p21-activated kinases (PAKs) are serine/threonine protein kinases acting as effectors of CDC42 and RAC, which are members of the RHO family of small GTPases. PAK1’s kinase activity is autoinhibited ...by homodimerization, whereas CDC42 or RAC1 binding causes PAK1 activation by dimer dissociation. Major functions of the PAKs include actin cytoskeleton reorganization, for example regulation of the cellular protruding activity during cell spreading. We report the de novo PAK1 mutations c.392A>G (p.Tyr131Cys) and c.1286A>G (p.Tyr429Cys) in two unrelated subjects with developmental delay, secondary macrocephaly, seizures, and ataxic gait. We identified enhanced phosphorylation of the PAK1 targets JNK and AKT in fibroblasts of one subject and of c-JUN in those of both subjects compared with control subjects. In fibroblasts of the two affected individuals, we observed a trend toward enhanced PAK1 kinase activity. By using co-immunoprecipitation and size-exclusion chromatography, we observed a significantly reduced dimerization for both PAK1 mutants compared with wild-type PAK1. These data demonstrate that the two PAK1 variants function as activating alleles. In a cell spreading assay, subject-derived fibroblasts showed significant enrichment in cells occupied by filopodia. Interestingly, application of the PAK1 inhibitor FRAX486 completely reversed this cellular phenotype. Together, our data reveal that dominantly acting, gain-of-function PAK1 mutations cause a neurodevelopmental phenotype with increased head circumference, possibly by a combined effect of defective homodimerization and enhanced kinase activity of PAK1. This condition, along with the developmental disorders associated with RAC1 and CDC42 missense mutations, highlight the importance of RHO GTPase members and effectors in neuronal development.
Abstract
Background
Life extension by medical interventions and health-related quality of life (HRQOL) are sometimes conflicting aspects of medical care. Long-term ventilation in children with ...neuromuscular disease is a well-established life-extending procedure and often at the center of this conflict. HRQOL and the mental health of affected children and their families become even more important in respect to emerging therapies in neuromuscular diseases with longer life-expectancy of treated patients and considerable costs of medical treatment.
Methods
We performed a questionnaire survey in a total of forty-three families of children with neuromuscular disease treated in the University Medical Center Hamburg-Eppendorf and the Children’s Hospital Altona. We evaluated self- and proxy-reported HRQOL and mental health outcomes of affected children and their parents using validated and age-appropriate instruments.
Results
Compared to normative data, children with neuromuscular diseases and their families experienced a lower HRQOL and mental health. However, there was no additional negative influence on the overall HRQOL by ventilator use.
Conclusions
As ventilator use was not responsible for the reduction of HRQOL and mental health our data contributes an important aspect to the discussion about life-prolonging procedures, in particular mechanical ventilation, in severly disabled patients.
Dysfunction of the endolysosomal system is often associated with neurodegenerative disease because postmitotic neurons are particularly reliant on the elimination of intracellular aggregates. ...Adequate function of endosomes and lysosomes requires finely tuned luminal ion homeostasis and transmembrane ion fluxes. Endolysosomal CLC Cl−/H+ exchangers function as electric shunts for proton pumping and in luminal Cl− accumulation. We now report three unrelated children with severe neurodegenerative disease, who carry the same de novo c.1658A>G (p.Tyr553Cys) mutation in CLCN6, encoding the late endosomal Cl−/H+-exchanger ClC-6. Whereas Clcn6−/− mice have only mild neuronal lysosomal storage abnormalities, the affected individuals displayed severe developmental delay with pronounced generalized hypotonia, respiratory insufficiency, and variable neurodegeneration and diffusion restriction in cerebral peduncles, midbrain, and/or brainstem in MRI scans. The p.Tyr553Cys amino acid substitution strongly slowed ClC-6 gating and increased current amplitudes, particularly at the acidic pH of late endosomes. Transfection of ClC-6Tyr553Cys, but not ClC-6WT, generated giant LAMP1-positive vacuoles that were poorly acidified. Their generation strictly required ClC-6 ion transport, as shown by transport-deficient double mutants, and depended on Cl−/H+ exchange, as revealed by combination with the uncoupling p.Glu200Ala substitution. Transfection of either ClC-6Tyr553Cys/Glu200Ala or ClC-6Glu200Ala generated slightly enlarged vesicles, suggesting that p.Glu200Ala, previously associated with infantile spasms and microcephaly, is also pathogenic. Bafilomycin treatment abrogated vacuole generation, indicating that H+-driven Cl− accumulation osmotically drives vesicle enlargement. Our work establishes mutations in CLCN6 associated with neurological diseases, whose spectrum of clinical features depends on the differential impact of the allele on ClC-6 function.
Canavan disease (CD, MIM # 271900) is a rare and devastating leukodystrophy of early childhood. To identify clinical features that could serve as endpoints for treatment trials, the clinical course ...of CD was studied retrospectively and prospectively in 23 CD patients. Results were compared with data of CD patients reported in three prior large series. Kaplan Meier survival analysis including log rank test was performed for pooled data of 82 CD patients (study cohort and literature patients).
Onset of symptoms was between 0 and 6 months. Psychomotor development of patients was limited to abilities that are usually gained within the first year of life. Macrocephaly became apparent between 4 and 18 months of age. Seizure frequency was highest towards the end of the first decade. Ethnic background was more diverse than in studies previously reported. A CD severity score with assessment of 11 symptoms and abilities was developed.
Early hallmarks of CD are severe psychomotor disability and macrocephaly that develop within the first 18 months of life. While rare in the first year of life, seizures increase in frequency over time in most patients. CD occurs more frequently outside Ashkenazi Jewish communities than previously reported. Concordance of phenotypes between siblings but not patients with identical ASPA mutations suggest the influence of yet unknown modifiers. A CD severity score may allow for assessment of CD disease severity both retrospectively and prospectively.
Congenital dyserythropoietic anemias (CDAs) are phenotypically and genotypically heterogeneous diseases. CDA type II (CDAII) is the most frequent CDA. It is characterized by ineffective ...erythropoiesis and by the presence of bi- and multinucleated erythroblasts in bone marrow, with nuclei of equal size and DNA content, suggesting a cytokinesis disturbance. Other features of the peripheral red blood cells are protein and lipid dysglycosylation and endoplasmic reticulum double-membrane remnants. Development of other hematopoietic lineages is normal. Individuals with CDAII show progressive splenomegaly, gallstones and iron overload potentially with liver cirrhosis or cardiac failure. Here we show that the gene encoding the secretory COPII component SEC23B is mutated in CDAII. Short hairpin RNA (shRNA)-mediated suppression of SEC23B expression recapitulates the cytokinesis defect. Knockdown of zebrafish sec23b also leads to aberrant erythrocyte development. Our results provide in vivo evidence for SEC23B selectivity in erythroid differentiation and show that SEC23A and SEC23B, although highly related paralogous secretory COPII components, are nonredundant in erythrocyte maturation.
The MCM2-7 helicase is a heterohexameric complex with essential roles as part of both the pre-replication and pre-initiation complexes in the early stages of DNA replication. Meier-Gorlin syndrome, a ...rare primordial dwarfism, is strongly associated with disruption to the pre-replication complex, including a single case described with variants in MCM5. Conversely, a biallelic pathogenic variant in MCM4 underlies immune deficiency with growth retardation, features also seen in individuals with pathogenic variants in other pre-initiation complex encoding genes such as GINS1, MCM10, and POLE. Through exome and chromium genome sequencing, supported by functional studies, we identify biallelic pathogenic variants in MCM7 and a strong candidate biallelic pathogenic variant in MCM3. We confirm variants in MCM7 are deleterious and through interfering with MCM complex formation, impact efficiency of S phase progression. The associated phenotypes are striking; one patient has typical Meier-Gorlin syndrome, whereas the second case has a multi-system disorder with neonatal progeroid appearance, lipodystrophy and adrenal insufficiency. We provide further insight into the developmental complexity of disrupted MCM function, highlighted by two patients with a similar variant profile in MCM7 but disparate clinical features. Our results build on other genetic findings linked to disruption of the pre-replication and pre-initiation complexes, and the replisome, and expand the complex clinical genetics landscape emerging due to disruption of DNA replication.
Bain type of X-linked syndromic intellectual developmental disorder, caused by pathogenic missense variants in
HRNRPH2
, was initially described in six female individuals affected by ...moderate-to-severe neurodevelopmental delay. Although it was initially postulated that the condition would not be compatible with life in males, several affected male individuals harboring pathogenic variants in
HNRNPH2
have since been documented. However, functional in-vitro analyses of identified variants have not been performed and, therefore, possible genotype–phenotype correlations remain elusive. Here, we present eight male individuals, including a pair of monozygotic twins, harboring pathogenic or likely pathogenic
HNRNPH2
variants. Notably, we present the first individuals harboring nonsense or frameshift variants who, similarly to an individual harboring a de novo p.(Arg29Cys) variant within the first quasi-RNA-recognition motif (qRRM), displayed mild developmental delay, and developed mostly autistic features and/or psychiatric co-morbidities. Additionally, we present two individuals harboring a recurrent de novo p.(Arg114Trp), within the second qRRM, who had a severe neurodevelopmental delay with seizures. Functional characterization of the three most common
HNRNPH2
missense variants revealed dysfunctional nucleocytoplasmic shuttling of proteins harboring the p.(Arg206Gln) and p.(Pro209Leu) variants, located within the nuclear localization signal, whereas proteins with p.(Arg114Trp) showed reduced interaction with members of the large assembly of splicing regulators (LASR). Moreover, RNA-sequencing of primary fibroblasts of the individual harboring the p.(Arg114Trp) revealed substantial alterations in the regulation of alternative splicing along with global transcriptome changes. Thus, we further expand the clinical and variant spectrum in
HNRNPH2
-associated disease in males and provide novel molecular insights suggesting the disorder to be a spliceopathy on the molecular level.
Background Advances in genetic and pharmaceutical technology and pediatric care have enabled treatment options for an increasing number of rare diseases in affected children. However, as current ...treatment options are primarily of palliative nature, the Health-Related Quality of Life (HRQoL) and mental health of this impaired population and their siblings are of increasing importance. Among children and adolescents with rare diseases, those who are technology-dependent carry a high disease burden and are selected as the target population in our study. In a cross-sectional observational design, the children's HRQoL was assessed with the DISABKIDS (DCGM-37) as well as KIDSCREEN-27, while mental health was assessed with the Strengths and Difficulties Questionnaire (SDQ) by both the affected children, their parents, and siblings. Results Results of the study sample were compared to normative data. Affected children scored significantly lower than the norm on almost all HRQoL subscales as reported by parent and child. From the parental perspective, more mental health subscales were significantly impaired compared to the child's perspective. Siblings showed no impairment in HRQoL as well as significantly fewer behavioral problems and higher prosocial behavior regarding their mental health compared to the norm. Conclusion Children and adolescents with rare diseases seem particularly impaired in social and emotional aspects of HRQoL and mental health. Interventions may focus primarily on promoting social skills, fostering prosocial behavior and peer relationships. Keywords: Health-Related Quality of Life, Mental health, Technologically dependent, Siblings
Management strategies for CLN2 disease Williams, Ruth E., DM, FRCPCH; Adams, Heather R., PhD; Blohm, Martin, MD ...
Pediatric neurology,
04/2017, Letnik:
69
Journal Article
Recenzirano
Odprti dostop
Abstract CLN2 disease (neuronal ceroid lipofuscinosis type 2) is a rare, autosomal recessive, pediatric-onset, rapidly progressive neurodegenerative lysosomal storage disorder caused by TPP1 enzyme ...deficiency, and is characterized by language delay, seizures, rapid cognitive and motor decline, blindness and early death. No management guidelines exist and there is a paucity of published disease-specific evidence to inform clinical practice, which currently draws upon experience from the field of childhood neurodisability. Twenty-four disease experts were surveyed on CLN2 disease management and a subset met to discuss current practice. Management goals and strategies are consistent among experts globally, and are guided by the principles of pediatric palliative care. Goals and interventions evolve as the disease progresses, with a shift in focus from maintenance of function early in the disease to maintenance of quality of life. A multidisciplinary approach is critical for optimal patient care. This work represents an initial step towards development of consensus-based management guidelines for CLN2 disease.
ANK3
encodes multiple isoforms of ankyrin-G, resulting in variegated tissue expression and function, especially regarding its role in neuronal development. Based on the zygosity, location, and type,
...ANK3
variants result in different neurodevelopmental phenotypes. Autism spectrum disorder has been associated with heterozygous missense variants in
ANK3
, whereas a more severe neurodevelopmental phenotype is caused by isoform-dependent, autosomal-dominant, or autosomal-recessive loss-of-function variants. Here, we present four individuals affected by a variable neurodevelopmental phenotype harboring a heterozygous frameshift or nonsense variant affecting all
ANK3
transcripts. Thus, we provide further evidence of an isoform-based phenotypic continuum underlying
ANK3
-associated pathologies and expand its phenotypic spectrum.
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