This proposal stems from our recent discovery that the sea lamprey (unlike other vertebrates) undergoes large- scale genome rearrangements during the normal course of its embryonic development. Programmed genome rearrangement (PGR) results in the highly reproducible elimination of ~20% of the lamprey's genome during the establishment of somatic cell lineages in the early embryo. Recent work has revealed that: 1) hundreds of gene-coding fragments are eliminated, 2) human homologs of lost genes generally possess pluripotency functions, 3) computational analysis of next-gen sequence datasets identify predicted recombination sites that mediate deletion events, which have been validated experimentally, indicating that PGR is mediated in part by recombination and 4) proteins expressed in the early embryo show sequence-specific binding to validated recombination sites. With the advent of extensive sequence resources for lamprey and methods for gene knockdown and transcript replacement, lamprey will continue to provide unique insights into the rearrangement biology of vertebrate genomes and the genetics of somatic vs. germline cell fate. As such, this research is broadly relevant to NIGMS research programs in genetics and developmental biology, particularly towards understanding the biology of genomes, chromosomes and epigenetics, vertebrate developmental genetics, stem cell biology, genetic mechanisms of DNA recombination/repair, and oncogenesis.
The specific aims of this proposal will seek to further characterize lamprey PGR at the genetic level in order to deduce its molecular mechanisms and use this information to guide functional studies of the biological causes and consequences of genome rearrangement.
Specific Aim 1 will allow us to further refine our functional models of PGR by developing a meiotic map for the lamprey genome and integrating this with existing somatic and germline genome assemblies. Analyses of this map will shed critical light on the scale, distribution, biological function, and likely mechanisms of deletion.
Specific Aim 2 dissects the biological function of genes that are deleted through PGR. Experiments performed under this aim will use morpholino mediated gene knockdowns and transcript replacement to elucidate the function of somatically deleted genes and their human homologs.
Specific Aim 3 identifies genes that mediate PGR and characterizes their molecular function. Experiments performed under this aim will use morpholino-mediated knockdown to elucidate the function of genes that bind recombination sites during PGR then use transcript replacement to test whether human homologs can partly or completely replace these functions. This will provide a direct assay for the capacity of identified human homologs to participate in somatic recombination. Critically, these approaches do not rely on pre-existing knowledge regarding the function of human genes and therefore hold great potential for the discovery of new gene functions. These studies are expected to provide unique insight into vertebrate genome biology and yield information that might not be achievable outside of the context of PGR.

Public Health Relevance

Programmed rearrangement of the lamprey genome provides a highly reproducible model for studying the causes and consequences of genome rearrangement, especially as it relates to the biology of germline stem cells. Proposed research will use the lamprey as a model for studying 1) the genetic consequences of programmed gene deletions, 2) the molecular basis of rearrangement and 3) the capacity of specific human genes to mediate rearrangement. This work will shed new light on the molecular basis of genome stability/instability and fundamental molecular properties of germline stem cells, focusing on genes with human homologs.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM104123-05
Application #
9335891
Study Section
Genetic Variation and Evolution Study Section (GVE)
Program Officer
Ainsztein, Alexandra M
Project Start
2013-09-01
Project End
2019-08-31
Budget Start
2017-09-01
Budget End
2019-08-31
Support Year
5
Fiscal Year
2017
Total Cost
Indirect Cost
Name
University of Kentucky
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
939017877
City
Lexington
State
KY
Country
United States
Zip Code
40526
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Smith, Jeramiah J (2018) Programmed DNA Elimination: Keeping Germline Genes in Their Place. Curr Biol 28:R601-R603
Smith, Jeramiah J; Timoshevskaya, Nataliya; Ye, Chengxi et al. (2018) The sea lamprey germline genome provides insights into programmed genome rearrangement and vertebrate evolution. Nat Genet 50:270-277
Timoshevskiy, Vladimir A; Lampman, Ralph T; Hess, Jon E et al. (2017) Deep ancestry of programmed genome rearrangement in lampreys. Dev Biol 429:31-34
Mukendi, Christian; Dean, Nicholas; Lala, Rushil et al. (2016) Evolution of the vertebrate claudin gene family: insights from a basal vertebrate, the sea lamprey. Int J Dev Biol 60:39-51
Timoshevskiy, Vladimir A; Herdy, Joseph R; Keinath, Melissa C et al. (2016) Cellular and Molecular Features of Developmentally Programmed Genome Rearrangement in a Vertebrate (Sea Lamprey: Petromyzon marinus). PLoS Genet 12:e1006103
Bryant, Stephanie A; Herdy, Joseph R; Amemiya, Chris T et al. (2016) Characterization of Somatically-Eliminated Genes During Development of the Sea Lamprey (Petromyzon marinus). Mol Biol Evol 33:2337-44
Smith, Jeramiah J; Keinath, Melissa C (2015) The sea lamprey meiotic map improves resolution of ancient vertebrate genome duplications. Genome Res 25:1081-90