Abstracts Category : Other

Developing novel transgenic reporters to study Lowesyndrome in Zebrafish

by Anthony Jackson

Lowe syndrome is a rare X linked disorder,characterized by renal, ocular and cerebral defects, caused bymutation in the protein OCRL1. OCRL1 has been implicated in aplethora of cellular functions, and loss of its catalyticconversion of PtdIns(4,5)P2 into PtdIns(4)P is proposed to underlymany of the cellular phenotypes associated with lack of OCRL1. Theinteraction with other proteins such as IPIP27A are also requiredfor the correct function of OCRL1. Renal tubular dysfunctionsimilar to that seen in Lowe syndrome patients is seen in zebrafishmodels of ocrl1 and ipip27a mutation. Using zebrafish as a model ofLowe syndrome, a reduction of increased PtdIns(4,5)P2 levels inocrl1-/- embryos is shown to alleviate the renal tubulardysfunction. This demonstrates that targeting PtdIns(4,5)P2 is aviable option for therapeutic treatment of Lowe syndrome. Noveltransgenic zebrafish lines are also described, that provide megalinspecific, fluorescent and luminescent readouts of proximal tubularendocytic function. These will be an important tool to perform highthroughput screens for compounds that alleviate the symptoms ofLowe syndrome. The importance of the binding of IPIP27A to itsinteraction partners OCRL1 and SH3 containing proteins such asPACSIN2 is demonstrated by rescue of the ipip27a-/- mutant withipip27a with mutated binding sites. The phenotype of ipip27a-/-mutant embryos is further characterised to demonstrate there is nolong term growth defect or defect in tubular polarity, howevertubular dilation is seen, suggesting possible mild ciliary defects.In the zebrafish proximal tubule in fish with no functional IPIP27Aor OCRL1, a more severe defect in 10 kDa dextran endocytosis isseen, as well as hydrocephaly and curved body axis, ciliaimpairment related phenotypes. This indicates that IPIP27A andOCRL1 are acting in the same pathway, and therefore depletion ofboth exacerbates phenotypes. Finally, transgenic lines expressingubiquitous or pronephric tubule specific fluorescently tagged Rabproteins as markers of membrane compartments in zebrafish aredescribed.Advisors/Committee Members: HURLSTONE, ADAM AFL, Lowe, Martin, Hurlstone, Adam.