73-Deoxychondropsin A
: A Novel Inhibitor of Bone Resorption Sourced From a Great Barrier Reef Sponge

Student thesis: Doctoral ThesisDoctor of Philosophy


73-deoxychondropsin A (73-DOC), a natural product of the polyketide family sourced from the marine sponge Ircinia ramosa, has previously shown inhibition of vacuolar-type H+-ATPases. This enzyme is crucial for osteoclastic bone resorption and is important in the pathogenesis of metabolic bone diseases, which affect both osteoclasts and the bone-forming osteoblasts. Following extraction of 73-DOC from I. ramosa tissues, in vitro experiments were performed to establish the differential effects of 73-DOC on primary osteoclast and osteoblast differentiation and function. Dose-response and time course analyses, as well as confocal microscopy assessments of cellular acidification, showed that 73-DOC inhibited mouse and human osteoclast resorption at concentrations 5-10-fold lower than those causing inhibition of osteoblast activity. The inhibition of bone resorption whilst maintaining bone formation demonstrates a novel application for 73-DOC and potential as a therapeutic for osteolytic diseases such as osteoporosis.
Symbiotic microorganisms have frequently been proposed as the true producers of sponge-sourced secondary metabolites. Whilst symbionts are typically resistant to culturing, metagenomic approaches allow for microbial biosynthetic genes from the sponge holobiome to be cloned and ultimately expressed in a heterologous host, leading to a sustainable supply of the compound. To clone and sequence the biosynthetic gene cluster responsible for 73-DOC, a metagenomic fosmid library was screened for conserved features of polyketide synthase biosynthesis. Metagenomic DNA was also directly sequenced and screened using in silico analysis tools, which led to the annotation of genes with putative partial involvement in 73-DOC biosynthesis. Further work required to identify the remaining biosynthetic components was suggested.
Date of Award2018
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorPaul Long (Supervisor) & Agamemnon Grigoriadis (Supervisor)

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