Spatial and temporal expression of histone demethylase, Kdm2a, during murine molar development

Role and mechanisms of histone methylation in osteogenic/odontogenic differentiation of dental mesenchymal stem cells

Dental mesenchymal stem cells (DMSCs) are pivotal for tooth development and periodontal tissue health and play an important role in tissue engineering and regenerative medicine because of their multidirectional differentiation potential and self-renewal ability. The cellular microenvironment regulates the fate of stem cells and can be modified using various optimization techniques. These methods can influence the cellular microenvironment, activate disparate signaling pathways, and induce different biological effects. "Epigenetic regulation" refers to the process of influencing gene expression and regulating cell fate without altering DNA sequences, such as histone methylation. Histone methylation modifications regulate pivotal transcription factors governing DMSCs differentiation into osteo-/odontogenic lineages. The most important sites of histone methylation in tooth organization were found to be H3K4, H3K9, and H3K27. Histone methylation affects gene expression and regulates stem cell differentiation by maintaining a delicate balance between major trimethylation sites, generating distinct chromatin structures associated with specific downstream transcriptional states. Several crucial signaling pathways associated with osteogenic differentiation are susceptible to modulation via histone methylation modifications. A deeper understanding of the regulatory mechanisms governing histone methylation modifications in osteo-/odontogenic differentiation and immune-inflammatory responses of DMSCs will facilitate further investigation of the epigenetic regulation of histone methylation in DMSC-mediated tissue regeneration and inflammation. Here is a concise overview of the pivotal functions of epigenetic histone methylation at H3K4, H3K9, and H3K27 in the regulation of osteo-/odontogenic differentiation and renewal of DMSCs in both non-inflammatory and inflammatory microenvironments. This review summarizes the current research on these processes in the context of tissue regeneration and therapeutic interventions.

Conditional Knockout Kdm2a Reveals Crucial Involvement in Development and Function of Kidney Collecting Ducts

Lysine-specific histone demethylase 2 (Kdm2a) is essential for histone modifications involved in development and associated diseases. Nevertheless, the specific functions of Kdm2a in renal development and pathology remain largely unexplored. This study aimed to elucidate the roles of Kdm2a in sustaining the biological functions of the kidney by generating mutant mice with Kdm2a deletion using the Aqp2-cre/Loxp system. Our findings showed that Kdm2a is widely expressed across various mouse tissues, with particularly high expression in the kidney's cortex and medulla, surpassing that in other tissues. Despite no observable effects on morphology or survival following the conditional knockout of Kdm2a, there was a significant reduction in body weight and bilateral kidney weight compared to controls, most pronounced at the 5-week-old stage (p < 0.05). Post Kdm2a deletion, kidney metabolic functions were impaired, evidenced by altered levels of creatinine, urea, total cholesterol, and low-density lipoprotein. Histological examination revealed that Kdm2a-null kidneys exhibited signs of dysfunction, characterized by macrophage infiltration, fibrosis, inflammatory cell infiltration, and mild thrombosis. Further studies revealed that the expression of chemokine- and pro-inflammatory cytokine-related genes Il-6, Il-8, Tnf-a, and Il-1β was significantly increased in the kidneys of Kdm2a cKO mice compared with controls (p < 0.05). Additionally, the expression of reabsorption-related genes (Aqp-3, Aqp-5, and Aqp-8) was markedly downregulated in Kdm2a-deficient kidneys compared with controls (p < 0.05). Collectively, these findings suggest that Kdm2a is crucial for maintaining kidney function and development, partly through the suppression of inflammation and regulation of gene expression. However, the underlying molecular mechanisms of Kdm2a in kidney development warrant further investigation.

Histone-modifying enzymes: Roles in odontogenesis and beyond

OBJECTIVES

Odontogenesis, an intricate process initiated by epithelium-mesenchyme interaction, is meticulously regulated by a cascade of regulatory mechanisms. Epigenetic modifications, especially histone modification, have been found to exhibit spatiotemporal specificity during tooth development. However, the expression patterns and roles of enzymes associated with histone modifications have yet to be systematically explored in odontogenesis. This review aims to summarize the histone-modifying enzymes in odontogenesis and their regulation mechanism during tooth development and provide the potential theoretical basis for the clinical management and intervention of dental developmental diseases.

SUBJECTS AND METHODS

This study conducted a systematic search across PubMed and Web of Science databases, utilizing the keywords "odontogenesis," "histone modification," and "enzyme" for pertinent articles.

RESULTS

No doubt histone modification contributes extensively to odontogenesis regulation, and the disturbances in histone modifications can derange the odontogenesis process.

CONCLUSION

Further studies are warranted to elucidate these roles and their potential downstream effects, positioning histone modifications as a pivotal focal point for unraveling the intricacies of tooth development and regeneration.

Single-cell transcriptome analysis of the germ cells and somatic cells during mitotic quiescence stage in goats

The mitotic quiescence of prospermatogonia is the event known to occur during genesis of the male germline and is tied to the development of the spermatogenic lineage. The regulatory mechanisms and the functional importance of this process have been demonstrated in mice; however, regulation of this process in human and domestic animal is still largely unknown. In this study, we employed single-cell RNA sequencing to identify transcriptional signatures of prospermatogonia and major somatic cell types in testes of goats at E85, E105, and E125. We identified both common and specific Gene Ontology categories, transcription factor regulatory networks, and cell-cell interactions in cell types from goat testis. We also analyzed the transcriptional dynamic changes in prospermatogonia, Sertoli cells, Leydig cells, and interstitial cells. Our datasets provide a useful resource for the study of domestic animal germline development.

Histone demethylase KDM2A: Biological functions and clinical values (Review)

Histone lysine demethylation modification is a critical epigenetic modification. Lysine demethylase 2A (KDM2A), a Jumonji C domain-containing demethylase, demethylates the dimethylated H3 lysine 36 (H3K36) residue and exerts little or no activity on monomethylated and trimethylated H3K36 residues. KDM2A expression is regulated by several factors, such as microRNAs, and the phosphorylation of KDM2A also plays a vital role in its function. KDM2A mainly recognizes the unmethylated region of CpG islands and subsequently demethylates histone H3K36 residues. In addition, KDM2A recognizes and binds to phosphorylated proteins, and promotes their ubiquitination and degradation. KDM2A plays an important role in chromosome remodeling and gene transcription, and is involved in cell proliferation and differentiation, cell metabolism, heterochromosomal homeostasis and gene stability. Notably, KDM2A is crucial for tumorigenesis and progression. In the present review, the documented biological functions of KDM2A in physiological and pathological processes are comprehensively summarized.

Histone Acetylation as a Regenerative Target in the Dentine-Pulp Complex

If dental caries (or tooth decay) progresses without intervention, the infection will advance through the dentine leading to severe pulpal inflammation (irreversible pulpitis) and pulp death. The current management of irreversible pulpits is generally root-canal-treatment (RCT), a destructive, expensive, and often unnecessary procedure, as removal of the injurious stimulus alone creates an environment in which pulp regeneration may be possible. Current dental-restorative-materials stimulate repair non-specifically and have practical limitations; as a result, opportunities exist for the development of novel therapeutic strategies to regenerate the damaged dentine-pulp complex. Recently, epigenetic modification of DNA-associated histone ‘tails’ has been demonstrated to regulate the self-renewal and differentiation potential of dental-stem-cell (DSC) populations central to regenerative endodontic treatments. As a result, the activities of histone deacetylases (HDAC) are being recognised as important regulators of mineralisation in both tooth development and dental-pulp-repair processes, with HDAC-inhibition (HDACi) promoting pulp cell mineralisation in vitro and in vivo. Low concentration HDACi-application can promote de-differentiation of DSC populations and conversely, increase differentiation and accelerate mineralisation in DSC populations. Therapeutically, various HDACi solutions can release bioactive dentine-matrix-components (DMCs) from the tooth’s extracellular matrix; solubilised DMCs are rich in growth factors and can stimulate regenerative processes such as angiogenesis, neurogenesis, and mineralisation. The aim of this mini-review is to discuss the role of histone-acetylation in the regulation of DSC populations, while highlighting the importance of HDAC in tooth development and dental pulp regenerative-mineralisation processes, before considering the potential therapeutic application of HDACi in targeted biomaterials to the damaged pulp to stimulate regeneration.

Epigenetic gene regulation by histone demethylases: emerging role in oncogenesis and inflammation

Histone N-terminal tails of nucleosomes are the sites of complex regulation of gene expression through post-translational modifications. Among these modifications, histone methylation had long been associated with permanent gene inactivation until the discovery of Lys-specific demethylase (LSD1), which is responsible for dynamic gene regulation. There are more than 30 members of the Lys demethylase (KDM) family, and with exception of LSD1 and LSD2, all other KDMs possess the Jumonji C (JmjC) domain exhibiting demethylase activity and require unique cofactors, for example, Fe(II) and α-ketoglutarate. These cofactors have been targeted when devising KDM inhibitors, which may yield therapeutic benefit. KDMs and their counterpart Lys methyltransferases (KMTs) regulate multiple biological processes, including oncogenesis and inflammation. KDMs' functional interactions with retinoblastoma (Rb) and E2 factor (E2F) target promoters illustrate their regulatory role in cell cycle progression and oncogenesis. Recent findings also demonstrate the control of inflammation and immune functions by KDMs, such as KDM6B that regulates the pro-inflammatory gene expression and CD4⁺ T helper (Th) cell lineage determination. This review will highlight the mechanisms by which KDMs and KMTs regulate the target gene expression and how epigenetic mechanisms may be applied to our understanding of oral inflammation.