Genetic Variant in GRM1 Underlies Congenital Cerebellar Ataxia with No Obvious Intellectual Disability.

Metabotropic glutamate receptor 1 (mGluR1) plays a crucial role in slow excitatory postsynaptic conductance, synapse formation, synaptic plasticity, and motor control. The GRM1 gene is expressed mainly in the brain, with the highest expression in the cerebellum. Mutations in the GRM1 gene have previously been known to cause autosomal recessive and autosomal dominant spinocerebellar ataxias. In this study, whole-exome sequencing of a patient from a family of Azerbaijani origin with a diagnosis of congenital cerebellar ataxia was performed, and a new homozygous missense mutation in the GRM1 gene was identified. The mutation leads to the homozygous amino acid substitution of p.Thr824Arg in an evolutionarily highly conserved region encoding the transmembrane domain 7, which is critical for ligand binding and modulating of receptor activity. This is the first report in which a mutation has been identified in the last transmembrane domain of the mGluR1, causing a congenital autosomal recessive form of cerebellar ataxia with no obvious intellectual disability. Additionally, we summarized all known presumable pathogenic genetic variants in the GRM1 gene to date. We demonstrated that multiple rare variants in the GRM1 underlie a broad diversity of clinical neurological and behavioral phenotypes depending on the nature and protein topology of the mutation.

Bibliometría y mapeo de redes de la producción científica internacional de Cuba sobre ataxias (1993-2020) / Bibliometrics and network mapping of Cuban international scientific production on ataxias (1993-2020)

El objetivo del estudio fue caracterizar el potencial investigador cubano en el ámbito de las ataxias y su evolución temporal. Se realizó una búsqueda en la base de datos Web of Science y se obtuvieron todos los documentos publicados entre 1993 y 2020. Se aplicaron indicadores bibliométricos para explorar la producción, dispersión, distribución y crecimiento anual de los documentos (ley de Price, ley de Lotka, índice de transitoriedad y modelo de Bradford). Se calculó el índice de participación y colaboración de países e instituciones y, por cartografía bibliométrica, se exploraron las redes de coocurrencia de los términos más utilizados. La producción científica de Cuba sobre ataxias hereditarias es alta (219 documentos) y se ajusta a un crecimiento lineal (r= 0,7580). El período estudiado concentra el 47,95 por ciento de los registros con un ritmo anual de publicaciones del 6,6 por ciento y tiempo de duplicidad de 10,8 años. El total de citas fue de 3807 (índice medio: 131,27; índice -h: 31). Se concluye que el crecimiento de la literatura científica cubana sobre ataxias fue lineal para el período estudiado, lo que confirma el incumplimiento de la ley de Price de crecimiento de la literatura científica. El estudio también corrobora la importante red de integración y cooperación internacional entre los diferentes autores y la interdisciplinariedad de los trabajos, evidencia del éxito del Centro para la Investigación y Rehabilitación de las Ataxias Hereditarias (CIRAH), al planificar una estrategia de colaboración científica con objetivos definidos(AU)

The objective of this study was to characterize the Cuban research potential in the field of ataxias and its temporal evolution. A search was carried out in the Web of Science database and all the documents published from 1993 to 2020 were retrieved. Bibliometric indicators were applied to explore the production, dispersion, distribution and annual growth of the documents (Price's law, Lotka's law, transience index and Bradford model). The participation and collaboration index of countries and institutions was calculated and, through bibliometric cartography, the co-occurrence networks of the most used terms were explored. The Cuban scientific production on hereditary ataxias is high (219 documents) and it adjusts to a linear growth (r = 0.7580). The period studied concentrates 47.95percent of the records with an annual publication rate of 6.6percent and 10.8 years' duplication time. The total number of citations was 3807 (mean index: 131.27; h-index: 31). Growth of the Cuban scientific literature on ataxias was concluded to be linear for the period studied, which confirms the non-compliance with Price's law of growth of scientific literature. The study also corroborates the important network of integration and international cooperation among the different authors and the interdisciplinarity of the papers, marking the success of the Center for Research and Rehabilitation of Hereditary Ataxias (CIRAH), when planning a strategy of scientific collaboration with objectives defined(AU)

Clinical application of next generation sequencing in hereditary spinocerebellar ataxia: increasing the diagnostic yield and broadening the ataxia-spasticity spectrum. A retrospective analysis.

One of the hardest challenges in medical genetics is to reach a molecular diagnosis in the presence of rare brain disorders. Hereditary spinocerebellar ataxia (HA), characterized by high clinical and genetic heterogeneity, is among the diseases that present this challenge. HA can have features overlapping with those of other neurological diseases, especially hereditary spastic paraplegia (HSP), as routine clinical application of next generation sequencing (NGS) has confirmed. This article reviews different NGS methods applied in heterogeneous cohorts of patients with suspected HA and suggests that exome sequencing should be considered the first-tier genetic approach in this setting. Its application lends support to the hypothesis of HA and HSP as two extremes of a continuous spectrum.

[Recent Topics in Autosomal Dominantly Inherited Spinocerebellar Ataxias].

Among various dominantly inherited spinocerebellar ataxias (SCAs), it is revealed that the molecular mechanism of so called "non-coding microsatellite repeat expansion disorders" was involved in RNA gain-of-function as well as "RAN translation". Recently, the "polyglutamine disorders" caused by the coding CAG repeat expansions were also clarified that they were involved in RNA mechanism or RAN translation. The common molecular mechanism might exist between SCAs of which the repeat expansions were located in both coding and non-coding regions.

Spongy degeneration with cerebellar ataxia in Malinois puppies: a hereditary autosomal recessive disorder?

BACKGROUND: There is a high incidence of hereditary degenerative diseases of the central nervous system in purebred dogs. HYPOTHESIS: Cerebellar ataxia in Malinois puppies, caused by degenerative changes that predominate in cerebellar nuclei and the granular cell layer, is a hereditary disorder that is distinct from cerebellar cortical abiotrophies. ANIMALS: Thirteen Malinois puppies with cerebellar ataxia. METHODS: Retrospective study. Records of Malinois puppies with spongy degeneration of the cerebellar nuclei were analyzed including clinical signs, histopathological changes, and pedigree data. RESULTS: Signs of cerebellar dysfunction were observed in puppies of both sexes from 5 different litters (1995-2009) of phenotypically normal parents. Clinical signs started before the age of 2 months and resulted in euthanasia of all puppies by the age of 13 weeks. Histopathology disclosed marked bilateral spongy degeneration of the cerebellar nuclei and vacuoles in the granular cell layer and foliate white matter of the cerebellum. In some puppies, discrete vacuoles in gray and white matter were present in other parts of the brain. Furthermore, spheroids and dilated myelin sheaths were observed. Pedigree data and segregation frequency support an autosomal recessive hereditary disorder. CONCLUSIONS AND CLINICAL IMPORTANCE: Malinois suffer from a hereditary spongiform degeneration that predominates in the cerebellum and causes an early onset of clinical signs with unfavorable prognosis. Future efforts should increase awareness among veterinarians and breeders and aim to identify underlying metabolic mechanisms and the affected genes.

Degeneración tumoral en meningocele no intervenido. Descripción de dos casos / Tumoral degeneration occurring over a non-healing meningocele. Report of two cases

Asistir a pacientes que presentan un meningocele gigante y en edad adulta es una rareza clínica, debido en parte a que es una malformación disráfica con una incidencia baja y a que el índice de supervivencia de los recién nacidos con éstas patologías era menor en épocas anteriores, pese a la benignidad de la malformación. Aportamos a la literatura existente los casos de dos pacientes que nacieron con un disrafismo espinal abierto y que no fueron operados en su momento, llegando a la edad adulta con voluminosos sacos meningocutáneos que tuvieron que ser extirpados, por presentar en el caso de más edad, un absceso con fistulización sin salida de LCR que no mejoró con tratamiento tópico y antibiótico. En el otro caso por sospecha de malignización debido a crecimiento progresivo de la malformación durante el último año, endurecimiento de la piel y dolor. El estudio anatomopatológico de los sacos resecados demostró la existencia de una degeneración carcinomatosa. En nuestros casos y en los pocos casos encontrados en la bibliografía parece que la irritación crónica del LCR y la existencia de células multipotenciales en el saco meningocélico pueden favorecer la malignización de los tejidos que recubren el mismo. La posible malignización descrita en la escasa literatura existente, a la que aportamos nuestros dos casos, sugiere como tratamiento de elección la exéresis quirúrgica de estas lesiones congénitas lo más precozmente posible (AU)

A giant meningocelic sac has not been usually described in adult patients, due to the fact that it shows a low incidence and few newborn have survived to date though the malformation is benign. We report two cases of patients born with the described malformation and who were not operated at that time, so they reached adulthood with bigger sacs. They needed surgery to remove the sacs, for a different reason. The older one had a fistulous abcess but the LCR did not come out, and it did not improved by the application of topic and antibiotic treatment. The other patient showed a progressive growth of the malformation during the last year, skin hardening and pain. The histological study of the dried sacs proved the existence of a carcinomatous degeneration. In the patients we have treated, it seems that a chronic irritation of the LCR and the appearance of multipotent cells in the meningocele may favour the malignancy of the tissues surrounding the sac. This possible malignancy, already described in the bibliography, suggests a prompt elective surgical treatment of the patients with these congenital lesions as soon as possible (AU)

Autosomal dominant congenital non-progressive ataxia overlaps with the SCA15 locus.

BACKGROUND: Most patients with pure nonprogressive congenital cerebellar ataxia have a sporadic form of unknown heredity and etiology. Several small families have been reported with a dominantly inherited nonprogressive congenital ataxia (NPCA). METHODS: The authors ascertained and clinically characterized a four-generation pedigree segregating an autosomal dominant type of congenital nonprogressive cerebellar ataxia associated with cognitive impairment. Following the exclusion of several SCA localizations (SCA-1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 17, IOSCA, and DRPLA), a genome-wide linkage study was performed. RESULTS: Examination of the family showed that all affected members had gait ataxia and cognitive disability with variable features of dysarthria, dysmetria, dysdiadochokinesia, nystagmus, dystonic movements, and cerebellar hypoplasia on imaging. Clinical signs of pyramidal tract dysfunction and sensory changes were absent. A genome-wide search in this family detected linkage to chromosome 3p with a maximum two-point lod score of 4.26 at D3S3630. This localization to the pter is distal to D3S1304, as defined by a recombination event. This overlaps with the SCA15 locus, with the critical overlapping region between the microsatellite markers, D3S1304 and D3S1620 (approximately 8 cM). CONCLUSION: Autosomal dominant congenital nonprogressive cerebellar ataxia with or without cerebellar hypoplasia overlaps with the SCA15 locus on chromosome 3pter.

Combined congenital deficiencies of intrinsic factor and R binder.

Coexisting deficiencies of both intrinsic factor (IF) and R binder were identified in an Algerian boy who presented with severe megaloblastic anemia, growth retardation, and neurologic dysfunction with typical features of subacute combined degeneration of the spinal cord. The anemia responded completely to cyanocobalamin and folic acid. IF was absent from gastric juice, but acid secretion and gastric mucosa were normal. R binders were absent from gastric juices as well as from serum, saliva, and polymorphonuclear leukocytes. The patient's father exhibited absence of R binder in his serum with a low serum vitamin B12 level and was asymptomatic. This unique case of simultaneous IF and R binder deficiencies suggests a genetic association between these two functionally and immunologically dissimilar, but structurally close vitamin B12-binding proteins.

Neocerebellar hypoplasia with systemic combined olivo-ponto-dentatal degeneration in a 9-day-old baby: contribution to the problem of relations between malformation and systemic degeneration in early life.

Three different cerebral alterations, apparently formed consecutively, were observed in a 9-day-old baby. Marked cortico-neocerebellar hypoplasia was seen in a relatively well-developed paleocortex. Its teratological stage was apparently the 3rd fetal month. Almost total nerve cell loss and marked proliferation of protoplasmic and fibrous astrocytes were found in the nuclei pontis and inferior olive. Perihypoglossal and pararaphal nuclei, which are related to the cerebellum, were also affected. This degenerative process must have resulted from neuronal deprivation or inactivity, as the pertinent cortico-cerebellar area was hypoplastic, and therefore any neuronal imput was impossible (olivo-ponto-dentatal degeneration due to cortico-cerebellar hypoplasia). Massive symmetrical necrosis in the cerebral white and grey matter, basal ganglia, midbrain and bulbus, is interpreted as hypoxic damage due to perinatal convulsive attacks and cessation of respiration.