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M K Gordon

Publications and source records attributed to M K Gordon.

At least 37 records · Page 2Linked to original sources
PubMed1995

Dynamics of MASH1 expression in vitro and in vivo suggest a non-stem cell site of MASH1 action in the olfactory receptor neuron lineage.

Disruption of the mouse gene encoding the transcription factor MASH1 leads to loss of certain classes of neurons, including receptor neurons of the olfactory epithelium (OE). Here we investigate the nature of the cell type expressing MASH1 in mouse OE by manipulating olfactory receptor neuron (ORN) neurogenesis in vitro and in vivo to alter the dynamics of neuronal production. The results indicate that MASH1 is expressed in cells of the ORN lineage, but not in ORNs themselves nor in their immediate precursors. Data on how changes in the numbers and proliferative states of MASH+ cells correlate with induced changes in overall neurogenesis strongly suggest that MASH1-expressing cells give rise to the immediate precursors of ORNs, but are not the self-renewing stem cells of the OE. The results imply that multiple progenitor stages are employed in generating ORNs and suggest that the action of MASH1 occurs predominantly at an intermediate stage.

Animals↗
PubMed1995

The management of splenic rupture in infectious mononucleosis.

Non-operative management of splenic trauma is now well established; however, the role of conservative management in spontaneous splenic rupture is undetermined. The leading cause of spontaneous splenic rupture is infectious mononucleosis. We report on the management of four patients with spontaneous rupture, in association with infectious mononucleosis. Three patients eventually required splenectomy, and one was successfully managed non-operatively. The comparative risks of operative and non-operative management are discussed. We believe that when splenic rupture complicates infectious mononucleosis, early splenectomy is the most appropriate management.

Adult↗
PubMed1994

Type V collagen and Bowman's membrane. Quantitation of mRNA in corneal epithelium and stroma.

Bowman's membrane is an acellular matrix of the cornea which lies between the epithelial basal lamina and the corneal stroma. By immunoelectron microscopy, we have determined that types I and V collagen are components of the collagen fibrils in Bowman's membrane of the chick cornea. Although these same components are found in the fibrils of the stroma, the fibrils of Bowman's membrane are smaller in diameter and less uniform than those of the stroma. At early stages of development, the corneal epithelium synthesizes the types I and II collagen of the primary stroma. We therefore asked whether it might also be capable of synthesizing the type V collagen found in Bowman's membrane at later stages of development. Our results, using competitive polymerase chain reaction to quantitate mRNA from avian corneal cells, indicate that the amount of alpha 1(V) collagen mRNA present in epithelia, relative to alpha 2(I) collagen mRNA, is greater than that in stromal fibroblasts. We postulate that this enables the epithelium to synthesize a higher ratio of type V to type I collagen than the stroma and that this proportionally higher amount of type V might account for the ultrastructural appearance of the fibrils in Bowman's membrane.

Amino Acid Sequence↗
PubMed1993

Type XIV collagen is encoded by alternative transcripts with distinct 5' regions and is a multidomain protein with homologies to von Willebrand's factor, fibronectin, and other matrix proteins.

The combined nucleotide sequences of several overlapping cDNAs provide the first complete amino acid sequence of type XIV collagen. Independent confirmation of the deduced sequence is provided by amino acid sequencing of several tryptic peptides isolated from purified chicken skin type XIV collagen. Comparative analyses show that the amino-terminal non-triple-helical region of alpha 1(XIV) chains contains sequence motifs that are similar to alpha 1(IX) collagen, fibronectin type III repeats, and von Willebrand's factor A-domains. The results also strongly suggest that the alpha 1(XIV) collagen gene is identical to the gene encoding the matrix component previously named undulin. cDNAs covering the 5' region of alpha 1(XIV) mRNA fall into two classes with distinct sequences in their 5'-untranslated regions. We believe the two alternative sequences result from differential splicing of the primary transcript. Interestingly, one of the untranslated sequences shows a high degree of identity with the cis-regulatory translational control sequence in the 5'-untranslated region of a Drosophila ribosomal protein mRNA. We hypothesize therefore that the sequence in alpha 1(XIV) collagen may play a role in the control of alpha 1(XIV) protein synthesis.

Alternative Splicing↗
PubMed1993

Type V collagen: molecular structure and fibrillar organization of the chicken alpha 1(V) NH2-terminal domain, a putative regulator of corneal fibrillogenesis.

Previous work from our laboratories has demonstrated that: (a) the striated collagen fibrils of the corneal stroma are heterotypic structures composed of type V collagen molecules coassembled along with those of type I collagen, (b) the high content of type V collagen within the corneal collagen fibrils is one factor responsible for the small, uniform fibrillar diameter (25 nm) characteristic of this tissue, (c) the completely processed form of type V collagen found within tissues retains a large noncollagenous region, termed the NH2-terminal domain, at the amino end of its alpha 1 chain, and (d) the NH2-terminal domain may contain at least some of the information for the observed regulation of fibril diameters. In the present investigation we have employed polyclonal antibodies against the retained NH2-terminal domain of the alpha 1(V) chain for immunohistochemical studies of embryonic avian corneas and for immunoscreening a chicken cDNA library. When combined with cDNA sequencing and molecular rotary shadowing, these approaches provide information on the molecular structure of the retained NH2-terminal domain as well as how this domain might function in the regulation of fibrillar structure. In immunofluorescence and immunoelectron microscopy analyses, the antibodies against the NH2-terminal domain react with type V molecules present within mature heterotypic fibrils of the corneal stroma. Thus, epitopes within at least a portion of this domain are exposed on the fibril surface. This is in marked contrast to mAbs which we have previously characterized as being directed against epitopes located in the major triple helical domain of the type V molecule. The helical epitopes recognized by these antibodies are antigenically masked on type V molecules that have been assembled into fibrils. Sequencing of the isolated cDNA clones has provided the conceptual amino acid sequence of the entire amino end of the alpha 1(V) procollagen chain. The sequence shows the location of what appear to be potential propeptidase cleavage sites. One of these, if preferentially used during processing of the type V procollagen molecule, can provide an explanation for the retention of the NH2-terminal domain in the completely processed molecule. The sequencing data also suggest that the NH2-terminal domain consists of several regions, providing a structure which fits well with that of the completely processed type V molecule as visualized by rotary shadowing.

Amino Acid Sequence↗
PubMed1992

Identification of a previously unknown human collagen chain, alpha 1(XV), characterized by extensive interruptions in the triple-helical region.

A previously unknown collagen cDNA clone, PF19, was isolated from a human placenta library. The 2.1-kilobase insert has a complete open reading frame of 709 amino acids that includes 12 amino acids of the NH2-terminal domain, a principally collagenous region of 577 residues, and 120 residues of the noncollagenous COOH terminus. The collagenous part of the sequence encoded by PF19 is characterized by 13 interruptions ranging in size from 2 to 45 amino acids. Within four interruptions are consensus sequences for attachment of serine-linked glycosaminoglycans and asparagine-linked oligosaccharides suggesting that this collagen may be extensively glycosylated. A synthetic decapeptide representing a sequence at the beginning of the COOH-terminal noncollagenous domain was used to prepare an antibody in rabbits. This antiserum detected a 125-kDa bacterial collagenase-sensitive protein in Western blots of HeLa cell lysate. Consistent with the size of the collagen chain, Northern blot hybridization revealed a major transcript of 5.3 kilobases and two minor ones of 4.7 and 4.4 kilobases that are present in cultured human fibroblasts but absent from umbilical vein endothelial cells. We propose that the previously unidentified polypeptide described in this report be designated the alpha 1 chain of type XV collagen.

Amino Acid Sequence↗
PubMed1992

Synteny between the loci for a novel FACIT-like collagen locus (D6S228E) and alpha 1 (IX) collagen (COL9A1) on 6q12-q14 in humans.

A 1.8-kb cDNA encoding portion of a novel collagenous chain was isolated from a human rhabdomyosarcoma cell line by cross-hybridization using a chicken type V collagen probe. Sequence analysis suggests that this chain belongs to the recently discovered group of collagens, termed the FACIT class of macromolecules. This cDNA was used to locate the corresponding gene (D6S228E) to chromosome 6, notably at position 6q12-q14. Interestingly, within this region of human chromosome 6 residues the alpha 1 (IX) collagen gene (COL9A1), a member of the FACIT group.

Amino Acid Sequence↗
PubMed1992

Tissue-specific expression of type XIV collagen--a member of the FACIT class of collagens.

The collagens represent a highly diverse superfamily of extracellular matrix proteins that can be divided into several distinct families. One of the families, called FACIT (fibril-associated collagens with interrupted triple-helices) family, contains molecules that appear to be associated with cross-striated fibrils composed of members of the fibrillar collagen family. We have determined a portion of the primary structure of a recently discovered member of the FACIT family, chicken alpha 1(XIV) collagen, based on cloning and sequencing cDNAs. A synthetic oligopeptide from within the carboxy-terminal non-triple-helical domain of the alpha 1(XIV) chain has been used for generating specific polyclonal antibodies. The antiserum, PS1, recognizes a 220 kDa polypeptide in immunoblots of extracts of chicken skin, tendons, and cartilage. Sequencing of a tryptic peptide generated from purified, immunoreactive material, gives a sequence identical to that derived from cDNA sequencing, providing strong support for the type XIV-specificity of PS1. We have examined the expression of type XIV collagen in developing chick embryos by immunostaining of sections from 12-day-old embryos with PS1 and by Northern blot analysis of RNA from several tissues from both 12- and 17-day-old embryos. The results show that type XIV collagen is prevalent within relatively dense connective tissues such as dermis, tendons, perichondrium, perimysium, the stroma of lungs and liver, and blood vessels.

Amino Acid Sequence↗
PubMed1991

Cloning of a cDNA for a new member of the class of fibril-associated collagens with interrupted triple helices.

cDNA from embryonic chick skin has been isolated and characterized which encodes a novel member of the FACIT (fibril-associated collagen with interrupted triple helices) group whose other known members are collagen types IX and XII. Nucleotide sequence analysis of the cDNA, combined with characterization of a pepsin-resistant fragment of the protein from embryonic chick skin, demonstrates that the collagen chain is more closely related to the chain of type XII collagen than to those of type IX. It is most similar to a collagen, type XIV, recently identified in bovine skin. It is possible, therefore, that the cDNA codes for a chain of chicken type XIV collagen. From the additional data on molecular structure obtained by sequencing the cDNA, the FACIT family appears to consist of at least two classes of molecules: one of which contains the three chains of type IX collagen, and a second which includes the chains of collagen types XII and XIV.

Amino Acid Sequence↗
PubMed1991

cDNA analysis predicts a cornea-specific collagen.

In the development of chicken corneal stroma, two or more collagens often interact, either as constituents of a single heterotypic fibril or as components of the fibril surface. The latter, fibril-associated collagens, may facilitate interactions between fibrils and the surrounding extracellular matrix or between fibrils themselves. In an effort to isolate putative nonfibrillar collagens that may have such a function, we screened a 13-day embryonic cornea cDNA library under reduced stringency conditions, using a cDNA probe for a collagenous domain of type XII collagen. We isolated a 4.2-kilobase (kb) cDNA that predicts a "collagenous" protein that has three unusual, if not unique, features. (i) The putative polypeptide encoded by this cDNA has a structural arrangement in which numerous stretches of Gly-Xaa-Yaa triplets, typical of collagens, are interrupted by non-Gly-Xaa-Yaa regions. One of the potential triple-helical domains is 246 amino acids long, but most are much smaller, consisting of 15-36 amino acids. Many are very rich in the helix-stabilizing imino acid proline. (ii) Northern blot analyses demonstrated strong cDNA hybridization to a 6.8-kb mRNA whose expression is restricted to the cornea. No hybridization was observed to mRNAs from the nine other tissues used in these analyses, even with extended exposure of the film. (iii) The cDNA contains a short (less than or equal to 425-base-pair) sequence in the 3' untranslated region of the 6.8-kb mRNA that hybridizes to a 7.8-kb mRNA that has a wide tissue distribution.

Amino Acid Sequence↗
PubMed1991

Collagen types IX and X in the developing chick tibiotarsus: analyses of mRNAs and proteins.

To examine the regulation of collagen types IX and X during the hypertrophic phase of endochondral cartilage development, we have employed in situ hybridization and immunofluorescence histochemistry on selected stages of embryonic chick tibiotarsi. The data show that mRNA for type X collagen appears at or about the time that we detect the first appearance of the protein. This result is incompatible with translational regulation, which would require accumulation of the mRNA to occur at an appreciably earlier time. Data on later-stage embryos demonstrate that once hypertrophic chondrocytes initiate synthesis of type X collagen, they sustain high levels of its mRNA during the remainder of the hypertrophic program. This suggests that these cells maintain their integrity until close to the time that they are removed at the advancing marrow cavity. Type X collagen protein in the hypertrophic matrix also extends to the marrow cavity. Type IX collagen is found throughout the hypertrophic matrix, as well as throughout the younger cartilaginous matrices. But the mRNA for this molecule is largely or completely absent from the oldest hypertrophic cells. These data are consistent with a model that we have previously proposed in which newly synthesized type X collagen within the hypertrophic zone can become associated with type II/IX collagen fibrils synthesized and deposited earlier in development (Schmid and Linsenmayer, 1990; Chen et al. 1990).

Animals↗
PubMed1990

Extracellular matrices of the developing chick retina and cornea. Localization of mRNAs for collagen types II and IX by in situ hybridization.

In the embryonic avian eye, the vitreous and the primary corneal stroma are composed in part of collagen types II and IX. Previous biochemical and immunohistochemical studies have suggested that the production of these molecules changes dramatically during development. In the current investigation, we employed in situ hybridization to determine the temporospatial distribution of the messenger ribonucleic acids (mRNAs) for these collagens in the eyes of selected stages of chick embryos. Our observations suggest that through much of development, the ciliary region is the major source for the production of the collagens found within the vitreous. For the cornea, they confirm that both collagen mRNAs are indeed present, and suggest that each is independently regulated.

Animals↗
PubMed1989

Type XII collagen. A large multidomain molecule with partial homology to type IX collagen.

Three overlapping cDNAs encoding alpha 1 (XII) collagen have been isolated and sequenced. The DNAs define five sequence domains within the chain. Three domains are nontriple-helical; two are relatively short triple-helical regions. The amino acid sequences of tryptic peptides derived from 16- and 10-kDa pepsin-resistant fragments isolated from tendon extracts are in full agreement with the deduced sequences of the triple-helical regions. Two of the five sequence domains in alpha 1 (XII), one triple-helical and one nontriple-helical, show a high degree of similarity to regions in type IX collagen chains. In addition, examination of seven exons in the alpha 1 (XII) gene shows that the gene is, in part, similar to the structure of type IX collagen genes. Therefore, collagen types IX and XII are partially homologous. The alpha 1 (XII) sequence data predict an asymmetric structure for type XII collagen molecules, fully consistent with the rotary shadowing images. These images show a triple-helical 75-nm tail attached through a central globule to three finger-like structures, each 60 nm long (Dublet, B., Oh, S., Sugrue, S. P., Gordon, M. K., Gerecke, D. R., Olsen, B. R., and van der Rest, M. (1989) J. Biol. Chem. 264, 13150-13156).

Amino Acid Sequence↗
PubMed1989

The structure of avian type XII collagen. Alpha 1 (XII) chains contain 190-kDa non-triple helical amino-terminal domains and form homotrimeric molecules.

The monoclonal antibody 75d7, specific for type XII collagen (Sugrue, S.P., Gordon, M.K., Seyer, J., Dublet, B., van der Rest, M., and Olsen, B. R. (1989) J. Cell Biol., in press), was used to characterize the intact form of type XII collagen from chick embryo leg tendons. On an immunoblot of a 6% polyacrylamide gel of tendon extracts, one sharp band is recognized by the antibody at Mr = 220,000, while two fuzzy and poorly resolved bands are seen at Mr = 270,000 and Mr = 290,000. By immunoprecipitation of radiolabeled tendon culture media and electrophoresis of the precipitated material, bands with the same mobilities are observed, indicating that type XII collagen is not proteolytically processed in the extracellular space. Type XII collagen was extracted from tendons with 1 M NaCl in a Tris-HCl buffer and partially purified by concanavalin A-Sepharose and gel permeation chromatographies, using dot immunoblots to monitor the purification. Fractions highly enriched in bacterial collagenase-sensitive proteins with the same electrophoretic properties as type XII collagen were obtained. These fractions did not stain with Alcian blue and neither they nor the immunostained type XII collagen were affected by chondroitinase ABC digestion, indicating that type XII collagen is not a proteoglycan. A disulfide-bonded trimeric CNBr peptide was isolated by affinity chromatography on an antibody column and further purified by gel electrophoresis. Its NH2-terminal amino acid sequence was shown to be unique, demonstrating that type XII collagen is a homotrimer [alpha 1 (XII)]3. After bacterial collagenase digestion, both the immunopurified radiolabeled preparation and the purified tendon extract fraction showed by gel electrophoresis the presence of a large disulfide-bonded, 3 x 190-kDa, collagenase-resistant domain. Rotary shadowing and electron microscopy of the purified type XII fraction demonstrated that the molecule has the structure of a cross consisting of a 75 nm collagenase-sensitive tail, a central globule, and three 60 nm arms each ending in a small globule. After heat denaturation and renaturation, only a very large globule can be seen, attached to the triple helical tail. These results show that type XII collagen has a unique structure and is different from the other matrix constituents described so far.

Amino Acid Sequence↗
PubMed1989

Immunoidentification of type XII collagen in embryonic tissues.

We have generated a monoclonal antibody against a synthetic peptide whose sequence was derived from the nucleotide sequence of a cDNA encoding alpha 1(XII) collagen. The antibody, 75d7, has been used to identify the alpha 1(XII) chain on immunoblots of SDS-PAGE tendon extracts as a 220-kD polypeptide, under reducing conditions. Amino-terminal amino acid sequence analysis of an immunopurified cyanogen bromide fragment of type XII collagen from embryonic chick tendons gave a single sequence identical to that predicted from the cDNA, thus confirming that the antibody recognizes the type XII protein. Immunofluorescence studies with the antibody demonstrate that type XII collagen is localized in type I-containing dense connective tissue structures such as tendons, ligaments, perichondrium, and periosteum. With these data, taken together with previous results showing that a portion of the sequence domains of type XII collagen is similar to domains of type IX, a nonfibrillar collagen associated with cross-striated fibrils in cartilage, we suggest that types IX and XII collagens are members of a distinct class of extracellular matrix proteins found in association with quarter-staggered collagen fibrils.

Animals↗