Exploring the characteristics and most bothersome symptoms in MECP2 duplication syndrome to pave the path toward developing parent-oriented outcome measures.

BACKGROUND: MECP2 Duplication Syndrome (MDS), resulting from the duplication of Xq28 region, including MECP2, is a rare disorder with a nascent understanding in clinical features and severity. Studies using antisense oligonucleotides revealed a broad phenotypic rescue in transgenic mice. With human clinical trials on the horizon, there is a need to develop clinical outcome measures for MDS. METHODS: We surveyed caregivers of MDS individuals to explore the frequency and severity of MDS clinical features, and identify the most meaningful symptoms/domains that need to be included in the outcome measure scales. RESULTS: A total of 101 responses were eligible for the survey. The top six most meaningful symptoms to caregivers in descending order included epilepsy, gross motor, fine motor, communication, infection, and constipation problems. Epilepsy was present in 58.4% of the subjects and 75% were drug-resistant, Furthermore, ~12% required intensive care unit (ICU) admission. Infections were present in 55% of the subjects, and one-fourth of them required ICU admission. Constipation was present in ~85% of the subjects and one-third required enemas/suppositories. CONCLUSION: Our study is one of the largest cohorts conducted on MDS individuals characterizing the frequency and severity of MDS symptoms. Additionally, these study results will contribute to establishing a foundation to develop parent-reported outcomes in MDS.

Cerebral creatine deficiency disorders - A clinical, genetic and follow up study from India.

INTRODUCTION: Cerebral creatine deficiency syndromes (CCDS) are a group of potentially treatable neurometabolic disorders. The clinical, genetic profile and follow up outcome of Indian CCDS patients is presented. MATERIALS AND METHODS: This was a retrospective cohort of CCDS patients seen over six-years. Diagnosis was based either on low creatine peak on proton magnetic resonance spectroscopy (MRS) and/or genetic evaluation. RESULTS: Thirteen patients were eligible [8 creatine transporter deficiency (CTD), 4 guanidinoacetate methyltransferase (GAMT) deficiency and 1 could not be classified]. The mean (±SD) age at diagnosis was 7.2(±5.0) years. Clinical manifestations included intellectual disability (ID) with significant expressive speech delay in all. Most had significant behavior issues (8/13) and/or autism (8/13). All had history of convulsive seizures (11/13 had epilepsy; 2 patients only had febrile seizures) and 2/13 had movement disorder. Constipation was the commonest non-neurological manifestation (5/13 patients). Cranial MRI was normal in all CTD patients but showed globus pallidus hyperintensity in all four with GAMT deficiency. MRS performed in 11/13 patients, revealed abnormally low creatine peak. A causative genetic variant (novel mutation in nine) was identified in 12 patients. Three GAMT deficiency and one CTD patient reported neurodevelopmental improvement and good seizure control after creatine supplementation. CONCLUSION: Intellectual disability, disproportionate speech delay, autism, and epilepsy, were common in our CCDS patients. A normal structural neuroimaging with easily controlled febrile and/or afebrile seizures differentiated CTD from GAMT deficiency patients who had abnormal neuroimaging and often difficult to control epilepsy and movement disorder.

Electroclinical Features in MECP2 Duplication Syndrome: Pediatric Case Series.

OBJECTIVE: MECP2 duplication syndrome (MECP2DS) is an x-linked recessive syndrome characterized by infantile hypotonia, severe neurodevelopmental delay, intellectual disability, progressive spasticity, recurrent infections, and seizures. More than 50% of cases have been associated with epilepsy. Seizure semiology and electroencephalogram (EEG) findings in these patients are poorly described. METHODS: In this case series, the authors describe the electroclinical features of children with MECP2DS presenting to their institution. In addition, they reviewed seizure types and therapies used. RESULTS: Eight out of 9 patients with MECP2DS developed epilepsy, with 56% having normal initial EEG. Generalized slowing with generalized and focal/multifocal discharges was the most common EEG pattern which is consistent with prior studies. Atonic seizure was the most common semiology. Majority were pharmacoresistant (63%). CONCLUSION: The goal of this case series is to better define the clinical and electrophysiological aspects of the epilepsy associated with MECP2 duplication syndrome and provide practical guidance regarding management.

ATR-X syndrome: genetics, clinical spectrum, and management.

ATR-X, an acronym for alpha thalassemia and mental retardation X-linked, syndrome is a congenital condition predominantly affecting males, characterized by mild to severe intellectual disability, facial, skeletal, urogenital, and hematopoietic anomalies. Less common are heart defects, eye anomalies, renal abnormalities, and gastrointestinal dysfunction. ATR-X syndrome is caused by germline variants in the ATRX gene. Until recently, the diagnosis of the ATR-X syndrome had been guided by the classical clinical manifestations and confirmed by molecular techniques. However, our new systematic analysis shows that the only clinical sign shared by all affected individuals is intellectual disability, with the other manifestations varying even within the same family. More than 190 different germline ATRX mutations in some 200 patients have been analyzed. With improved and more frequent analysis by molecular technologies, more subtle deletions and insertions have been detected recently. Moreover, emerging technologies reveal non-classic phenotypes of ATR-X syndrome as well as the description of a new clinical feature, the development of osteosarcoma which suggests an increased cancer risk in ATR-X syndrome. This review will focus on the different types of inherited ATRX mutations and their relation to clinical features in the ATR-X syndrome. We will provide an update of the frequency of clinical manifestations, the affected organs, and the genotype-phenotype correlations. Finally, we propose a shift in the diagnosis of ATR-X patients, from a clinical diagnosis to a molecular-based approach. This may assist clinicians in patient management, risk assessment and genetic counseling.

Transgenic mice with an R342X mutation in Phf6 display clinical features of Börjeson-Forssman-Lehmann Syndrome.

The PHF6 mutation c.1024C > T; p.R342X, is a recurrent cause of Börjeson-Forssman-Lehmann Syndrome (BFLS), a neurodevelopmental disorder characterized by moderate-severe intellectual disability, truncal obesity, gynecomastia, hypogonadism, long tapering fingers and large ears (MIM#301900). Here, we generated transgenic mice with the identical substitution (R342X mice) using CRISPR technology. We show that the p.R342X mutation causes a reduction in PHF6 protein levels, in both human and mice, from nonsense-mediated decay and nonsense-associated alternative splicing, respectively. Magnetic resonance imaging studies indicated that R342X mice had a reduced brain volume on a mixed genetic background but developed hydrocephaly and a high incidence of postnatal death on a C57BL/6 background. Cortical development proceeded normally, while hippocampus and hypothalamus relative brain volumes were altered. A hypoplastic anterior pituitary was also observed that likely contributes to the small size of the R342X mice. Behavior testing demonstrated deficits in associative learning, spatial memory and an anxiolytic phenotype. Taken together, the R342X mice represent a good preclinical model of BFLS that will allow further dissection of PHF6 function and disease pathogenesis.

Immunodeficiency in a patient with microcephalic osteodysplastic primordial dwarfism type I as compared to Roifman syndrome.

BACKGROUND: Microcephalic osteodysplastic primordial dwarfism type I (MOPD I, also known as Taybi-Linder syndrome) is a rare genetic disorder associated with severe intrauterine growth retardation, short stature, microcephaly, brain anomalies, stunted limbs, and early mortality. RNU4ATAC, the gene responsible for this disorder, does not encode a protein but instead the U4atac small nuclear RNA (snRNA), a crucial component of the minor spliceosome. Roifman syndrome is an allelic disorder of MOPD I that is characterized by immunodeficiency complications. CASE REPORT: The patient described herein is an 18-year-old woman exhibiting congenital dwarfism and microcephaly with structural brain anomaly. She suffered human herpesvirus 6 (HHV-6)-associated acute necrotizing encephalopathy at the age of one, thereafter resulting in severe psychomotor disabilities. Genetic analysis using gene microarray and whole-exome sequencing could not identify the cause of her congenital anomalies. However, Sanger sequencing revealed a compound heterozygous mutation within RNU4ATAC (NR_023343.1:n.[50G > A];[55G > A]). Immunological findings showed decreases in total lymphocytes, CD4+ T cells, and T cell regenerative activity. Furthermore, antibodies against varicella-zoster, rubella, measles, mumps, and influenza were very low or negative despite having received vaccinations for these viruses. HHV-6 IgG antibodies were also undetected. DISCUSSION: The patient here exhibited a marked MOPD I phenotype complicated by various immunodeficiencies. Previous studies have not demonstrated immunodeficiency comorbidities within MOPD I subjects, but this report suggests an evident immunodeficiency in MOPD I. Patients with MOPD I should be treated with one of the immunodeficiency syndromes.

Brain Gene Expression in Systemic Hypothyroidism and Mouse Models of MCT8 Deficiency: The Mct8-Oatp1c1-Dio2 Triad.

Background: The monocarboxylate transporter 8 (Mct8) protein is a primary thyroxine (T4) and triiodothyronine (T3) (thyroid hormone [TH]) transporter. Mutations of the MCT8-encoding, SLC16A2 gene alter thyroid function and TH metabolism and severely impair neurodevelopment (Allan-Herndon-Dudley syndrome [AHDS]). Mct8-deficient mice manifest thyroid alterations but lack neurological signs. It is believed that Mct8 deficiency in mice is compensated by T4 transport through the Slco1c1-encoded organic anion transporter polypeptide 1c1 (Oatp1c1). This allows local brain generation of sufficient T3 by the Dio2-encoded type 2 deiodinase, thus preventing brain hypothyroidism. The Slc16a2/Slco1c1 (MO) and Slc16a2/Dio2 (MD) double knockout (KO) mice lacking T4 and T3 transport, or T3 transport and T4 deiodination, respectively, should be appropriate models of AHDS. Our goal was to compare the cerebral hypothyroidism of systemic hypothyroidism (SH) caused by thyroid gland blockade with that present in the double KO mice. Methods: We performed RNA sequencing by using RNA from the cerebral cortex and striatum of SH mice and the double KO mice on postnatal days 21-23. Real-time polymerase chain reaction was used to confirm RNA-Seq results in replicate biological samples. Cell type involvement was assessed from cell type-enriched genes. Functional genomic differences were analyzed by functional node activity based on a probabilistic graphical model. Results: Each of the three conditions gave a different pattern of gene expression, with partial overlaps. SH gave a wider and highest variation of gene expression than MD or MO. This was partially due to secondary gene responses to hypothyroidism. The set of primary transcriptional T3 targets showed a tighter overlap, but quantitative gene responses indicated that the gene responses in SH were more severe than in MD or MO. Examination of cell type-enriched genes indicated cellular differences between the three conditions. Conclusions: The results indicate that the neurological impairment of AHDS is too severe to be fully explained by TH deprivation only.

Prenatal Treatment of Thyroid Hormone Cell Membrane Transport Defect Caused by MCT8 Gene Mutation.

Background: Mutations of the thyroid hormone (TH)-specific cell membrane transporter, monocarboxylate transporter 8 (MCT8), produce an X-chromosome-linked syndrome of TH deficiency in the brain and excess in peripheral tissues. The clinical consequences include brain hypothyroidism causing severe psychoneuromotor abnormalities (no speech, truncal hypotonia, and spastic quadriplegia) and hypermetabolism (poor weight gain, tachycardia, and increased metabolism, associated with high serum levels of the active TH, T3). Treatment in infancy and childhood with TH analogues that reduce serum triiodothyronine (T3) corrects hypermetabolism, but has no effect on the psychoneuromotor deficits. Studies of brain from a 30-week-old MCT8-deficient embryo indicated that brain abnormalities were already present during fetal life. Methods: A carrier woman with an affected male child (MCT8 A252fs268*), pregnant with a second affected male embryo, elected to carry the pregnancy to term. We treated the fetus with weekly 500 µg intra-amniotic instillation of levothyroxine (LT4) from 18 weeks of gestation until birth at 35 weeks. Thyroxine (T4), T3, and thyrotropin (TSH) were measured in the amniotic fluid and maternal serum. Treatment after birth was continued with LT4 and propylthiouracil. Follow-up included brain magnetic resonance imaging (MRI) and neurodevelopmental evaluation, both compared with the untreated brother. Results: During intrauterine life, T4 and T3 in the amniotic fluid were maintained above threefold to twofold the baseline and TSH was suppressed by 80%, while maternal serum levels remained unchanged. At birth, the infant serum T4 was 14.5 µg/dL and TSH <0.01 mU/L compared with the average in untreated MCT8-deficient infants of 5.1 µg/ and >8 mU/L, respectively. MRI at six months of age showed near-normal brain myelination compared with much reduced in the untreated brother. Neurodevelopmental assessment showed developmental quotients in receptive language and problem-solving, and gross motor and fine motor function ranged from 12 to 25 at 31 months in the treated boy and from 1 to 7 at 58 months in the untreated brother. Conclusions: This is the first demonstration that prenatal treatment improved the neuromotor and neurocognitive function in MCT8 deficiency. Earlier treatment with TH analogues that concentrate in the fetus when given to the mother may further rescue the phenotype.

The First Korean Case of Baraitser-Winter Cerebro-Fronto-Facial Syndrome with a Novel Mutation in ACTB Diagnosed Via Targeted Gene Panel Sequencing and Literature Review.

Baraitser-Winter Cerebro-fronto-facial syndrome (BWCFF, OMIM #243310, #614583) is caused by a heterozygous gain-of-function mutation of ACTB and ACTG1 that encodes actin. The syndrome is characterized by striking facial features, structural brain abnormalities, ocular coloboma, hearing loss, cardiac defects, intellectual disabilities, short stature, and developmental delay. We report a two-year-old girl who had distinctive facial features, including hypertelorism, arched eyebrows, bilateral ptosis, short broad nose with a flat nasal tip, long philtrum, retrognathia, low-set ears, and a thin upper lip. In addition, she also exhibited short stature, pectus excavatum, developmental delay, brain malformation, and hearing loss. Targeted gene panel sequencing identified a de novo heterozygous missense variant c.826G>A (p.Glu276Lys) in ACTB This is the first Korean case of BWCFF with a novel mutation in ACTB.

Comparison of Core Features in Four Developmental Encephalopathies in the Rett Natural History Study.

OBJECTIVE: Rett syndrome, CDKL5-deficiency disorder, FOXG1 disorder, and MECP2 duplication disorder are developmental encephalopathies with shared and distinct features. Although they are historically linked, no direct comparison has been performed. The first head-to-head comparison of clinical features in these conditions is presented. METHODS: Comprehensive clinical information was collected from 793 individuals enrolled in the Rett and Rett-Related Disorders Natural History Study. Clinical features including clinical severity, regression, and seizures were cross-sectionally compared between diagnoses to test the hypothesis that these are 4 distinct disorders. RESULTS: Distinct patterns of clinical severity, seizure onset age, and regression were present. Individuals with CDKL5-deficency disorder were the most severely affected and had the youngest age at seizure onset (2 months), whereas children with MECP2 duplication syndrome had the oldest median age at seizure onset (64 months) and lowest severity scores. Rett syndrome and FOGX1 were intermediate in both features. Smaller head circumference correlates with increased severity in all disorders and earlier age at seizure onset in MECP2 duplication syndrome. Developmental regression occurred in all Rett syndrome participants (median = 18 months) but only 23 to 34% of the other disorders. Seizure incidence prior to the baseline visit was highest for CDKL5 deficiency disorder (96.2%) and lowest for Rett syndrome (47.5%). Other clinical features including seizure types and frequency differed among groups. INTERPRETATION: Although these developmental encephalopathies share many clinical features, clear differences in severity, regression, and seizures warrant considering them as unique disorders. These results will aid in the development of disease-specific severity scales, precise therapeutics, and future clinical trials. ANN NEUROL 2020;88:396-406.

Allan-Herndon-Dudley-Syndrome: Considerations about the Brain Phenotype with Implications for Treatment Strategies.

Despite its first description more than 75 years ago, effective treatment for "Allan-Herndon-Dudley-Syndrome (AHDS)", an X-linked thyroid hormone transporter defect, is unavailable. Mutations in the SLC16A2 gene have been discovered to be causative for AHDS in 2004, but a comprehensive understanding of the function of the encoded protein, monocarboxylate transporter 8 (MCT8), is incomplete. Patients with AHDS suffer from neurodevelopmental delay, as well as extrapyramidal (dystonia, chorea, athetosis), pyramidal (spasticity), and cerebellar symptoms (ataxia). This suggests an affection of the pyramidal tracts, basal ganglia, and cerebellum, most likely already during fetal brain development. The function of other brain areas relevant for mood, behavior, and vigilance seems to be intact. An optimal treatment strategy should thus aim to deliver T3 to these relevant structures at the correct time points during development. A potential therapeutic strategy meeting these needs might be the delivery of T3 via a "Trojan horse mechanism" by which T3 is delivered into target cells by a thyroid hormone transporter independent T3 internalization.

MED12 missense mutation in a three-generation family. Clinical characterization of MED12-related disorders and literature review.

Mutations in MED12 gene have been described in association with syndromic and non-syndromic X-linked intellectual disability (XLID). Up to date at least three distinct XLID syndromes have been described: FG syndrome, Lujan-Fryns syndrome (LS) and Ohdo syndrome (OSMKB). In the last years, thanks to the massive use of next generation sequencing techniques (NGS) it has been possible to discover at least 16 others MED12 mutations and to expand the phenotype of MED12-related disorders. Here we report three subjects from a large non-consanguineous family presenting with a mild to severe ID, important speech delay, behavior problems, dysmorphic facial features and hearing loss. NGS allows us to detect the MED12 missense variant c.3883C > T (p.(Arg1295Cys)) carried by the three patients. This variant has been reported in 2016 by Hu et al. in one family from a big cohort of XLID families. This clinical report contributes to expanding the phenotype associated with MED12-mutations.

Deletion of the Creatine Transporter (Slc6a8) in Dopaminergic Neurons Leads to Hyperactivity in Mice.

The lack of cerebral creatine (Cr) causes intellectual disability and epilepsy. In addition, a significant portion of individuals with Cr transporter (Crt) deficiency (CTD), the leading cause of cerebral Cr deficiency syndromes (CCDS), are diagnosed with attention-deficit hyperactivity disorder. While the neurological effects of CTD are clear, the mechanisms that underlie these deficits are unknown. Part of this is due to the heterogenous nature of the brain and the unique metabolic demands of specific neuronal systems. Of particular interest related to Cr physiology are dopaminergic neurons, as many CCDS patients have ADHD and Cr has been implicated in dopamine-associated neurodegenerative disorders, such as Parkinson's and Huntington's diseases. The purpose of this study was to examine the effect of a loss of the Slc6a8 (Crt) gene in dopamine transporter (Slc6a3; DAT) expressing cells on locomotor activity and motor function as the mice age. Floxed Slc6a8 (Slc6a8flox) mice were mated to DATIREScre expressing mice to generate DAT-specific Slc6a8 knockouts (dCrt-/y). Locomotor activity, spontaneous activity, and performance in the challenging beam test were evaluated monthly in dCrt-/y and control (Slc6a8flox) mice from 3 to 12 months of age. dCrt-/y mice were hyperactive compared with controls throughout testing. In addition, dCrt-/y mice showed increased rearing and hindlimb steps in the spontaneous activity test. Latency to cross the narrow bridge was increased in dCrt-/y mice while foot slips were unchanged. Taken together, these data suggest that the lack of Cr in dopaminergic neurons causes hyperactivity while sparing motor function.

Bain type of X-linked syndromic mental retardation in a male with a pathogenic variant in HNRNPH2.

Heterogeneous nuclear ribonucleoproteins (hnRNPs) are RNA binding proteins, which aid in maturation, stabilization, and transport of mRNA. They have a significant role in cellular nucleic acid metabolism. The hnRNPs alter gene expression and are linked to various neurodegenerative disorders and cancers. Previously, six unrelated girls with developmental delay, intellectual disability, and hypotonia were found to have de novo heterozygous pathogenic missense variants in HNRNPH2, located on the X chromosome. A gain-of-function effect was proposed for the variant and it was thought to be lethal in males as no surviving males were identified. We describe a family with two affected siblings, one male and one female, with a known pathogenic variant in HNRNPH2, possibly due to maternal germline mosaicism.

Thyroid Hormone Transporters.

Thyroid hormone transporters at the plasma membrane govern intracellular bioavailability of thyroid hormone. Monocarboxylate transporter (MCT) 8 and MCT10, organic anion transporting polypeptide (OATP) 1C1, and SLC17A4 are currently known as transporters displaying the highest specificity toward thyroid hormones. Structure-function studies using homology modeling and mutational screens have led to better understanding of the molecular basis of thyroid hormone transport. Mutations in MCT8 and in OATP1C1 have been associated with clinical disorders. Different animal models have provided insight into the functional role of thyroid hormone transporters, in particular MCT8. Different treatment strategies for MCT8 deficiency have been explored, of which thyroid hormone analogue therapy is currently applied in patients. Future studies may reveal the identity of as-yet-undiscovered thyroid hormone transporters. Complementary studies employing animal and human models will provide further insight into the role of transporters in health and disease. (Endocrine Reviews 41: 1 - 55, 2020).

Alu-mediated Xq24 deletion encompassing CUL4B, LAMP2, ATP1B4, TMEM255A, and ZBTB33 genes causes Danon disease in a female patient.

Cullin 4B (CUL4B), lysosomal-associated membrane protein Type 2 (LAMP2), ATP1B4, TMEM255A, and ZBTB33 are neighboring genes on Xq24. Mutations in CUL4B result in Cabezas syndrome (CS). Male CS patients present with dysmorphic, neuropsychiatric, genitourinary, and endocrine abnormalities. Heterozygous CS females are clinically asymptomatic. LAMP2 mutations cause Danon disease (DD). Cardiomyopathy is a dominant feature of DD present in both males and heterozygous females. No monogenic phenotypes have been associated with mutations in ATP1B4, TMEM255A, and ZBTB33 genes. To facilitate diagnostics and counseling in CS and DD families, we present a female DD patient with a de novo Alu-mediated Xq24 rearrangement causing a deletion encompassing CUL4B, LAMP2, and also the other three neighboring genes. Typical to females heterozygous for CUL4B mutations, the patient was CS asymptomatic, however, presented with extremely skewed X-chromosome inactivation (XCI) ratios in peripheral white blood cells. As a result of the likely selection against CUL4B deficient clones, only minimal populations (~3%) of LAMP2 deficient leukocytes were identified by flow cytometry. On the contrary, myocardial LAMP2 protein expression suggested random XCI. We demonstrate that contiguous CUL4B and LAMP2 loss-of-function copy number variations occur and speculate that male patients carrying similar defects could present with features of both CS and DD.

[MECP2 mutation in a male patient identified in the background of severe epileptic encephalopathy]. / Súlyos epilepsziás encephalopathia hátterében azonosított MECP2-gén-mutáció fiúbetegben.

Here we report on a severe, neonatal onset epileptic encephalopathy manifested in a currently 2-year-old boy with no family history of neurological disease. Extensive clinical investigations were unable to clarify the etiology of the infant's condition characterized by drug-resistant seizures and markedly delayed developmental skills. As in this class of disorders a genetic cause might be identified, a next-generation sequencing (NGS) epilepsy panel examination consisting of 128 genes was initiated for a correct diagnosis. The genetic analysis identified a previously undescribed hemizygous missense mutation in the MECP2 gene. Similarly to other, X-linked dominant disorders, Rett syndrome was originally hypothesized to be lethal in males. This theory, however, has been revised. The aim of this report is to review the wide spectrum of neurodevelopmental diseases observed in male patients carrying mutations in the MECP2 gene classically associated with Rett syndrome in girls. To the author's knowledge, this is the first report in Hungary to document MECP2 mutation of a male patient diagnosed by molecular genetic testing. Orv Hetil. 2019; 160(51): 2036-2039.