Mitochondrial function in mice and human patients with telomere disorders

Author(s)

André Luiz Pinto Santos

• Document type: Master's Dissertation
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto
• Defense date: 10 dez. 2018

Examining board members

Rodrigo do Tocantins Calado de Saloma Rodrigues; Luciane Carla Alberici; Luis Francisco Zirnberger Batista; Fabíola Traina

• Advisor: Rodrigo do Tocantins Calado de Saloma Rodrigues

Abstract

Mutations in telomere-related genes are the molecular basis of a phenotypically heterogeneous group of disorders that are collectively termed telomeropathies. The prototype of telomeropathies is the dyskeratosis congenita (DC), an inherited bone marrow failure characterized by mucocutaneous stigmata and aplastic anemia (AA). In murine telomerase knockout models, telomere shortening provokes mitochondrial deficiency and increases reactive oxygen species (ROS) production. However, the mitochondrial function in human telomeropathies has not been addressed. We evaluated mitochondrial parameters in fibroblasts from four healthy individuals (controls) and six patients with inherent bone marrow failure (DC and AA), carrying pathogenic variants in TERC, DKC1, RTEL1 and POT1 genes and, consequently, telomere shortening (<10th percentile). Patient fibroblasts displayed an 85% increment in mitochondrial mass, resulting in a 71% increase in oxygen consumption in the state of maximum respiration (ETS) compared to controls. As a consequence, mitochondrial ROS production was 74% higher in patients\' fibroblasts than in controls. Increased ROS level may explain the overexpression of SOD1 and UCP1 observed in patient cells. We further assessed the mitochondrial DNA (mtDNA) copy number in fibroblasts and peripheral blood of patients with telomere shortening. The mtDNA content was significantly higher in patients compared to controls. These findings indicate that mitochondria are affected in human telomere diseases and may play a role in disease development. Furthermore, overproduction of mitochondrial ROS could induce oxidative stress and result in somatic mutations in hematopoietic stem-cells, causing clonal disorders in patients with telomeropathies (AU)

• FAPESP's process: 16/03620-8 - Evaluation of the mitochondrial function in human patient and mice with telomeropathies
• Grantee: André Luiz Pinto Santos
• Support type: Scholarships in Brazil - Master