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Loss of KCTD13 Decreases Hippocampal Synaptic Transmission Via the Small Gtpase RhoA
Thursday, May 11, 2017: 12:00 PM-1:40 PM
Golden Gate Ballroom (Marriott Marquis Hotel)
C. Ochoa1, I. Filonova2, A. Walker3, Z. Xuan3, A. J. Eisch4, J. Ellegood5, J. P. Lerch6, H. E. Speed4 and C. M. Powell7, (1)Neurology and Neurotherapeutics, UT Southwestern, Dallas, TX, (2)UT Southwestern, Bedford, TX, (3)UT Southwestern, Dallas, TX, (4)University of Texas Southwestern Medical Center, Dallas, TX, (5)Hospital for Sick Children, Toronto, ON, CANADA, (6)Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada, (7)Neurology & Neurotherapeutics and Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX
Background: Autism Spectrum Disorder (ASD) is a complex neurological disorder that affects brain function.
Copy number variations (CNVs) are implicated in autism. Deletions/duplications within the 16p11.2 chromosomal region are among the most frequent CNVs associated with neurodevelopmental disorders and are one of the most prevalent CNVs in ASD. Deletions within this region are implicated in autism and intellectual disability (ID), whereas duplications are associated with schizophrenia, bipolar, autism, and ID. Of the many genes within this CNV region,
KCTD13 has been implicated in and hypothesized as a major driver of the neuroanatomical and neurodevelopmental phenotypes. KCTD13 acts as an adaptor protein that forms a complex with the ubiquitin-ligase
CUL3, an established autism gene. Together KCTD13-CUL3 ubiquitinate RhoA, a small GTPase that regulates many cellular processes. Interestingly, the KCTD13-CUL3-RhoA interaction has been implicated in contributing to brain size and connectivity in humans. However, little is known regarding the function of KCTD13, and its contribution to neurodevelopmental phenotypes in the mammalian brain.
Objectives: In an effort to understand how loss of Kctd13 might contribute to 16p11.2 deletion pathology, we created a Kctd13 deletion mouse.
Methods: Kctd13 effects on synaptic transmission were determined using extracellular and intracellular recordings of neurons in area CA1 of hippocampus from acute slices. CA1 neuronal morphology and spine density/morphology were analyzed using Golgi-Cox staining. Hippocampal lysate was tested biochemically for alterations in total and active RhoA protein levels via western blots and G-LISA RhoA Activation Assay (Cytoskeleton) respectively. Incubation of acute slice in Rho inhibitors occurred for 3.5 hours followed by extracellular and intracellular recordings of neurons in area CA1 of hippocampus.
Results: We have specifically deleted Kctd13 in mice and demonstrated reduced synaptic transmission correlated with decreased dendritic complexity and spine density in area CA1 the hippocampus. These alterations in synaptic transmission also correlate with increased levels of the KCTD13/CUL3 ubiquitin ligase substrate RhoA. Further, these synaptic phonotypes are reversed by selective RhoA inhibition in situ, confirming increased RhoA as the mechanism underlying reduced synaptic transmission.
Conclusions: These findings implicate Kctd13 in neuronal alterations that may contribute to neuropsychiatric disorders. These data implicate a potential role for RhoA as therapeutic target in disorders associated with deletion of KCTD13 including 16p11.2 deletion.
