Abstract: SA-PO222

Dlg1 Is a Novel Regulator of Slit Diaphragm Formation in the Drosophila Nephrocyte

Session Information

  • Glomerular: Cell Biology
    November 04, 2017 | Location: Hall H, Morial Convention Center
    Abstract Time: 10:00 AM - 10:00 AM

Category: Glomerular

  • 1003 Glomerular: Cell Biology

Author

  • Poulton, John S., University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Background

Proper glomerular filtration requires the formation and maintenance of slit diaphragms (SDs) between podocyte foot processes. Mutations affecting SD formation/function result in nephrotic syndrome. SD formation is coupled to podocyte maturation, which involves changes in cell polarity. Previous work in mammals has revealed that apical polarity proteins play important roles in SD formation, however the basolateral polarity complex appears dispensable.

Methods

To further explore the role of polarity proteins in SD formation, I took advantage of the Drosophila nephrocyte, which form SDs analogous to vertebrate podocytes. The facile genetics of Drosophila allowed efficient screening of multiple RNAi lines targeting components of the basolateral polarity complex.

Results

Consistent with previous findings in mouse podocytes, I found no obvious role for the basolateral protein Scrib in SD formation. In addition, knockdown of Lgl, another key component of the basolateral complex also produced no defects in SD formation. Surprisingly, loss of Discs Large1 (Dlg1) led to dramatic mislocalization of core SD components, including the fly homologues of Nephrin, Neph1, and ZO-1. Transmission electron microscopy of Dlg1 knockdown nephrocytes revealed significant reduction in the number of SDs, though some small patches of nephrocyte surface did retain SDs. Intriguingly, numerous ectopic SDs were observed internal to the cell surface, lining the labyrinthine channels—a phenotype not observed in wildtype nephrocytes.

Conclusion

These data identify Dlg1 as a novel and vital regulator of SD formation and localization. Dlg1 is a highly conserved PDZ protein best known for its role as a scaffold in the basolateral polarity complex, where it helps define apicobasal polarity in polarized epithelia. However, our findings indicate that Dlg’s function in SD formation is independent of its role in cell polarity. I am currently working to determine Dlg’s mechanism of action in this new context and also test Dlg’s potential role in SD formation in vertebrate podocytes.