Exploring the expression and potential roles of Fras1 and Frem2 in models of kidney diseases affecting the collecting
Lead Research Organisation:
University College London
Department Name: UNLISTED
Abstract
In this project I propose to undertake studies of the possible roles of Fraser genes in diseases of a particular part of the kidney: the collecting duct. Fraser genes are known to have an essential role in the development of the kidney as evidenced by Fraser syndrome in which the kidneys are severely malformed or absent when the latter genes are mutated. These genes are known to have continued activity in the mature kidney and may be involved in diseases affecting the kidney collecting duct system including obstructive nephropathy and polycystic kidney disease. Obstructive nephropathy accounts for 20% of children with kidney failure and polycystic kidney disease accounts for 10% of adults on dialysis. Most such individuals with renal failure are destined to die prematurely. Furthermore, the treatment of such diseases constitutes a major burden for the families involved and for national health services. My aim is to study the role of Fraser genes in the biology underlying such diseases so that treatments can de devised in future to modify the disease processes responsible before the onset of renal failure. This is, therefore, potentially of great importance in alleviation of human suffering.
Technical Summary
Aims and objectives
FRAS1 and FREM2 are mutated in Fraser syndrome (FS), and mouse experiments show that Fras1 and Frem2 control early metanephrogenesis, explaining renal agenesis in the human syndrome. Continued activities of these genes maintain epithelial integrity in mature kidneys, especially in collecting ducts. I hypothesise that Fras1 and Frem2 have roles in the pathobiology of diseases which affect collecting ducts after early steps of development are complete. Collecting ducts bear the brunt of injury following urinary flow impairment; furthermore, collecting duct cysts occur in polycystic kidney diseases (PKDs).
My specific aims are to:
1. Define Fras1 and Frem2 expression in mice with obstructive nephropathy
2. Define Fras1 and Frem2 expression in mice with PKD
3. Ascertain whether Fras1 and/or Frem2 haploinsufficiency affects severity of obstructive nephropathy and PKD.
Design and Methodology
I will analyse four mouse models of collecting duct disease:
a. Surgically induced unilateral ureteric obstruction (UUO); b. A genetic model of congenital pelviureteric junction obstruction; c. cpk/cpk autosomal recessive PKD; d. A novel Pkd1 mutant PKD model. I will use: quantitative real-time polymerase chain reaction to measure Fras1 and Frem2 mRNA; in situ hybridisation to localise transcripts; and immunohistochemistry to localise FS proteins. Results will be correlated with renal injury by quantifying: tubular atrophy and interstitial fibrosis; phospho-Smads (Bmp/Tgf beta signalling markers); apoptosis with in-situ end labelling; and proliferation after administering BrdU. Finally, I will use blebbed and Frem2/LacZ genetrap mice to generate animals with one mutant allele (i.e. +/Fras1 or +/Frem2) and heterozygous for both mutant alleles. I will determine whether renal injury after surgically induced UUO is modified by FS mutations, using the read-outs described above. I will introduce the same spectrum of mutant FS alleles into cpk/cpk mice to determine whether the FS genotypes affect PKD severity by comparing kidney/bodyweight ratio; area occupied by cysts; proliferation and apoptosis between the different FS genotypes.
Scientific and medical opportunities of the study
My studies are essential preludes to experiments where FS genes will be experimentally ablated postnatally in vivo to define possible roles in acquired renal disease and will complement in vitro studies determining whether FS genes modulate renal epithelial differentiation and cyst growth. Putting the proposed work in a broader context, obstructive nephropathy accounts for 20% of children with end-stage renal failure and PKD accounts for 10% of adults with chronic renal failure. Understanding the biology underlying such diseases is potentially of great importance in alleviation of human suffering.
FRAS1 and FREM2 are mutated in Fraser syndrome (FS), and mouse experiments show that Fras1 and Frem2 control early metanephrogenesis, explaining renal agenesis in the human syndrome. Continued activities of these genes maintain epithelial integrity in mature kidneys, especially in collecting ducts. I hypothesise that Fras1 and Frem2 have roles in the pathobiology of diseases which affect collecting ducts after early steps of development are complete. Collecting ducts bear the brunt of injury following urinary flow impairment; furthermore, collecting duct cysts occur in polycystic kidney diseases (PKDs).
My specific aims are to:
1. Define Fras1 and Frem2 expression in mice with obstructive nephropathy
2. Define Fras1 and Frem2 expression in mice with PKD
3. Ascertain whether Fras1 and/or Frem2 haploinsufficiency affects severity of obstructive nephropathy and PKD.
Design and Methodology
I will analyse four mouse models of collecting duct disease:
a. Surgically induced unilateral ureteric obstruction (UUO); b. A genetic model of congenital pelviureteric junction obstruction; c. cpk/cpk autosomal recessive PKD; d. A novel Pkd1 mutant PKD model. I will use: quantitative real-time polymerase chain reaction to measure Fras1 and Frem2 mRNA; in situ hybridisation to localise transcripts; and immunohistochemistry to localise FS proteins. Results will be correlated with renal injury by quantifying: tubular atrophy and interstitial fibrosis; phospho-Smads (Bmp/Tgf beta signalling markers); apoptosis with in-situ end labelling; and proliferation after administering BrdU. Finally, I will use blebbed and Frem2/LacZ genetrap mice to generate animals with one mutant allele (i.e. +/Fras1 or +/Frem2) and heterozygous for both mutant alleles. I will determine whether renal injury after surgically induced UUO is modified by FS mutations, using the read-outs described above. I will introduce the same spectrum of mutant FS alleles into cpk/cpk mice to determine whether the FS genotypes affect PKD severity by comparing kidney/bodyweight ratio; area occupied by cysts; proliferation and apoptosis between the different FS genotypes.
Scientific and medical opportunities of the study
My studies are essential preludes to experiments where FS genes will be experimentally ablated postnatally in vivo to define possible roles in acquired renal disease and will complement in vitro studies determining whether FS genes modulate renal epithelial differentiation and cyst growth. Putting the proposed work in a broader context, obstructive nephropathy accounts for 20% of children with end-stage renal failure and PKD accounts for 10% of adults with chronic renal failure. Understanding the biology underlying such diseases is potentially of great importance in alleviation of human suffering.
