The Molecular Basis of Hereditary Diseases 
of the Kidney 
Stephen T. Reeders, M.D. — Associate Investigator 
Dr. Reeders is also Associate Professor of Internal Medicine and Genetics at Yale University School of 
Medicine. He attended Cambridge University with the intention of majoring in physics, but, realizing that 
developments in molecular biology were providing the basis for new approaches to the study of human 
disease, he switched to medicine and continued to study at Oxford University. After qualifying in 
medicine, he sought clinical training in intensive care, cardiology, nephrology, and neurology. Then, with 
Sir David Weatherall at Oxford, he began to use molecular genetic techniques to study human disease, 
with emphasis on hereditary diseases of the kidney, diseases that heretofore had received little attention 
from geneticists. 
CRITICAL for normal functioning of the kid- 
ney is the integrity of the glomerular base- 
ment membrane (GBM) , a complex extracellular 
structure that forms one of the main barriers be- 
tween the blood and the urine. The GBM is com- 
posed of several proteins, including five related 
but subtly different collagens that interact to 
form a chicken-wire mesh holding the membrane 
together. One of the interests of our laboratory is 
Goodpasture syndrome, an autoimmune disorder 
in which, for unknown reasons, autoantibodies 
are suddenly targeted at the collagen components 
of basement membrane in the lungs and kidneys. 
In the kidney, these autoantibodies produce a 
sudden and devastating severe inflammation, 
which frequently leads to acute renal failure, irre- 
versible unless treated. The nephritis is often ac- 
companied by autoimmune lung damage, mani- 
fested by bleeding into the alveoli. 
Previous studies have shown that the probable 
target of Goodpasture autoantibodies is the a 3 
chain of basement membrane collagen. To under- 
stand the pathogenesis more clearly, we under- 
took to isolate and purify the collagen chain to 
study its structure. Because the protein is present 
in very small amounts and is accompanied by four 
similar proteins, purifying it has proved difficult. 
We have therefore isolated, cloned, and se- 
quenced the gene for the a3 chain of basement 
membrane collagen and have used the sequence 
information to predict the primary structure and 
compare this protein with other basement mem- 
brane collagens. 
In collaboration with Billy Hudson (Kansas 
City), we used knowledge of the primary struc- 
ture to identify several potential antibody- 
binding sites (epitopes) in the a3 molecule. We 
synthesized short peptides and used them to test 
the binding of some of these sites, which we local- 
ized to within a small region at the carboxyl ter- 
minus. At least one of the peptides has very high 
affinity for Goodpasture antibodies and adsorbs 
them from patients' serum. Knowledge of the 
epitope structure should enable us to develop a 
means of selectively adsorbing Goodpasture anti- 
bodies, opening possibilities for a new treatment 
modality. In addition, this information may pro- 
vide clues to the development of autoimmunity 
in this disorder. 
Mariko Mariyama, a Howard Hughes associate 
in our laboratory, has recently isolated a novel 
basement membrane collagen, a4. The compari- 
son of the structure of this molecule with the 
known basement membrane collagen allows the 
evolution of these molecules to be inferred. Two 
classes of the molecule exist in all species from 
roundworm to humans, suggesting a functional 
divergence. The expression of a3 and a4 occurs 
in a limited number of tissues, and they are re- 
gionally localized within these tissues. In kidney, 
for example, they are found in the glomerulus 
but not in the tubular or vascular endothelial 
basement membranes. Our gene mapping data 
suggest that the expression of a3 and aA is coordi- 
nated by transcription of the genes from opposite 
DNA strands. A similar arrangement has been 
found for the al and a2 genes, homologues of al 
and a2. 
One of the major projects in our laboratory is a 
study of the molecular and cellular pathology of 
autosomal dominant polycystic kidney disease 
(ADPKD) , one of the commonest causes of kid- 
ney failure in humans, affecting at least 1 in 
1,000 of the population. The disease is an enor- 
mous burden to families and the community, 
since the majority of patients develop irreversible 
kidney failure in middle life and require dialysis 
or transplantation for survival. 
Having previously ascertained that the majority 
of the inherited mutations in ADPKD lie close to 
the tip of the short arm of chromosome 16, we 
have isolated and cloned a small segment of DNA 
(550,000 base pairs) that includes the mutated 
gene. This region turns out to be extremely gene 
rich, and we have already isolated 22 genes from 
within it. These include novel cyclin A-like and 
r«s-like genes, a gene encoding a zinc finger pro- 
tein, and a gene having homology to the (8- 
335 
