TY - JOUR
T1 - Reclassification of Two MLH1 Variants of Uncertain Significance Utilizing Clinical and Functional Data
AU - Frederiksen, Jane Hübertz
AU - Birkedal, Ulf
AU - Bachmann, Sarah
AU - Eliesen, Elisabeth Victoria
AU - Rasmussen, Lene Juel
AU - Pedersen, Katja Venborg
AU - Al-Zehhawi, Lana
AU - Boonen, Susanne E
AU - Krogh, Lotte
AU - Rønlund, Karina
AU - Graversen, Lise
AU - Assenholt, Jannie
AU - Schmiegelow, Kjeld
AU - Wadt, Karin
AU - Gerdes, Anne-Marie
AU - Hansen, Thomas V O
N1 - © 2024 The Author(s). Molecular Genetics & Genomic Medicine published by Wiley Periodicals LLC.
PY - 2024/11
Y1 - 2024/11
N2 - BACKGROUND: Pathogenic variants in the mismatch repair genes are associated with an elevated lifetime risk of colorectal cancer (CRC). We previously identified two variants of uncertain significance (VUS) in the MLH1 gene, c.696_698del, p.(Cys233del) and c.1919C > G, p.(Pro640Arg), in Danish families with numerous occurrences of CRC.METHODS: To reclassify the variants we collected clinical data, initiated tumor and co-segregation analysis, and performed RNA splicing analysis, subcellular localization, and protein stability studies.RESULTS: The functional analysis revealed that the c.696_698del, p.(Cys233del) variant had an effect at the RNA level, on subcellular localization, and on protein stability, while the c.1919C > G, p.(Pro640Arg) variant showed decreased expression in localization studies and decreased protein stability. These results suggest both variants disrupt DNA mismatch repair.CONCLUSION: By applying all collected data and functional results we propose to reclassify the c.696_698del, p.(Cys233del) and the c.1919C > G, p.(Pro640Arg) variants as likely pathogenic (class 4) using MMR gene-specific ACMG/AMP guidelines. Consequently, the two MLH1 variants can now be used for risk assessment of variant carriers, while family members without the variants can be excluded from intensified cancer surveillance and follow population recommendations.
AB - BACKGROUND: Pathogenic variants in the mismatch repair genes are associated with an elevated lifetime risk of colorectal cancer (CRC). We previously identified two variants of uncertain significance (VUS) in the MLH1 gene, c.696_698del, p.(Cys233del) and c.1919C > G, p.(Pro640Arg), in Danish families with numerous occurrences of CRC.METHODS: To reclassify the variants we collected clinical data, initiated tumor and co-segregation analysis, and performed RNA splicing analysis, subcellular localization, and protein stability studies.RESULTS: The functional analysis revealed that the c.696_698del, p.(Cys233del) variant had an effect at the RNA level, on subcellular localization, and on protein stability, while the c.1919C > G, p.(Pro640Arg) variant showed decreased expression in localization studies and decreased protein stability. These results suggest both variants disrupt DNA mismatch repair.CONCLUSION: By applying all collected data and functional results we propose to reclassify the c.696_698del, p.(Cys233del) and the c.1919C > G, p.(Pro640Arg) variants as likely pathogenic (class 4) using MMR gene-specific ACMG/AMP guidelines. Consequently, the two MLH1 variants can now be used for risk assessment of variant carriers, while family members without the variants can be excluded from intensified cancer surveillance and follow population recommendations.
KW - Humans
KW - MutL Protein Homolog 1/genetics
KW - DNA Mismatch Repair
KW - Female
KW - Male
KW - Protein Stability
KW - Middle Aged
KW - Colorectal Neoplasms/genetics
KW - RNA Splicing
KW - Colorectal Neoplasms, Hereditary Nonpolyposis/genetics
KW - Mutation
UR - http://www.scopus.com/inward/record.url?scp=85209701524&partnerID=8YFLogxK
U2 - 10.1002/mgg3.70026
DO - 10.1002/mgg3.70026
M3 - Journal article
C2 - 39548353
SN - 2324-9269
VL - 12
JO - Molecular Genetics & Genomic Medicine
JF - Molecular Genetics & Genomic Medicine
IS - 11
M1 - e70026
ER -