Reduction of spermine synthase enhances autophagy to suppress Tau accumulation.

Precise polyamine metabolism regulation is vital for cells and organisms. Mutations in spermine synthase (SMS) cause Snyder-Robinson intellectual disability syndrome (SRS), characterized by significant spermidine accumulation and autophagy blockage in the nervous system. Emerging evidence connects polyamine metabolism with other autophagy-related diseases, such as Tauopathy, however, the functional intersection between polyamine metabolism and autophagy in the context of these diseases remains unclear. Here, we altered SMS expression level to investigate the regulation of autophagy by modulated polyamine metabolism in Tauopathy in Drosophila and human cellular models. Interestingly, while complete loss of Drosophila spermine synthase (dSms) impairs lysosomal function and blocks autophagic flux recapitulating SRS disease phenotype, partial loss of dSms enhanced autophagic flux, reduced Tau protein accumulation, and led to extended lifespan and improved climbing performance in Tauopathy flies. Measurement of polyamine levels detected a mild elevation of spermidine in flies with partial loss of dSms. Similarly, in human neuronal or glial cells, partial loss of SMS by siRNA-mediated knockdown upregulated autophagic flux and reduced Tau protein accumulation. Importantly, proteomics analysis of postmortem brain tissue from Alzheimer's disease (AD) patients showed a significant albeit modest elevation of SMS level. Taken together, our study uncovers a functional correlation between polyamine metabolism and autophagy in AD: SMS reduction upregulates autophagy, suppresses Tau accumulation, and ameliorates neurodegeneration and cell death. These findings provide a new potential therapeutic target for AD.

Dodecyl creatine ester therapy: from promise to reality.

Pathogenic variants in SLC6A8, the gene which encodes creatine transporter SLC6A8, prevent creatine uptake in the brain and result in a variable degree of intellectual disability, behavioral disorders (e.g., autism spectrum disorder), epilepsy, and severe speech and language delay. There are no treatments to improve neurodevelopmental outcomes for creatine transporter deficiency (CTD). In this spotlight, we summarize recent advances in innovative molecules to treat CTD, with a focus on dodecyl creatine ester, the most promising drug candidate.

[Clinical features and genetic analysis of 17 Chinese pedigrees affected with X-linked intellectual disability].

OBJECTIVE: To analyze the clinical features and genetic etiology of 17 Chinese pedigrees affected with X-linked intellectual disability (XLID). METHODS: Seventeen pedigrees affected with unexplained intellectual disability which had presented at Henan Provincial People's Hospital from May 2021 to May 2023 were selected as the study subjects. Clinical data of the probands and their pedigree members were collected. Trio-whole exome sequencing (Trio-WES), Sanger sequencing and X chromosome inactivation (XCI) analysis were carried out. Pathogenicity of candidate variants was predicted based on the guidelines from the American College of Medical Genetics and Genomics and co-segregation analysis. RESULTS: The 17 probands, including 9 males and 8 females with an age ranging from 0.6 to 8 years old, had all shown mental retardation and developmental delay. Fourteen variants were detected by genetic testing, which included 4 pathogenic variants (MECP2: c.502C>T, MECP2: c.916C>T/c.806delG, IQSEC2: c.1417G>T), 4 likely pathogenic variants (MECP2: c.1157_1197del/c.925C>T, KDM5C: c.2128A>T, SLC6A8: c.1631C>T) and 6 variants of uncertain significance (KLHL15: c.26G>C, PAK3: c.970A>G/c.1520G>A, GRIA3: c.2153C>G, TAF1: c.2233T>G, HUWE1: c.10301T>A). The PAK3: c.970A>G, GRIA3: c.2153C>G and TAF1: c.2233T>G variants were considered as the genetic etiology for pedigrees 12, 14 and 15 by co-segregation analysis, respectively. The proband of pedigree 13 was found to have non-random XCI (81:19). Therefore, the PAK3: c.1520G>A variant may underlie its pathogenesis. CONCLUSION: Trio-WES has attained genetic diagnosis for the 17 XLID pedigrees. Sanger sequencing and XCI assay can provide auxiliary tests for the diagnosis of XLID.

Clinical Characteristics, Developmental Trajectory, and Caregiver Burden of Patients With Creatine Transporter Deficiency (SLC6A8).

BACKGROUND AND OBJECTIVES: Creatine transporter deficiency (CTD) is a rare X-linked genetic disorder characterized by intellectual disability (ID). We evaluated the clinical characteristics and trajectory of patients with CTD and the impact of the disease on caregivers to identify relevant endpoints for future therapeutic trials. METHODS: As part of a French National Research Program, patients with CTD were included based on (1) a pathogenic SLC6A8 variant and (2) ID and/or autism spectrum disorder. Families and patients were referred by the physician who ordered the genetic analysis through Reference Centers of ID from rare causes and inherited metabolic diseases. After we informed the patients and their parents/guardians about the study, all of them gave written consent and were included. A control group of age-matched and sex-matched patients with Fragile X syndrome was also included. Physical examination, neuropsychological assessments, and caregiver impact were assessed. All data were analyzed using R software. RESULTS: Thirty-one patients (27 male, 4 female) were included (25/31 aged 18 years or younger). Most of the patients (71%) had symptoms at <24 months of age. The mean age at diagnosis was 6.5 years. Epilepsy occurred in 45% (mean age at onset: 8 years). Early-onset behavioral disorder occurred in 82%. Developmental trajectory was consistently delayed (fine and gross motor skills, language, and communication/sociability). Half of the patients with CTD had axial hypotonia during the first year of life. All patients were able to walk without help, but 7/31 had ataxia and only 14/31 could walk tandem gait. Most of them had abnormal fine motor skills (27/31), and most of them had language impairment (30/31), but 12/23 male patients (52.2%) completed the Peabody Picture Vocabulary Test. Approximately half (14/31) had slender build. Most of them needed nursing care (20/31), generally 1-4 h/d. Adaptive assessment (Vineland) confirmed that male patients with CTD had moderate-to-severe ID. Most caregivers (79%) were at risk of burnout, as shown by Caregiver Burden Inventory (CBI) > 36 (significantly higher than for patients with Fragile X syndrome) with a high burden of time dependence. DISCUSSION: In addition to clinical endpoints, such as the assessment of epilepsy and the developmental trajectory of the patient, the Vineland scale, PPVT5, and CBI are of particular interest as outcome measures for future trials. TRIAL REGISTRATION INFORMATION: ANSM Registration Number 2010-A00327-32.

Increased Proteolytic Activity of Serratia marcescens Clinical Isolate HU1848 Is Associated with Higher eepR Expression.

Serratia marcescens is a global opportunistic pathogen. In vitro cytotoxicity of this bacterium is mainly related to metalloprotease serralysin (PrtS) activity. Proteolytic capability varies among the different isolates. Here, we characterized protease production and transcriptional regulators at 37°C of two S. marcescens isolates from bronchial expectorations, HU1848 and SmUNAM836. As a reference strain the insect pathogen S. marcescens Db10 was included. Zymography of supernatant cultures revealed a single (SmUNAM836) or double proteolytic zones (HU1848 and Db10). Mass spectrometry confirmed the identity of PrtS and the serralysin-like protease SlpB from supernatant samples. Elevated proteolytic activity and prtS expression were evidenced in the HU1848 strain through azocasein degradation and qRT-PCR, respectively. Evaluation of transcriptional regulators revealed higher eepR expression in HU1848, whereas cpxR and hexS transcriptional levels were similar between studied strains. Higher eepR expression in HU1848 was further confirmed through an in vivo transcriptional assay. Moreover, two putative CpxR binding motifs were identified within the eepR regulatory region. EMSA validated the interaction of CpxR with both motifs. The evaluation of eepR transcription in a cpxR deletion strain indicated that CpxR negatively regulates eepR. Sequence conservation suggests that regulation of eepR by CpxR is common along S. marcescens species. Overall, our data incorporates CpxR to the complex regulatory mechanisms governing eepR expression and associates the increased proteolytic activity of the HU1848 strain with higher eepR transcription. Based on the global impact of EepR in secondary metabolites production, our work contributes to understanding virulence factors variances across S. marcescens isolates.

PHF6-mediated transcriptional control of NSC via Ephrin receptors is impaired in the intellectual disability syndrome BFLS.

The plant homeodomain zinc-finger protein, PHF6, is a transcriptional regulator, and PHF6 germline mutations cause the X-linked intellectual disability (XLID) Börjeson-Forssman-Lehmann syndrome (BFLS). The mechanisms by which PHF6 regulates transcription and how its mutations cause BFLS remain poorly characterized. Here, we show genome-wide binding of PHF6 in the developing cortex in the vicinity of genes involved in central nervous system development and neurogenesis. Characterization of BFLS mice harbouring PHF6 patient mutations reveals an increase in embryonic neural stem cell (eNSC) self-renewal and a reduction of neural progenitors. We identify a panel of Ephrin receptors (EphRs) as direct transcriptional targets of PHF6. Mechanistically, we show that PHF6 regulation of EphR is impaired in BFLS mice and in conditional Phf6 knock-out mice. Knockdown of EphR-A phenocopies the PHF6 loss-of-function defects in altering eNSCs, and its forced expression rescues defects of BFLS mice-derived eNSCs. Our data indicate that PHF6 directly promotes Ephrin receptor expression to control eNSC behaviour in the developing brain, and that this pathway is impaired in BFLS.

[Genetic analysis and prenatal diagnosis for a Chinese pedigree affected with co-morbid Ornithine carbamoyl transferase deficiency and MECP2 duplication syndrome].

OBJECTIVE: To explore the genetic basis for a Chinese pedigree affected with co-morbid Ornithine carbamoyl transferase deficiency (OTCD) and MECP2 duplication syndrome. METHODS: A proband who was admitted to the Neonatal Intensive Care Unit of Gansu Provincial Maternal and Child Health Care Hospital on December 19, 2017 was selected as the study subject. High-throughput sequencing and multiplex ligation-dependent probe amplification (MLPA) were carried out for her pedigree, and short tandem repeat-based linkage analysis and chromosome copy number variation sequencing (CNV-seq) were used for the prenatal diagnosis. RESULTS: The proband, a 3-day-old female, was found to harbor heterozygous deletion of exons 7-9 of the OTC gene. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was classified as likely pathogenic (PVS1+PM2_Supporting+PP4). The proband was diagnosed with OTCD , which was in keeping with her acute encephalopathy and metabolic abnormalities (manifesting as hyperammonemia, decreased blood citrulline, and increased urine orotic acid). Prenatal diagnosis was carried out for the subsequent pregnancy. The fetus did not harbor the exons 7-9 deletion of the OTC gene, but was found to carry a duplication in Xq28 region (which encompassed the whole region of MECP2 duplication syndrome) and was positive for the SRY sequence. The same duplication was also found in the proband and her mother. Considering the possible existence of X-chromosome inactivation, the proband was diagnosed with two X-linked recessive disorders including OTCD and MECP2 duplication syndrome, and the fetus was determined as a male affected with the MECP2 duplication syndrome. CONCLUSION: Discoveries of the pathogenic variants underlying the OTCD and MECP2 duplication syndrome have enabled clinical intervention, treatment, genetic counseling and prenatal diagnosis for this pedigree.

A decentralized approach for the aerial manipulator robust trajectory tracking.

This paper introduces a new decentralized control strategy for an unmanned aerial manipulator (UAM) constrained to the vertical plane. The control strategy comprises two loops: the first compensates for the aerial vehicle's impact on the manipulator; and the second one implements independent controllers for the aerial vehicle and the manipulator. The controller for the aerial vehicle includes an estimator to compensate for the dynamic influence of the manipulator, even if it is affected by external wind-gust disturbances. The manipulator has two revolute joints; however, it is modeled as an dynamically equivalent manipulator, with one revolute and one prismatic joint. The proposed control strategy's performance is evaluated using a simulator that includes the vehicle's aerodynamics and the manipulator's contact force and moment.

Movement Disorder Perspectives on Monocarboxylate 8 Deficiency: A Case Series of 3 Colombian Patients with Allan-Herndon-Dudley Syndrome.

BACKGROUND: Deficiencies in the thyroid hormone transporter monocarboxylate 8 (MCT8) due to pathogenic variants in the SLC16A2 gene (OMIM 300095) result in a complex phenotype with main endocrine and neurologic symptoms. This rare disorder, named Allan-Herndon-Dudley syndrome (AHDS) (OMIM 300523), is inherited in an X-linked trait. One of the prominent features of AHDS is the presence of movement disorders (MD), which are complex and carry a significant burden of the disease. CASES: Patient 1: male with hypotonia since birth, developmental delay, dystonic posturing at 4 months and at 15 months, and startle reaction developed with sensory stimuli. Patient 2: male, at 2 months, shows hypotonia and developmental delay, paroxysmal episodes triggered by a stimulus with sudden blush, tonic asymmetric posture, and no epileptiform activity. At 10 months, generalized dystonic posturing. Patient 3: typical neurodevelopmental milestones until 6 months; at 24 months, dystonia, startle reaction, and upper motoneuron signs. CONCLUSIONS: We aim to describe our patients diagnosed with AHDS, focusing on MD phenomenology and strengthening the phenotype-genotype correlations for this rare condition.

Impaired polyamine metabolism causes behavioral and neuroanatomical defects in a mouse model of Snyder-Robinson syndrome.

Snyder-Robinson syndrome (SRS) is a rare X-linked recessive disorder caused by a mutation in the SMS gene, which encodes spermine synthase, and aberrant polyamine metabolism. SRS is characterized by intellectual disability, thin habitus, seizure, low muscle tone/hypotonia and osteoporosis. Progress towards understanding and treating SRS requires a model that recapitulates human gene variants and disease presentations. Here, we evaluated molecular and neurological presentations in the G56S mouse model, which carries a missense mutation in the Sms gene. The lack of SMS protein in the G56S mice resulted in increased spermidine/spermine ratio, failure to thrive, short stature and reduced bone density. They showed impaired learning capacity, increased anxiety, reduced mobility and heightened fear responses, accompanied by reduced total and regional brain volumes. Furthermore, impaired mitochondrial oxidative phosphorylation was evident in G56S cerebral cortex, G56S fibroblasts and Sms-null hippocampal cells, indicating that SMS may serve as a future therapeutic target. Collectively, our study establishes the suitability of the G56S mice as a preclinical model for SRS and provides a set of molecular and functional outcome measures that can be used to evaluate therapeutic interventions for SRS.

ClinGen variant curation expert panel recommendations for classification of variants in GAMT, GATM and SLC6A8 for cerebral creatine deficiency syndromes.

Cerebral creatine deficiency syndromes (CCDS) are inherited metabolic phenotypes of creatine synthesis and transport. There are two enzyme deficiencies, guanidinoacetate methyltransferase (GAMT), encoded by GAMT and arginine-glycine amidinotransferase (AGAT), encoded by GATM, which are involved in the synthesis of creatine. After synthesis, creatine is taken up by a sodium-dependent membrane bound creatine transporter (CRTR), encoded by SLC6A8, into all organs. Creatine uptake is very important especially in high energy demanding organs such as the brain, and muscle. To classify the pathogenicity of variants in GAMT, GATM, and SLC6A8, we developed the CCDS Variant Curation Expert Panel (VCEP) in 2018, supported by The Clinical Genome Resource (ClinGen), a National Institutes of Health (NIH)-funded resource. We developed disease-specific variant classification guidelines for GAMT-, GATM-, and SLC6A8-related CCDS, adapted from the American College of Medical Genetics/Association of Molecular Pathology (ACMG/AMP) variant interpretation guidelines. We applied specific variant classification guidelines to 30 pilot variants in each of the three genes that have variants associated with CCDS. Our CCDS VCEP was approved by the ClinGen Sequence Variant Interpretation Working Group (SVI WG) and Clinical Domain Oversight Committee in July 2022. We curated 181 variants including 72 variants in GAMT, 45 variants in GATM, and 64 variants in SLC6A8 and submitted these classifications to ClinVar, a public variant database supported by the National Center for Biotechnology Information. Missense variants were the most common variant type in all three genes. We submitted 32 new variants and reclassified 34 variants with conflicting interpretations. We report specific phenotype (PP4) using a points system based on the urine and plasma guanidinoacetate and creatine levels, brain magnetic resonance spectroscopy (MRS) creatine level, and enzyme activity or creatine uptake in fibroblasts ranging from PP4, PP4_Moderate and PP4_Strong. Our CCDS VCEP is one of the first panels applying disease specific variant classification algorithms for an X-linked disease. The availability of these guidelines and classifications can guide molecular genetics and genomic laboratories and health care providers to assess the molecular diagnosis of individuals with a CCDS phenotype.

SLC6A8 creatine transporter deficiency can be detected by plasma creatine and creatinine concentrations.

Creatine transporter deficiency has been described with normal or uninformative levels of creatine and creatinine in plasma, while urine has been the preferred specimen type for biochemical diagnosis. We report a cohort of untreated patients with creatine transporter deficiency and abnormal plasma creatine panel results, characterized mainly by markedly decreased plasma creatinine. We conclude that plasma should be considered a viable specimen type for the biochemical diagnosis of this disorder, and abnormal results should be followed up with further confirmatory testing.

Genetic analysis of a pedigree with MECP2 duplication syndrome in China.

BACKGROUND: MECP2 duplication syndrome (MDS) is a rare X-linked genomic disorder that primarily affects males. It is characterized by delayed or absent speech development, severe motor and cognitive impairment, and recurrent respiratory infections. MDS is caused by the duplication of a chromosomal region located on chromosome Xq28, which contains the methyl CpG binding protein-2 (MECP2) gene. MECP2 functions as a transcriptional repressor or activator, regulating genes associated with nervous system development. The objective of this study is to provide a clinical description of MDS, including imaging changes observed from the fetal period to the neonatal period. METHODS: Conventional G-banding was employed to analyze the chromosome karyotypes of all pedigrees under investigation. Subsequently, whole exome sequencing (WES), advanced biological information analysis, and pedigree validation were conducted, which were further confirmed by copy number variation sequencing (CNV-seq). RESULTS: Chromosome karyotype analysis revealed that a male patient had a chromosome karyotype of 46,Y,dup(X)(q27.2q28). Whole-exon duplication in the MECP2 gene was revealed through WES results. CNV-seq validation confirmed the presence of Xq27.1q28 duplicates spanning 14.45 Mb, which was inherited from a mild phenotype mother. Neither the father nor the mother's younger brother carried this duplication. CONCLUSION: In this study, we examined a male child in a family who exhibited developmental delay and recurrent respiratory tract infections as the main symptoms. We conducted thorough family investigations and genetic testing to determine the underlying causes of the disease. Our findings will aid in early diagnosis, genetic counseling for male patients in this family, as well as providing prenatal diagnosis and reproductive guidance for female carriers.

Hemizygous splicing variant in CNKSR2 results in X-linked intellectual developmental disorder.

BACKGROUND: Intellectual disability (ID) refers to a childhood-onset neurodevelopmental disorder with a prevalence of approximately 1%-3%. METHODS: We performed whole exome sequencing for the patient with ID. And the splicing variant we found was validated by minigene assay. RESULTS: Here, we report a boy with ID caused by a variant of CNKSR2. His neurological examination revealed hypsarrhythmia via electroencephalography and a right temporal polar arachnoid cyst via brain magnetic resonance imaging. A novel splicing variant in the CNKSR2 gene (NM_014927.5, c.1657+1G>A) was discovered by exome sequencing. The variant caused a 166 bp intron retention between exons 14 and 15, which was validated by a minigene assay. The variant was not reported in public databases such as gnomAD and the Exome Aggregation Consortium. CONCLUSIONS: The variant was predicted to be damaging to correct the translation of the CNKRS2 protein and was classified as likely pathogenic according to the ACMG guidelines.

Insights on the role of thyroid hormone transport in neurosensory organs and implication for the Allan-Herndon-Dudley syndrome.

Thyroid hormones play an important role during the development and functioning of the different sensory systems. In order to exert their actions, thyroid hormones need to access their target cells through transmembrane transporter proteins, among which the monocarboxylate transporter 8 (MCT8) stands out for its pathophysiological relevance. Mutations in the gene encoding for MCT8 lead to the Allan-Herndon-Dudley syndrome (AHDS), a rare disease characterised by severe neuromotor and cognitive impairments. The impact of MCT8 deficiency in the neurosensory capacity of AHDS patients is less clear, with only a few patients displaying visual and auditory impairments. In this review we aim to gather data from different animal models regarding thyroid hormone transport and action in the different neurosensory systems that could aid to identify potential neurosensorial alterations in MCT8-deficient patients.

Development and validation of parent-reported gastrointestinal health scale in MECP2 duplication syndrome.

BACKGROUND/AIMS: We aimed to develop a validated patient-reported Gastrointestinal Health Scale (GHS) specific to MECP2 Duplication Syndrome (MDS) to be used in clinical trials. METHODS: MDS parents completed a Gastrointestinal Health Questionnaire (GHQ) to investigate the most relevant and important items associated with gastrointestinal problems in MECP2-related disorders. Item reduction was executed according to EORTC guidelines. We performed reliability and validity studies for the finalized scale. RESULTS: A total of 106 surveys were eligible for item reduction and validation processes. The initial 55 items were reduced to 38 items based on parent responses, expert opinion, and initial confirmatory factor analysis (CFA). The final MDS-specific GHS included 38 items and 7 factors that underwent further reliability and validity assessments. The power of the study was at least 0.982. The Cronbach's alphas of the instruments were General Health: 0.799, Eating-Chewing-Swallowing: 0.809, Reflux: 0.794, Motility: 0.762, Mood: 0.906, Medication: 0.595, Parenting: 0.942 and all items together: 0.928. The correlation coefficient between total and individual item scores ranged from 0.215 to 0.730. Because of the ordinal nature of the variables, the diagonal weighted least squares estimation (DWLS) method was used to execute the CFA and Structural Equation Modeling. The GHS had excellent model fit with the acceptable range of fit indices values. CONCLUSIONS: We developed a parent-reported, reliable, and valid MDS-specific GHS. This scale can be utilized in clinical settings or as an outcome measure in translational and clinical research.

Late diagnosis of the X-linked MCT8 deficiency (Allan-Herndon-Dudley syndrome) in a teenage girl with primary ovarian insufficiency.

OBJECTIVES: To report an unusual case of MCT8 deficiency (Allan-Herndon-Dudley syndrome), an X-linked condition caused by pathogenic variants in the SLC16A2 gene. Defective transport of thyroid hormones (THs) in this condition leads to severe neurodevelopmental impairment in males, while heterozygous females are usually asymptomatic or have mild TH abnormalities. CASE PRESENTATION: A girl with profound developmental delay, epilepsy, primary amenorrhea, elevated T3, low T4 and free T4 levels was diagnosed with MCT8-deficiency at age 17 years, during evaluation for primary ovarian insufficiency (POI). Cytogenetic analysis demonstrated balanced t(X;16)(q13.2;q12.1) translocation with a breakpoint disrupting SLC16A2. X-chromosome inactivation studies revealed a skewed inactivation of the normal X chromosome. CONCLUSIONS: MCT8-deficiency can manifest clinically and phenotypically in women with SLC16A2 aberrations when nonrandom X inactivation occurs, while lack of X chromosome integrity due to translocation can cause POI.