ClinVar

Description

The heterozygous c.2694-2_2694-1del variant in NPHP3 was identified by our study in one individual with renal-hepatic-pancreatic dysplasia 1. Trio exome analysis showed this variant to be in trans with a likely pathogenic variant (ClinVar Variation ID: 635041). The c.2694-2_2694-1del variant in NPHP3 has been previously reported in 22 unrelated individuals with NPHP3-related disease (PMID: 33532864, PMID: 28973083, PMID: 32055034, PMID: 32552793, PMID: 32901917, PMID: 27894351, PMID: 33726816, PMID: 23559409, PMID: 26673778, PMID: 30002499, PMID: 33323469), but has been identified in 0.04% (14/30612) of South Asian chromosomes by the Genome Aggregation Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP ID: rs963574014). Although this variant has been seen in the general population in a heterozygous state, its frequency is not high enough to rule out a pathogenic role. Of these 22 previously reported unrelated individuals (PMID: 33532864, PMID: 28973083, PMID: 32055034, PMID: 32552793, PMID: 32901917, PMID: 27894351, PMID: 33726816, PMID: 23559409, PMID: 26673778, PMID: 30002499, PMID: 33323469), 12 were homozygotes (PMID: 32055034, PMID: 32552793, PMID: 27894351, PMID: 18371931, PMID: 20007846) and 4 were compound heterozygotes who carried pathogenic or likely pathogenic variants in trans (PMID: 33532864, ClinVar Variation ID: 659899; PMID: 28973083, ClinVar Variation ID: 988261; PMID: 23559409, ClinVar Variation ID: 96511, ClinVar Variation ID: 693989 ; PMID: 30002499, ClinVar Variation ID: 262696; PMID: 33323469, ClinVar Variation ID: 1454640), which increases the likelihood that the c.2694-2_2694-1del variant is pathogenic. This variant has also been reported in ClinVar (Variation ID: 220868) and has been interpreted as pathogenic by multiple submitters. RT-PCR analysis performed on affected tissue shows evidence of altered splicing of exon 20 (PMID: 32552793, PMID: 30002499, PMID: 20007846). A different nucleotide change that also results in a splice acceptor variant at the same site, c.2694-2A>T (ClinVar Variation ID: 1524627), has been previously reported likely pathogenic, and the variant being assessed here, c.2694-2_2694-1del, is predicted by SpliceAI to have a similar effect on splicing. This variant is located in the 3' splice region. Computational tools do suggest an impact to splicing. However, this information is not predictive enough to determine pathogenicity. There is an in-frame cryptic splice site 21 bases from the intron-exon boundary, providing evidence that this variant may delete 7 amino acids instead of causing loss of function. However, this information is not predictive enough to determine pathogenicity. Loss of function of the NPHP3 gene is an established disease mechanism in autosomal recessive renal-hepatic-pancreatic dysplasia 1. In summary, this variant meets criteria to be classified as pathogenic for autosomal recessive renal-hepatic-pancreatic dysplasia 1. ACMG/AMP Criteria applied: PVS1_Moderate, PS1_Supporting, PS3_Moderate, PM3_VeryStrong (Richards 2015).