21A. DIS3L2-mediated Wilms tumor predisposition and the role of non-coding RNAs

Genetic or epigenetic factors underly Wilms tumor (WT) in up to 33% of cases. Next to classical WT predisposition syndromes like Beckwith-Wiedemann spectrum and WT1-associated predisposition syndrome, many other WT predisposition genes have been identified. One of these genes is DIS3L2, which encodes a 3’-5’ exonuclease involved in degradation of a subset of non-coding mRNAs, including the pre-miRNA pre-let-7. Biallelic germline DIS3L2 variants cause Perlman overgrowth syndrome, which is associated with a very high WT susceptibility. Heterozygous germline variants, mostly exon 9 deletions, occur in up to 4% of WT cases, which usually acquire a second somatic hit to trigger WT development. Whereas potential roles of DIS3L2 in mRNA degradation have been studied in general, the mechanism of WT predisposition in a DIS3L2-deficient context is still poorly understood. Furthermore, parallels in WT development may exist with other WT subtypes that are driven by key players of miRNA processing, including DICER1, DROSHA, and DCGR8.

To elucidate the role of DIS3L2 in WT development we have four objectives:

1. Establish the mutational status of DIS3L2 in normal tissue and tumor in a cohort of ~175 WT patients at the genomic (point mutations and structural variations) and transcriptomic (alternative splicing, monoallelic expression) level.
2. Compare the molecular and clinical features that are shared by DIS3L2-deficient WTs
3. Identify the (noncoding) RNA targets of DIS3L2 by transcriptome analysis and analysis of 3’uridylated transcripts in DIS3L2-deficient WTs and CRISPR-mediated normal kidney and WT-derived organoids
4. Compare the identified commonly altered downstream events in DIS3L2-deficient WTs with WT subtypes carrying germline or somatic aberrations in DICER1, DROSHA or DCGR8 to identify common driving pathways of WT development between these subtypes.

With this work we aim to improve our understanding of WT development in a DIS3L2-deficient context, thereby providing novel clues for optimized care in these patients.