Abstract
Specialized renal epithelial cells known as podocytes are essential components of the filtering structures within the kidney that coordinate the process of removing waste from the bloodstream. Podocyte loss initiates many human kidney diseases as it triggers subsequent damage to the kidney, leading to progressive loss of function that culminates with end stage renal failure. Podocyte morphology, function and gene expression profiles are well conserved between zebrafish and humans, making the former a relevant model to study podocyte development and model kidney diseases. Recently, we reported that whole genome sequencing of the zeppelin (zep) zebrafish mutant, which exhibits podocyte abrogation, revealed that the causative lesion for this defect was a splicing mutation in the breast cancer 2, early onset (brca2) gene. This was a surprising and novel discovery, as previous research on brca2/BRCA2 in a number of vertebrate animal models had not implicated an explicit role for this gene in kidney mesoderm development. Interestingly, the abrogation of the podocyte lineage in zep mutants was also accompanied by the formation of a larger interrenal (IR) gland, which is analogous to the adrenal gland in mammals, and suggested a fate switch between the renal and inter renal mesodermal derivatives. Mirroring these findings, knockdown of brca2 also recapitulated the loss of podocytes and increased IR population. In addition, brca2 overexpression was sufficient to partially rescue podocytes in zep mutants, and induced ectopic podocyte formation in wild-type embryos. Interestingly, immunofluorescence studies indicated that zep mutants had elevated P-h2A.X levels, suggesting that DNA repair is dysfunctional in these animals and contributes to the zep phenotype. Moving forward, this unique zebrafish mutant provides a new model to further explore how brca2 contributes to the development of tissues including the kidney mesoderm-roles which may have implications for renal diseases as well.
Highlights
The classic tumor suppressor genes BRCA1, DNA repair associated and BRCA2, DNA repair associated (BRCA1 and BRCA2) have risen to notoriety as they are two of the most frequently mutated genes found in hereditary breast cancer tumors[1, 2]
In exploring related tissue types, we noticed a significant increase in area and volume of the interrenal gland (IR) in zep mutants, the teleost equivalent of the adrenal cortex, which is marked by the transcripts of nuclear receptor subfamily 5, group A, member 1a at 36 hpf (Figure 1D)
We examined the gain of function brca2 phenotype, to test whether Brca2 was sufficient to ameliorate the podocyte deficiency in zep mutants[66]. zep mutants injected with brca2 capped mRNA exhibited a partial podocyte rescue, where 55% of mutant embryos developed wt1b+ podocytes (Figure 2D)
Summary
The classic tumor suppressor genes BRCA1, DNA repair associated and BRCA2, DNA repair associated (BRCA1 and BRCA2) have risen to notoriety as they are two of the most frequently mutated genes found in hereditary breast cancer tumors[1, 2]. The zebrafish pronephros has been a useful model for the in vivo study of podocyte and renal corpuscle development, real-time physiology assessment of filtration, and how acute damage to the various components leads to regeneration or permanent defects[55].
Sign-in/Register to view highlights & summary 
Accepted Version (
Free)
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call