Characterization of the insulin-like growth factor binding protein family in Xenopus tropicalis

Abstract

The insulin-like growth factor binding protein (Igfbp) family consists of six members designated Igfbp1-6. Igfbps are involved in many vital biological functions. They physically interact with IGFs (IGF1 and IGF2) and act as carriers, thereby protecting IGFs from proteolytic degradation. Thus, they function as modulators of IGF activity. Furthermore, Igfbps have been reported to have IGF-independent activities. They interact with other proteins, including cell surface proteins, extracellular matrix proteins, and potentially intracellular molecules. In Xenopus tropicalis (X. tropicalis), only four igfbp genes (igfbp1, igfbp2, igfbp4, and igfbp5) have been identified, and their expression is not well characterized. We report that X. tropicalis genome lacks the igfbp3 and igfbp6 genes based on synteny analyses. We also examined the spatio-temporal expression patterns of igfbp genes in early X. tropicalis development. Expression analyses indicated that they are differentially expressed during early development. Each igfbp gene showed a characteristic spatial expression pattern. Except for igfbp5, they demonstrated overlapping expression in the pronephros. The Xenopus pronephros is composed of four domains (i.e., the proximal tubule, intermediate tubule, distal tubule, and connecting tubule). Our results showed that at least two igfbp genes are co-expressed in all pronephric domains, suggesting that redundant functions of igfbp genes are required in early pronephric kidney development.

A comprehensive reference transcriptome resource for the Iberian ribbed newt Pleurodeles waltl, an emerging model for developmental and regeneration biology

“…waltl has all six igfbp orthologous genes (Supplementary Fig. S2E), while Xenopus lacks igfbp3 and igfbp6 orthologs 65 …”

A comprehensive reference transcriptome resource for the Iberian ribbed newtPleurodeles waltl, an emerging model for developmental and regeneration biology

“…But we detected two additional paralogous genes encoding Wnt ligands, wnt11b and wnt7 - like (Supplementary figure 2A); we postulate that these additional loci were generated by duplication in the lineage leading to P. waltl . In vertebrates, six highly conserved igfbp -family genes are typically observed, and P. waltl has all six igfbp orthologous genes (Supplementary figure 2E), while Xenopus lacks igfbp3 and igfbp6 orthologs 65 .…”

Species-Specific Expression of Growth-Regulatory Genes in 2 Anoles with Divergent Patterns of Sexual Size Dimorphism

“…2010 ; Allard and Duan 2018 ). However, the function of IGFBPs varies greatly among non-mammalian vertebrates ( Haramoto et al. 2014 ; Garcia de la Serrana and Macqueen 2018 ), and predictions based upon molecular structure of IGFBP6 suggest that it can no longer efficiently bind IGFs in squamates ( McGaugh et al.…”