'Costa da Morte' ataxia is spinocerebellar ataxia 36: clinical and genetic characterization.

Spinocerebellar ataxia 36 has been recently described in Japanese families as a new type of spinocerebellar ataxia with motor neuron signs. It is caused by a GGCCTG repeat expansion in intron 1 of NOP56. Family interview and document research allowed us to reconstruct two extensive, multigenerational kindreds stemming from the same village (Costa da Morte in Galicia, Spain), in the 17th century. We found the presence of the spinocerebellar ataxia 36 mutation co-segregating with disease in these families in whom we had previously identified an ~0.8 Mb linkage region to chromosome 20 p. Subsequent screening revealed the NOP56 expansion in eight additional Galician ataxia kindreds. While normal alleles contain 5-14 hexanucleotide repeats, expanded alleles range from ~650 to 2500 repeats, within a shared haplotype. Further expansion of repeat size was frequent, especially upon paternal transmission, while instances of allele contraction were observed in maternal transmissions. We found a total of 63 individuals carrying the mutation, 44 of whom were confirmed to be clinically affected; over 400 people are at risk. We describe here the detailed clinical picture, consisting of a late-onset, slowly progressive cerebellar syndrome with variable eye movement abnormalities and sensorineural hearing loss. There were signs of denervation in the tongue, as well as mild pyramidal signs, but otherwise no signs of classical amyotrophic lateral sclerosis. Magnetic resonance imaging findings were consistent with the clinical course, showing atrophy of the cerebellar vermis in initial stages, later evolving to a pattern of olivo-ponto-cerebellar atrophy. We estimated the origin of the founder mutation in Galicia to have occurred ~1275 years ago. Out of 160 Galician families with spinocerebellar ataxia, 10 (6.3%) were found to have spinocerebellar ataxia 36, while 15 (9.4%) showed other of the routinely tested dominant spinocerebellar ataxia types. Spinocerebellar ataxia 36 is thus, so far, the most frequent dominant spinocerebellar ataxia in this region, which may have implications for American countries associated with traditional Spanish emigration.

Severe congenital X-linked myopathy with excessive autophagy secondary to an apparently synonymous but pathogenic novel variant.

X-linked myopathy with excessive autophagy is a rare inherited disease characterized by aberrant accumulation of autophagic vacuoles in skeletal muscle. Affected males usually show a slow progression and the heart is characteristically spared. We present four male patients from the same family with an extremely aggressive form of this disease, requiring permanent mechanical ventilation from birth. Ambulation was never achieved. Three died, one in the first hour of life, one at 7 years and one at 17 years, the last death being a consequence of heart failure. Muscle biopsy showed pathognomonic features of the disease in the 4 affected males. Genetic study found a novel synonymous variant in VMA21, c.294C>T (Gly98=). Genotyping was consistent with co-segregation with the phenotype in an X-linked recessive manner. An alteration of the normal splice pattern was confirmed by transcriptome analysis, proving that the apparently synonymous variant was the cause of this extremely severe phenotype.

Axonal neuropathy, long limbs and bumpy tongue: think of MEN2B.

INTRODUCTION: Multiple endocrine neoplasia type 2 (MEN 2) is an uncommon autosomal dominant cancer syndrome which can be associated with nerve conduction abnormalities. METHODS: A 14-year-old boy with a family history of consanguinity developed progressive gait clumsiness, pes cavus, hypotonia, and mucosal tumors of the lips and tongue since the age of 3 years. At age 11 years, he was diagnosed with an hereditary motor neuropathy (Charcot-Marie-Tooth syndrome). RESULTS: Physical examination revealed a Marfanoid habitus, mucocutaneous verrucous tumors, thyroid nodules, and cervical adenopathy. Genetic testing demonstrated the p.M918T mutation in the RET gene, and blood tests showed elevated levels of calcitonin. CONCLUSIONS: Clinical suspicion in MEN2 is crucial for early diagnosis and subsequent therapy. Mucosal neuroma and a Marfanoid habitus are especially useful. Other neurologic manifestations should not disguise the endocrine disorder, because early diagnosis and treatment of medullary thyroid carcinoma determines the prognosis.

A C-terminal mutation of ATP1A3 underscores the crucial role of sodium affinity in the pathophysiology of rapid-onset dystonia-parkinsonism.

The Na(+)/K(+)-ATPases are ion pumps of fundamental importance in maintaining the electrochemical gradient essential for neuronal survival and function. Mutations in ATP1A3 encoding the alpha3 isoform cause rapid-onset dystonia-parkinsonism (RDP). We report a de novo ATP1A3 mutation in a patient with typical RDP, consisting of an in-frame insertion of a tyrosine residue at the very C terminus of the Na(+)/K(+)-ATPase alpha3-subunit-the first reported RDP mutation in the C terminus of the protein. Expression studies revealed that there is no defect in the biogenesis or plasma membrane targeting, although cells expressing the mutant protein showed decreased survival in response to ouabain challenge. Functional analysis demonstrated a drastic reduction in Na(+) affinity in the mutant, which can be understood by structural modelling of the E1 and E2 conformations of the wild-type and mutant enzymes on the basis of the strategic location of the C terminus in relation to the third Na(+) binding site. The dramatic clinical presentation, together with the biochemical findings, provides both in vivo and in vitro evidence for a crucial role of the C terminus of the alpha-subunit in the function of the Na(+)/K(+)-ATPase and a key impact of Na(+) affinity in the pathophysiology of RDP.

Phenotypical features of a new dominant GDAP1 pathogenic variant (p.R226del) in axonal Charcot-Marie-Tooth disease.

There are few reports on axonal CMT due to dominant GDAP1 mutations. We describe two unrelated Spanish families with a dominant axonal CMT. A novel in frame GAA deletion in exon 5 of the GDAP1 gene (c.677_679del; p.R226del) was identified in both families. Disease onset varied from early childhood to adulthood. Affected family members complained of distal lower limb weakness, cramps and foot deformities with variable CMTNS score in both families. Several individuals were asymptomatic or had paraesthesia only, however neurological examination and nerve conduction studies demonstrated neuropathic signs. Transfection of HeLa cells with the p.R226del mutation led to an increased mitochondrial aggregation. We report an AD-CMT2K with large phenotypic variability due to a novel dominant GDAP1 variant. This is the second founder GDAP1 pathogenic variant reported in Spain.

Distribution and genotype-phenotype correlation of GDAP1 mutations in Spain.

Mutations in the GDAP1 gene can cause Charcot-Marie-Tooth disease. These mutations are quite rare in most Western countries but not so in certain regions of Spain or other Mediterranean countries. This cross-sectional retrospective multicenter study analyzed the clinical and genetic characteristics of patients with GDAP1 mutations across Spain. 99 patients were identified, which were distributed across most of Spain, but especially in the Northwest and Mediterranean regions. The most common genotypes were p.R120W (in 81% of patients with autosomal dominant inheritance) and p.Q163X (in 73% of autosomal recessive patients). Patients with recessively inherited mutations had a more severe phenotype, and certain clinical features, like dysphonia or respiratory dysfunction, were exclusively detected in this group. Dominantly inherited mutations had prominent clinical variability regarding severity, including 29% of patients who were asymptomatic. There were minor clinical differences between patients harboring specific mutations but not when grouped according to localization or type of mutation. This is the largest clinical series to date of patients with GDAP1 mutations, and it contributes to define the genetic distribution and genotype-phenotype correlation in this rare form of CMT.

Distinct phenotypic features and gender-specific disease manifestations in a Spanish family with desmin L370P mutation.

Desminopathies represent a subtype of myofibrillar myopathy caused by mutations in the DES gene, which cause myofibril disruption and intracellular inclusions containing desmin and other protein components. Desminopathy mainly involves skeletal and cardiac muscle, separately or together. Both autosomal dominant and autosomal recessive inheritance have been reported. Here, we describe the second family identified to date with an L370P desmin mutation. The disease in this family shows autosomal dominant inheritance with a particular phenotype, where males suffer from sudden death of cardiac origin while females exhibit a more benign myopathy of distal onset and slower progression. Because the only family previously identified with this mutation was limited to one studied patient, the present kindred represents the largest clinical investigation of the phenotype associated with the L370P mutation.

Targeted NGS meets expert clinical characterization: Efficient diagnosis of spastic paraplegia type 11.

Next generation sequencing (NGS) is transforming the diagnostic approach for neurological disorders, since it allows simultaneous analysis of hundreds of genes, even based on just a broad, syndromic patient categorization. However, such an approach bears a high risk of incidental and uncertain genetic findings. We report a patient with spastic paraplegia whose comprehensive neurological and imaging examination raised a high clinical suspicion of SPG11. Thus, although our NGS pipeline for this group of disorders includes gene panel and exome sequencing, in this sample only the spatacsin gene region was captured and subsequently searched for mutations. Two probably pathogenic variants were quickly and clearly identified, confirming the diagnosis of SPG11. This case illustrates how combination of expert clinical characterization with highly oriented NGS protocols leads to a fast, cost-efficient diagnosis, minimizing the risk of findings with unclear significance.

A novel MYH7 mutation links congenital fiber type disproportion and myosin storage myopathy.

This study aimed to identify the genetic defect in a multigenerational family presenting an autosomal dominant myopathy with histological features of congenital fiber type disproportion. Linkage analysis and genetic sequencing identified, in all affected members of the family, the c.5807A>G heterozygous mutation in MYH7, which encodes the slow/ß-cardiac myosin heavy chain. This mutation causes skeletal but not cardiac involvement. Myosin heavy chain expression pattern was also characterized by immunohistochemistry, western blot and q-PCR in muscle biopsies from two patients aged 25 and 62, respectively. While only congenital fiber type disproportion was observed in the younger patient, older patient's biopsy presented aggregates of slow myosin heavy chains, in fiber sub-sarcolemmal region. These clinico-pathologic findings suggest a novel phenotype within the emerging group of hereditary myosin myopathies, which in this family presents typical characteristics of congenital fiber type disproportion in early stages and later evolves to myosin storage myopathy.

A comparative analysis of the pig, mouse, and human PCDHX genes.

Protocadherin X and Y (PCDHX/Y) represent a pair of homologous genes located on the human sex chromosomes that are primarily expressed in the brain. PCDHY emerged as a result of a duplicative transposition from the X Chromosome (Chr) and is present on the Y only in hominids. Previous zoo-blot analysis suggested the existence of PCDHX orthologs on the X Chr of several mammalian species. This paper reports the cloning and characterization of porcine and murine Pcdhx. Pig Pcdhx cDNA was obtained by a combination of RT-PCR, SMART-RACE, and genomic sequencing and exhibits 88% identity to human PCDHX; FISH analysis indicated that porcine Pcdhx maps to Xq. Mouse Pcdhx cDNA was assembled by RT-PCR and database analysis and is 84% identical to the human gene. Some degree of alternative splicing was detected in pig Pcdhx, but not to the extent previously described in humans. Both murine and porcine Pcdhx mRNA were detected in all tissues studied. Cloning of 2.5 kb of genomic sequence upstream of the most 5' exon of porcine Pcdhx allowed a comparative analysis with murine and human sequences in order to define potential promoter elements. All exons present in mouse and pig transcripts were found to have homologous sequences in human DNA. Not all of these exons are represented in human transcripts, indicating differential evolution and usage. The increased complexity in post-transcriptional processing and restriction of expression of the human genes primarily to central nervous system tissue as compared with pig and mouse suggests that PCDHX/Y is potentially a good candidate to account for human-specific features of the CNS.

Protocadherin X ( PCDHX) and Y ( PCDHY) genes; multiple mRNA isoforms encoding variant signal peptides and cytoplasmic domains.

The gene-poor, hominid-specific Yp11.2/Xq21.3 X-Y homology block encodes two members of the protocadherin group of cell surface molecules, PCDHX and PCDHY. These two genes, mainly expressed in brain, were known to be composed of at least six exons sharing 98.1% DNA identity. The genomic structure of PCDHX/ Y has been reanalyzed in detail, uncovering the existence of at least 11 more exons spanning more than 700 kb. Many of these exons located at the 5' and 3' ends of PCDHX/ Y undergo differential and alternative splicing. Seven of the exons have been found to use alternative splice sites. Most of these variants are expressed within the brain, although some isoforms exhibit a more ubiquitous distribution pattern. PCDHX/ Y transcription appears to be driven from two alternative promoters located usptream of exon 1 and exon 4.1. Assuming that the splicing events at the 5' and 3' ends of these genes are independent of one another, potentially up to 360 different mRNAs could be produced. The main impact on protein function is predicted to be in the efficiency of translation, post-translational processing within the cell, and structure of the cytoplasmic domain that may influence any role the genes have in signaling.

The human-specific Yp11.2/Xq21.3 homology block encodes a potentially functional testis-specific TGIF-like retroposon.

Yp11.2/Xq21.3 is a human-specific homology block that constitutes the largest shared region among the sex chromosomes, spanning some 3.5 Mb. Only two transcribed sequences have been mapped to this segment: the protocadherin genes PCDHX/Y, and the X-linked poly(A)-binding protein PABPC5 gene, whose Y-homolog has been lost during human evolution. This paper reports the genomic structure, expression, and evolutionary conservation of a third (X-Y homologous) transcribed sequence, TGIFLX/Y (TGIF-like X/Y), mapping to this region. TGIFLX/Y has a 2666-bp mRNA encoded by two exons separated by a 96-bp intron. TGIFLX/Y are homeodomain-containing genes related to the TALE superclass gene family. Comparative DNA analysis indicates that TGIFLX originated from retrotransposition of TGIF2, located on 20q11.2-12, onto the X Chromosome. RT-PCR analysis reveals that both X- and Y-linked genes are specifically expressed in adult testis. Cloning and sequencing of TGIFLX homologs in hominoids and Old World monkeys provides evidence for an open reading frame in the eight species studied. Interestingly, a single base pair deletion in the human TGIFLY (as compared with TGIFLX) creates a different reading frame where the C-terminal residues shared by TGIFLX and other TGIF proteins are missing. The conservation, similarity to protein-encoding transcription factors, and specific expression in testis points to a transcriptional role for TGIFLX/Y in this tissue.

Estudio de un caso de hipoalbuminemia severa / A case study of severe hypoalbuminemia

La ataxia con apraxia oculomotora e hipoalbuminemia severa (AOA/EAOH) es una entidad rara que se caracteriza por un inicio temprano de ataxia cerebelosa de progreso lento, seguida por apraxia oculomotora y neuropatía periférica severa que lleva a la cuadriplejia. Pertenece al grupo de ataxias autsómocas recesivas (ARCA), siendo la de mayor frecuencia tras la ataxia de Friedreich, y la primera en población japonesa. El diagnóstico definitivo es mediante el estudio molecular del gen APTX que codifica para la aprataxina. Se presenta el caso de una mujer de 52 años, con síntomas y datos sugerentes desde la infancia que ha sido diagnosticada 30 años después (AU)

Ataxia with oculomotor apraxia and severe hypoalbuminemia (AOA/EAOH) is a rare entity characterized by early onset of slowly progressive cerebellar ataxia, followed by oculomotor apraxia and peripheral neuropathy leading to severe quadriplegia. AOA/EAOH belongs to the group of autosomal recessive ataxias, being the most frequent after Friedreich's ataxia. Definitive diagnosis provided by identification of mutations in the APTX gene encoding aprataxin. This case study of a 52 year-old woman with childhood onset of the disease, suggested by symptoms and several additional findings, who has been diagnosed 30 years later (AU)