Gonadal Function in 15 Patients Associated with WT1 Gene Mutations

Exonic WT1 pathogenic variants in 46,XY DSD associated with gonadoblastoma

OBJECTIVE

The literature regarding gonadoblastoma risk in exonic Wilms' tumor suppressor gene (WT1) pathogenic variants is sparse. The aim of this study is to describe the phenotypic and genotypic characteristics of Asian-Indian patients with WT1 pathogenic variants and systematically review the literature on association of exonic WT1 pathogenic variants and gonadoblastoma.

DESIGN

Combined retrospective-prospective analysis.

METHODS

In this study, 46,XY DSD patients with WT1 pathogenic variants detected by clinical exome sequencing from a cohort of 150 index patients and their affected relatives were included. The PubMed database was searched for the literature on gonadoblastoma with exonic WT1 pathogenic variants.

RESULTS

The prevalence of WT1 pathogenic variants among 46,XY DSD index patients was 2.7% (4/150). All the four patients had atypical genitalia and cryptorchidism. None of them had Wilms' tumor till the last follow-up, whereas one patient had late-onset nephropathy. 11p13 deletion was present in one patient with aniridia. The family with p.Arg458Gln pathogenic variant had varied phenotypic spectrum of Frasier syndrome; two siblings had gonadoblastoma, one of them had growing teratoma syndrome (first to report with WT1). On literature review, of >100 exonic point pathogenic variants, only eight variants (p.Arg462Trp, p.Tyr177*, p.Arg434His, p.Met410Arg, p.Gln142*, p.Glu437Lys, p.Arg458*, and p.Arg458Gln) in WT1 were associated with gonadoblastoma in a total of 15 cases (including our two cases).

CONCLUSIONS

WT1 alterations account for 3% of 46,XY DSD patients in our cohort. 46,XY DSD patients harboring exonic WT1 pathogenic variants carry a small but definitive risk of gonadoblastoma; hence, these patients require a gonadoblastoma surveillance with a more stringent surveillance in those harboring a gonadoblastoma-associated variant.

Systematic Review of Genotype-Phenotype Correlations in Frasier Syndrome

Introduction

Frasier syndrome (FS) is a rare inherited kidney disease caused by intron 9 splicing variants of WT1. For wild-type WT1, 2 active splice donor sites in intron 9 cause a mixture of 2 essential transcripts (with or without lysine-threonine-serine [+/KTS or −KTS]), and imbalance of the +KTS/−KTS ratio results in the development of FS. To date, 6 causative intron 9 variants have been identified; however, detailed transcript analysis has not yet been conducted and the genotype-phenotype correlation also remains to be elucidated.

Methods

We conducted an in vitro minigene splicing assay for 6 reported causative variants and in vivo RNA sequencing to determine the +KTS/−KTS ratio using patients’ samples. We also performed a systematic review of reported FS cases with a description of the renal phenotype.

Results

The in vitro assay revealed that although all mutant alleles produced −KTS transcripts only, the wild-type allele produced both +KTS and −KTS transcripts at a 1:1 ratio. In vivo RNA sequencing showed that patients’ samples with all heterozygous variants produced similar ratios of +KTS to −KTS (1:3.2−1:3.5) and wild-type kidney showed almost a 1:1 ratio (1:0.85). A systematic review of 126 cases clarified that the median age of developing ESKD was 16 years in all FS patients, and there were no statistically significant differences between the genotypes or sex chromosome karyotypes in terms of the renal survival period.

Conclusion

Our study suggested no differences in splicing pattern or renal survival period among reported intron 9 variants causative of FS.