atrophy plus syndrome, or costeff optic atrophy syndrome): identification of the OPA3 gene and its

deficiencies in a male with cardiomyopathy and 3-methylglutaconic aciduria, ” J Inherit Metab Dis

Burosumab therapy in children with x-linked hypophosphatemia

BACKGROUND X-linked hypophosphatemia is characterized by increased secretion of fibroblast growth factor 23 (FGF-23), which leads to hypophosphatemia and consequently rickets, osteomalacia, and skeletal deformities. We investigated burosumab, a monoclonal antibody that targets FGF-23, in patients with X-linked hypophosphatemia. METHODS In an open-label, phase 2 trial, we randomly assigned 52 children with X-linked hypophosphatemia, in a 1:1 ratio, to receive subcutaneous burosumab either every 2 weeks or every 4 weeks; the dose was adjusted to achieve a serum phosphorus level at the low end of the normal range. The primary end point was the change from baseline to weeks 40 and 64 in the Thacher rickets severity total score (ranging from 0 to 10, with higher scores indicating greater disease severity). In addition, the Radiographic Global Impression of Change was used to evaluate rachitic changes from baseline to week 40 and to week 64. Additional end points were changes in pharmacodynamic markers, linear growth, physical ability, and patient-reported outcomes and the incidence of adverse events. RESULTS The mean Thacher rickets severity total score decreased from 1.9 at baseline to 0.8 at week 40 with every-2-week dosing and from 1.7 at baseline to 1.1 at week 40 with every-4-week dosing (P<0.001 for both comparisons); these improvements persisted at week 64. The mean serum phosphorus level increased after the first dose in both groups, and more than half the patients in both groups had levels within the normal range (3.2 to 6.1 mg per deciliter [1.0 to 2.0 mmol per liter]) by week 6. Stable serum phosphorus levels were maintained through week 64 with every-2-week dosing. Renal tubular phosphate reabsorption increased from baseline in both groups, with an overall mean increase of 0.98 mg per deciliter (0.32 mmol per liter). The mean dose of burosumab at week 40 was 0.98 mg per kilogram of body weight with every-2-week dosing and 1.50 mg per kilogram with every-4-week dosing. Across both groups, the mean serum alkaline phosphatase level decreased from 459 U per liter at baseline to 369 U per liter at week 64. The mean standing-height z score increased in both groups, with greater improvement seen at all time points with every-2-week dosing (an increase from baseline of 0.19 at week 64) than with every-4-week dosing (an increase from baseline of 0.12 at week 64). Physical ability improved and pain decreased. Nearly all the adverse events were mild or moderate in severity. CONCLUSIONS In children with X-linked hypophosphatemia, treatment with burosumab improved renal tubular phosphate reabsorption, serum phosphorus levels, linear growth, and physical function and reduced pain and the severity of rickets

Development of a reporter gene assay to identify control elements required for dosage compensation in Drosophila Melanogaster : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Genetics at Massey University

Dosage compensation (equalisation of X-linked gene products) occurs in Drosophila melanogaster by a two-fold transcriptional increase of X-linked gene expression in the male. This involves the binding of four proteins, MSL-1, MSL-2, MSL-3 and MLE (collectively known as the MSLs), to hundreds of sites along the length of the male X. The MSLs are thought to recruit MOF, a histone acetyl transferase, which facilitates the increase in transcriptional activity of X-linked genes. The DNA sequences required to target the MSL complex to the X chromosome (known as dosage compensation regulatory elements, or DCREs) remain elusive, despite numerous attempts over the last ten years to identify them. DCREs are thought to be present at multiple sites along the length of the X chromosome, as antibodies to the MSLs bind to hundreds of sites along the X, and autosomal genes transduced to the X usually become dosage compensated. The first objective of this study was to develop a reporter gene assay to screen for DCREs that would minimise problems previously encountered. A construct consisting of the constitutive armadillo promoter fused to the lacZ reporter gene (called arm-lacZ) was flanked by insulator elements which block the repressive effects of the autosomal chromatin environment. Fragments of X-linked DNA were inserted upstream of the armadillo promoter with the premise that males carrying one copy of an autosomal insertion of this construct would express twice the level of ß-galactosidase as females. Transgenic flies carrying autosomal insertions of X-linked fragments plus arm-lacZ were generated and one dose males and females were assayed for ß-galactosidase activity using a spectrophotometric assay. In all cases, males and females expressed the same level of lacZ. This suggests that no DCREs that could confer dosage compensation onto arm-lacZ were present in the X-linked fragments. arm-lacZ is capable of being dosage compensated as males and females carrying one copy of an X-linked insertion of arm-lacZ produce a 2:1 male to female ratio. This implies that DCREs of the 'strength' required to dosage compensate arm-lacZ are rarer than previously thought. A second method of dosage compensation that is independent of the MSLs is thought to occur in Drosophila. The X-linked gene runt is dosage compensated in the absence of the MSLs. It is possible that runt is sex specifically regulated by the female specific Sex lethal protein (Sxl). Sxl down-regulates msl-2 in females by binding to (U)8 or A(U)7 sequences in the msl-2 5' and 3' untranslated regions (UTRs) of the mRNA. runt mRNA contains three Sxl binding sites in its 3' UTR, as do 20 other X-linked genes. The second objective of this project was to determine if Sxl could down regulate a gene in females, purely by the addition of three Sxl binding sites to the 3'UTR. Sxl binding sites were inserted into the 3'UTR of arm-lacZ in the form of a 40 bp synthetic linker containing three of the sites, and also as a 170 bp fragment from the runt 3' UTR. ß-galactosidase assays of flies carrying the Sxl binding sites from runt showed that males expressed an average of 1.31 to 1.46 times the level of lacZ than females. This shows that Sxl can down-regulate a gene if there are Sxl binding sites in its 3' UTR, however, to achieve two-fold regulation, additional factors may be required, or topologically, the sites may not have been in the right position in the 3' UTR for optimal activity of Sxl. Flies carrying the synthetic linker expressed the same level of ß-galactosidase in both sexes which suggests that either additional elements within the 3' UTR are required, or that the spacing between the sites is critical for the action of Sxl

PAK in Alzheimer disease, Huntington disease and X-linked mental retardation.

Developmental cognitive deficits including X-linked mental retardation (XLMR) can be caused by mutations in P21-activated kinase 3 (PAK3) that disrupt actin dynamics in dendritic spines. Neurodegenerative diseases such as Alzheimer disease (AD), where both PAK1 and PAK3 are dysregulated, may share final common pathways with XLMR. Independent of familial mutation, cognitive deficits emerging with aging, notably AD, begin after decades of normal function. This prolonged prodromal period involves the buildup of amyloid-β (Aβ) extracellular plaques and intraneuronal neurofibrillary tangles (NFT). Subsequently region dependent deficits in synapses, dendritic spines and cognition coincide with dysregulation in PAK1 and PAK. Specifically proximal to decline, cytoplasmic levels of actin-regulating Rho GTPase and PAK1 kinase are decreased in moderate to severe AD, while aberrant activation and translocation of PAK1 appears around the onset of cognitive deficits. Downstream to PAK1, LIM kinase inactivates cofilin, contributing to cofilin pathology, while the activation of Rho-dependent kinase ROCK increases Aβ production. Aβ activation of fyn disrupts neuronal PAK1 and ROCK-mediated signaling, resulting in synaptic deficits. Reductions in PAK1 by the anti-amyloid compound curcumin suppress synaptotoxicity. Similarly other neurological disorders, including Huntington disease (HD) show dysregulation of PAKs. PAK1 modulates mutant huntingtin toxicity by enhancing huntingtin aggregation, and inhibition of PAK activity protects HD as well as fragile X syndrome (FXS) symptoms. Since PAK plays critical roles in learning and memory and is disrupted in many cognitive disorders, targeting PAK signaling in AD, HD and XLMR may be a novel common therapeutic target for AD, HD and XLMR

MAP7D2 is a brain expressing X-linked maternal imprinted gene in humans

Increasing evidence suggests imprinted genes influence mouse and human behaviors and cognitive functions. Unlike autosomal imprinted genes, X-linked imprinted genes are expressed in a sex-dependent manner because of male hemizygosity. Therefore, these genes could directly affect sex-specific brain functions and sex-biased vulnerability to psychiatric disorders such as autism1. Comparing lymphoblastoid cell lines (LCL) and peripheral blood mononuclear cells (PBMC) from healthy adult male and females, we identified MAP7 domain containing 2 (MAP7D2) as the first human X-linked imprinted gene. Both in LCL and PBMC, MAP7D2 expression was significantly suppressed in males by maternal imprinting. In each female LCL clone, MAP7D2 was expressed higher in paternally derived allele and was affected by X-chromosome inactivation. In female PBMC, however, reactivation of maternal MAP7D2 alleles was observed. MAP7D2 was expressed specifically in the brain among human tissues with unique isoforms. These results predict a crucial role of MAP7D2 for human sex-dependent neurobiological traits

Increased Metabolic Rate in X-linked Hypophosphatemic Mice

Hyp mice are a model for human X-linked hypophosphatemia, the most common form of vitamin D-resistant rickets. It has previously been observed that Hyp mice have a greater food consumption per gram body weight than do normal mice. This led to the search for some alteration in metabolism in Hyp mice. We found that oxygen consumption was significantly higher in Hyp mice than in normal C57BL/6J mice and this was accompanied by an increased percentage of cardiac output being delivered to organs of heat production (liver and skeletal muscle), to the skin, and to bone and a decreased percentage to the gastrointestinal tract of Hyp mice. The increased oxygen consumption in Hyp mice was not associated with increased plasma free T4 levels and was not affected by alterations in plasma phosphate produced by a low phosphate diet. The cause of the increased oxygen consumption is not known, and the role that this change and reported changes in distribution of cardiac output may play in the development of X-linked hypophosphatemia is also unknown. Study of the cardiovascular and thermoregulatory systems in Hyp mice should help increase understanding of the underlying mechanisms of this disease

Long-term rearrangement of retinal structures in a novel mutation of X-linked retinoschisis

The aim of the present study was to report a novel mutation in the retinoschisin 1 (RS1) gene in a Caucasian family affected by X-linked juvenile retinoschisis (XLRS) and to describe the long-term modification of retinal structure. Two brothers with an early onset maculopathy were diagnosed with XLRS. Fundus photography, fluorescein angiography, spectral domain optical coherence tomography and electroretinogram analyses were performed. Their sister was also examined. All subjects were screened for mutations in the RS1 gene. XLRS patients demonstrated a marked reduction of best-corrected visual acuity. SD-OCT scans reported a cystic degeneration primarily involving the inner nuclear layer, though some cysts were detected in the outer plexiform layer and in the ganglion cell layer. During the ten-year follow-up, a progressive retinal thickening and coalescence of the cysts was observed. Genetic testing revealed a novel mutation (p.Ile212Asn) in the RS1 gene in both XLRS patients, whereas their sister was not a genetic carrier. Several mutations of the RS1 gene were recognized to be responsible for XLRS. Although the correspondence between genotype and phenotype is still under debate, is reasonable that siblings affected by XLRS could share other genetic and/or epigenetic factors capable to influence clinical course of the disease

Severe B Cell Deficiency in Mice Lacking the Tec Kinase Family Members Tec and Btk

The cytoplasmic protein tyrosine kinase Tec has been proposed to have important functions in hematopoiesis and lymphocyte signal transduction. Here we show that Tec-deficient mice developed normally and had no major phenotypic alterations of the immune system. To reveal potential compensatory roles of other Tec kinases such as Bruton's tyrosine kinase (Btk), Tec/Btk double-deficient mice were generated. These mice exhibited a block at the B220+CD43+ stage of B cell development and displayed a severe reduction of peripheral B cell numbers, particularly immunoglobulin (Ig)MloIgDhi B cells. Although Tec/Btknull mice were able to form germinal centers, the response to T cell–dependent antigens was impaired. Thus, Tec and Btk together have an important role both during B cell development and in the generation and/or function of the peripheral B cell pool. The ability of Tec to compensate for Btk may also explain phenotypic differences in X-linked immunodeficiency (xid) mice compared with human X-linked agammaglobulinemia (XLA) patients

Pharmacological rescue of adult hippocampal neurogenesis in a mouse model of X-linked intellectual disability

Oligophrenin-1 (OPHN1) is a Rho GTPase activating protein whose mutations cause X-linked intellectual disability (XLID). How loss of function of Ophnl affects neuronal development is only partly understood. Here we have exploited adult hippocampal neurogenesis to dissect the steps of neuronal differentiation that are affected by Ophn1 deletion. We found that mice lacking Ophnl display a reduction in the number of newborn neurons in the dentate gyrus. A significant fraction of the Ophn1-deficient newly generated neurons failed to extend an axon towards CM, and showed an altered density of dendritic protrusions. Since Ophnl-deficient mice display overactivation of Rho-associated protein kinase (ROCK) and protein kinase A (PICA) signaling, we administered a clinically approved ROCK/PICA inhibitor (fasudil) to correct the neurogenesis defects. While administration of fasudil was not effective in rescuing axon formation, the same treatment completely restored spine density to control levels, and enhanced the long-term survival of adult-born neurons in mice lacking Ophn1. These results identify specific neurodevelopmental steps that are impacted by Ophn1 deletion, and indicate that they may be at least partially corrected by pharmacological treatment. (C) 2017 The Authors. Published by Elsevier Inc

Deletion within the Src homology domain 3 of Bruton's tyrosine kinase resulting in X-linked agammaglobulinemia (XLA).

The gene responsible for X-linked agammaglobulinemia (XLA) has been recently identified to code for a cytoplasmic tyrosine kinase (Bruton's agammaglobulinemia tyrosine kinase, BTK), required for normal B cell development. BTK, like many other cytoplasmic tyrosine kinases, contains Src homology domains (SH2 and SH3), and catalytic kinase domain. SH3 domains are important for the targeting of signaling molecules to specific subcellular locations. We have identified a family with XLA whose affected members have a point mutation (g--&gt;a) at the 5' splice site of intron 8, resulting in the skipping of coding exon 8 and loss of 21 amino acids forming the COOH-terminal portion of the BTK SH3 domain. The study of three generations within this kinship, using restriction fragment length polymorphism and DNA analysis, allowed identification of the mutant X chromosome responsible for XLA and the carrier status in this family. BTK mRNA was present in normal amounts in Epstein-Barr virus-induced B lymphoblastoid cell lines established from affected family members. Although the SH3 deletion did not alter BTK protein stability and kinase activity of the truncated BTK protein was normal, the affected patients nevertheless have a severe B cell defect characteristic for XLA. The mutant protein was modeled using the normal BTK SH3 domain. The deletion results in loss of two COOH-terminal beta strands containing several residues critical for the formation of the putative SH3 ligand-binding pocket. We predict that, as a result, one or more crucial SH3 binding proteins fail to interact with BTK, interrupting the cytoplasmic signal transduction process required for B cell differentiation