Moyamoya disease is a well-known cerebrovascular disorder of unknown 
pathogenesis affecting terminal portion of internal carotid arteries and causing 
ischemic attacks. Its familial occurrence suggests genetic background. We 
hypothesized that paternally imprinted gene might be associated with this 
disorder. To identify the expressed sequence tags (ESTs) with monoallelic 
expressions on chromosome 3, we used mouse A9 hybrid cells having human 
chromosome 3. Two ESTs showed only maternal expression in mouse A9 hybrid cells, 
and four showed non-expression in the lymphocytes derived from moyamoya 
patients. Although these ESTs are clustered on the same 150 kb region, we 
finally failed to identify cDNA in this region.