SMC5/6 is required for replication fork stability and faithful chromosome segregation during neurogenesis
- Johns Hopkins Bloomberg School of Public Health, United States
Abstract
Mutations of SMC5/6 components cause developmental defects, including primary microcephaly. To model neurodevelopmental defects, we engineered a mouse wherein Smc5 is conditionally knocked out (cKO) in the developing neocortex. Smc5 cKO mice exhibited neurodevelopmental defects due to neural progenitor cell (NPC) apoptosis, which led to reduction in cortical layer neurons. Smc5 cKO NPCs formed DNA bridges during mitosis and underwent chromosome missegregation. SMC5/6 depletion triggers a CHEK2-p53 DNA damage response, as concomitant deletion of the Trp53 tumor suppressor or Chek2 DNA damage checkpoint kinase rescued Smc5 cKO neurodevelopmental defects. Further assessment using Smc5 cKO and auxin-inducible degron systems demonstrated that absence of SMC5/6 leads to DNA replication stress at late-replicating regions such as pericentromeric heterochromatin regions. In summary, SMC5/6 is important for completion of DNA replication prior to entering mitosis, which ensures accurate chromosome segregation. Thus, SMC5/6 functions are critical in highly proliferative stem cells during organism development.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting files.
Article and author information
Author details
Nathaniel P Rogers
Marina V Pryzhkova
Funding
National Institute of General Medical Sciences (R01GM11755)
- Philip W Jordan
National Institutes of Health (R21OD023720)
- Philip W Jordan
National Institute of Neurological Disorders and Stroke (R03NS106486)
- Philip W Jordan
Johns Hopkins University (Catalyst Award)
- Philip W Jordan
National Cancer Institute (T32CA009110)
- Michelle J Xu
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: All mice were bred at Johns Hopkins University (JHU, Baltimore, MD) in accordance with the National Institutes of Health and U.S. Department of Agriculture criteria and protocols for their care and use were approved by the Institutional Animal Care and Use Committees (IACUC) of JHU (Protocol number = MO19H08).
Reviewing Editor
- Kevin Struhl, Harvard Medical School, United States
Publication history
- Received: July 16, 2020
- Accepted: November 16, 2020
- Accepted Manuscript published: November 17, 2020 (version 1)
- Version of Record published: December 8, 2020 (version 2)
Copyright
© 2020, Atkins et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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SMC5/6 is required for replication fork stability and faithful chromosome segregation during neurogenesis
eLife 9:e61171.
https://doi.org/10.7554/eLife.61171
Further reading
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- Chromosomes and Gene Expression
- Neuroscience
Sensory feedback is required for the stable execution of learned motor skills, and its loss can severely disrupt motor performance. The neural mechanisms that mediate sensorimotor stability have been extensively studied at systems and physiological levels, yet relatively little is known about how disruptions to sensory input alter the molecular properties of associated motor systems. Songbird courtship song, a model for skilled behavior, is a learned and highly structured vocalization that is destabilized following deafening. Here, we sought to determine how the loss of auditory feedback modifies gene expression and its coordination across the birdsong sensorimotor circuit. To facilitate this system-wide analysis of transcriptional responses, we developed a gene expression profiling approach that enables the construction of hundreds of spatially-defined RNA-sequencing libraries. Using this method, we found that deafening preferentially alters gene expression across birdsong neural circuitry relative to surrounding areas, particularly in premotor and striatal regions. Genes with altered expression are associated with synaptic transmission, neuronal spines, and neuromodulation and show a bias toward expression in glutamatergic neurons and Pvalb/Sst-class GABAergic interneurons. We also found that connected song regions exhibit correlations in gene expression that were reduced in deafened birds relative to hearing birds, suggesting that song destabilization alters the inter-region coordination of transcriptional states. Finally, lesioning LMAN, a forebrain afferent of RA required for deafening-induced song plasticity, had the largest effect on groups of genes that were also most affected by deafening. Combined, this integrated transcriptomics analysis demonstrates that the loss of peripheral sensory input drives a distributed gene expression response throughout associated sensorimotor neural circuitry and identifies specific candidate molecular and cellular mechanisms that support the stability and plasticity of learned motor skills.
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- Chromosomes and Gene Expression
In songbirds, deafening leads to changes in gene expression which have now been mapped at the single-cell level across the neural circuit involved in song production.
