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About Sickkids
About SickKids

Cathy Barr, PhD

Research Institute
Senior Scientist
Neurosciences & Mental Health

University of Toronto

Other Positions

Toronto Western Research Institute
Genetics & Development Division
Senior Scientist

Phone: 416-603-5800 ext. 2744
Fax: 416-603-5745
Email: cbarr@uhnres.utoronto.ca

Research Interests

  • Genetic and epigenetic studies of neuropsychiatric disorders
  • Behaviour
  • Reading disabilities (developmental dyslexia)
  • Specific cognitive process
  • Learning 
  • Memory

Research Activities

The focus of my research is the genetic study of behaviour, specific aspects of cognition, and psychiatric and neurological disorders for which a genetic predisposition has been established, including attention-deficit hyperactivity disorder (ADHD), childhood-onset anxiety disorders, childhood-onset depression, reading disabilities (developmental dyslexia), and Tourette syndrome.

We have identified a number of genes contributing to these disorders and molecular studies are in progress to understand the relationship of DNA variation in these genes to the development of the disorder.  We have recently identified novel genes as associated to ADHD and reading disabilities and we are characterizing the function of these genes.  

For complex traits, it has been predicted that changes in gene expression are more likely to contribute to disease susceptibility than changes in the code for the protein sequence. For a number of the genes we have identified as susceptibility genes, we have ruled out changes in the coding region as contributing to risk, thus we are now searching for the regions that control gene regulation. We collaborated with Dr. Rod Bremner to create genome-wide maps of gene regulatory elements (funding from The Krembil Scientific Development Seed Fund).  Current studies are now focused on determining the impact of DNA variation in these regulatory regions using high-throughput methods to test thousands of regions and the DNA variants within them simultaneously.  

In developing humans and other mammals, not all genes are created equal – or equally used. The expression of certain genes, known as imprinted genes, is determined by just one copy of the parents’ genetic contribution. In humans, there are at least 80 known imprinted genes. If a copy of an imprinted gene fails to function correctly – or if both copies are expressed – the result can be a variety of heritable conditions, such as Prader-Willi and Angelman syndromes, or increased risk for cancer.

To study the mechanism of imprinted genes in mouse brain, we collaborated with Dr. Bing Ren (UCSD) generating a whole-genome, base-resolution map of allelic DNA methylation in the frontal cortex (The Krembil Scientific Development Seed Fund). The study identified many genomic regions that are differentially methylated, dependent on the parent-of-origin. We discovered sequence signatures correlated with CG methylation that are evolutionarily conserved as well as previously unknown genes that are subject to imprinting, including micro RNAs.  

The most surprising finding was significant amounts of methylation outside of the CG dinucleotide context (non-CG) in the brain. This epigenetic mark previously documented only in embryonic stem cells, preimplantation embryos and oocytes, was thought to be a marker of pluripotency. The significance of non-CG methylation is unknown, however the presence of this mark in brain is very specific, suggesting that it correlates with an important biological function (Cell 148(4): 816-831, 2012).

External Funding

  • CIHR
  • Ontario Mental Health Foundation
  • The Krembil Scientific Development Seed Fund
  • Psychiatry Endowment Fund


Barr CL, Xu C, Kroft J, Feng Y, Wigg KG, Zai G, Tannock R, Schachar R, Malone M, Roberts W, Nöthen MM, Grunhage F, Vandenberg DJ, Uhl GR, King N, and Kennedy JL. Haplotype study of three polymorphisms at the dopamine transporter locus confirm linkage to attention-deficit hyperactivity disorder. Biological Psychiatry, 49: 333-339, 2001

Barr CL, Feng Y, Wigg K, Bloom S, Roberts W, Malone M, Schachar R, Tannock R, and Kennedy JL. Identification of DNA variants in the SNAP-25 gene and linkage study of these polymorphisms and attention-deficit hyperactivity disorder. Molecular Psychiatry, 5(4): 405-409, 2000.

Barr CL, Wigg KG, Pakstis AJ, Kurlan R, Pauls D, Kidd KK, Tsui LC, Sandor P. Genome scan for linkage to Gilles de la Tourette Syndrome. American Journal of Medical Genetics, 88: 437-445, 1999.

Barr CL, Sandor P. Current status of genetic studies of Gilles de la Tourette syndrome. Canadian Journal of Psychiatry, 43: 351-357, 1998.