MATRIX ATTACHMENT REGIONS IN AN IMPRINTED DOMAIN

DESCRIPTION (Taken from the applicant's Abstract) We propose to study the mechanism of genomic imprinting, a genetic process of importance in development, hormonal regulation and tumorigenesis. The programme has been divided into 2 phases according to the guidelines for the Mentored Clinical Scientist Development Award and will be completed over 5 years. The didactic element of the first phase will include laboratory meetings, research conferences, journal clubs and seminars in the Department of Genetics, as well as formal course work on the molecular genetics of eukaryotes and the nucleus and cell cycle. The research component of this proposal is a test of the hypothesis that matrix-attachment regions (MARs) are involved in genomic imprinting. MARs are DNA sequences which anchor chromatin to a fixed nuclear matrix. Many nuclear factors (such as transcriptional and replication enzymes) are associated with the nuclear matrix, which may explain the many effects in cis found for MARs. As these effects include transcriptional enhancement, DNA replication origination, methylation and chromatin structure determination, they are candidates for controlling genomic imprinting. This is because imprinted domains are characterized by differences in gene expression, replication timing, methylation and chromatin structure between homologous chromosomes. We propose that functional differences in MARs between homologous imprinted regions determine these heterogenous manifestations of imprinting. We describe two MARs from the imprinted domain of distal mouse chromosome 7, the first described from an imprinted region. Supporting our hypothesis that they are important regulatory elements, they exhibit striking sequence conservation with rat. Phase I of this proposal combines the didactic component described with the comprehensive mapping of MARs from this domain. Phase II will concentrate on the functional testing of the MARs by transfection into cultured cells of appropriate constructs, laying the foundation for the production of transgenic mice to fully test the role of these elements in genomic imprinting.