Cerebral organoid and mouse models reveal a RAB39b-PI3K-mTOR pathway-dependent dysregulation of cortical development leading to macrocephaly/autism phenotypes.

Dysregulation of early neurodevelopment is implicated in macrocephaly/autism disorders. However, the mechanism underlying this dysregulation, particularly in human cells, remains poorly understood. Mutations in the small GTPase gene RAB39b are associated with X-linked macrocephaly, autism spectrum disorder (ASD), and intellectual disability. The in vivo roles of RAB39b in the brain remain unknown. We generated Rab39b knockout (KO) mice and found that they exhibited cortical neurogenesis impairment, macrocephaly, and hallmark ASD behaviors, which resembled patient phenotypes. We also produced mutant human cerebral organoids that were substantially enlarged due to the overproliferation and impaired differentiation of neural progenitor cells (NPCs), which resemble neurodevelopmental deficits in KO mice. Mechanistic studies reveal that RAB39b interacts with PI3K components and its deletion promotes PI3K-AKT-mTOR signaling in NPCs of mouse cortex and cerebral organoids. The mTOR activity is robustly enhanced in mutant outer radial glia cells (oRGs), a subtype of NPCs barely detectable in rodents but abundant in human brains. Inhibition of AKT signaling rescued enlarged organoid sizes and NPC overproliferation caused by RAB39b mutations. Therefore, RAB39b mutation promotes PI3K-AKT-mTOR activity and alters cortical neurogenesis, leading to macrocephaly and autistic-like behaviors. Our studies provide new insights into neurodevelopmental dysregulation and common pathways associated with ASD across species.

A recurrent de novo MAX p.Arg60Gln variant causes a syndromic overgrowth disorder through differential expression of c-Myc target genes.

Cyclin D2 (CCND2) stabilization underpins a range of macrocephaly-associated disorders through mutation of CCND2 or activating mutations in upstream genes encoding PI3K-AKT pathway components. Here, we describe three individuals with overlapping macrocephaly-associated phenotypes who carry the same recurrent de novo c.179G>A (p.Arg60Gln) variant in Myc-associated factor X (MAX). The mutation, located in the b-HLH-LZ domain, causes increased intracellular CCND2 through increased transcription but it does not cause stabilization of CCND2. We show that the purified b-HLH-LZ domain of MAXArg60Gln (Max∗Arg60Gln) binds its target E-box sequence with a lower apparent affinity. This leads to a more efficient heterodimerization with c-Myc resulting in an increase in transcriptional activity of c-Myc in individuals carrying this mutation. The recent development of Omomyc-CPP, a cell-penetrating b-HLH-LZ-domain c-Myc inhibitor, provides a possible therapeutic option for MAXArg60Gln individuals, and others carrying similar germline mutations resulting in dysregulated transcriptional c-Myc activity.

Deleterious ZNRF3 germline variants cause neurodevelopmental disorders with mirror brain phenotypes via domain-specific effects on Wnt/ß-catenin signaling.

Zinc and RING finger 3 (ZNRF3) is a negative-feedback regulator of Wnt/ß-catenin signaling, which plays an important role in human brain development. Although somatically frequently mutated in cancer, germline variants in ZNRF3 have not been established as causative for neurodevelopmental disorders (NDDs). We identified 12 individuals with ZNRF3 variants and various phenotypes via GeneMatcher/Decipher and evaluated genotype-phenotype correlation. We performed structural modeling and representative deleterious and control variants were assessed using in vitro transcriptional reporter assays with and without Wnt-ligand Wnt3a and/or Wnt-potentiator R-spondin (RSPO). Eight individuals harbored de novo missense variants and presented with NDD. We found missense variants associated with macrocephalic NDD to cluster in the RING ligase domain. Structural modeling predicted disruption of the ubiquitin ligase function likely compromising Wnt receptor turnover. Accordingly, the functional assays showed enhanced Wnt/ß-catenin signaling for these variants in a dominant negative manner. Contrarily, an individual with microcephalic NDD harbored a missense variant in the RSPO-binding domain predicted to disrupt binding affinity to RSPO and showed attenuated Wnt/ß-catenin signaling in the same assays. Additionally, four individuals harbored de novo truncating or de novo or inherited large in-frame deletion variants with non-NDD phenotypes, including heart, adrenal, or nephrotic problems. In contrast to NDD-associated missense variants, the effects on Wnt/ß-catenin signaling were comparable between the truncating variant and the empty vector and between benign variants and the wild type. In summary, we provide evidence for mirror brain size phenotypes caused by distinct pathomechanisms in Wnt/ß-catenin signaling through protein domain-specific deleterious ZNRF3 germline missense variants.

Germline variants in tumor suppressor FBXW7 lead to impaired ubiquitination and a neurodevelopmental syndrome.

Neurodevelopmental disorders are highly heterogenous conditions resulting from abnormalities of brain architecture and/or function. FBXW7 (F-box and WD-repeat-domain-containing 7), a recognized developmental regulator and tumor suppressor, has been shown to regulate cell-cycle progression and cell growth and survival by targeting substrates including CYCLIN E1/2 and NOTCH for degradation via the ubiquitin proteasome system. We used a genotype-first approach and global data-sharing platforms to identify 35 individuals harboring de novo and inherited FBXW7 germline monoallelic chromosomal deletions and nonsense, frameshift, splice-site, and missense variants associated with a neurodevelopmental syndrome. The FBXW7 neurodevelopmental syndrome is distinguished by global developmental delay, borderline to severe intellectual disability, hypotonia, and gastrointestinal issues. Brain imaging detailed variable underlying structural abnormalities affecting the cerebellum, corpus collosum, and white matter. A crystal-structure model of FBXW7 predicted that missense variants were clustered at the substrate-binding surface of the WD40 domain and that these might reduce FBXW7 substrate binding affinity. Expression of recombinant FBXW7 missense variants in cultured cells demonstrated impaired CYCLIN E1 and CYCLIN E2 turnover. Pan-neuronal knockdown of the Drosophila ortholog, archipelago, impaired learning and neuronal function. Collectively, the data presented herein provide compelling evidence of an F-Box protein-related, phenotypically variable neurodevelopmental disorder associated with monoallelic variants in FBXW7.

Rare and de novo coding variants in chromodomain genes in Chiari I malformation.

Chiari I malformation (CM1), the displacement of the cerebellum through the foramen magnum into the spinal canal, is one of the most common pediatric neurological conditions. Individuals with CM1 can present with neurological symptoms, including severe headaches and sensory or motor deficits, often as a consequence of brainstem compression or syringomyelia (SM). We conducted whole-exome sequencing (WES) on 668 CM1 probands and 232 family members and performed gene-burden and de novo enrichment analyses. A significant enrichment of rare and de novo non-synonymous variants in chromodomain (CHD) genes was observed among individuals with CM1 (combined p = 2.4 × 10-10), including 3 de novo loss-of-function variants in CHD8 (LOF enrichment p = 1.9 × 10-10) and a significant burden of rare transmitted variants in CHD3 (p = 1.8 × 10-6). Overall, individuals with CM1 were found to have significantly increased head circumference (p = 2.6 × 10-9), with many harboring CHD rare variants having macrocephaly. Finally, haploinsufficiency for chd8 in zebrafish led to macrocephaly and posterior hindbrain displacement reminiscent of CM1. These results implicate chromodomain genes and excessive brain growth in CM1 pathogenesis.

Loss of function of FAM177A1, a Golgi complex localized protein, causes a novel neurodevelopmental disorder.

PURPOSE: The function of FAM177A1 and its relationship to human disease is largely unknown. Recent studies have demonstrated FAM177A1 to be a critical immune-associated gene. One previous case study has linked FAM177A1 to a neurodevelopmental disorder in 4 siblings. METHODS: We identified 5 individuals from 3 unrelated families with biallelic variants in FAM177A1. The physiological function of FAM177A1 was studied in a zebrafish model organism and human cell lines with loss-of-function variants similar to the affected cohort. RESULTS: These individuals share a characteristic phenotype defined by macrocephaly, global developmental delay, intellectual disability, seizures, behavioral abnormalities, hypotonia, and gait disturbance. We show that FAM177A1 localizes to the Golgi complex in mammalian and zebrafish cells. Intersection of the RNA sequencing and metabolomic data sets from FAM177A1-deficient human fibroblasts and whole zebrafish larvae demonstrated dysregulation of pathways associated with apoptosis, inflammation, and negative regulation of cell proliferation. CONCLUSION: Our data shed light on the emerging function of FAM177A1 and defines FAM177A1-related neurodevelopmental disorder as a new clinical entity.

Clinical characteristics, longitudinal adaptive functioning, and association with electroencephalogram activity in PPP2R5D-related neurodevelopmental disorder.

Protein phosphatase 2 regulatory subunit B56δ related neurodevelopmental disorder (PPP2R5D-related NDD) is largely caused by de novo heterozygous missense PPP2R5D variants. We report medical characteristics, longitudinal adaptive functioning, and in-person neurological, motor, cognitive, and electroencephalogram (EEG) activity for PPP2R5D-related NDD. Forty-two individuals (median age 6 years, range = 0.8-25.3) with pathogenic/likely pathogenic PPP2R5D variants were assessed, and almost all variants were missense (97.6%) and de novo (85.7%). Common clinical symptoms were developmental delay, hypotonia, macrocephaly, seizures, autism, behavioral challenges, and sleep problems. The mean Gross motor functional measure-66 was 60.2 ± 17.3% and the mean Revised upper limb module score was 25.9 ± 8.8. The Vineland-3 adaptive behavior composite score (VABS-3 ABC) at baseline was low (M = 61.7 ± 16.8). VABS-3 growth scale value scores increased from baseline in all subdomains (range = 0.6-5.9) after a mean follow-up of 1.3 ± 0.3 years. EEG beta and gamma power were negatively correlated with VABS-3 score; p < 0.05. Individuals had a mean Quality-of-life inventory-disability score of 74.7 ± 11.4. Twenty caregivers (80%) had a risk of burnout based on the Caregiver burden inventory. Overall, the most common clinical manifestations of PPP2R5D-related NDD were impaired cognitive, adaptive function, and motor skills; and EEG activity was associated with adaptive functioning. This clinical characterization describes the natural history in preparation for clinical trials.

New cases of recently described Thauvin-Robinet-Faivre syndrome with a novel homozygous FIBP gene variant.

Thauvin-Robinet-Faivre syndrome (#617107) is a rare autosomal recessive overgrowth syndrome characterized by intellectual disability, facial dysmorphism, macrocephaly, and variable congenital malformations. It is caused by homozygous or compound heterozygous FIBP gene mutations. The FIBP gene is located on the 11q13.1 region and codes the acidic fibroblast growth factor intracellular binding protein, which is involved in the fibroblast growth factor (FGF) signaling pathway. FGF signaling is required for neurogenesis and neuronal precursor proliferation. The FGF controls cell proliferation, differentiation, and migration in embryonic development and in adult life. Overgrowth syndromes consist of a wide spectrum disorders characterized by prenatal and postnatal excess growth in weight and length, often associated malformations, intellectual disability, and neoplastic predisposition. Embryonic tumors are especially common in these syndromes. Thauvin-Robinet-Faivre syndrome is a recently described overgrowth syndrome with typical facial dysmorphic and clinical features. To date, only four patients have been reported with this disorder. Herein, two new cases of Thauvin-Robinet-Faivre syndrome are reported with overgrowth, intellectual disability, typical dysmorphic signs in one dysplastic kidney, and a novel homozygous FIBP gene variant. Exome sequencing analysis showed that both affected siblings share the same homozygous c. 412-3_415dupCAGTTTG FIBP gene variant. Reporting two new cases with this rare autosomal recessive overgrowth syndrome with a novel FIBP gene variant will support and expand the clinical spectrum of Thauvin-Robinet-Faivre syndrome. Also discussed will be the function of FIBP in tumorigenesis and the possible renal tumor susceptibility in heterozygous carriers will be emphasized.

Models of KPTN-related disorder implicate mTOR signalling in cognitive and overgrowth phenotypes.

KPTN-related disorder is an autosomal recessive disorder associated with germline variants in KPTN (previously known as kaptin), a component of the mTOR regulatory complex KICSTOR. To gain further insights into the pathogenesis of KPTN-related disorder, we analysed mouse knockout and human stem cell KPTN loss-of-function models. Kptn -/- mice display many of the key KPTN-related disorder phenotypes, including brain overgrowth, behavioural abnormalities, and cognitive deficits. By assessment of affected individuals, we have identified widespread cognitive deficits (n = 6) and postnatal onset of brain overgrowth (n = 19). By analysing head size data from their parents (n = 24), we have identified a previously unrecognized KPTN dosage-sensitivity, resulting in increased head circumference in heterozygous carriers of pathogenic KPTN variants. Molecular and structural analysis of Kptn-/- mice revealed pathological changes, including differences in brain size, shape and cell numbers primarily due to abnormal postnatal brain development. Both the mouse and differentiated induced pluripotent stem cell models of the disorder display transcriptional and biochemical evidence for altered mTOR pathway signalling, supporting the role of KPTN in regulating mTORC1. By treatment in our KPTN mouse model, we found that the increased mTOR signalling downstream of KPTN is rapamycin sensitive, highlighting possible therapeutic avenues with currently available mTOR inhibitors. These findings place KPTN-related disorder in the broader group of mTORC1-related disorders affecting brain structure, cognitive function and network integrity.

PTEN hamartoma tumor syndrome: Clinical and genetic characterization in pediatric patients.

OBJECTIVE: The aim of this study was to provide a full characterization of a cohort of 11 pediatric patients diagnosed with PTEN hamartoma tumor syndrome (PHTS). PATIENTS AND METHODS: Eleven patients with genetic diagnostic of PHTS were recruited between February 2019 and April 2023. Clinical, imaging, demographic, and genetic data were retrospectively collected from their hospital medical history. RESULTS: Regarding clinical manifestations, macrocephaly was the leading sign, present in all patients. Frontal bossing was the most frequent dysmorphism. Neurological issues were present in most patients. Dental malformations were described for the first time, being present in 27% of the patients. Brain MRI showed anomalies in 57% of the patients. No tumoral lesions were present at the time of the study. Regarding genetics, 72% of the alterations were in the tensin-type C2 domain of PTEN protein. We identified four PTEN genetic alterations for the first time. CONCLUSIONS: PTEN mutations appear with a wide variety of clinical signs and symptoms, sometimes associated with phenotypes which do not fit classical clinical diagnostic criteria for PHTS. We recommend carrying out a genetic study to establish an early diagnosis in children with significant macrocephaly. This facilitates personalized monitoring and enables anticipation of potential PHTS-related complications.

Syndrome of megalencephaly, mega corpus callosum, and complete lack of motor development: an unusual case and a literature review.

The syndrome of megalencephaly, mega corpus callosum (MEG-MegaCC) accompanied by complete lack of motor development is a rare condition with only few sporadic cases having been reported in the literature. In this paper, we describe a child from non-consanguineous parents presenting with MegaCC, psychomotor retardation, and language impairment linked to MEG-MegaCC syndrome. Genetic analysis, radiological findings, and detailed neurological phenotype of MEG-MegaCC syndrome with its overlapping syndromes would allow for a better classification of the disease spectrum.

Jugular foramen stenosis in external hydrocephalus in infants.

OBJECTIVE: To measure the size of jugular foramina in infants affected by external hydrocephalus (EH) and in a control group, to support the hypothesis that a jugular foramen (JF) stenosis may determine dural venous sinus alterations and increased venous outflow resistance as main pathophysiological factor. METHODS: Minimum, maximum, and mean values of JF areas were measured in a series of phase-contrast magnetic resonance venous angiography (angio MRV PCA3D) performed on 81 infants affected by EH. Results were compared with a group of 54 controls. RESULTS: Smaller JF area was significantly smaller in patients versus controls (43.1 ± 14.6 vs. 52.7 ± 17.8; p < 0.001) resulting in a significantly smaller mean JF areas in patients vs. controls (51.6 ± 15.8 vs. 57.0 ± 18.3; p = 0.043). In patients, smaller JF areas were significantly associated with higher venous obstruction grading score (VOGS) both on the right (p = 0.018) and on the left side (p = 0.005). Positional plagiocephaly (cranial vault asymmetry index > 3.5%) was more frequent among EH patients than controls (38/17) but the difference was not significant (p = 0.07). In the 38 plagiocephalic patients, JF area was smaller on the flattened side than the contralateral in a significant number of cases both in right (21/7) and left (9/1) plagiocephaly (p < 0.0005) as well as the mean area (48.2 + 16.4 mm2 vs. 57.5 + 20.7 mm2, p = 0.002) and VOGS was significantly higher on the plagiocephalic side than on the contralateral side (1.6 ± 1.1 vs. 1.1 ± 0.9, p = 0.019). CONCLUSION: In this series of infants affected by EH, the mean size of the ostium of both JF resulted significantly smaller than controls. JF stenosis was significantly associated with higher degrees of venous obstruction on both sides, suggesting a direct extrinsic effect of JF size on dural sinus lumen and possible consequent effect on venous outflow resistance. Positional plagiocephaly, when present, was associated with a decreased JF area and increased VOGS on the flattened side.

Overexpression of CD47 is associated with brain overgrowth and 16p11.2 deletion syndrome.

Copy number variation (CNV) at the 16p11.2 locus is associated with neuropsychiatric disorders, such as autism spectrum disorder and schizophrenia. CNVs of the 16p gene can manifest in opposing head sizes. Carriers of 16p11.2 deletion tend to have macrocephaly (or brain enlargement), while those with 16p11.2 duplication frequently have microcephaly. Increases in both gray and white matter volume have been observed in brain imaging studies in 16p11.2 deletion carriers with macrocephaly. Here, we use human induced pluripotent stem cells (hiPSCs) derived from controls and subjects with 16p11.2 deletion and 16p11.2 duplication to understand the underlying mechanisms regulating brain overgrowth. To model both gray and white matter, we differentiated patient-derived iPSCs into neural progenitor cells (NPCs) and oligodendrocyte progenitor cells (OPCs). In both NPCs and OPCs, we show that CD47 (a "don't eat me" signal) is overexpressed in the 16p11.2 deletion carriers contributing to reduced phagocytosis both in vitro and in vivo. Furthermore, 16p11.2 deletion NPCs and OPCs up-regulate cell surface expression of calreticulin (a prophagocytic "eat me" signal) and its binding sites, indicating that these cells should be phagocytosed but fail to be eliminated due to elevations in CD47. Treatment of 16p11.2 deletion NPCs and OPCs with an anti-CD47 antibody to block CD47 restores phagocytosis to control levels. While the CD47 pathway is commonly implicated in cancer progression, we document a role for CD47 in psychiatric disorders associated with brain overgrowth.

A New De Novo Missense Variant of the TET3 Gene in a Patient with Epilepsy and Macrocephaly.

The etiology of neurodevelopmental disorders and epilepsy is very heterogeneous and partly still unknown, and the research of causative genes related to these diseases is still in progress. In 2020, pathogenic variants of the TET3 gene were associated with Beck-Fahrner syndrome, which is characterized by neurodevelopmental delay, intellectual and learning disabilities of variable degree, growth abnormalities, hypotonia and seizures. Variants of TET3 have been described having both an autosomal dominant with a milder phenotype and an autosomal recessive pattern. To date, in the literature, only 28 patients are reported with pathogenic variants of the TET3 gene, and only 9 of them have epilepsy. We describe a 31-year-old woman with macrocephaly, mild neurodevelopmental delay and a long history of epilepsy. Trio-based exome sequencing identified a de novo heterozygous TET3 variant, c.2867G>A p.(Arg956Gln), never described before, absent in the general population and predicted to be potentially pathogenetic by bioinformatics tools. This report aims to describe the clinical history of our patient, the pharmacological treatment and clinical response, as well as the biological characteristics of this new variant.

Macrocephaly and Finger Changes: A Narrative Review.

Macrocephaly, characterized by an abnormally large head circumference, often co-occurs with distinctive finger changes, presenting a diagnostic challenge for clinicians. This review aims to provide a current synthetic overview of the main acquired and genetic etiologies associated with macrocephaly and finger changes. The genetic cause encompasses several categories of diseases, including bone marrow expansion disorders, skeletal dysplasias, ciliopathies, inherited metabolic diseases, RASopathies, and overgrowth syndromes. Furthermore, autoimmune and autoinflammatory diseases are also explored for their potential involvement in macrocephaly and finger changes. The intricate genetic mechanisms involved in the formation of cranial bones and extremities are multifaceted. An excess in growth may stem from disruptions in the intricate interplays among the genetic, epigenetic, and hormonal factors that regulate human growth. Understanding the underlying cellular and molecular mechanisms is important for elucidating the developmental pathways and biological processes that contribute to the observed clinical phenotypes. The review provides a practical approach to delineate causes of macrocephaly and finger changes, facilitate differential diagnosis and guide for the appropriate etiological framework. Early recognition contributes to timely intervention and improved outcomes for affected individuals.

Reduction Cranioplasty in Cases of Hydrocephalic Macrocephaly: Pearls and Pitfalls of Computer-Assisted Surgery.

Reduction cranioplasty may be indicated to address functional or cosmetic sequelae of hydrocephalic macrocephaly. With the advent of CAD/CAM digital workflow, surgeons can design and fabricate craniotomy guides, templates, and models that allow for precise cranial reconstruction. Although there are several advantages of virtual planning, pre-determined surgical plans may limit intraoperative flexibility, requiring surgeons to troubleshoot errors in pre-operative planning or model design. The purpose of this report is to present a series of cases demonstrating our institution's technique for single-stage reduction cranioplasty using a CAD/CAM workflow. This report will highlight the benefits and challenges associated with a contemporary digital workflow for reduction cranioplasty.

Opposite Modulation of RAC1 by Mutations in TRIO Is Associated with Distinct, Domain-Specific Neurodevelopmental Disorders.

The Rho-guanine nucleotide exchange factor (RhoGEF) TRIO acts as a key regulator of neuronal migration, axonal outgrowth, axon guidance, and synaptogenesis by activating the GTPase RAC1 and modulating actin cytoskeleton remodeling. Pathogenic variants in TRIO are associated with neurodevelopmental diseases, including intellectual disability (ID) and autism spectrum disorders (ASD). Here, we report the largest international cohort of 24 individuals with confirmed pathogenic missense or nonsense variants in TRIO. The nonsense mutations are spread along the TRIO sequence, and affected individuals show variable neurodevelopmental phenotypes. In contrast, missense variants cluster into two mutational hotspots in the TRIO sequence, one in the seventh spectrin repeat and one in the RAC1-activating GEFD1. Although all individuals in this cohort present with developmental delay and a neuro-behavioral phenotype, individuals with a pathogenic variant in the seventh spectrin repeat have a more severe ID associated with macrocephaly than do most individuals with GEFD1 variants, who display milder ID and microcephaly. Functional studies show that the spectrin and GEFD1 variants cause a TRIO-mediated hyper- or hypo-activation of RAC1, respectively, and we observe a striking correlation between RAC1 activation levels and the head size of the affected individuals. In addition, truncations in TRIO GEFD1 in the vertebrate model X. tropicalis induce defects that are concordant with the human phenotype. This work demonstrates distinct clinical and molecular disorders clustering in the GEFD1 and seventh spectrin repeat domains and highlights the importance of tight control of TRIO-RAC1 signaling in neuronal development.

De Novo Variants in SPOP Cause Two Clinically Distinct Neurodevelopmental Disorders.

Recurrent somatic variants in SPOP are cancer specific; endometrial and prostate cancers result from gain-of-function and dominant-negative effects toward BET proteins, respectively. By using clinical exome sequencing, we identified six de novo pathogenic missense variants in SPOP in seven individuals with developmental delay and/or intellectual disability, facial dysmorphisms, and congenital anomalies. Two individuals shared craniofacial dysmorphisms, including congenital microcephaly, that were strikingly different from those of the other five individuals, who had (relative) macrocephaly and hypertelorism. We measured the effect of SPOP variants on BET protein amounts in human Ishikawa endometrial cancer cells and patient-derived cell lines because we hypothesized that variants would lead to functional divergent effects on BET proteins. The de novo variants c.362G>A (p.Arg121Gln) and c. 430G>A (p.Asp144Asn), identified in the first two individuals, resulted in a gain of function, and conversely, the c.73A>G (p.Thr25Ala), c.248A>G (p.Tyr83Cys), c.395G>T (p.Gly132Val), and c.412C>T (p.Arg138Cys) variants resulted in a dominant-negative effect. Our findings suggest that these opposite functional effects caused by the variants in SPOP result in two distinct and clinically recognizable syndromic forms of intellectual disability with contrasting craniofacial dysmorphisms.

Impact of Macrocephaly, as an Isolated Trait, on EEG Signal as Measured by Spectral Power and Multiscale Entropy during the First Year of Life.

Macrocephaly has been associated with neurodevelopmental disorders; however, it has been mainly studied in the context of pathological or high-risk populations and little is known about its impact, as an isolated trait, on brain development in general population. Electroencephalographic (EEG) power spectral density (PSD) and signal complexity have shown to be sensitive to neurodevelopment and its alterations. We aimed to investigate the impact of macrocephaly, as an isolated trait, on EEG signal as measured by PSD and multiscale entropy during the first year of life. We recorded high-density EEG resting-state activity of 74 healthy full-term infants, 50 control (26 girls), and 24 macrocephalic (12 girls) aged between 3 and 11 months. We used linear regression models to assess group and age effects on EEG PSD and signal complexity. Sex and brain volume measures, obtained via a 3D transfontanellar ultrasound, were also included into the models to evaluate their contribution. Our results showed lower PSD of the low alpha (8-10 Hz) frequency band and lower complexity in the macrocephalic group compared to the control group. In addition, we found an increase in low alpha (8.5-10 Hz) PSD and in the complexity index with age. These findings suggest that macrocephaly as an isolated trait has a significant impact on brain activity during the first year of life.

Expansion of clinical and variant spectrum of EEF2-related neurodevelopmental disorder: Report of two additional cases.

Eukaryotic translation elongation factor 2 (eEF2), encoded by the gene EEF2, is an essential factor involved in the elongation phase of protein translation. A specific heterozygous missense variant (p.P596H) in EEF2 was originally identified in association with autosomal dominant adult-onset spinocerebellar ataxia-26 (SCA26). More recently, additional heterozygous missense variants in this gene have been described to cause a novel, childhood-onset neurodevelopmental disorder with benign external hydrocephalus. Herein, we report two unrelated individuals with a similar gene-disease correlation to support this latter observation. Patient 1 is a 7-year-old male with a previously reported, de novo missense variant (p.V28M) who has motor and speech delay, autism spectrum disorder, failure to thrive with relative macrocephaly, unilateral microphthalmia with coloboma and eczema. Patient 2 is a 4-year-old female with a novel de novo nonsense variant (p.Q145X) with motor and speech delay, hypotonia, macrocephaly with benign ventricular enlargement, and keratosis pilaris. These additional cases help to further expand the genotypic and phenotypic spectrum of this newly described EEF2-related neurodevelopmental syndrome.