PURPOSE:Biallelic variants in RDH11, encoding retinol dehydrogenase 11, have been associated with a syndromic disorder, based on 4 individuals from 2 unrelated families. We aimed to profile the clinical variability, natural history and associated molecular spectrum of this condition. METHODS:In the frame of a collaborative effort, clinical and molecular data were collected using a semistructured survey. Structural modeling of RDH11 with NADH(P) was used to assess the functional impact of missense variants. RESULTS:Sixteen affected individuals from 9 unrelated families with biallelic RDH11 variants were assembled, frequently showing juvenile-onset progressive myopathy with vacuolar degeneration and prodromic asymptomatic hyperCKemia. Neurodevelopmental impairment, juvenile-onset cataract, and retinal dystrophy were confirmed as common features. Microcephaly and distinct craniofacial traits were also recurrent, whereas short stature was less frequent than previously reported. Most pathogenic variants were truncating, supporting RDH11 loss of function as the mechanism of disease. Consistently, the identified missense changes were predicted to affect RDH11 catalytic function. CONCLUSION:We refine the clinical and molecular spectra of RDH11-related disorder, reclassifying it as syndromic intellectual disability with muscular (juvenile myopathy) and ocular (retinal dystrophy) involvement. These insights are expected to improve diagnostic accuracy and patient care, guiding clinical evaluation, and genetic counseling.

Obsessive-Compulsive Disorder (OCD) traits are increasingly recognized as part of the broader psychopathological profile in Duchenne Muscular Dystrophy (DMD). However, standardized diagnostic data based on DSM-5 criteria are limited. This study aimed to systematically examine OCD traits in pediatric and young adult patients with DMD. In this single-center, cross-sectional observational study, 77 DMD patients were enrolled, regardless of disease severity or comorbidities. Standardized psychometric instruments were administered to assess cognitive functioning and obsessive-compulsive symptomatology. OCD traits were qualitatively identified in 68.8% of patients. Psychometric tests confirmed this high prevalence. OCD traits were significantly associated with reduced general functioning, underscoring the impact of psychopathological dimensions in DMD. Correlations emerged between the site of mutation in the DMD gene, cognitive performance and OCD traits. Interestingly, OCD traits were more frequent in patients with normal IQ, while in those with intellectual disability were more closely related to functional impairment. These findings highlight the need for nuanced clinical evaluation and individualized interventions addressing the interaction between genetic, cognitive, and psychopathological factors in DMD. The study underscores the importance of a holistic approach to care, emphasizing the recognition and management of OCD traits within this population.

The G-protein-coupled receptor kinase-interacting protein 1, GIT1, is a multifunctional scaffold protein that plays key roles in the regulation of actin cytoskeletal dynamics, focal adhesion assembly, membrane trafficking, and intracellular signaling. In mice, loss of Git1 function causes a microcephaly-like phenotype characterized by a smaller brain due to reduced neuronal cell size, accompanied by behavioral deficits, altered gait, and impairment in motor coordination, learning and memory. To date, variants in GIT1 have not been definitely linked to human disease. By applying a combined genomic approach based on linkage analysis and exome sequencing, we provide evidence that biallelic GIT1 variants affecting transcript processing or causing premature termination underlie a syndromic neurodevelopmental disorder. Nine affected individuals from three families were identified to share a clinically homogeneous syndromic phenotype with major features including microcephaly, brain MRI anomalies, developmental delay/intellectual disability, a recognizable facial gestalt, and intrauterine growth restriction with postnatal growth failure. We used complementary in vitro and in vivo approaches to validate this causal relationship. Cell-based functional analyses using patient-derived fibroblasts confirmed the inactivating behavior of the disease-associated variants and demonstrated that loss of GIT1 function disrupts actin cytoskeleton dynamics, leading to defective cell spreading and flawed formation of focal adhesions as a result of reduced RAC1 activation. A zebrafish git1 knockdown model recapitulated the clinical phenotype observed in affected patients and further validated the loss-of-function effect of the identified variants. Collectively, our findings establish an essential role for GIT1 in development and cognitive function.

Heterozygous missense mutations in MORC2 have been implicated in various clinical entities, ranging from early-onset neurodevelopmental disorders to late-onset neuropathies. The mechanism underlying the phenotypic heterogeneity and pleiotropic effects of MORC2 has remained elusive. Here, we analysed blood and fibroblast DNA methylation, transcriptomes, proteomes and phenotypes of 53 MORC2 patients. We identified a MORC2-specific DNA methylation episignature that is universal across all MORC2-associated phenotypes and conserved across different tissues. The MORC2 episignature consists mainly of DNA hypermethylation in promoter regions, leading to transcriptional repression of target genes resulting in a MORC2-specific RNA signature. Concomitant downregulation of three disease-associated genes-ERCC8, NDUFAF2 and FKTN-at different levels mirrors the variable biochemical defects and clinical manifestations observed in MORC2 patients. Silencing of NDUFAF2 accounts for the Leigh syndrome manifestation, whereas dysmorphic features are due to the repression of ERCC8. Overall, we showed that pathogenic MORC2 variants cause specific episignature, whereby methylation level variability and its repression impact on target genes explains the pleiotropy and predicts phenotypic heterogeneity in MORC2-related disorders. We predict that epigenetic variation may underlie pleiotropy in other Mendelian disorders.

Missense variants in TTN pose a major challenge in genetic diagnostics due to their high frequency in the general population, the large size of the gene, and the complex multidomain architecture of the titin protein. While the contribution of truncating variants (TTNtv) to titinopathies is well established, the role of rare TTN missense variants remains poorly defined. Advances in computational prediction and functional testing offer new tools to assess their potential pathogenicity, which however are currently not fully utilized for clinical application. We analyzed an international cohort of unsolved myopathy cases selected based on the presence of a rare missense variant in trans with a TTNtv. Clinical data were collected from neuromuscular centers worldwide. In silico predictions were generated using AlphaMissense and complemented by minor allele frequency (MAF) and exon usage information. Additional inclusion criteria were based on a MAF < 0.010 and an AlphaMissense score ≥ 0.792 for the missense variants, in accordance with the latest ClinGen guidelines. Selected missense variants were characterized in vitro through protein expression and cell imaging assays to assess their effects on domain solubility and aggregation. Thirty patients with TTNtv/missense combinations were identified, presenting with heterogeneous myopathic phenotypes, ranging from congenital to adult onset. An in-depth analysis on AlphaMissense predictions highlighted those changes most frequently predicted as possibly pathogenic. Functional assays showed that three selected variants with changes to proline, located in β-sheets of Ig domains, led to impaired folding, cytoplasmic aggregation and co-localisation with proteostasis markers. In our cohort, all non-proline mutations occurred at buried sites, while some proline substitutions affected exposed residues. Notably, the variant p.(Gln7023Pro) was identified in 5 unrelated families sharing a conserved haplotype, indicating a common ancestor. This variant and the previously reported p.(Arg25480Pro) now meet ACMG criteria for classification as likely pathogenic. By integrating clinical, computational, and functional evidence, we propose a framework for interpreting TTN missense variants. Combining multiple lines of evidence is essential for variants’ classification and interpretation, especially given TTN complexity. Advancing diagnostic accuracy will require tailored interpretation guidelines and a global effort in data sharing and functional validation.

Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by reduced expression of the survival motor neuron (SMN) protein. In addition to motor neuron survival, SMN deficiency affects the integrity and function of afferent synapses that provide glutamatergic excitatory drive essential for motor neuron firing and muscle contraction. However, it is unknown whether deficits in the metabolism of excitatory amino acids and their precursors contribute to neuronal dysfunction in SMA. To address this issue, we measured the levels of the main neuroactive D- and L-amino acids acting on glutamatergic receptors in the central nervous system of SMN∆7 mice as well as the cerebrospinal fluid (CSF) of SMA patients of varying severity before and after treatment with the SMN-inducing drug Nusinersen. Our findings reveal that SMN deficiency is associated with disruption of glutamate and serine metabolism in the CSF of severe SMA patients, including decreased concentration of L-glutamate, which is partially corrected by Nusinersen therapy. Moreover, we identify dysregulated l-glutamine/L-glutamate ratio as a shared neurochemical signature of altered glutamatergic synapse metabolism that implicates neuron-astrocyte dysfunction in both severe SMA patients and mouse models. Lastly, consistent with hypo-glutamatergic neurotransmission in SMA, we show that daily supplementation with the NMDA receptor co-agonist d-serine improves neurological deficits in SMN∆7 mice. Altogether, these findings provide direct evidence for central dysregulation of D- and L-amino acid metabolism linked to glutamatergic neurotransmission in severe SMA and have potential implications for treating this neurological disorder.

BACKGROUND:Non-selective sodium leak channel (NALCN) protein encoded by the NALCN gene is of key importance for neuronal cell excitability. Previous reports showed that biallelic NALCN pathogenic variants cause infantile hypotonia with psychomotor retardation and characteristic facies 1 (IHPRF1) while monoallelic variants lead to congenital contractures of the limbs and face, hypotonia, and developmental delay (CLIFAHDD). In our work, we aimed to expand the heterozygous NALCN-related clinical spectrum, presenting two affected individuals and a literature review. METHODS:We describe two new unrelated subjects harboring monoallelic NALCN pathogenic variants identified through clinical exome sequencing and review the current literature of other heterozygous NALCN patients. RESULTS:The c.3542G > A (p.Arg1181Gln) and the novel c.3423C > A (p.Phe1141Leu) heterozygous missense variants were disclosed in two subjects manifesting a similar phenotype characterized by congenital ataxia with progressive cerebellar atrophy, camptodactyly, and hypertrichosis of the arms (CAPCACH). Other NALCN subjects with overlapping features have already been reported. A combination of these clinical and neuroimaging findings suggests the definition of the new CAPCACH phenotype. CONCLUSION:We expand the heterozygous NALCN-related clinical spectrum from the more severe CLIFFAHDD to the milder CAPCACH phenotype. These conditions should be considered in the differential diagnosis of syndromic congenital ataxias, and the presence of camptodactyly and/or hypertrichosis may represent peculiar diagnostic clues.

Collagen VI-related dystrophies manifest with a spectrum of clinical phenotypes, ranging from Ullrich congenital muscular dystrophy (UCMD), presenting with prominent congenital symptoms and characterized by progressive muscle weakness, joint contractures and respiratory insufficiency, to Bethlem muscular dystrophy, with milder symptoms typically recognized later and at times resembling a limb girdle muscular dystrophy, and intermediate phenotypes falling between UCMD and Bethlem muscular dystrophy. Despite clinical and muscle pathology features highly suggestive of collagen VI-related dystrophy, some patients had remained without an identified causative variant in COL6A1, COL6A2 or COL6A3. With combined muscle RNA sequencing and whole-genome sequencing, we uncovered a recurrent, de novo deep intronic variant in intron 11 of COL6A1 (c.930+189C>T) that leads to a dominantly acting in-frame pseudoexon insertion. We subsequently identified and have characterized an international cohort of 44 patients with this COL6A1 intron 11 causative variant, one of the most common recurrent causative variants in the collagen VI genes. Patients manifest a consistently severe phenotype characterized by a paucity of early symptoms followed by an accelerated progression to a severe form of UCMD, except for one patient with somatic mosaicism for this COL6A1 intron 11 variant who manifests a milder phenotype consistent with Bethlem muscular dystrophy. Partial amelioration of the disease phenotype in this individual provides a strong rationale for the development of our pseudoexon skipping therapy to successfully suppress the pseudoexon insertion, resulting in normal COL6A1 transcripts. We have previously shown that splice-modulating antisense oligomers applied in vitro effectively decreased the abundance of the mutant pseudoexon-containing COL6A1 transcripts to levels comparable to the in vivo scenario of the somatic mosaicism shown here, indicating that this therapeutic approach carries significant translational promise for ameliorating the severe form of UCMD caused by this common recurrent COL6A1 variant.

Spinal Muscular Atrophy (SMA) is a progressive neuromuscular disorder caused by homozygous loss of the survival motor neuron 1 (SMN1) gene, leading to reduced SMN protein expression. Increasing evidence implicates neurotransmission deficits in the pathophysiology of SMA. In particular, alterations in neuroactive amino acids involved in glutamatergic neurotransmission have recently been identified in both the cerebrospinal fluid (CSF) of SMApatients and the spinal cord of SMNΔ7 mouse models. L-arginine, a precursor of nitric oxide, plays a critical role in glutamatergic receptor signalling, influencing neurotransmitter release, synaptic plasticity, and neuroprotection. However, it remains unclear whether SMN deficiency affects L-arginine metabolism in SMA. To address this, we used high-performance liquid chromatography to investigate whether SMN deficiency alters L-arginine homeostasis in the central nervous system of SMNΔ7 mice and in the CSF of SMA patients with varying disease severity, both before and after treatment with the SMN-inducing therapy Nusinersen. Notably, we observed significantly reduced L-arginine levels in the brainstem and spinal cord of symptomatic SMA mice compared to age-matched wild-type littermates. Consistent with these findings, we revealed lower L-arginine levels in severe SMA1 patients compared to milder SMA2 and SMA3 patients and healthy controls, enhancing the translational strength of our findings. Importantly, Nusinersen-mediated SMN upregulation fully restored L-arginine homeostasis in the CSF of severe SMA1 patients. In conclusion, our results demonstrate a dysregulation of L-arginine in SMA and highlight a role for SMN-enhancing therapies in restoring neurochemical alterations observed in patients with this neurodegenerative disease.

Background: Congenital myopathies are a group of neuromuscular disorders that typically present at birth or early childhood with hypotonia and non-progressive or slowly progressive muscle weakness. They are classically subclassified by characteristic structural changes and histopathological findings in skeletal muscle. Variants in over 40 genes have been described to date in patients with various forms of congenital myopathy with overlapping phenotypic and histological features, which poses a challenge for laboratories and clinicians in interpreting genetic findings. Objective: The purpose of this study was to evaluate the evidence supporting each gene-disease relationship and provide an expert-reviewed classification for the clinical validity of genes involved in congenital myopathies. Methods: The ClinGen Neurological Disorders Clinical Domain Working Group assembled the Congenital Myopathies Gene Curation Expert Panel (CongenMyopathy-GCEP), a group of clinicians and geneticists with expertise in congenital myopathies tasked to perform evidence-based curation of 50 gene-disease relationships using the ClinGen semiquantitative framework to assign clinical validity. Results: Our curation effort resulted in 35 (70%) Definitive, eight (16%) Moderate, six (12%) Limited, and one (2%) Disputed disease relationship classifications. The summary of each curation is made publicly available on the ClinGen website. Conclusions: Expert-reviewed assignment of gene-disease relationships by the CongenMyopathy-GCEP facilitates accurate molecular diagnoses for congenital myopathies and can allow genetic testing to focus on genes with a validated role in disease.

Pooled risdiplam (EVRYSDI®) safety data were analysed from 465 symptomatic patients with Types 1–3 SMA in the FIREFISH (NCT02913482), SUNFISH (NCT02908685) and JEWELFISH (NCT03032172) studies (overall exposure: 1,292 patient-years [PY]). Data were also collected from 18 presymptomatic patients in RAIN- BOWFISH (NCT03779334). At the clinical cut-off dates, most treatment-related adverse events (AEs) were mild; none led to treatment withdrawal in any trial (N=483). In presymptomatic patients, the most common AEs per 100PY were vomiting (48.24), teething and pyrexia (41.35 each), nasal congestion (34.46) and diarrhoea and viral infection (27.57 each). In symptomatic patients, the overall rate of AEs decreased with continued treatment; there was decline in the rate of gastrointestinal AEs during the first 4 weeks of treatment and no observable trend in the rate of infection AEs in the first 6 months. In symptomatic patients, serious AEs (SAEs) were more frequent in Type 1 SMA. The rate of SAEs declined in Type 1 SMA but remained stable in Types 2/3 SMA. No SAEs were observed in presymptomatic patients. These data will add to the understanding of the long-term safety profile of risdiplam. Studies are ongoing; safety data will be published annually until patients complete 5 years of treatment.

Collagen VI is an extracellular matrix component encoded by COL6A1, COL6A2 and COL6A3 genes. Causative variants in these genes are associated with the following collagen VI-related myopathies: severe Ullrich congenital muscular dystrophy (UCMD), milder Bethlem myopathy (BM) and intermediate phenotypes (INT). We report the mutation landscape of COL6A genes in 138 Italian patients affected with a collagen VI-related phenotype. The patient cohort included 44 (32%) UCMD, 9 (7%) INT, 61 (44%) BM and 21 (15%) INT/BM patients; 3 patients (2%) with a myosclerosis myopathy (MM) phenotype were also considered. We identified 104 different variants: 26 in COL6A1 (25%), 52 in COL6A2 (50%) and 26 in COL6A3 (25%). The variant spectrum includes missense, splicing, small indel, frameshifting and nonsense variants. Glycine substitutions in the triple helical domain of the collagen VI protein are the commonest variants and occur in all phenotypes. Our genetic profiling disclosed a unique mutation scenario and phenotypic association of the COL6A2 gene with respect to COL6A1 and COL6A3, which may be related to a different evolutive history. Landscape mutation analysis of variants occurring in ultrarare conditions, such as collagen VI-related myopathies, is crucial to better understand the variations’ profile and to gain insight into fundamental knowledge about gene structure and its evolutive origin.

Background Aicardi-Goutières syndrome (AGS) is a rare monogenic leukodystrophy belonging to type I interferonopathies caused by alterations in one of nine genes. Among them, homozygous RNASEH2B:c.529G>A(p.Ala177Thr) is the most common variant worldwide and associated to AGS2. This variant typically leads to severe phenotypes, but individuals with later onset or milder clinical manifestations have been described, with recent finding of asymptomatic homozygous individuals. However, the cause for this intragenotypic clinical variability is unclear, as well as developmental trajectories and early prognostic factors. Our study objective is the description of phenotypic variability in patients with AGS2 and the identification of early clinical markers of prognosis. Methods A multicenter international retrospective natural history study was carried out by recruiting patients with AGS homozygous for p.Ala177Thr variant. Patients were categorized into three groups based on the clinical severity through the composite functional severity score, although comparison was made with the more recently introduced AGS severity score. Disease onset was divided into neonatal, infantile, and later onset. Demographic, clinical, and laboratory data were collected and compared between these groups. Results Irritability at onset correlates significantly to the three functional categories. Early age at onset and presence of extrapyramidal signs correlate to functional outcomes when comparing mild with severe patients. Furthermore, retrospective application of AGS severity score correlated well with the commonly used composite functional severity score. Conclusion The authors observed irritability, early onset, and extrapyramidal signs not to be exclusive to the severe group, hence the need for creation of a composite predictive biomarker for prognosis accuracy.

We recently showed that mutations in RNU4-2 and RNU2-2, two genes that are transcribed into small nuclear RNA (snRNA) components of the major spliceosome, are prevalent causes of dominant neurodevelopmental disorders (NDDs). By genetic association comparing 12,776 NDD cases with 56,064 controls, we now demonstrate the existence of a recessive form of RNU2-2 syndrome that, in England, is even more common than the dominant form. We inferred log Bayes factors for dominant and recessive models of association of 14.0 and 18.2, respectively, and observed 17 rare variants with a posterior probability of pathogenicity conditional on recessive association >0.8. This conservative threshold identified 18 probands (all with unaffected parents) and five affected siblings, each carrying two alleles in trans at these variants. A relaxed threshold of >0.6 identified a further 13 candidate probands. We estimate that recessive RNU2-2 syndrome accounts for 7-10% of families with a diagnosed recessive NDD, and is 36-62% as prevalent as the dominant RNU4-2-related disorder ReNU syndrome. We identified a further seven cases in five pedigrees in two replication collections. Cases are characterized by intellectual disability, global developmental delay and seizures. The variants are predicted to destabilize stem loops and binding domains of the U2-2 snRNA that contribute to spliceosome quaternary structure, intron recognition and catalytic function. Despite this, whole-blood derived RNA-seq data from three patients did not reveal splicing defects, in line with previous analogous observations for dominant RNU2-2 syndrome.

Protocadherin 19 (PCDH19) is an adhesion molecule involved in cell-cell interaction whose mutations cause a drug-resistant form of epilepsy, named PCDH19-Clustering Epilepsy (PCDH19-CE, MIM 300088). The mechanism by which altered PCDH19 function drive pathogenesis is not yet fully understood. Our previous work showed that PCDH19 dysfunction is associated with altered orientation of the mitotic spindle and accelerated neurogenesis, suggesting a contribution of altered cytoskeleton organization in PCDH19-CE pathogenesis in the control of cell division and differentiation. Here, we evaluate the consequences of altered PCDH19 function on microfilaments and microtubules organization, using a disease model obtained from patient-derived induced pluripotent stem cells. We show that iPSC-derived cortical neurons are characterized by altered cytoskeletal dynamics, suggesting that this protocadherin has a role in modulating stability of MFs and MTs. Consistently, the levels of acetylated-tubulin, which is related with stable MTs, are significantly increased in cortical neurons derived from the patient’s iPSCs compared to control cells, supporting the idea that the altered dynamics of the MTs depends on their increased stability. Finally, performing live-imaging experiments using fluorescence recovery after photobleaching and by monitoring GFP-tagged end binding protein 3 (EB3) “comets,” we observe an impairment of the plus-end polymerization speed in PCDH19-mutated cortical neurons, therefore confirming the impaired MT dynamics. In addition to altering the mitotic spindle formation, the present data unveil that PCDH19 dysfunction leads to altered cytoskeletal rearrangement, providing therapeutic targets and pharmacological options to treat this disorder.

Riboflavin transporter deficiency syndrome (RTD) is a rare childhood-onset neurodegenerative disorder caused by mutations in SLC52A2 and SLC52A3 genes, encoding the riboflavin (RF) transporters hRFVT2 and hRFVT3. In the present study we focused on RTD Type 2, which is due to variants in SLC52A2 gene. There is no cure for RTD patients and, although studies have reported clinical improvements with administration of RF, an effective treatment is still unavailable. Here we tested gene augmentation therapy on RTD type 2 patient-derived motoneurons using an adeno-associated viral vector 2/9 (AAV9) carrying the human codon optimized SLC52A2 cDNA. We optimized the in vitro transduction of motoneurons using sialidase treatment. Treated RTD motoneurons showed a significant increase in neurite’s length when compared to untreated samples demonstrating that AAV9-SLC52A2 gene therapy can rescue RTD motoneurons. This leads the path towards in vivo studies offering a potential treatment for RTD patients.

RNU4ATAC is a non-coding gene involved in the minor spliceosome, and is mutated in a spectrum of syndromic skeletal disorders with recessive inheritance. Recently, biallelic RNU4ATAC pathogenic variants were detected in five patients presenting a complex syndromic phenotype and a brain malformation resembling the 'molar tooth sign' (MTS). This is the hallmark of Joubert syndrome (JS), a neurodevelopmental ciliopathy with multiorgan involvement.We reanalysed exome sequencing (ES) from 53 patients with JS, who lacked coding variants in known JS-associated genes. Four RNU4ATAC variants (n.16G>A, n.51G>A, n.13C>T and n.30G>A) were identified in compound heterozygosity in three probands, accounting for 5.6% of negative cases. All patients displayed the MTS and clinical features overlapping those of JS and RNU4ATAC-related skeletal disorders.These findings expand the phenotypic spectrum of RNU4ATAC-related disorders to include a complex neurological-skeletal ciliopathy phenotype, and highlight the relevance of ES reanalysis to uncover non-coding variants often undetected by conventional diagnostics.

We establish the natural history of pediatric-onset TUBB4A-related leukodystrophy to improve clinical trial readiness through a medical record-based longitudinal study. An international cohort of 216 individuals with pediatric-onset TUBB4A-related leukodystrophy was included. Demographic information and medical events were extracted from medical records or publications. Retrospective scores (Gross Motor Function - Metachromatic Leukodystrophy [GMFC-MLD] and Communication Function Classification System [CFCS]) were applied to assess function. Survival analysis distinguished differences in longitudinal neurocognitive function and time to event outcomes between subtypes. A decision tree predicted independent ambulation from early motor milestones. Genotype (p.Asp249Asn vs non-p.Asp249Asn) and independent sitting by age 9 months predicted ambulation by 3 years, and stratification into three subgroups: early-infantile (non- sitting by 9 months), late-infantile (normal early milestones without the common p.Asp249Asn mutation), and a cohort of p.Asp249Asn late- infantile onset individuals. Median age at symptom onset was 0.71 years (interquartile range: [0.33, 1.50]). Common symptoms at onset include delayed development and tone abnormalities (n = 125, 66.5 % and n = 77, 43.0 %). The most common medical complications included scoliosis (N = 51/142), hip dislocation (N = 30/ 101), and seizures (N = 51/163). The early-infantile more severely affected cohort had a greater prevalence of Gtube placement, scoliosis, and seizure compared to the late-infantile form (p < 0.01). Peak motor and communication abilities were comparable between the p.Asp249Asn and the late infantile cohorts. Despite the acquisition of early milestones, individuals with p.Asp249Asn showed a more rapid decline of functional abilities compared to other late infantile forms (log-rank p = 0.0002). Better understanding of TUBB4A-related leukodystrophy subtypes will improve clinical care, allow targeted preventive interventions, and permit disease stratification for future disease-modifying clinical trials.

Hereditary spastic paraplegias (HSPs) are genetically and clinically heterogeneous, slowly progressive neurological disorders characterized by primary involvement of the corticospinal tracts. The early-onset forms of HSP (EO-HSP) are often defined as "cerebral palsy mimics" since symptoms begin in infancy and manifest as spastic di- or tetraplegia and possible neurodevelopmental disorder. The rarity and heterogeneity of these disorders make their diagnosis challenging. In this single-center study, we focus on the outcomes and diagnostic detection rate of EO-HSP patients from a cohort of 104 consecutive HSP cases. The discussion highlights the genetic variability in cases of EO-HSP that tested positive through a series of molecular analyses, particularly those requiring further investigation via whole exome sequencing (WES). This approach has shed light on the etiopathogenetic role of 19 variants across 10 different genes (COQ4, FOXG1, GRIN2B, HPDL, LRP2, RBMX, SPART, TBCD, ZBTB11, and ZC4H2) in 14 patients with complex EO-HSP. Notably, most of these genes are not conventionally classified as HSP-related or included in the SPG classification on the Online Mendelian Inherited in Men (OMIM) catalog. We emphasize the importance of detailed genotype-phenotype correlations and the diagnostic potential of a highly specialized translational approach in clinically selected cases lacking molecular confirmation, thereby expanding our understanding of the genetic variability of EO-HSP.

Redox homeostasis is impaired in Friedreich’s Ataxia (FRDA), a neurodegenerative disease caused by the decreased expression of the mitochondrial protein frataxin. Nrf2, the master regulator of tissue redox balance, is defective in the disease, driving cells to ferroptosis. Neuro-inflammation is recently emerging as an additional pathological mechanism in FRDA and has to be understood in order to go deeper into the pathogenesis of the disease. As a functional cross talk between Nrf2 and NF-kB pathways has been previously reported, we wonder if inflammation may be activated in FRDA as a consequence of Nrf2 deficiency. Thus, we analyzed the expression of proteins involved in the antioxidant and inflammatory responses in fibroblasts of patients with FRDA. We found a significant activation of the TLR4/NF-kB/IL-1β axis in patients, associated to a consistent increase of the redox enzymes thioredoxin 1 (TRX1) and glutaredoxin 1 (GLRX1), which are essential to activate NF-kB under oxidative stress conditions. Furthermore, we investigated the role of 4-HNE, a by-product of lipid peroxidation, as a potential mediator between ferroptosis and inflammation in FRDA.