RESUMEN

White matter hyperintensities (WMHs) refer to a group of diseases with numerous etiologies while oligodendrocytes remain the centerpiece in the pathogenesis of WMHs. Ring Finger Protein 216 (RNF216) encodes a ubiquitin ligase, and its mutation begets WMHs, ataxia, and cognitive decline in patients. Yet no study has revealed the function of RNF216 in oligodendroglia and WHIs before. In this study, we summarized the phenotypes of RNF216-mutation cases and explored the normal distribution of RNF216 in distinct brain regions and neuronal cells by bioinformatic analysis. Furthermore, MO3.13, a human oligodendrocyte cell line, was applied to study the function alteration after RNF216 knockdown. As a result, WMHs were the most common symptom in RNF216-mutated diseases, and RNF216 was indeed relatively enriched in corpus callosum and oligodendroglia in humans. The downregulation of RNF216 in oligodendroglia remarkably hampered cell proliferation by inhibiting the Akt pathway while having no significant effect on cell injury and oligodendrocyte maturation. Combining clinical, bioinformatical, and experimental evidence, our study implied the pivotal role of RNF216 in WMHs which might serve as a potent target in the therapy of WMHs.

Asunto(s)

Proliferación Celular , Oligodendroglía , Ubiquitina-Proteína Ligasas , Sustancia Blanca , Humanos , Mutación con Pérdida de Función , Oligodendroglía/metabolismo , Oligodendroglía/citología , Ubiquitina-Proteína Ligasas/metabolismo , Ubiquitina-Proteína Ligasas/genética , Sustancia Blanca/metabolismo , Sustancia Blanca/patología , Sustancia Blanca/citología

RESUMEN

Biallelic pathogenic variants in the PNPLA6 gene cause a broad spectrum of disorders leading to gait disturbance, visual impairment, anterior hypopituitarism and hair anomalies. PNPLA6 encodes neuropathy target esterase (NTE), yet the role of NTE dysfunction on affected tissues in the large spectrum of associated disease remains unclear. We present a systematic evidence-based review of a novel cohort of 23 new patients along with 95 reported individuals with PNPLA6 variants that implicate missense variants as a driver of disease pathogenesis. Measuring esterase activity of 46 disease-associated and 20 common variants observed across PNPLA6-associated clinical diagnoses unambiguously reclassified 36 variants as pathogenic and 10 variants as likely pathogenic, establishing a robust functional assay for classifying PNPLA6 variants of unknown significance. Estimating the overall NTE activity of affected individuals revealed a striking inverse relationship between NTE activity and the presence of retinopathy and endocrinopathy. This phenomenon was recaptured in vivo in an allelic mouse series, where a similar NTE threshold for retinopathy exists. Thus, PNPLA6 disorders, previously considered allelic, are a continuous spectrum of pleiotropic phenotypes defined by an NTE genotype:activity:phenotype relationship. This relationship, and the generation of a preclinical animal model, pave the way for therapeutic trials, using NTE as a biomarker.

Asunto(s)

Fenotipo , Animales , Femenino , Humanos , Masculino , Ratones , Aciltransferasas , Hidrolasas de Éster Carboxílico/genética , Mutación Missense , Fosfolipasas/genética , Enfermedades de la Retina/genética

RESUMEN

Gordon Holmes syndrome (GHS) is a neurological disorder associated with neuroendocrine, cognitive, and motor impairments with corresponding neurodegeneration. Mutations in the E3 ubiquitin ligase RNF216 are strongly linked to GHS. Previous studies show that deletion of Rnf216 in mice led to sex-specific neuroendocrine dysfunction due to disruptions in the hypothalamic-pituitary-gonadal axis. To address RNF216 action in cognitive and motor functions, we tested Rnf216 knock-out (KO) mice in a battery of motor and learning tasks for a duration of 1 year. Although male and female KO mice did not demonstrate prominent motor phenotypes, KO females displayed abnormal limb clasping. KO mice also showed age-dependent strategy and associative learning impairments with sex-dependent alterations of microglia in the hippocampus and cortex. Additionally, KO males but not females had more negative resting membrane potentials in the CA1 hippocampus without any changes in miniature excitatory postsynaptic current (mEPSC) frequencies or amplitudes. Our findings show that constitutive deletion of Rnf216 alters microglia and neuronal excitability, which may provide insights into the etiology of sex-specific impairments in GHS.

Asunto(s)

Ataxia Cerebelosa , Hormona Liberadora de Gonadotropina/deficiencia , Hipogonadismo , Microglía , Masculino , Femenino , Ratones , Animales , Ratones Noqueados , Cognición , Ubiquitina-Proteína Ligasas/genética

RESUMEN

The association of hypogonadism and cerebellar ataxia was first recognized in 1908 by Gordon Holmes. Since the seminal description, several heterogeneous phenotypes have been reported, differing for age at onset, associated features, and gonadotropins levels. In the last decade, the genetic bases of these disorders are being progressively uncovered. Here, we review the diseases associating ataxia and hypogonadism and the corresponding causative genes. In the first part of this study, we focus on clinical syndromes and genes (RNF216, STUB1, PNPLA6, AARS2, SIL1, SETX) predominantly associated with ataxia and hypogonadism as cardinal features. In the second part, we mention clinical syndromes and genes (POLR3A, CLPP, ERAL1, HARS, HSD17B4, LARS2, TWNK, POLG, ATM, WFS1, PMM2, FMR1) linked to complex phenotypes that include, among other features, ataxia and hypogonadism. We propose a diagnostic algorithm for patients with ataxia and hypogonadism, and we discuss the possible common etiopathogenetic mechanisms.

Asunto(s)

Aminoacil-ARNt Sintetasas , Ataxia Cerebelosa , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil , Hipogonadismo , ARN Polimerasa III , Humanos , Ataxia Cerebelosa/genética , Ataxia/genética , Fenotipo , Hipogonadismo/genética , Hipogonadismo/patología , Mutación , Factores de Intercambio de Guanina Nucleótido/genética , Ubiquitina-Proteína Ligasas/genética , ADN Helicasas/genética , ARN Helicasas/genética , Enzimas Multifuncionales/genética

RESUMEN

BACKGROUND: Variants in the patatin-like phospholipase domain containing 6 (PNPLA6) gene cause a broad spectrum of neurological disorders characterized by gait disturbance, visual impairment, anterior hypopituitarism, and hair anomalies. This review examines the clinical, cellular, and biochemical features found across the five PNPLA6-related diseases, with a focus on future questions to be addressed. MATERIALS AND METHODS: A literature review was performed on published clinical reports on patients with PNPLA6 variants. Additionally, in vitro and in vivo models used to study the encoded protein, Neuropathy Target Esterase (NTE), are summarized to lend mechanistic perspective to human diseases. RESULTS: Biallelic pathogenic PNPLA6 variants cause five systemic neurological disorders: spastic paraplegia type 39, Gordon-Holmes, Boucher-Neuhäuser, Laurence-Moon, and Oliver-McFarlane syndromes. PNPLA6 encodes NTE, an enzyme involved in maintaining phospholipid homeostasis and trafficking in the nervous system. Retinal disease presents with a unique chorioretinal dystrophy that is phenotypically similar to choroideremia and Leber congenital amaurosis. Animal and cellular models support a loss-of-function mechanism. CONCLUSIONS: Clinicians should be aware of choroideremia-like ocular presentation in patients who also experience growth defects, motor dysfunction, and/or hair anomalies. Although NTE biochemistry is well characterized, further research on the relationship between genotype and the presence or absence of retinopathy should be explored to improve diagnosis and prognosis.

Asunto(s)

Blefaroptosis , Coroideremia , Enfermedades del Sistema Nervioso , Enfermedades de la Retina , Animales , Humanos , Ojo , Enfermedades de la Retina/genética , Aciltransferasas , Fosfolipasas/genética

RESUMEN

BACKGROUND: Gordon Holmes syndrome (GHS) is a rare autosomal recessive disorder characterized by hypogonadotropic hypogonadism, cognitive decline, and cerebellar ataxia. Mutations in the Ring Finger Protein 216 (RNF216) gene have been known to be associated with GHS therewithal RNF216 mutations have been detected in cases with Huntington-like disease, 4H syndrome (hypodontia, hypomyelination, ataxia and hypogonadotropic hypogonadism), and congenital hypogonadotropic hypogonadism. CASE PRESENTATION: Here we report a novel homozygous frameshift mutation in RNF216 gene c.1860_1861dupCT (p.Cys621SerfsTer56) in a patient with hypogonadotropic hypogonadism, ataxia, and cognitive decline diagnosed with GHS also co-occurrence of parkinsonism and dystonia which was not reported before. CONCLUSIONS: We report an extremely rare case of GHS. The core features of GHS are well defined, but genotype-phenotype correlations are still limited. To understand the pathophysiology of different phenotypes, the type and localization of novel mutations need to be defined, and the effect of these different variants on clinical features needs to be determined. Further studies should explain the factors of phenotypic variability present in GHS patients with RNF216 mutations.

Asunto(s)

Ataxia Cerebelosa , Síndrome de Klinefelter , Humanos , Ataxia Cerebelosa/genética , Ataxia , Mutación , Ubiquitina-Proteína Ligasas/genética

RESUMEN

  Objective  To summarize the clinical characteristics and RNF216 gene mutation of a patient with Gordon Holmes syndrome (GHS), and to improve the understanding of the genetic and clinica characteristics of this disease through literature review.  Methods  We collected the clinical data of the patient with GHS, extracted the DNA from 2 mL peripheral venous blood of the patient and his parents for whole exome gene detection, and then we analyzed the clinical and genetic characteristics of all previously reported patients with RNF216 gene mutation.  Results  The young male patient was short in stature at sixyearsold and was diagnosed growth hormone deficiency.He had no secondary sexual characteristics by the age of 15 and was diagnosed hypogonadal hypogonadism.After the age of 22, he gradually developed abnormal gait and had progressive decline in speech, motor, and cognitive functions.Whole exome sequencing revealed a homozygous, nonsense mutation c.1549C>T (p.R517*) in the RNF216 gene.His parents were consanguineous and were heterozygous carriers of the mutations with phenotypic normality.Combined with literature review and this case report results showed that a total of 21 patients of the disease in the world and among them 15 had pathogenic variants of RNF216 gene mutation.7 of the 15 had truncated mutations, 5 had missense mutations, and 1 synonym mutation, 1 splice mutation, and 1 deletion mutation respectively.RNF216 gene mutation can be seen in neurodegenerative diseases with multiple overlapping symptoms of GHS, Huntington-like disease, and 4H syndrome.The main clinical manifestations are hypogonadotropic hypogonadism and early-onset progressive neurological dysfunction in adolescence or early adulthood.The median age of onset of neurological symptoms is 28 years old, featuring cerebellar ataxia, dysarthria, and cognitive impairment, as well as imaging manifestations of extensive white matter lesions and cerebellar atrophy.  Conclusions  The mutation of RNF216 gene can cause GHS.Genetic testing is helpful to the diagnosis and treatment of rare diseases.

RESUMEN

An increasing number of genetic diseases are linked to deregulation of E3 ubiquitin ligases. Loss-of-function mutations in the RING-between-RING (RBR) family E3 ligase RNF216 (TRIAD3) cause Gordon-Holmes syndrome (GHS) and related neurodegenerative diseases. Functionally, RNF216 assembles K63-linked ubiquitin chains and has been implicated in regulation of innate immunity signaling pathways and synaptic plasticity. Here, we report crystal structures of key RNF216 reaction states including RNF216 in complex with ubiquitin and its reaction product, K63 di-ubiquitin. Our data provide a molecular explanation for chain-type specificity and reveal the molecular basis for disruption of RNF216 function by pathogenic GHS mutations. Furthermore, we demonstrate how RNF216 activity and chain-type specificity are regulated by phosphorylation and that RNF216 is allosterically activated by K63-linked di-ubiquitin. These molecular insights expand our understanding of RNF216 function and its role in disease and further define the mechanistic diversity of the RBR E3 ligase family.

Asunto(s)

Ataxia Cerebelosa/enzimología , Hormona Liberadora de Gonadotropina/deficiencia , Hipogonadismo/enzimología , Procesamiento Proteico-Postraduccional , Ubiquitina-Proteína Ligasas/metabolismo , Regulación Alostérica , Sitios de Unión , Catálisis , Ataxia Cerebelosa/genética , Cristalografía por Rayos X , Predisposición Genética a la Enfermedad , Hormona Liberadora de Gonadotropina/genética , Células HEK293 , Humanos , Hipogonadismo/genética , Mutación con Pérdida de Función , Lisina , Modelos Moleculares , Fenotipo , Fosforilación , Unión Proteica , Conformación Proteica , Relación Estructura-Actividad , Ubiquitina-Proteína Ligasas/genética , Ubiquitinación

RESUMEN

Gordon Holmes syndrome (GHS) is an autosomal recessive disease characterized by cerebellar ataxia and hypogonadotropic hypogonadism. Among the genes associated with this syndrome, mutations in PNPLA6 have been detected and correlated with the phenotype of GHS. We report a case of a patient affected with GHS, confirmed by physical, neurological, laboratory and genetic analyses. Two compound heterozygous missense mutations on the PNPLA6 gene described as probably damaging/damaging in multiple in silico predictive tools have been detected with massive multigene sequencing. Interestingly, brain MRI uncovered abnormalities in the periventricular white matter, which so far have not been associated with GHS caused by PNPLA6 mutations.

Asunto(s)

Aciltransferasas/genética , Ataxia Cerebelosa/diagnóstico , Ataxia Cerebelosa/genética , Hormona Liberadora de Gonadotropina/deficiencia , Hipogonadismo/diagnóstico , Hipogonadismo/genética , Mutación/genética , Fosfolipasas/genética , Hormona Liberadora de Gonadotropina/genética , Humanos , Masculino , Persona de Mediana Edad

RESUMEN

A wide spectrum of neurodegenerative diseases has been associated with pathogenic variants in the PNPLA6 (patatin-like phospholipase domain-containing protein 6) gene, including spastic paraplegia type 39, Gordon-Holmes, Boucher-Neuhauser, Oliver-Mc Farlane, and Laurence-Moon syndromes. These syndromes present variable and overlapping clinical symptoms, encompassing cerebellar ataxia, hypogonadotropic hypogonadism, chorioretinal dystrophy, spastic paraplegia, muscle wasting, peripheral neuropathy, and cognitive impairment. In the present study, we performed a wide genetic screening in 292 patients presenting with ataxia or spastic paraplegia using a probe-based customized gene panel, covering >200 genes associated with spinocerebellar diseases. We identified six novel and four recurrent PNPLA6 gene variants in eight patients (2.7%). Six patients presented an infantile or juvenile onset (age <18), and two patients had an adult onset. Cerebellar ataxia was observed in seven patients and spastic paraplegia in one patient. Progression of cerebellar symptoms was slow in all patients, who retained ambulation even after a mean disease duration of 15 years. Brain MRI showed cerebellar atrophy in 6/8 patients, more pronounced in superior and dorsal vermis lobules (I to VII). Additional clinical features included hypogonadotropic hypogonadism (5/8), growth hormone deficiency (2/8), peripheral axonal neuropathy (4/8), cognitive impairment (3/8), chorioretinal dystrophy (2/8), and bilateral vestibular areflexia with a reduced visual vestibule-ocular reflex (1/8). In accordance with previous studies, chorioretinal dystrophy was the most frequent presenting symptom in early onset patients, hypogonadotropic hypogonadism in juvenile onset cases, and cerebellar ataxia in adult patients. One patient had an initial clinical presentation compatible with Cerebellar Ataxia with Neuropathy and Vestibular Areflexia Syndrome (CANVAS), but no pathological expansions in the RFC1 gene. In conclusion, patients with PNPLA6 variants present a variable age of onset spanning from infancy to adulthood, and each clinical symptom has an age-dependent manifestation thus requiring a multi-systemic diagnostic approach. The description of patients presenting very late-onset cerebellar ataxia suggests that PNPLA6 genetic screening should also be considered in the diagnostic workout of adult cerebellar ataxia.

RESUMEN

Mutations in STUB1 have been identified to cause autosomal recessive spinocerebellar ataxia type 16 (SCAR16), also named as Gordon Holmes syndrome, which is characterized by cerebellar ataxia, cognitive decline, and hypogonadism. Additionally, several heterozygous mutations in STUB1 have recently been described as a cause of autosomal dominant spinocerebellar ataxia type 48. STUB1 encodes C-terminus of HSC70-interacting protein (CHIP), which functions as an E3 ubiquitin ligase and co-chaperone and has been implicated in several neurodegenerative diseases. In this study, we identified two SCAR16 pedigrees from 512 Taiwanese families with cerebellar ataxia. Two compound heterozygous mutations in STUB1, c.[433A>C];[721C>T] (p.[K145Q];[R241W]) and c.[433A>C];[694T>G] (p.[K145Q];[C232G]), were found in each SCAR16 family by Sanger sequencing, respectively. Among them, STUB1 p.R241W and p.C232G were novel mutations. SCAR16 seems to be an uncommon ataxic syndrome, accounting for 0.4% (2/512) of our cohort with cerebellar ataxia. Clinically, the three patients from the two SCAR16 families presented with cerebellar ataxia alone or in combination with cognitive impairment. The brain MRIs showed a marked cerebellar atrophy of the patients. In conclusion, SCAR16 is an important but often neglected diagnosis of cerebellar ataxia of unknown cause, and the isolated cerebellar ataxia without involvement of other systems cannot be a basis to exclude the possibility of STUB1-related disease.

Asunto(s)

Ataxia Cerebelosa/genética , Hormona Liberadora de Gonadotropina/deficiencia , Hipogonadismo/genética , Ubiquitina-Proteína Ligasas/genética , Adulto , Ataxia Cerebelosa/patología , Cerebelo/patología , Femenino , Hormona Liberadora de Gonadotropina/genética , Humanos , Hipogonadismo/patología , Masculino , Mutación , Linaje , Taiwán , Adulto Joven

RESUMEN

BACKGROUND: Gordon Holmes syndrome (GHS), characterized by cerebellar ataxia and hypogonadotropic hypogonadism (HH), has been related to recessive mutations in PNPLA6 gene. AIMS OF THE STUDY: Describe one Portuguese family with GHS due to compound heterozygosity of two new PNPLA6 variants. METHODS: Report on the clinical presentation, diagnostic and genetic workup to reach GHS diagnosis. RESULTS: The index case presented with slight cognitive impairment and primary amenorrhea, developed at the age of 25 a cerebellar syndrome. Her neurological exam revealed ataxia and mild extrapyramidal syndrome. She was born from non-consanguineous parents and had 8 siblings. Two of her sisters also had history of primary amenorrhea, tremor and ataxia. All 3 were diagnosed with HH and previous FMR1 gene screening on her sisters revealed a 51 CGGs allele. However, 2 normal-sized FMR1 alleles were identified on the proband thus excluding the FXTAS diagnosis in the family. Further PNPLA6 variant screening revealed 2 novel variants in compound heterozygosity [c.2404G > C]; [c.4081C > T], which co-segregated with the disease. CONCLUSIONS: This case shows how incomplete studies can be misleading, increases genetic knowledge of GHS and expands its clinical spectrum. The coexistence of a FMR1 intermediate allele in this family constituted an additional challenge in the etiological investigation.

RESUMEN

Autosomal recessive cerebellar ataxias (ARCAs) represent a heterogeneous group of inherited disorders. The association of early-onset cerebellar ataxia with hypogonadotropic hypogonadism is related to two syndromes, known as Gordon Holmes syndrome (GHS-ataxia and pyramidal signs with hypogonadotropic hypogonadism) and Boucher-Neuhäuser syndrome (BNS-ataxia with chorioretinal dystrophy). Mutations in the PNPLA6 gene have been identified as the cause of hereditary spastic paraplegia and complex forms of ataxia associated with retinal and endocrine manifestations. We reported two Brazilian patients with sporadic, progressive cerebellar ataxia, associated with hypogonadotropic hypogonadism, in whom the GHS and BNS were confirmed by the demonstration of compound heterozygote mutations in the PNPLA6 gene. Genetic analysis of the patient 1 revealed compound heterozygous mutations, one allele in exon 34 and the other allele in exon 29. Genetic exam of the patient 2 also demonstrated compound heterozygous mutations. Three were novel mutations. The missense mutation c.3373G> A, found in the BNS patient, was previously related to Oliver-McFarlane syndrome. These different mutations in this gene suggest a complex phenotype associated disease spectrum.

Asunto(s)

Ataxia Cerebelosa/genética , Mutación , Fosfolipasas/genética , Ataxia Cerebelosa/diagnóstico , Ataxia Cerebelosa/tratamiento farmacológico , Ataxia Cerebelosa/fisiopatología , Diagnóstico Diferencial , Genes Recesivos , Humanos , Masculino , Fenotipo , Adulto Joven

RESUMEN

Sir Gordon Morgan Holmes (1876-1965) was one of the most important founders of modern neurology and a great teacher and scientist. He was the first scientist to challenge the theory of the unitary function of the cerebellum and described cerebellar disorders. Holmes together with Thomas Grainger Stewart (1877-1957) described 40 cases of the rebound phenomenon in cerebellar disease (Stewart-Holmes maneuver or Stewart-Holmes test). He also described the symptoms of inherited neurodegenerative spinocerebellar ataxia involving the olivary nucleus (Gordon-Holmes syndrome). Independently from the Australian neurologist William John Adie (1886-1935), he described the partial iridoplegia (Holmes-Adie pupil or Holmes-Adie syndrome). His teaching skills became clearly visible in Goulstonian and Croonian lectures dedicated to spinal cord injuries.

Asunto(s)

Neurología/historia , Historia del Siglo XIX , Historia del Siglo XX

RESUMEN

We describe a patient with Gordon Holmes syndrome presenting with a combination of hypogonadotropic hypogonadism, ataxia and progressive cognitive decline, with distinct MRI brain findings. Recent genetic advances allowed the identification of the genetic defects responsible for this rather unusual combination of endocrine and neurological involvement.

Asunto(s)

Ataxia Cerebelosa/genética , Ataxia Cerebelosa/patología , Hormona Liberadora de Gonadotropina/deficiencia , Hipogonadismo/genética , Hipogonadismo/patología , Genotipo , Hormona Liberadora de Gonadotropina/genética , Humanos , Masculino , Fenotipo , Adulto Joven

RESUMEN

BACKGROUND: CHIP, the protein encoded by STUB1, is a central component of cellular protein homeostasis and interacts with several key proteins involved in the pathogenesis of manifold neurodegenerative diseases. This gives rise to the hypothesis that mutations in STUB1 might cause a far more multisystemic neurodegenerative phenotype than the previously reported cerebellar ataxia syndrome. METHODS: Whole exome sequencing data-sets from n = 87 index subjects of two ataxia cohorts were screened for individuals with STUB1 mutations. In-depth phenotyping by clinical evaluation and neuroimaging was performed in mutation carriers. RESULTS: We identified four novel STUB1 mutations in three affected subjects from two index families (frequency 2/87 = 2.3%). All three subjects presented with a severe multisystemic phenotype including severe dementia, spastic tetraparesis, epilepsy, and autonomic dysfunction in addition to cerebellar ataxia, plus hypogonadism in one index patient. Diffusion tensor imaging revealed degeneration of manifold supra- and infratentorial tracts. CONCLUSIONS: Our findings provide clinical and imaging support for the notion that CHIP is a crucial converging point of manifold neurodegenerative processes, corresponding with its universal biological function in neurodegeneration. Further, our data reveal the second STUB1 family with ataxia plus hypogonadism reported so far, demonstrating that Gordon Holmes syndrome is indeed a recurrent manifestation of STUB1. However, it does not present in isolation, but as part of a broad multisystemic neurodegenerative process. This supports the notion that STUB1 disease should be conceptualized not by historical or clinical syndromic names, but as a variable multisystemic disease defined by disturbed function of the underlying STUB1 gene, which translates into a multidimensional gradual spectrum of variably associated clinical signs and symptoms.

Asunto(s)

Ataxia Cerebelosa/genética , Hormona Liberadora de Gonadotropina/deficiencia , Hipogonadismo/genética , Enfermedades Neurodegenerativas/genética , Ubiquitina-Proteína Ligasas/metabolismo , Adulto , Secuencia de Aminoácidos , Femenino , Hormona Liberadora de Gonadotropina/genética , Humanos , Masculino , Persona de Mediana Edad , Mutación , Enfermedades Neurodegenerativas/diagnóstico por imagen , Enfermedades Neurodegenerativas/patología , Linaje , Dominios Proteicos , Ubiquitina-Proteína Ligasas/genética

RESUMEN

Multiple loss-of-function mutations in TRIAD3 (a.k.a. RNF216) have recently been identified in patients suffering from Gordon Holmes syndrome (GHS), characterized by cognitive decline, dementia, and movement disorders. TRIAD3A is an E3 ubiquitin ligase that recognizes and facilitates the ubiquitination of its target for degradation by the ubiquitin-proteasome system (UPS). Here, we demonstrate that two of these missense substitutions in TRIAD3 (R660C and R694C) could not regulate the degradation of their neuronal target, activity-regulated cytoskeletal-associated protein (Arc/Arg 3.1), whose expression is critical for synaptic plasticity and memory. The synaptic deficits due to the loss of endogenous TRIAD3A could not be rescued by TRIAD3A harboring GHS-associated missense mutations. Moreover, we demonstrate that the loss of endogenous TRIAD3A in the mouse hippocampal CA1 region led to deficits in spatial learning and memory. Finally, we show that these missense mutations abolished the interaction of TRIAD3A with Arc, disrupting Arc ubiquitination, and consequently Arc degradation. Our current findings of Arc misregulation by TRIAD3A variants suggest that loss-of-function mutations in TRIAD3A may contribute to dementia observed in patients with GHS driven by dysfunctional UPS components, leading to cognitive impairments through the synaptic protein Arc.

Asunto(s)

Ataxia Cerebelosa/genética , Disfunción Cognitiva/patología , Proteínas del Citoesqueleto/metabolismo , Hormona Liberadora de Gonadotropina/deficiencia , Hipogonadismo/genética , Mutación/genética , Proteínas del Tejido Nervioso/metabolismo , Sinapsis/patología , Ubiquitina-Proteína Ligasas/genética , Animales , Región CA1 Hipocampal/patología , Clatrina/metabolismo , Disfunción Cognitiva/metabolismo , Endocitosis , Técnicas de Silenciamiento del Gen , Hormona Liberadora de Gonadotropina/genética , Células HEK293 , Humanos , Ratones Endogámicos C57BL , Mutación Missense/genética , Unión Proteica , Proteolisis , Ratas Sprague-Dawley , Receptores AMPA/metabolismo , Memoria Espacial , Sinapsis/metabolismo , Transmisión Sináptica , Ubiquitina-Proteína Ligasas/metabolismo , Ubiquitinación

RESUMEN

We comment on the recent publication by Ganos et al. [1] classifying a patient with non-specific white matter abnormalities, cerebellar atrophy, hypogonadotropic hypogonadism and absent lower median incisors as 4H syndrome. He had mutations in RNF216. Mutations in this gene cause Gordon-Holmes syndrome, distinct from 4H syndrome.

Asunto(s)

Ataxia Cerebelosa/genética , Enfermedades Autoinmunes Desmielinizantes SNC/genética , Hipogonadismo/genética , Hipotonía Muscular/genética , Mutación/genética , Ubiquitina-Proteína Ligasas/genética , Humanos , Masculino