Mellissa RW Mann, PhD

Associate Professor, Obstetrics, Gynecology, and Reproductive Sciences

Research

Description

Genomic Imprint Regulation in Gametes and Early Embryos

Research in Dr Mellissa Mann’s laboratory focuses on molecular mechanisms that regulate genomic imprinting during gametogenesis and early embryo development. Genomic imprinting is defined as a mechanism of transcriptional regulation that restricts expression to one parental allele. Imprinting is a multi-step process that begins in the gametes, where epigenetic modifications differentially mark the parental alleles. These marks must then be stably maintained in the developing embryo where they are translated into parental-specific expression. Errors in any of these stages can lead to genomic imprinting disorders, such as Beckwith-Wiedemann Syndrome, Angelman Syndrome, and Silver-Russell Syndrome. To strike a competitive edge, we have developed novel methodology for assessing genomic imprinting in single oocytes and preimplantation embryos, as well as a unique and powerful RNA interference system for stem cells. These tools have enabled my lab to perform cutting-edge research on four main projects using the mouse as a model system.

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1. Effects of Assisted Reproductive Technologies on Genomic Imprint Maintenance

Children conceived by assisted reproduction technologies are at increased risk of intrauterine growth retardation, premature birth, low birth weight, and possibly genomic imprinting disorders. Dr Mann’s research has lead the field by produced extensive and novel data showing that preimplantation development is a critical period of imprint maintenance that is susceptible to epigenetic perturbation during oocyte and embryo manipulation. Our current work will determine how hormone stimulation or in vitro embryo culture perturbs genomic imprint maintenance.

 

Dynamic changes in DNA methylation programming coincide with assisted reproductive technologies

Dynamic changes in DNA methylation programming coincide with assisted reproductive technologies

2. Role of the Kcnq1ot1 long noncoding in stem cells and early embryos

There is little information of how imprinted gene expression is established across an imprinted domain during preimplantation development and its maintenance during early postimplantation development. To better understand the regulatory events in early embryos, we are using genetic models to more precisely determine the timing of paternal allelic silencing of genes within the domain and whether the Kcnq1ot1imprinting control region and/or the Kcnq1ot1 noncoding RNA are required for establishment and maintenance of paternal allelic silencing.

 

The paternal Kcnq1ot1 domain, which is coated by the Kcnq1ot1 noncoding RNA (ncRNA, green), localizes to the periphery (nuclear pore complex (NPC) signal, red) of the nucleus (DAPI, blue stain)

The paternal Kcnq1ot1 domain, which is coated by the Kcnq1ot1 noncoding RNA (ncRNA, green), localizes to the periphery (nuclear pore complex (NPC) signal, red) of the nucleus (DAPI, blue stain)

3. Imprinted domain regulation

Very little is known about mechanisms that regulate genomic imprinting during early development. Using an improved lentiviral transgene delivery system, an RNAi library for epigenetic modifiers and hybrid stem cells that that we generated, we have conducted a positive selection, loss of function, RNA interference screen for epigenetic factors that regulate genomic imprinting, using the Kcnq1ot1 domain as a model imprinted domain. We have identified novel candidate factors involved in imprinted gene regulation as well as discovered a novel mechanism of imprinted domain regulation that we are currently investigating.

 

Derivation of stem cells from the three lineages of the blastocyst-stage mouse embryo

Derivation of stem cells from the three lineages of the blastocyst-stage mouse embryo

4. Identification of genomic imprinting control regions

An intriguing characteristic of imprinted genes is that they often cluster in large chromosomal domains that are co-ordinately regulated by cis-acting regions, known as imprinting control regions. To identify novel imprinting control regions, we have used extensive bioinformatics screening of publicly available database. Based on defined epigenetic profiles, we identified known and novel imprinting control regions. We are currently investigation these identify novel imprinting control regions and novel neighboring imprinted genes.

 

Selected Publications

  • White CR, Denomme MM, Tekpetey FR, Feyles V, Power SGA and Mann MRW, High frequency of imprinted methylation errors in donated human preimplantation embryos. Scientific Reports 5:17311.
  • MacDonald WA, Sachani SS, White CR and Mann MRW, 2015, A role for chromatin topology in imprinted domain regulation. Invited Review. Biochemistry and Cell Biology 99:1-13.

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  • MacDonald WA and Mann MRW, 2014, Epigenetic regulation of genomic imprinting from germ line to preimplantation, Molecular Reproduction and Development 81:126-140, Invited Review.

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  • Market Velker BA, Denomme MM and Mann MRW, 2012. Loss of Genomic Imprinting in Mouse Embryos with Fast Rates of Preimplantation Development in Culture, Biology of Reproduction, 86:134-150.
  • Denomme MM, Zhang L and Mann MRW, 2011, Embryonic imprinting perturbations do not originate from superovulation-induced defects in DNA methylation acquisition. Fertility and Sterility 96:734-738
  • Golding MC, Magri LS, Zhang L, Lalone SA, Higgins MJ and Mann, MRW, 2011, Depletion of Kcnq1ot1non-coding RNA does not affect imprinting maintenance in stem cells, Development, 138:3667-3678.
  • Golding MC and Mann MRW, 2011, A bidirectional promoter architecture enhances lentiviral transgenesis in embryonic and extraembryonic stem cells, Gene Therapy, 18:817-826.
  • Market-Velker BA, Fernandes AD and Mann MRW, 2010, Side-by-side comparison of five commercial media systems in a mouse model system: suboptimal in vitro culture interferes with imprint maintenance, Biology of Reproduction, 83:936-950.
  • Golding MC, Zhang L and Mann MRW, 2010, Multiple epigenetic modifiers induce aggressive viral extinction in extraembryonic endoderm stem cells, Cell Stem Cell, 6:457-467.

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  • Market-Velker BA, Zhang L, Magri LS, Bonvissuto AC and Mann MRW, 2010, Dual Effects of Superovulation: Loss of maternal and paternal imprinted methylation in a dose-dependent manner, Human Molecular Genetics, 19:36-51.

For additional publications, see: https://scholar.google.com/citations?user=uTq2H0YAAAAJ&hl=en