WT1 Splice-Site Mutations Are Rarely Associated With Primary Steroid-Resistant Focal and Segmental Glomerulosclerosis

Kidney Int. 2000 May;57(5):1868-72. doi: 10.1046/j.1523-1755.2000.00036.x.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adrenal Cortex Hormones / therapeutic use*
  • Child
  • Child, Preschool
  • DNA-Binding Proteins / genetics*
  • Exons
  • Female
  • Glomerulosclerosis, Focal Segmental / drug therapy
  • Glomerulosclerosis, Focal Segmental / genetics*
  • Humans
  • Infant
  • Male
  • Mutation*
  • RNA Splicing
  • Transcription Factors / genetics*
  • WT1 Proteins

Substances

  • Adrenal Cortex Hormones
  • DNA-Binding Proteins
  • Transcription Factors
  • WT1 Proteins