Tomás Oliveira-Madureira

Divergent Protein Kinase Domain 2B (DIPK2B) is a conserved kinase-like protein of the FAM69 family that has been associated with autism spectrum disorder and X-linked intellectual disability. However, its biological function has not yet been described. We previously identified dipk2b as a marker of hemangioblasts and hemogenic endothelial populations in the chick embryo, suggesting a potential role in hematopoietic development. Here, we characterized the expression pattern of dipk2b and the effects of its loss of function during zebrafish development. In line with our observations in the chick embryo, zebrafish dipk2b is expressed in the hematopoietic regions of the developing embryo, including the lateral plate mesoderm, dorsal aorta, and caudal hematopoietic tissue. Using two independent CRISPR/Cas9 loss-of-function alleles, we show that dipk2b homozygous mutant embryos have significantly fewer primitive macrophages than wild-type controls. In addition, dipk2b mutants exhibit a persistent decrease in microglial cell numbers at larval stages, consistent with the reduced macrophage population that gives rise to microglia. Together, these findings uncover a role for Dipk2b in promoting the development of primitive macrophages and microglia from early hematopoietic progenitors. Given the emerging role of microglial dysfunction in neurodevelopmental disorders, our results suggest that DIPK2B deficiency may contribute to autism spectrum disorder and X-linked intellectual disability by impairing microglia development.

The SCN2A gene encodes the alpha subunit of a voltage-gated sodium channel which is necessary for creating and propagating action potentials in neurons. Impairment of the Na _v 1.2 function is associated with neurodevelopmental disorders such as Developmental and Epileptic Encephalopathy, Self-limited Neonatal/Infantile Seizures, and Autism Spectrum Disorder. In this study, we used orthologous sequence comparisons, as well as disease associated variants to analyze their location in the structure of Na _v 1.2, with the aim of understanding the impact of genetic variants in the structure of this protein at an evolutionary and clinical level. Our analyses reveal different spatial distribution of interspecific variation where different residues locate preferentially in the first cytoplasmic linker, while disease-associated variants tend to cluster in the voltage-sensing segments of the protein domains. Altogether, these discoveries point to structurally important segments in the Na _v 1.2 structure that have been conserved through evolution due to their role in maintaining the function of the channel.

A key factor influencing the structural and functional impact of amino acid substitutions in disease‐associated genes involves the background genetic variation. Epistatic interactions between co‐evolving positions in the same gene result in the interdependence of each site with its interacting partners. Evidence supporting the role of these interactions is exemplified in the occurrence of human disease‐associated alleles in the genome of non‐human species. Although several explanations can contribute to this phenomenon, one possibility is the occurrence of compensatory interacting sites that can fully, or partially, restore the pathogenic effect, contributing to the maintenance of protein structure and proper function. These interactions create genetic contexts that are revisited here through the analysis of literature data for specific proteins, with a particular focus on proteins involved in inborn errors of metabolism.