Histones: coming of age in Mendelian genetic disorders.

Histones hold significant interest in development and genetic disorders due to their critical roles in chromatin dynamics, influencing gene expression and genome integrity. These roles are linked to alterations of post-translational marks, which are generally concentrated in the histone tails. The machinery modifying or interpreting these marks, known as chromatin writers, erasers or readers, have been associated with many Mendelian disorders; however, it has been only recently that the histone proteins themselves have been directly implicated in Mendelian conditions. High throughput sequencing has recently identified mutations in genes encoding histone H1, H3 and H4, all causing neurodevelopmental disorders with clinical variability. Notably, many of the mutations lie outside of recognised post-translational modification-associated residues, suggesting disrupting the core functions of histones is a primary molecular mechanism underpinning these neurodevelopmental phenotypes. In this review, we describe the clinical and genetic features of histone-related disorders, focusing on the unique aspects associated with each histone gene family, while noting the commonalities which provide insight into the required roles for histone fidelity in brain development and functioning.

Evaluation of Dimensional Accuracy of Three Combinations of Polyvinyl Siloxane Impression Material: An In Vitro Study.

AIM: The aim of the study was to evaluate the dimensional accuracy of three combinations of polyvinyl siloxane impression material by double-mix single-step impression technique. MATERIALS AND METHODS: Metal master model was made according to the ADA specification no. 19; ISO 4823:2000/AMD 2007. Impressions were made using perforated custom-made metallic trays of 2 mm and 4 mm spacing, the impression materials used were putty, heavy body, regular body and light body. A total of 30 impressions were made by single-step technique and poured in die stone to obtain resultant cast. Ten impressions were made of each combination of polyvinyl siloxane (PVS). Three dimensions (interabutment distance, height and diameter) on resultant cast were measured and compared with metal master model. The results were statistically analyzed and tabulated. RESULTS: Diameter of abutment, the height of abutment and interabutment distance in each group were larger in dimensions as compared with metal master model. The dimensional discrepancies of group I, group II and group III casts when compared with the master model were significantly different from each other. The least difference was found in group I. CONCLUSION: The one-step putty-light body combination (group I) produced the most accurate stone casts compared with one-step heavy body-light body and regular body-light body combinations. CLINICAL SIGNIFICANCE: In everyday dental practice, impression making is imperative. Hence, by doing this study, we tried to find out which material combination is suitable to give us predictable and accurate results.