Developmental Expression and Biochemical Characterization of Emu Family Members

Abstract

Kidney development has often served as a model for epithelial-mesenchymal cell interaction where the branching epithelium of the ureteric bud induces the metanephrogenic mesenchyme to form epithelial nephrons. In a screen for genes differentially expressed during kidney development, we have identified a novel gene that is dynamically expressed in the branching ureter and the developing nephrons. It was designated Emu1 since it shares an N-terminal cysteine-rich domain with Emilin1/2 and Multimerin. This highly conserved EMI domain is also found in another novel protein (Emu2) of similar protein structure: an N-terminal signal peptide followed by the EMI domain, an interrupted collagen stretch, and a conserved C-terminal domain of unknown function. We identified two further secreted EMI domain proteins, prompting us to compare their gene and protein structures, the EMI domain phylogeny, as well as the embryonic expression pattern of known (Emilin1/2, Multimerin) and novel (Emu1/2, Emilin3, Multimerin2) Emu gene family members. Emu1 and Emu2 not only show a similar structural organization, but furthermore a striking complementary expression in organs developing through epithelial-mesenchymal interactions. In these tissues, Emu1 is restricted to epithelial and Emu2 to mesenchymal cells. Preliminary biochemical analysis of Emu1/2 confirmed that they are secreted glycoproteins which are attached to the extracellular matrix and capable of forming homo- and heteromers via disulfide bonding. The widespread, but individually distinct expression patterns of all Emu gene family members suggest multiple functions during mouse embryogenesis. Their multidomain protein structure may indicate that Emu proteins interact with several different extracellular matrix components and serve to connect and integrate the function of multiple partner molecules.

Characterization of C1q in Teleosts

“…6 and 7) demonstrate that the EMI-collagen-C1q domain-containing molecules are in an original position. Finally, the gene structures of these C1q domain-containing molecules revealed that EMI-collagen-C1q domain-containing molecules have multiple exons (35), whereas C1q-like and C1qDC molecules were encoded by only three or four exons (data not shown). These indicate that EMI-collagen-C1q domain-containing molecules may be the primitive form of C1q-like and C1qDC molecules.…”

Emilin3 is required for notochord sheath integrity and interacts with Scube2 to regulate notochord-derived Hedgehog signals

“…At variance with the other EMILIN/multimerin proteins, Emilin3 is not expressed in the cardiovascular system and it lacks the C-terminal gC1q domain, which is involved in cell attachment and integrin binding (Spessotto et al, 2003;Danussi et al, 2011). Emilin3 expression during mouse development is particularly abundant in the perichondrium of developing bones (Leimeister et al, 2002;Doi et al, 2004;Schiavinato et al, 2012). We have previously found that eight EMILIN/multimerin genes are present in the zebrafish genome in four pairs of duplicated paralogs (Milanetto et al, 2008).…”

EMILIN-1 Deficiency Induces Elastogenesis and Vascular Cell Defects

“…The family includes, in addition to the protein first isolated and now renamed EMILIN-1, a closely related molecule, EMILIN-2 (16); multimerin, a protein secreted by endothelial cells and platelets (19); and endoglyx-1, a panendothelial human cell surface glycoprotein (6). The latter two molecules, also known as EMILIN-3 and multimerin-2, respectively (15,24), share high homology to each other and have similar gene organizations.…”