The pathology of the Michelin tire baby syndrome

This grant application deals with a rare genetic disorder commonly referred to as the Michelin tire baby syndrome. Patients with this disease present with an array of symptoms including; intellectual impairment, epilepsy, flat faces, smaller brains, short stature, and very unusual skin folds. These skin folds have prompted clinicians to call the disease circumferential skin creases Kunze type (CSC-KT). Until recently the cause of this condition was not known, but working in collaboration with a group in Belgium, we have recently shown that it is due to genetic mutations in two different genes called EB2 or TUBB5. These genes encode for proteins that are involved with the microtubule cytoskeleton of the cell. Microtubules are the cells internal scaffold and are important for separating the chromosomes during mitosis and mediating cellular movement. The goal of this study is to investigate how mutations in EB2 and TUBB5 cause the Michelin tire baby syndrome. To do this we will first determine which cells in the brain and skin express EB2 and TUBB5. Next we will make two different genetically modified mice that have the same mutations as affected patients. We will put these mice through a battery of tests examining the performance in cognitive tasks, investigating the structure of their brain and the molecular architecture of their microtubules. We will complement these mouse studies with a new state-of- the-art technique which enables the generation of human cerebral organoids, commonly referred to as mini-brains. These organoids are a valuable tool as they recapitulate aspects of human brain development in cell culture. We will a genetic system known as CRISPR-Cas9 to make organoids that have the same mutations as patients with the Michelin tire baby syndrome, and compare them to organoids without mutations. The results of this study will provide insight into the mechanisms that cause the Michelin tire baby syndrome, which in time may lead to the development of novel therapeutics. Importantly, it will also shed light on a growing spectrum of disease states that are associated with the microtubule cytoskeleton.