The developing brain requires an intricate network of signals to direct proliferation, differentiation and cell fate decisions. Primary cilia are vital organelles with an emerging role regulating several major signalling cascades, in particular the Hedgehog pathway. Talpid3 (Ta3) is 166.7 kD protein found at the distal tip of centrioles. It has been shown to interact with a number of key centriolar proteins and is essential for the formation of primary cilia. A recent mouse model has been designed to conditionally target the highly conserved coiled-coil domain of Ta3 using the Cre/loxP system. This project uncovers the role of Ta3 in the developing brain. It characterises in detail the phenotype of mice with conditional loss of Ta3 in the central nervous system using the Nestin-Cre deleter strain. Morphological and histological analyses demonstrate that significant defects occur postnatally with mice developing severe ataxia and hydrocephaly. Immunohistochemical techniques further characterise the distinct phenotypes of three key brain regions including the cerebellum, cortex and hippocampus. Ta3fl/fl;NesCre mutant mice exhibit defects in the proliferation, organisation, morphology and migration of both neuronal and glial cells. We have shown the mechanistic cause to be the result of widespread loss of primary cilia and a concomitant disruption in the transduction of the Hedgehog signalling pathway. The neural roles of Ta3 are explored further through the optimisation of an in vitro neurosphere system to culture postnatal hippocampal progenitors. The use of a tamoxifen inducible strain allows the timely recombination of Ta3 to study its role in a controlled environment. The cultured cells recapitulate many of the in vivo defects showing loss of primary cilia and reduced migration. Finally, characterisation of the phenotypes seen in the Ta3fl/fl;NesCre mice were shown to resemble neurological traits seen in human conditions with loss of Primary cilia, known as ‘human ciliopathies’. Through clinical collaboration this project demonstrated a human ciliopathy case of Joubert Syndrome with compound heterozygous mutations in TA3. This presents the Ta3fl/fl;NesCre mutant mice as a valuable model system to study a rare but clinically relevant condition.
|Date of Award||25 Nov 2015|
|Supervisor||Vasanta Subramanian (Supervisor) & Ravi Acharya (Supervisor)|
- Cerebral Cortex
- Primary cilia