KAT6B Genetic Variant Identified in a Short Stature Chinese Infant: A Report of Physical Growth in Clinical Spectrum of KAT6B-Related Disorders

Phenotypic Characterization of Seven Pediatric Patients Diagnosed With KAT6B-Related Disorders: Case Series and Review of the Literature

Genitopatellar syndrome (GPS) and Say-Barber-Biesecker-Young-Simpson Syndrome (SBBYSS) are clinically distinct neurodevelopmental disorders caused by monoallelic pathogenic variants in KAT6B. In some cases, GPS and SBBYSS features can overlap, determining an intermediate phenotype. In the present study, we describe seven patients, four with a clinical diagnosis of SBBYSS and three presenting with an intermediate phenotype. All patients carried de novo pathogenic variants in KAT6B that were identified by exome sequencing. Five variants were novel. We provide both molecular and clinical findings, highlighting the previously undescribed association with two additional features: partial penoscrotal transposition and hypopigmented macules. We performed a review of the literature, listing the clinical features of 152 patients described in 33 papers, with a molecularly confirmed diagnosis of KAT6B-related disorders, reporting the frequency of each clinical feature detected in patients diagnosed with SBBYSS and GPS. The present work provides new insights into the phenotype associated with "KAT6B-related disorders", expanding the spectrum of features that can lead to a clinical suspicion of these conditions, also guiding the molecular investigations.

Association of two missense mutations in the MSS51 and KAT6B genes with body weight at different ages in cows of the Yaroslavl breed

The Yaroslavl cattle is a native Russian dairy breed developed in the 19th century from the Northern Great Russian cattle, which were adapted to withstand harsh climates and poor forage conditions. Previous studies identified two breed-specific missense mutations in the MSS51 (Ala415Glu) and KAT6B (Val105Met) genes that negatively impact the body weight of the animals. This study aimed to confirm the association of these missense mutations in the MSS51 and KAT6B genes, along with the mutant haplotype containing both mutations, with live weight at various ages in the Yaroslavl breed using an expanded sample set. We genotyped 113 cows for these missense variants and analyzed their associations with live weight at birth, as well as at 6, 10, 12, 15, and 18 months in a combined sample of 143 animals, which includes earlier data. We employed linear regression and one-way ANOVA for statistical analysis. The results from linear regression indicated significant associations with live weight at 6, 12, and 18 months for the mutation in the KAT6B gene. The MSS51 gene mutation was associated with live weight at 6, 12, 15, and 18 months. Notably, the mutant haplotype was linked to live weight across all ages from 6 to 18 months. One-way ANOVA revealed significant associations of live weight with KAT6B genotypes only at 6 months. For the MSS51 gene mutation and the mutant haplotype, significant associations were found at 6, 12, 15, and 18 months. In both statistical tests, the most significant association was observed for the mutant haplotype rather than for the individual variants. These findings could be instrumental in enhancing the live weight of beef hybrids utilising the Yaroslavl cattle breed.

Genitopatellar Syndrome With a Novel Variant in the KAT6B Gene: Supporting Spectrum Delineation

Genitopatellar syndrome (GPS) and Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS) are rare genetic disorders linked to mutations in the Lysine Acetyltransferase 6B (KAT6B) gene, affecting histone acetylation regulation and developmental processes. We present a case of an African American infant with classic GPS features and a novel KAT6B gene mutation (c.4066del, p.Glu1356Argfs*23). The patient exhibited skeletal anomalies, neurologic deficits, and genitourinary abnormalities, consistent with GPS. Genetic analysis revealed a de novo heterozygous pathogenic variant, adding to the growing understanding of KAT6B-related disorders. Reviewing recent literature, we found an increased prevalence of reported cases and novel gene variants, supporting the delineation of GPS and SBBYSS. Furthermore, analysis suggests a preference range within the gene associated with GPS phenotypes, challenging the notion of a spectrum of KAT6B-related disorders. As genetic sequencing advances, continued reporting of cases will inform decisions regarding the classification of these disorders.

Novel variants in KAT6B spectrum of disorders expand our knowledge of clinical manifestations and molecular mechanisms

The phenotypic variability associated with pathogenic variants in Lysine Acetyltransferase 6B (KAT6B, a.k.a. MORF, MYST4) results in several interrelated syndromes including Say-Barber-Biesecker-Young-Simpson Syndrome and Genitopatellar Syndrome. Here we present 20 new cases representing 10 novel KAT6B variants. These patients exhibit a range of clinical phenotypes including intellectual disability, mobility and language difficulties, craniofacial dysmorphology, and skeletal anomalies. Given the range of features previously described for KAT6B-related syndromes, we have identified additional phenotypes including concern for keratoconus, sensitivity to light or noise, recurring infections, and fractures in greater numbers than previously reported. We surveyed clinicians to qualitatively assess the ways families engage with genetic counselors upon diagnosis. We found that 56% (10/18) of individuals receive diagnoses before the age of 2 years (median age = 1.96 years), making it challenging to address future complications with limited accessible information and vast phenotypic severity. We used CRISPR to introduce truncating variants into the KAT6B gene in model cell lines and performed chromatin accessibility and transcriptome sequencing to identify key dysregulated pathways. This study expands the clinical spectrum and addresses the challenges to management and genetic counseling for patients with KAT6B-related disorders.

Integrated in silico MS-based phosphoproteomics and network enrichment analysis of RASopathy proteins

Background

RASopathies are a group of syndromes showing clinical overlap caused by mutations in genes affecting the RAS-MAPK pathway. Consequent disruption on cellular signaling leads and is driven by phosphoproteome remodeling. However, we still lack a comprehensive picture of the different key players and altered downstream effectors.

Methods

An in silico interactome of RASopathy proteins was generated using pathway enrichment analysis/STRING tool, including identification of main hub proteins. We also integrated phosphoproteomic and immunoblotting studies using previous published information on RASopathy proteins and their neighbors in the context of RASopathy syndromes. Data from Phosphosite database (www.phosphosite.org) was collected in order to obtain the potential phosphosites subjected to regulation in the 27 causative RASopathy proteins. We compiled a dataset of dysregulated phosphosites in RASopathies, searched for commonalities between syndromes in harmonized data, and analyzed the role of phosphorylation in the syndromes by the identification of key players between the causative RASopathy proteins and the associated interactome.

Results

In this study, we provide a curated data set of 27 causative RASopathy genes, identify up to 511 protein–protein associations using pathway enrichment analysis/STRING tool, and identify 12 nodes as main hub proteins. We found that a large group of proteins contain tyrosine residues and their biological processes include but are not limited to the nervous system. Harmonizing published RASopathy phosphoproteomic and immunoblotting studies we identified a total of 147 phosphosites with increased phosphorylation, whereas 47 have reduced phosphorylation. The PKB signaling pathway is the most represented among the dysregulated phosphoproteins within the RASopathy proteins and their neighbors, followed by phosphoproteins implicated in the regulation of cell proliferation and the MAPK pathway.

Conclusions

This work illustrates the complex network underlying the RASopathies and the potential of phosphoproteomics for dissecting the molecular mechanisms in these syndromes. A combined study of associated genes, their interactome and phosphorylation events in RASopathies, elucidates key players and mechanisms to direct future research, diagnosis and therapeutic windows.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01934-x.