Growth factor-dependent phosphorylation of Gαi shapes canonical signaling by G protein-coupled receptors.

A long-standing question in the field of signal transduction is how distinct signaling pathways interact with each other to control cell behavior. Growth factor receptors and G protein-coupled receptors (GPCRs) are the two major signaling hubs in eukaryotes. Given that the mechanisms by which they signal independently have been extensively characterized, we investigated how they may cross-talk with each other. Using linear ion trap mass spectrometry and cell-based biophysical, biochemical, and phenotypic assays, we found at least three distinct ways in which epidermal growth factor affected canonical G protein signaling by the Gi-coupled GPCR CXCR4 through the phosphorylation of Gαi. Phosphomimicking mutations in two residues in the αE helix of Gαi (tyrosine-154/tyrosine-155) suppressed agonist-induced Gαi activation while promoting constitutive Gßγ signaling. Phosphomimicking mutations in the P loop (serine-44, serine-47, and threonine-48) suppressed Gi activation entirely, thus completely segregating growth factor and GPCR pathways. As expected, most of the phosphorylation events appeared to affect intrinsic properties of Gαi proteins, including conformational stability, nucleotide binding, and the ability to associate with and to release Gßγ. However, one phosphomimicking mutation, targeting the carboxyl-terminal residue tyrosine-320, promoted mislocalization of Gαi from the plasma membrane, a previously uncharacterized mechanism of suppressing GPCR signaling through G protein subcellular compartmentalization. Together, these findings elucidate not only how growth factor and chemokine signals cross-talk through the phosphorylation-dependent modulation of Gαi but also how such cross-talk may generate signal diversity.

Structural and dynamic insights into the activation of the µ-opioid receptor by an allosteric modulator.

G-protein-coupled receptors (GPCRs) play pivotal roles in various physiological processes. These receptors are activated to different extents by diverse orthosteric ligands and allosteric modulators. However, the mechanisms underlying these variations in signaling activity by allosteric modulators remain largely elusive. Here, we determine the three-dimensional structure of the µ-opioid receptor (MOR), a class A GPCR, in complex with the Gi protein and an allosteric modulator, BMS-986122, using cryogenic electron microscopy. Our results reveal that BMS-986122 binding induces changes in the map densities corresponding to R1673.50 and Y2545.58, key residues in the structural motifs conserved among class A GPCRs. Nuclear magnetic resonance analyses of MOR in the absence of the Gi protein reveal that BMS-986122 binding enhances the formation of the interaction between R1673.50 and Y2545.58, thus stabilizing the fully-activated conformation, where the intracellular half of TM6 is outward-shifted to allow for interaction with the Gi protein. These findings illuminate that allosteric modulators like BMS-986122 can potentiate receptor activation through alterations in the conformational dynamics in the core region of GPCRs. Together, our results demonstrate the regulatory mechanisms of GPCRs, providing insights into the rational development of therapeutics targeting GPCRs.

Inhibition of adenylyl cyclase by GTPase-deficient Gαi is mechanistically different from that mediated by receptor-activated Gαi.

Signal transduction through G protein-coupled receptors (GPCRs) has been a major focus in cell biology for decades. Numerous disorders are associated with GPCRs that utilize Gi proteins to inhibit adenylyl cyclase (AC) as well as regulate other effectors. Several early studies have successfully defined the AC-interacting domains of several members of Gαi by measuring the loss of activity upon homologous replacements of putative regions of constitutive active Gαi mutants. However, whether such findings can indeed be translated into the context of a receptor-activated Gαi have not been rigorously verified. To address this issue, an array of known and new chimeric mutations was introduced into GTPase-deficient Q204L (QL) and R178C (RC) mutants of Gαi1, followed by examinations on their ability to inhibit AC. Surprisingly, most chimeras failed to abolish the constitutive activity brought on by the QL mutation, while some were able to eliminate the inhibitory activity of RC mutants. Receptor-mediated inhibition of AC was similarly observed in the same chimeric constructs harbouring the pertussis toxin (PTX)-resistant C351I mutation. Moreover, RC-bearing loss-of-function chimeras appeared to be hyper-deactivated by endogenous RGS protein. Molecular docking revealed a potential interaction between AC and the α3/ß5 loop of Gαi1. Subsequent cAMP assays support a cooperative action of the α3/ß5 loop, the α4 helix, and the α4/ß6 loop in mediating AC inhibition by Gαi1-i3. Our results unveiled a notable functional divergence between constitutively active mutants and receptor-activated Gαi1 to inhibit AC, and identified a previously unknown AC-interacting domain of Gαi subunits. These results collectively provide valuable insights on the mechanism of AC inhibition in the cellular environment.

Inhibitory G proteins play multiple roles to polarize sensory hair cell morphogenesis.

Inhibitory G alpha (GNAI or Gαi) proteins are critical for the polarized morphogenesis of sensory hair cells and for hearing. The extent and nature of their actual contributions remains unclear, however, as previous studies did not investigate all GNAI proteins and included non-physiological approaches. Pertussis toxin can downregulate functionally redundant GNAI1, GNAI2, GNAI3, and GNAO proteins, but may also induce unrelated defects. Here, we directly and systematically determine the role(s) of each individual GNAI protein in mouse auditory hair cells. GNAI2 and GNAI3 are similarly polarized at the hair cell apex with their binding partner G protein signaling modulator 2 (GPSM2), whereas GNAI1 and GNAO are not detected. In Gnai3 mutants, GNAI2 progressively fails to fully occupy the sub-cellular compartments where GNAI3 is missing. In contrast, GNAI3 can fully compensate for the loss of GNAI2 and is essential for hair bundle morphogenesis and auditory function. Simultaneous inactivation of Gnai2 and Gnai3 recapitulates for the first time two distinct types of defects only observed so far with pertussis toxin: (1) a delay or failure of the basal body to migrate off-center in prospective hair cells, and (2) a reversal in the orientation of some hair cell types. We conclude that GNAI proteins are critical for hair cells to break planar symmetry and to orient properly before GNAI2/3 regulate hair bundle morphogenesis with GPSM2.

Molecular Dynamic Simulations to Determine Individualized Therapy: Tetrabenazine for the GNAO1 Encephalopathy E246K Variant.

INTRODUCTION: GNAO1 encephalopathy is characterized by severe hypotonia, psychomotor retardation, epilepsy, and movement disorders. Genetic variations in GNAO1 have been linked to neurological symptoms including movement disorders like dystonia. The correlation between the E246K mutation in the Gα subunit and aberrant signal transduction of G proteins has been established but no data are reported regarding the efficacy of medical treatment with tetrabenazine. METHODS: Molecular modeling studies were performed to elucidate the molecular mechanisms underlying this mutation. We developed drug efficacy models using molecular dynamic simulations that replicated the behavior of wild-type and mutated proteins in the presence or absence of ligands. RESULTS AND DISCUSSION: We demonstrated that the absence of the mutation leads to normal signal transduction upon receptor activation by the endogenous ligand, but not in the presence of tetrabenazine. In contrast, the presence of the mutation resulted in abnormal signal transduction in the presence of the endogenous ligand, which was corrected by the drug tetrabenazine. Tetrabenazine was identified as a promising therapeutic option for pediatric patients suffering from encephalopathy due to an E246K mutation in the GNAO1 gene validated through molecular dynamics. This is a potential first example of the use of this technique in a rare neurological pediatric disease.

Stabilization of interdomain interactions in G protein α subunits as a determinant of Gαi subtype signaling specificity.

Highly homologous members of the Gαi family, Gαi1-3, have distinct tissue distributions and physiological functions, yet their biochemical and functional properties are very similar. We recently identified PDZ-RhoGEF (PRG) as a novel Gαi1 effector that is poorly activated by Gαi2. In a proteomic proximity labeling screen we observed a strong preference for Gαi1 relative to Gαi2 with respect to engagement of a broad range of potential targets. We investigated the mechanistic basis for this selectivity using PRG as a representative target. Substitution of either the helical domain (HD) from Gαi1 into Gαi2 or substitution of a single amino acid, A230 in Gαi2 with the corresponding D in Gαi1, largely rescues PRG activation and interactions with other potential Gαi targets. Molecular dynamics simulations combined with Bayesian network models revealed that in the GTP bound state, separation at the HD-Ras-like domain (RLD) interface is more pronounced in Gαi2 than Gαi1. Mutation of A230 to D in Gαi2 stabilizes HD-RLD interactions via ionic interactions with R145 in the HD which in turn modify the conformation of Switch III. These data support a model where D229 in Gαi1 interacts with R144 and stabilizes a network of interactions between HD and RLD to promote protein target recognition. The corresponding A230 in Gαi2 is unable to stabilize this network leading to an overall lower efficacy with respect to target interactions. This study reveals distinct mechanistic properties that could underly differential biological and physiological consequences of activation of Gαi1 or Gαi2 by G protein-coupled receptors.

GNAO1 Mutations Affecting the N-Terminal α-Helix of Gαo Lead to Parkinsonism.

BACKGROUND: Patients carrying pathogenic variants in GNAO1 present a phenotypic spectrum ranging from severe early-onset epileptic encephalopathy and developmental delay to mild adolescent/adult-onset dystonia. Genotype-phenotype correlation and molecular mechanisms underlying the disease remain understudied. METHODS: We analyzed the clinical course of a child carrying the novel GNAO1 mutation c.38T>C;p.Leu13Pro, and structural, biochemical, and cellular properties of the corresponding mutant Gαo-GNAO1-encoded protein-alongside the related mutation c.68T>C;p.Leu23Pro. RESULTS: The main clinical feature was parkinsonism with bradykinesia and rigidity, unlike the hyperkinetic movement disorder commonly associated with GNAO1 mutations. The Leu ➔ Pro substitutions have no impact on enzymatic activity or overall folding of Gαo but uniquely destabilize the N-terminal α-helix, blocking formation of the heterotrimeric G-protein and disabling activation by G-protein-coupled receptors. CONCLUSIONS: Our study defines a parkinsonism phenotype within the spectrum of GNAO1 disorders and suggests a genotype-phenotype correlation by GNAO1 mutations targeting the N-terminal α-helix of Gαo. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

RNA Interference Effectors Selectively Silence the Pathogenic Variant GNAO1 c.607 G > A In Vitro.

RNA interference (RNAi)-based therapeutics hold the potential for dominant genetic disorders, enabling sequence-specific inhibition of pathogenic gene products. We aimed to direct RNAi for the selective suppression of the heterozygous GNAO1 c.607 G > A variant causing GNAO1 encephalopathy. By screening short interfering RNA (siRNA), we showed that GNAO1 c.607G>A is a druggable target for RNAi. The si1488 candidate achieved at least twofold allelic discrimination and downregulated mutant protein to 35%. We created vectorized RNAi by incorporating the si1488 sequence into the short hairpin RNA (shRNA) in the adeno-associated virus (AAV) vector. The shRNA stem and loop were modified to improve the transcription, processing, and guide strand selection. All tested shRNA constructs demonstrated selectivity toward mutant GNAO1, while tweaking hairpin structure only marginally affected the silencing efficiency. The selectivity of shRNA-mediated silencing was confirmed in the context of AAV vector transduction. To conclude, RNAi effectors ranging from siRNA to AAV-RNAi achieve suppression of the pathogenic GNAO1 c.607G>A and discriminate alleles by the single-nucleotide substitution. For gene therapy development, it is crucial to demonstrate the benefit of these RNAi effectors in patient-specific neurons and animal models of the GNAO1 encephalopathy.

GPCR-G protein selectivity revealed by structural pharmacology.

Receptor-G protein promiscuity is frequently observed in class A G protein-coupled receptors (GPCRs). In particular, GPCRs can couple with G proteins from different families (Gαs, Gαq/11, Gαi/o, and Gα12/13) or the same family subtypes. The molecular basis underlying the selectivity/promiscuity is not fully revealed. We recently reported the structures of kappa opioid receptor (KOR) in complex with the Gi/o family subtypes [Gαi1, GαoA, Gαz, and Gustducin (Gαg)] determined by cryo-electron microscopy (cryo-EM). The structural analysis, in combination with pharmacological studies, provides insights into Gi/o subtype selectivity. Given the conserved sequence identity and activation mechanism between different G protein families, the findings within Gi/o subtypes could be likely extended to other families. Understanding the KOR-Gi/o or GPCR-G protein selectivity will facilitate the development of more precise therapeutics targeting a specific G protein subtype.

Overexpressed Gαi1 exerts pro-tumorigenic activity in nasopharyngeal carcinoma.

The current study tested the expression and potential functions of Gαi1 in nasopharyngeal carcinoma (NPC). The Cancer Genome Atlas (TCGA) database results demonstrate that Gαi1 transcripts' number in NPC tissues is significantly higher than that in the normal nasal epithelial tissues. Its overexpression correlates with poor survival in certain NPC patients. Moreover, Gαi1 is significantly upregulated in NPC tissues of local primary patients and in different primary human NPC cells. Whereas its expression is relatively low in cancer-surrounding normal tissues and in primary nasal epithelial cells. Genetic silencing (via shRNA strategy) or knockout (via CRISPR-sgRNA method) of Gαi1 substantially suppressed viability, proliferation, cell cycle progression, and migration in primary NPC cells, causing significant caspase-apoptosis activation. Contrarily, ectopic Gαi1 expression exerted pro-tumorigenic activity and strengthened cell proliferation and migration in primary NPC cells. Gαi1 is important for Akt-mTOR activation in NPC cells. Akt-S6K phosphorylation was downregulated after Gαi1 shRNA or KO in primary NPC cells, but strengthened following Gαi1 overexpression. In Gαi1-silenced primary NPC cells, a S473D constitutively-active mutant Akt1 (caAkt1) restored Akt-S6K phosphorylation and ameliorated Gαi1 shRNA-induced proliferation inhibition, migration reduction and apoptosis. Bioinformatics analyses proposed zinc finger protein 384 (ZNF384) as a potential transcription factor of Gαi1. In primary NPC cells, ZNF384 shRNA or knockout (via CRISPR-sgRNA method) decreased Gαi1 mRNA and protein expression, whereas ZNF384 overexpression upregulated it. Importantly, there was an increased binding between ZNF384 protein and the Gαi1 promoter in human NPC tissues and different NPC cells. In vivo studies showed that intratumoral injection of Gαi1-shRNA-expressing adeno-associated virus (AAV) impeded subcutaneous NPC xenograft growth in nude mice. Gαi1 downregulation, Akt-mTOR inactivation, and apoptosis induction were detected in Gαi1-silenced NPC xenograft tissues. Gαi1 KO also effectively inhibited the growth of NPC xenografts in nude mice. Together, overexpressed Gαi1 exerts pro-tumorigenic activity in NPC possibly by promoting Akt-mTOR activation.

Molecular annotation of G protein variants in a neurological disorder.

Heterotrimeric G proteins transduce extracellular chemical messages to generate appropriate intracellular responses. Point mutations in GNAO1, encoding the G protein αo subunit, have been implicated in a pathogenic condition characterized by seizures, movement disorders, intellectual disability, and developmental delay (GNAO1 disorder). However, the effects of these mutations on G protein structure and function are unclear. Here, we report the effects of 55 mutations on Gαo conformation, thermostability, nucleotide binding, and hydrolysis, as well as interaction with Gßγ subunits, receptors, and effectors. Our effort reveals four functionally distinct groups of mutants, including one group that sequesters receptors and another that sequesters Gßγ, both acting in a genetically dominant manner. These findings provide a more comprehensive understanding of disease-relevant mutations and reveal that GNAO1 disorder is likely composed of multiple mechanistically distinct disorders that will likely require multiple therapeutic strategies.

Clinical Cases and the Molecular Profiling of a Novel Childhood Encephalopathy-Causing GNAO1 Mutation P170R.

De novo mutations in GNAO1, the gene encoding the major neuronal G protein Gαo, cause a spectrum of pediatric encephalopathies with seizures, motor dysfunction, and developmental delay. Of the >80 distinct missense pathogenic variants, many appear to uniformly destabilize the guanine nucleotide handling of the mutant protein, speeding up GTP uptake and deactivating GTP hydrolysis. Zinc supplementation emerges as a promising treatment option for this disease, as Zn2+ ions reactivate the GTP hydrolysis on the mutant Gαo and restore cellular interactions for some of the mutants studied earlier. The molecular etiology of GNAO1 encephalopathies needs further elucidation as a prerequisite for the development of efficient therapeutic approaches. In this work, we combine clinical and medical genetics analysis of a novel GNAO1 mutation with an in-depth molecular dissection of the resultant protein variant. We identify two unrelated patients from Norway and France with a previously unknown mutation in GNAO1, c.509C>G that results in the production of the Pro170Arg mutant Gαo, leading to severe developmental and epileptic encephalopathy. Molecular investigations of Pro170Arg identify this mutant as a unique representative of the pathogenic variants. Its 100-fold-accelerated GTP uptake is not accompanied by a loss in GTP hydrolysis; Zn2+ ions induce a previously unseen effect on the mutant, forcing it to lose the bound GTP. Our work combining clinical and molecular analyses discovers a novel, biochemically distinct pathogenic missense variant of GNAO1 laying the ground for personalized treatment development.

Severity of GNAO1-Related Disorder Correlates with Changes in G-Protein Function.

OBJECTIVE: GNAO1-related disorders (OMIM #615473 and #617493), caused by variants in the GNAO1 gene, are characterized by developmental delay or intellectual disability, hypotonia, movement disorders, and epilepsy. Neither a genotype-phenotype correlation nor a clear severity score have been established for this disorder. The objective of this prospective and retrospective observational study was to develop a severity score for GNAO1-related disorders, and to delineate the correlation between the underlying molecular mechanisms and clinical severity. METHODS: A total of 16 individuals with GNAO1-related disorders harboring 12 distinct missense variants, including four novel variants (p.K46R, p.T48I, p.R209P, and p.L235P), were examined with repeated clinical assessments, video-electroencephalogram monitoring, and brain magnetic resonance imaging. The molecular pathology of each variant was delineated using a molecular deconvoluting platform. RESULTS: The patients displayed a wide variability in the severity of their symptoms. This heterogeneity was well represented in the GNAO1-related disorders severity score, with a broad range of results. Patients with the same variant had comparable severity scores, indicating that differences in disease profiles are not due to interpatient variability, but rather, to unique disease mechanisms. Moreover, we found a significant correlation between clinical severity scores and molecular mechanisms. INTERPRETATION: The clinical score proposed here provides further insight into the correlation between pathophysiology and phenotypic severity in GNAO1-related disorders. We found that each variant has a unique profile of clinical phenotypes and pathological molecular mechanisms. These findings will contribute to better understanding GNAO1-related disorders. Additionally, the severity score will facilitate standardization of patients categorization and assessment of response to therapies in development. ANN NEUROL 2023;94:987-1004.

Genotype-phenotype correlation and treatment effects in young patients with GNAO1-associated disorders.

BACKGROUND: Patients carrying pathogenic variants in GNAO1 often present with early-onset central hypotonia and global developmental delay, with or without epilepsy. As the disorder progresses, a complex hypertonic and hyperkinetic movement disorder is a common phenotype. A genotype-phenotype correlation has not yet been described and there are no evidence-based therapeutic recommendations. METHODS: To improve understanding of the clinical course and pathophysiology of this ultra-rare disorder, we built up a registry for GNAO1 patients in Germany. In this retrospective, multicentre cohort study, we collected detailed clinical data, treatment effects and genetic data for 25 affected patients. RESULTS: The main clinical features were symptom onset within the first months of life, with central hypotonia or seizures. Within the first year of life, nearly all patients developed a movement disorder comprising dystonia (84%) and choreoathetosis (52%). Twelve (48%) patients suffered life-threatening hyperkinetic crises. Fifteen (60%) patients had epilepsy with poor treatment response. Two patients showed an atypical phenotype and seven novel pathogenic variants in GNAO1 were identified. Nine (38%) patients were treated with bilateral deep brain stimulation of the globus pallidus internus. Deep brain stimulation reduced hyperkinetic symptoms and prevented further hyperkinetic crises. The in silico prediction programmes did not predict the phenotype by the genotype. CONCLUSION: The broad clinical spectrum and genetic findings expand the phenotypical spectrum of GNAO1-associated disorder and therefore disprove the assumption that there are only two main phenotypes. No specific overall genotype-phenotype correlation was identified. We highlight deep brain stimulation as a useful treatment option in this disorder.

Molecular and in silico analyses of SYN III gene variants in autism spectrum disorder.

BACKGROUND: Defects in neurotransmission and synaptogenesis are noteworthy in the pathogenesis of ASD. Synapsin III (SYN III) is defined as a synaptic vesicle protein that plays an important role in synaptogenesis and regulation of neurotransmitter release and neurite outgrowth. Therefore, SYN III may associate with many neurodevelopmental diseases, including ASD. AIM: The aim of this study was to investigate whether the SYN III gene -631 C > G (rs133946) and -196 G > A (rs133945) polymorphisms are associated with susceptibility to ASD. METHODS: SYN III variants and the risk of ASD were investigated in 26 healthy children and 24 ASD children. SYN III gene variants were genotyped by PCR-RFLP methods. The differences in genotype and allele frequencies between the ASD and control groups were calculated using the chi-square (χ2). We analysed the SYN III gene using web-based tools. RESULTS: Our results suggest that the presence of the AA genotype of the SYN III -196 G > A (rs133945) polymorphism affects the characteristics and development of ASD in children (p = 0.012). SYN III -631 C > G (rs133946) polymorphism was not associated with ASD (p = 0.524). We have shown the prediction of gene-gene interaction that SYN III is co-expressed with 17 genes, physical interaction with 3 genes, and co-localization with 12 genes. The importance of different genes (SYN I, II, III, GABRD, NOS1AP, GNAO1) for ASD pathogenesis was revealed by GO analysis. CONCLUSION: Considering the role of SYN III and related genes, especially in the synaptic vesicle pathway and neurotransmission, its effect on ASD can be further investigated.

Dystonic Cerebral Palsy Phenotype Due to GNAO1 Variant Responsive to Levodopa.

Background: Cerebral palsy (CP) should not be considered a diagnosis, but rather a syndrome related to several etiologies, including, but not limited to, neurological sequelae of a perinatal brain injury. Case report: 24-years-old man with dystonia and delayed motor and cognitive development had been previously diagnosed with CP. Molecular genetic testing identified a heterozygosity variant in GNAO 1 gene. A therapeutic trial with levodopa was started, with improvement of dystonia. Discussion: GNAO1 gene variant disorders share similarities with other causes of CP syndrome, and thus investigation of this variant should be included in instances of CP syndrome without a clear history of previous perinatal brain injury. GNAO1 dystonic phenotype (DYT-GNAO1) should be considered as dopa-responsive dystonia in some cases.

In-depth molecular profiling of an intronic GNAO1 mutant as the basis for personalized high-throughput drug screening.

BACKGROUND: The GNAO1 gene, encoding the major neuronal G protein Gαo, is mutated in a subset of pediatric encephalopathies. Most such mutations consist of missense variants. METHODS: In this study, we present a precision medicine workflow combining next-generation sequencing (NGS) diagnostics, molecular etiology analysis, and personalized drug discovery. FINDINGS: We describe a patient carrying a de novo intronic mutation (NM_020988.3:c.724-8G>A), leading to epilepsy-negative encephalopathy with motor dysfunction from the second decade. Our data show that this mutation creates a novel splice acceptor site that in turn causes an in-frame insertion of two amino acid residues, Pro-Gln, within the regulatory switch III region of Gαo. This insertion misconfigures the switch III loop and creates novel interactions with the catalytic switch II region, resulting in increased GTP uptake, defective GTP hydrolysis, and aberrant interactions with effector proteins. In contrast, intracellular localization, Gßγ interactions, and G protein-coupled receptor (GPCR) coupling of the Gαo[insPQ] mutant protein remain unchanged. CONCLUSIONS: This in-depth analysis characterizes the heterozygous c.724-8G>A mutation as partially dominant negative, providing clues to the molecular etiology of this specific pathology. Further, this analysis allows us to establish and validate a high-throughput screening platform aiming at identifying molecules that could correct the aberrant biochemical functions of the mutant Gαo. FUNDING: This work was supported by the Joint Seed Money Funding scheme between the University of Geneva and the Hebrew University of Jerusalem.

Visual Function in Children with GNAO1-Related Encephalopathy.

BACKGROUND: GNAO1-related encephalopathies include a broad spectrum of developmental disorders caused by de novo heterozygous mutations in the GNAO1 gene, encoding the G (o) subunit α of G-proteins. These conditions are characterized by epilepsy, movement disorders and developmental impairment, in combination or as isolated features. OBJECTIVE: This study aimed at describing the profile of neurovisual competences in children with GNAO1 deficiency to better characterize the phenotype of the disease spectrum. METHODS: Four male and three female patients with confirmed genetic diagnosis underwent neurological examination, visual function assessment, and neurovisual and ophthalmological evaluation. Present clinical history of epilepsy and movement disorders, and neuroimaging findings were also evaluated. RESULTS: The assessment revealed two trends in visual development. Some aspects of visual function, such as discrimination and perception of distance, depth and volume, appeared to be impaired at all ages, with no sign of improvement. Other aspects, reliant on temporal lobe competences (ventral stream) and more related to object-face exploration, recognition and environmental control, appeared to be preserved and improved with age. SIGNIFICANCE: Visual function is often impaired, with patterns of visual impairment affecting the ventral stream less.