International Mammalian Genome Society

logo18th International Mouse Genome Conference

17-22 October 2004, Seattle, USA


POSTER 158 - ENU MUTAGENESIS REVEALS A NEW ROLE FOR THE AF4 PROTEIN FAMILY IN NEURODEGENERATION

Oliver PL, Bitoun E, Clark J, Davies KE

MRC Functional Genetics Unit, Oxford, United Kingdom

We have used ENU mutagenesis to identify new models of neurological disease and have characterised a novel cerebellar mutant named robotic. It displays a jerky, ataxic gait that is caused by an adult-onset loss of Purkinje cells that occurs in a striking region-specific pattern. The causative mutation was identified in a highly conserved region of the putative transcription factor, Af4, and we have shown that this gene is expressed specifically in Purkinje cells. Af4 has previously been implicated in leukaemia, but its function in the brain is unknown.

From a yeast-two hybrid screen in the brain, we identified an ubiquitin ligase as a novel binding partner of Af4. We were able confirm this interaction and demonstrate co-localisation of these proteins both in vitro and in vivo. In addition, quantitative binding assays revealed a highly significant reduction in affinity of this interaction with mutant protein, suggesting that normal turnover of Af4 by the proteosome is blocked in the robotic mouse. To identify potential targets of Af4 transcriptional regulation, a microarray study was carried out using wild-type and robotic cerebellar samples across a time-course. In situ hybridisation results from differentially regulated genes have provided clues to the pathways involved in Purkinje cell death.

The discovery that Af4 is involved in movement and behavioural disorders has implications for other members of the highly conserved Af4 protein family, including Fmr2, revealing more about their normal function and contribution to human disorders as diverse as leukaemia, mental retardation and neurodegenerative disease.

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