Spinal muscular atrophy (SMA) is an autosomal recessive disorder that is the leading genetic cause of infantile death. SMA is characterized by loss of motor neurons in the ventral horn of the spinal ...cord, leading to weakness and muscle atrophy. SMA occurs as a result of homozygous deletion or mutations in Survival Motor Neuron‐1 (SMN1). Loss of SMN1 leads to a dramatic reduction in SMN protein, which is essential for motor neuron survival. SMA disease severity ranges from extremely severe to a relatively mild adult onset form of proximal muscle atrophy. Severe SMA patients typically die mostly within months or a few years as a consequence of respiratory insufficiency and bulbar paralysis. SMA is widely known as a motor neuron disease; however, there are numerous clinical reports indicating the involvement of additional peripheral organs contributing to the complete picture of the disease in severe cases. In this review, we have compiled clinical and experimental reports that demonstrate the association between the loss of SMN and peripheral organ deficiency and malfunction. Whether defective peripheral organs are a consequence of neuronal damage/muscle atrophy or a direct result of SMN loss will be discussed.
Pontocerebellar hypoplasia Rudnik-Schöneborn, Sabine; Barth, Peter G.; Zerres, Klaus
American journal of medical genetics. Part C, Seminars in medical genetics,
June 2014, Letnik:
166C, Številka:
2
Journal Article
In contrast to most European countries, genetic counseling in Austria, Germany, and German‐speaking Switzerland is exclusively carried out by medical doctors. In this study, we investigate the ...perspectives of key clinician stakeholders in Austrian genetics services regarding prerequisites, opportunities, and challenges of implementing master's trained genetic counselors. Semi‐structured interviews with open‐ended questions and thematic analysis were carried out with nine participants, mostly medical geneticists at different hierarchy levels from three Centers for Medical Genetics in Austria. Several Austrian medical geneticists strongly object to the implementation of non‐physician genetic counselors, and representatives of 3/6 medical genetic centers declined to be interviewed. Semantic framing was identified as a critical factor: In German medical language, patient consultations carried out by medical geneticists are generally called ‘Genetische Beratung’ (genetic counseling), and many medical geneticists see themselves primarily as ‘Genetische Berater’ (genetic counselors). ‘Genetic counseling’ is specified as an exclusively medical task in Austrian law. There is apprehension that the introduction of non‐physician genetic counselors could reduce quality and undermine the position of medical genetics as a clinical specialty. The situation in Austria resembles that in Germany. Our study highlights the need for a clear definition of roles, expertise, and scope of practice of different genetic professionals. The integration of genetic counselors into Austrian genetics services is most likely acceptable in multi‐professional teams, closely affiliated with medical genetic services, and under the medico‐legal oversight of medical geneticists.
The joint occurrence of short stature, congenital dislocation of the hip, carpal coalition, dislocation of the radial head, cavus deformity, scoliosis, and vertebral anomalies was first described in ...1993 by Steel et al. (OMIM #615155) in 23 children from Puerto Rico. The condition is caused by a deficient matrix protein, collagen type XXVII alpha 1 chain, due to bi‐allelic loss of function mutations in the gene COL27A1. Outside of Puerto Rico, only four families have been described, in three of which the patients also had hearing loss. However, structural eye defects have not yet been reported in conjunction with this rare autosomal recessive syndrome. Here, we describe a 9‐year‐old girl born to nonconsanguineous Syrian parents with the characteristic features of Steel syndrome, including short stature, massive malalignment of large joints, kyphoscoliosis, hearing loss, and typical facial dysmorphism. However, she was also born with bilateral colobomata of the irides and choroido‐retinae with unilateral affection of the macula. Whole exome sequencing identified two pathogenic compound heterozygous variants in COL27A1: c.93del, p.(Phe32Leufs*71) and c.3075del, p.(Lys1026Argfs*33). There was no discernible alternative cause for the colobomata. Our findings might indicate an association of this exceptionally rare disorder caused by COL27A1 mutations with developmental defects of the eye from the anophthalmia/microphthalmia/coloboma spectrum.
Tuberous sclerosis complex (TSC) is an autosomal dominant neurocutaneous syndrome caused by either TSC1 or TSC2 gene mutations. About 15% of TSC patients remain without genetic diagnosis by ...conventional analysis despite clinical evidence. It is important to identify somatic mosaics, as therapeutic options are now available in patients with TSC1 or TSC2 mutations. Here, we describe the clinical and genetic characteristics of four male TSC patients with low‐level mosaicism. Patients presented at ages between 9 months and 32 years. Clinical manifestations varied considerably and included brain lesions in all four patients, cardiac rhabdomyomas in two young patients, skin involvement in two patients, and retinal hamartomas and renal angiomyolipomas in three patients. One patient presented with epileptic seizures and psychomotor delay. Low levels of mosaicism for TSC1 or TSC2 mutation were found in different tissue samples employing next generation sequencing and multiple ligation‐dependent probe amplification. The five disease‐associated variants, including one second‐hit mutation, include three truncating mutations and one deletion in TSC2, and one truncating mutation in TSC1. Sanger sequencing, allele‐specific oligonucleotide PCR (ASO‐PCR), and droplet digital PCR were used to confirm and quantify the disclosed mutations. Genetic identification of low‐level mosaicism for TSC remains challenging but is important for optimal surveillance and management.
Infantile spinal muscular atrophy (SMA) caused by homozygous SMN1 gene deletions/mutations is characterized by neuronal loss and axonopathy of motor neurons. We report two unrelated patients with ...severe SMA type I who had only one SMN2 copy and developed ulcerations and necroses of the fingers and toes. Sural nerve biopsy was normal in patient 1, whose affected skin displayed necroses and thrombotic occlusions of small vessels. Corresponding to a mouse model and other patients with similar findings, we believe that severe survival motor neuron (SMN) deficiency may present as vasculopathy. Muscle Nerve 42: 144–147, 2010
RNA exosomes are multi-subunit complexes conserved throughout evolution and are emerging as the major cellular machinery for processing, surveillance and turnover of a diverse spectrum of coding and ...noncoding RNA substrates essential for viability. By exome sequencing, we discovered recessive mutations in EXOSC3 (encoding exosome component 3) in four siblings with infantile spinal motor neuron disease, cerebellar atrophy, progressive microcephaly and profound global developmental delay, consistent with pontocerebellar hypoplasia type 1 (PCH1; MIM 607596). We identified mutations in EXOSC3 in an additional 8 of 12 families with PCH1. Morpholino knockdown of exosc3 in zebrafish embryos caused embryonic maldevelopment, resulting in small brain size and poor motility, reminiscent of human clinical features, and these defects were largely rescued by co-injection with wild-type but not mutant exosc3 mRNA. These findings represent the first example of an RNA exosome core component gene that is responsible for a human disease and further implicate dysregulation of RNA processing in cerebellar and spinal motor neuron maldevelopment and degeneration.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
PAN2 encodes a subunit of a deadenylation complex with important functions in mRNA stability and post-transcriptional regulation of gene expression. A homozygous frameshift deletion in PAN2 was ...reported in a single affected individual with developmental delay and multiple congenital anomalies. Here, we describe five additional individuals from three unrelated families with homozygous predicted loss-of-function variants in PAN2. The affected individuals presented with significant overlap in their clinical features, including mild-moderate intellectual disability, hypotonia, sensorineural hearing loss, EEG abnormalities, congenital heart defects (tetralogy of Fallot, septal defects, dilated aortic root), urinary tract malformations, ophthalmological anomalies, short stature with other skeletal anomalies, and craniofacial features including flat occiput, ptosis, long philtrum, and short neck. Our data confirm that biallelic predicted loss-of-function variants in PAN2 cause a syndrome with multiple congenital anomalies, and suggest an important role of mRNA polyA tail length for proper organ formation.
ABSTRACT
Introduction
Heterozygous BICD2 gene mutations cause a form of autosomal dominant spinal muscular atrophy with lower extremity predominance (SMALED).
Methods
We analyzed the BICD2 gene in a ...selected group of 25 index patients with neurogenic muscle atrophy.
Results
We identified 2 new BICD2 missense mutations, c.2515G>A, p.Gly839Arg, in a family with autosomal dominant inheritance, and c.2202G>T, p.Lys734Asn, as a de novo mutation in an isolated patient with similar phenotype. The patients had congenital foot contractures, muscle atrophy of the legs, and slowly progressive weakness of the shoulder girdle. There was no apparent sensory or brain dysfunction. One patient died of unrelated reasons at age 52 years. Autopsy revealed no upper motor neuron and only moderate lower motor neuron loss, but there was distal corticospinal tract degeneration and marked neurogenic muscular atrophy.
Conclusion
These findings give further insight into the clinical and pathoanatomical consequences of BICD2 mutations. Muscle Nerve 54: 496–500, 2016
Mutations in SACS, leading to autosomal-recessive spastic ataxia of Charlevoix-Saguenay (ARSACS), have been identified as a frequent cause of recessive early-onset ataxia around the world. Here we ...aimed to enlarge the spectrum of SACS mutations outside Quebec, to establish the pathogenicity of novel variants, and to expand the clinical and imaging phenotype.
Sequencing of SACS in 22 patients with unexplained early-onset ataxia, assessment of novel SACS variants in 3.500 European control chromosomes and extensive phenotypic investigations of all SACS carriers.
We identified 11 index patients harbouring 17 novel SACS variants. 9/11 patients harboured two variants of at least probable pathogenicity which were not observed in controls and, in case of missense mutations, were located in highly conserved domains. These 9 patients accounted for at least 11% (9/83) in our series of unexplained early onset ataxia subjects. While most patients (7/9) showed the classical ARSACS triad, the presenting phenotype reached from pure neuropathy (leading to the initial diagnosis of Charcot-Marie-Tooth disease) in one subject to the absence of any signs of neuropathy in another. In contrast to its name "spastic ataxia", neither spasticity (absent in 2/9=22%) nor extensor plantar response (absent in 3/9=33%) nor cerebellar ataxia (absent in 1/9=11%) were obligate features. Autonomic features included urine urge incontinence and erectile dysfunction. Apart from the well-established MRI finding of pontine hypointensities, all patients (100%) showed hyperintensities of the lateral pons merging into the (thickened) middle cerebellar peduncles. In addition, 63% exhibited bilateral parietal cerebral atrophy, and 63% a short circumscribed thinning of the posterior midbody of the corpus callosum. In 2 further patients with differences in important clinical features, VUS class 3 variants (c.1373C>T p.Thr458Ile and c.2983 G>T p.Val995Phe) were identified. These variants were, however, also observed in controls, thus questioning their pathogenic relevance.
We here demonstrate that each feature of the classical ARSACS triad (cerebellar ataxia, spasticity and peripheral neuropathy) might be missing in ARSACS. Nevertheless, characteristic MRI features - which also extend to supratentorial regions and involve the cerebral cortex - will help to establish the diagnosis in most cases.
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