This sequence change affects a donor splice site in intron 8 of the PTEN gene. While this variant is not anticipated to result in nonsense mediated decay, it likely alters RNA splicing and results in a disrupted protein product. This variant is not present in population databases (gnomAD no frequency). Disruption of this splice site has been observed in individuals with Cowden or Cowden-like syndrome and overgrowth and intellectual disability (PMID: 21194675, 28475857, 28677221). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 635377). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic.

This variant is considered likely pathogenic. This variant occurs within a consensus splice junction and is predicted to result in abnormal mRNA splicing of either an out-of-frame exon or an in-frame exon necessary for protein stability and/or normal function.

Canonical splice site variant predicted to result in an in-frame loss of the adjacent exon in a gene for which loss of function is a known mechanism of disease; Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 31664961, 28677221, 18626510, 21194675, 39049995, 28475857)

The c.1026+1G>T intronic pathogenic mutation results from a G to T substitution one nucleotide after coding exon 8 of the PTEN gene. This variant was reported in individual(s) with features consistent with PTEN hamartoma tumor syndrome; in at least one individual, it was determined to be de novo (Tatton-Brown K et al. Am J Hum Genet, 2017 May;100:725-736; Matsubayashi H et al. BMC Cancer, 2019 Oct;19:1014). Another variant impacting the same donor site (c.1026+1G>A) has been identified in individual(s) with features consistent with PTEN hamartoma tumor syndrome (Agrawal S et al. Hum Mol Genet. 2005 Aug;14(16):2459-68; Tan MH et al. Am. J. Hum. Genet. 2011 Jan; 88(1):42-56; Chen HJ et al. Hum Mutat, 2017 10;38:1372-1377; Ambry internal data). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This nucleotide position is highly conserved in available vertebrate species. In silico splice site analysis predicts that this alteration will weaken the native splice donor site. Alterations that disrupt the canonical splice site are expected to cause aberrant splicing, resulting in an abnormal protein or a transcript that is subject to nonsense-mediated mRNA decay. Based on the supporting evidence, this variant is interpreted as a disease-causing mutation.