Genetic disorders – Development
Kidney International (2000) 57, 1868–1872; doi:10.1046/j.1523-1755.2000.00036.x
WT1 splice-site mutations are rarely associated with primary steroid-resistant focal and segmental glomerulosclerosis
Erick Denamur, Nathalie Bocquet, Veronique Baudouin, Françis Da Silva, Reiner Veitia, Michel Peuchmaur, Jacques Elion, Marie Claire Gubler, Marc Fellous, Patrick Niaudet and Chantal Loirat
INSERM U458, Hôpital Robert Debré, and Laboratoire d'Anatomopathologic and EA 3102, Paris, France
Correspondence: Erick Denamur, M.D., Ph.D., INSERM U 458, Hôpital Robert Debré, 48, boulevard Sérurier, 75935 Paris cedex 19, France. E-mail: denamur@infobiogen.fr
Received 28 June 1999; Revised 23 November 1999; Accepted 18 December 1999.
Abstract
WT1 splice-site mutations are rarely associated with primary steroid-resistant focal and segmental glomerulosclerosis.
Background
Donor splice-site de novo heterozygous mutations in intron 9 of the Wilms' tumor gene (WT1) have been reported in Frasier syndrome, which is defined by the association of focal and segmental glomerulosclerosis (FSGS), male pseudohermaphroditism, and gonadoblastoma. These splice-site mutations alter the WT1 alternative splicing leading to two WT1 isoforms, with (+) or without (-) three amino acids, lysine-threonine-serine (KTS), between zinc fingers 3 and 4. The aim of this work was to investigate the possibility that some cases of primary steroid-resistant nephrotic syndrome associated with FSGS may be caused by WT1 splice-site mutations.
Methods
We analyzed WT1 exons 8 and 9 and the surrounding exon/intron boundary DNA sequences in 37 children with nonfamilial primary steroid-resistant nephrotic syndrome. Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to determine the relative ratio of +KTS/-KTS transcripts from immortalized lymphocyte RNA.
Results
One boy with FSGS and associated pathologies (diaphragmatic hernia, proximal hypospadias, and unilateral testicular ectopia) was found to carry the heterozygous 1228 +4 C
T splice-site mutation. RT-PCR quantitation of the +KTS/-KTS transcripts from immortalized lymphocyte RNA of this patient showed a diminution of the +KTS/-KTS isoform ratio (0.43), which is identical to that reported in patients with Frasier syndrome. Using the same approach, healthy control subjects have +KTS/-KTS ratios ranging from 1.50 to 2.00.
Conclusions
This study expands the range of the phenotypic presentation of the intron 9 splice-site WT1 mutations and adds to the already reported heterogeneity of primary steroid-resistant nephrotic syndromes. We suggest that these mutations are not likely to be a common cause of isolated steroid-resistant nephrotic syndrome, and recommend a WT1 exon 9/intron 9 splice-site study in children with primary steroid-resistant nephrotic syndrome if genital or diaphragmatic anomalies are associated. The identification of such WT1 mutations has practical implications for the management of these patients.
Keywords:
focal segmental glomerulosclerosis, splice-site mutations, nephrotic syndrome, Frasier syndrome, Wilms' tumor gene
