Trinucleotide repeats consist of three bases consecutively repeated (e.g., CAG CAG CAG CAG CAG CAG CAG) within a region of genomic DNA. Increase in the number of triplets contained within a repeat is a new form of human genetic mutation, known as an expansion mutation. Seven diseases, each with neuropsychiatric features and unusual patterns of inheritance, are caused by expansion mutations. One of these expansion mutations occurs in a gene identified in the laboratory of Dr. Ross. A number of neuropsychiatric disorders, including schizophrenia, bipolar affective disorder, and autism have clinical and neuropathological features and patterns of inheritance similar to the other diseases caused by expansion mutations. In addition, genes with TNRs are frequently transcription factors, and such genes often play a prominent role in neurodevelopment. Together these factors lead to the two hypotheses guiding the proposed research plan: 1) Genes with trinucleotide repeats may regulate aspects of neurodevelopment, and 2) trinucleotide repeat expansion mutation may cause some forms of neuropsychiatric disorders. To test these hypotheses, three specific aims, each tied to a specific career development goal, have been identified. Formal course work and the assistance of collaborators will provide a conceptual context for the technical skills to be acquired in pursuit of each specific aim.
In specific aim #1, the cDNA fragments of previously unidentified genes which contain CAG or CCG repeats will be cloned. The repeats within the clones will be examined for length polymorphisms and collaborators will map each polymorphic clone to a specific loci and test patient DNA for expansion mutation of the newly identified genes.
In specific aims #2 and #3, mRNA and protein expression of selected genes will be examined, with particular emphasis on expression during neurodevelopment. The overall goal of these studies is to identify and characterize genes that are of neurodevelopmental relevance and in which expansion mutations could lead to neuropsychiatric disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Mental Health (NIMH)
Type
Scientist Development Award (K21)
Project #
5K21MH001275-03
Application #
2445424
Study Section
Molecular, Cellular, and Developmental Neurobiology Review Committee (MCDN)
Project Start
1995-07-01
Project End
2000-06-30
Budget Start
1997-07-01
Budget End
1998-06-30
Support Year
3
Fiscal Year
1997
Total Cost
Indirect Cost
Name
Johns Hopkins University
Department
Psychiatry
Type
Schools of Medicine
DUNS #
045911138
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Holmes, S E; O'Hearn, E; Margolis, R L (2003) Why is SCA12 different from other SCAs? Cytogenet Genome Res 100:189-97
Holmes, S E; Hearn, E O; Ross, C A et al. (2001) SCA12: an unusual mutation leads to an unusual spinocerebellar ataxia. Brain Res Bull 56:397-403
Fujigasaki, H; Verma, I C; Camuzat, A et al. (2001) SCA12 is a rare locus for autosomal dominant cerebellar ataxia: a study of an Indian family. Ann Neurol 49:117-21
O'Hearn, E; Holmes, S E; Calvert, P C et al. (2001) SCA-12: Tremor with cerebellar and cortical atrophy is associated with a CAG repeat expansion. Neurology 56:299-303
Holmes, S E; O'Hearn, E E; McInnis, M G et al. (1999) Expansion of a novel CAG trinucleotide repeat in the 5' region of PPP2R2B is associated with SCA12. Nat Genet 23:391-2
Margolis, R L; McInnis, M G; Rosenblatt, A et al. (1999) Trinucleotide repeat expansion and neuropsychiatric disease. Arch Gen Psychiatry 56:1019-31
Nasir, J; Maclean, A; Engelender, S et al. (1999) Chromosomal localization of the Huntingtin associated protein (HAP-1) gene in mouse and humans with radiation hybrid and interspecific backcross mapping. Mamm Genome 10:397-8
Wellington, C L; Ellerby, L M; Hackam, A S et al. (1998) Caspase cleavage of gene products associated with triplet expansion disorders generates truncated fragments containing the polyglutamine tract. J Biol Chem 273:9158-67
Wood, J D; Yuan, J; Margolis, R L et al. (1998) Atrophin-1, the DRPLA gene product, interacts with two families of WW domain-containing proteins. Mol Cell Neurosci 11:149-60
Kleiderlein, J J; Nisson, P E; Jessee, J et al. (1998) CCG repeats in cDNAs from human brain. Hum Genet 103:666-73