Sometimes, this symptom can disappear with age and following early rehabilitation [39]. other parts of this review. International consensus diagnostic criteria for KS were established in 2019. These aimed to facilitate the process of diagnosing KS. It was concluded that a definite diagnosis of KS can be made in patients of any age with a history of infantile hypotonia, developmental delay and at least one of the major criteria: A pathogenic or a likely pathogenic variant in or variants underlie Kabuki syndrome [3]. is also known as MLL2 (the latter name is considered outdated) [6]. Two years later, Lederer et al. described three patients with deletions encompassing the gene on the X-chromosome. They claimed that would manifest itself in the affected individuals [7]. Miyake et al. then demonstrated that the point variants PF-3635659 in also cause KS. They examined 32 patients with KS diagnosed clinically who were negative for variants. Two patients had nonsense variants while one had a three base-pair deletion in [8]. UTY is a homologue of on the Y-chromosome. In the past, UTY was thought to have lost its demethylase activity and to be nonfunctional; however, knockout-mice models suggest that the gene is expressed in a cell. Female mice with homozygous deletion do not survive, but hemizygous males do, as this is thought to be due to the UTY PF-3635659 gene function. This suggests that UTY does play a role similar to in metabolism and development [9]. The protein is a histone (H3) lysine methyltransferase protein, while acts as a histone demethylase. Both proteins have complementary functions. is responsible for cell-type specific gene expression during differentiation. It functions to trimethylate histone-3-lysine-4, opening the chromatin and activating homeobox and NESTIN genes during cell differentiation. demethylates histone-3-lysine-27, closing the chromatin. Both genes affect the opening of chromatin and promote gene expression. Dosage GTF2F2 sensitivity may be important in Kabuki syndrome. The switch between open and closed chromatin affects the access of transcriptional machinery to target genes, which may lead to the development of the disease [10]. Pathogenic/likely pathogenic variants seen in KS tend to reduce decreases mediator and polymerase levels, which leads to defects in cell-type specific gene expression and cell differentiation. was identified as a mono and di-methyltransferase, which is essential for enhancer activation during cell differentiation [6]. Drug-induced balance-restoration that promotes open-chromatin (for example, with histone-deacetylase inhibitors) may be considered as a novel KS treatment. Drug administration in mice normalized structural and functional deficits in dentate gyrus function after H3K4 trimethylation [10]. In humans, the gene is located on chromosome 12. It is over 19 kilobase pairs in length and contains 54 exons. codes for the enhancer histone-3-lysine-4 methyltransferase protein, one of six KMT proteins working as part of a chromatin modifier protein complex. Enhancers aid in gene expression regulation. They are often bound PF-3635659 to transcription factors. selectively binds to specific regions during various cell differentiation stages, activating gene expression depending on the differentiation stage [12]. A recently published Xenopus frog model provides evidence that loss-of-function variants inhibit neural crest development, suggesting that KS be considered a neurocristopathy. The expression of in the neural crest during pre-migratory as well as migratory stages was found. may be required for neural crest cell differentiation and consequent migration [13]. Cell-autonomous proliferation and cell cycle defects along with early neural stem cell progenitor maturation in an in vitro and mouse model were confirmed. function suppresses oxygen-responsive gene programs crucial for neural progenitor maintenance, ultimately leading to precocious neuronal differentiation [14]. A recent zebrafish model aimed to analyze the role of and in the development of tissue abnormalities, including craniofacial, heart and brain deformities. Variants in both and lead to improper cell differentiation, ultimately causing a characteristic dysmorphism and developmental delay [15]. A fluorescence in situ hybridization and Whole Genome Sequencing study was performed, analyzing a female KS patient with a known variant and a phenotype including hypotonia, developmental delay, short stature, microcephaly, seizures, facial dysmorphism and cleft palate. expression is PF-3635659 significantly reduced in neural crest cells, leading to delayed neural development. The dosage sensitivity of is associated with characteristic Kabuki syndrome dysmorphism. and proteins regulate the differentiation of mesenchymal cell lineages: myoblasts and osteoblasts. Mouse models have shown that lysine demethylase plays a crucial role in regulating mesenchymal lineage cell.