Role of host chromatin remodelling in Mycobacterium leprae-induced Schwann cell fate change

BACKGROUND: Mycobacterium leprae is a strictly obligate, intracellular bacterium that is a causative agent of the chronic infectious disease Leprosy. In humans, M. leprae infects Schwann cells, a type of glial cell that surrounds neurons and is responsible for the formation of the myelin sheath that encases the axon. To aid in nerve regeneration post-injury, Schwann cells have an innate plasticity ability that allows them to transition into a dedifferentiated phenotype for proliferation and axon remyelination purposes, and research has shown that Sox2, an early embryonic cell transcription factor, is reactivated in Schwann cells during this process. However, in the case of an infection by M. leprae, the bacteria hijacks this innate ability and manipulates the host cell machinery to keep the Schwann cells in this dedifferentiated state for its own bacterial advantage, with long-term infection reprogramming the infected Schwann cell into a progenitor/stem-cell like cell (pSLC) for bacterial survival and dissemination. METHOD: Externally generated ATAC-seq data sets and Sox2 ChIP-seq data on three cell states, control mouse Schwann cells (mSwCs), M. leprae infected cells (ML-mSwCs) and progenitor/stem-cell like cells (pSLCs). Data quality was checked then analysed using PCA, differential peak calling, HOMER motif enrichment, GREAT functional annotation, differential accessible regions and differential Sox2 binding sites in order to define changes to chromatin accessibility and Sox2 binding. Cultured mSwCs, along with fixed ML-mSwC models, were validated and phenotypically characterised through microscopy with additional immunofluorescence staining for Schwann cell lineage markers (p75-NTR, Oct6, Sox2, Sox10) for mSwCs. RESULTS AND DISCUSSION: ATAC-seq analysis revealed significant, genome-wide alterations in chromatin accessibility during M. leprae infection. Both shared and condition-specific remodelling events were identified, including distinct accessibility signatures associated with the reprogrammed pSLC state. The Sox2 ChIP-seq analysis revealed that Sox2 binding was distributed across the genome during infection, showing a strong correlation with regions of increase chromatin accessibility in ML-mSwCs and pSLCs. The integrated analysis pinpointed key regulatory regions where initial infection opened chromatin for Sox2 recruitment whereas in long-term infection, Sox2 binding directed the chromatin opening. The mSwC and ML-mSwC models were successfully validated, confirming Schwann cell lineage identity and infection experiment procedure. CONCLUSION: M. leprae conducts Schwann cell reprogramming in a two-phase epigenetic manipulation of the chromatin landscape and hijacks the Sox2 transcription factor, which in pSLCs adopts a de facto pioneer factor function and bindings to closed chromatin to directing opening in order to active and establish a pSLC state.

Author dc:creator

• Nowak-Garcias, Joanna

Advisors dc:contributor.advisor

• Rambukkana, Anura
• Picozzi, Kim

• Mycobacterium leprae
• Schwann cells
• Chromatin remodelling
• Sox2
• Progenitor/stem-cell like cells (pSLCs)

Language dc:language.iso

en

Identifier URI

https://doi.org/10.7488/era/7365

OAI identifier oai:identifier

oai:era.ed.ac.uk:1842/44851