BGP-15 prevents the death of neurons in a mouse model of familial dysautonomia

Genetic modeling of ELP1-associated Sonic hedgehog medulloblastoma identifies MDM2 as a selective therapeutic target

Germline loss-of-function (LOF) variants in Elongator acetyltransferase complex subunit 1 (ELP1) are the most prevalent predisposing genetic events in childhood medulloblastoma (MB), accounting for ∼30% of the Sonic hedgehog (SHH) 3 subtype. The mechanism(s) by which germline ELP1 deficiency provokes SHH-MB pathogenesis remain unknown. Genetically engineered mice mimicking heterozygous Elp1 LOF (Elp1HET) seen in affected germline carriers exhibit hallmark features of premalignancy in cerebellar granule neuron progenitors (GNPs), including increased DNA replication stress, genomic instability, accelerated cell cycle, and stalled differentiation. Orthotopic transplantation of Elp1HET GNPs harboring somatic Ptch1 inactivation yields SHH-MB-like tumors with compromised p53 signaling, providing a plausible explanation for the exclusivity of ELP1-associated MBs in the SHH-3 subtype. Preclinical treatment of ELP1-mutant patient-derived xenografts with an FDA-approved MDM2 inhibitor reactivates p53-dependent apoptosis and extends survival. Our findings functionally substantiate the role of ELP1 deficiency in SHH-MB predisposition and nominate therapeutics targeting MDM2 as a rational treatment option.

The role of granulosa cells in oocyte development and aging: Mechanisms and therapeutic opportunities

Granulosa cells (GCs) are essential for oocyte maturation, providing metabolic support, hormonal signaling, and structural integrity critical to successful follicular development. However, advancing age disrupts these functions, driven by factors such as increased oxidative stress, mitochondrial dysfunction, and transcriptomic and proteomic alterations. These age-related changes in GCs contribute to compromised oocyte quality, diminished follicular support, and a decline in fertility, particularly in women of advanced maternal age. This review highlights recent progress in understanding the pivotal roles of GCs in maintaining oocyte health, with a focus on the mechanisms underlying their aging-related dysfunction. Furthermore, we explore promising therapeutic strategies, including antioxidant therapies, metabolic modulators, and GC-based rejuvenation techniques, aimed at mitigating the impacts of reproductive aging. By consolidating and analyzing existing research, this review provides valuable perspectives on fertility preservation and factors shaping reproductive outcomes in women of advanced maternal age.

Sperm oxidative damage acquired during seminal plasma removal for assisted reproductive technology is reduced by BGP-15

PURPOSE

Semen manipulation for assisted reproductive technology (ART) causes spermatozoa damage; thus, we investigated the potential of the novel therapeutic BGP-15 to preserve sperm quality during semen washing prior to insemination.

METHODS

Donated human ejaculates (N = 40), with or without 10 µM BGP-15, were analyzed for sperm motility, DNA fragmentation, and oxidation. Seminal plasma was removed using different clinical sperm selection methods: simple wash, swim-up, or density gradient centrifugation (DGC), followed by assessment for sperm motility, mitochondrial ROS (mtROS), mitochondrial membrane potential (MMP), and DNA fragmentation and oxidation.

RESULTS

Donated semen samples incubated with BGP-15 had increased sperm motility (+ 15%, p = 0.002) and reduced oxidative DNA damage levels (- 57%, p = 0.03). Samples processed by simple wash had the highest sperm count compared with DGC (+ 55%, p < 0.005) and swim-up (+ 21%, p < 0.0005). Swim-up showed increased vitality compared with DGC (+ 18%, p < 0.001) and simple wash (+ 27%, p < 0.0001), as well as the lowest DNA oxidation levels compared with simple wash - 40%, (p = 0.01) and DGC (- 76%, p < 0.0001). Swim-up also had the lowest mitochondrial membrane potential compared with simple wash and DGC (- 28%, p < 0.03). Comparison between untreated and BGP-15-treated groups for each sperm washing method showed that BGP-15 increased MMP in DGC sperm (+ 11%, p = 0.0006), and reduced DNA fragmentation in washed samples (- 22%, p = 0.03). Moreover, BGP-15 lowered DNA oxidation in all preparation methods: washed (- 48%, p = 0.002), swim-up (- 42%, p = 0.04), and DGC (- 29%, p < 0.0001).

CONCLUSIONS

The inclusion of BGP-15 during semen preparation can protect sperm quality and, in the future, may be used clinically to improve sperm selection methods.

Telomere length in offspring is determined by mitochondrial-nuclear communication at fertilization

The initial setting of telomere length during early life in each individual has a major influence on lifetime risk of aging-associated diseases; however there is limited knowledge of biological signals that regulate inheritance of telomere length, and whether it is modifiable is not known. We now show that when mitochondrial activity is disrupted in mouse zygotes, via exposure to 20% O2 or rotenone, telomere elongation between the 8-cell and blastocyst stage is impaired, with shorter telomeres apparent in the pluripotent Inner Cell Mass (ICM) and persisting after organogenesis. Identical defects of elevated mtROS in zygotes followed by impaired telomere elongation, occurred with maternal obesity or advanced age. We further demonstrate that telomere elongation during ICM formation is controlled by mitochondrial-nuclear communication at fertilization. Using mitochondrially-targeted therapeutics (BGP-15, MitoQ, SS-31, metformin) we demonstrate that it is possible to modulate the preimplantation telomere resetting process and restore deficiencies in neonatal telomere length.

BGP-15 improves quality of goat sperm by mitigating oxidative stress during cryopreservation

The objective of this study was to evaluate the effect of the addition of BGP-15 ((Z)-N'-(2-hydroxy-3-(piperidin-1-yl) propoxy) nicotinimidamide) on goat sperm during cryopreservation. The semen from six rams was diluted with a soybean lecithin-based extender containing different doses of BGP-15 (0, 50, 100, 150, and 200 μM). After the freeze-thawing process, sperm characteristics, plasma membrane integrity and functionality, acrosomal status, mitochondria activity, apoptosis status, and gene expression of post-thawed ram spermatozoa were assessed. Compared to fresh spermatozoa, the ultrastructure of frozen spermatozoa was damaged, and frozen spermatozoa had a reduced number of duplex microtubules with partially asymmetric distributions, localized disappearance of the central microtubule, and ambiguous submicrotubule structures. Moreover, the 100 μM BGP-15 treatment group had the highest percentage of viability, plasma membrane and acrosome integrities, and mitochondrial activity of frozen-thawed spermatozoa when compared to the control (P < 0.05). In the Computer-Assisted Semen Analyzer, sperm motility parameters were significantly increased in the BGP-15 treatment group against the control group (P < 0.05), except wobble. Similarly, BGP-15 treatment increased the levels of T-AOC, SOD, CAT, and GHS-Px and decreased the level of ROS which compared to controls (P < 0.05). Only the 100 μM BGP-15 treatment group had a higher MDA level than the control group (P < 0.05). In all BGP-15 treatment groups, the mRNA expressions of the ROMO1 gene were significantly reduced compared to controls (P < 0.05), and the mRNA expressions of the SMCP, MnSOD, and CuZnSOD genes were significantly increased (P < 0.05). While the difference in the mRNA expression of the SMOX gene between the 50 μM BGP-15 treatment group and the control group was not significant (P > 0.05). Moreover, the apoptosis rate of freeze-thawed spermatozoa significantly decreased in the 100 μM BGP-15 treatment group compared to the control (P < 0.05), while the MMP of freeze-thawed spermatozoa significantly enhanced in the 100 μM BGP-15 treatment group (P < 0.05). In conclusion, BGP-15 enhances cryo-protective effects on goat spermatozoa, and 100 μM BGP-15 addition to the extender during cryopreservation is beneficial to the goat breeding industry.

Mitochondrial activator BGP-15 protects sperm quality against oxidative damage and improves embryo developmental competence

OBJECTIVE

To study the efficacy of mitochondrial activator BGP-15 to preserve sperm quality and competence against cellular damage.

DESIGN

Spermatozoa from mice or humans were treated in vitro with BGP-15, and sperm quality markers were assessed. Spermatozoa from young (8-12 weeks old) or reproductively old (>14 months old) mice were treated with BGP-15 for 1 hour and assessed for sperm quality and preimplantation embryo development after in vitro fertilization. The safety of BGP-15 on offspring outcomes was assessed through embryo transfers. In parallel studies, spermatozoa from healthy (not infertile) men were incubated in hydrogen peroxide, to induce oxidative stress, plus increasing doses of BGP-15, and sperm quality was evaluated. Spermatozoa from patients undergoing assisted reproductive technology (ART) treatment were incubated in the optimized dose of BGP-15 for 30 minutes, and sperm quality was assessed.

SUBJECTS

C57BL/6 mice (N = 4-15 per group) for sperm quality and embryo development. CBAF1 mice (n = 6 per group) produced embryos for transfer. Human spermatozoa were from men with no infertility diagnosis (n = 14-20) or men undergoing ART (n = 33) at a local fertility clinic.

EXPOSURE

Mouse spermatozoa were treated with 10-μM BGP-15. Human spermatozoa were treated with BGP-15 at doses from 1 to 100 μM.

MAIN OUTCOME MEASURES

Sperm quality measures (mouse and human) included motility, mitochondrial membrane potential (JC-1 dye), deoxyribonucleic acid (DNA) fragmentation ("HALO" assay), and DNA oxidation (8-oxoguanine immunodetection). Mouse embryo and offspring measures included on-time development after in vitro fertilization, morphokinetic analysis, and blastocyst inner cell mass and trophectoderm cell number, and growth and development from birth to 21 days postnatally.

RESULTS

BGP-15 increased sperm motility and mitochondrial membrane potential and decreased DNA oxidation in old mice. BGP-15 improved on-time development of 2-cell and blastocyst embryos and increased the inner cell mass blastomere number. Embryos from BGP-15-treated mouse spermatozoa produced normal offspring. In human spermatozoa subjected to in vitro oxidative stress, BGP-15 increased motility by 45% and prevented DNA fragmentation (by 45%) and oxidative damage (by 60%). In spermatozoa from men attending a fertility clinic, BGP-15 increased motility by 12% and reduced both DNA oxidation and fragmentation by >20%.

CONCLUSION

BGP-15 protects sperm against cellular damage and has the potential to improve ART outcomes.

Neuronal and glial cell alterations involved in the retinal degeneration of the familial dysautonomia optic neuropathy

Familial dysautonomia (FD) is a rare genetic neurodevelopmental and neurodegenerative disorder. In addition to the autonomic and peripheral sensory neuropathies that challenge patient survival, one of the most debilitating symptoms affecting patients' quality of life is progressive blindness resulting from the steady loss of retinal ganglion cells (RGCs). Within the FD community, there is a concerted effort to develop treatments to prevent the loss of RGCs. However, the mechanisms underlying the death of RGCs are not well understood. To study the mechanisms underlying RGC death, Pax6-cre;Elp1loxp/loxp male and female mice and postmortem retinal tissue from an FD patient were used to explore the neuronal and non-neuronal cellular pathology associated with the FD optic neuropathy. Neurons, astrocytes, microglia, Müller glia, and endothelial cells were investigated using a combination of histological analyses. We identified a novel disruption of cellular homeostasis and gliosis in the FD retina. Beginning shortly after birth and progressing with age, the FD retina is marked by astrogliosis and perturbations in microglia, which coincide with vascular remodeling. These changes begin before the onset of RGC death, suggesting alterations in the retinal neurovascular unit may contribute to and exacerbate RGC death. We reveal for the first time that the FD retina pathology includes reactive gliosis, increased microglial recruitment to the ganglion cell layer (GCL), disruptions in the deep and superficial vascular plexuses, and alterations in signaling pathways. These studies implicate the neurovascular unit as a disease-modifying target for therapeutic interventions in FD.

ELP1, the Gene Mutated in Familial Dysautonomia, Is Required for Normal Enteric Nervous System Development and Maintenance and for Gut Epithelium Homeostasis

Familial dysautonomia (FD) is a rare sensory and autonomic neuropathy that results from a mutation in the ELP1 gene. Virtually all patients report gastrointestinal (GI) dysfunction and we have recently shown that FD patients have a dysbiotic gut microbiome and altered metabolome. These findings were recapitulated in an FD mouse model and moreover, the FD mice had reduced intestinal motility, as did patients. To understand the cellular basis for impaired GI function in FD, the enteric nervous system (ENS; both female and male mice) from FD mouse models was analyzed during embryonic development and adulthood. We show here that not only is Elp1 required for the normal formation of the ENS, but it is also required in adulthood for the regulation of both neuronal and non-neuronal cells and for target innervation in both the mucosa and in intestinal smooth muscle. In particular, CGRP innervation was significantly reduced as was the number of dopaminergic neurons. Examination of an FD patient's gastric biopsy also revealed reduced and disoriented axons in the mucosa. Finally, using an FD mouse model in which Elp1 was deleted exclusively from neurons, we found significant changes to the colon epithelium including reduced E-cadherin expression, perturbed mucus layer organization, and infiltration of bacteria into the mucosa. The fact that deletion of Elp1 exclusively in neurons is sufficient to alter the intestinal epithelium and perturb the intestinal epithelial barrier highlights a critical role for neurons in regulating GI epithelium homeostasis.

Metabolic Deficits in the Retina of a Familial Dysautonomia Mouse Model

Neurodegenerative retinal diseases such as glaucoma, diabetic retinopathy, Leber's hereditary optic neuropathy (LHON), and dominant optic atrophy (DOA) are marked by progressive death of retinal ganglion cells (RGC). This decline is promoted by structural and functional mitochondrial deficits, including electron transport chain (ETC) impairments, increased oxidative stress, and reduced energy (ATP) production. These cellular mechanisms associated with progressive optic nerve atrophy have been similarly observed in familial dysautonomia (FD) patients, who experience gradual loss of visual acuity due to the degeneration of RGCs, which is thought to be caused by a breakdown of mitochondrial structures, and a disruption in ETC function. Retinal metabolism plays a crucial role in meeting the elevated energetic demands of this tissue, and recent characterizations of FD patients' serum and stool metabolomes have indicated alterations in central metabolic processes and potential systemic deficits of taurine, a small molecule essential for retina and overall eye health. The present study sought to elucidate metabolic alterations that contribute to the progressive degeneration of RGCs observed in FD. Additionally, a critical subpopulation of retinal interneurons, the dopaminergic amacrine cells, mediate the integration and modulation of visual information in a time-dependent manner to RGCs. As these cells have been associated with RGC loss in the neurodegenerative disease Parkinson's, which shares hallmarks with FD, a targeted analysis of the dopaminergic amacrine cells and their product, dopamine, was also undertaken. One dimensional (1D) proton (1H) nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and retinal histology methods were employed to characterize retinae from the retina-specific Elp1 conditional knockout (CKO) FD mouse model (Pax6-Cre; Elp1LoxP/LoxP). Metabolite alterations correlated temporally with progressive RGC degeneration and were associated with reduced mitochondrial function, alterations in ATP production through the Cahill and mini-Krebs cycles, and phospholipid metabolism. Dopaminergic amacrine cell populations were reduced at timepoints P30-P90, and dopamine levels were 25-35% lower in CKO retinae compared to control retinae at P60. Overall, this study has expanded upon our current understanding of retina pathology in FD. This knowledge may apply to other retinal diseases that share hallmark features with FD and may help guide new avenues for novel non-invasive therapeutics to mitigate the progressive optic neuropathy in FD.

Elp1 function in placode-derived neurons is critical for proper trigeminal ganglion development

Background

The trigeminal nerve is the largest cranial nerve and functions in somatosensation. Cell bodies of this nerve are positioned in the trigeminal ganglion, which arises from the coalescence of neural crest and placode cells. While this dual cellular origin has been known for decades, the molecular mechanisms controlling trigeminal ganglion development remain obscure. We performed RNAsequencing on the forming chick trigeminal ganglion and identified Elongator acetyltransferase complex subunit 1 ( Elp1 ) for further study. Mutations in ELP1 cause familial dysautonomia (FD), a fatal disorder characterized by the presence of smaller trigeminal nerves and sensory deficits. While Elp1 has established roles in neurogenesis, its functions in placode cells during trigeminal gangliogenesis have not been investigated.

Results

To this end, we used morpholinos to deplete Elp1 from chick trigeminal placode cells. Elp1 knockdown decreased trigeminal ganglion size and led to aberrant innervation of the eye by placode-derived neurons. Trigeminal nerve branches exhibited fewer axons, and abnormal interactions between placode-derived neurons and neural crest cells were observed.

Conclusions

These findings reveal a new role for Elp1 in chick placode-derived neurons during trigeminal ganglion development. These results have potential high significance to provide new insights into trigeminal ganglion development and the etiology of FD.

Bullet points

Elp1 is expressed in undifferentiated neural crest cells and placode-derived neurons contributing to the trigeminal ganglion.Elp1 knockdown in trigeminal placode cells reduces trigeminal ganglion size.Elp1 depletion from trigeminal placode cells leads to aberrant target tissue innervation and disrupts proper neural crest-placodal neuron interactions in the trigeminal ganglion.

Grant sponsor and number

NIH R01DE024217 and NIH R03HD108480.

BGP-15 alleviates LPS-induced depression-like behavior by promoting mitophagy

The high prevalence of major depressive disorder (MDD) frequently imposes severe constraints on psychosocial functioning and detrimentally impacts overall well-being. Despite the growing interest in the hypothesis of mitochondrial dysfunction, the precise mechanistic underpinnings and therapeutic strategies remain unclear and require further investigation. In this study, an MDD model was established in mice using lipopolysaccharide (LPS). Our research findings demonstrated that LPS exposure induced depressive-like behaviors and disrupted mitophagy by diminishing the mitochondrial levels of PINK1/Parkin in the brains of mice. Furthermore, LPS exposure evoked the activation of the NLRP3 inflammasome, accompanied by a notable elevation in the concentrations of pro-inflammatory factors (TNF-α, IL-1β, and IL-6). Additionally, neuronal apoptosis was stimulated through the JNK/p38 pathway. The administration of BGP-15 effectively nullified the impact of LPS, corresponding to the amelioration of depressive-like phenotypes and restoration of mitophagy, prevention of neuronal injury and inflammation, and suppression of reactive oxygen species (ROS)-mediated NLRP3 inflammasome activation. Furthermore, we elucidated the involvement of mitophagy in BGP-15-attenuated depressive-like behaviors using the inhibitors targeting autophagy (3-MA) and mitophagy (Mdivi-1). Notably, these inhibitors notably counteracted the antidepressant and anti-inflammatory effects exerted by BGP-15. Based on the research findings, it can be inferred that the antidepressant properties of BGP-15 in LPS-induced depressive-like behaviors could potentially be attributed to the involvement of the mitophagy pathway. These findings offer a potential novel therapeutic strategy for managing MDD.

Acetylated tau exacerbates apoptosis by disturbing mitochondrial dynamics in HEK293 cells

An increase in tau acetylation at K274 and K281 and abnormal mitochondrial dynamics have been observed in the brains of Alzheimer's disease (AD) patients. Here, we constructed three types of tau plasmids, TauKQ (acetylated tau mutant, by mutating its K274/K281 into glutamine to mimic disease-associated lysine acetylation), TauKR (non-acetylated tau mutant, by mutating its K274/K281 into arginine), and TauWT (wild-type human full-length tau). By transfecting these tau plasmids in HEK293 cells, we found that TauWT and TauKR induced mitochondrial fusion by increasing the level of mitochondrial fusion proteins. Conversely, TauKQ induced mitochondrial fission by reducing mitochondrial fusion proteins, exacerbating mitochondrial dysfunction and apoptosis. BGP-15 ameliorated TauKQ-induced mitochondrial dysfunction and apoptosis by improving mitochondrial dynamics. Our findings suggest that acetylation of K274/281 represents an important post-translational modification site regulating mitochondrial dynamics, and that BGP-15 holds potential as a therapeutic agent for mitochondria-associated diseases such as AD.

Oocyte Aging: A Multifactorial Phenomenon in A Unique Cell

The oocyte is considered to be the largest cell in mammalian species. Women hoping to become pregnant face a ticking biological clock. This is becoming increasingly challenging as an increase in life expectancy is accompanied by the tendency to conceive at older ages. With advancing maternal age, the fertilized egg will exhibit lower quality and developmental competence, which contributes to increased chances of miscarriage due to several causes such as aneuploidy, oxidative stress, epigenetics, or metabolic disorders. In particular, heterochromatin in oocytes and with it, the DNA methylation landscape undergoes changes. Further, obesity is a well-known and ever-increasing global problem as it is associated with several metabolic disorders. More importantly, both obesity and aging negatively affect female reproduction. However, among women, there is immense variability in age-related decline of oocytes' quantity, developmental competence, or quality. Herein, the relevance of obesity and DNA-methylation will be discussed as these aspects have a tremendous effect on female fertility, and it is a topic of continuous and widespread interest that has yet to be fully addressed for the mammalian oocyte.

Acetylated tau exacerbates learning and memory impairment by disturbing with mitochondrial homeostasis

Increased tau acetylation at K274 and K281 has been observed in the brains of Alzheimer's disease (AD) patients and animal models, and mitochondrial dysfunction are noticeable and early features of AD. However, the effect of acetylated tau on mitochondria has been unclear until now. Here, we constructed three type of tau forms, acetylated tau mutant by mutating its K274/K281 into Glutamine (TauKQ) to mimic disease-associated lysine acetylation, the non-acetylation tau mutant by mutating its K274/K281 into Arginine (TauKR) and the wild-type human full-length tau (TauWT). By overexpression of these tau forms in vivo and in vitro, we found that, TauKQ induced more severe cognitive deficits with neuronal loss, dendritic plasticity damage and mitochondrial dysfunctions than TauWT. Unlike TauWT induced mitochondria fusion, TauKQ not only induced mitochondria fission by decreasing mitofusion proteins, but also inhibited mitochondrial biogenesis via reduction of PGC-1a/Nrf1/Tfam levels. TauKR had no significant difference in the cognitive and mitochondrial abnormalities compared with TauWT. Treatment with BGP-15 rescued impaired learning and memory by attenuation of mitochondrial dysfunction, neuronal loss and dendritic complexity damage, which caused by TauKQ. Our data suggested that, acetylation at K274/281 was an important post translational modification site for tau neurotoxicity, and BGP-15 is a potential therapeutic drug for AD.

A Comprehensive NMR Analysis of Serum and Fecal Metabolites in Familial Dysautonomia Patients Reveals Significant Metabolic Perturbations

Central metabolism has a profound impact on the clinical phenotypes and penetrance of neurological diseases such as Alzheimer’s (AD) and Parkinson’s (PD) diseases, Amyotrophic Lateral Sclerosis (ALS) and Autism Spectrum Disorder (ASD). In contrast to the multifactorial origin of these neurological diseases, neurodevelopmental impairment and neurodegeneration in Familial Dysautonomia (FD) results from a single point mutation in the ELP1 gene. FD patients represent a well-defined population who can help us better understand the cellular networks underlying neurodegeneration, and how disease traits are affected by metabolic dysfunction, which in turn may contribute to dysregulation of the gut–brain axis of FD. Here, 1H NMR spectroscopy was employed to characterize the serum and fecal metabolomes of FD patients, and to assess similarities and differences in the polar metabolite profiles between FD patients and healthy relative controls. Findings from this work revealed noteworthy metabolic alterations reflected in energy (ATP) production, mitochondrial function, amino acid and nucleotide catabolism, neurosignaling molecules, and gut-microbial metabolism. These results provide further evidence for a close interconnection between metabolism, neurodegeneration, and gut microbiome dysbiosis in FD, and create an opportunity to explore whether metabolic interventions targeting the gut–brain–metabolism axis of FD could be used to redress or slow down the progressive neurodegeneration observed in FD patients.

Norepinephrine transporter defects lead to sympathetic hyperactivity in Familial Dysautonomia models

Familial dysautonomia (FD), a rare neurodevelopmental and neurodegenerative disorder affects the sympathetic and sensory nervous system. Although almost all patients harbor a mutation in ELP1, it remains unresolved exactly how function of sympathetic neurons (symNs) is affected; knowledge critical for understanding debilitating disease hallmarks, including cardiovascular instability or dysautonomic crises, that result from dysregulated sympathetic activity. Here, we employ the human pluripotent stem cell (hPSC) system to understand symN disease mechanisms and test candidate drugs. FD symNs are intrinsically hyperactive in vitro, in cardiomyocyte co-cultures, and in animal models. We report reduced norepinephrine transporter expression, decreased intracellular norepinephrine (NE), decreased NE re-uptake, and excessive extracellular NE in FD symNs. SymN hyperactivity is not a direct ELP1 mutation result, but may connect to NET via RAB proteins. We found that candidate drugs lowered hyperactivity independent of ELP1 modulation. Our findings may have implications for other symN disorders and may allow future drug testing and discovery.

Rescue of a familial dysautonomia mouse model by AAV9-Exon-specific U1 snRNA

Familial dysautonomia (FD) is a currently untreatable, neurodegenerative disease caused by a splicing mutation (c.2204+6T>C) that causes skipping of exon 20 of the elongator complex protein 1 (ELP1) pre-mRNA. Here, we used adeno-associated virus serotype 9 (AAV9-U1-FD) to deliver an exon-specific U1 (ExSpeU1) small nuclear RNA, designed to cause inclusion of ELP1 exon 20 only in those cells expressing the target pre-mRNA, in a phenotypic mouse model of FD. Postnatal systemic and intracerebral ventricular treatment in these mice increased the inclusion of ELP1 exon 20. This also augmented the production of functional protein in several tissues including brain, dorsal root, and trigeminal ganglia. Crucially, the treatment rescued most of the FD mouse mortality before one month of age (89% vs 52%). There were notable improvements in ataxic gait as well as renal (serum creatinine) and cardiac (ejection fraction) functions. RNA-seq analyses of dorsal root ganglia from treated mice and human cells overexpressing FD-ExSpeU1 revealed only minimal global changes in gene expression and splicing. Overall then, our data prove that AAV9-U1-FD is highly specific and will likely be a safe and effective therapeutic strategy for this debilitating disease.

Developmental regulation of neuronal gene expression by Elongator complex protein 1 dosage

Familial dysautonomia (FD), a hereditary sensory and autonomic neuropathy, is caused by a mutation in the Elongator complex protein 1 (ELP1) gene that leads to a tissue-specific reduction of ELP1 protein. Our work to generate a phenotypic mouse model for FD headed to the discovery that homozygous deletion of the mouse Elp1 gene leads to embryonic lethality prior to mid-gestation. Given that FD is caused by a reduction, not loss, of ELP1, we generated two new mouse models by introducing different copy numbers of the human FD ELP1 transgene into the Elp1 knockout mouse (Elp1-/-) and observed that human ELP1 expression rescues embryonic development in a dose-dependent manner. We then conducted a comprehensive transcriptome analysis in mouse embryos to identify genes and pathways whose expression correlates with the amount of ELP1. We found that ELP1 is essential for the expression of genes responsible for nervous system development. Further, gene length analysis of the differentially expressed genes showed that the loss of Elp1 mainly impacts the expression of long genes and that by gradually restoring Elongator, their expression is progressively rescued. Finally, through evaluation of co-expression modules, we identified gene sets with unique expression patterns that depended on ELP1 expression.

Female reproductive life span is extended by targeted removal of fibrotic collagen from the mouse ovary

The female ovary contains a finite number of oocytes, and their release at ovulation becomes sporadic and disordered with aging and with obesity, leading to loss of fertility. Understanding the molecular defects underpinning this pathology is essential as age of childbearing and obesity rates increase globally. We identify that fibrosis within the ovarian stromal compartment is an underlying mechanism responsible for impaired oocyte release, which is initiated by mitochondrial dysfunction leading to diminished bioenergetics, oxidative damage, inflammation, and collagen deposition. Furthermore, antifibrosis drugs (pirfenidone and BGP-15) eliminate fibrotic collagen and restore ovulation in reproductively old and obese mice, in association with dampened M2 macrophage polarization and up-regulated MMP13 protease. This is the first evidence that ovarian fibrosis is reversible and indicates that drugs targeting mitochondrial metabolism may be a viable therapeutic strategy for women with metabolic disorders or advancing age to maintain ovarian function and extend fertility.

Elp1 is required for development of visceral sensory peripheral and central circuitry

Cardiovascular instability and a blunted respiratory drive in hypoxic conditions are hallmark features of the genetic sensory and autonomic neuropathy, familial dysautonomia (FD). FD results from a mutation in the gene ELP1, the encoded protein of which is a scaffolding subunit of the six-subunit Elongator complex. In mice, we and others have shown that Elp1 is essential for the normal development of neural crest-derived dorsal root ganglia sensory neurons. Whether Elp1 is also required for development of ectodermal placode-derived visceral sensory receptors, which are required for normal baroreception and chemosensory responses, has not been investigated. Using mouse models for FD, we here show that the entire circuitry underlying baroreception and chemoreception is impaired due to a requirement for Elp1 in the visceral sensory neuron ganglia, as well as for normal peripheral target innervation, and in their central nervous system synaptic partners in the medulla. Thus, Elp1 is required in both placode- and neural crest-derived sensory neurons, and its reduction aborts the normal development of neuronal circuitry essential for autonomic homeostasis and interoception.

This article has an associated First Person interview with the first author of the paper.

Summary: Our data indicate that Elp1 is required in both placode- and neural crest-derived sensory neurons, and that it exerts comparable effects, including survival, axonal morphology and target innervation in both lineages.

Loss of Elp1 disrupts trigeminal ganglion neurodevelopment in a model of familial dysautonomia

Familial dysautonomia (FD) is a sensory and autonomic neuropathy caused by mutations in elongator complex protein 1 (ELP1). FD patients have small trigeminal nerves and impaired facial pain and temperature perception. These signals are relayed by nociceptive neurons in the trigeminal ganglion, a structure that is composed of both neural crest- and placode-derived cells. Mice lacking Elp1 in neural crest derivatives ('Elp1 CKO') are born with small trigeminal ganglia, suggesting Elp1 is important for trigeminal ganglion development, yet the function of Elp1 in this context is unknown. We demonstrate that Elp1, expressed in both neural crest- and placode-derived neurons, is not required for initial trigeminal ganglion formation. However, Elp1 CKO trigeminal neurons exhibit abnormal axon outgrowth and deficient target innervation. Developing nociceptors expressing the receptor TrkA undergo early apoptosis in Elp1 CKO, while TrkB- and TrkC-expressing neurons are spared, indicating Elp1 supports the target innervation and survival of trigeminal nociceptors. Furthermore, we demonstrate that specific TrkA deficits in the Elp1 CKO trigeminal ganglion reflect the neural crest lineage of most TrkA neurons versus the placodal lineage of most TrkB and TrkC neurons. Altogether, these findings explain defects in cranial gangliogenesis that may lead to loss of facial pain and temperature sensation in FD.

Mitochondria-targeted therapeutics, MitoQ and BGP-15, reverse aging-associated meiotic spindle defects in mouse and human oocytes

STUDY QUESTION

Do mitochondria-targeted therapies reverse ageing- and oxidative stress-induced spindle defects in oocytes from mice and humans?

SUMMARY ANSWER

Exposure to MitoQ or BGP-15 during IVM protected against spindle and chromosomal defects in mouse oocytes exposed to oxidative stress or derived from reproductively aged mice whilst MitoQ promoted nuclear maturation and protected against chromosomal misalignments in human oocytes.

WHAT IS KNOWN ALREADY

Spindle and chromosomal abnormalities in oocytes are more prevalent with maternal aging, increasing the risk of aneuploidy, miscarriage and genetic disorders such as Down's syndrome. The origin of compromised oocyte function may be founded in mitochondrial dysfunction and increased reactive oxygen species (ROS).

STUDY DESIGN, SIZE, DURATION

Oocytes from young and old mice were treated with MitoQ and/or BGP-15 during IVM. To directly induce mitochondrial dysfunction, oocytes were treated with H2O2, and then treated the MitoQ and/or BGP-15. Immature human oocytes were cultured with or without MitoQ. Each experiment was repeated at least three times, and data were analyzed by unpaired-sample t-test or chi-square test.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Immature germinal vesicle (GV) stage oocytes from 1-, 12- and 18-month-old mice were obtained from preovulatory ovarian follicles. Oocytes were treated with MitoQ and/or BGP-15 during IVM. GV-stage human oocytes were cultured with or without MitoQ. Mitochondrial membrane potential and mitochondrial ROS were measured by live-cell imaging. Meiotic spindle and chromosome alignments were visualized by immunofluorescent labeling of fixed oocytes and the 3-dimensional images were analyzed by Imaris.

MAIN RESULTS AND THE ROLE OF CHANCE

MitoQ or BGP-15 during IVM protects against spindle and chromosomal defects in oocytes exposed to oxidative stress and in oocytes from aged mice (P < 0.001). In human oocytes, the presence of MitoQ during IVM promoted nuclear maturation and had a similar positive effect in protecting against chromosomal misalignments (P < 0.001).

LIMITATIONS, REASONS FOR CAUTION

Our study identifies two excellent candidates that may help to improve fertility in older women. However, these potential therapies must be tested for efficacy in clinical IVM systems, and undergo thorough examination of resultant offspring in preclinical models before utilization.

WIDER IMPLICATIONS OF THE FINDINGS

Our results using in-vitro systems for oocyte maturation in both mouse and human provide proof of principle that mitochondrially targeted molecules such as MitoQ and BGP-15 may represent a novel therapeutic approach against maternal aging-related spindle and chromosomal abnormalities.

STUDY FUNDING/COMPETING INTEREST(S)

The project was financially supported by the National Health and Medical Research Council and Australian Research Council, Australia. U.A.-Z. was supported by the Iraqi Higher Education and Scientific Research Ministry PhD scholarship and O.C. was supported by TUBITAK-1059B191601275. M.P.M. consults for MitoQ Inc. and holds patents in mitochondria-targeted therapies. R.L.R. is an inventor on patents relating to the use of BGP-15 to improve gamete quality.

TRIAL REGISTRATION NUMBER

N/A.

Expanding the Genotypic Spectrum of Congenital Sensory and Autonomic Neuropathies Using Whole-Exome Sequencing

Objective

To test the hypothesis that many patients presenting with congenital insensitivity to pain have lesser known or unidentified mutations not captured by conventional genetic panels, we performed whole-exome sequencing in a cohort of well-characterized patients with a clinical diagnosis of congenital hereditary sensory and autonomic neuropathy with unrevealing conventional genetic testing.

Methods

We performed whole-exome sequencing (WES) in 13 patients with congenital impaired or absent sensation to pain and temperature with no identified molecular diagnosis from a conventional genetic panel. Patients underwent a comprehensive phenotypic assessment including autonomic function testing, and neurologic and ophthalmologic examinations.

Results

We identified known or likely pathogenic genetic causes of congenital insensitivity to pain in all 13 patients, spanning 9 genes, the vast majority of which were inherited in an autosomal recessive manner. These included known pathogenic variants (3 patients harboring mutations in TECPR2 and SCN11A), suspected pathogenic variants in genes described to cause congenital sensory and autonomic syndromes (7 patients harboring variants in NGF, LIFR, SCN9A, and PRDM12), and likely pathogenic variants in novel genes (4 patients harboring variants in SMPDL3A, PLEKHN1, and SCN10A).

Conclusions

Our results expand the genetic landscape of congenital sensory and autonomic neuropathies. Further validation of some identified variants should confirm their pathogenicity. WES should be clinically considered to expedite diagnosis, reduce laboratory investigations, and guide enrollment in future gene therapy trials.

Neurotherapeutic Effect of Inula britannica var. Chinensis against H2O2-Induced Oxidative Stress and Mitochondrial Dysfunction in Cortical Neurons

Inula britannica var. chinensis (IBC) has been used as a traditional medicinal herb to treat inflammatory diseases. Although its anti-inflammatory and anti-oxidative effects have been reported, whether IBC exerts neuroprotective effects and the related mechanisms in cortical neurons remain unknown. In this study, we investigated the effects of different concentrations of IBC extract (5, 10, and 20 µg/mL) on cortical neurons using a hydrogen peroxide (H₂O₂)-induced injury model. Our results demonstrate that IBC can effectively enhance neuronal viability under in vitro-modeled reaction oxygen species (ROS)-generating conditions by inhibiting mitochondrial ROS production and increasing adenosine triphosphate level in H₂O₂-treated neurons. Additionally, we confirmed that neuronal death was attenuated by improving the mitochondrial membrane potential status and regulating the expression of cytochrome c, a protein related to cell death. Furthermore, IBC increased the expression of brain-derived neurotrophic factor and nerve growth factor. Furthermore, IBC inhibited the loss and induced the production of synaptophysin, a major synaptic vesicle protein. This study is the first to demonstrate that IBC exerts its neuroprotective effect by reducing mitochondria-associated oxidative stress and improving mitochondrial dysfunction.

Myocardial ischaemia reperfusion injury and cardioprotection in the presence of sensory neuropathy: Therapeutic options

During the last decades, mortality from acute myocardial infarction has been dramatically reduced. However, the incidence of post-infarction heart failure is still increasing. Cardioprotection by ischaemic conditioning had been discovered more than three decades ago. Its clinical translation, however, is still an unmet need. This is mainly due to the disrupted cardioprotective signalling pathways in the presence of different cardiovascular risk factors, co-morbidities and the medication being taken. Sensory neuropathy is one of the co-morbidities that has been shown to interfere with cardioprotection. In the present review, we summarize the diverse aetiology of sensory neuropathies and the mechanisms by which these neuropathies may interfere with ischaemic heart disease and cardioprotective signalling. Finally, we suggest future therapeutic options targeting both ischaemic heart and sensory neuropathy simultaneously. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

Development of the Autonomic Nervous System: Clinical Implications

Investigations of the cellular and molecular mechanisms that mediate the development of the autonomic nervous system have identified critical genes and signaling pathways that, when disrupted, cause disorders of the autonomic nervous system. This review summarizes our current understanding of how the autonomic nervous system emerges from the organized spatial and temporal patterning of precursor cell migration, proliferation, communication, and differentiation, and discusses potential clinical implications for developmental disorders of the autonomic nervous system, including familial dysautonomia, Hirschsprung disease, Rett syndrome, and congenital central hypoventilation syndrome.

Retina-specific loss of Ikbkap/Elp1 causes mitochondrial dysfunction that leads to selective retinal ganglion cell degeneration in a mouse model of familial dysautonomia

Familial dysautonomia (FD) is an autosomal recessive disorder marked by developmental and progressive neuropathies. It is caused by an intronic point-mutation in the IKBKAP/ELP1 gene, which encodes the inhibitor of κB kinase complex-associated protein (IKAP, also called ELP1), a component of the elongator complex. Owing to variation in tissue-specific splicing, the mutation primarily affects the nervous system. One of the most debilitating hallmarks of FD that affects patients' quality of life is progressive blindness. To determine the pathophysiological mechanisms that are triggered by the absence of IKAP in the retina, we generated retina-specific Ikbkap conditional knockout (CKO) mice using Pax6-Cre, which abolished Ikbkap expression in all cell types of the retina. Although sensory and autonomic neuropathies in FD are known to be developmental in origin, the loss of IKAP in the retina did not affect its development, demonstrating that IKAP is not required for retinal development. The loss of IKAP caused progressive degeneration of retinal ganglion cells (RGCs) by 1 month of age. Mitochondrial membrane integrity was breached in RGCs, and later in other retinal neurons. In Ikbkap CKO retinas, mitochondria were depolarized, and complex I function and ATP were significantly reduced. Although mitochondrial impairment was detected in all Ikbkap-deficient retinal neurons, RGCs were the only cell type to degenerate; the survival of other retinal neurons was unaffected. This retina-specific FD model is a useful in vivo model for testing potential therapeutics for mitigating blindness in FD. Moreover, our data indicate that RGCs and mitochondria are promising targets.

Summary: The elongator subunit IKBKAP/ELP1 is not required for development, but is essential for maintaining mitochondrial function and retina morphology. Loss of this subunit causes progressive, selective degeneration of retinal ganglion cells.

Mitochondrial regulation of [Ca2+]i oscillations during cell cycle resumption of the second meiosis of oocyte

Oocyte is arrested at metaphase of the second meiosis until fertilization switching on [Ca²⁺]i oscillations. Oocyte activation inefficiency is the most challenging problem for failed fertilization and embryonic development. Mitochondrial function and intracellular [Ca²⁺]i oscillations are two critical factors for the oocyte's developmental potential. We aimed to understand the possible correlation between mitochondrial function and [Ca²⁺]i oscillations in oocytes. To this end, mitochondrial uncoupler CCCP which damages mitochondrial function and two small molecule mitochondrial agonists, L-carnitine (LC) and BGP-15, were used to examine the regulation of [Ca²⁺]i by mitochondrial functions. With increasing CCCP concentrations, [Ca²⁺]i oscillations were gradually diminished and high concentrations of CCCP led to oocyte death. LC enhanced mitochondrial membrane potential and [Ca²⁺]i oscillations and even improved the damage induced by CCCP, however, BGP-15 had no beneficial effect on oocyte activation. We have found that mitochondrial function plays a vital role in the generation of [Ca²⁺]i oscillations in oocytes, and thus mitochondria may interact with the ER to generate [Ca²⁺]i oscillations during oocyte activation. Improvement of mitochondrial functions with small molecules can be expected to improve oocyte activation and embryonic development in infertile patients without invasive micromanipulation.

Structural insights into the function of Elongator

Conserved from yeast to humans, Elongator is a protein complex implicated in multiple processes including transcription regulation, α-tubulin acetylation, and tRNA modification, and its defects have been shown to cause human diseases such as familial dysautonomia. Elongator consists of two copies of six core subunits (Elp1, Elp2, Elp3, Elp4, Elp5, and Elp6) that are organized into two subcomplexes: Elp1/2/3 and Elp4/5/6 and form a stable assembly of ~ 850 kDa in size. Although the catalytic subunit of Elongator is Elp3, which contains a radical S-adenosyl-L-methionine (SAM) domain and a putative histone acetyltransferase domain, the Elp4/5/6 subcomplex also possesses ATP-modulated tRNA binding activity. How at the molecular level, Elongator performs its multiple functions and how the different subunits regulate Elongator's activities remains poorly understood. Here, we provide an overview of the proposed functions of Elongator and describe how recent structural studies provide new insights into the mechanism of action of this multifunctional complex.

Animal and cellular models of familial dysautonomia

Since Riley and Day first described the clinical phenotype of patients with familial dysautonomia (FD) over 60 years ago, the field has made considerable progress clinically, scientifically, and translationally in treating and understanding the etiology of FD. FD is classified as a hereditary sensory and autonomic neuropathy (HSAN type III) and is both a developmental and a progressive neurodegenerative condition that results from an autosomal recessive mutation in the gene IKBKAP, also known as ELP1. FD primarily impacts the peripheral nervous system but also manifests in central nervous system disruption, especially in the retina and optic nerve. While the disease is rare, the rapid progress being made in elucidating the molecular and cellular mechanisms mediating the demise of neurons in FD should provide insight into degenerative pathways common to many neurological disorders. Interestingly, the protein encoded by IKBKAP/ELP1, IKAP or ELP1, is a key scaffolding subunit of the six-subunit Elongator complex, and variants in other Elongator genes are associated with amyotrophic lateral sclerosis (ALS), intellectual disability, and Rolandic epilepsy. Here we review the recent model systems that are revealing the molecular and cellular pathophysiological mechanisms mediating FD. These powerful model systems can now be used to test targeted therapeutics for mitigating neuronal loss in FD and potentially other disorders.