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Congenital vertebral malformations (CVM) occur in 1 in 1000 live births and in many cases can cause spinal deformities, such as scoliosis, and result in disability and distress of affected individuals. Many severe forms of the disease, such as spondylocostal dystostosis, are recessive monogenic traits affecting somitogenesis, however the etiologies of the majority of CVM cases remain undetermined. Here we demonstrate that morphological defects of the notochord in zebrafish can generate congenital-type spine defects. We characterize three recessive zebrafish leviathan/col8a1a mutant alleles ((m531, vu41, vu105)) that disrupt collagen type VIII alpha1a (col8a1a), and cause folding of the embryonic notochord and consequently adult vertebral column malformations. Furthermore, we provide evidence that a transient loss of col8a1a function or inhibition of Lysyl oxidases with drugs during embryogenesis was sufficient to generate vertebral fusions and scoliosis in the adult spine. Using periodic imaging of individual zebrafish, we correlate focal notochord defects of the embryo with vertebral malformations (VM) in the adult. Finally, we show that bends and kinks in the notochord can lead to aberrant apposition of osteoblasts normally confined to well-segmented areas of the developing vertebral bodies. Our results afford a novel mechanism for the formation of VM, independent of defects of somitogenesis, resulting from aberrant bone deposition at regions of misshapen notochord tissue.
Copyright © 2013 Elsevier Inc. All rights reserved.
Collagens contain large numbers of Gly-Xaa-Yaa peptide repeats that form the characteristic triple helix, where the individual chains fold into a polyproline II helix and three of these helices form a right-handed triple helix. For the proper folding of the triple helix collagens contain trimerization domains. These domains ensure a single starting point for triple helix formation and are also responsible for the chain selection in heterotrimeric collagens. Trimerization domains are non-collagenous domains of very different structures. The size of trimerization domains varies from 35 residues in type IX collagen to around 250 residues for the fibrillar collagens. These domains are not only crucial for biological functions, but they are also attractive tools for generating recombinant collagen fragments of interest as well as for general use in protein engineering and biomaterial design. Here we review the current knowledge of the structure and function of these trimerization domains.
Copyright © 2011 Elsevier Ltd. All rights reserved.
BACKGROUND AND AIMS - The distinction between benign and malignant gastrointestinal stromal tumours (GISTs) is often unclear at the clinical and histopathology levels. GISTs are believed to arise from the stem cells of Cajal. In order to define genetic biomarkers and identify target genes related to GIST progression, we analysed and compared benign and malignant GISTs with verified follow up data using cDNA expression arrays.
METHODS - Eight genes were frequently overexpressed in malignant GISTs and their overexpression was confirmed using quantitative real time reverse transcription-polymerase chain reaction. These genes included ezrin (villin 2 (VIL2)), collagen 8 alpha 1 subunit (COL8A1), G2/mitotic specific cyclin B1 (CCNB1), high mobility group protein (HMG2), TSG101 tumour susceptibility protein, CENP-F kinetochore protein, protein tyrosine kinase 2 (FAK), and protein kinase DYRK2. To test these genes in a clinical setting, we obtained diagnostic samples of 16 additional GISTs that were classified at diagnosis as benign, malignant, and uncertain malignant potential (UMP).
RESULTS - There was remarkable gene overexpression in all malignant GISTs. Statistical analyses revealed significant correlations between overexpression of several gene pairs in malignant GISTs. We found the strongest correlations (rho>0.70) among the significant correlations (p<0.01) between CCNB1-CENP-F (rho = 0.87) and CCNB1-FAK (rho = 0.73). Gene expression of the UMP GISTs suggested two different groups. Three UMP GISTs had gene expression consistent with malignant tumours and their follow up data revealed that indeed these patients had recurrences later on. On the other hand, UMP GISTs that had low gene expression levels continued free of disease for several years.
CONCLUSIONS - These results provide insight into the oncogenesis of GISTs and suggest that testing the expression profile of a number of genes may segregate GISTs into groups of different tumour behaviour.