The mammalian Tolloid-like 1 gene, Tll1, is necessary for normal septation and positioning of the heart. (1/752)

Mammalian Tolloid-like 1 (mTLL-1) is an astacin-like metalloprotease, highly similar in domain structure to the morphogenetically important proteases bone morphogenetic protein-1 (BMP-1) and Drosophila Tolloid. To investigate possible roles for mTLL-1 in mammalian development, we have used gene targeting in ES cells to produce mice with a disrupted allele for the corresponding gene, Tll1. Homozygous mutants were embryonic lethal, with death at mid-gestation from cardiac failure and a unique constellation of developmental defects that were apparently confined solely to the heart. Constant features were incomplete formation of the muscular interventricular septum and an abnormal and novel positioning of the heart and aorta. Consistent with roles in cardiac development, Tll1 expression was specific to precardiac tissue and endocardium in 7.5 and 8.5 days p.c. embryos, respectively. Tll1 expression was also high in the developing interventricular septum, where expression of the BMP-1 gene, Bmp1, was not observed. Cardiac structures that were not affected in Tll1-/- embryos either showed no Tll1 expression (atrio-ventricular cushions) or showed overlapping expression of Tll1 and Bmp1 (aortico-pulmonary septum), suggesting that products of the Bmp1 gene may be capable of functionally substituting for mTLL-1 at sites in which they are co-expressed. Together, the various data show that mTLL-1 plays multiple roles in formation of the mammalian heart and is essential for formation of the interventricular septum.  (+info)

The role of tolloid/mini fin in dorsoventral pattern formation of the zebrafish embryo. (2/752)

A highly conserved TGF-&bgr; signaling pathway is involved in the establishment of the dorsoventral axis of the vertebrate embryo. Specifically, Bone Morphogenetic Proteins (Bmps) pattern ventral tissues of the embryo while inhibitors of Bmps, such as Chordin, Noggin and Follistatin, are implicated in dorsal mesodermal and neural development. We investigated the role of Tolloid, a metalloprotease that can cleave Chordin and increase Bmp activity, in patterning the dorsoventral axis of the zebrafish embryo. Injection of tolloid mRNA into six dorsalized mutants rescued only one of these mutants, mini fin. Through chromosomal mapping, linkage and cDNA sequence analysis of several mini fin alleles, we demonstrate that mini fin encodes the tolloid gene. Characterization of the mini fin mutant phenotype reveals that Mini fin/Tolloid activity is required for patterning ventral tissues of the tail: the ventral fin, and the ventroposterior somites and vasculature. Gene expression studies show that mfn mutants exhibit reduced expression of ventrally restricted markers at the end of gastrulation, suggesting that the loss of ventral tail tissues is caused by a dorsalization occurring at the end of gastrulation. Based on the mini fin mutant phenotype and the expression of tolloid, we propose that Mini fin/Tolloid modifes the Bmp activity gradient at the end of gastrulation, when the ventralmost marginal cells of the embryo are in close proximity to the dorsal Chordin-expressing cells. At this time, unimpeded Chordin may diffuse to the most ventral marginal regions and inhibit high Bmp activity levels. In the presence of Mini fin/Tolloid, however, Chordin activity would be negatively modulated through proteolytic cleavage, thereby increasing Bmp signaling activity. This extracellular mechanism is amplified by an autoregulatory loop for bmp gene expression.  (+info)

Expression of chick BMP-1/Tolloid during patterning of the neural tube and somites. (3/752)

The expression pattern described here is that of the chick BMP-1/Tolloid family of secreted metalloproteinases during early stages of development. BMP-1/Tolloid transcripts are expressed in the blastoderm, at gastrulation stages and as the neural plate forms and neural tube folds, BMP-1/Tolloid is found at the neural plate/ectodermal transition. Expression is maintained in the premigratory neural crest, and transiently in the migrating cephalic neural crest cells. BMP-1/Tolloid is also expressed in the caudal, but not in the anterior notochord, and in the ventral neural tube at the time of dorso-ventral patterning. Further sites of BMP-1/Tolloid expression are the lateral plate mesoderm and the dermotome and the myotome of the somites.  (+info)

Molecular cloning and characterization of a human metalloprotease disintegrin--a novel marker for dendritic cell differentiation. (4/752)

The 1alpha,25-dihydroxyvitamin D(3) (1,25- [OH](2)VD(3)) modulates the differentiation of monocytic cell lines and monocytes (MOs) in vitro. Up to now several target genes of 1,25(OH)(2)VD(3) have been described in monocytic cell lines; however, little is known about target genes in primary MOs. With the Differential Display technique, we found a transcript up-regulated by 1,25(OH)(2)VD(3) in short-term cultured human blood MOs, which we called MADDAM (metalloprotease and disintegrin dendritic antigen marker; EMBL/GenBank/DDBJ accession no. Y13786). Northern blot analysis confirmed this result and revealed a signal of MADDAM messenger RNA (mRNA) at about 7.5 kilobases (kb). Long-term culture (more than 20 hours) of MOs during macrophage (MAC) differentiation led to a rapid and complete down-regulation of MADDAM expression. In contrast, MADDAM expression was maintained in MOs differentiated along the dendritic cell (DC) pathway and induced in CD34(+)-derived DCs. In addition, in situ hybridization revealed signals of MADDAM mRNA in follicles of human lymph nodes and MADDAM mRNA was detected in freshly isolated human blood-DCs by reverse transcription-polymerase chain reaction (RT-PCR). By means of a database search, we found that MADDAM is a member of the ADAM (a metalloprotease and disintegrin) family, the human homologue to murine meltrin-beta (ADAM 19). From these data, we conclude that MADDAM is an important marker for the differentiation and characterization of DCs and the distinction between MACs and DCs. (Blood. 2000;96:732-739)  (+info)

Bone morphogenetic protein-1 processes probiglycan. (5/752)

Bone morphogenetic protein-1 (BMP-1) is a metalloprotease that plays important roles in regulating the deposition of fibrous extracellular matrix in vertebrates, including provision of the procollagen C-proteinase activity that processes the major fibrillar collagens I-III. Biglycan, a small leucine-rich proteoglycan, is a nonfibrillar extracellular matrix component with functions that include the positive regulation of bone formation. Biglycan is synthesized as a precursor with an NH(2)-terminal propeptide that is cleaved to yield the mature form found in vertebrate tissues. Here, we show that BMP-1 cleaves probiglycan at a single site, removing the propeptide and producing a biglycan molecule with an NH(2) terminus identical to that of the mature form found in tissues. BMP-1-related proteases mammalian Tolloid and mammalian Tolloid-like 1 (mTLL-1) are shown to have low but detectable levels of probiglycan-cleaving activity. Comparison shows that wild type mouse embryo fibroblasts (MEFs) produce only fully processed biglycan, whereas MEFs derived from embryos homozygous null for the Bmp1 gene, which encodes both BMP-1 and mammalian Tolloid, produce predominantly unprocessed probiglycan, and MEFs homozygous null for both the Bmp1 gene and the mTLL-1 gene Tll1 produce only unprocessed probiglycan. Thus, all detectable probiglycan-processing activity in MEFs is accounted for by the products of these two genes.  (+info)

Primary structure and autoproteolysis of brevilysin H6 from the venom of Gloydius halys brevicaudus. (6/752)

The complete amino acid sequence of brevilysin H6 (H6), a zinc-protease isolated from Gloydius halys brevicaudus venom, was determined by a manual Edman degradation method. H6 has an amino-terminal pyroglutamic acid and consists of a total of 419 residues. An N-linked sugar chain is attached at Asn-181. The molecule is composed of three domains (metalloprotease, disintegrin-like and cysteine-rich domains), as commonly found in other high molecular mass metalloproteases from snake venoms. In the absence of calcium ions, H6 is autocatalytically degraded with a half-life of 47 min to give 29 and 45 kDa fragments, which correspond to residues 208-419 and 99-419 of H6, respectively. Thus, the autoproteolysis seemed to start from the cleavage of either the Leu(98)-Leu(99) or Asp(207)-Ile(208) bond. Calcium ions suppressed both the formation of the 45 kDa fragment and the rate of autoproteolysis. Calcium ions also contributed to the stability of H6 against pH, heating, urea and cysteine. More than twenty-five peptide bonds adjacent to hydrophobic residues in the metalloprotease domain were progressively cleaved during the autoproteolysis.  (+info)

Notch1 signaling promotes the maturation of CD4 and CD8 SP thymocytes. (7/752)

Notch proteins regulate many developmental processes. Notch1 is highly expressed on thymocytes, but its role in regulating their development is not known. We show that activation of Notch1 signaling in CD4+CD8+ double positive thymocytes promotes the maturation of both CD4+ and CD8+ single positive thymocytes and that this occurs in the absence of interactions between the T cell receptor and MHC molecules expressed on thymic epithelial cells. We have also identified several genes that are transcriptionally regulated by Notch1 in T cells and show that they are upregulated during maturation into both single positive lineages. These observations suggest that Notch1 signaling plays a role in promoting maturation into both the CD4 and CD8 T cell lineages.  (+info)

Identification by differential display of a chicken tolloid-related metalloprotease specifically expressed in the caudal notochord. (8/752)

While the ventralizing factor Sonic hedgehog is expressed in the entire notochord (Development 121 (1995) 2537) the latter displays distinct ventralizing activities along its rostrocaudal axis. Hence, in HH stage-10 chicken embryo, the caudal notochord exhibits floor plate inducing capacities lost by rostral regions (Development 117 (1993) 205). Therefore, we hypothesize that the caudal notochord produces some cofactors which may contribute to its ventralizing properties. In order to identify such molecules we applied the differential display strategy and isolated a secreted Tolloid-related metalloprotease displaying a regionalized expression in the notochord.  (+info)