Table 1.
Clinical, genetic information and functional variant evaluation of the investigated Turkish and Tunisian patients.
Fig 1.
Pedigrees of variant carriers.
Arrows show index cases. Double lines indicate consangious marriages. Tumours and other diseases are indicated under the symbols (CRC: colorectal cancer; Stom.: stomach cancer; Blad.: bladder cancer; Lung, Larynx: cancers affecting lung and larynx; CUP: cancer of unknown primary; EC: endometrium cancer; Uterus: uterus cancer; Alzh.: Alzheimer’s disease). Age at diagnosis is indicated where available. Filled symbols indicate tumours elevated in Lynch syndrome.
Table 2.
Classification criteria as applied to the current variants1.
Fig 2.
Analysis of expression of the MLH1 variants.
A, Expression of wild-type and variant MLH1 proteins was visualized by SDS-PAGE and western blotting. The two stability reference variants p.(Ala681Thr) (pathogenic expression defect) and p.(Val716Met) (non-pathogenic expression defect, polymorphism) were transfected in parallel. The shown blots are representative for 3 independent experiments that were performed and delivered the data shown in evaluation (B). B, Average expression values in percent of the wild-type expression and standard deviations are shown for wild-type and variant MLH1 proteins.
Fig 3.
Analysis of mismatch repair activity of the MLH1 variants.
DNA mismatch repair activity was assessed for wild-type and variant MLH1 proteins, and a negative control (without MLH1 protein) was included as detailed in “Materials and Methods”. A, Representative agarose gel image of the MMR activity measurement. The extent of repair is visible in the agarose gel electrophoresis by the generation of two smaller fragments (“Repair”) of the unrepaired, linearized plasmid (“No repair”). B, three independent experiments were performed, and repair activity was scored relative to wild-type MLH1 protein (100%). Average repair values and standard deviations are shown.
Fig 4.
Affected residues in their structural and conservational context.
Structural model of the human MLH1-PMS2 heterodimer (MLH1: green; PMS2: cyan). The N-terminal, structured ATPase regions (bound ATP in ball-stick presentation with magnesium ions as orange spheres) are connected by unstructured linker region (symbolized as a line), including the catalytically relevant, conserved ConMot motif, to the structured C-terminal dimerization and endonuclease domains. The locations of the residues affected by alterations investigated in this study are marked in red in the structure and by red boxes in the sequence logos. Sequence conservation is shown in WebLogo presentation at the left. Yellow shading indicates hydrophobic residues relevant for helix anchoring. Green boxes above the sequence inform about secondary structure that these sequences form.