A De Novo Mutation in ACTC1 and a TTN Variant Linked to a Severe Sporadic Infant Dilated Cardiomyopathy Case

Figures

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  Figure 1. Electrocardiographic findings in the infant DCM patient. Twelve lead electrocardiogram shows sinus tachycardia of 159 bpm, increased precordial lead voltages, and an incomplete bundle brunch left ventricle (BBLV) and inverted T waves in V3–V6.

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  Figure 2. Thoracic roentgenography of the DCM patient. Chest roentgenography demonstrates marked cardiomegaly, pulmonary venous congestion, and pulmonary edema.

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  Figure 3. Doppler echocardiography reveals a severe DCM in the proband. Four chambers' view of the echocardiography allows to appreciate the left auricle and the left ventricle severely enlarged and the thinned interventricular septum bulging into the right ventricle.

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  Figure 4. Analysis of confirmed variants in the infant DCM case support their probable pathogenic implication. (a) DNA chromatograms contrast of mutated and native ACTC1 show a heterozygous A > G transition at nucleotide 664, which is traduced into an Ala > Thr substitute ion at 222nd residue in actin protein. (b) DNA chromatograms show a heterozygous 33,250 mutated site of TTN from A to G, which is traduced into a Glu > Lys substitution at 11,084 residue in titin protein. (c) Amino acidic alignment of orthologous actin proteins shows that alanine at Position 222 is highly conserved among several species. (d) Amino acidic alignment of orthologous titin proteins shows that glutamic acid at Position 11,084 is well conserved among species. (e) The pedigree chart of the family shows a segregation of TTN variant from the father to the proband and his brother, but ACTC1 variant was spontaneously acquired since it was not present in the parents. The black arrow indicates the proband. (f) Schematic representation of the protein location within the actin and titin protein structures. Actin mutation is located inside the fourth subunit, while titin mutant amino acid is within a region located in the…

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  Figure 5. Comparative analysis between computational structures of wild-type (WT) and p.Ala222Thr actins shows changes in some electrostatic interactions shifts. Electrostatic interactions in WT actin neighboring are affected in mutant variant (right images). The most remarkable interaction shifts are specified with yellow dotted lines: E228 nitrogen–F225 oxygen changes from 2.9 Å to 3.3 Å; E228 oxygen–L223 nitrogen changes from to 3.2 Å to 2.6 Å; T222 oxygen–T222 nitrogen changes from 2.9 Å to 2.8 Å; a new hydrogen bond is generated between E228 nitrogen and D224 oxygen (3.0 Å); a new hydrogen bond is formed between the mutated T222 nitrogen and E228 oxygen (3.1 Å). Blue numbers inside the box of electrostatic interactions express an increase in distance compared to the normal state of WT protein, red numbers express a decrease in distance, and green numbers declare new interactions.

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  Figure 6. Comparative conformations of 11-residue peptide TTN wild-type show a more compacted state compared to E11084K variant. (a) Spatial distribution of TTN in the sarcomere and modeling of the region around the E11084K mutant. Overlay of all allowed conformations (1300 for each; each ribbon shows a single conformation) of the wild-type (right, blue), and mutant (left, red) 11-mer peptides centered on the E11084K mutant shows that the wild-type can adopt more compact conformations than the mutant. (b) Plot of the probability distribution for the end-to-end length of each peptide shows that the mutation causes an increase in end-to-end distance. Wild-type = EEVPPEEEYVP and mutant = EEVPPKEEYVP.