gene product.

Amino Acid Sequence↗

PubMed1990

Competence to develop sensory organs is temporally and spatially regulated in Drosophila epidermal primordia.

The Drosophila adult cuticle displays a stereotyped pattern of sensory organs (SOs). Its deployment requires the expression of the achaete (ac) and scute (sc) genes. Their products confer to cells of epidermal primordia (imaginal discs and histoblasts) the ability to become SO precursors (SOPs). In imaginal discs, ac and sc expression is spatially restricted to cell clusters within which one or a few cells become SOP(s). With the help of ubiquitous sc expression provided at different developmental times by a heat shock-sc (HSSC) chimeric gene, we have analyzed the response of epidermal primordia to the proneural action of the sc product, and have tested whether the patterned distribution of ac/sc products is necessary to position SOs correctly within the epidermis. Each primordium responds to HSSC expression by developing SOs only during a characteristic developmental period. In the absence of the endogenous ac and sc genes, most SOs induced by HSSC are of the correct type and are located in wild type positions. These results indicate that the capacity of primordia to respond to sc is temporally and spatially regulated, that specification of the type of SO does not depend on ac/sc, and that SO positioning utilizes topological information independent of the spatially restricted distribution of ac/sc products.

Abdomen↗

PubMed1988

A unitary basis for different Hairy-wing mutations of Drosophila melanogaster.

Hairy-wing (Hw) mutations are caused by modifications of the achaete-scute complex (AS-C) which promote development of extra sensory organs on the cuticle of Drosophila melanogaster. We show that the extreme Hw49c allele contains an inversion with a breakpoint within the AS-C, while the weak Hw685 allele is associated with a terminal deletion of the X chromosome which removes the achaete region of the AS-C. In both cases, foreign DNA in contact with the breakpoints presumably enhances expression of AS-C genes. Overexpression of achaete (T5) or scute alpha (T4) genes was previously found in Hw mutants associated with insertions of transposable elements (Hw1, HwBS and HwUa, Campuzano et al., 1986). In situ hybridizations to Hw49c and Hw1 larval sections show that the overexpression causes an abnormally generalized distribution of T4 and/or T5 transcripts in imaginal discs. Such distribution correlates with development of extra sensory organs in ectopic positions. We also show that in Hw685 a moderate overexpression of the T4 gene largely replaces the absence of the T5 gene in the development of the notum chaetae pattern. We propose that overexpression of T4/T5 genes in normal or ectopic positions is at the basis of the Hw effect.

Animals↗

PubMed1987

Deletion analysis of the achaete-scute locus of Drosophila melanogaster.

The achaete-scute gene complex (AS-C) is involved in the development of the central and peripheral (sensory chaetae, sensilla) nervous system. To assess the contribution of the different parts of the complex in the generation of the adult chaetae pattern, we have determined the phenotypes and molecular positions of the breakpoints of 74 terminal deficiencies of the X chromosome. According to these and previous data, the AS-C is organized, distally to proximally, as follows: the achaete region, with most of its DNA (10 kb) located upstream from the putative achaete (T5) gene; an intermediate region, approximately 18 kb long, whose deletion only weakly affects the scute function; and the scute region, with most of the DNA critical for its function extending 4-5 kb upstream and 50 kb downstream of the putative scute (T4) gene. The DNA extending far upstream of the T5 gene and downstream of the T4 gene may provide chromatin conformations adequate for efficient expression of these genes. However, in the case of the T4 gene, the available data suggest the presence of a small number of elements, scattered in the long downstream region, that would respond to topological cues and cis-activate this gene in specific anatomical regions.

Animals↗