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Biomedical subjects

Q T Wang

Publications and source records attributed to Q T Wang.

10 recordsLinked to original sources
PubMed2006

FGF ligand family mRNA expression profile for mouse preimplantation embryos, early gestation human placenta, and mouse trophoblast stem cells.

Signaling by fibroblast growth factor (FGF) is essential is for trophoblast stem (TS) cells and preimplantation embryos. FGF4 provides essential signaling, but the expression of the complete set of 23 FGF family members has not been analyzed. Here, semi-quantitative RT-PCR and microarray analyses were used to define expression of all FGF ligand mRNA. RT-PCR was done for developmentally important FGF subfamilies, FGF10/FGF22 and FGF8/FGF17/FGF18 as well as FGF11. FGF4 and FGF18 are detected at highest levels by RT-PCR and microarrays. FGF10 was detected at low levels in both assays. FGF11 was detected at moderate levels by microarray, but not by RT-PCR. FGF17 was detected at low levels by array and moderate levels by RT-PCR. FGF8 and FGF22 were detected by RT-PCR, but not by microarrays during late cleavage divisions. FGF8, FGF5, and FGF9 were detected in the oocyte by microarray. FGF2, FGF3, and FGF7 were not detected by RT-PCR or microarrays and FGF13, FGF14, and FGF23 were not detected by microarray. Since a major role of FGF is to maintain TS cells, we tested human and mouse placental cell lines and early gestation human placenta for expression of FGF ligands. Expression in mouse TS cells was compared with preimplantation embryos, and human placental cell line expression was compared with human placenta, to infer which ligands are expressed in placental lineage vs. other cell lineages. The data suggest that human and mouse placenta share FGF18 and its high expression suggests preimplantation and early placental function.

Animals↗
PubMed2001

Genetic dissection of the Drosophila Cubitus interruptus signaling complex.

Much of our understanding of the Hedgehog (Hh) signaling pathway comes from Drosophila, where a gradient of Hh signaling regulates the function of the transcription factor Cubitus interruptus (Ci) at three levels: protein stabilization, nuclear import, and activation. Regulation of Ci occurs in a cytoplasmic complex containing Ci, the kinesin-like protein Costal-2 (Cos2), the serine-threonine kinase Fused (Fu), and the Suppressor of Fused [Su(fu)] protein. The mechanisms by which this complex responds to different levels of Hh signaling and establishes distinct domains of gene expression are not fully understood. By sequentially mutating components from the Ci signaling complex, their roles in each aspect of Ci regulation can be analyzed. The Cos2-Ci core complex is able to mediate Hh-regulated activation of Ci but is insufficient to regulate nuclear import and cleavage. Addition of Su(fu) to the core complex blocks nuclear import while the addition of Fu restores Hh regulation of Ci nuclear import and proteolytic cleavage. Fu participates in two partially redundant pathways to regulate Ci nuclear import; the kinase function plays a positive role by inhibiting Su(fu), and the regulatory domain plays a negative role in conjunction with Cos2.

Active Transport, Cell Nucleus↗
PubMed2000

Nuclear import of cubitus interruptus is regulated by hedgehog via a mechanism distinct from Ci stabilization and Ci activation.

The Hedgehog (Hh) signal is transduced via Cubitus interruptus (Ci) to specify cell fates in the Drosophila wing. In the absence of Hh, the 155 kDa full-length form of Ci is cleaved into a 75 kDa repressor. Hh inhibits the proteolysis of full-length Ci and facilitates its conversion into an activator. Recently, it has been suggested that Hh promotes Ci nuclear import in tissue culture cells. We have studied the mechanism of Ci nuclear import in vivo and the relationship between nuclear import, stabilization and activation. We found that Ci rapidly translocates to the nucleus in cells close to the anteroposterior (AP) boundary and this rapid nuclear import requires Hh signaling. The nuclear import of Ci is regulated by Hh even under conditions in which Ci is fully stabilized. Furthermore, cells that exhibit Ci stabilization and rapid nuclear import do not necessarily exhibit maximal Ci activity. It has been previously shown that stabilization does not suffice for activation. Consistent with this finding, our results suggest that the mechanisms regulating nuclear import, stabilization and activation are distinct from each other. Finally, we show that cos2 and pka, two molecules that have been characterized primarily as negative regulators of Ci activity, also have positive roles in the activation of Ci in response to Hh.

Animals↗
PubMed1999

The subcellular localization and activity of Drosophila cubitus interruptus are regulated at multiple levels.

Cubitus interruptus (Ci), a Drosophila transcription factor, mediates Hedgehog (Hh) signaling during the patterning of embryonic epidermis and larval imaginal discs. In the absence of Hh signal, Ci is cleaved to generate a truncated nuclear form capable of transcriptional repression. Hh signaling stabilizes and activates the full-length Ci protein leading to strong activation of downstream target genes including patched and decapentaplegic. A number of molecules have been implicated in the regulation of Ci. Mutations in these molecules lead to changes in Ci protein level, the extent of Ci proteolysis and the expression of Ci target genes. This paper examines the regulation of Ci subcellular localization and activity. We first characterize a bipartite nuclear localization signal (NLS) within Ci. We propose that the subcellular distribution of Ci is affected by two opposing forces, the action of the NLS and that of at least two regions targeting Ci to the cytoplasm. Further our data show that loss of PKA or Costal-2 activity does not fully mimic Hh signaling, demonstrating that Ci proteolysis and Ci activation are two distinct events which are regulated through different paths. Finally, we propose that there are three levels of apparent Ci activity, corresponding to three zones along the AP axis with different sets of gene expression and different levels of Hh signaling.

Amino Acid Sequence↗
PubMed1997

Drosophila cubitus interruptus forms a negative feedback loop with patched and regulates expression of Hedgehog target genes.

The Drosophila segment polarity gene cubitus interruptus (ci) encodes a zinc finger protein that is required for the proper patterning of segments and imaginal discs. Epistasis analysis indicates that ci functions in the Hedgehog (Hh) signal transduction pathway and is required to maintain wingless expression in the embryo. In this paper, the role of the Ci protein in the Hh signaling pathway is examined in more detail. Our results show that ectopic expression of ci in imaginal discs and the embryo activates the expression of Hh target genes. One of these target genes, patched, forms a negative feedback loop with ci that is regulated by Hh signal transduction. Activation is also achieved using the Ci zinc finger domain fused to a heterologous transactivation domain. Conversely, repression of Hh target genes occurs in animals expressing the Ci zinc finger domain fused to a repression domain. To examine Ci function in more detail, regions of the Ci protein that are responsible for its ability to transactivate and its subcellular distribution have been identified.

Animals↗
PubMed1992

[The distribution and significance of collagen type III and fibronectin in human gingiva].

Immunohistochemical methods were used to study the distribution and patterns of collagen type III and fibronectin (FN) in human gingiva, their appearance in normal and several periodontal diseases were compared and discussed. It is found that type III collagen and FN are distributed consistently throughout the connective tissue. In inflamed gingiva, both of them are greatly diminished (P < 0.01). It is suggested that they should be in coordination with each other in the maintenance of normal gingiva and the decrease in amount may play a role in the development of periodontal disease.

Adolescent↗
PubMed1991

Reconstruction of the frequency distribution of A- and B-cell size in the pancreatic islets from several animal species--an important stereological operation in QMSOC.

The stereological algorithms for the conversion of the profile-size frequency distribution (PSFD) observed in histological section to the sphere-size frequency distribution (SSFD) in three-dimensional space was developed to a computer program and its practical application was described in this paper. The reconstructions of SSFD were based on the data of PSFD of A- and B-cells measured in sections of the pancreatic islets from ophiocephalus argus, toad, chicken, cat, rabbit and rat. The sizes of both profile and sphere were expressed by their caliper diameters. The experimental results showed that the patterns of SSFD of A- and B-cells from six animal species were somewhat different, and that all the peaks of them, however, occurred in the range from 6 to 12 microns in caliper diameter.

Algorithms↗