Conserved functions of mouse ARX and Caenorhabditis elegans alr-1 in controlling pathways damaged in neurodevelopmental disorders (NDDs)

The X-linked ARX gene encodes the Aristaless-related homeobox protein, which is a morphogenetic transcription factor with a crucial role in cerebral development and patterning. Mutations in ARX cause a wide spectrum of X-linked neurodevelopmental disorders affecting male children, as lissencephaly with abnormal genitalia (XLAG) that is a severe cortical malformation and developmental and epileptic encephalopathy type 1 (DEE-1), a severe paediatric epilepsy characterized by recurrent and pharmaco-resistant seizures. Here we describe the conservation of multiple ARX-dependent disease-pathways among human, mouse and nematode establishing a gene-phenotype association from one organism to another. Starting from the homologous gene relationship between ARX and its murine (Arx) and worm (alr-1) counterparts, we discovered that the activity of the epigenetic ARX-KDM5C axis and the organization of microtubule cytoskeleton are conserved functions deeply damaged in XLAG mice and C. elegans mutants, respectively ablated for Arx and alr-1. Furthermore, abnormal alternative splicing (AS) repertoires in Neurexin-1, a gene encoding multiple pre-synaptic organizers implicated in synaptic remodelling, were detected in the epileptogenic brain areas and in the depolarized cortical neurons of DEE-1 Arx mice and in the alr-1(KO) animals. We also proved the ability of the epidrug Vorinostat to rescue ARX/alr-1 dependent phenotypes both in murine and C.elegans KO mutants. Given the complexity of the regulatory network controlled by ARX, mouse and worm studies offered a powerful experimental strategy that allowed us to identify unanticipated evolutionarily conserved regulatory circuits and to improve our knowledge on the pleiotropic activity of ARX, both at the cellular and tissue levels.