A de novo heterozygous variant in KAT6A is associated with a newly named neurodevelopmental disorder Arboleda-Tham syndrome-a case report

Forebrain excitatory neuron-specific loss of Brpf1 attenuates excitatory synaptic transmission and impairs spatial and fear memory

Bromodomain and plant homeodomain (PHD) finger containing protein 1 (Brpf1) is an activator and scaffold protein of a multiunit complex that includes other components involving lysine acetyltransferase (KAT) 6A/6B/7. Brpf1, KAT6A, and KAT6B mutations were identified as the causal genes of neurodevelopmental disorders leading to intellectual disability. Our previous work revealed strong and specific expression of Brpf1 in both the postnatal and adult forebrain, especially the hippocampus, which has essential roles in learning and memory. Here, we hypothesized that Brpf1 plays critical roles in the function of forebrain excitatory neurons, and that its deficiency leads to learning and memory deficits. To test this, we knocked out Brpf1 in forebrain excitatory neurons using CaMKIIa-Cre. We found that Brpf1 deficiency reduced the frequency of miniature excitatory postsynaptic currents and downregulated the expression of genes Pcdhgb1, Slc16a7, Robo3, and Rho, which are related to neural development, synapse function, and memory, thereby damaging spatial and fear memory in mice. These findings help explain the mechanisms of intellectual impairment in patients with BRPF1 mutation.

The clinical spectrum of a nonsense mutation in KAT6A: a case report

KAT6A syndrome is an autosomal dominant genetic disorder associated with intellectual disability due to mutations in the lysine acetyltransferase 6A (KAT6A) gene. There are some differences in phenotype between KAT6A gene variants. This current case report describes a 1-month-old male infant that had a nonsense mutation in the KAT6A gene. Neither of his parents had the mutation. The proband had feeding difficulties and a physical examination revealed the following: moderate dysphagia, hypoplastic laryngeal cartilage, poor audio-visual response, poor head-up ability, no active grasping awareness, microcephaly, high arched palate and he was significantly behind other children of the same age. Echocardiography showed that the foramen ovale was not closed. He was diagnosed with atrial septal defect (ASD) when 2 years old. The patient received ASD repair at 32 months of age. Head colour Doppler ultrasonography and brain magnetic resonance imaging showed cysts in the right ventricle and choroid plexus, which returned to normal at 2 years of age. This current case demonstrates that immediate surgery should be considered in newborns with KAT6A syndrome presenting with a heart malformation. A new KAT6A syndrome phenotype is described in this current case report, which requires early diagnosis and treatment.

BRPF1-KAT6A/KAT6B Complex: Molecular Structure, Biological Function and Human Disease

The bromodomain and PHD finger–containing protein1 (BRPF1) is a member of family IV of the bromodomain-containing proteins that participate in the post-translational modification of histones. It functions in the form of a tetrameric complex with a monocytic leukemia zinc finger protein (MOZ or KAT6A), MOZ-related factor (MORF or KAT6B) or HAT bound to ORC1 (HBO1 or KAT7) and two small non-catalytic proteins, the inhibitor of growth 5 (ING5) or the paralog ING4 and MYST/Esa1-associated factor 6 (MEAF6). Mounting studies have demonstrated that all the four core subunits play crucial roles in different biological processes across diverse species, such as embryonic development, forebrain development, skeletal patterning and hematopoiesis. BRPF1, KAT6A and KAT6B mutations were identified as the cause of neurodevelopmental disorders, leukemia, medulloblastoma and other types of cancer, with germline mutations associated with neurodevelopmental disorders displaying intellectual disability, and somatic variants associated with leukemia, medulloblastoma and other cancers. In this paper, we depict the molecular structures and biological functions of the BRPF1-KAT6A/KAT6B complex, summarize the variants of the complex related to neurodevelopmental disorders and cancers and discuss future research directions and therapeutic potentials.

Identification of a novel KAT6A variant in an infant presenting with facial dysmorphism and developmental delay: a case report and literature review

Background

Arboleda-Tham syndrome (ARTHS), caused by a pathogenic variant of KAT6A, is an autosomal dominant inherited genetic disorder characterized by various degrees of developmental delay, dysmorphic facial appearance, cardiac anomalies, and gastrointestinal problems.

Case presentation

A baby presented multiple facial deformities including a high arched and cleft palate, with philtral ridge and vermilion indentation, a prominent nasal bridge, a thin upper lip, low-set ears, an epicanthal fold, and cardiac malformations. Whole exome sequencing (WES) revealed a heterozygous nonsense mutation in exon 8 of the KAT6A gene (c.1312C>T, p.[Arg438*]) at 2 months of age. After a diagnosis of ARTHS, an expressive language delay was observed during serial assessments of developmental milestones.

Conclusions

In this study, we describe a case with a novel KAT6A variant first identified in Korea. This case broadens the scope of clinical features of ARTHS and emphasizes that WES is necessary for early diagnosis in patients with dysmorphic facial appearances, developmental delay, and other congenital abnormalities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01148-x.