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Biomedical subjects

A A Wylie

Publications and source records attributed to A A Wylie.

8 recordsLinked to original sources
PubMed2003

Epigenetic detection of human chromosome 14 uniparental disomy.

The recent demonstration of genomic imprinting of DLK1 and MEG3 on human chromosome 14q32 indicates that these genes might contribute to the discordant phenotypes associated with uniparental disomy (UPD) of chromosome 14. Regulation of imprinted expression of DLK1 and MEG3 involves a differentially methylated region (DMR) that encompasses the MEG3 promoter. We exploited the normal differential methylation of the DLK1/MEG3 region to develop a rapid diagnostic PCR assay based upon an individual's epigenetic profile. We used methylation-specific multiplex PCR in a retrospective analysis to amplify divergent lengths of the methylated and unmethylated MEG3 DMR in a single reaction and accurately identified normal, maternal UPD14, and paternal UPD14 in bisulfite converted DNA samples. This approach, which is based solely on differential epigenetic profiles, may be generally applicable for rapidly and economically screening for other imprinting defects associated with uniparental disomy, determining loss of heterozygosity of imprinted tumor suppressor genes, and identifying gene-specific hypermethylation events associated with neoplastic progression.

Chromosomes, Human, Pair 14↗
PubMed2001

Divergent evolution in M6P/IGF2R imprinting from the Jurassic to the Quaternary.

M6P/IGF2R imprinting first appeared approximately 150 million years ago following the divergence of prototherian from therian mammals. Although M6P/IGF2R is clearly imprinted in opossums and rodents, its imprint status in humans remains ambiguous. It is also still unknown if M6P/IGF2R imprinting was an ancestral mammalian epigenotype or if it evolved convergently. We report herein that M6P/IGF2R is imprinted in Artiodactyla, as it is in Rodentia and Marsupialia, but that it is not imprinted in Scandentia, Dermoptera and Primates, including ringtail lemurs and humans. These results are most parsimonious with a single ancestral origin of M6P/IGF2R imprinting followed by a lineage-specific disappearance of M6P/IGF2R imprinting in Euarchonta. The absence of M6P/IGF2R imprinting in extant primates, due to its disappearance from the primate lineage over 75 million years ago, demonstrates that imprinting at this locus does not predispose to human disease. Moreover, the divergent evolution of M6P/IGF2R imprinting predicts that the success of in vitro embryo procedures such as cloning may be species dependent.

Animals↗
PubMed2001

Imprinting of PEG3, the human homologue of a mouse gene involved in nurturing behavior.

The paternally expressed Peg3 gene in mice encodes an unusual Krüppel-type zinc finger protein implicated in critical cellular and behavioral functions including growth, apoptosis, and maternal nurturing behavior. Methylation and expression analyses were used to determine whether PEG3 on chromosome 19q13.4 is imprinted in humans. The PEG3 promoter is encompassed within a large CpG-rich region that is differentially methylated in fetal tissues. Furthermore, expression studies demonstrate that PEG3 is ubiquitously imprinted throughout development and postnatally. Multiple isoforms of the PEG3 gene, including a novel transcript, are paternally expressed. These results are the first to show that human chromosome 19q13.4 contains an imprinted region. The imprinted status of PEG3 throughout life coupled with its neural expression and putative roles in regulating cell growth suggests that PEG3 may be a susceptibility locus for cancer as well as neurobehavioral deficits.

Amino Acid Sequence↗
PubMed2001

The neuronatin gene resides in a "micro-imprinted" domain on human chromosome 20q11.2.

A small fraction of the genome contains genes that are imprinted and thus expressed exclusively from one parental allele. We report here that the human neuronatin gene (NNAT) on chromosome 20q11.2 is imprinted and transcribed specifically from the paternal allele. The region containing NNAT has multiple CpG islands, and methylation analysis showed that a 1.8-kb CpG island in its promoter region exhibits differential methylation in all tissues examined. This finding is consistent with the island acting as a component of the NNAT imprint control domain. NNAT lies within the singular 8.5-kb intron of the gene encoding bladder cancer-associated protein (BLCAP), which, as we demonstrate, is not imprinted. This study provides the first example, to our knowledge, in humans of an imprinted gene contained within the genomic structure of a nonimprinted gene. Thus, NNAT is in an imprinted "microdomain," making this locus uniquely suited for the investigation of mechanisms of localized imprint regulation.

Alleles↗
PubMed2000

Novel imprinted DLK1/GTL2 domain on human chromosome 14 contains motifs that mimic those implicated in IGF2/H19 regulation.

The evolution of genomic imprinting in mammals occurred more than 100 million years ago, and resulted in the formation of genes that are functionally haploid because of parent-of-origin-dependent expression. Despite ample evidence from studies in a number of species suggesting the presence of imprinted genes on human chromosome 14, their identity has remained elusive. Here we report the identification of two reciprocally imprinted genes, GTL2 and DLK1, which together define a novel imprinting cluster on human chromosome 14q32. The maternally expressed GTL2 (gene trap locus 2) gene encodes for a nontranslated RNA. DLK1 (delta, Drosophila, homolog-like 1) is a paternally expressed gene that encodes for a transmembrane protein containing six epidermal growth factor (EGF) repeat motifs closely related to those present in the delta/notch/serrate family of signaling molecules. The paternal expression, chromosomal localization, and biological function of DLK1 also make it a likely candidate gene for the callipyge phenotype in sheep. Many of the predicted structural and regulatory features of the DLK1/GTL2 domain are highly analogous to those implicated in IGF2/H19 imprint regulation, including two hemimethylated consensus binding sites for the vertebrate enhancer blocking protein, CTCF. These results provide evidence that a common mechanism and domain organization may be used for juxtapositioned, reciprocally imprinted genes.

Amino Acid Motifs↗
PubMed1999

Genomic imprinting: implications for human disease.

Genomic imprinting refers to an epigenetic marking of genes that results in monoallelic expression. This parent-of-origin dependent phenomenon is a notable exception to the laws of Mendelian genetics. Imprinted genes are intricately involved in fetal and behavioral development. Consequently, abnormal expression of these genes results in numerous human genetic disorders including carcinogenesis. This paper reviews genomic imprinting and its role in human disease. Additional information about imprinted genes can be found on the Genomic Imprinting Website at http://www.geneimprint.com.

Angelman Syndrome↗
PubMed1997

Regulated expression of a foreign gene targeted to the ischaemic myocardium.

OBJECTIVES: Regulated expression of transferred foreign genes may be an important feature of gene therapy. Because coronary artery disease often involves intermittent myocardial ischaemia followed by periods of normal cardiac function it will probably be necessary to regulate the expression of putative therapeutic/cardioprotective genes directly in response to ischaemia-associated signals. The objectives of the current study were to develop a combination of gene regulatory components that can be used to target a product to the myocardium and limit the expression of the gene to periods of ischaemic activity. METHODS: Expression plasmids were constructed containing muscle-specific promoters and hypoxia-responsive enhancer elements linked to a reporter gene. The regulation of these constructs by hypoxia or experimental ischaemia was measured following transient expression in cultured cells or after direct injection of DNA into the rabbit myocardium. RESULTS: A single set of hypoxia response elements placed immediately upstream of the minimal muscle-specific alpha-myosin heavy chain promoter conferred potent positive regulation of this promoter by hypoxia in vitro and by ischaemia in vivo. Induction by ischaemia persisted for at least 4 h and returned to the baseline level within 8 h. CONCLUSIONS: Hypoxia responsive regulatory elements, in combination with weak tissue-restricted promoters incorporated into an appropriate vector system may allow controlled expression of a therapeutic gene in ischaemic myocardium.

Animals↗