Relevant to our research interests in animal models of neuropsychiatric diseases, our Laboratory of Behavioral Neuroscience investigates the behavioral phenotypes of transgenic and knockout mice with mutations in genes expressed in brain pathways involved in neuropsychiatric disorders. We developed and refined a multi-tiered strategy for mouse behavioral phenotyping that is widely used by the international research community. We collaborate with a large number of molecular genetics laboratories, including behavioral testing of COMT knockout mice with Danny Weinberger, NIMH, of serotonin transporter knockout mice with Dennis Murphy, NIMH, and Randy Blakely, Vanderbilt University, and oxytocin and vasopressin receptor knockout mice with Scott Young, NIMH, and Larry Young, Emory University.? ? Dr. Crawley began a new initiative in 2002 to develop mouse behavioral tasks relevant to the symptoms of autism. She learned about the defining behavioral features of autism through a collaboration with Dr. Joseph Piven at the University of North Carolina Center for Autism Research, through attending a large number of lectures by autism researchers at UNC, Dr. Susan Swedos branch at NIMH, and from observing autistic children in classrooms and videotaped interviews. Dr. Crawley contributed to the UNC STAART project at UNC, helping Dr. Piven and Dr. Sheryl Moy set up a mouse behavioral phenotyping laboratory, and participating in a comprehensive mouse strain distribution study. Mouse behavioral genetics experiments were designed to discover genes related to the social deficits that represent the fundamental symptoms of autism. Dr. Crawley and Dr. Moy developed an automated three chambered apparatus that measures sociability and preference for social novelty in mice. George Dold and coworkers in the NIMH Research Services Branch built the prototype apparatus, based partly on previous methods in the literature. Last year, Drs. Crawley and Moy and technicians in the UNC Neurodevelopmental Disorders Research Center completed testing of 20 inbred strains on the social tasks. Robust social interaction with a stranger mouse, as compared to interaction with a non-social novel object, were detected for most inbred strains, including C57BL/6J, DBA/2J, FVB/NJ, C3H/HeJ, AKR/J, PL/J, and SWR/J. Low social approach was detected in A/J, Balb/cJ, BTBR T+tf/J, 129SvImJ, C58/J, NOD/LtJ, and PERA/EiJ. Control tasks to measure general health, neurological reflexes, motor functions, sensory abilities, and anxiety-like behaviors indicated compromised procedural abilities in most of the strains with low social approach. BTBR T+Tf/J (BTBR) demonstrated a highly specific sociability deficit, with normal scores on all other procedural measures, including the elevated plus maze anxiety-related task and open field exploration. DNA microarray studies funded by the STAART project are ongoing at UNC, to discover genes in the backgrounds of BTBR and other strains with social deficits and resistance to change in routine.? ? Here at LBN, we are pursuing the intriguing social deficits in BTBR. Lack of sociability was confirmed in an independently bred cohort raised on a reverse light cycle and tested in the dark phase of the circadian cycle, when mouse social behaviors are maximal. Postdoctoral fellow Mu Yang confirmed the social deficit in BTBR mice raised by normal C57BL/6J mothers, using a cross-fostering technique, to rule out maternal care as a causal factor. To further investigate the apparent social deficit in BTBR, Dr. Hewlet McFarlane, LBN guest researcher, tested BTBR and C57BL/6J (B6) control mice on a juvenile play task. Because autism is diagosed between ages 2 and 7 years old in humans, a comparable age of 21 days was chosen for mice. Using the Noldus Observer event scoring software, and choosing relevant parameters of juvenile social interaction from the literature, Dr. McFarlane scored multiple measures of social approach, following, sniffing, crawling over/under/past, and non-social behaviors during a 30 minute test session in the Noldus video chamber. Pairs of juvenile male BTBR displayed significantly less social approach, nose-to-nose sniffing, and social grooming than pairs of juvenile male B6. Dr. Yang discovered high levels of self-grooming behaviors in BTBR, which she has documented at all stages of development. Postdoctoral fellow Maria Luisa Scattoni detected unusual pattterns of vocalizations in BTBR. Collaborators Dr. Valerie Bolivar and student Jennifer Phoenix at the Wadsworth Center for Genome Research in Troy, NY discovered deficits in social transmission of food preference in BTBR. These findings of a highly selective social deficit in BTBR raise the possibility that this commercially available inbred strain may represent a mouse model of autism for wide translational applications. ? ? Collaborator Gretchen Kusek, a graduate student at the Wadsworth Center, examined the JAX database for unusual single nucleotide polymorphisms (SNPs) in the coding regions of genes in the BTBR background. Three unique SNPs were detected in nonsynonymous coding region of the gene for Kmo, kynurenine-3-hydroxylase, an enzyme that regulate the metabolism of kynurenic acid in the brain. Kynurenic acid mediates neuronal survival and dendritic spine formation. These findings provide a proof of principle for using social deficits in inbred strains of mice to generate new hypotheses about unpredicted genes that could mediate symptoms of autism. ? ? A second approach toward identifying the genes mediating the diagnostic symptoms of autism is to evaluate the behaviors of lines of mice with experimentally targeted mutations in candidate genes proposed to be relevant to autism. Comprehensive behavioral phenotyping was conducted on several interesting lines in the past year. Two independent lines of oxytocin knockout mice, one generated by Dr. W. Scott Young, NIMH, ane one generated by Dr. Larry Young, Emory University, both displayed normal social approach in our automated three-chambered apparatus. Our negative findings in both lines of oxytocin null mutants on general social approach underscore the selective deficit in social memory previously reported by the Emory researchers for the oxytocin null mutants from Baylor, and argue against a role for oxytocin in general sociability. ? ? Vasopressin receptor knockout mice generated by Drs. Heather Caldwell and Scott Young, NIMH, similarly did not show a genotype difference on the social approach task, nor on juvenile play. Postdoctoral fellow Maria Luisa Scattoni found normal mouse pup separation vocalizations, but some genotype-related differences in adult female V1b mice in a resident-intruder test. These findings support the well-established literature on the role of vasopressin in aggression, and argue against a role for vasopressin in general sociability.? ? Neuroligin-3 is a synaptic protein that has been implicated in autism. Neuroligin-3 mutant mice were obtained from Dr. Nat Heintz and the GenSat Project at Rockefeller University. Postdoctoral fellow Kathy Chadman is presently testing all genotypes and both sexes of mice with mutations in this X-linked gene on our entire sequence of control measures, social behaviors, and repetitive behaviors. Dr. Scattoni is analyzing vocalizations in neuroligin-3 pups.? ? Polymorphisms in the serotonin transporter gene have been reported in some cases of autism. We are investigating social behaviors in Dr. Dennis Murphys 5-HTT knockout mice. Our UNC postdoctoral fellow Bryce Ryand, and Dr. Randy Blakelys clinical fellow Jeremy Veenstra-Vanderweele at Vanderbilt University, are testing 5-HTT mice on different social tasks in collaboration with Dr. Crawley.
Showing the most recent 10 out of 32 publications
