Galloway-Mowat syndrome is an autosomal recessive disorder characterized by early onset
nephrotic syndrome and central nervous system anomalies. Mutations in podocyte
proteins, such as
nephrin,
alpha-actinin 4, and
podocin, are associated with
proteinuria and
nephrotic syndrome. The genetic defect in
Galloway-Mowat syndrome is as yet unknown. We postulated that in
Galloway-Mowat syndrome the mutation would be in a
protein that is expressed both in podocytes and neurons, such as synaptopodin, GLEPP1, or
nephrin. We therefore analyzed kidney tissue from normal children (n=3), children with congenital
nephrotic syndrome of the Finnish type (CNF, n=3),
minimal change disease (MCD, n=3),
focal segmental glomerulosclerosis (FSGS, n=3), and
Galloway-Mowat syndrome (n=4) by immunohistochemistry for expression of synaptopodin, GLEPP1, intracellular domain of
nephrin (
nephrin-I), and extracellular domain of
nephrin (
nephrin-E). Synaptopodin, GLEPP1, and
nephrin were strongly expressed in normal kidney tissue.
Nephrin was absent, and synaptopodin and GLEPP1 expression were decreased in CNF. The expression of all three
proteins was reduced in MCD and FSGS; the decrease in expression being more marked in FSGS. Synaptopodin, GLEPP1, and
nephrin expression was present, although reduced in
Galloway-Mowat syndrome. We conclude that the reduced expression of synaptopodin, GLEPP1, and
nephrin in
Galloway- Mowat syndrome is a secondary phenomenon related to the
proteinuria, and hence synaptopodin, GLEPP1, and
nephrin are probably not the
proteins mutated in
Galloway-Mowat syndrome.