Tubulinopathies encompass a spectrum of disorders resulting from variants in genes encoding α- and β-tubulins, the key components of microtubules. While previous studies have linked de novo or dominantly inherited TUBA4A missense variants to neurodegenerative phenotypes, including amyotrophic lateral sclerosis, frontotemporal dementia, spastic ataxia, and recently, an isolated congenital myopathy, the full phenotypic and genotypic spectrum of TUBA4A-related disorders remains incompletely characterised. In this multi-centre study, we identified one previously reported and 12 novel TUBA4A missense variants in 31 individuals from 19 unrelated families. Remarkably, individuals in 17 families presented with a myopathy without any CNS involvement or history of such disease. In the remaining two families, we observed probands with cerebellar ataxia and epilepsy accompanying proximal and axial muscle weakness along with protein aggregation. The coexistence of neuromuscular and neurodegenerative features with protein aggregation defines a multisystem proteinopathy. These two families thus establish the first association between TUBA4A and multisystem proteinopathy. Our cohort exhibited diverse genotypes and inheritance patterns: four families demonstrated autosomal dominant transmission through heterozygous variants in TUBA4A, three probands had recessive inheritance due to homozygous variants, while the respective heterozygous carriers were asymptomatic; five probands carried de novo variants, and nine probands with heterozygous variants were classified as sporadic cases. Clinical phenotypes ranged from mild to severe myopathy, predominantly affecting the axial and paraspinal muscles. We observed a range of disease onset, from congenital to late adulthood. Creatine kinase levels were variable, ranging from normal to highly elevated. Cardiac function remained preserved across the cohort. Muscle biopsies showed heterogenous myopathic changes, including myofibre size variation, nemaline bodies, core-like regions, and internal nuclei. Immunohistochemical analysis revealed protein accumulations positive for TDP-43 (n=2), p62 (n=5), and TUBA4A (n=6). Complementary in silico and in vitro investigations suggested that the identified TUBA4A variants cause significant protein abnormalities and may differentially impact microtubule dynamics. Correlation analyses integrating clinical severity, variant location, and mechanistic readouts further demonstrated that domain specificity within TUBA4A influences both the pattern of muscle involvement and the extent of microtubule disruption. Our findings establish myo-tubulinopathies as distinct clinical entities, encompassing both primary myopathies and multisystem proteinopathies with muscle involvement. This study broadens the phenotypic and genotypic spectrum of TUBA4A-related disorders beyond autosomal dominant or de novo mechanisms and neurodegenerative presentations. These results underscore the importance of considering TUBA4A variants in the differential diagnosis of axial myopathies and multisystem proteinopathies, regardless of central nervous system (CNS) involvement. The phenotypic spectrum of SPG7-related neurologic disorder includes uncomplicated spastic ataxia, complicated spastic ataxia, spinocerebellar ataxia, and isolated optic nerve atrophy. Although onset typically occurs in adulthood, it may start in infancy or as late as age 72 years. Initially the spastic paraplegia is typically characterized by insidiously progressive bilateral leg weakness and spasticity or cerebellar findings (ataxia, dysarthria, and dysphagia) or both. Other central nervous system findings include decreased visual acuity due to optic neuropathy, cognitive impairment, and dystonia. Peripheral nervous system involvement manifests as motor and sensory neuropathy, neuropathic pain, and amyotrophy. Associated musculoskeletal involvement includes pes cavus and scoliosis. Spasticity and ataxia are progressive and may result in wheelchair dependence. The diagnosis of SPG7-related neurologic disorder is established in a proband with suggestive findings and biallelic pathogenic variants in SPG7 identified by molecular genetic testing. Treatment of manifestations: Multidisciplinary care by specialists in neurology, ophthalmology, low vision services, audiology, urology, physiatry, occupational therapy, physical therapy, orthopedics, feeding therapy and nutrition, speech-language therapy, social work, psychology, and clinical genetics. Surveillance: Monitor existing manifestations, the individual's response to supportive care, and the emergence of new manifestations with routinely scheduled evaluations by treating specialists. SPG7-related neurologic disorder is inherited in an autosomal recessive manner. (Several studies have reported a single [heterozygous] pathogenic variant in SPG7 in individuals with SPG7-related neurologic disorder suggesting the possibility of autosomal dominant inheritance; however, the possibility of autosomal dominant inheritance remains controversial.) If both parents are known to be heterozygous for an SPG7 pathogenic variant, each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being heterozygous, and a 25% chance of inheriting neither of the familial pathogenic variants. Once the SPG7 pathogenic variants have been identified in an affected family member, heterozygote testing for at-risk relatives and prenatal/preimplantation genetic testing for SPG7-related neurologic disorder are possible. AFG3L2-related neurologic disorders comprise four phenotypes. Spinocerebellar ataxia type 28 (SCA28), the most common phenotype, is characterized by young adult onset (26.5 ± 17.2 years); the onset range is from birth to 74 years of a cerebellar syndrome manifesting initially as very slowly progressive gait and limb ataxia resulting in incoordination and balance problems. Less frequently, ptosis/ophthalmoplegia, dysarthria, or upper-limb incoordination may occur as the initial finding. Pyramidal syndrome (increased and brisk reflexes, extensor plantar reflex, and spasticity) is commonly observed in individuals with longer disease duration. Although cognitive impairment, spasticity, and ophthalmologic signs can occur with disease progression, most individuals remain ambulatory and fully independent throughout their lives. Spastic ataxia type 5 (SPAX5), reported in 14 individuals to date, ranges from severe neurodegeneration with microcephaly, poor weight gain, developmental delay, developmental regression around age nine months, and death as early as age 2.5 years. Milder presentations range from onset in infancy to an early-onset complex cerebellar ataxia with myoclonic epilepsy. AFG3L2-related autosomal recessive spinocerebellar ataxia (AFG3L2-SCAR), reported in two individuals to date, is a late-onset ataxia with a clinical phenotype closely resembling that of SCA28. Optic atrophy type 12 (OPA12) manifests as decreased visual acuity (variable but frequently ranging from 0.2/10 to 2/10), photophobia, and impaired color vision. Ophthalmologic findings are optic nerve pallor and highly reduced retinal nerve fiber layer on optical coherence tomography. Although affected individuals do not present with ataxia, some may exhibit sensorineural hearing loss, neurodevelopmental disorders, dystonia, and spasticity. The diagnoses of SCA28 and OPA12 are established in a proband with suggestive findings and a heterozygous pathogenic variant in AFG3L2 identified by molecular genetic testing. The diagnoses of SPAX5 and AFG3L2-SCAR are established in a proband with suggestive findings and biallelic pathogenic variants in AFG3L2 identified by molecular genetic testing. Treatment of manifestations: Supportive care to improve quality of life, maximize function, and reduce complications is recommended. This ideally involves multidisciplinary care by specialists in relevant fields including neurologists (to address pharmacologic treatment of myoclonic epilepsy, spasticity, movement disorders); occupational therapists (to optimize activities of daily living and home safety); physiatrists and physical therapists (to help maintain independence and mobility); nutritionists and feeding therapy programs (to assess the risks of aspiration and need for gastrostomy tube placement for those with dysphagia); speech-language therapists (to address communication for individuals who have expressive language difficulties), ophthalmologists (to consider surgery for ptosis); low vision clinics (for those with optic atrophy); and social workers and psychologists (depending on any cognitive or psychologic manifestations). Surveillance: Routinely scheduled follow-up appointments with treating clinicians are recommended to monitor existing manifestations, the individual's response to supportive care, and the emergence of new manifestations. Agents/circumstances to avoid: Alcohol consumption and sedatives such as benzodiazepines that may worsen gait ataxia and coordination. Carbamazepine and phenytoin may exacerbate myoclonus in SPAX5. SCA28 and OPA12 are inherited in an autosomal dominant manner. AFG3L2-SCAR and SPAX5 are inherited in an autosomal recessive manner. Autosomal dominant inheritance: Most individuals diagnosed with SCA28, and some individuals diagnosed with OPA12, have an affected parent. Some individuals diagnosed with an autosomal dominant AFG3L2-related neurologic disorder have the disorder as the result of a de novo pathogenic variant. Each child of an individual with an autosomal dominant AFG3L2-related neurologic disorder has a 50% risk of inheriting the pathogenic variant. If the reproductive partner of an individual with an autosomal dominant AFG3L2-related neurologic disorder also has an AFG3L2 pathogenic variant, offspring are at risk of inheriting biallelic pathogenic variants and having an autosomal recessive AFG3L2-related neurologic disorder. Once the AFG3L2 pathogenic variant has been identified in an affected family member, predictive testing for at-risk relatives and prenatal/preimplantation genetic testing are possible. Autosomal recessive inheritance: The parents of a child with an autosomal recessive AFG3L2-related neurologic disorder are presumed to be heterozygous for an AFG3L2 pathogenic variant. If both parents are known to be heterozygous for an AFG3L2 pathogenic variant, each sib of an affected individual has at conception a 25% chance of inheriting biallelic pathogenic variants and being affected, a 50% chance of being heterozygous, and a 25% chance of inheriting neither of the familial AFG3L2 pathogenic variants. Heterozygous family members of an individual with an autosomal recessive AFG3L2-related neurologic disorder are typically asymptomatic and the risk of developing an AFG3L2-related neurologic disorder appears to be low. Once the AFG3L2 pathogenic variants has been identified in an affected family member, carrier testing for at-risk relatives and prenatal/preimplantation genetic testing are possible.

Tubulinopathies encompass a wide spectrum of disorders resulting from variants in genes encoding α- and β-tubulins, the key components of microtubules. While previous studies have linked de novo or dominantly inherited TUBA4A missense variants to neurodegenerative phenotypes, including amyotrophic lateral sclerosis, frontotemporal dementia, hereditary spastic ataxia, and more recently, an isolated report of congenital myopathy, the full phenotypic and genotypic spectrum of TUBA4A-related disorders remains incompletely characterised. In this multi-centre study, we identified 13 novel TUBA4A missense variants in 31 individuals from 19 unrelated families. Remarkably, affected individuals in 17 families presented with a primary axial myopathy without any identified CNS involvement or history of such disease. In the remaining two families, we observed probands with cerebellar ataxia and epilepsy accompanying proximal and axial muscle weakness, establishing the first documented association between TUBA4A variants and multisystem proteinopathy. Our cohort exhibited diverse genotypes and associated inheritance patterns: four families demonstrated autosomal dominant transmission through heterozygous variants in TUBA4A, three probands had homozygous TUBA4A variants, where the biallelic genotype was found to be associated with the disease, and the heterozygous carriers were asymptomatic; five probands carried de novo variants, and nine probands with heterozygous TUBA4A variants were classified as "isolated-sporadic cases" where parental samples were unavailable. Clinical phenotypes ranged from mild to severe myopathy, predominantly affecting the axial and paraspinal muscles. We observed a range of disease onset, from congenital to late adulthood. Creatine kinase levels were also variable, ranging from normal to highly elevated. Cardiac function remained preserved across the cohort. Muscle biopsies revealed a range of pathologies, including myofibre size variation, myofibre atrophy, nemaline bodies, core-like regions, internal nuclei, and endomysial fibrosis. Immunohistochemical staining showed evidence of proteinopathy, with autophagic features and TUBA4A accumulation in patient myofibres. Complementary in silico and in vitro investigations suggested that the identified TUBA4A substitutions cause significant protein abnormalities and may differentially impact microtubule dynamics. Our findings establish myo-tubulinopathies as distinct clinical entities, encompassing both primary myopathies and multisystem proteinopathies with muscle involvement. This study broadens the phenotypic and genotypic spectrum of TUBA4A-related disorders beyond autosomal dominant or de novo mechanisms and neurodegenerative presentations. These results underscore the importance of considering TUBA4A variants in the differential diagnosis of axial myopathies and multisystem proteinopathies, regardless of central nervous system (CNS) involvement.

Mitochondria-associated paraplegin dysfunction is primarily linked to spastic paraplegia; however, genetic alterations in SPG7 have been associated with a broader spectrum of clinical symptoms. To identify disease-causing variants in the SPG7 gene, 437 patients with spastic ataxia, mitochondrial dysfunction-associated symptoms, or motoneuron lesions detected by EMG have been tested. We aimed to assess the clinical spectrum and determine the frequency of damaging variants within patient groups, particularly those less studied. Using ACMG criteria, we identified 10 pathogenic or likely pathogenic variants, 5 variants of uncertain significance with predicted damaging effects, and a probable risk factor variant in 58 patients. We identified 25 biallelic and 33 monoallelic cases. The most common variant was p. Leu78Ter (N = 23), followed by p. Ala510Val (N = 21). The point prevalence of SPG7-associated conditions in Hungary in 2024 is 0.46 per 100 000. In addition to well-characterized cohorts, SPG7 alterations were frequently identified in cohorts with multisystemic mitochondrial disease and lower motoneuron lesions. Multiple mtDNA deletions and histological abnormalities were consistently observed across all groups. In monoallelic cases, no evidence of a digenic effect involving AFG3L2 was found. Both autosomal dominant and recessive inheritance patterns were documented, with monoallelic cases typically presenting with a milder phenotype.

Ubiquitin C-terminal hydrolase L1 (UCHL1) has been associated with a severe, complex autosomal recessive spastic paraplegia (HSP79) [1] [2] [3] [4]. More recently, UCHL1 loss of function (LoF) variants have been associated to an autosomal dominant disease characterized by late-onset spastic ataxia, neuropathy, and frequent optic atrophy [5]. Routine clinical care whole-genome (WGS) and exome (ES) sequencing. We present three families with autosomal dominant UCHL1-related disorder. The clinical phenotype mainly associated optic atrophy, mixed cerebellar and sensory ataxia, and possible hearing loss. We delineated two major phenotypes, even within the same family: (1) juvenile severe optic atrophy followed by a later-onset ataxia, or (2) late-onset ataxia with asymptomatic or mild optic atrophy. The families harboured three novel heterozygous variants in UCHL1: two loss of function (p.Lys115AsnfsTer40; c.171_174 + 7del11), and one missense (p.Asp176Asn) involving the catalytic site of the protein and potentially altering the adjacent splice site. We confirm the existence of dominantly inherited UCHL1 pathogenic variants. We describe a considerable intrafamilial phenotypic variability, with two main phenotypes. Optic atrophy was consistently present, but with varying degrees of severity. Neither delayed motor or intellectual development, nor dysmorphic features were part of the dominant phenotype in comparison with the autosomal recessive form. The molecular mechanism appears to be haploinsufficiency. UCHL1 monoallelic variants should therefore be considered in any case of early-onset optic atrophy or in late-onset complex ataxic syndrome with asymptomatic optic atrophy.

We report the cases of two Spanish pediatric patients with hypotonia, muscle weakness and feeding difficulties at birth. Whole-exome sequencing (WES) uncovered two new homozygous VAMP1 (Vesicle Associated Membrane Protein 1) splicing variants, NM_014231.5:c.129+5 G > A in the boy patient (P1) and c.341-24_341-16delinsAGAAAA in the girl patient (P2). This gene encodes the vesicle-associated membrane protein 1 (VAMP1) that is a component of a protein complex involved in the fusion of synaptic vesicles with the presynaptic membrane. VAMP1 has a highly variable C-terminus generated by alternative splicing that gives rise to three main isoforms (A, B and D), being VAMP1A the only isoform expressed in the nervous system. In order to assess the pathogenicity of these variants, expression experiments of RNA for VAMP1 were carried out. The c.129+5 G > A and c.341-24_341-16delinsAGAAAA variants induced aberrant splicing events resulting in the deletion of exon 2 (r.5_131del; p.Ser2TrpfsTer7) in the three isoforms in the first case, and the retention of the last 14 nucleotides of the 3' of intron 4 (r.340_341ins341-14_341-1; p.Ile114AsnfsTer77) in the VAMP1A isoform in the second case. Pathogenic VAMP1 variants have been associated with autosomal dominant spastic ataxia 1 (SPAX1) and with autosomal recessive presynaptic congenital myasthenic syndrome (CMS). Our patients share the clinical manifestations of CMS patients with two important differences: they do not show the typical electrophysiological pattern that suggests pathology of pre-synaptic neuromuscular junction, and their muscular biopsies present hypertrophic fibers type 1. In conclusion, our data expand both genetic and phenotypic spectrum associated with VAMP1 variants.