Biomedical subjects

G Minowada

Publications and source records attributed to G Minowada.

6 recordsLinked to original sources

PubMed1999

Vertebrate Sprouty genes are induced by FGF signaling and can cause chondrodysplasia when overexpressed.

The Drosophila sprouty gene encodes an antagonist of FGF and EGF signaling whose expression is induced by the signaling pathways that it inhibits. Here we describe a family of vertebrate Sprouty homologs and demonstrate that the regulatory relationship with FGF pathways has been conserved. In both mouse and chick embryos, Sprouty genes are expressed in intimate association with FGF signaling centers. Gain- and loss-of-function experiments demonstrate that FGF signaling induces Sprouty gene expression in various tissues. Sprouty overexpression obtained by infecting the prospective wing territory of the chick embryo with a retrovirus containing a mouse Sprouty gene causes a reduction in limb bud outgrowth and other effects consistent with reduced FGF signaling from the apical ectodermal ridge. At later stages of development in the infected limbs there was a dramatic reduction in skeletal element length due to an inhibition of chondrocyte differentiation. The results provide evidence that vertebrate Sprouty proteins function as FGF-induced feedback inhibitors, and suggest a possible role for Sprouty genes in the pathogenesis of specific human chondrodysplasias caused by activating mutations in Fgfr3.

Amino Acid Sequence↗

PubMed1996

Roles for FGF8 in the induction, initiation, and maintenance of chick limb development.

We provide evidence that FGF8 serves as an endogenous inducer of chick limb formation and that its expression in the intermediate mesoderm at the appropriate time and place to trigger forelimb development is directly linked to the mechanism of embryonic kidney differentiation. One function of the limb inducer is to initiate Fgf8 gene expression in the ectoderm overlying the prospective limb-forming territories. FGF8 secreted by the ectoderm then appears to initiate limb bud formation by promoting outgrowth of and Sonic hedgehog expression in the underlying lateral plate mesoderm. FGF8 also maintains mesoderm outgrowth and Sonic hedgehog expression in the established limb bud. Our data thus point to FGF8 as a key regulator of limb development that not only induces and initiates the formation of a limb bud, but also sustains its subsequent development.

Amino Acid Sequence↗

PubMed1996

The chick limbless mutation causes abnormalities in limb bud dorsal-ventral patterning: implications for the mechanism of apical ridge formation.

In chick embryos homozygous for the limbless mutation, limb bud outgrowth is initiated, but a morphologically distinct apical ridge does not develop and limbs do not form. Here we report the results of an analysis of gene expression in limbless mutant limb buds. Fgf4, Fgf8, Bmp2 and Msx2, genes that are expressed in the apical ridge of normal limb buds, are not expressed in the mutant limb bud ectoderm, providing molecular support for the hypothesis that limb development fails in the limbless embryo because of the inability of the ectoderm to form a functional ridge. Moreover, Fgf8 expression is not detected in the ectoderm of the prospective limb territory or the early limb bud of limbless embryos. Since the early stages of limb bud outgrowth occur normally in the mutant embryos, this indicates that FGF8 is not required to promote initial limb bud outgrowth. In the absence of FGF8, Shh is also not expressed in the mutant limb buds, although its expression can be induced by application of FGF8-soaked beads. These observations support the hypothesis that Fgf8 is required for the induction of Shh expression during normal limb development. Bmp2 expression was also not detected in mutant limb mesoderm, consistent with the hypothesis that SHH induces its expression. In contrast, SHH is not required for the induction of Hoxd11 or Hoxd13 expression, since expression of both these genes was detected in the mutant limb buds. Thus, some aspects of mesoderm A-P patterning can occur in the absence of SHH and factors normally expressed in the apical ridge. Intriguingly, mutant limbs rescued by local application of FGF displayed a dorsalized feather pattern. Furthermore, the expression of Wnt7a, Lmx1 and En1, genes involved in limb D-V patterning, was found to be abnormal in mutant limb buds. These data suggest that D-V patterning and apical ridge formation are linked, since they show that the limbless mutation affects both processes. We present a model that explains the potential link between D-V positional information and apical ridge formation, and discuss the possible function of the limbless gene in terms of this model.

Animals↗

PubMed1995

Variation in the expression and/or phosphorylation of the human low molecular weight stress protein during in vitro cell differentiation.

Members of the low molecular weight heat shock protein (hsp) family show regulated expression in both Drosophila and mice during development and differentiation. Here we have examined whether similar regulation of the single low molecular weight hsp (hsp 28) of humans exhibits differences in either its expression and/or phosphorylation during the course of in vitro differentiation of hematopoietic cells. In the promyelocytic leukemic cell line, HL-60, we show that early after commitment of the cells to a macrophage-like phenotype (via exposure to phorbol ester myristate, PMA) there occurs an accompanying increased phosphorylation of hsp 28. Over time and as the cells become terminally differentiated the levels of hsp 28 increase significantly. In contrast, cells stimulated to adopt a granulocyte-like phenotype (e.g. exposed to either dimethyl sulfoxide or retinoic acid) show no changes in either the phosphorylation or expression of hsp 28. Moreover, once differentiated the granulocyte-like cells no longer appear capable of phosphorylating hsp 28. Human K562 cells, in response to hemin, rapidly increase their expression and phosphorylation of hsp 28 during the course of their differentiation into erythroid-like cells. Addition of PMA to the K562 cells induces differentiation into a megakaryocyte-like phenotype but is not accompanied by changes in hsp 28 phosphorylation/expression. In the case of the HL-60 cells, differentiation toward the macrophage like lineage is accompanied by an increased adherence of the cells to their substratum and an apparent association of hsp 28 with the actin cytoskeleton.

Actins↗

PubMed1995

Clinical implications of the stress response.

A field of research that began with a curious observation in Drosophila has resulted in a new understanding of how cells respond to sudden and adverse changes in their environment. In addition through the study of the structure/function of the stress proteins, especially those which function as molecular chaperones, new insights into the details by which proteins are synthesized and acquire their final biologically active conformation have been realized. Equally exciting is the progress being made as it relates the potential diagnostic and therapeutic applications of the stress-response proteins. The use of stress proteins as the next generation of vaccines and/or their use as potentially powerful adjuvants, capable of stimulating both T and B cell responses to a particular antigen of interest appear close to becoming a reality. One wonders how many more surprises are in store for us as we continue to explore this evolutionally conserved cellular stress response.

Adaptation, Physiological↗

PubMed1984

Recognition of HLA-A2 and -B7 antigens by cloned cytotoxic T lymphocytes after gene transfer into human and monkey, but not mouse, cells.

The genes that code for the human major histocompatibility class I antigens, HLA-A2 and HLA-B7, were introduced into human, monkey, and mouse cell lines by cotransfection with suitable biochemical markers and the fluorescence-activated cell sorter was used to identify and/or select stable cell populations expressing high surface levels of these antigens. Levels of expression obtained were similar to those observed for endogenous HLA antigens on various human cell lines and were 25-80% of those observed on the human B-lymphoblastoid cell line JY. Serologically defined HLA-A2 and HLA-B7 polymorphic determinants remained intact on all transfected recipient cells analyzed. Cloned human allospecific cytotoxic T lymphocytes (CTL) specific for HLA-A2 or HLA-B7 were capable of lysing appropriate HLA-transfected human cells with comparable efficiency to JY cell lysis. Two of 10 CTL clones lysed appropriate monkey cell transfectants with approximately equal to 20% the efficiency of human cell transfectants. No specific lysis of any HLA-transfected mouse cell lines, including a B cell lymphoma, was observed despite comparable levels of surface antigen expression or after induction of higher levels by mouse gamma-interferon. Furthermore, L cells expressing human beta 2-microglobulin in addition to HLA-A2 or -B7 were not lysed by these CTL. Thus, an additional species-specific component may be involved in lysis by allogeneic CTL--possibly related to the function(s) of other surface proteins on target cells.

Animals↗