Knock in Mouse Models and Microtubule Associated Cortical Development Disorders

Epilepsy is a common neurological disorder that affects more than 50 million people globally. In some instances the disease can be treated with drugs, but in many cases this is not possible. Drug-resistant epilepsy has devastating personal, social and economic consequences, which is reflected by the recent declaration from the World Health Organization that epilepsy is a major public health concern. Some cases of drug resistant epilepsy have been associated with changes in the structure of the brain and mutations in the Tubulin gene family. In this project our goal is to understand how mutations in these genes (TUBA1A, TUBB3, TUBB5 and TUBG1) cause epilepsy. To do this we will use genetically modified mice that carry human disease causing mutations. We will study: the behaviour of these mice; their brains during development; the cellular characteristics of the neurons; and the genes expressed in key brain areas. Our results will contribute to a deeper understanding of the causes of epilepsy and brain disease, and may identify targets that could be exploited to modulate epilepsy severity.

Epilepsy is a common neurological disorder that affects more than 50 million people globally. In some instances the disease can be treated with drugs, but in many cases this is not possible. Drug-resistant epilepsy has devastating personal, social and economic consequences, which is reflected by the recent declaration from the World Health Organization that epilepsy is a major public health concern. Some cases of drug resistant epilepsy have been associated with changes in the structure of the brain and mutations in the Tubulin gene family. The tubulins are a class of proteins that make up a cells scaffold, and are important for the generation of new neurons, and their maturation. In addition they function as highways within a cell, allowing the trafficking of cellular cargo. Molecules that participate in this trafficking bind to microtubules and are referred to as microtubule associated proteins. In this project we investigated how different genetic mutations in tubulins and microtubule-associated proteins cause intellectual impairment, structural brain defects, and epilepsy. To achieve this we generated mice that carry human mutations using advanced genetic methods. We then studied these mice using a range of tests that assessed various behavioral attributes including their: motor co-ordination, startle response and anxiety, as well as monitoring whether or not they experienced seizures. In addition we also carefully studied how their brains developed to see whether the same number of nerve cells were generated, whether these neurons were in the correct place, and to see whether they functioned properly. Our project had three major outcomes: 1) We identified a new gene called MAST1 that causes epilepsy, movement disorders and severe intellectual impairment. We showed that MAST1 is a protein that associates with the microtubule cytoskeleton and is found in many neurons in the developing brain. We showed that mutations in this gene cause neurons to form unusual connections in the brain and to die prematurely, which we believe contributes to the disease in humans. 2) We have studied how mutations in the Tubulin Gene TUBB5 cause epilepsy and a reduction in brain size. Using our mice we discovered that there are subtle defects in the generation of new neurons, which contributes to their premature loss. 3) We have studied the behavior of TUBB5 mice, discovering that like affected patients they have defects in motor co-ordination and exhibit hyper excitable phenotypes. Collectively we are now in a better position to diagnose and design rational treatments for these severe neurological disorders.