Severe Speech Delay Research Articles

Rescue of myocytes and locomotion through AAV2/9-2YF intracisternal gene therapy in a rat model of creatine transporter deficiency

Creatine deficiency syndromes (CDS), caused by mutations in GATM (AGAT), GAMT, and SLC6A8, mainly affect the central nervous system (CNS). CDS show brain creatine (Cr) deficiency, intellectual disability with severe speech delay, behavioral troubles, epilepsy, and motor dysfunction. AGAT/GAMT-deficient patients lack brain Cr synthesis but express the Cr transporter SLC6A8 at the blood-brain barrier and are thus treatable by oral supplementation of Cr. In contrast, no satisfactory treatment has been identified for Cr transporter deficiency (CTD), the most frequent of CDS. We used our Slc6a8Y389C CTD rat model to develop a new AAV2/9-2YF-driven gene therapy re-establishing the functional Slc6a8 transporter in rat CNS. We show, after intra-cisterna magna AAV2/9-2YF-Slc6a8-FLAG vector injection of postnatal day 11 pups, the transduction of Slc6a8-FLAG in cerebellum, medulla oblongata, and spinal cord as well as a partial recovery of Cr in these brain regions, together with full prevention of locomotion defaults and impairment of myocyte development observed in Slc6a8Y389 C/y male rats. While more work is needed to correct those CTD phenotypes more associated with forebrain structures, this study is the first demonstrating positive effects of an AAV-driven gene therapy on CTD and thus represents a very encouraging approach to treat the so-far untreatable CTD.

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.

Further evidence supporting the role of GTDC1 in glycine metabolism and neurodevelopmental disorders

Copy number variants (CNVs) represent the genetic cause of about 15–20% of neurodevelopmental disorders (NDDs). We identified a ~67 kb de novo intragenic deletion on chromosome 2q22.3 in a female individual showing a developmental encephalopathy characterised by epilepsy, severe intellectual disability, speech delay, microcephaly, and thin corpus callosum with facial dysmorphisms. The microdeletion involved exons 5-6 of GTDC1, encoding a putative glycosyltransferase, whose expression is particularly enriched in the nervous system. In a previous study, a balanced de novo translocation encompassing GTDC1 was reported in a male child with global developmental delay and delayed speech and language development. Based on these premises, we explored the transcriptomic profile of our proband to evaluate the functional consequences of the novel GTDC1 de novo intragenic deletion in relation to the observed neurodevelopmental phenotype. RNA-seq on the proband’s lymphoblastoid cell line (LCL) showed expression changes of glycine/serine and cytokine/chemokine signalling pathways, which are related to neurodevelopment and epileptogenesis. Subsequent analysis by ELISA (enzyme-linked immunosorbent assay) and HPLC (high-performance liquid chromatography) revealed increased levels of glycine in the proband’s LCL and serum compared to matched controls. Given that an increased level of glycine has been observed in the plasma samples of individuals with Rett syndrome, a condition sharing epilepsy, microcephaly, and intellectual disability with our proband, we proposed that the GTDC1 downregulation is implicated in neurodevelopmental impairment by altering glycine metabolism. Furthermore, our findings expanded the phenotypic spectrum of the novel GTDC1-related condition, including microcephaly and epilepsy among relevant clinical features.

Maternal Wellbeing Five Years after a Very Preterm Delivery: Prevalence and Influencing Factors in a European Cohort.

(1) Background: Mothers of very preterm (VPT) infants may experience psychological symptoms compromising long-term emotional wellbeing. This study describes the emotional wellbeing of mothers of five-year-old children born VPT. We assess the association between sociodemographic, perinatal and neonatal characteristics, and the child's health and development at five years old and maternal emotional wellbeing. (2) Methods: Data are from the prospective European "Effective Perinatal Intensive Care in Europe" (EPICE) and subsequent "Screening for Health In very Preterm infantS in Europe" (SHIPS) projects including births <32 weeks' gestational age in 11 countries in 2011/12. Data were abstracted from obstetric and neonatal records. At five years old, 2605 mothers answered a parental questionnaire including the Mental Health Inventory-5 (MHI-5). Associations between sociodemographic and health characteristics and the mother's MHI-5 score were investigated using multilevel multivariate linear regression analysis with the country modelled as a random effect and inverse probability weighting to correct for attrition bias. (3) Results: The mean MHI-5 score was 71.3 (SD 16.7) out of 100 (highest emotional wellbeing) with a variation among countries from 63.5 (SD 16.8; Poland) to 82.3 (SD 15.8; the Netherlands). MHI-5 scores were significantly lower for mothers whose child had a severe health problem, developmental, or speech delay, for multiparous and single mothers, and when at least one of the parents was unemployed. (4) Conclusions: The emotional wellbeing of mothers of VPT infants differs between European countries. Identifying sociodemographic characteristics and child's health and developmental conditions that affect maternal emotional wellbeing may help to identify groups of mothers who need special assistance to cope with consequences of the delivery of a VPT child.

Behaviours that Challenge in SATB2-associated Syndrome: Correlates of Self-injury, Aggression and Property Destruction

SATB2-associated syndrome (SAS) is a genetic syndrome characterised by intellectual disability, severe speech delay, and palatal and dental problems. Behaviours that challenge (BtC) are reported frequently; however, there is limited research on specific forms of BtC and the correlates of these behaviours. The current study explores correlates of well-defined BtC, self-injury, aggression, and property destruction, in SAS. Eighty-one parents/caregivers of individuals with SAS (53.1% male, Mage 10.12 years) completed questionnaire measures of health, behavioural, emotional, and autism characteristics. Individuals with SAS were grouped based on caregiver responses to the presence or absence of self-injury, aggression, and property destruction on the Challenging Behaviour Questionnaire. Rates of self-injury, aggression and property destruction were 42%, 77% and 49%, respectively. Between-group comparisons were conducted to compare characteristics between behaviour groups. Significantly differing characteristics were entered into separate hierarchical logistic regressions for each form of BtC. Behavioural comparisons indicated variation in the characteristics associated with each behaviour. All hierarchical logistic regression models were significant (p < .001): self-injury (χ2(5) = 38.46, R2 = 0.571), aggression (χ2(4) = 25.12, R2 = 0.414), property destruction (χ2(4) = 23.70, R2 = 0.346), explaining between 34.6% and 57.1% of the variance in behaviour presence. This is the first study to identify correlates of self-injury, aggression, and property destruction in SAS. Variability in the characteristics associated with each behaviour highlights the importance of specificity when examining BtC. Understanding correlates of specific forms of BtC has important implications for informing SAS-associated pathways to behavioural outcomes and the implementation of tailored behavioural interventions.

Autosomal recessive otospondylo-mega-epiphyseal dysplasia: comprehensive clinical review of a pediatric cohort.

Autosomal recessive otospondylo-mega-epiphyseal dysplasia (OSMEDB) is characterized by short stature with short limbs, dysmorphic facial features, and hearing loss, which is caused by biallelic, loss-of-function, variants in the COL11A2 gene. Geno-phenotypic data from the medical records of eight affected individuals from five unrelated families was abstracted, recorded in an Excel spreadsheet and analyzed using simple frequency analysis. Either short femora or short extremities with or without other ultrasonographic abnormalities were demonstrated in five patients antenatally. The mean height was -2.29 SDS. Pectus deformity, including either chest asymmetry or pectus excavatum, was present in five patients. Bilateral hearing loss was verified in all patients. Severe speech delay and learning disabilities were present in two patients whose deafness was realized after the age of 12 months. Four novel loss-of-function variants in COL11A2 were found in this cohort. We present novel geno-phenotypic findings in a pediatric cohort with OSMEDB. The age of manifestation of short stature was variable, ranging from birth to middle childhood, and the severity of short stature varied even within the same family. Hearing loss may not be evident in the neonatal period and manifest later in OSMEDB. Intermittent hearing tests should be performed for early intervention of neurolinguistic delay and learning disabilities.

Quantitative Phenotype Morbidity Description of SATB2-Associated Syndrome

Characterized by developmental delay with severe speech delay, dental anomalies, cleft palate, skeletal abnormalities, and behavioral difficulties, SATB2-associated syndrome (SAS) is caused by pathogenic variants in SATB2. The SAS phenotype range of severity has been documented previously in large series. Using data from the SAS registry, we present the SAS severity score, a comprehensive scoring rubric that encompasses 15 different individual neurodevelopmental and systemic features. Higher (more severe) systemic and total (sum of neurodevelopmental and systemic scores) scores were seen for null variants located after amino acid 350 (the start of the CUT1 domain), the recurrent missense Arg389Cys variant ( n = 10 ), intragenic deletions, and larger chromosomal deletions. The Arg389Cys variant had the highest cognitive, verbal, and sialorrhea severity scores, while large chromosomal deletions had the highest expressive, ambulation, palate, feeding and growth, neurodevelopmental, and total scores. Missense variants not located in the CUT1 or CUT2 domain scored lower in several subcategories. We conclude that the SAS severity score allows quantitative phenotype morbidity description that can be used in routine clinical counseling. Further refinement and validation of the SAS severity score are expected over time. All data from this project can be interactively explored in a new portal.

A novel CACNA1A variant causing Developmental and Epileptic Encephalopathy 42: Report of the first case in Colombia (P3-1.010)

<h3>Objective:</h3> To report a CACNA1A Novel variant causing Developmental and Epileptic Encephalopathy 42. <h3>Background:</h3> CACNA1A encodes the α1A subunit (pore-forming subunit) of a neuronal P/Q type calcium channel. Mutations within this gene lead to clinically significant neurological abnormalities with multiple phenotypic presentations, including Familial Hemiplegic Migraine (FHM), episodic ataxia type 2 (EA2), spinocerebellar ataxia type 6 (SCA6), and Developmental and Epileptic Encephalopathy 42 (DEE42). DEE42 is a disorder characterized by the developmental delay with cognitive impairment and multiple types of seizures in the neonatal period. <h3>Design/Methods:</h3> A karyotype was performed using peripheral blood lymphocytes. A Microarray-based Comparative Genomic Hybridization (aCGH) using CytoScan 750K Array (Affymetrix, Santa Clara, CA, USA) and whole exome sequencing (WES). <h3>Results:</h3> Our patient is a female born to non-consanguineous parents with a family history of speech and psychomotor developmental delay in her mother. She was born at term with uneventful antenatal and perinatal history. At 12 months, she presented to the Neurology and Genetics department with macrocephaly, frontal bossing, severe hypotonia, psychomotor delay, and repeated episodes of seizures requiring therapy with valproic acid and levetiracetam. EEG evidenced generalized spike waves. Her course was complicated by a traumatic brain injury that precipitated repeated episodes of status epilepticus. At 28 months old, she had cognitive and communication deficits with severe speech delay. The aCGH showed a 4q21.21 deletion. The final result was given as 46, XX arr[GRCh37/hg19] chr4:79766081-80327420. In this study, we describe a patient with DEE42 due to a novel mutation in CACNA1A identified using WES. WES revealed a novel heterozygous variant in the CACNA1A gene: c.4174G&gt;A (p.Val1392Met). Parent analysis was negative for the mutation. This novel variant was predicted as a disease-causing mutation. <h3>Conclusions:</h3> These findings widen the mutation and phenotypic spectrum of CACNA1A-associated disease. The potential genotype-phenotype correlation would facilitate early identification and help guide future pharmacologic treatment research. <b>Disclosure:</b> Dr. Orellana Zambrano has nothing to disclose. Dr. Candelo has nothing to disclose. Mrs. Diaz has nothing to disclose. Dr. Pacheco has nothing to disclose. Mr. Giraldo-Ocampo has nothing to disclose. Dr. Gomez-Pineda has nothing to disclose. Dr. Pachajoa has nothing to disclose.

A de novo PAK1 likely pathogenic variant and a de novo terminal 1q microdeletion in a Chinese girl with global developmental delay, severe intellectual disability, and seizures

BackgroundPathogenic PAK1 variants were described to be causative of neurodevelopmental disorder with macrocephaly, seizures, and speech delay. Herein, we present a de novo PAK1 variant combine with a de novo terminal 1q microdeletion in a Chinese pediatric patient, aiming to provide more insights into the underlying genotype–phenotype relationship.MethodsEnrolled in this study was a 6-year-old girl with clinical features of global developmental delay, severe intellectual disability, speech delay, and seizures from Quanzhou region of China. Karyotype and chromosomal microarray analysis (CMA) were performed to detect chromosome abnormalities in this family. Whole exome sequencing (WES) was performed to investigate additional genetic variants in this family.ResultsNo chromosomal abnormalities were elicited from the entire family by karyotype analysis. Further familial CMA results revealed that the patient had a de novo 2.7-Mb microdeletion (arr[GRCh37] 1q44(246,454,321_249,224,684) × 1]) in 1q44 region, which contains 14 OMIM genes, but did not overlap the reported smallest region of overlap (SRO) responsible for the clinical features in 1q43q44 deletion syndrome. In addition, WES result demonstrated a de novo NM_002576: c.251C > G (p.T84R) variant in PAK1 gene in the patient, which was interpreted as a likely pathogenic variant.ConclusionIn this study, we identify a novel PAK1 variant associated with a terminal 1q microdeletion in a patient with neurodevelopmental disorder. In addition, we believe that the main clinical features may ascribe to the pathogenic variant in PAK1 gene in the patient.

Early Diagnostic Signs and the Natural History of Typical Findings in Cohen Syndrome

To describe the clinical presentation and long-term clinical features of a molecularly confirmed cohort with Cohen syndrome. Twelve patients with Cohen syndrome aged 0.2-13.9years from 8 families with a median follow-up of 7years were enrolled to the study. Genetic analyses were made by VPS13B and whole-exome sequencing analyses. Biallelic VPS13B variants, including 3 nonsense, 1 frameshift, and 1 splice-site variant, and a multiexon deletion were detected. Prader-Willi syndrome-like features such as hypotonia, small hands, round face with full cheeks, almond-shaped eyes, and micrognathia were observed in all infantile patients. Beginning from age 4years, it was noticed that the face gradually elongated and became oval. The typical facial features of Cohen syndrome such as a long face, beak-shaped nose, and open-mouth appearance with prominent upper central incisors became evident at age 9. Other Cohen syndrome features including retinopathy (11/11), neutropenia (11/12), truncal obesity (5/12), and myopia (5/11) were detected at the median ages of 7.8, 7, 7.5, and 5years, respectively. Eleven patients aged older than 5years at their last examination had severe speech delay. A differential diagnosis of Cohen syndrome in the infancy should be made with Prader-Willi syndrome, and that the typical facial features for Cohen syndrome is prominent at age 9years, when retinopathy, neutropenia, and truncal obesity become evident. Moreover, adding the severe speech delay to the diagnostic criteria should be considered.

Menke-Hennekam syndrome 1: A Case Report

IntroductionMenke-Hennekam syndrome (MHS) is a relatively new genetic condition characterized by intellectual disabilities, autistic behavior, auditory defects, recurrent upper respiratory tract infections, microcephaly and short stature. Facial characteristics include short palpebral fissures, telecanthus, depressed nasal bridge, short nose, anteverted nares, short columella, and long philtrum. The genetic defect is represented by missense variants of CREBBP gene, located on exons 30 or 31. There are only around 30 cases reported by now.ObjectivesThe aim of the paper is to report a new case of MHS.MethodsThe case is a 3-year-old boy admitted in our department for developmental delay. The clinical examination revealed dysmorphic features; severe speech delay, mild intellectual disability, autistic behaviour.The patient had a personal history of recurrent respiratory infections, visual defect and bilateral sensorineural hearing loss. Other investigations included EEG, abdominal echography, and cerebral MRI all were normal. The genetic studies included array CGH and WES.ResultsThe array CGH was normal. WES identified a pathogenic heterozygote variant c.5600G&gt;A in the exon 31 of CREBBP gene, confirming MHS.ConclusionsOverall, the features of our patient are consistent with those reported in the previous reports, including developmental and speech delay, autistic behavior, dysmorphic features, recurrent upper way infections, sensorineural hearing loss, and visual defects. Other common features, such as growth delay and microcephaly were not present in our patient. Our case contributes to the clinical characterisation of the new syndrome. Funding: The research leading to these results has received funding from the EEA Grant 2014-2021, under the project contract No 6/2019.DisclosureNo significant relationships.

Expanding the mutational spectrum of Rahman syndrome: A rare disorder with severe intellectual disability and particular facial features in two Chinese patients

BackgroundThe study aimed to investigate the clinical and genetic features of Rahman syndrome caused by HIST1H1E gene mutations.MethodsWe retrospectively analyzed the clinical information and genetic testing results of a Rahman syndrome family in an outpatient clinic in August 2020 and summarized the clinical characteristics of the HIST1H1E gene mutations in conjunction with peer‐reviewed reports.ResultsA 4‐year‐old boy was diagnosed with severe developmental delay and with specific features (large head, full cheeks, high hairline, low‐set ear, sparse eyebrows, and short neck) similar to his mother (mild intellectual disability, high hairline, reduced hair, ptosis, sagging skin, and hyperkeratosis) and premature aging. Trio whole exome sequencing (WES) revealed a novel maternal c.368dup (p.G124Rfs*72) heterozygous mutation in the HIST1H1E gene. There have been only a few reported cases with mainly de novo mutations. Only six peer‐reviewed articles in English and one in Chinese have been published regarding this syndrome. From 48 children with Rahman syndrome, 21 were males and 27 were females encompassing 25 mutations in the HIST1H1E gene. All mutations located in C‐terminal tail were frameshift mutations leading to premature protein termination.ConclusionRahman syndrome, caused by the HIST1H1E gene mutation, is a rare autosomal dominant disorder in which the patient has an unusual facial appearance with high hairline and full cheeks, and clinical manifestations of mild to severe intellectual disability, motor delay and speech delay. Genetic testing may assist in the diagnosis of these patients. This diagnosis will permit early speech rehabilitation to improve their quality of life.

Clinical manifestations of Angelman syndrome in children

Angelman syndrome is a genetic disorder characterized by mental retardation and severe speech delay, movement disorders and ataxia, dysmorphic features, and behavioral disorders. Angelman syndrome is caused by the loss of the 15q11.2-q13 region of chromosome 15 received from the mother, which leads to a violation of the expression of the UBE3A gene.Purpose. To analyze clinical manifestations in children with Angelman syndrome to identify early-onset and characteristic clinical signs.Characteristics of children and research methods. The study included 60 children. In all cases, Angelman syndrome was diagnosed on the basis of international clinical criteria and the results of genetic testing. The researchers used clinical, functional and molecular genetic research methods.Results. 80-100% of children demonstrated delayed mental and motor development, lack of speech, affective behavior, ataxia, hand stereotypes, apraxia of hand movements, strabismus, sialorrhea. 72% of children had epileptic seizures; all patients (regardless of the presence / absence of epilepsy) had a pattern characteristic of Angelman syndrome on the electroencephalogram. Differential diagnosis was based on the gene / chromosomal syndromes characterized by similar clinical signs.Conclusion. The combination of such most frequent, early clinical symptoms as difficulties in feeding, strabismus, impaired muscle tone, delayed motor and psycho-speech development, affective behavior with frequent laughter, and sleep disorders may indicate Angelman syndrome in a child.

Creatine transporter-deficient rat model shows motor dysfunction, cerebellar alterations, and muscle creatine deficiency without muscle atrophy.

Creatine (Cr) is a nitrogenous organic acid and plays roles such as fast phosphate energy buffer to replenish ATP, osmolyte, antioxidant, neuromodulator, and as a compound with anabolic and ergogenic properties in muscle. Cr is taken from the diet or endogenously synthetized by the enzymes arginine:glycine amidinotransferase and guanidinoacetate methyltransferase, and specifically taken up by the transporter SLC6A8. Loss‐of‐function mutations in the genes encoding for the enzymes or the transporter cause creatine deficiency syndromes (CDS). CDS are characterized by brain Cr deficiency, intellectual disability with severe speech delay, behavioral troubles, epilepsy, and motor dysfunction. Among CDS, the X‐linked Cr transporter deficiency (CTD) is the most prevalent with no efficient treatment so far. Different animal models of CTD show reduced brain Cr levels, cognitive deficiencies, and together they cover other traits similar to those of patients. However, motor function was poorly explored in CTD models, and some controversies in the phenotype exist in comparison with CTD patients. Our recently described Slc6a8 Y389C knock‐in rat model of CTD showed mild impaired motor function, morphological alterations in cerebellum, reduced muscular mass, Cr deficiency, and increased guanidinoacetate content in muscle, although no consistent signs of muscle atrophy. Our results indicate that such motor dysfunction co‐occurred with both nervous and muscle dysfunctions, suggesting that muscle strength and performance as well as neuronal connectivity might be affected by this Cr deficiency in muscle and brain.

A Novel 4q32.3 Deletion in a Child: Additional Signs and the Role of MARCH1.

The 4q deletion syndrome is an uncommon condition manifesting with broad clinical expression and phenotypic variability. We report a 5-year-old boy affected by 4q deletion syndrome who showed minor craniofacial features, growth failure, mild developmental delay, severe speech delay, and marked irascibility and aggressivity. Moreover, he showed precocious and crowded primary dentition, digital hyperlaxity, and congenital bilateral adducted thumbs, signs which were previously unreported in the syndrome. The array comparative genomic hybridization analysis revealed a 4q partial terminal deletion of ∼329.6 kb extending from 164.703.186 to 165.032.803 nt, which includes part of MARCH1 (membrane associated ring-CH-type finger 1) gene (OMIM#613331). Same rearrangement was found in his healthy mother. Clinical phenotype of the child and its relationship to the deleted region is presented with a revision of the cases having the same copy number losses from the literature and genomic variant databases.

Chromosome 2q14.3 microdeletion encompassing CNTNAP5 gene in a patient carrying a complex chromosomal rearrangement

We report a patient with loss of chromosome region 2q14.3 encompassing exon 1 of the gene CNTNAP5. The deletion occurred in association with a de novo complex chromosomal rearrangement, characterized by routine G-banding, fluorescence in situ hybridization and microarray analysis. The presented patient's phenotype is dominated by severe early childhood weight gain, severe speech delay and behavioural problems. To our knowledge, a few similar patients have been reported previously. CNTNAP5 is a member of the neurexin gene family and is associated with autism spectrum disorder and potentially other behavioural and neurodevelopmental disorders. Recent data point to its possible role in obesity and/or metabolism. The phenotype of the herein presented pediatric patient corroborates CNTNAP5's pathogenic role in human disease.

Identification of two novel homozygous mutations in ERCC8 gene in two unrelated consanguineous families with Cockayne syndrome from Iran

BackgroundCockayne syndrome (CS) is a rare autosomal recessive disorder with characteristic multisystem involvement including pre- or post-natal growth failure, progressive neurological dysfunction, psychomotor retardation, cerebral atrophy, microcephaly and mental retardation, due to mutations in either the ERCC8/CSA or ERCC6/CSB gene. MethodWe present two Iranian patients with remarkable growth failure, developmental delay, microcephaly, severe speech delay, vision problem, sun sensitivity, hearing loss, dental anomalies, unstable gait, mild contractures in knees, kyphosis and spasticity in lower limbs, balance disorders and typical dysmorphic features including long nose, aged face, large ears and sunken eyes.Clinical evaluation, magnetic resonance imaging, Peripheral blood karyotype, Multiplex ligation-dependent probe amplification (MLPA), and whole-exome sequencing were used to characterize etiology in two patients from two unrelated consanguineous families of Iranian descent with Cockayne syndrome. ResultsWe detected two novel pathogenic mutations in two unrelated families, a homozygous duplication mutation (c.317_320dupAGTG, p.Trp107Ter) and a splicing variant (c.481 + 1G > A) in ERCC8 gene. ConclusionWES results together with the characteristic clinical manifestations of Cockayne syndrome, provided an accurate diagnosis for two patients. Also, our study identified two novel variants in Iranian families.

Impaired glucose-1,6-biphosphate production due to bi-allelic PGM2L1 mutations is associated with a neurodevelopmental disorder

SummaryWe describe a genetic syndrome due to PGM2L1 deficiency. PGM2 and PGM2L1 make hexose-bisphosphates, like glucose-1,6-bisphosphate, which are indispensable cofactors for sugar phosphomutases. These enzymes form the hexose-1-phosphates crucial for NDP-sugars synthesis and ensuing glycosylation reactions. While PGM2 has a wide tissue distribution, PGM2L1 is highly expressed in the brain, accounting for the elevated concentrations of glucose-1,6-bisphosphate found there. Four individuals (three females and one male aged between 2 and 7.5 years) with bi-allelic inactivating mutations of PGM2L1 were identified by exome sequencing. All four had severe developmental and speech delay, dysmorphic facial features, ear anomalies, high arched palate, strabismus, hypotonia, and keratosis pilaris. Early obesity and seizures were present in three individuals. Analysis of the children’s fibroblasts showed that glucose-1,6-bisphosphate and other sugar bisphosphates were markedly reduced but still present at concentrations able to stimulate phosphomutases maximally. Hence, the concentrations of NDP-sugars and glycosylation of the heavily glycosylated protein LAMP2 were normal. Consistent with this, serum transferrin was normally glycosylated in affected individuals. PGM2L1 deficiency does not appear to be a glycosylation defect, but the clinical features observed in this neurodevelopmental disorder point toward an important but still unknown role of glucose-1,6-bisphosphate or other sugar bisphosphates in brain metabolism.

A novel MYT1L mutation in a boy with syndromic obesity: Case report and literature review

BackgroundPathogenic variants involving the MYT1L gene lead to an autosomal dominant form of syndromic obesity, characterized by polyphagia, intellectual disability/developmental delay, and behavioral problems, and that a characteristic facial phenotype does not seem to be recognizable. MethodsTrio whole exome sequencing was performed in a 10-year-old Brazilian male presenting polyphagia, severe early-onset obesity, intellectual disability, speech delay, macrocephaly, frontal bossing, telecanthus, strabismus, and hypogenitalism. Additionally, we performed a literature review of patients carrying non-copy number MYT1L variants. ResultsA de novo genetic variant not previously reported in MYT1L (NM_015025.4:c.2990C>A) was identified in the proband and classified as pathogenic. From a literature search, 22 further patients carrying non-copy number MYT1L variants were identified, evidencing that although the associated phenotype is quite variable, intellectual disability/developmental and speech delays are always present. Further, most patients have obesity or overweight due to polyphagia. Macrocephaly, strabismus, behavioral problems, and hand/feet malformations are also recurrent features. ConclusionsWe described the first Brazilian case of MYT1L related syndrome and highlighted clinical characteristics based on the literature. Other syndromic forms of obesity such as Prader-Willi, Bardet-Biedl, Börjeson-Forssman-Lehmann, MORM, Cohen, Alstrom, and Kleefstra type 1 syndromes should be considered in the differential diagnosis. Further, although obesity is frequent, it is not an obligatory feature of all carriers of MYT1L mutations.

A new rat model of creatine transporter deficiency reveals behavioral disorder and altered brain metabolism

Creatine is an organic compound used as fast phosphate energy buffer to recycle ATP, important in tissues with high energy demand such as muscle or brain. Creatine is taken from the diet or endogenously synthetized by the enzymes AGAT and GAMT, and specifically taken up by the transporter SLC6A8. Deficit in the endogenous synthesis or in the transport leads to Cerebral Creatine Deficiency Syndromes (CCDS). CCDS are characterized by brain creatine deficiency, intellectual disability with severe speech delay, behavioral troubles such as attention deficits and/or autistic features, and epilepsy. Among CCDS, the X-linked creatine transporter deficiency (CTD) is the most prevalent with no efficient treatment so far. Different mouse models of CTD were generated by doing long deletions in the Slc6a8 gene showing reduced brain creatine and cognitive deficiencies or impaired motor function. We present a new knock-in (KI) rat model of CTD holding an identical point mutation found in patients with reported lack of transporter activity. KI males showed brain creatine deficiency, increased urinary creatine/creatinine ratio, cognitive deficits and autistic-like traits. The Slc6a8Y389C KI rat fairly enriches the spectrum of CTD models and provides new data about the pathology, being the first animal model of CTD carrying a point mutation.