Treacher Collins Syndrome: mechanisms responsible for clinical variability and in search of molecules to rescue the phenotype

Abstract

Treacher Collins Syndrome (TCS) is a rare craniofacial disorder mainly characterized by hypoplasia of the facial bones, cleft palate and ear abnormalities. Most of the cases (~93%) are caused by mutations in gene TCOF1. Although intra and interfamilial clinical impairment with grand levels of variability is observed, the etiological mechanisms are still unknown. Several studies using animal models for TCS demonstrated, in neuroepithelial cells, a high production of Reactive Oxygen Species (ROS), ribosomal biogenesis deregulation, stress, DNA oxidative damage and apoptosis, resulting in TCS craniofacial phenotypes. These phenotypes can be ameliorated through maternal treatment during gestational period with antioxidants, through reduction of neuroepithelial apoptosis rates. Since mitochondria is the main source of ROS and is involved with various cellular signaling roles, besides the ones already associated with apoptosis, it is relevant to study this organelle's role in TCS pathophysiology. Therefore, we propose to investigate the mechanisms responsible for TCS clinical variability, as well as the mitochondria role in a human embryonic development model. We will use iPSC-derived neuroepithelial cells of 5 patients with TCS and of 4 unaffected individuals. First, we are going to test whether the pathogenic mechanisms described in animal models are applicable to TCS in humans. Then, we are going to investigate if the apoptosis rate and levels of p53 differ between groups. Next, we will search for molecules to restore/ameliorate the cellular phenotype, such as p53 inhibitors and antioxidants. The levels of DNA damage and of protein synthesis will also be evaluated, as well as if there are alterations in mitochondria activity due to TCOF1's deficiency and/or of other protein of the same pathway. Therefore, we are going to analyze the O2 consumption's rate, the H2O2 production and the GSH/GSSH ratio. If differences in these mechanisms are found, we are going to investigate its relationship with the clinical variability observed in TCS, using this in vitro model. With this project, we expect to contribute for a better understanding not only about the mechanisms responsible for clinical variability, but also about the mitochondria role for TCS pathogenicity. Besides, we are going to contribute for the development of possible prospective treatments or prevention of severe forms with the use of human cellular model. (AU)