Protein haploinsufficiency drivers identify MYBPC3 mutations that cause hypertrophic cardiomyopathy

Carmen Suay-CorrederaMaria Rosaria PricoloElias Herrero-GalanDiana Velazquez-CarrerasDavid Sanchez-OrtizDiego Garcia-GiustinianiJavier DelgadoJuan Jose Galano-FrutosHelena Garcia-CebolladaSilvia VilchesFernando DominguezMaria Sabater MolinaRoberto Barriales-VillaGiulia FrissoJavier SanchoLuis SerranoPablo Garcia-PaviaLorenzo MonserratJorge Alegre-Cebollada.

Abstract: Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease. Mutations in MYBPC3, the gene encoding cardiac myosin-binding protein C (cMyBP-C), are a leading cause of HCM. However, it remains challenging to define whether specific gene variants found in patients are pathogenic or not, limiting the reach of cardiovascular genetics in the management of HCM. Here, we have examined cMyBP-C haploinsufficiency drivers in 68 clinically annotated non-truncating variants of MYBPC3. We find that 45% of the pathogenic variants show alterations in RNA splicing or protein stability, which can be linked to pathogenicity with 100% and 94% specificity, respectively. Relevant for variant annotation, we uncover that 9% of non-truncating variants of MYBPC3 currently classified as of uncertain significance induce one of these molecular phenotypes. We propose that alteration of RNA splicing or protein stability caused by MYBPC3 variants provide strong evidence of their pathogenicity, leading to improved clinical management of HCM patients and their families.

Link a la publicación.

Nanorheology of living cells measured by AFM-based force–distance curves

Pablo D. Garcia, Carlos R. Guerrero and Ricardo Garcia

Abstract: Mechanobiology aims to establish functional relationships between the mechanical state of a living a cell
and its physiology. The acquisition of force–distance curves with an AFM is by far the dominant method to characterize the nanomechanical properties of living cells. However, theoretical simulations have shown that the contact mechanics models used to determine the Young’s modulus from a force–distance curve could be off by a factor 5 from its expected value. The semi-quantitative character arises from the lack of a theory that integrates the AFM data, a realistic viscoelastic model of a cell and its finitethickness. Here, we develop a method to determine the mechanical response of a cell from a force–distance curve. The method incorporates bottom-effect corrections, a power-law rheology model and the deformation history of the cell. It transforms the experimental data into viscoelastic parameters of the cell as a function of the indentation frequency. The quantitative agreement obtained between the experiments performed on living fibroblast cells and the analytical theory supports the use of force–distance curves to measure the nanorheological properties of cells.

Link a la publicación.

Double-stranded RNA bending by AU-tract sequences

Alberto Marin-Gonzalez, Clara Aicart-Ramos, Mikel Marin-Baquero, Alejandro Martín-González, Maarit Suomalainen, Abhilash Kannan, J. G. Vilhena, Urs F. Greber, Fernando Moreno-Herrero and Rubén Pérez.

Abstract: Sequence-dependent structural deformations of the DNA double helix (dsDNA) have been extensively
studied, where adenine tracts (A-tracts) provide a striking example for global bending in the molecule. In
contrast to dsDNA, much less is known about how the nucleotide sequence affects bending deformations
of double-stranded RNA (dsRNA). Using all-atom microsecond long molecular dynamics simulations we
found a sequence motif consisting of alternating adenines and uracils, or AU-tracts, that bend the dsRNA
helix by locally compressing the major groove. We experimentally tested this prediction using atomic force
microscopy (AFM) imaging of long dsRNA molecules containing phased AU-tracts. AFM images revealed a
clear intrinsic bend in these AU-tracts molecules, as quantified by a significantly lower persistence length
compared to dsRNA molecules of arbitrary sequence. The bent structure of AU-tracts here described might
play a role in sequence-specific recognition of dsRNAs by dsRNA-interacting proteins or impact the folding
of RNA into intricate tertiary and quaternary structures.

Link a la publicación.