Table 2. A summary of the changes in H3 variant composition and H3 modification abundances with age. * ‘-‘ indicates that there is no clear pattern of change or no significant difference.

Changes in the relative abundances of H3 variants with age
	H3 variant	Change with age	Tissues	Note
	H3.3	Increase	Liver, kidney, brain, heart	Enriched in non-tumor human liver tissue
	H3.1/2	Decrease	Liver, kidney, brain, heart	Enriched in human hepatocellular carcinoma tissue
Changes in the relative abundances of H3 PTMs with age
	Modification	Change with age (total H3)	H3 variant-specific enrichment	Change with age (on H3.3)	Tissue(s)
Individual PTMs	K36me2	Increase	H3.3	Stable abundance	Liver, kidney, brain, heart
	K36me3	Increase	- *	-	Liver, brain, heart
	K27me2	Increase	-	Stable abundance	Liver, Kidney
	R26me2	Increase	-	-	Brain, heart
	K4me1	Increase	-	-	Liver, kidney, brain, heart
	R26me1	Increase	H3.1/2	Increase	Liver, brain
		Decrease	H3.1/2	Increase	Heart
	R17me2	Decrease	H3.1/2	-	Liver, kidney, brain, heart
	K27me1	Decrease	-	-	Heart
	K27me3	Decrease	H3.1/2	Stable abundance	Liver
	K9me2	Decrease	H3.1/2	Increase	Liver, kidney
	K9me3	Decrease	-	-	Kidney, brain
Binary PTMs	K27me2K36me2	Increase	H3.3	Stable abundance	Liver, kidney, heart
	K9me2K27me3	Decrease	H3.1/2	Stable abundance	Liver, heart
Combinatorial PTMs	K9me2K36me3	Increase	H3.3 (liver)	-	Liver, kidney, brain
	K4me1K9me1K14ac-K27me2K36me2	Increase	H3.1/2 (heart, brain)	-	Liver, kidney, brain, heart
	K23acK27me2K36me2	Increase	H3.3	-	Liver, Kidney
	K23acR26me2K36me2	Increase	H3.3 (brain)	Increase (brain)	Liver, kidney, heart
	K14acK18acK27me2K36me2	Increase	H3.3	-	Liver, kidney, brain
	R26me2K36me2	Increase	H3.3	Stable/increase	Liver, kidney, brain, heart
	K27me3K36me1	Increase	H3.3	Stable/increase	Liver, kidney
	K27me2K36me2	Increase	H3.3	Stable/increase	Liver, kidney, heart
	K18acK23acK27me2K36me2	Increase	H3.3 (kidney, brain)	-	Liver, heart
	K9me1K14me1K27me2	Decrease	H3.1/2	-	Liver