Proteomic analysis of sea urchin (Strongylocentrotus purpuratus) spicule matrix.

Karlheinz Mann,Fred H Wilt,Albert J Poustka

doi:10.1186/1477-5956-8-33

Abstract

BackgroundThe sea urchin embryo has been an important model organism in developmental biology for more than a century. This is due to its relatively simple construction, translucent appearance, and the possibility to follow the fate of individual cells as development to the pluteus larva proceeds. Because the larvae contain tiny calcitic skeletal elements, the spicules, they are also important model organisms for biomineralization research. Similar to other biominerals the spicule contains an organic matrix, which is thought to play an important role in its formation. However, only few spicule matrix proteins were identified previously.ResultsUsing mass spectrometry-based methods we have identified 231 proteins in the matrix of the S. purpuratus spicule matrix. Approximately two thirds of the identified proteins are either known or predicted to be extracellular proteins or transmembrane proteins with large ectodomains. The ectodomains may have been solubilized by partial proteolysis and subsequently integrated into the growing spicule. The most abundant protein of the spicule matrix is SM50. SM50-related proteins, SM30-related proteins, MSP130 and related proteins, matrix metalloproteases and carbonic anhydrase are among the most abundant components.ConclusionsThe spicule matrix is a relatively complex mixture of proteins not only containing matrix-specific proteins with a function in matrix assembly or mineralization, but also: 1) proteins possibly important for the formation of the continuous membrane delineating the mineralization space; 2) proteins for secretory processes delivering proteinaceous or non-proteinaceous precursors; 3) or proteins reflecting signaling events at the cell/matrix interface. Comparison of the proteomes of different skeletal matrices allows prediction of proteins of general importance for mineralization in sea urchins, such as SM50, SM30-E, SM29 or MSP130. The comparisons also help point out putative tissue-specific proteins, such as tooth phosphodontin or specific spicule matrix metalloproteases of the MMP18/19 group. Furthermore, the direct sequence analysis of peptides by MS/MS validates many predicted genes and confirms the existence of the corresponding proteins.

Highlights

The sea urchin embryo has been an important model organism in developmental biology for more than a century
Computational methods, semi-quantative RT-PCR analysis and in situ hybridization studies implicated many more proteins in biomineralization events. This included previously un-described C-type lectin-like domain-containing proteins, at least six members of the extracellular and membrane-anchored mesenchyme specific MSP130 family, and one of 19 putative carbonic anhydrases encoded in the S. purpuratus genome [16]
Spicules prepared by the method used, which involves treatment with SDS and sodium hypochlorite, appear free of adherent extracellular material when viewed by electron microscopy [6,14] (Figure 1)

Summary

Introduction

The sea urchin embryo has been an important model organism in developmental biology for more than a century This is due to its relatively simple construction, translucent appearance, and the possibility to follow the fate of individual cells as development to the pluteus larva proceeds. This is due to the relatively simple construction of a translucent larva from about 1500 cells and the possibility to follow the fate of individual cells as development to the pluteus larva proceeds. Computational methods, semi-quantative RT-PCR analysis and in situ hybridization studies implicated many more proteins in biomineralization events This included previously un-described C-type lectin-like domain-containing proteins, at least six members of the extracellular and membrane-anchored mesenchyme specific MSP130 family, and one of 19 putative carbonic anhydrases encoded in the S. purpuratus genome [16]. Only SM50 and two members of the SM30 subfamily were identified by Western blotting of the 2 D displays [24]

Methods

Results

Conclusion