Delaney Carolan, “Role of MMP28 in Early Placodal Development Using Xenopus”
Mentor: Nadege Gouignard, Biological Sciences
Poster #48

Matrix metalloproteinases (MMPs) are mostly known for their extracellular matrix remodeling activity and their function in wound healing, cell proliferation and migration. They are involved in pathological and physiological events including cancer, tissues homeostasis and embryogenesis. However, our understanding of their molecular function remains incomplete. Cranial placodes (CP) are embryonic cells that will give rise to most of the head pair sensory organs (inner ear, lens, olfactory system), and the facial nerves. Defects in CP development program are responsible for numerous diseases such as Branchio-oto-renal syndrome, anosmia, and deafness. In Xenopus laevis, MMP28 is expressed in the pre placodal region, a domain that emerges in the anterior dorsal ectoderm at neurula stage. At tailbud stage, MMP28 expression is maintained in the epibranchial placodes that gives rise to facial nerves. Previous experiments in the lab have shown that placodal MMP28 controls the development of the neighboring cranial neural crest. However, the role of MMP28 during the CP development itself was not investigated. Here we focus on understanding MMP28 function during CP development using Xenopus laevis as a model system. We performed loss of function experiments using morpholino oligonucleotides to transiently knockdown MMP28 expression. Embryos were then collected at neurula and tailbud stages and whole mount In situ hybridization was performed. We used a set of CP markers to evaluate the effect of MMP28 knockdown on the development of the placodes. Our results showed that the plan placodal marker (Six1) and the epibranchial marker (Pax8) were downregulated at neurula stage. The olfactory marker (Dmrta1) showed downregulation at both neurula stage and tailbud stage. And finally, the otic placode marker Sox9 was also strongly affected by the lack of MMP28 at tailbud stage. Taken together our data showed that MMP28 plays a key role in placodal development and potentially their derivatives.