XB-ART-22865J Cell Biol February 1, 1993; 120 (4): 1059-67.
Identification and characterization of thrombospondin-4, a new member of the thrombospondin gene family.
A new member of the thrombospondin gene family, designated thrombospondin-4, has been identified in the Xenopus laevis genome. The predicted amino acid sequence indicates that the protein is similar to the other members of this gene family in the structure of the type 3 repeats and the COOH-terminal domain. Thrombospondin-4 contains four type 2 repeats and lacks the type 1 repeats that are found in thrombospondin-1 and 2. The amino-terminal domain of thrombospondin-4 has no significant homology with the other members of the thrombospondin gene family or with other proteins in the database. RNAse protection analysis establishes that the initial expression of Xenopus thrombospondin-4 is observed during neurulation. Levels of mRNA expression increase twofold during tailbud stages but decrease by the feeding tadpole stage. The size of the thrombospondin-4 message is 3.3 Kb and 3.4 Kb in the frog and human, respectively. Northern blot analysis of human tissues reveals high levels of thrombospondin-4 expression in heart and skeletal muscle, low levels in brain, lung and pancreas and undetectable levels in the placenta, liver and kidney. These data establish the existence of a new member of the thrombospondin gene family that may participate in the genesis and function of cardiac and skeletal muscle.
PubMed ID: 8432726
PMC ID: PMC2200072
Article link: J Cell Biol
Species referenced: Xenopus laevis
Genes referenced: thbs4
Article Images: [+] show captions
|Figure 1. Alignment of Xenopus thrombospondin-4 clones. Restriction endonuclease sites are indicated for the two families (TSP-4A and TSP-4B). The clones that have been isolated in the first (XF1- XF4), second (XSS-XS10), and third (XTI1-XTI4) rounds of screening have been grouped into their appropriate family by restriction endonuclease mapping and nucleotide sequencing.|
|lqgure 2. Northern blot of Xenopus stage 17 RNA. Two micrograms of total stage 17 mRNA was electrophoresed and blotted. The blot was probed with the XF3 clone. The positions and sizes of the markers are indicated on the letL|
|Figure 3. The nucleotide sequence and corresponding amino acid sequence of Xenopus thrombospondin-4. The predicted site for signal sequence cleavage is indicated (open triangle). The termination codon TAA and the polyadanylation signal AATAAA are underlined. The sites for potential N-linked glyeosylation are circled and the site for potential ~-hydroxylation is boxed. Note that asparagine(314) could be either glycosylated or ~-l~xlmxylated. These sequence data are available from EMBL/GenBank/DDBJ under accession number, Z19091.|
|Figure 4. The amino acid sequence of the type 2 (A) and 3 (B) repeats of thrombospondin-4. The amino acid sequences for the four type 2 repeats P(217)-K(394) and seven type 3 repeats (D-I) have been aligued. The positions of gaps ~ marked by dashes. The consensus sequence for the type 3 repeats of Xenop~ thmmbospondin-4 is compared to that for human and mouse thrombospondin-1 and chicken thrombospondin-2 at the bottom of the figure. The underline indicates that an N occupies one of the positions that is occupied by a D.|
|Figure 5. Developmental expression of thrombospondin-4 mRNAs during Xenopus development as determined by RNase protection analyses. Ten embryo equivalents total mRNA per lane were bybridized with a 3~P-labeled thrombospondin-4 antisense transcript synthesized in vitro. EFI-,~ mRNA analysis is included as a control for RNA loading. The relative stage-specific levels of EFI-,v shown here are equivalent to those described by Krieg et al. (1989). Embryos were staged according to Nieuwkoop and Faber (1967). Stage 8 corresponds to the mid-blastula, which is marked by the onset of zygotic transcription in Xenopus (Newport and Kirschner, 1982). (P), probe alone, unhybridized transcript, no RNAse; (t) tRNA control lane, no protected fragments after RNAse digestion. Stages include: (1) fertilized egg, (8) mid-blastula, 00-12) early-late gastrula, 07) neurula, (25-35) tailbud stages, (45) feeding tadpole. Thrombospondin-4 protected fragment is ,,o300 nucleotides. EFI-a protected fragment is ,x,75 nucleotides. Full length EFI-c~ probe (90 nucleotides) is not shown.|
|Figure 6. The expression of thrombospondin-4 in adult human tissue. A northern blot ofpoly A + RNA from adult human heart (a), brain (b), placenta (c), lung (d), liver (e), skeletal muscle (f), kidney (g), and pancreas (h). The blot was probed with a 2.2-kb fragment of Xenopus thrombospondin-4. The positions and sizes (kb) of the markers are indicated on the left.|
|Figure 7. Schematic model of thrombospondin-4. The molecular architecture of thrombospondin-4 is shown below that of thrombospondin-1 or 2. The NH2 terminal is to the left and the COOH terminal is to the right. Whereas the NH2-terminal domains are similar in size, they share very little sequence homology. Two interchain disulfides of thrombospondin-1 and 2 are depicted as vertical lines between the NH~-terminal domain and the region of homology with procollagen. Whereas two cysteine residues are present in a similar location in thrombospondin-4, the structure of the protein that contains the thrombospondin-4 polypeptide remains to be determined.|
References [+] :
Asch, Thrombospondin sequence motif (CSVTCG) is responsible for CD36 binding. 1992, Pubmed