The clinical and mutational spectrum of B3GAT3 linkeropathy : two case reports and literature review

Background: Proteoglycans are large and structurally complex macromolecules which can be found in abundancy in the extracellular matrix and on the surface of all animal cells. Mutations in the genes encoding the enzymes responsible for the formation of the tetrasaccharide linker region between the proteoglycan core protein and the glycosaminoglycan side chains lead to a spectrum of severe and overlapping autosomal recessive connective tissue disorders, collectively coined the glycosaminoglycan linkeropathies'. Results: We report the clinical findings of two novel patients with a complex linkeropathy due to biallelic mutations in B3GAT3, the gene that encodes glucuronosyltransferase I, which catalyzes the addition of the ultimate saccharide to the linker region. We identified a previously reported c.667G>A missense mutation and an unreported homozygous c.416C>T missense mutation. We also performed a genotype and phenotype-oriented literature overview of all hitherto reported patients harbouring B3GAT3 mutations. A total of 23 patients from 10 families harbouring bi-allelic mutations and one patient with a heterozygeous splice-site mutation in B3GAT3 have been reported. They all display a complex phenotype characterized by consistent presence of skeletal dysplasia (including short stature, kyphosis, scoliosis and deformity of the long bones), facial dysmorphology, and spatulate distal phalanges. More variably present are cardiac defects, joint hypermobility, joint dislocations/contractures and fractures. Seven different B3GAT3 mutations have been reported, and although the number of patients is still limited, some phenotype-genotype correlations start to emerge. The more severe phenotypes seem to have mutations located in the substrate acceptor subdomain of the catalytic domain of the glucuronosyltransferase I protein while more mildly affected phenotypes seem to have mutations in the NTP-sugar donor substrate binding subdomain. Conclusions: Loss-of-function mutations in B3GAT3 are associated with a complex connective tissue phenotype characterized by disproportionate short stature, skeletal dysplasia, facial dysmorphism, spatulate distal phalanges and -to a lesser extent- joint contractures, joint hypermobility with dislocations, cardiac defects and bone fragility. Based on the limited number of reported patients, some genotype-phenotype correlations start to emerge

Case Report: Retracing Atypical Development: A Preserved Speech Variant of Rett Syndrome

The subject of the present study is the development of a girl with the preserved speech variant of Rett disorder. Our data are based on detailed retrospective and prospective video analyses. Despite achieving developmental milestones, movement quality was already abnormal during the girl's first half year of life. In addition, early hand stereotypies, idiosyncratic vocalizations, asymmetric eye opening, and abnormal facial expressions are early signs proving that this variant of the Rett complex, too, manifests itself within the first months of life

Novel patients with NHLRC2 variants expand the phenotypic spectrum of FINCA disease

PurposeFINCA disease (Fibrosis, Neurodegeneration and Cerebral Angiomatosis, OMIM 618278) is an infantile-onset neurodevelopmental and multiorgan disease. Since our initial report in 2018, additional patients have been described. FINCA is the first human disease caused by recessive variants in the highly conserved NHLRC2 gene. Our previous studies have shown that Nhlrc2-null mouse embryos die during gastrulation, indicating the essential role of the protein in embryonic development. Defect in NHLRC2 leads to cerebral neurodegeneration and severe pulmonary, hepatic and cardiac fibrosis. Despite having a structure suggestive of an enzymatic role and the clinical importance of NHLRC2 in multiple organs, the specific physiological role of the protein is unknown.MethodsThe clinical histories of five novel FINCA patients diagnosed with whole exome sequencing were reviewed. Segregation analysis of the biallelic, potentially pathogenic NHLRC2 variants was performed using Sanger sequencing. Studies on neuropathology and NHLRC2 expression in different brain regions were performed on autopsy samples of three previously described deceased FINCA patients.ResultsOne patient was homozygous for the pathogenic variant c.442G > T, while the other four were compound heterozygous for this variant and two other pathogenic NHLRC2 gene variants. All five patients presented with multiorgan dysfunction with neurodevelopmental delay, recurrent infections and macrocytic anemia as key features. Interstitial lung disease was pronounced in infancy but often stabilized. Autopsy samples revealed widespread, albeit at a lower intensity than the control, NHLRC2 expression in the brain.ConclusionThis report expands on the characteristic clinical features of FINCA disease. Presentation is typically in infancy, and although patients can live to late adulthood, the key clinical and histopathological features are fibrosis, infection susceptibility/immunodeficiency/intellectual disability, neurodevelopmental disorder/neurodegeneration and chronic anemia/cerebral angiomatosis (hence the acronym FINCA) that enable an early diagnosis confirmed by genetic investigations

Abstracts from the 20th International Symposium on Signal Transduction at the Blood-Brain Barriers

https://deepblue.lib.umich.edu/bitstream/2027.42/138963/1/12987_2017_Article_71.pd

TATK-CDKL5 FUSION PROTEINS, COMPOSITIONS, FORMULATIONS, AND USE THEREOF

Disclosed herein are compositions and formulations containing a TATk-CDKL5 fusion protein. Also disclosed are methods of producing a TATk-CDKL5 fusion protein from vectors containing a TATk-CDKL5 cDNA and methods of transducing cells with the vectors containing a TATk-CDKL5 cDNA and the TATk-CDKL5 fusion protei

A Recurrent Expansion of a Maternal Allele with 36 CAG Repeats Causes Huntington Disease in Two Sisters

Large intergenerational repeat expansions of the CAG trinucleotide repeat in the HD gene have been well documented for the male germline. We describe a recurrent large expansion of a maternal allele with 36 CAG repeats (to 66 and 57 repeats, respectively, in two daughters) associated with onset of Huntington disease (HD) in the second and third decade in a family without history of HD. Our findings give evidence of a gonadal mosaicism in the unaffected mother. We hypothesize that large expansions also occur in the female germline and that a negative selection of oocytes with long repeats might explain the different instability behavior of the male and the female germlines

Identification and molecular characterisation of a homozygous missense mutation in the ADAMTS10 gene in a patient with Weill-Marchesani syndrome

Weill-Marchesani syndrome is a rare disorder of the connective tissue. Functional variants in ADAMTS10 are associated with Weill-Marchesani syndrome-1. We identified a homozygous missense mutation, c.41T>A, of the ADAMTS10 gene in a 19-year-old female with typical symptoms of WMS1: proportionate short stature, brachydactyly, joint stiffness, and microspherophakia. The ADAMTS10 missense mutation was analysed in silico, with conflicting results as to its effects on protein function, but it was predicted to affect the leader sequence. Molecular characterisation in HEK293 Ebna cells revealed an intracellular mis-targeting of the ADAMTS10 protein with a reduced concentration of the polypeptide in the endoplasmic reticulum. A large reduction in glycosylation of the cytoplasmic fraction of the mutant ADAMTS10 protein versus the wild-type protein and a lack of secretion of the mutant protein are also evident in our results.In conclusion, we identified a novel missense mutation of the ADAMTS10 gene and confirmed the functional consequences suggested by the in silico analysis by conducting molecular studies

Autosomal dominant Carvajal plus syndrome due to the novel desmoplakin mutation c.1678A > T (p.Ile560Phe)

Carvajal syndrome is an autosomal dominant or autosomal recessive disorder, manifesting with dilated cardiomyopathy, woolly hair, and palmoplantar keratoma. Additional manifestations can be occasionally found. Carvajal syndrome may be due to mutations in the desmocollin-2, desmoplakin, or plakophilin-2 gene. We report a family with Carvajal syndrome which additionally presented with hypoacusis, noncompaction, recurrent pharyngeal infections, oligodontia, and recurrent diarrhoea. Father and brother were also affected and had died suddenly, the father despite implantation of a cardioverter defibrillator (ICD). Genetic studies revealed the novel pathogenic mutation c.1678A > T in the desmoplakin gene resulting in the amino acid change Ile to Phe at position 560 in the index case and her brother. The index case underwent ICD implantation recently. Phenotypic manifestations of Carvajal syndrome are even broader than so far anticipated, the number of mutations in the desmoplakin gene responsible for Carvajal syndrome is still increasing, and these patients require implantation of an ICD as soon as their diagnosis is established