Human laminopathies are caused by mutations in genes encoding nuclear lamina (NL) proteins. These proteins form an extensive network that lies beneath the inner nuclear membrane. A unifying disease model suggests that lost tissue homeostasis is due to a failure to maintain adult stem cells. Although NL proteins responsible for laminopathies have been identified, it remains unclear how these proteins maintain healthy stem cell populations and promote tissue homeostasis. The conserved NL family of LEM-domain (LEM-D) proteins play a critical role in building nuclear structure and the NL. LEM-D proteins bind Barrier-to-Autointegration Factor (BAF), a conserved double stranded DNA and histone binding protein. Interactions between LEM-D proteins and BAF target nuclear membranes to chromosomes during nuclear assembly after mitosis. In addition, LEM-D proteins interact with BAF to tether the genome to the nuclear periphery and establish repressed chromatin domains in non-dividing cells. We investigate the Drosophila LEM-D family, focusing on Otefin, a LEM-D protein that is required for survival of adult germline stem cells (GSCs). The otefin mutant GSCs carry structural deformities of the NL and chromatin changes that are shared with laminopathic cells. My lab discovered that these mutant GSCs die because of activation of a novel checkpoint pathway that uses two DNA damage response (DDR) kinases, ATR and Checkpoint kinase 2 (Chk2). Although otefin mutant GSCs carry DNA damage, damage accumulation depends upon Chk2, demonstrating that DNA damage results from checkpoint activation. Based on these and other data, we hypothesize that NL deformation is responsible for activation of ATR and Chk2, a prediction supported by emerging evidence that ATR is a global sensor of structural deformities of cellular components. In this proposal, two Aims are proposed.
In Aim 1, we will define the mechanism of ATR/Chk2 activation in otefin mutant GSCs.
In Aim 2, we define Chk2- dependent pathways involved in GSC death. We expect our studies will have a broad impact. Nuclear shape changes are shared features of laminopathies and premature aging syndromes. We predict that activation of the NL checkpoint might contribute to lost stem cell maintenance in these diseases.

Public Health Relevance

Human laminopathies are caused by mutations in genes encoding nuclear lamina (NL) proteins that alter nuclear structure and resulted in loss of adult stem cell maintenance. We discovered that structural deformities of the NL activate a novle checkpoint pathway that leads to stem cell death. An improved understanding of this novel NL checkpoint has the potential to provide new avenues for treatment of laminopathies.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM087341-06
Application #
10001531
Study Section
Nuclear and Cytoplasmic Structure/Function and Dynamics Study Section (NCSD)
Program Officer
Flicker, Paula F
Project Start
2010-06-01
Project End
2023-06-30
Budget Start
2020-07-01
Budget End
2021-06-30
Support Year
6
Fiscal Year
2020
Total Cost
Indirect Cost
Name
University of Iowa
Department
Biochemistry
Type
Schools of Medicine
DUNS #
062761671
City
Iowa City
State
IA
Country
United States
Zip Code
52242
Barton, Lacy J; Duan, Tingting; Ke, Wenfan et al. (2018) Nuclear lamina dysfunction triggers a germline stem cell checkpoint. Nat Commun 9:3960
Berger, Frederic; Geyer, Pamela K (2016) Editorial overview: Genome architecture and expression: Connecting genome composition and nuclear architecture with function. Curr Opin Genet Dev 37:iv-vi
Barton, Lacy J; Lovander, Kaylee E; Pinto, Belinda S et al. (2016) Drosophila male and female germline stem cell niches require the nuclear lamina protein Otefin. Dev Biol 415:75-86
Barton, Lacy J; Soshnev, Alexey A; Geyer, Pamela K (2015) Networking in the nucleus: a spotlight on LEM-domain proteins. Curr Opin Cell Biol 34:1-8
Barton, Lacy J; Wilmington, Shameika R; Martin, Melinda J et al. (2014) Unique and shared functions of nuclear lamina LEM domain proteins in Drosophila. Genetics 197:653-65
Barton, Lacy J; Pinto, Belinda S; Wallrath, Lori L et al. (2013) The Drosophila nuclear lamina protein otefin is required for germline stem cell survival. Dev Cell 25:645-54
Geyer, Pamela K; Vitalini, Michael W; Wallrath, Lori L (2011) Nuclear organization: taking a position on gene expression. Curr Opin Cell Biol 23:354-9