Vett Lloyd

Publications (4)3.8 Total impact

• Article: The Drosophila homolog of the mammalian imprint regulator, CTCF, maintains the maternal genomic imprint in Drosophila melanogaster

  William MacDonald, Debashish Menon, Nicholas Bartlett, Sperry G Elizabeth, Vanya Rasheva, Victoria Meller, Vett Lloyd
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  ABSTRACT: Abstract Background CTCF is a versatile zinc finger DNA-binding protein that functions as a highly conserved epigenetic transcriptional regulator. CTCF is known to act as a chromosomal insulator, bind promoter regions, and facilitate long-range chromatin interactions. In mammals, CTCF is active in the regulatory regions of some genes that exhibit genomic imprinting, acting as insulator on only one parental allele to facilitate parent-specific expression. In Drosophila , CTCF acts as a chromatin insulator and is thought to be actively involved in the global organization of the genome. Results To determine whether CTCF regulates imprinting in Drosophila , we generated CTCF mutant alleles and assayed gene expression from the imprinted Dp(1;f)LJ9 mini-X chromosome in the presence of reduced CTCF expression. We observed disruption of the maternal imprint when CTCF levels were reduced, but no effect was observed on the paternal imprint. The effect was restricted to maintenance of the imprint and was specific for the Dp(1;f)LJ9 mini-X chromosome. Conclusions CTCF in Drosophila functions in maintaining parent-specific expression from an imprinted domain as it does in mammals. We propose that Drosophila CTCF maintains an insulator boundary on the maternal X chromosome, shielding genes from the imprint-induced silencing that occurs on the paternally inherited X chromosome. See commentary: http://www.biomedcentral.com/1741-7007/8/104
  BMC Biology. 01/2010;
• Article: The white gene of Drosophila melanogaster encodes a protein with a role in courtship behavior.

  Matthew Anaka, C Danielle MacDonald, Eva Barkova, Karl Simon, Reem Rostom, Ruth A Godoy, Andrew J Haigh, Ian A Meinertzhagen, Vett Lloyd
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  ABSTRACT: The white gene of Drosophila melanogaster has been extensively studied, yet it is still not understood how its ectopic overexpression induces male-male courtship. To investigate the cellular basis of this behavior, we examined the sexual behavior of several classes of mutants. We find that male-male courtship is seen not only in flies overexpressing the white gene, but also in mutants expected to have mislocalized White protein. This finding confirms that mislocalizing White transporter in the cells in which it is normally expressed will produce male-male courtship behaviors; the courtship behavior is not an indirect consequence of aberrant physiological changes elsewhere in the body. Male-male courtship is also seen in some mutants with altered monoamine metabolism and deficits in learning and memory, but can be distinguished from that produced by White mislocalization by its reduced intensity and locomotor activity. Double mutants overexpressing white and with mutations in genes for serotonergic neurons suggest that male-male courtship produced by mislocalizing White may not be mediated exclusively by serotonergic neurons. We also find decreased olfactory learning in white mutants and in individuals with mutations in the genes for White's binding partners, brown and scarlet. Finally, in cultured Drosophila and mammalian cells, the White transporter is found in the endosomal compartment. The additional genes identified here as being involved in male-male courtship increase the repertoire of mutations available to study sexual behavior in Drosophila.
  Journal of neurogenetics 12/2008; 22(4):243-76. · 0.73 Impact Factor
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  Available from: mta.ca

  Article: Genomic imprinting in Drosophila has properties of both mammalian and insect imprinting.

  Matthew Anaka, Audra Lynn, Patrick McGinn, Vett K Lloyd
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  ABSTRACT: Genomic imprinting is a process that marks DNA, causing a change in gene or chromosome behavior, depending on the sex of the transmitting parent. In mammals, most examples of genomic imprinting affect the transcription of individual or small clusters of genes whereas in insects, genomic imprinting tends to silence entire chromosomes. This has been interpreted as evidence of independent evolutionary origins for imprinting. To investigate how these types of imprinting are related, we performed a phenotypic, molecular, and cytological analysis of an imprinted chromosome in Drosophila melanogaster. Analysis of this chromosome reveals that the imprint results in transcriptional silencing. Yet, the domain of transcriptional silencing is very large, extending at least 1.2 Mb and encompassing over 100 genes, and is associated with decreased somatic polytenization of the entire chromosome. We propose that repression of somatic replication in polytenized cells, as a secondary response to the imprint, acts to extend the size of the imprinted domain to an entire chromosome. Thus, imprinting in Drosophila has properties of both typical mammalian and insect imprinting which suggests that genomic imprinting in Drosophila and mammals is not fundamentally different; imprinting is manifest as transcriptional silencing of a few genes or silencing of an entire chromosome depending on secondary processes such as differences in gene density and polytenization.
  Archiv für Entwickelungsmechanik der Organismen 12/2008; 219(2):59-66. · 1.77 Impact Factor
• Article: Genome and chromosome structure: Twelve dynamic and evolving genomes.

  Vett K Lloyd, Kathleen Fitzpatrick
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  ABSTRACT: Chromosomes are not inert structures that haul the genome through cell division. The dynamic properties of chromosomes, during the cell cycle, the lifetime of the organism and across evolutionary time, featured prominently at the 49(th) Annual Drosophila Research Conference. Platform presentations, workshops and posters focused on many aspects of chromosome structure and function including chromosome interactions such as trans-silencing and pairing between homologous and non-homologous chromosomes, specialized portions of the chromosome including the centromere and telomeres, the structure, function and evolution of the large heterochromatic domains such as the Y and 4(th) chromosomes, centric heterochromatin and subtelomeric heterochromatin. The speed of evolutionary changes in these regions, and the consequences for speciation and hybrid-incompatibility, were recurring themes. Finally, there was considerable new insight offered into the mechanics by which chromosomes are rearranged and changes in the types of alterations occurring over the lifetime of the organism, which can result in novel genes and gene flow between chromosomes. The availability of the twelve sequenced Drosophila genomes has allowed new insights into the structure, function and evolutionary transformation of chromosomes and genomes that will continue to transform our view of the chromosome as a dynamic and flexible entity that houses and regulates the genome.
  Fly 06/2008; 2(3):141-4. · 1.30 Impact Factor