FRMPD4 mutations cause X-linked intellectual disability and disrupt dendritic spine morphogenesis.

FRMPD4 (FERM and PDZ Domain Containing 4) is a neural scaffolding protein that interacts with PSD-95 to positively regulate dendritic spine morphogenesis, and with mGluR1/5 and Homer to regulate mGluR1/5 signaling. We report the genetic and functional characterization of 4 FRMPD4 deleterious mutations that cause a new X-linked intellectual disability (ID) syndrome. These mutations were found to be associated with ID in ten affected male patients from four unrelated families, following an apparent X-linked mode of inheritance. Mutations include deletion of an entire coding exon, a nonsense mutation, a frame-shift mutation resulting in premature termination of translation, and a missense mutation involving a highly conserved amino acid residue neighboring FRMPD4-FERM domain. Clinical features of these patients consisted of moderate to severe ID, language delay and seizures alongside with behavioral and/or psychiatric disturbances. In-depth functional studies showed that a frame-shift mutation, FRMPD4p.Cys618ValfsX8, results in a disruption of FRMPD4 binding with PSD-95 and HOMER1, and a failure to increase spine density in transfected hippocampal neurons. Behavioral studies of frmpd4-KO mice identified hippocampus-dependent spatial learning and memory deficits in Morris Water Maze test. These findings point to an important role of FRMPD4 in normal cognitive development and function in humans and mice, and support the hypothesis that FRMPD4 mutations cause ID by disrupting dendritic spine morphogenesis in glutamatergic neurons.

Rare GABRA3 variants are associated with epileptic seizures, encephalopathy and dysmorphic features.

Genetic epilepsies are caused by mutations in a range of different genes, many of them encoding ion channels, receptors or transporters. While the number of detected variants and genes increased dramatically in the recent years, pleiotropic effects have also been recognized, revealing that clinical syndromes with various degrees of severity arise from a single gene, a single mutation, or from different mutations showing similar functional defects. Accordingly, several genes coding for GABAA receptor subunits have been linked to a spectrum of benign to severe epileptic disorders and it was shown that a loss of function presents the major correlated pathomechanism. Here, we identified six variants in GABRA3 encoding the α3-subunit of the GABAA receptor. This gene is located on chromosome Xq28 and has not been previously associated with human disease. Five missense variants and one microduplication were detected in four families and two sporadic cases presenting with a range of epileptic seizure types, a varying degree of intellectual disability and developmental delay, sometimes with dysmorphic features or nystagmus. The variants co-segregated mostly but not completely with the phenotype in the families, indicating in some cases incomplete penetrance, involvement of other genes, or presence of phenocopies. Overall, males were more severely affected and there were three asymptomatic female mutation carriers compared to only one male without a clinical phenotype. X-chromosome inactivation studies could not explain the phenotypic variability in females. Three detected missense variants are localized in the extracellular GABA-binding NH2-terminus, one in the M2-M3 linker and one in the M4 transmembrane segment of the α3-subunit. Functional studies in Xenopus laevis oocytes revealed a variable but significant reduction of GABA-evoked anion currents for all mutants compared to wild-type receptors. The degree of current reduction correlated partially with the phenotype. The microduplication disrupted GABRA3 expression in fibroblasts of the affected patient. In summary, our results reveal that rare loss-of-function variants in GABRA3 increase the risk for a varying combination of epilepsy, intellectual disability/developmental delay and dysmorphic features, presenting in some pedigrees with an X-linked inheritance pattern.

[Fragile X syndrome and FMR1-dependent diseases - diagnostic scheme based on own experience .]

The presence of dynamic mutation in the FMR1 gene localized on the X chromosome (Xq28) is the major cause of Fragile X syndrome. As this syndrome is quite frequently diagnosed in patients with intellectual disability and autism spectrum disorders, the genetic testing of the FMR1 gene is a routine procedure performed in these patients. Molecular methods based on the PCR technique are used commonly, as they allow to identify normal (up to 54 CGG repeats, including grey zone alleles - 45-54 CGG repeats), premutation (55-200 CGG repeats) and full mutation (>200 CGG repeats) alleles.The article presents the basic methods used in the molecular diagnosis of Fragile X syndrome and other FMR1-related disorders. The following methods are presented: a screening test with GeneScan analysis, TP-PCR based tests and methods used for methylation analysis. Their pros and cons, as well as the resulting interpretation are discussed. Moreover, there is a presentation of the molecular diagnostic scheme following European Molecular Genetics Quality Network guidelines used in the Department of Medical Genetics.

[Fragile X syndrome and FMR1-dependent diseases - clinical presentation, epidemiology and molecular background].

Fragile X syndrome (FXS) is the second most common inherited cause of intellectual disability (ID), after Down syndrome. The severity of ID in FXS patients varies and depends mainly on the patient's sex. Besides intellectual disorders, additional symptoms, such as psychomotor delay, a specific behavioral phenotype, or emotional problems are present in FXS patients. In over 99% of the cases, the disease is caused by the presence of a dynamic mutation in the FMR1 gene localized on the X chromosome. Due to the expansion of CGG nucleotides (over 200 repeats), FMR1 gene expression is decreased and results in the significant reduction of the FMRP protein level. The CGG expansion to premutation range (55-200 CGG repeats) is equivalent to the FXS carrier status and may cause FMR1-dependent disorders - fragile X-associated primary ovarian insufficiency (FXPOI) and fragile X-associated tremor/ataxia syndrome (FXTAS). In contrast to FXS, clinical symptoms of these diseases occur later in adulthood. The aim of the article is to present the knowledge about the molecular background and epidemiology of fragile X syndrome and other FMR1-related disorders.

[Non-invasive genetic prenatal diagnosis. Analysis of nucleic acids of foetal origin present in maternal vascular system].

Prenatal diagnosis is an important element of health care in pregnant women. Until now, prenatal testing of genetically determined diseases was invasive. Identification in maternal plasma of cell-free fetal nucleic acids (cffNA) has created new opportunities, and gave rise to genetic non-invasive prenatal diagnosis (NIPD). They are three leading trends in NIPD, depending on the clinical application: analysis of hereditary diseases, analysis of aneuploidy and study of maternal-fetal conflict. In case of hereditary diseases, application of NIPD is limited to autosomal dominant disorders where the mutation is carried on the paternal allelle. It refers to problems with distinguish fetal derived cell-free DNA from maternal cell-free DNA. The important issue for using NIPD techniques in practice is to develop appropriate law regulation. This is of particular importance in the non-medical applications, when the aim of testing could be e.g. selection of fetuses. The development of effective methods for the analysis of free fetal DNA present in the mother's bloodstream is a matter of few years and show the progress made in the fields of molecular biology and medicine. It seems that non-invasive testing for a wider range of genetic disorders is a only a question of time.

A Patient with Berardinelli-Seip Syndrome, Novel AGPAT2 Splicesite Mutation and Concomitant Development of Non-diabetic Polyneuropathy

Primary polyneuropathy in the context of Seip-Berardinelli type 1 seipinopathy, or congenital generalized lipodystrophy type 1 (CGL1) has not been previously reported. We report the case history of a 27 year old female CGL1 patient presenting with an unusual additional development of non-diabetic peripheral neuropathy and learning disabilities in early adolescence. Whole exome sequencing (WES) of the patient genome identified a novel variant, homozygous for a 52 bp intronic deletion in the AGPAT2 locus, coding for 1-acylglycerol-3-phosphate O-acyltransferase 2, which is uniquely associated with CGL1 seipinopathies, with no molecular evidence for dual diagnosis. Functional studies using RNA isolated from patient peripheral blood leucocytes showed abnormal RNA splicing resulting in the loss of 25 amino acids from the patient AGPAT2 protein coding sequence. Stability and transcription levels for the misspliced AGPAT2 mRNA in our patient nonetheless remained normal. Any AGPAT2 protein produced in our patient is therefore likely to be dysfunctional. However, formal linkage of this deletion to the neuropathy observed remains to be shown. The classical clinical presentation of a patient with AGPAT2-associated lipodystrophy shows normal cognition and no development of polyneuropathy. Cognitive disabilities and polyneuropathy are features associated exclusively with clinical CGL type 2 arising from seipin (BSCL2) gene mutations. This case study suggests that in some genetic contexts, AGPAT2 mutations can also produce phenotypes with primary polyneuropathy.

Rosiglitazone induces decreases in bone mass and strength that are reminiscent of aged bone.

Peroxisome proliferator-activated receptor-gamma (PPARgamma) regulates both glucose metabolism and bone mass. Recent evidence suggests that the therapeutic modulation of PPARgamma activity with antidiabetic thiazolidinediones elicits unwanted effects on bone. In this study, the effects of rosiglitazone on the skeleton of growing (1 month), adult (6 month), and aged (24 month) C57BL/6 mice were determined. Aging was identified as a confounding factor for rosiglitazone-induced bone loss that correlated with the increased expression of PPARgamma in bone marrow mesenchymal stem cells. The bone of young growing mice was least affected, although a significant decrease in bone formation rate was noted. In both adult and aged animals, bone volume was significantly decreased by rosiglitazone. In adult animals, bone loss correlated with attenuated bone formation, whereas in aged animals, bone loss was associated with increased osteoclastogenesis, mediated by increased receptor activator of nuclear factor-kappaB ligand (RANKL) expression. PPARgamma activation led to changes in marrow structure and function such as a decrease in osteoblast number, an increase in marrow fat cells, an increase in osteoclast number, and a loss of the multipotential character of marrow mesenchymal stem cells. In conclusion, rosiglitazone induces changes in bone reminiscent of aged bone and appears to induce bone loss by altering the phenotype of marrow mesenchymal stem cells.

Netoglitazone is a PPAR-gamma ligand with selective effects on bone and fat.

Thiazolidinediones are effective anti-diabetic drugs that improve insulin sensitivity through the activation of the nuclear receptor and adipocyte-specific transcription factor, peroxisome proliferator-activated receptor gamma (PPAR-gamma). Recent evidence suggests that PPAR-gamma also controls bone cell development and bone homeostasis. In mice, PPAR-gamma insufficiency results in increased bone mass, whereas administration of the specific PPAR-gamma agonist rosiglitazone leads to bone loss and increased bone marrow adiposity. Although the pro-adipocytic and anti-osteoblastic activities of PPAR-gamma can be separated in vitro using ligands with distinct chemical structures, little evidence exists supporting this functional separation in vivo. Netoglitazone (MCC-555, RWJ-241947) is a thiazolidinedione, which acts as either a full or partial PPAR-gamma agonist, or antagonist, in a cell type specific manner. In this study, the pro-adipocytic and anti-osteoblastic activities of netoglitazone were evaluated in vitro, using both U-33/gamma2 cells as a model of marrow mesenchymal cell differentiation under the control of PPAR-gamma2 and primary bone marrow cultures, and in vivo in C57BL/6 mice. In vitro, netoglitazone induced adipocyte and inhibited osteoblast formation in a PPAR-gamma2-dependent manner; however, it was 100-fold less effective than rosiglitazone. In vivo, the administration of netoglitazone at an effective hyperglycemic dose (10 microg/g body weight/day) did not result in trabecular bone loss. Bone quality parameters such as bone mineral density and bone microarchitecture were not affected in netoglitazone-treated animals. The observed lack of an in vivo effect of netoglitazone on bone was entirely consistent with its low anti-osteoblastic activity in vitro. In contrast to the observed in vitro effects, netoglitazone in vivo effectively induced marrow adipocyte formation and induced changes in the weights of extramedullary fat depots. Consistent with these cell type-specific effects, expression of the adipocyte-specific gene marker FABP4/aP2 was increased, whereas the expression of osteoblast-specific gene markers, Runx2, Dlx5, osteocalcin, and collagen were not affected by netoglitazone. In conclusion, netoglitazone is a member of a new class of PPAR-gamma ligands with distinct anti-diabetic, anti-osteoblastic, and pro-adipocytic activities in vivo.

Towards a Better Molecular Diagnosis of FMR1-Related Disorders-A Multiyear Experience from a Reference Lab.

The article summarizes over 20 years of experience of a reference lab in fragile X mental retardation 1 gene (FMR1) molecular analysis in the molecular diagnosis of fragile X spectrum disorders. This includes fragile X syndrome (FXS), fragile X-associated primary ovarian insufficiency (FXPOI) and fragile X-associated tremor/ataxia syndrome (FXTAS), which are three different clinical conditions with the same molecular background. They are all associated with an expansion of CGG repeats in the 5'UTR of FMR1 gene. Until 2016, the FMR1 gene was tested in 9185 individuals with the pre-screening PCR, supplemented with Southern blot analysis and/or Triplet Repeat Primed PCR based method. This approach allowed us to confirm the diagnosis of FXS, FXPOI FXTAS in 636/9131 (6.96%), 4/43 (9.3%) and 3/11 (27.3%) of the studied cases, respectively. Moreover, the FXS carrier status was established in 389 individuals. The technical aspect of the molecular analysis is very important in diagnosis of FXS-related disorders. The new methods were subsequently implemented in our laboratory. This allowed the significance of the Southern blot technique to be decreased until its complete withdrawal. Our experience points out the necessity of implementation of the GeneScan based methods to simplify the testing procedure as well as to obtain more information for the patient, especially if TP-PCR based methods are used.

Soluble TNF-α receptor I encoded on plasmid vector and its application in experimental gene therapy of radiation-induced lung fibrosis.

Post-radiation inflammatory reaction leads to an irreversible pulmonary fibrosis which may cause lethal respiratory insufficiency. Pathological inflammatory and fibrotic changes might be attenuated by inhibiting tumour necrosis factor (TNF)-α activity using TNF-α soluble receptors. Thus, an experimental antifibrotic gene therapy with the plasmid vector encoding a mouse soluble receptor I for TNF-α (psTNFR-I) was assessed. Soluble TNFR-I encoding gene was cloned into pcDNA3.1 plasmid. The ability of psTNFR-I expressing vector to transfect cells, and its biological activity in vitro and in vivo were examined by PCR, RT-PCR, MTT assay and ELISA. The C57Bl/6J mice received single intramuscular injection of psTNFR-I, conjugated with polyetylenimine (PEI) 25 kDa, equally divided to both hind legs, 3 days before irradiation (20 Gy, Co60), and either a single injection or ten injections once a week after irradiation. The data proved the effectiveness of psTNFR-I product to neutralise TNF-α activity in vitro. The in vivo plasmid incorporation and maintenance was confirmed. Measurements of plasma soluble TNFR-I levels showed that the in vivo gene transfer was effective. PEI was found to enhance transfection efficiency in vivo. The psTNFR-I/PEI complexes caused no toxicity in the transfected mice. C57Bl/6J mice that received prolonged psTNFR-I/PEI injections developed lethal fibrotic syndrome and died 8 weeks later than the mice treated with a double plasmid injection and the control mice treated with a control plasmid. Sequential administration of soluble TNFR-I by a nonviral, intramuscular gene transduction in the early and late post-radiation inflammatory phase prolonged survival of irradiated mice and attenuated the symptoms of lung fibrosis. The psTNFR-I gene transduction may provide a safe and simple method to partially neutralise TNF-α activity and prevent radiation-induced lung injury.