ClinVar Genomic variation as it relates to human health

PTEN c.235G>A (p.A79T) meets criteria to be classified as likely benign for PTEN Hamartoma Tumor syndrome in an autosomal dominant manner using modified ACMG criteria (Mester et al. 2018; manuscript in preparation). Please see a summary of the rules and criteria codes in the 'PTEN ACMG Specifications Summary' document (assertion method column). BS1: Allele frequency of 0.0045 (0.45%, 9/1984 alleles) in the GME variome. (PMID 27428751) BS2_P: Meets criteria for BS2 (observed in the homozygous state in at least one healthy or PHTS-unaffected individual) but BS1 is also applied. (Internal laboratory contributor(s) SCV000222198.12) PP2: PTEN is defined by the PTEN Expert Panel as a gene that has a low rate of benign missense variation and where missense variants are a common mechanism of disease.

This variant is associated with the following publications: (PMID: 22703879, 26800850, 25980754, 25669429, 30728895, 12789288, 25527629, 10923032, 21659347, 21956414, 16171945, 23161105, 12372056, 21343951, 27720647, 27600092, 11297763, 24142049, 9619835, 21194675, 27477328, 28007035, 25925381, 22076652, 28873162, 29641532, 29371908, 29785012, 29706350, 31159747, 31209962, 31144778, 32350270, 32366478)

PTEN: PP2, PP3, BS1

This variant is considered likely benign. Homozygosity has been confirmed in one or more individuals. As homozygosity for pathogenic variants in this gene is generally assumed to result in embryonic lethality, this variant is unlikely to be pathogenic.

This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity.

Converted during submission to Uncertain significance.

This variant is classified as likely benign based on ACMG/AMP sequence variant interpretation guidelines (Richards et al. 2015 PMID: 25741868, with internal and published modifications).

CMT panel and gene duplication assays were negative and investigative exome sequencing was conducted. Clinical presentation is 80% match with Cowden Syndrome (exception unilateral pes cavus).

The PTEN p.Ala79Thr variant was identified in 10 of 47,988 proband chromosomes (frequency: 0.0002) from individuals or families with Bannayan-Riley Ruvalcaba syndrome, Cowden syndrome, PTEN hamartoma tumour syndrome, Lynch Syndrome, or ovarian or breast cancer and was present in 2 of 23,624 control chromosomes (frequency: 0.00008) from healthy individuals (Momozawa 2018, Figer 2002, Pilarski 2011, Tan 2011, Mester 2011, Dominguez-Valentin 2018, Nizialek 2015, Yurgelun 2015, Ngeow 2011). The variant was identified in dbSNP (rs202004587) as “with uncertain significance allele”, ClinVar (classified as likely benign by ClinGen PTEN Expert Panel in 2018, Ambry Genetics, GeneDx, and Color; as uncertain significance by Invitae, PreventionGenetics, Counsyl and 7 other submitters; and as pathogenic by Kuwait University) and LOVD 3.0 (observed 6x). The variant was identified in control databases in 29 of 281,404 chromosomes at a frequency of 0.0001 (Genome Aggregation Database Feb 27, 2017). The variant was observed in the following populations: European in 22 of 128,158 chromosomes (freq: 0.0002), South Asian in 5 of 30,560 chromosomes (freq: 0.0002), and Other in 1 of 7170 chromosomes (freq: 0.00004), while it was not observed in the African, Latino, Ashkenazi Jewish, East Asian or Finnish populations. However, this variant was also identified at an allele frequency of 0.005 in a Middle Eastern population, increasing the likelihood this could be a low frequency benign variant (Scott 2016). This variant has been identified in the homozygous state in one unaffected individual, decreasing the likelihood that this variant has clinical significance (PTEN expert panel internal data, per ClinVar entry dated April 6, 2018). The p.Ala79 residue is conserved in mammals but not in more distantly related organisms however four out of five computational analyses (PolyPhen-2, SIFT, AlignGVGD, BLOSUM, MutationTaster) do not suggest a high likelihood of impact to the protein; this information is not predictive enough to rule out pathogenicity. The variant occurs outside of the splicing consensus sequence and in silico or computational prediction software programs (SpliceSiteFinder, MaxEntScan, NNSPLICE, GeneSplicer) do not predict a difference in splicing. In summary, based on the above information, the clinical significance of this variant cannot be determined with certainty at this time although we would lean towards a more benign role for this variant. This variant is classified as likely benign.