Cleft Lip Palate in a Patient with 5q14.3 Deletion Syndrome: A Possible Unreported Feature?

5q14.3 deletion syndrome (MIM#613443) is an uncommon but well-known syndrome characterized by intellectual disability, epilepsy, hypotonia, brain malformations, and facial dysmorphism. Most patients with this syndrome have lost one copy of the <i>MEF2C</i> gene (MIM*600662), whose haploinsufficiency is considered to be responsible for the distinctive phenotype. To date, nearly 40 cases have been reported; the deletion size and clinical spectrum are variable, and at least 6 cases without <i>MEF2C</i> involvement have been documented. We herein report the clinical and cytogenomic findings of an 11-year-old girl who has a 5q14.3q21.1 de novo deletion that does not involve <i>MEF2C</i> but shares the clinical features described in other reported patients. Moreover, she additionally presents with bilateral cleft-lip palate (CLP), which has not been previously reported as a feature of the syndrome. The most frequent syndromic forms of CLP were ruled out in our patient mainly by clinical examination, and Sanger sequencing was performed to discard the presence of a <i>TBX22</i> gene (MIM*300307) defect. Our report suggests CLP as a possible unreported feature and redefines the critical phenotypic regions of 5q14.3 deletion syndrome.

Complementing the phenotypical spectrum of TUBA1A tubulinopathy and its role in early-onset epilepsies

TUBA1A tubulinopathy is a rare neurodevelopmental disorder associated with brain malformations as well as early-onset and intractable epilepsy. As pathomechanisms and genotype-phenotype correlations are not completely understood, we aimed to provide further insights into the phenotypic and genetic spectrum. We here present a multicenter case series of ten unrelated individuals from four European countries using systematic MRI re-evaluation, protein structure analysis, and prediction score modeling. In two cases, pregnancy was terminated due to brain malformations. Amongst the eight living individuals, the phenotypic range showed various severity. Global developmental delay and severe motor impairment with tetraparesis was present in 63% and 50% of the subjects, respectively. Epilepsy was observed in 75% of the cases, which showed infantile onset in 83% and a refractory course in 50%. One individual presented a novel TUBA1A-associated electroclinical phenotype with evolvement from early myoclonic encephalopathy to continuous spike-and-wave during sleep. Neuroradiological features comprised a heterogeneous spectrum of cortical and extracortical malformations including rare findings such as cobblestone lissencephaly and subcortical band heterotopia. Two individuals developed hydrocephalus with subsequent posterior infarction. We report four novel and five previously published TUBA1A missense variants whose resulting amino acid substitutions likely affect longitudinal, lateral, and motor protein interactions as well as GTP binding. Assessment of pathogenic and benign variant distributions in synopsis with prediction scores revealed sections of variant enrichment and intolerance to missense variation. We here extend the clinical, neuroradiological, and genetic spectrum of TUBA1A tubulinopathy and provide insights into residue-specific pathomechanisms and genotype-phenotype correlations.

POTENTIAL RISK OF BRAIN DAMAGE AND POOR DEVELOPMENTAL OUTCOMES IN CHILDREN PRENATALLY EXPOSED TO SARS-COV-2: A SYSTEMATIC REVIEW

ABSTRACT Objective: To perform a systematic literature review to analyze existing data on the neurological effects of coronavirus on newborns. Data sources: We followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P), and searched the PubMed and Embase platforms for the keywords [brain damage OR pregnancy OR developmental outcomes] and [coronavirus OR SARS-CoV-2 OR SARS-CoV OR MERS-CoV] between January 1, 2000 and June 1, 2020. Data synthesis: Twenty-three reports described the course of pregnant women exposed to SARS-CoV-2, SARS-CoV, or MERS-CoV during the gestational period, eight to SARS-CoV-2, eight to SARS-CoV, and seven to MERS-CoV. No data were found on abnormalities in brain development or on a direct link between the virus and neurological abnormalities in the human embryo, fetus, or children. Spontaneous miscarriage, stillbirth, and termination of pregnancy were some complications connected with SARS/MERS-CoV infection. SARS-CoV-2 is not currently associated with complications in the gestational period. Conclusions: The literature has no data associating exposure to coronavirus during pregnancy with brain malformations and neurodevelopmental disorders. However, despite the lack of reports, monitoring the development of children exposed to SARS-CoV-2 is essential given the risk of complications in pregnant women and the potential neuroinvasive and neurotropic properties found in previous strains.

Somatic mutation involving diverse genes leads to a spectrum of focal cortical malformations

Post-zygotically acquired genetic variants, or somatic variants, that arise during cortical development have emerged as important causes of focal epilepsies, particularly those due to malformations of cortical development. Pathogenic somatic variants have been identified in many genes within the PI3K-AKT3-mTOR-signaling pathway in individuals with hemimegalencephaly and focal cortical dysplasia (type II), and more recently in SLC35A2 in individuals with focal cortical dysplasia (type I) or non-dysplastic epileptic cortex. Given the expanding role of somatic variants across different brain malformations, we sought to delineate the landscape of somatic variants in a large cohort of patients who underwent epilepsy surgery with hemimegalencephaly or focal cortical dysplasia. We evaluated samples from 123 children with hemimegalencephaly (n=16), focal cortical dysplasia type I and related phenotypes (n=48), focal cortical dysplasia type II (n=44), or focal cortical dysplasia type III (n=15) classified using imaging and pathological findings. We performed high-depth exome sequencing in brain tissue-derived DNA from each case and identified somatic single nucleotide, indel, and large copy number variants. In 75% of individuals with hemimegalencephaly and 29% with focal cortical dysplasia type II, we identified pathogenic variants in PI3K-AKT-mTOR pathway genes. Four of 48 cases with focal cortical dysplasia type I (8%) had a likely pathogenic variant in SLC35A2. While no other gene had multiple disease-causing somatic variants across the focal cortical dysplasia type I cohort, four individuals in this group had a single pathogenic or likely pathogenic somatic variant in CASK, KRAS, NF1, and NIPBL, genes associated with neurodevelopmental disorders. No rare pathogenic or likely pathogenic somatic variants in any neurological disease genes like those identified in the focal cortical dysplasia type I cohort were found in 63 neurologically normal controls (P = 0.017), suggesting a role for these novel variants. We also identified a somatic loss-of-function variant in the known epilepsy gene, PCDH19, present in a very small number of alleles in the dysplastic tissue from a female patient with focal cortical dysplasia IIIa with hippocampal sclerosis. In contrast to focal cortical dysplasia type II, neither focal cortical dysplasia type I nor III had somatic variants in genes that converge on a unifying biological pathway, suggesting greater genetic heterogeneity compared to type II. Importantly, we demonstrate that FCD types I, II, and III, are associated with somatic gene variants across a broad range of genes, many associated with epilepsy in clinical syndromes caused by germline variants, as well as including some not previously associated with radiographically evident cortical brain malformations.

Hydranencephaly: A rare case report

Hydranencephaly (HE) is a rare condition occurring in <1/10,000 births worldwide. It is one of the recognized forms of brain malformations that are usually associated with intrauterine fetal demise rarely seen in postnatal life. HE can often be misdiagnosed due to certain common features with other neurological abnormalities such as hydrocephalus, holoprosencephaly, and porencephaly. Here, we report the case of a 26-year-old pregnant patient at 34 weeks who was referred with ultrasonography finding of HE which was confirmed by fetal MRI. The decision to deliver the baby was taken expecting an extremely poor outcome after discussing with the family.

Tubulinopathy mutations in TUBA1A that disrupt neuronal morphogenesis and migration override XMAP215/Stu2 regulation of microtubule dynamics

ABSTRACTHeterozygous, missense mutations in α- or β-tubulin genes are associated with a wide range of human brain malformations, known as tubulinopathies. We seek to understand whether a mutation’s impact at the molecular and cellular levels scale with the severity of brain malformation. Here we focus on two mutations at the valine 409 residue of TUBA1A, V409I and V409A, identified in patients with pachygyria or lissencephaly, respectively. We find that ectopic expression of TUBA1A-V409I/A mutants disrupt neuronal migration in mice and promote excessive neurite branching and delayed retraction in primary neuronal cultures, accompanied by increased microtubule acetylation. To determine the molecular mechanisms, we modeled the V409I/A mutants in budding yeast and found that they promote intrinsically faster microtubule polymerization rates in cells and in reconstitution experiments with purified tubulin. In addition, V409I/A mutants decrease the recruitment of XMAP215/Stu2 to plus ends and ablate tubulin binding to TOG domains. In each assay tested, the TUBA1A-V409I mutant exhibits an intermediate phenotype between wild type and the more severe TUBA1A-V409A, reflecting the severity observed in brain malformations. Together, our data support a model in which the V409I/A mutations may limit tubulin conformational states and thereby disrupt microtubule regulation during neuronal morphogenesis and migration.

Kinetically Stabilizing Mutations in Beta Tubulins Create Isotype-Specific Brain Malformations

Mutations in the family of genes encoding the tubulin subunits of microtubules are associated with a spectrum of human brain malformations known as tubulinopathies. How these mutations impact tubulin activity to give rise to distinct developmental consequences is poorly understood. Here we report two patients exhibiting brain malformations characteristic of tubulinopathies and heterozygous T178M missense mutations in different β-tubulin genes, TUBB2A or TUBB3. RNAseq analysis indicates that both TUBB2A and TUBB3 are expressed in the brain during development, but only TUBB2A maintains high expression in neurons into adulthood. The T178 residue is highly conserved in β-tubulins and located in the exchangeable GTP-binding pocket of β-tubulin. To determine the impact of T178M on β-tubulin function we created an analogous mutation in the β-tubulin of budding yeast and show that the substitution acts dominantly to produce kinetically stabilized microtubules that assemble and disassemble slowly, with fewer transitions between these states. In vitro experiments with purified mutant tubulin demonstrate that T178M decreases the intrinsic assembly activity of β-tubulin and forms microtubules that rarely transition to disassembly. We provide evidence that the T178M substitution disrupts GTPase-dependent conformational changes in tubulin, providing a mechanistic explanation for kinetic stabilization. Our findings demonstrate the importance of tubulin’s GTPase activity during brain development, and indicate that tubulin isotypes play different, important roles during brain development.