The people behind the papers - Meng-Han Tsai, Wan-Cian Lin and Jin-Wu Tsai.

Lissencephaly is a neurodevelopmental disorder characterised by a loss of brain folds. In a new study, Jin-Wu Tsai and colleagues uncover a new variant of BAIAP2 that is associated with lissencephaly. To learn more about the story behind the paper, we caught up with first authors Meng-Han Tsai and Wan-Cian Lin, and corresponding author Jin-Wu Tsai, Professor at National Yang Ming Chiao Tung University, Taiwan.

Novel lissencephaly-associated NDEL1 variant reveals distinct roles of NDE1 and NDEL1 in nucleokinesis and human cortical malformations.

The development of the cerebral cortex involves a series of dynamic events, including cell proliferation and migration, which rely on the motor protein dynein and its regulators NDE1 and NDEL1. While the loss of function in NDE1 leads to microcephaly-related malformations of cortical development (MCDs), NDEL1 variants have not been detected in MCD patients. Here, we identified two patients with pachygyria, with or without subcortical band heterotopia (SBH), carrying the same de novo somatic mosaic NDEL1 variant, p.Arg105Pro (p.R105P). Through single-cell RNA sequencing and spatial transcriptomic analysis, we observed complementary expression of Nde1/NDE1 and Ndel1/NDEL1 in neural progenitors and post-mitotic neurons, respectively. Ndel1 knockdown by in utero electroporation resulted in impaired neuronal migration, a phenotype that could not be rescued by p.R105P. Remarkably, p.R105P expression alone strongly disrupted neuronal migration, increased the length of the leading process, and impaired nucleus-centrosome coupling, suggesting a failure in nucleokinesis. Mechanistically, p.R105P disrupted NDEL1 binding to the dynein regulator LIS1. This study identifies the first lissencephaly-associated NDEL1 variant and sheds light on the distinct roles of NDE1 and NDEL1 in nucleokinesis and MCD pathogenesis.

Prenatal diagnosis of microcephaly with simplified gyral pattern: series of eight cases.

Microcephaly with simplified gyral pattern (MSG) is an intrinsic genetic central nervous system disorder, characterized by microcephaly (a reduction of brain volume) and a simplified gyral pattern (a reduced number of gyri and shallow sulci associated with normal cortical thickness and neuroanatomical architecture), related to a reduced number of neuronal progenitors in the germinal matrix. We report the first prenatal series of MSG and define the prenatal imaging pattern, which should inform diagnosis and guide prenatal counseling in cases of fetal microcephaly. In this single-center retrospective study of fetuses with MSG, we assessed features on ultrasound and magnetic resonance imaging (MRI), as well as genetic and neuropathological/postnatal data. We included eight patients who had been referred following observation of microcephaly. Ultrasound examination confirmed microcephaly, with a mean growth delay in head circumference of 3.4 weeks, associated with both a lack of gyration and a lack of opercularization of the Sylvian fissure and without any extracephalic anomaly. Fetal brain MRI confirmed lack of gyration with normal cortical thickness and normal intensity of the white matter in all cases. These MRI features led to exclusion of migration/corticogenesis disorders (lissencephaly/polymicrogyria), instead suggesting MSG. The posterior fossa was normal in seven of the eight cases. The corpus callosum was thin in four cases, hypoplastic in two and dysgenetic in two. In four cases, the pregnancy was terminated. The diagnosis of MSG was confirmed from neuropathological and postnatal MRI data. MSG was associated with a genetic diagnosis of RTTN (n = 1) and ASPM (n = 2) biallelic variants in three of the six cases in which genetic work-up was performed. Mild or moderate intellectual deficit with speech delay was present in the three surviving children who were at least 5 years of age at their last examination, without seizures. In conclusion, in the presence of isolated fetal microcephaly with lack of gyration on ultrasound, fetal cerebral MRI is key to diagnosing MSG, which, in the majority of cases, affects the supratentorial space exclusively, and to ruling out other cortical malformations that show a similar sonographic pattern. In addition to imaging, genetic assessment may guide prenatal counseling, since the prenatal prognosis of MSG is different from that of both diffuse polymicrogyria and lissencephaly. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Bi-allelic truncating variants in CASP2 underlie a neurodevelopmental disorder with lissencephaly.

Lissencephaly (LIS) is a malformation of cortical development due to deficient neuronal migration and abnormal formation of cerebral convolutions or gyri. Thirty-one LIS-associated genes have been previously described. Recently, biallelic pathogenic variants in CRADD and PIDD1, have associated with LIS impacting the previously established role of the PIDDosome in activating caspase-2. In this report, we describe biallelic truncating variants in CASP2, another subunit of PIDDosome complex. Seven patients from five independent families presenting with a neurodevelopmental phenotype were identified through GeneMatcher-facilitated international collaborations. Exome sequencing analysis was carried out and revealed two distinct novel homozygous (NM_032982.4:c.1156delT (p.Tyr386ThrfsTer25), and c.1174 C > T (p.Gln392Ter)) and compound heterozygous variants (c.[130 C > T];[876 + 1 G > T] p.[Arg44Ter];[?]) in CASP2 segregating within the families in a manner compatible with an autosomal recessive pattern. RNA studies of the c.876 + 1 G > T variant indicated usage of two cryptic splice donor sites, each introducing a premature stop codon. All patients from whom brain MRIs were available had a typical fronto-temporal LIS and pachygyria, remarkably resembling the CRADD and PIDD1-related neuroimaging findings. Other findings included developmental delay, attention deficit hyperactivity disorder, hypotonia, seizure, poor social skills, and autistic traits. In summary, we present patients with CASP2-related ID, anterior-predominant LIS, and pachygyria similar to previously reported patients with CRADD and PIDD1-related disorders, expanding the genetic spectrum of LIS and lending support that each component of the PIDDosome complex is critical for normal development of the human cerebral cortex and brain function.

A lissencephaly-associated BAIAP2 variant causes defects in neuronal migration during brain development.

Lissencephaly is a neurodevelopmental disorder characterized by a loss of brain surface convolutions caused by genetic variants that disrupt neuronal migration. However, the genetic origins of the disorder remain unidentified in nearly one-fifth of people with lissencephaly. Using whole-exome sequencing, we identified a de novo BAIAP2 variant, p.Arg29Trp, in an individual with lissencephaly with a posterior more severe than anterior (P>A) gradient, implicating BAIAP2 as a potential lissencephaly gene. Spatial transcriptome analysis in the developing mouse cortex revealed that Baiap2 is expressed in the cortical plate and intermediate zone in an anterior low to posterior high gradient. We next used in utero electroporation to explore the effects of the Baiap2 variant in the developing mouse cortex. We found that Baiap2 knockdown caused abnormalities in neuronal migration, morphogenesis and differentiation. Expression of the p.Arg29Trp variant failed to rescue the migration defect, suggesting a loss-of-function effect. Mechanistically, the variant interfered with the ability of BAIAP2 to localize to the cell membrane. These results suggest that the functions of BAIAP2 in the cytoskeleton, cell morphogenesis and migration are important for cortical development and for the pathogenesis of lissencephaly in humans.

Automatic Quantification of Normal Brain Gyrification Patterns and Changes in Fetuses with Polymicrogyria and Lissencephaly Based on MRI.

BACKGROUND AND PURPOSE: The current imaging assessment of fetal brain gyrification is performed qualitatively and subjectively using sonography and MR imaging. A few previous studies have suggested methods for quantification of fetal gyrification based on 3D reconstructed MR imaging, which requires unique data and is time-consuming. In this study, we aimed to develop an automatic pipeline for gyrification assessment based on routinely acquired fetal 2D MR imaging data, to quantify normal changes with gestation, and to measure differences in fetuses with lissencephaly and polymicrogyria compared with controls. MATERIALS AND METHODS: We included coronal T2-weighted MR imaging data of 162 fetuses retrospectively collected from 2 clinical sites: 134 controls, 12 with lissencephaly, 13 with polymicrogyria, and 3 with suspected lissencephaly based on sonography, yet with normal MR imaging diagnoses. Following brain segmentation, 5 gyrification parameters were calculated separately for each hemisphere on the basis of the area and ratio between the contours of the cerebrum and its convex hull. Seven machine learning classifiers were evaluated to differentiate control fetuses and fetuses with lissencephaly or polymicrogyria. RESULTS: In control fetuses, all parameters changed significantly with gestational age (P < .05). Compared with controls, fetuses with lissencephaly showed significant reductions in all gyrification parameters (P ≤ .02). Similarly, significant reductions were detected for fetuses with polymicrogyria in several parameters (P ≤ .001). The 3 suspected fetuses showed normal gyrification values, supporting the MR imaging diagnosis. An XGBoost-linear algorithm achieved the best results for classification between fetuses with lissencephaly and control fetuses (n = 32), with an area under the curve of 0.90 and a recall of 0.83. Similarly, a random forest classifier showed the best performance for classification of fetuses with polymicrogyria and control fetuses (n = 33), with an area under the curve of 0.84 and a recall of 0.62. CONCLUSIONS: This study presents a pipeline for automatic quantification of fetal brain gyrification and provides normal developmental curves from a large cohort. Our method significantly differentiated fetuses with lissencephaly and polymicrogyria, demonstrating lower gyrification values. The method can aid radiologic assessment, highlight fetuses at risk, and may improve early identification of fetuses with cortical malformations.

Lissencephaly With Cerebellar Hypoplasia Due To a New RELN Mutation.

Lissencephaly with cerebellar hypoplasia (LCH) is a rare variant form of lissencephaly, its distinctive neuroradiological phenotype being an important investigation clue regarding the potential involved genes, including variants in RELN gene. We report on a case of LCH whose clinical and neuroradiological features led to the identification of a homozygous pathogenic variant in RELN gene that has not been previously reported in the scientific literature.

Loss of Twist1 and balanced retinoic acid signaling from the meninges causes cortical folding in mice.

Secondary lissencephaly evolved in mice due to effects on neurogenesis and the tangential distribution of neurons. Signaling pathways that help maintain lissencephaly are still poorly understood. We show that inactivating Twist1 in the primitive meninges causes cortical folding in mice. Cell proliferation in the meninges is reduced, causing loss of arachnoid fibroblasts that express Raldh2, an enzyme required for retinoic acid synthesis. Regionalized loss of Raldh2 in the dorsolateral meninges is first detected when folding begins. The ventricular zone expands and the forebrain lengthens at this time due to expansion of apical radial glia. As the cortex expands, regionalized differences in the levels of neurogenesis are coupled with changes to the tangential distribution of neurons. Consequentially, cortical growth at and adjacent to the midline accelerates with respect to more dorsolateral regions, resulting in cortical buckling and folding. Maternal retinoic acid supplementation suppresses cortical folding by normalizing forebrain length, neurogenesis and the tangential distribution of neurons. These results suggest that Twist1 and balanced retinoic acid signaling from the meninges are required to maintain normal levels of neurogenesis and lissencephaly in mice.

Further characterization of CEP85L-associated lissencephaly type 10: Report of a three-generation family and review of the literature.

Lissencephaly type 10 is a recently reported condition characterized by posterior predominant abnormalities in gyration with associated seizures, developmental delays or intellectual disability. We report a boy who presented at 5 years of age with epilepsy and developmental delays. His family history was notable for epilepsy in two prior generations associated with variable developmental and cognitive impact. Exome sequencing identified a novel missense variant in CEP85L [NM_001042475.2; c.196A>G, p.(Thr66Ala)] which segregated in four affected family members across three generations. Brain imaging of the proband demonstrated a posterior lissencephaly pattern with pachygyria, while other affected family members demonstrated a similar subcortical band heterotopia. This report expands the phenotypic spectrum of this rare disorder by describing a novel variant in CEP85L in a family with variable clinical and neuroimaging findings.

YWHAE loss of function causes a rare neurodevelopmental disease with brain abnormalities in human and mouse.

PURPOSE: Miller-Dieker syndrome is caused by a multiple gene deletion, including PAFAH1B1 and YWHAE. Although deletion of PAFAH1B1 causes lissencephaly unambiguously, deletion of YWHAE alone has not clearly been linked to a human disorder. METHODS: Cases with YWHAE variants were collected through international data sharing networks. To address the specific impact of YWHAE loss of function, we phenotyped a mouse knockout of Ywhae. RESULTS: We report a series of 10 individuals with heterozygous loss-of-function YWHAE variants (3 single-nucleotide variants and 7 deletions <1 Mb encompassing YWHAE but not PAFAH1B1), including 8 new cases and 2 follow-ups, added with 5 cases (copy number variants) from literature review. Although, until now, only 1 intragenic deletion has been described in YWHAE, we report 4 new variants specifically in YWHAE (3 splice variants and 1 intragenic deletion). The most frequent manifestations are developmental delay, delayed speech, seizures, and brain malformations, including corpus callosum hypoplasia, delayed myelination, and ventricular dilatation. Individuals with variants affecting YWHAE alone have milder features than those with larger deletions. Neuroanatomical studies in Ywhae-/- mice revealed brain structural defects, including thin cerebral cortex, corpus callosum dysgenesis, and hydrocephalus paralleling those seen in humans. CONCLUSION: This study further demonstrates that YWHAE loss-of-function variants cause a neurodevelopmental disease with brain abnormalities.

A likely pathogenic ACTG1 variant in a child showing partial phenotypic overlap with Baraitser-Winter syndrome.

Baraitser-Winter syndrome (BRWS) is a rare autosomal dominant disease (AD) caused by heterozygous variants in ACTB (BRWS1) or ACTG1 (BRWS2) genes. BRWS features developmental delay/intellectual disability of variable degree and craniofacial dysmorphisms. Brain abnormalities (especially pachygyria), microcephaly, epilepsy, as well as hearing impairment, cardiovascular and genitourinary abnormalities may be present. We report on a 4-year-old female, who was addressed to our institution because of psychomotor delay associated with microcephaly and dysmorphic features, short stature, mild bilateral sensorineural hearing loss, mild cardiac septal hypertrophy, and abdominal swelling. Clinical exome sequencing detected a c.617G>A p.(Arg206Gln) de novo variant in ACTG1 gene. Such variant has been previously reported in association with a form of AD nonsyndromic sensorineural progressive hearing loss and we classified it as likely pathogenic according to ACMG/AMP criteria, despite our patient's phenotype only partially overlapped BWRS2. Our finding supports the extreme variability of the ACTG1-related disorders, ranging from classical BRWS2 to nuanced clinical expressions not fitting the original description, and occasionally featuring previously undescribed clinical findings.

Missed diagnosis of lissencephaly after prenatal diagnosis: A case report.

RATIONALE: Lissencephaly (LIS) is a rare and serious cortical malformation characterized by a smooth or nearly smooth brain surface. With the progress of molecular genetics, platelet-activating factor acetylhydrolase brain isoform Ib is the most frequent type during the fetal period. Here, we report an infant with LIS who was missed although undergoing prenatal diagnosis. We aim to share our experiences and lessons. PATIENT CONCERNS: A 2-month-old male infant presented recurrent convulsions. Karyotype and copy number variation sequencing were conducted to be normal at the 23-week gestation because of bipedal varus and ventricular septal defect (2.3 mm). After birth, he suffered from epilepsy confirmed by video electroencephalogram exam, meanwhile, computed tomography and magnetic resonance imaging revealed pachygyria. The infant was diagnosed with LIS carrying a de-novo mutation c.817 C > T (p.Arg273 Ter,138) in exon 8 of platelet-activating factor acetylhydrolase brain isoform Ib (NM_000430) detected by whole-exome sequencing. DIAGNOSES: Based on the clinical characteristics, imaging, and genetic test findings, the infant was diagnosed with LIS. INTERVENTIONS: The patient was treated with topiramate and dose was adjusted according to the seizure frequency. OUTCOMES: The infant had recurrent seizures. The muscle tone of his extremities increased, and he could not look up or turn over actively at the age of 6 months. LESSONS: Comprehensive evaluation of a multi-disciplinary team should be recommended for patients with epilepsy and cerebral hypoplasia. Individuals with LIS during the fetal period might be missed due to atypical features. In fetuses with structural abnormalities, if karyotype and copy number variation sequencing are both normal, whole-exome sequencing may be an effective complementary means to detect pathogenic variants.

Lissencephaly-1 mutations enhance traumatic brain injury outcomes in Drosophila.

Traumatic brain injury (TBI) outcomes vary greatly among individuals, but most of the variation remains unexplained. Using a Drosophila melanogaster TBI model and 178 genetically diverse lines from the Drosophila Genetic Reference Panel (DGRP), we investigated the role that genetic variation plays in determining TBI outcomes. Following injury at 20-27 days old, DGRP lines varied considerably in mortality within 24 h ("early mortality"). Additionally, the disparity in early mortality resulting from injury at 20-27 vs 0-7 days old differed among DGRP lines. These data support a polygenic basis for differences in TBI outcomes, where some gene variants elicit their effects by acting on aging-related processes. Our genome-wide association study of DGRP lines identified associations between single nucleotide polymorphisms in Lissencephaly-1 (Lis-1) and Patronin and early mortality following injury at 20-27 days old. Lis-1 regulates dynein, a microtubule motor required for retrograde transport of many cargoes, and Patronin protects microtubule minus ends against depolymerization. While Patronin mutants did not affect early mortality, Lis-1 compound heterozygotes (Lis-1x/Lis-1y) had increased early mortality following injury at 20-27 or 0-7 days old compared with Lis-1 heterozygotes (Lis-1x/+), and flies that survived 24 h after injury had increased neurodegeneration but an unaltered lifespan, indicating that Lis-1 affects TBI outcomes independently of effects on aging. These data suggest that Lis-1 activity is required in the brain to ameliorate TBI outcomes through effects on axonal transport, microtubule stability, and other microtubule proteins, such as tau, implicated in chronic traumatic encephalopathy, a TBI-associated neurodegenerative disease in humans.

Further expansion and confirmation of phenotype in rare loss of YWHAE gene distinct from Miller-Dieker syndrome.

Deletion of 17p13.3 has varying degrees of severity on brain development based on precise location and size of the deletion. The most severe phenotype is Miller-Dieker syndrome (MDS) which is characterized by lissencephaly, dysmorphic facial features, growth failure, developmental disability, and often early death. Haploinsufficiency of PAFAH1B1 is responsible for the characteristic lissencephaly in MDS. The precise role of YWHAE haploinsufficiency in MDS is unclear. Case reports are beginning to elucidate the phenotypes of individuals with 17p13.3 deletions that have deletion of YWHAE but do not include deletion of PAFAH1B1. Through our clinical genetics practice, we identified four individuals with 17p13.3 deletion that include YWHAE but not PAFAH1B1. These patients have a similar phenotype of dysmorphic facial features, developmental delay, and leukoencephalopathy. In a review of the literature, we identified 19 patients with 17p13.3 microdeletion sparing PAFAH1B1 but deleting YWHAE. Haploinsufficiency of YWHAE is associated with brain abnormalities including cystic changes. These individuals have high frequency of epilepsy, intellectual disability, and dysmorphic facial features including prominent forehead, epicanthal folds, and broad nasal root. We conclude that deletion of 17p13.3 excluding PAFAH1B1 but including YWHAE is associated with a consistent phenotype and should be considered a distinct condition from MDS.

Tubulin mutations in human neurodevelopmental disorders.

Mutations causing dysfunction of tubulins and microtubule-associated proteins, also known as tubulinopathies, are a group of recently described entities that lead to complex brain malformations. Anatomical and functional consequences of the disruption of tubulins include microcephaly, combined with abnormal corticogenesis due to impaired migration or lamination and abnormal growth cone dynamics of projecting and callosal axons. Key imaging features of tubulinopathies are characterized by three major patterns of malformations of cortical development (MCD): lissencephaly, microlissencephaly, and dysgyria. Additional distinctive MRI features include dysmorphism of the basal ganglia, midline commissural structure hypoplasia or agenesis, and cerebellar and brainstem hypoplasia. Tubulinopathies can be diagnosed as early as 21-24 gestational weeks using imaging and neuropathology, with possible extreme microlissencephaly with an extremely thin cortex, lissencephaly with either thick or thin/intermediate cortex, and dysgyria combined with cerebellar hypoplasia, pons hypoplasia and corpus callosum dysgenesis. More than 100 MCD-associated mutations have been reported in TUBA1A, TUBB2B, or TUBB3 genes, whereas fewer than ten are known in other genes such TUBB2A, TUBB or TUBG1. Although these mutations are scattered along the α- and ß-tubulin sequences, recurrent mutations are consistently associated with almost identical cortical dysgenesis. Much of the evidence supports that these mutations alter the dynamic properties and functions of microtubules in several fashions. These include diminishing the abundance of functional tubulin heterodimers, altering GTP binding, altering longitudinal and lateral protofilament interactions, and impairing microtubule interactions with kinesin and/or dynein motors or with MAPs. In this review we discuss the recent advances in our understanding of the effects of mutations of tubulins and microtubule-associated proteins on human brain development and the pathogenesis of malformations of cortical development.

Prenatal Diagnosis of Lissencephaly Associated with Biallelic Pathologic Variants in the COQ2 Gene.

Primary CoQ10 deficiency comprises several clinical phenotypes. Nevertheless, there are no reports so far of lissencephaly linked to CoQ10 deficiency. Lissencephaly is a developmental condition associated with defective neuronal migration which may be depicted on fetal neurosonography by persistence of a laminar pattern beyond 34 weeks and abnormal cortical sulcation. We report an index case of a male fetus diagnosed with abnormal lamination, characterized by the persistence of a laminar pattern during late pregnancy, following a normal second trimester scan. Post-natal whole exome sequencing revealed biallelic pathologic variants in the COQ2 gene which encodes an enzyme that is part of coenzyme Q10 (COQ10 or ubiquinone) pathway and is involved in the biosynthesis of CoQ, a redox carrier in the mitochondrial respiratory chain and a lipid-soluble antioxidant. This case underscores the heterogeneity of the prenatal phenotypic presentation of pathogenic variants in the COQ2, namely lissencephaly.

A deficiência primária de CoQ10 traduz-se numa variedade de fenótipos clínicos. Todavia, não existe até à data nenhuma descrição deste défice associado a lisencefalia. A lisencefalia consiste numa alteração do desenvolvimento cortical cerebral em que se verifica um defeito na migração neuronal, detetável na neurossonografia pela persistência de um padrão de laminação cerebral após as 34 semanas de gestação e por alterações nas circunvoluções corticais. Neste trabalho descreve-se o caso de um feto masculino com um padrão de laminação cerebral alterado, detetado na avaliação ecográfica do terceiro trimestre, após exame morfológico sem alterações. A sequenciação pós-natal do exoma revelou uma variante bialélica patológica do gene COQ2, que codifica uma enzima da via da coenzima Q10 (COQ10 ou ubiquinona), envolvida na biossíntese do CoQ, um transportador redox da cadeia respiratória mitocondrial e anti-oxidante lipossolúvel. Com este caso, destaca-se a heterogeneidade fenotípica pré-natal das variantes patogénicas no gene COQ2.

Lissencephaly: presentation of a clinical case of LIS 1 with a diagnosis confirmed by MLPA method and indications for rehabilitation treatment in childhood.

Lissencephaly is a very rare clinical condition that affects the formation of the brain and causes severe psychomotor retardation, convulsions and muscular spasticity or hypotonia, often also associated with respiratory problems, facial dysmorphisms, abnormalities of the fingers and toes and difficulty swallowing resulting in reduced life expectancy. The clinical case described in the following article demonstrates the diagnostic process and rehabilitation treatment of a patient through a narrative review of the scientific literature and the presentation of this condition in order to provide indications to guide rehabilitation treatment in childhood.

Obsessive-compulsive symptoms in ACTG1-associated Baraitser-Winter cerebrofrontofacial syndrome.

Symptoms of obsessive-compulsive disorder (OCD) may rarely occur in the context of genetic syndromes. So far, an association between obsessive-compulsive symptoms (OCS) and ACTG1-associated Baraitser-Winter cerebrofrontofacial syndrome has not been described as yet. A thoroughly phenotyped patient with OCS and ACTG1-associated Baraitser-Winter cerebrofrontofacial syndrome is presented. The 25-year-old male patient was admitted to in-patient psychiatric care due to OCD. A whole-exome sequencing analysis was initiated as the patient also showed an autistic personality structure, below average intelligence measures, craniofacial dysmorphia signs, sensorineural hearing loss, and sinus cavernoma as well as subtle cardiac and ophthalmological alterations. The diagnosis of Baraitser-Winter cerebrofrontofacial syndrome type 2 was confirmed by the detection of a heterozygous likely pathogenic variant in the ACTG1 gene [c.1003C > T; p.(Arg335Cys), ACMG class 4]. The automated analysis of magnetic resonance imaging (MRI) revealed changes in the orbitofrontal, parietal, and occipital cortex of both sides and in the right mesiotemporal cortex. Electroencephalography (EEG) revealed intermittent rhythmic delta activity in the occipital and right temporal areas. Right mesiotemporal MRI and EEG alterations could be caused by a small brain parenchymal defect with hemosiderin deposits after a cavernomectomy. This paradigmatic case provides evidence of syndromic OCS in ACTG1-associated Baraitser-Winter cerebrofrontofacial syndrome. The MRI findings are compatible with a dysfunction of the cortico-striato-thalamo-cortical loops involved in OCD. If a common pathophysiology is confirmed in future studies, corresponding patients with Baraitser-Winter cerebrofrontofacial syndrome type 2 should be screened for OCS. The association may also contribute to a better understanding of OCD pathophysiology.

Bi-allelic CAMSAP1 variants cause a clinically recognizable neuronal migration disorder.

Non-centrosomal microtubules are essential cytoskeletal filaments that are important for neurite formation, axonal transport, and neuronal migration. They require stabilization by microtubule minus-end-targeting proteins including the CAMSAP family of molecules. Using exome sequencing on samples from five unrelated families, we show that bi-allelic CAMSAP1 loss-of-function variants cause a clinically recognizable, syndromic neuronal migration disorder. The cardinal clinical features of the syndrome include a characteristic craniofacial appearance, primary microcephaly, severe neurodevelopmental delay, cortical visual impairment, and seizures. The neuroradiological phenotype comprises a highly recognizable combination of classic lissencephaly with a posterior more severe than anterior gradient similar to PAFAH1B1(LIS1)-related lissencephaly and severe hypoplasia or absence of the corpus callosum; dysplasia of the basal ganglia, hippocampus, and midbrain; and cerebellar hypodysplasia, similar to the tubulinopathies, a group of monogenic tubulin-associated disorders of cortical dysgenesis. Neural cell rosette lineages derived from affected individuals displayed findings consistent with these phenotypes, including abnormal morphology, decreased cell proliferation, and neuronal differentiation. Camsap1-null mice displayed increased perinatal mortality, and RNAScope studies identified high expression levels in the brain throughout neurogenesis and in facial structures, consistent with the mouse and human neurodevelopmental and craniofacial phenotypes. Together our findings confirm a fundamental role of CAMSAP1 in neuronal migration and brain development and define bi-allelic variants as a cause of a clinically distinct neurodevelopmental disorder in humans and mice.