H3K4 methyl marks landscape during Caenorhabditis elegans embryogenesis and their implication in lifespan regulation

Abstract

How long organisms may live is not determined by genetic code alone. Recent findings reveal that components of MLL/SET/COMPASS complex, ASH-2, WDR-5 and SET-2, regulate H3K4 methylation levels on genome and limit how long nematode Caenorhabditis elegans may live. This suggest that histone modifications could also determine life expectancy. We conducted lifespan assay and transgenerational study to investigate if another core component of the COMPASS complex, RBBP-5, is also a regulator of lifespan. We mapped H3K4me1/me2/me3 attributed to WDR-5 and RBBP-5 and then find any correlation between changes in gene expression and altered methylation levels in wdr-5(-) and rbbp-5(-). Our study reveals that in absence of RBBP-5, lifespan is shortened. The H3K4 methylation levels also reduce as the animal aged. Moreover, the rbbp-5(-) mutant descendants from wild type ancestors inherit normal lifespan for up to three generations, before gaining back short lifespan. The transgenerational inheritance is specific for lifespan regulation and does not affect brood size (Chapter 3). Mapping of H3K4me1/me2/me3 using rbbp-5(-) C. elegans embryos reveals severe depletion of all states throughout the genome. In contrast, in absence of WDR-5, we observe global increase in H3K4me1, decrease in H3K4me3 and excessive accumulation of H3K4me2 at chromosome X. Correlation between RNA-seq and ChIP-seq data using wdr-5(-) and rbbp-5(-) embryos uncover more genes being upregulated than downregulated, despite depletion in H3K4 methylation levels in both mutants. Absence of WDR-5 also causes higher incidence of male, all of which have abnormal tail morphology (Chapter 4). While exploring the landscape of H3K4me1/me2/me3, we developed new technique for the amplification of massive amount of C. elegans on solid media (Chapter 5). In conclusion, the work presented in this thesis shows that H3K4 methylation attributed by RBBP prevents lifespan shortening. The work also shows WDR-5 as a key player in promoting the acquisition of H3K4me3 and in preventing excessive accumulation of H3K4me2 at chromosome X.

Date of Award	1 Aug 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Andrew Sharrocks (Supervisor) & Gino Poulin (Supervisor)