Around 1% of children worldwide are born with a neurodevelopmental disease (NDDs). Amongst those, we count, for example autism spectrum disorder (ASD), intellectual disability and certain forms of epilepsy. Despite the relatively frequent occurrence of these NDDs, their ontology is not very well understood. Part of the reason for this, is the complexity of NDDs at the genetic level. While a number of diseases classically occurs through the mutation of a single gene, NDDs in which only a single gene is mutated, are rare. Instead, NDDs are often the consequence of an accumulation of mutations in various genes. This genetic complexity is often paired with a similar clinical manifestation, but varying severity in patients. Add onto that the incomplete understanding of the functioning of the human brain and it is clear why our comprehension of NDDs remains at surface-level.
Given this context, a lot of effort has been put into discovering common processes that are affected in NDDs. For ASD, for example, research has shown that affected genes converge on a limited number of pathways that govern brain function, such as metabolism, RNA biology and epigenetics (modifications at the DNA level without changing the order of the DNA sequence). All these processes, in turn, converge on the correct functioning of the neuronal structure that is responsible for the connectivity in the brain: the synapse. Despite, this global view, however, detailed knowledge about how these processes interact during neurodevelopment is lacking.
The current project is framed within this knowledge gap. We decided to study the interaction between two genes called Nuak1 and Son. Nuak1 is a gene encoding a kinase of the AMP kinase-related family of kinases which govern cell growth and metabolism and in the context of neurodevelopment also cell polarity. Nuak1 has been studied for a long time in the lab and we showed that Nuak1 contributes to the metabolic activity of neurons through regulation of mitochondrial activity. The loss of function of Nuak1 leads to behavioural abnormalities in a mouse model, contributing to Nuak1 being classified as a category 2 ASD-related gene by the Simons Foundation.
On the other hand, we decided to study Son, a gene that encodes a scaffolding protein of the nuclear speckles. Nuclear speckles are structures in the nucleus of the cell that are important for RNA biology including transcription, mRNA splicing and export of RNA from the nucleus. Son, like Nuak1, equally is a syndromic ASD-related gene in category 1 according the Simons Foundation. In addition, mutations in the Son gene are associated with a broad-spectrum developmental syndrome called Zhu-Tokita-Takenouchi-Kim (ZTTK) syndrome. The clinical manifestations of the syndrome are varied but include in the majority of cases intellectual disability and brain malformations, in conjunction with epilepsy and ASD.
The interest of this project is to study the interaction and interplay between those two genes that represent two different biological processes involved in the ontology of NDDs, and especially ASD. The objective of this study is thus to understand: 1. how Nuak1 and Son interact at the cellular level in detail, 2. how RNA biology and metabolism affect each other in a neuronal context 3. how their interaction can explain the involvement of both in the ontology of NDDs.
