Title:
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Identifying imprinted genes on mouse chromosome 12 : novel approaches
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The distal portion of mouse chromosome 12 (chr.12) has been shown to be imprinted through translocation studies, with both maternal and paternal duplications and deficiencies causing embryonic lethality. The region shares homology primarily with human chromosome 14. An imprinted disorder has been attributed to maternal duplication/paternal deficiency of human chromosome 14 commonly referred to as maternal uniparental disomy (mUPD14). mUPD14 results in short stature, premature puberty, development delay, small hands with hyperextensible joints and other minor anomalies. These pieces of evidence suggest that mouse chromosome 12 and human chromosome 14 harbour imprinted genes with important roles in development. This dissertation discusses two approaches to identifying imprinted genes on mouse chr.12 with particular attention being given to identifying genes in the highly conserved homologous domain. A cDNA screen was devised which was expected to enrich a d8.5 embryonic cDNA library for chromosome 12 specific transcripts. The aim of the screen was to isolate highly conserved, developmental regulated candidate genes mapping to chr.12, which could also be assayed for imprinting. Genes already described to some extent and known to map within the region of homology were also chosen and assayed for imprinting using two candidate screening approaches; SSCP and Northern blotting of UPD and normal RNA. Candidate genes assay for imprinting using mRNA from normal, mUPD12 and pUPD12 embryos identified two new imprinted genes, Gtl-2 and Dlk. SSCP analysis eliminated Tgfβ3, which was considered as a candidate. The cDNA screen showed depletion for cDNA that did not map to chr.12 and there may have been some level of enrichment for clones mapping to chr.12. The results of these studies are described in detail.
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