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.

Similar return to sport between double cortical button and docking techniques for ulnar collateral ligament reconstruction in baseball players.

BACKGROUND AND HYPOTHESIS: A double cortical button technique for ulnar collateral ligament reconstruction (UCLR) has advantages including significant control over graft tensioning, less concern about graft length, and minimized risk of bone tunnel fracture compared with traditional UCLR techniques. This double cortical button technique was recently found to be noninferior in mechanical performance to the traditional docking technique regarding joint strength, joint stiffness, and graft strain. However, clinical outcomes have not been compared between these UCLR techniques. Therefore, the purpose of this study was to determine whether baseball players who underwent UCLR with a double cortical button (double button) technique have similar return-to-sport (RTS) outcomes to baseball players who underwent UCLR with the traditional docking (docking) technique. MATERIALS AND METHODS: Baseball players who underwent primary UCLR from 2011 to 2020 across 2 institutions were identified. Included patients were contacted to complete a follow-up survey evaluating reoperations, RTS, and functional outcome scores. Functional outcome surveys include the Kerlan-Jobe Orthopaedic Clinic score, the Conway-Jobe score, the Andrews-Timmerman elbow score, and the Single Assessment Numeric Evaluation score. RESULTS: Overall, 78 male baseball players (age: 18.9 ± 2.4 years) with an average follow-up of 3.1 ± 2.4 years were evaluated, with 73 of the players being baseball pitchers. Players in the double button group more frequently received palmaris longus autografts (78% vs. 30%) and less frequently received gracilis autografts (22% vs. 58%) compared with players in the docking group (P = .001); however, all other demographic factors were similar between the groups. All players in the double button group were able to RTS in 11.1 ± 2.6 months, whereas 96% of players in the docking group were able to RTS in 13.5 ± 3.4 months (P > .05). All postoperative outcomes and patient-reported outcomes were statistically similar between the groups and remained similar after isolating pitchers only and after separating partial-thickness from full-thickness UCL tears (all P > .05). CONCLUSION: RTS and other postoperative outcomes may be similar between baseball players who underwent UCLR with the double button technique and the docking technique. Although future research may be necessary to strengthen clinical recommendations, these findings provide the first clinical outcomes in light of a recent cadaveric study finding similar elbow strength, joint stiffness, and graft strain compared with the docking technique.

Phenotypic Variability in Novel Doublecortin Gene Variants Associated with Subcortical Band Heterotopia.

Doublecortin, encoded by the DCX gene, plays a crucial role in the neuronal migration process during brain development. Pathogenic variants of the DCX gene are the major causes of the "lissencephaly (LIS) spectrum", which comprehends a milder phenotype like Subcortical Band Heterotopia (SBH) in heterozygous female subjects. We performed targeted sequencing in three unrelated female cases with SBH. We identified three DCX-related variants: a novel missense (c.601A>G: p.Lys201Glu), a novel nonsense (c.210C>G: p.Tyr70*), and a previously identified nonsense (c.907C>T: p.Arg303*) variant. The novel c.601A>G: p.Lys201Glu variant shows a mother-daughter transmission pattern across four generations. The proband exhibits focal epilepsy and achieved seizure freedom with a combination of oxcarbazepine and levetiracetam. All other affected members have no history of epileptic seizures. Brain MRIs of the affected members shows predominant fronto-central SBH with mixed pachygyria on the overlying cortex. The two nonsense variants were identified in two unrelated probands with SBH, severe drug-resistant epilepsy and intellectual disability. These novel DCX variants further expand the genotypic-phenotypic correlations of lissencephaly spectrum disorders. Our documented phenotypic descriptions of three unrelated families provide valuable insights and stimulate further discussions on DCX-SBH cases.

Early suppression of excitability in subcortical band heterotopia modifies epileptogenesis in rats.

Malformations of cortical development represent a major cause of epilepsy in childhood. However, the pathological substrate and dynamic changes leading to the development and progression of epilepsy remain unclear. Here, we characterized an etiology-relevant rat model of subcortical band heterotopia (SBH), a diffuse type of cortical malformation associated with drug-resistant seizures in humans. We used longitudinal electrographic recordings to monitor the age-dependent evolution of epileptiform discharges during the course of epileptogenesis in this model. We found both quantitative and qualitative age-related changes in seizures properties and patterns, accompanying a gradual progression towards a fully developed seizure pattern seen in adulthood. We also dissected the relative contribution of the band heterotopia and the overlying cortex to the development and age-dependent progression of epilepsy using timed and spatially targeted manipulation of neuronal excitability. We found that an early suppression of neuronal excitability in SBH slows down epileptogenesis in juvenile rats, whereas epileptogenesis is paradoxically exacerbated when excitability is suppressed in the overlying cortex. However, in rats with active epilepsy, similar manipulations of excitability have no effect on chronic spontaneous seizures. Together, our data support the notion that complex developmental alterations occurring in both the SBH and the overlying cortex concur to creating pathogenic circuits prone to generate seizures. Our study also suggests that early and targeted interventions could potentially influence the course of these altered developmental trajectories, and favorably modify epileptogenesis in malformations of cortical development.

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.

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.

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.

Non-pharmacological treatment options of drug-resistant epilepsy in subcortical band heterotopia: systematic review and illustrative case.

OBJECTIVE: Subcortical band heterotopia is a rare X-linked neuronal migration disorder primarily in females often associated with drug-resistant epilepsy. The aim of this study is to review the literature for non-pharmacological treatment options of drug-resistant epilepsy in subcortical band heterotopia. MATERIAL AND METHODS: In accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we performed a systematic review. Entering the keywords "double cortex," "subcortical band heterotopia," and "subcortical laminar heterotopia," we searched Scopus and PubMed databases. We paid particular attention to type of invasive and non-invasive treatment, radiological presentation, and outcome. We also describe a related case report, managed at Alder Hey Children's Hospital, Liverpool. RESULTS: The systematic literature review yielded 25 patients with subcortical band heterotopia and drug-resistant epilepsy who underwent non-pharmacological treatment. Including our patient, 26 patients were reported. The patients' mean age at seizure onset was 6.5 years (range 0.2-23) with a female sex predilection (5.25:1). The patients' mean age at invasive or non-invasive treatment was 21.5 years (range 6.5-51). The 26 patients underwent 29 non-pharmacological treatments. Ten patients underwent corpus callosotomy; 8 patients had a formal temporal lobectomy. Three patients had focal cortical resection. Two patients respectively had multiple subpial transections, insertion of a vagal nerve stimulator, or deep brain stimulation of the bilateral anterior nuclei of the thalamus. One patient underwent responsive focal neurostimulation. Another patient had transcutaneous stimulation of the vagal nerve. Sixteen patients reported a reduction or the disappearance of the seizures; 1 patient had no improvement. The outcome of 2 patients was classified class I, of 1 patient class II, of 1 patient class III, and of 5 patients class IV according to the Engel Epilepsy Surgery Outcome Scale. CONCLUSION: Mainly corpus callosotomy and formal temporal lobectomy have been performed as non-pharmacological treatment with few cases published overall. Several other invasive procedures and one non-invasive technique are based on case reports. The small number of reported cases prevents drawing a firm conclusion as to which non-pharmacological treatment is the best treatment option for refractive epilepsy in patients with subcortical band heterotopia.

[Analysis of ARX gene variant in a child with X-linked lissencephaly with abnormal genitalia].

OBJECTIVE: To explore the clinical characteristics and genetic basis for a child with X-linked lissencephaly with abnormal genitalia (XLAG). METHODS: A child with XLAG who had presented at the Third Affiliated Hospital of Zhengzhou University in May 2021 was selected as the study subject. Peripheral blood samples of the child and his parents were collected and subjected to high-throughput sequencing. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the result was analyzed by using bioinformatic software. RESULTS: The child was found to have harbored a hemizygous c.945_948del variant in exon 2 of the ARX gene, which as a frameshifting variant has resulted in a truncated protein. His mother was found to be heterozygous for the variant, whilst his father was of wild type. The variant was unreported previously. CONCLUSION: The hemizygous c.945_948del variant of the ARX gene probably underlay the XLAG in this patient. Above finding has provided a basis for the diagnosis and genetic counseling for this family.

[Prenatal genetic analysis of a fetus with Miller-Dieker syndrome].

OBJECTIVE: To explore the genetic basis for fetus with bilateral lateral ventriculomegaly. METHODS: Fetus umbilical cord blood and peripheral blood samples of its parents were collected. The fetus was subjected to chromosomal karyotyping, whilst the fetus and its parents were subjected to array comparative genomic hybridization (aCGH). The candidate copy number variation (CNV) were verified by qPCR, Application goldeneye DNA identification system was used to confirm the parental relationship. RESULTS: The fetus was found to have a normal karyotype. aCGH analysis indicated that it has carried a 1.16 Mb deletion at 17p13.3, which partially overlapped with the critical region of Miller-Dieker syndrome (MDS), in addition with a 1.33 Mb deletion at 17p12 region, which is associated with hereditary stress-susceptible peripheral neuropathy (HNPP). Its mother was also found to harbor the 1.33 Mb deletion at 17p12. qPCR analysis confirmed that the expression levels of genes from the 17p13.3 and 17p12 regions were about the half of that in the normal control, as well as the maternal peripheral blood sample. Parental relationship was confirmed between the fetus and its parents. Following genetic counseling, the parents has chosen to continue with the pregnancy. CONCLUSION: The fetus was diagnosed with Miller-Dieker syndrome due to the de novo deletion at 17p13.3. Ventriculomegaly may be an important indicator for prenatal ultrasonography in fetuses with MDS.

Bi-allelic Loss of Human APC2, Encoding Adenomatous Polyposis Coli Protein 2, Leads to Lissencephaly, Subcortical Heterotopia, and Global Developmental Delay.

Lissencephaly is a severe brain malformation in which failure of neuronal migration results in agyria or pachygyria and in which the brain surface appears unusually smooth. It is often associated with microcephaly, profound intellectual disability, epilepsy, and impaired motor abilities. Twenty-two genes are associated with lissencephaly, accounting for approximately 80% of disease. Here we report on 12 individuals with a unique form of lissencephaly; these individuals come from eight unrelated families and have bi-allelic mutations in APC2, encoding adenomatous polyposis coli protein 2. Brain imaging studies demonstrate extensive posterior predominant lissencephaly, similar to PAFAH1B1-associated lissencephaly, as well as co-occurrence of subcortical heterotopia posterior to the caudate nuclei, "ribbon-like" heterotopia in the posterior frontal region, and dysplastic in-folding of the mesial occipital cortex. The established role of APC2 in integrating the actin and microtubule cytoskeletons to mediate cellular morphological changes suggests shared function with other lissencephaly-encoded cytoskeletal proteins such as α-N-catenin (CTNNA2) and platelet-activating factor acetylhydrolase 1b regulatory subunit 1 (PAFAH1B1, also known as LIS1). Our findings identify APC2 as a radiographically distinguishable recessive form of lissencephaly.

MACF1, Involved in the 1p34.2p34.3 Microdeletion Syndrome, is Essential in Cortical Progenitor Polarity and Brain Integrity.

1p34.2p34.3 deletion syndrome is characterized by an increased risk for autism. Microtubule Actin Crosslinking Factor 1 (MACF1) is one candidate gene for this syndrome. It is unclear, however, how MACF1 deletion is linked to brain development and neurodevelopmental deficits. Here we report on Macf1 deletion in the developing mouse cerebral cortex, focusing on radial glia polarity and morphological integrity, as these are critical factors in brain formation. We found that deleting Macf1 during cortical development resulted in double cortex/subcortical band heterotopia as well as disrupted cortical lamination. Macf1-deleted radial progenitors showed increased proliferation rates compared to control cells but failed to remain confined within their defined proliferation zone in the developing brain. The overproliferation of Macf1-deleted radial progenitors was associated with elevated cell cycle speed and re-entry. Microtubule stability and actin polymerization along the apical ventricular area were decreased in the Macf1 mutant cortex. Correspondingly, there was a disconnection between radial glial fibers and the apical and pial surfaces. Finally, we observed that Macf1-mutant mice exhibited social deficits and aberrant emotional behaviors. Together, these results suggest that MACF1 plays a critical role in cortical progenitor proliferation and localization by promoting glial fiber stabilization and polarization. Our findings may provide insights into the pathogenic mechanism underlying the 1p34.2p34.3 deletion syndrome.

Novel lissencephaly-associated DCX variants in the C-terminal DCX domain affect microtubule binding and dynamics.

OBJECTIVE: Pathogenic variants in DCX on the X chromosome lead to lissencephaly and subcortical band heterotopia (SBH), brain malformations caused by neuronal migration defects. Its product doublecortin (DCX) binds to microtubules to modulate microtubule polymerization. How pathogenic DCX variants affect these activities remains not fully investigated. METHODS: DCX variants were identified using whole exome and Sanger sequencing from six families with lissencephaly/SBH. We examined how these variants affect DCX functions using microtubule binding, regrowth, and colocalization assays. RESULTS: We found novel DCX variants p.Val177AlafsTer31 and p.Gly188Trp, as well as reported variants p.Arg196His, p.Lys202Met, and p.Thr203Ala. Incidentally, all of the missense variants were clustered on the C-terminal DCX domain. The microtubule binding ability was significantly decreased in p.Val177AlafsTer31, p.Gly188Trp, p.Lys202Met, and previously reported p.Asp262Gly variants. Furthermore, expression of p.Val177AlafsTer31, p.Gly188Trp, p.Arg196His, p.Lys202Met, and p.Asp262Gly variants hindered microtubule growth in cells. There were also decreases in the colocalization of p.Val177AlafsTer31, p.Thr203Ala, and p.Asp262Gly variants to microtubules. SIGNIFICANCE: Our results indicate that these variants in the C-terminal DCX domain altered microtubule binding and dynamics, which may underlie neuronal migration defects during brain development.

An action-concept processing advantage in a patient with a double motor cortex.

Patients with atrophy in motor brain regions exhibit selective deficits in processing action-related meanings, suggesting a link between movement conceptualization and the amount of regional tissue. Here we examine such a relation in a unique opposite model: a rare patient with a double cortex (due to subcortical band heterotopia) in primary/supplementary motor regions, and no double cortex in multimodal semantic regions. We measured behavioral performance in action- and object-concept processing as well and resting-state functional connectivity. Both dimensions involved comparisons with healthy controls. Results revealed preserved accuracy in action and object categories for the patient. However, unlike controls, the patient exhibited faster performance for action than object concepts, a difference that was uninfluenced by general cognitive abilities. Moreover, this pattern was accompanied by heightened functional connectivity between the bilateral primary motor cortices. This suggests that a functionally active double motor cortex may entail action-processing advantages. Our findings offer new constraints for models of action semantics and motor-region function at large.

Clinical and neuroimaging findings in patients with lissencephaly/subcortical band heterotopia spectrum: a magnetic resonance conventional and diffusion tensor study.

PURPOSE: To clarify brain abnormalities on magnetic resonance imaging (MRI) and its clinical implications in lissencephaly/subcortical band heterotopia (LIS/SBH) spectrum patients. METHODS: The clinical severity and classification according to Di Donato were retrospectively reviewed in 23 LIS/SBH spectrum patients. The morphological and signal abnormalities of the brainstem, corpus callosum, and basal ganglia were also assessed. The brainstem distribution pattern of the corticospinal tract (CST) was analyzed by diffusion tensor imaging (DTI) and categorized into two types: normal pattern, in which the CST and medial lemniscus (ML) are separated by the dorsal portion of the transverse pontine fiber, and the abnormal pattern, in which the CST and ML are juxtaposed on the dorsal portion of a single transverse pontine fiber. Correlations between MR grading score and potential additional malformative findings of the brain and clinical symptoms were investigated. RESULTS: All patients with grade 3 (n = 5) showed brainstem deformities, signal abnormalities of pontine surface and had a tendency of basal ganglia deformity and callosal hypoplasia whereas those abnormalities were rarely seen in patients with grade 1 and 2 (n = 18). For DTI analysis, the patients with grade 3 LIS/SBH had typically abnormal CST, whereas the patients with grade 1 and 2 LIS/SBH had normal CST. The classification was well correlated with CST and brainstem abnormalities and clinical severity. CONCLUSION: MR assessment including DTI analysis may be useful in assessing the clinical severity in LIS/BH spectrum and may provide insight into its developmental pathology.

Prenatal diagnosis of Miller-Dieker syndrome by chromosomal microarray.

OBJECTIVE: To assess the experience on prenatal diagnosis of Miller-Dieker syndrome (MDS) to further delineate the fetal presentation of this syndrome. METHODS: This was a retrospective study. Fetal MDS was diagnosed prenatally by chromosomal microarray (CMA). Clinical data were reviewed for these cases, including maternal characteristics, indications for prenatal diagnosis, sonographic findings, CMA results, and pregnancy outcomes. RESULTS: Four cases were diagnosis as MDS by CMA. The most common sonographic features were ventriculomegaly (3/4) and polyhydramnios (2/4). Deletion sizes ranged from 1.5 to 5.4 Mb. All microdeletions were located at the MDS critical region and showed haploinsufficiency of the YWHAE, CRK, and PAFAH1B1. All patients chose to terminate the pregnancy. Parental chromosome analysis were preformed in three cases and demonstrated that two cases were de novo and one case was caused by inherited derivative chromosomes from parental balanced translocations. CONCLUSION: The most common prenatal ultrasound findings of MDS were ventriculomegaly and polyhydramnios. CMA can improve diagnostic precision for detecting MDS.

[Prenatal diagnosis and genetic analysis of a fetus with Miller-Dieker syndrome].

OBJECTIVE: To explore the genetic basis for a fetus with lissencephaly. METHODS: Genomic DNA was extracted from amniotic fluid sample and subjected to copy number variation (CNV) analysis. RESULTS: The fetus was found to harbor a heterozygous 5.2 Mb deletion at 17p13.3p13.2, which encompassed the whole critical region of Miller-Dieker syndrome (MDS) (chr17: 1-2 588 909). CONCLUSION: The fetus was diagnosed with MDS. Deletion of the PAFAH1B1 gene may account for the lissencephaly found in the fetus.

A deletion in Eml1 leads to bilateral subcortical heterotopia in the tish rat.

Children with malformations of cortical development (MCD) are at risk for epilepsy, developmental delays, behavioral disorders, and intellectual disabilities. For a subset of these children, antiseizure medications or epilepsy surgery may result in seizure freedom. However, there are limited options for treating or curing the other conditions, and epilepsy surgery is not an option in all cases of pharmacoresistant epilepsy. Understanding the genetic and neurobiological mechanisms underlying MCD is a necessary step in elucidating novel therapeutic targets. The tish (telencephalic internal structural heterotopia) rat is a unique model of MCD with spontaneous seizures, but the underlying genetic mutation(s) have remained unknown. DNA and RNA-sequencing revealed that a deletion encompassing a previously unannotated first exon markedly diminished Eml1 transcript and protein abundance in the tish brain. Developmental electrographic characterization of the tish rat revealed early-onset of spontaneous spike-wave discharge (SWD) bursts beginning at postnatal day (P) 17. A dihybrid cross demonstrated that the mutant Eml1 allele segregates with the observed dysplastic cortex and the early-onset SWD bursts in monogenic autosomal recessive frequencies. Our data link the development of the bilateral, heterotopic dysplastic cortex of the tish rat to a deletion in Eml1.

Neuronal migration genes and a familial translocation t (3;17): candidate genes implicated in the phenotype.

BACKGROUND: While Miller-Dieker syndrome critical region deletions are well known delineated anomalies, submicroscopic duplications in this region have recently emerged as a new distinctive syndrome. So far, only few cases have been described overlapping 17p13.3 duplications. METHODS: In this study, we report on clinical and cytogenetic characterization of two new cases involving 17p13.3 and 3p26 chromosomal regions in two sisters with familial history of lissencephaly. Fluorescent In Situ Hybridization and array Comparative Genomic Hybridization were performed. RESULTS: A deletion including the critical region of the Miller-Dieker syndrome of at least 2,9 Mb and a duplication of at least 3,6 Mb on the short arm of chromosome 3 were highlighted in one case. The opposite rearrangements, 17p13.3 duplication and 3p deletion, were observed in the second case. This double chromosomal aberration is the result of an adjacent 1:1 meiotic segregation of a maternal reciprocal translocation t(3,17)(p26.2;p13.3). CONCLUSIONS: 17p13.3 and 3p26 deletions have a clear range of phenotypic features while duplications still have an uncertain clinical significance. However, we could suggest that regardless of the type of the rearrangement, the gene dosage and interactions of CNTN4, CNTN6 and CHL1 in the 3p26 and PAFAH1B1, YWHAE in 17p13.3 could result in different clinical spectrums.

Direct and Collateral Alterations of Functional Cortical Circuits in a Rat Model of Subcortical Band Heterotopia.

Subcortical band heterotopia (SBH), also known as double-cortex syndrome, is a neuronal migration disorder characterized by an accumulation of neurons in a heterotopic band below the normotopic cortex. The majority of patients with SBH have mild to moderate intellectual disability and intractable epilepsy. However, it is still not clear how cortical networks are organized in SBH patients and how this abnormal organization contributes to improper brain function. In this study, cortical networks were investigated in the barrel cortex in an animal model of SBH induced by in utero knockdown of Dcx, main causative gene of this condition in human patients. When the SBH was localized below the Barrel Field (BF), layer (L) four projection to correctly positioned L2/3 pyramidal cells was weakened due to lower connectivity. Conversely, when the SBH was below an adjacent cortical region, the excitatory L4 to L2/3 projection was stronger due to increased L4 neuron excitability, synaptic strength and excitation/inhibition ratio of L4 to L2/3 connection. We propose that these developmental alterations contribute to the spectrum of clinical dysfunctions reported in patients with SBH.