The Histone H3 K4me3, K27me3, and K27ac Genome-Wide Distributions Are Differently Influenced by Sex in Brain Cortexes and Gastrocnemius of the Alzheimer’s Disease PSAPP Mouse Model

X-Chromosome Dependent Differences in the Neuronal Molecular Signatures and Their Implications in Sleep Patterns

Biological factors and mechanisms that drive sex differences observed in sleep disturbances are understudied and poorly understood. The extent to which sex chromosome constitution impacts on sex differences in circadian patterns is still a knowledge void in the sleep medicine field. Here we focus on the neurological consequences of X-chromosome functional imbalances between males and females and how this molecular inequality might affect sex divergencies on sleep. In light of the X-chromosome inactivation mechanism in females and its implications in gene regulation, we describe sleep-related neuronal circuits and brain regions impacted by sex-biased modulations of the transcriptome and the epigenome. Benefited from recent large-scale genetic studies on the interplay between X-chromosome and brain function, we list clinically relevant genes that might play a role in sex differences in neuronal pathways. Those molecular signatures are put into the context of sleep and sleep-associated neurological phenotypes, aiming to identify biological mechanisms that link X-chromosome gene regulation to sex-biased human traits. These findings are a significant step forward in understanding how X-linked genes manifest in sleep-associated transcriptional networks and point to future research opportunities to address female-specific clinical manifestations and therapeutic responses.

Histone H3 Lysine 4 and 27 Trimethylation Landscape of Human Alzheimer's Disease

Background: Epigenetic remodeling is emerging as a critical process for both the onset and progression of Alzheimer’s disease (AD), the most common form of neurodegenerative dementia. However, it is not clear to what extent the distribution of histone modifications is involved in AD. Methods: To investigate histone H3 modifications in AD, we compared the genome-wide distributions of H3K4me3 and H3K27me3 in entorhinal cortices from severe sporadic AD patients and from age-matched healthy individuals of both sexes. Results: AD samples were characterized by typical average levels and distributions of the H3K4me3 and H3K27me3 signals. However, AD patients showed a lower H3K4me3 and higher H3K27me3 signal, particularly in males. Interestingly, the genomic sites found differentially trimethylated at the H3K4 between healthy and AD samples involve promoter regions of genes belonging to AD-related pathways such as glutamate receptor signaling. Conclusions: The signatures of H3K4me3 and H3K27me3 identified in AD patients validate the role of epigenetic chromatin remodeling in neurodegenerative disease and shed light on the genomic adaptive mechanisms involved in AD.

The Neuroepigenetic Landscape of Vertebrate and Invertebrate Models of Neurodegenerative Diseases

Vertebrate and invertebrate models of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, have been paramount to our understanding of the pathophysiology of these conditions; however, the brain epigenetic landscape is less well established in these disease models. DNA methylation, histone modifications, and microRNAs are among commonly studied mechanisms of epigenetic regulation. Genome-wide studies and candidate studies of specific methylation marks, histone marks, and microRNAs have demonstrated the dysregulation of these mechanisms in models of neurodegenerative diseases; however, the studies to date are scarce and inconclusive and the implications of many of these changes are still not fully understood. In this review, we summarize epigenetic changes reported to date in the brain of vertebrate and invertebrate models used to study neurodegenerative diseases, specifically diseases affecting the aging population. We also discuss caveats of epigenetic research so far and the use of disease models to understand neurodegenerative diseases, with the aim of improving the use of model organisms in this context in future studies.