CDH1 Germline Variants in a Tunisian Cohort with Hereditary Diffuse Gastric Carcinoma

Abstract

Mutational screening of the CDH1 gene is a standard treatment for patients who fulfill Hereditary Diffuse Gastric Cancer (HDGC) testing criteria. In this framework, the classification of variants found in this gene is a crucial step for the clinical management of patients at high risk for HDGC. The aim of our study was to identify CDH1 as well as CTNNA1 mutational profiles predisposing to HDGC in Tunisia. Thirty-four cases were included for this purpose. We performed Sanger sequencing for the entire coding region of both genes and MLPA (Multiplex Ligation Probe Amplification) assays to investigate large rearrangements of the CDH1 gene. As a result, three cases, all with the HDGC inclusion criteria (8.82% of the entire cohort), carried pathogenic and likely pathogenic variants of the CDH1 gene. These variants involve a novel splicing alteration, a missense c.2281G > A detected by Sanger sequencing, and a large rearrangement detected by MLPA. No pathogenic CTNNA1 variants were found. The large rearrangement is clearly pathogenic, implicating a large deletion of two exons. The novel splicing variant creates a cryptic site. The missense variant is a VUS (Variant with Uncertain Significance). With ACMG (American College of Medical Genetics and Genomics) classification and the evidence available, we thus suggest a revision of its status to likely pathogenic. Further functional studies or cosegregation analysis should be performed to confirm its pathogenicity. In addition, molecular exploration will be needed to understand the etiology of the other CDH1- and CTNNA1-negative cases fulfilling the HDGC inclusion criteria.

A Rare MSH2 Variant as a Candidate Marker for Lynch Syndrome II Screening in Tunisia: A Case of Diffuse Gastric Carcinoma

“…Results were processed by the Coffalyser.Net software (MRC-Holland, Amsterdam, Holland). Our results showed no large rearrangements in the CDH1 gene among this index case, as it is described in our previous study [ 33 ].…”

“…As a result, we have found no deleterious or potentially deleterious variants in the coding and flanking regions of both CDH1 and CTNNA1 genes as it was mentioned in our previous study [ 33 ]. This finding suggests other candidate genes/variants predisposing to DGC.…”

“…Based on the International Gastric Cancer Linkage Consortium (IGCLC), this case meets the third criterion for CDH1 germline screening. As a result, we found no pathogenic variant in the CDH1 gene coding and exons flanking regions [ 33 ]. In addition, no large rearrangements have been identified by MLPA in this gene for this patient [ 33 ].…”

“…As a result, we found no pathogenic variant in the CDH1 gene coding and exons flanking regions [ 33 ]. In addition, no large rearrangements have been identified by MLPA in this gene for this patient [ 33 ]. This result is not surprising since the lack of CDH1 pathogenic variant DGC patients meeting the IGCLC testing criteria has already been reported.…”

“…Referring to 2015 IGCLC [ 30 ] for the search of CDH1 and CTNNA1 [ 31 ] germline mutations, a complete sequencing of these two genes was carried out. Primers were designed using Primer Express™ Software version 2.0 Applied Biosystems Thermo Fisher Scientific [ 32 ] as shown in Table S1 , used in our previous study [ 33 ]. Forward and reverse primers incorporated the extensions 18F tail (ACCGTTAGTTAGCGATTT) and 18R tail (CGGATAGCAAGCTCGT), respectively, at their 5′ ends.…”