Matrix Metalloproteinases are required for membrane motility and lumenogenesis during Drosophila heart development

Abstract

Matrix Metalloproteinases (Mmps) degrade glycoproteins and proteoglycans of the extracellular matrix (ECM) or cell surface and are crucial for morphogenesis. Mmps and their inhibitors are expressed during early stages of cardiac development in vertebrates and expression is altered in multiple congenital cardiomyopathies such as cardia bifida. Drosophila genome encodes two copies of Mmps, Mmp1 and Mmp2 whereas in humans up to 25 Mmps have been identified with overlapping functions. We investigated the role of Mmps during embryonic heart development in Drosophila, a process which is morphogenetically similar to early heart tube formation in vertebrates. We demonstrate that the two Mmps in Drosophila have distinct and overlapping roles in cell motility, cell adhesion and cardiac lumenogenesis. We determined that Mmp1 and Mmp2 promote Leading Edge membrane dynamics of cardioblasts during collective migration. Mmp2 is essential for cardiac lumen formation, and mutants generate a cardia bifida phenotype. Mmp1 is required for luminal expansion. Mmp1 and Mmp2 both localise to the basal domains of cardiac cells, however, occupy non-overlapping domains apically. Mmp1 and Mmp2 regulate the proteoglycan composition and size of the apical and basal ECM, yet only Mmp2 is required to restrict ECM assembly to the lumen. Mmp1 negatively regulates the size of the adhesive Cadherin cell surface domain, whereas in a complementary fashion, Mmp2 negatively regulates the size of the Integrin-ECM domain and thereby prescribes the domain to establish and restrict Slit morphogen signalling. Inhibition of Mmp activity through ectopic expression of Tissue Inhibitor of Metalloproteinase in the ectoderm blocks lumen formation. Therefore, Mmp expression and function identifies ECM differentiation and remodelling as a key element for cell polarisation and organogenesis.

Transcriptomic analysis of the testicular fusion in Spodoptera litura

“…Cell adhesion to the ECM is mediated via integrin receptors that regulates the bidirectional signaling, which is important for cell survival, proliferation, differentiation, migration and adhesion [21,28,55]. Integrins are involved in cell adhesion and fusion during the sperm-egg fusion [16][17][18][19][20], myoblast fusion [17,21], cell-cell fusion in the heart development [19], stable adhesion between epithelia in wing development of insects [54] and cell migration in the nervous system development in mammals [56], In this study, the ECM components and its receptors integrins were also up-regulated at L6D6 (Fig. 7, 10), suggesting that the ECM-integrin interaction pathway may be involved in the fusion of testes by signaling cell migration and adhesion in S. litura.…”

“…Fusion of cell or tissues an indispensable process in diverse physiological events. Fusion events of tissue or organ are reported in the different developmental process in different organisms such as sperm-egg adhesion and fusion in mammals [16], myoblast fusion in flies and mice [17], epithelial fusion during neural tube morphogenesis [18] and medial cardiac cell fusion during the heart morphogenesis in Drosophila [19]. Fusion is essential for the fertilization, muscle development, neural tube formation and heart formation.…”

“…MMPs promote the collective CB cell migration, ECM remodeling and lumen formation. Integrin and cadherin are also involved in cell adhesion and fusion [19]. These studies indicate that ECM remodeling is very important in the spermegg fusion, myoblast fusion and heart development of Drosophila, and the MMPs are the main enzymes in ECM remodeling [19,23].…”

“…Integrin and cadherin are also involved in cell adhesion and fusion [19]. These studies indicate that ECM remodeling is very important in the spermegg fusion, myoblast fusion and heart development of Drosophila, and the MMPs are the main enzymes in ECM remodeling [19,23]. Although, the mechanisms of the fusion of different cells or tissues are reported in different species, the mechanism for the testis fusion in insects is still unknown.…”

Transcriptomic analysis of the testicular fusion in Spodoptera litura

“…Fusion of cell or tissues is an indispensable process in diverse physiological events. Fusion events of tissue or organ are reported in the different developmental process in different organisms such as sperm-egg adhesion and fusion in mammals [16], myoblast fusion in flies and mice [17], epithelial fusion during neural tube morphogenesis [18] and medial cardiac cell fusion during the heart morphogenesis in Drosophila [19]. Fusion is essential for the fertilization, muscle development, neural tube formation and heart formation.…”