Baker, Gordon et al. present the first international case series describing the neurodevelopmental disorder associated with Synaptotagmin 1 (SYT1) de novo missense mutations. Key features include ...movement abnormalities, severe intellectual disability, and hallmark EEG alterations. Expression of patients' SYT1 mutations in mouse neurons disturbs presynaptic vesicle dynamics in a mutation-specific manner.
Abstract
Synaptotagmin 1 (SYT1) is a critical mediator of fast, synchronous, calcium-dependent neurotransmitter release and also modulates synaptic vesicle endocytosis. This paper describes 11 patients with de novo heterozygous missense mutations in SYT1. All mutations alter highly conserved residues, and cluster in two regions of the SYT1 C2B domain at positions Met303 (M303K), Asp304 (D304G), Asp366 (D366E), Ile368 (I368T) and Asn371 (N371K). Phenotypic features include infantile hypotonia, congenital ophthalmic abnormalities, childhood-onset hyperkinetic movement disorders, motor stereotypies, and developmental delay varying in severity from moderate to profound. Behavioural characteristics include sleep disturbance and episodic agitation. Absence of epileptic seizures and normal orbitofrontal head circumference are important negative features. Structural MRI is unremarkable but EEG disturbance is universal, characterized by intermittent low frequency high amplitude oscillations. The functional impact of these five de novo SYT1 mutations has been assessed by expressing rat SYT1 protein containing the equivalent human variants in wild-type mouse primary hippocampal cultures. All mutant forms of SYT1 were expressed at levels approximately equal to endogenous wild-type protein, and correctly localized to nerve terminals at rest, except for SYT1M303K, which was expressed at a lower level and failed to localize at nerve terminals. Following stimulation, SYT1I368T and SYT1N371K relocalized to nerve terminals at least as efficiently as wild-type SYT1. However, SYT1D304G and SYT1D366E failed to relocalize to nerve terminals following stimulation, indicative of impairments in endocytic retrieval and trafficking of SYT1. In addition, the presence of SYT1 variants at nerve terminals induced a slowing of exocytic rate following sustained action potential stimulation. The extent of disturbance to synaptic vesicle kinetics is mirrored by the severity of the affected individuals' phenotypes, suggesting that the efficiency of SYT1-mediated neurotransmitter release is critical to cognitive development. In summary, de novo dominant SYT1 missense mutations are associated with a recognizable neurodevelopmental syndrome, and further cases can now be diagnosed based on clinical features, electrophysiological signature and mutation characteristics. Variation in phenotype severity may reflect mutation-specific impact on the diverse physiological functions of SYT1.
Bain type of X-linked syndromic intellectual developmental disorder, caused by pathogenic missense variants in
HRNRPH2
, was initially described in six female individuals affected by ...moderate-to-severe neurodevelopmental delay. Although it was initially postulated that the condition would not be compatible with life in males, several affected male individuals harboring pathogenic variants in
HNRNPH2
have since been documented. However, functional in-vitro analyses of identified variants have not been performed and, therefore, possible genotype–phenotype correlations remain elusive. Here, we present eight male individuals, including a pair of monozygotic twins, harboring pathogenic or likely pathogenic
HNRNPH2
variants. Notably, we present the first individuals harboring nonsense or frameshift variants who, similarly to an individual harboring a de novo p.(Arg29Cys) variant within the first quasi-RNA-recognition motif (qRRM), displayed mild developmental delay, and developed mostly autistic features and/or psychiatric co-morbidities. Additionally, we present two individuals harboring a recurrent de novo p.(Arg114Trp), within the second qRRM, who had a severe neurodevelopmental delay with seizures. Functional characterization of the three most common
HNRNPH2
missense variants revealed dysfunctional nucleocytoplasmic shuttling of proteins harboring the p.(Arg206Gln) and p.(Pro209Leu) variants, located within the nuclear localization signal, whereas proteins with p.(Arg114Trp) showed reduced interaction with members of the large assembly of splicing regulators (LASR). Moreover, RNA-sequencing of primary fibroblasts of the individual harboring the p.(Arg114Trp) revealed substantial alterations in the regulation of alternative splicing along with global transcriptome changes. Thus, we further expand the clinical and variant spectrum in
HNRNPH2
-associated disease in males and provide novel molecular insights suggesting the disorder to be a spliceopathy on the molecular level.
Very preterm infants are at high risk for suboptimal nutrition in the first weeks of life leading to insufficient weight gain and complications arising from metabolic imbalances such as insufficient ...bone mineral accretion. We investigated the use of a novel set of standardized parenteral nutrition (PN; MUC PREPARE) solutions regarding improving nutritional intake, accelerating termination of parenteral feeding, and positively affecting growth in comparison to individually prescribed and compounded PN solutions. We studied the effect of MUC PREPARE on macro- and micronutrient intake, metabolism, and growth in 58 very preterm infants and compared results to a historic reference group of 58 very preterm infants matched for clinical characteristics. Infants receiving MUC PREPARE demonstrated improved macro- and micronutrient intake resulting in balanced electrolyte levels and stable metabolomic profiles. Subsequently, improved energy supply was associated with up to 1.5 weeks earlier termination of parenteral feeding, while simultaneously reaching up to 1.9 times higher weight gain at day 28 in extremely immature infants (<27 GA weeks) as well as overall improved growth at 2 years of age for all infants. The use of the new standardized PN solution MUC PREPARE improved nutritional supply and short- and long-term growth and reduced PN duration in very preterm infants and is considered a superior therapeutic strategy.
High-impact pathogenic variants in more than a thousand genes are involved in Mendelian forms of neurodevelopmental disorders (NDD).
This study describes the molecular and clinical characterisation ...of 28 probands with NDD harbouring heterozygous
coding variants, occurring de novo for all those whose transmission could have been verified (26/28).
A total of 15 unique variants leading to amino acid changes or deletions were identified: 12 missense variants, two in-frame deletions of one codon, and one canonical splice variant leading to a deletion of two amino acid residues. Recurrently identified variants were present in several unrelated individuals: p.(Phe180del), p.(Leu190Pro), p.(Leu190Arg), p.(Gly199Ser), p.(Val254Ile) and p.(Glu376del).
encodes the Argonaute 1 protein, which functions in gene-silencing pathways mediated by small non-coding RNAs. Three-dimensional protein structure predictions suggest that these variants might alter the flexibility of the AGO1 linker domains, which likely would impair its function in mRNA processing. Affected individuals present with intellectual disability of varying severity, as well as speech and motor delay, autistic behaviour and additional behavioural manifestations.
Our study establishes that de novo coding variants in
are involved in a novel monogenic form of NDD, highly similar to the recently reported
-related NDD.
POU3F3 variants cause developmental delay, behavioral problems, hypotonia and dysmorphic features. We investigated the phenotypic and genetic landscape, and genotype–phenotype correlations in ...individuals with POU3F3‐related disorders. We recruited unpublished individuals with POU3F3 variants through international collaborations and obtained updated clinical data on previously published individuals. Trio exome sequencing or single exome sequencing followed by segregation analysis were performed in the novel cohort. Functional effects of missense variants were investigated with 3D protein modeling. We included 28 individuals (5 previously published) from 26 families carrying POU3F3 variants; 23 de novo and one inherited from an affected parent. Median age at study inclusion was 7.4 years. All had developmental delay mainly affecting speech, behavioral difficulties, psychiatric comorbidities and dysmorphisms. Additional features included gastrointestinal comorbidities, hearing loss, ophthalmological anomalies, epilepsy, sleep disturbances and joint hypermobility. Autism, hearing and eye comorbidities, dysmorphisms were more common in individuals with truncating variants, whereas epilepsy was only associated with missense variants. In silico structural modeling predicted that all (likely) pathogenic variants destabilize the DNA‐binding region of POU3F3. Our study refined the phenotypic and genetic landscape of POU3F3‐related disorders, it reports the functional properties of the identified pathogenic variants, and delineates some genotype–phenotype correlations.
Clinicians should suspect POU3F3‐related disorder when a patient presents with developmental delay mainly affecting speech, psychiatric comorbidities and facial dysmorphisms. Additional features include gastrointestinal comorbidities, hearing loss, epilepsy, hypotonia, sleep disturbances, skeletal malformations and joint hypermobility.
Introduction
Metopic suture synostosis leading to trigonocephaly is considered the second most frequent type of craniosynostosis. Besides esthetic results, we present 25 consecutive pediatric cases ...operated upon metopic suture synostosis with a focus on the child’s motor, speech, and neurocognitive development.
Methods
Twenty-five children (aged 6 to 33 months; median 9.2 months) with trigonocephaly were operated upon between 2002 and 2012 with fronto-orbital advancement including frontal bone cranioplasty and fronto-orbital bandeau remodeling. Neurodevelopmental deficits were evaluated by a standardized questionnaire including gross motor function, manual coordination, speech, and cognitive function performed by independent pediatric/developmental neurologists before surgery and at 6 and 12 months of time interval postoperatively.
Results
Twenty-one (84 %) boys and four (16 %) girls were included in this study. Mean follow-up period was 33 ± 28 months. Outcome analysis for esthetic results showed a high degree of satisfaction by the parents and treating physicians in 23 cases (92 %). Preoperative evaluation revealed neurodevelopmental deficits in 10 children (40 %; six mild, four moderate degree). Twelve children (48 %) were proven to have a normal preoperative neuropediatric development. Mild or moderate developmental restraints were no longer apparent in 6/13, improved but still apparent in 3/13, and stable in 4/13, 6 months after cranial vault reconstruction. At 12 months of follow-up, deficits were no longer present in 9/13 and improved in 4/13. Apart from this cohort, two children were diagnosed with a syndromic form, and one child had a fetal valproate syndrome. In these three children, neurodevelopmental deficits were more pronounced. Neurocognitive progress was obvious, but was comparably slower, and major deficits were still apparent at last follow-up. All children with proven mild/moderate/severe deficits received intensive physiotherapy, logopedic, or neurobehavioral support.
Conclusions
As shown in a single-center observation, surgical correction of metopic suture synostosis not only refines esthetic appearance but also might improve neurodevelopmental outcome if deficits are apparent, even in syndromic forms of the deformity under additional physiotherapy, logopedic, or neurobehavioral support.
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