Berthold, A. | Search bioRxiv

bioRxiv2024

Epigenetic responses in Borrelia-infected Ixodes scapularis ticks: Over-expression of euchromatic histone lysine methyltransferase 2 and no change in DNA methylation

Borrelia burgdorferi, a tick-vectored spirochete bacteria best known for causing Lyme disease, has been found to induce physiological and behavioural changes in its tick vector that can increase tick fitness and its ability to transmit the bacteria. The mechanism by which this bacterium modulates these changes remains unknown. Epigenetics plays a central role in transducing external and internal microbiome environmental influences to the organism, so we investigated DNA methylation and the expression of a key histone modification enzyme in Borrelia-infected and uninfected Ixodes scapularis ticks. DNA methylation of the pericentromeric tandem repeats family, Ixodes scapularis Repeats (ISR) were assessed by methylated-DNA immunoprecipitation (MeDIP) followed by qPCR of the ISR regions. DNA methylation of the ISR sequences was found. The different repeats had different levels of DNA methylation, however, these levels were not significantly affected by the presence or absence of B. burgdorferi. The epigenetic regulator euchromatic histone lysine methyltransferase 2 (EHMT2) is recognized as having a key role in modulating the organismal stress response to infections. To assess EHMT2 transcription in Borrelia-infected and uninfected ticks, real-time reverse transcriptase PCR was performed. Uninfected ticks had over 800X lower EHMT2 expression than infected ticks. This study is among the first to identify a gene that may be involved in producing epigenetic differences in ticks depending on infection status and lays the groundwork for future epigenetic studies of I. scapularis in response to B. burgdorferi as well as other pathogens that these ticks transmit.

genetics↗

bioRxiv2022

Changes in the transcriptome and long non-coding RNAs but not the methylome occur in human cells exposed to Borrelia burgdorferi

Lyme disease, caused by infection with members of the Lyme borreliosis group of Borrelia spirochete bacteria, is increasing in frequency and distribution worldwide. This spread is driven by the expansion of ticks, vectors of these pathogens. Epigenetics may be involved in the interaction between mammalian host, tick, and bacterial pathogen, but is still poorly understood. Next-generation sequencing (NGS) allows the study of host response at the transcriptomic and methylomic scale. We tested the effect of the Borrelia burgdorferi strain B31 on a human primary cell line (HUVEC) and an immortalized cell line (HEK-293) for 72 h, a time consistent with the duration of tick feeding and host cell exposure to B. burgdorferi. RNA and DNA were extracted from cells and used for RNA-seq and Enzymatic-Methyl-seq (EM-seq). Differential expression and Reactome pathway enrichment analysis were performed. More significantly differentially expressed genes (a total of 69) were found in HUVECs compared to HEK-293 (a total of 8). Borrelia burgdorferi exposure significantly induced genes in the interferon, cytokine, and other immune response signaling in HUVECs. In HEK-293, pre-NOTCH processing in Golgi was identified as a significant pathway. Other significant genes suggest extracellular matrix binding and interaction in HEK-293. Data comparison with other transcriptomic studies of human cells exposed to B. burgdorferi revealed a small overlap in genes identified in HUVEC, but no overlap for HEK-293. No significant methylation changes were detected in HUVECs or HEK-293 exposed to B. burgdorferi. However, two long non-coding RNAs and a pseudogene were deregulated in response to B. burgdorferi in HUVEC suggesting that other epigenetic mechanisms may be initiated by infection. This is the first study examining the transcriptome and methylome of human cells exposed to B. burgdorferi for 72 h and so contributes to the description of early-stage B. burgdorferi infection at the cellular level.

molecular biology↗