Effective Gene Therapy for Metachromatic Leukodystrophy Achieved with Minimal Lentiviral Genomic Integrations

Metachromatic leukodystrophy (MLD) is a fatal lysosomal storage disease (LSD) characterized by the deficient enzymatic activity of arylsulfatase A (ARSA). Combined autologous hematopoietic stem cell transplant (HSCT) with lentiviral (LV) based gene therapy has great potential to treat MLD. However, if enzyme production is inadequate, this could result in continued loss of motor function, implying a high vector copy number (VCN) requirement for optimal enzymatic output. This may place children at increased risk for genomic toxicity due to higher VCN. We increased the expression of ARSA cDNA at single integration by generating novel LVs, optimizing ARSA expression, and enhancing safety. In addition, our vectors achieved optimal transduction in mouse and human HSC with minimal multiplicity of infection (MOI). Our top-performing vector (EA1) showed at least 4X more ARSA activity than the currently EU-approved vector and a superior ability to secrete vesicle-associated ARSA, a critical modality to transfer functional enzymes from microglia to oligodendrocytes. Three-month-old Arsa -KO MLD mice transplanted with Arsa -KO BM cells transduced with 0.6 VCN of EA1 demonstrated behavior and CNS histology matching WT mice. Our novel vector boosts efficacy while improving safety as a robust approach for treating early symptomatic MLD patients.

Generation of three induced pluripotent stem cell lines from individuals with Aicardi-Goutières syndrome caused by a c.3019G>A (p.G1007R) autosomal dominant pathogenic variant in ADAR1

Mutations in Adenosine deaminase acting on RNA 1 (ADAR1) gene encoding RNA editing enzyme ADAR1 results in the neuroinflammatory leukodystrophy Aicardi Goutières Syndrome (AGS). AGS is an early onset leukoencephalopathy with an exacerbated interferon response leading to neurological regression with intellectual disability, spasticity, and motor deficits. We have generated three induced pluripotent stem cell (iPSC) lines from peripheral blood mononuclear cells (PBMCs) of individuals with ADAR1G1007R mutation. The generated iPSCs were investigated to confirm a normal karyotype, pluripotency, and trilineage differentiation potential. The reprogrammed iPSCs will allow us to model AGS, dissect the cellular mechanisms and testing different treatment targets.

Further Delineation of the Clinical and Pathologic Features of HIKESHI-Related Hypomyelinating Leukodystrophy

BACKGROUND

A recurrent homozygous missense variant, c.160G>C;p.(Val54Leu) in HIKESHI, was found to cause a hypomyelinating leukodystrophy with high frequency in the Ashkenazi Jewish population. We provide extended phenotypic classification of this disorder based on clinical history of a further seven affected individuals, assess carrier frequency in the Ashkenazi Jewish population, and provide a neuropathological study.

METHODS

Clinical information, neuroimaging, and biosamples were collected. Brain autopsy was performed for one case.

RESULTS

Individuals with HIKESHI-related disease share common clinical features: early axial hypotonia evolving to dystonia or with progressive spasticity, hyperreflexia and clonus, feeding difficulties with poor growth, and nystagmus. Severe morbidity or death during febrile illness occurred in five of the nine affected individuals. Magnetic resonance images of seven patients were analyzed and demonstrated diffuse hypomyelination and thin corpus callosum. Genotyping data of more than 125,000 Ashkenazi Jewish individuals revealed a carrier frequency of 1 in 216. Gross pathology examination in one case revealed abnormal white matter. Microscopically, there was a near-total absence of myelin with a relative preservation of axons. The cerebral white matter showed several reactive astrocytes and microglia.

CONCLUSIONS

We provide pathologic evidence for a primary disorder of the myelin in HIKESHI-related leukodystrophy. These findings are consistent with the hypomyelination seen in brain magnetic resonance imaging and with the clinical features of early-onset spastic/dystonic quadriplegia and nystagmus. The high carrier rate of the recurrent variant seen in the Ashkenazi Jewish population requires increased attention to screening and diagnosis of this condition, particularly in this population.

Glial cells in the driver seat of leukodystrophy pathogenesis

Glia cells are often viewed as support cells in the central nervous system, but recent discoveries highlight their importance in physiological functions and in neurological diseases. Central to this are leukodystrophies, a group of progressive, neurogenetic disease affecting white matter pathology. In this review, we take a closer look at multiple leukodystrophies, classified based on the primary glial cell type that is affected. While white matter diseases involve oligodendrocyte and myelin loss, we discuss how astrocytes and microglia are affected and impinge on oligodendrocyte, myelin and axonal pathology. We provide an overview of the leukodystrophies covering their hallmark features, clinical phenotypes, diverse molecular pathways, and potential therapeutics for clinical trials. Glial cells are gaining momentum as cellular therapeutic targets for treatment of demyelinating diseases such as leukodystrophies, currently with no treatment options. Here, we bring the much needed attention to role of glia in leukodystrophies, an integral step towards furthering disease comprehension, understanding mechanisms and developing future therapeutics.

Type II Alexander disease caused by splicing errors and aberrant overexpression of an uncharacterized GFAP isoform

Alexander disease results from gain-of-function mutations in the gene encoding glial fibrillary acidic protein (GFAP). At least eight GFAP isoforms have been described, however, the predominant alpha isoform accounts for ∼90% of GFAP protein. We describe exonic variants identified in three unrelated families with Type II Alexander disease that alter the splicing of GFAP pre-messenger RNA (mRNA) and result in the upregulation of a previously uncharacterized GFAP lambda isoform (NM_001363846.1). Affected members of Family 1 and Family 2 shared the same missense variant, NM_001363846.1:c.1289G>A;p.(Arg430His) while in Family 3 we identified a synonymous variant in the adjacent nucleotide, NM_001363846.1:c.1290C>A;p.(Arg430Arg). Using RNA and protein analysis of brain autopsy samples, and a mini-gene splicing reporter assay, we demonstrate both variants result in the upregulation of the lambda isoform. Our approach demonstrates the importance of characterizing the effect of GFAP variants on mRNA splicing to inform future pathophysiologic and therapeutic study for Alexander disease.

TUBB4A mutations result in both glial and neuronal degeneration in an H-ABC leukodystrophy mouse model

Mutations in TUBB4A result in a spectrum of leukodystrophy including Hypomyelination with Atrophy of Basal Ganglia and Cerebellum (H-ABC), a rare hypomyelinating leukodystrophy, often associated with a recurring variant p.Asp249Asn (D249N). We have developed a novel knock-in mouse model harboring heterozygous (Tubb4a^D249N/+) and the homozygous (Tubb4a^D249N/D249N) mutation that recapitulate the progressive motor dysfunction with tremor, dystonia and ataxia seen in H-ABC. Tubb4a^D249N/D249N mice have myelination deficits along with dramatic decrease in mature oligodendrocytes and their progenitor cells. Additionally, a significant loss occurs in the cerebellar granular neurons and striatal neurons in Tubb4a^D249N/D249N mice. In vitro studies show decreased survival and dysfunction in microtubule dynamics in neurons from Tubb4a^D249N/D249N mice. Thus Tubb4a^D249N/D249N mice demonstrate the complex cellular physiology of H-ABC, likely due to independent effects on oligodendrocytes, striatal neurons, and cerebellar granule cells in the context of altered microtubule dynamics, with profound neurodevelopmental deficits.

Astrocytes, an active player in Aicardi-Goutières syndrome

Aicardi-Goutières syndrome (AGS) is an early-onset, autoimmune and genetically heterogeneous disorder with severe neurologic injury. Molecular studies have established that autosomal recessive mutations in one of the following genes are causative: TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR1 and IFIH1/MDA5. The phenotypic presentation and pathophysiology of AGS is associated with over-production of the cytokine Interferon-alpha (IFN-α) and its downstream signaling, characterized as type I interferonopathy. Astrocytes are one of the major source of IFN in the central nervous system (CNS) and it is proposed that they could be key players in AGS pathology. Astrocytes are the most ubiquitous glial cell in the CNS and perform a number of crucial and complex functions ranging from formation of blood-brain barrier, maintaining ionic homeostasis, metabolic support to synapse formation and elimination in healthy CNS. Involvement of astrocytic dysfunction in neurological diseases-Alexander's disease, Epilepsy, Alzheimer's and amyotrophic lateral sclerosis (ALS)-has been well-established. It is now known that compromised astrocytic function can contribute to CNS abnormalities and severe neurodegeneration, nevertheless, its contribution in AGS is unclear. The current review discusses known molecular and cellular pathways for AGS mutations and how it stimulates IFN-α signaling. We shed light on how astrocytes might be key players in the phenotypic presentations of AGS and emphasize the cell-autonomous and non-cell-autonomous role of astrocytes. Understanding the contribution of astrocytes will help reveal mechanisms underlying interferonopathy and develop targeted astrocyte specific therapeutic treatments in AGS.

Spatial and Working Memory Is Linked to Spine Density and Mushroom Spines

Background

Changes in synaptic structure and efficacy including dendritic spine number and morphology have been shown to underlie neuronal activity and size. Moreover, the shapes of individual dendritic spines were proposed to correlate with their capacity for structural change. Spine numbers and morphology were reported to parallel memory formation in the rat using a water maze but, so far, there is no information on spine counts or shape in the radial arm maze (RAM), a frequently used paradigm for the evaluation of complex memory formation in the rodent.

Methods

24 male Sprague-Dawley rats were divided into three groups, 8 were trained, 8 remained untrained in the RAM and 8 rats served as cage controls. Dendritic spine numbers and individual spine forms were counted in CA1, CA3 areas and dentate gyrus of hippocampus using a DIL dye method with subsequent quantification by the Neuronstudio software and the image J program.

Results

Working memory errors (WME) and latency in the RAM were decreased along the training period indicating that animals performed the task. Total spine density was significantly increased following training in the RAM as compared to untrained rats and cage controls. The number of mushroom spines was significantly increased in the trained as compared to untrained and cage controls. Negative significant correlations between spine density and WME were observed in CA1 basal dendrites and in CA3 apical and basal dendrites. In addition, there was a significant negative correlation between spine density and latency in CA3 basal dendrites.

Conclusion

The study shows that spine numbers are significantly increased in the trained group, an observation that may suggest the use of this method representing a morphological parameter for memory formation studies in the RAM. Herein, correlations between WME and latency in the RAM and spine density revealed a link between spine numbers and performance in the RAM.

The effect of modafinil on the rat dopamine transporter and dopamine receptors D1-D3 paralleling cognitive enhancement in the radial arm maze

A series of drugs have been reported to increase memory performance modulating the dopaminergic system and herein modafinil was tested for its working memory (WM) enhancing properties. Reuptake inhibition of dopamine, serotonin (SERT) and norepinephrine (NET) by modafinil was tested. Sixty male Sprague–Dawley rats were divided into six groups (modafinil-treated 1–5–10 mg/kg body weight, trained and untrained and vehicle treated trained and untrained rats; daily injected intraperitoneally for a period of 10 days) and tested in a radial arm maze (RAM), a paradigm for testing spatial WM. Hippocampi were taken 6 h following the last day of training and complexes containing the unphosphorylated or phosphorylated dopamine transporter (DAT-CC and pDAT-CC) and complexes containing the D1–3 dopamine receptor subunits (D1–D3-CC) were determined. Modafinil was binding to the DAT but insignificantly to SERT or NET and dopamine reuptake was blocked specifically (IC₅₀ = 11.11 μM; SERT 1547 μM; NET 182 μM). From day 8 (day 9 for 1 mg/kg body weight) modafinil was decreasing WM errors (WMEs) in the RAM significantly and remarkably at all doses tested as compared to the vehicle controls. WMEs were linked to the D2R-CC and the pDAT-CC. pDAT and D1–D3-CC levels were modulated significantly and modafinil was shown to enhance spatial WM in the rat in a well-documented paradigm at all the three doses and dopamine reuptake inhibition with subsequent modulation of D1–3-CC is proposed as a possible mechanism of action.

Different expression of membrane-bound and cytosolic hippocampal steroid receptor complexes during spatial training in young male rats

Brain steroid receptors are involved in mediating stress responses and cognitive processes throughfast non-genomic signaling of membrane-bound receptors or through the slower genomic actions of cytosolic receptors. Although the contribution of these different pathways in the formation and maintenance of memories has been widely discussed, little is known about the regulation of membrane versus cytosolic receptors during a learning task. Besides the relatively well studied corticosterone-binding glucocorticoid (GR) and mineralocorticoid (MR) receptors, sex steroid hormone receptors, such as the androgen and estrogen (ERα and ERβ) receptors, have also been shown to be involved in the regulation of stress and cognition. Moreover, the latter receptors are known to be functional in both sexes. Therefore, we studied the expression of hippocampal receptors in both cellular fractions during spatial learning in male rats. Membrane and cytosolic GR were shown to be downregulated after memory acquisition and unaffected after consolidation, whereas membrane MR was upregulated after both learning phases and unaffected in the cytosol. Cytosolic ERα was downregulated after both phases and unaffected in the membrane. The remaining receptors were not regulated. The data suggest a specific role of MR and ERα during training as fast and slow mediators, respectively.

Low-concentration lidocaine rapidly inhibits axonal transport in cultured mouse dorsal root ganglion neurons

BACKGROUND

Axonal transport plays a critical role in supplying materials for a variety of neuronal functions such as morphogenetic plasticity, synaptic transmission, and cell survival. In the current study, the authors investigated the effects of the analgesic agent lidocaine on axonal transport in neurites of cultured mouse dorsal root ganglion neurons. In relation to their effects, the effects of lidocaine on the growth rate of the neurite were also examined.

METHODS

Isolated mouse dorsal root ganglion cells were cultured for 48 h until full growth of neurites. Video-enhanced microscopy was used to observe particles transported within neurites and to measure the neurite growth during control conditions and in the presence of lidocaine.

RESULTS

Application of 30 microM lidocaine immediately reduced the number of particles transported in anterograde and retrograde axonal directions. These effects were persistently observed during the application (26 min) and were reversed by lidocaine washout. The inhibitory effect was dose-dependent at concentrations from 0.1 to 1,000 microM (IC50 = 10 microM). In Ca2+-free extracellular medium, lidocaine failed to inhibit axonal transport. Calcium ionophore A23187 (0.1 microM) reduced axonal transport in both directions. The inhibitory effects of lidocaine and A23187 were abrogated by 10 microM KN-62, a Ca2+-calmodulin-dependent protein kinase II inhibitor. Application of such low-concentration lidocaine (30 microM) for 30 min reduced the growth rate of neurites, and this effect was also blocked by KN-62.

CONCLUSIONS

Low-concentration lidocaine rapidly inhibits axonal transport and neurite growth via activation of calmodulin-dependent protein kinase II.

Effect of the end-tidal xenon correction method on cerebral blood flow determination

The objective of this work is to show how the end-tidal xenon correction method contributes to determining the cerebral blood flow (CBF) values. Respiratory xenon data from 443 patients (mean age, 59.1 +/- 13.5) were analyzed using two methods: the conventional fitting method and the end-tidal correction method. For both methods, xenon saturation rate constant (Ka1) and desaturation rate constant (Ka2) were calculated for washin and washout phases respectively. By applying the correction method, both the histograms for Ka1 and Ka2 change significantly; they become to have narrower distribution with smaller mean value. As the average effect based on computer simulation, if calculated CBF values using corrected Ka1 and Ka2 are 80 cc/100 g-tissue/min for the gray matter and 20 for the white matter, those using conventional Ka1 and Ka2 become 62.8 for the gray matter and 17.9 for the white matter. By applying the end-tidal correction method, obtained CBF values increase, and the extent of increase is larger when xenon inhalation speed is slower.

The effect of xenon inhalation speed on cerebral blood flow obtained using the end-tidal method in xenon-enhanced CT

PURPOSE

The purpose of this work is to show how variations in inhalation speed of xenon gas affect cerebral blood flow (CBF) values obtained using the end-tidal method on xenon-enhanced CT (Xe-CT). We tried to clarify whether arterial xenon concentration could keep up with end-tidal xenon concentration by evaluating the effect of xenon inhalation speed on calculated CBF values.

METHOD

The same subject underwent two or three consecutive Xe-CT examinations, varying xenon inhalation speed. The rate constants of applied inhalation speeds were 0.1-0.15 min-1 (low speed), 0.25-0.3 min-1 (middle speed), and 1-2 min-1 (high speed), respectively.

RESULTS

No significant difference was observed among the CBF values of the same subject obtained under different inhalation speeds.

CONCLUSION

End-tidal xenon can closely reflect arterial xenon under the customary method of xenon supply. The end-tidal method can provide reliable absolute CBF values, assuming actual CBF values are substantially unchanged regardless of the inhalation speed variation applied in this work.

Correction method for end-tidal xenon concentration in CBF measurements with xenon-enhanced CT

PURPOSE

The goal of this work is to show how variations in respiratory rate and tidal volume affect calculated cerebral blood flow (CBF) values on xenon-enhanced CT. In xenon-enhanced CT examination, the patient often takes shallow and rapid breaths. Thus, it is less likely that end-tidal xenon concentration reflects arterial xenon concentration, and appropriate correction measures should be taken for the end-distal respiratory data to obtain reliable CBF values.

METHOD

Preliminary breathing tests were performed using a lung phantom to determine the influence of respiratory volume and rate on end-tidal xenon concentration. Two xenon-enhanced CT studies were conducted of a healthy person with completely different respiratory manners between two studies. One was deep and slow respiration. The other was shallow and rapid respiration.

RESULTS

The lung phantom results prove that deep and slow respiration is essential for the end-tidal method. The results of xenon-enhanced CT studies of the same person show that the direct use of end-tidal data for shallow and rapid respiration leads to CBF values much lower than the actual values.

CONCLUSION

Differences in respiratory rate and tidal volume during xenon inhalation can significantly affect calculated CBF values on xenon-enhanced CT. With use of the correction methods described herein, these effects can be minimized. We have derived the end-tidal correction method on the assumption that a person's CBF values should be kept unchanged regardless of different respiratory manners.

Characterization and identification of the glucose transporter of human erythrocytes

The glucose transporter was purified from human erythrocytes (Kasahara, M. and Hinkle, P.C. (1977) J. Biol. Chem. 252, 7384-7390). The following results support the conclusion that a major protein in the purified transporter fraction, zone 4.5 is the glucose transporter (or a part of the transporter) and is different from band 3: (1) peptide maps of zone 4.5 were similar throughout the broad band in sodium dodecyl sulfate-gel electrophoresis and were different from those of band 3, (2) specific binding of cytochalasin B was found to the transporter fraction, but not to a band 3 fraction, (3) the N-terminal amino acid analysis of the transporter fraction showed a single N-terminal of lysine, whereas the band 3 fraction showed no clear N-terminal, and (4) the rabbit antibody raised against the transporter fraction formed a precipitation line with the transporter fraction, but not with the band 3 fraction. A filtration apparatus was devised for quick and accurate measurement of cytochalasin B binding, with which results comparable to those from equilibrium dialysis were obtained.

Random distribution of the glucose transporter of human erythrocytes in reconstituted liposomes

The glucose transporter of human erythrocytes was reconstituted with soybean phospholipids by the freeze-thaw/sonication method and the distribution of the transporter molecules in liposomes was studied. The steady state level of glucose transport in reconstituted liposomes showed saturation when increased amounts of the transporter were used for reconstitution. The saturation curve fitted well to a theoretical curve which was derived assuming a Poisson distribution of the transporter. Freeze-fracture electron micrographs showed random distribution of intramembraneous particles on liposomes, irrespective of liposome size or amount of the transporter added. A detailed study showed a parameter of the distribution (the ratio of transporter to liposome) obtained from the transport measurement can be used for the analysis of the distribution of intramembraneous particles, indicating that most of the molecules seen as particles were active in transport.