Forebrain commissure formation in zebrafish embryo requires the binding of KLC1 to CRMP2.

Formation of the corpus callosum (CC), anterior commissure (AC), and postoptic commissure (POC), connecting the left and right cerebral hemispheres, is crucial for cerebral functioning. Collapsin response mediator protein 2 (CRMP2) has been suggested to be associated with the mechanisms governing this formation, based on knockout studies in mice and knockdown/knockout studies in zebrafish. Previously, we reported two cases of non-synonymous CRMP2 variants with S14R and R565C substitutions. Among the, the R565C substitution (p.R565C) was caused by the novel CRMP2 mutation c.1693C > T, and the patient presented with intellectual disability accompanied by CC hypoplasia. In this study, we demonstrate that crmp2 mRNA could rescue AC and POC formation in crmp2-knockdown zebrafish, whereas the mRNA with the R566C mutation could not. Zebrafish CRMP2 R566C corresponds to human CRMP2 R565C. Further experiments with transfected cultured cells indicated that CRMP2 with the R566C mutation could not bind to kinesin light chain 1 (KLC1). Knockdown of klc1a in zebrafish resulted in defective AC and POC formation, revealing a genetic interaction with crmp2. These findings suggest that the CRMP2 R566C mutant fails to bind to KLC1, preventing axonal elongation and leading to defective AC and POC formation in zebrafish and CC formation defects in humans. Our study highlights the importance of the interaction between CRMP2 and KLC1 in the formation of the forebrain commissures, revealing a novel mechanism associated with CRMP2 mutations underlying human neurodevelopmental abnormalities.

Significant phenotypic variability in a multigenerational family with an NFIA missense mutation: Case series and review of the literature.

We report the first multigenerational family with NFIA-related disorder from a missense variant. This case highlights the condition's phenotypic variability and the need for genetic testing when an initial diagnosis fails to explain all symptoms.

Lunapark deficiency leads to an autosomal recessive neurodevelopmental phenotype with a degenerative course, epilepsy and distinct brain anomalies.

LNPK encodes a conserved membrane protein that stabilizes the junctions of the tubular endoplasmic reticulum network playing crucial roles in diverse biological functions. Recently, homozygous variants in LNPK were shown to cause a neurodevelopmental disorder (OMIM#618090) in four patients displaying developmental delay, epilepsy and nonspecific brain malformations including corpus callosum hypoplasia and variable impairment of cerebellum. We sought to delineate the molecular and phenotypic spectrum of LNPK-related disorder. Exome or genome sequencing was carried out in 11 families. Thorough clinical and neuroradiological evaluation was performed for all the affected individuals, including review of previously reported patients. We identified 12 distinct homozygous loss-of-function variants in 16 individuals presenting with moderate to profound developmental delay, cognitive impairment, regression, refractory epilepsy and a recognizable neuroimaging pattern consisting of corpus callosum hypoplasia and signal alterations of the forceps minor ('ear-of-the-lynx' sign), variably associated with substantia nigra signal alterations, mild brain atrophy, short midbrain and cerebellar hypoplasia/atrophy. In summary, we define the core phenotype of LNPK-related disorder and expand the list of neurological disorders presenting with the 'ear-of-the-lynx' sign suggesting a possible common underlying mechanism related to endoplasmic reticulum-phagy dysfunction.

A Variant in TBCD Associated with Motoneuronopathy and Corpus Callosum Hypoplasia: A Case Report.

Mutations in the tubulin-specific chaperon D (TBCD) gene, involved in the assembly and disassembly of the α/ß-tubulin heterodimers, have been reported in early-onset progressive neurodevelopment regression, with epilepsy and mental retardation. We describe a rare homozygous variant in TBCD, namely c.881G>A/p.Arg294Gln, in a young woman with a phenotype dominated by distal motorneuronopathy and mild mental retardation, with neuroimaging evidence of corpus callosum hypoplasia. The peculiar phenotype is discussed in light of the molecular interpretation, enriching the literature data on tubulinopathies generated from TBCD mutations.

Mutación genética RAB11B: retraso psicomotor, braquicefalia, hipoplasia de cuerpo calloso. Primer caso descrito en España / Genetic mutation RAB11B: psychomotor retardation, brachycephaly, and corpus callosum hypoplasia. First case described in Spain

El complejo proteico RAB11B, miembro del complejo Rab GTPasa, codificado por el gen RAB11B, juega un papel importante en el desarrollo neuronal y en la formación de las funciones cognitivas. El gen RAB11B codifica un miembro de la subfamilia de las Rab11 GTPasas que se asocia con el reciclaje de las endosomas y participa en la regulación del tráfico de vesículas endoplásmicas. Se presenta el primer caso descrito en España de mutación en el gen RAB11B (mutación c.64G>A en heterocigosis), clínicamente caracterizado por retraso psicomotor, epilepsia, discapacidad intelectual, hipotonía, braquicefalia e hipoplasia del cuerpo calloso. Se realiza comparación del presente caso con otros cinco casos descritos a nivel mundial con la misma mutación, presentando las similitudes y rasgos distintivos(AU)

GTPase complex, encoded by the RAB11B gene, a member of the Rab protein complex which plays a significant role in neuronal development and the shaping of cognitive functions. The RAB11B gene encodes a member of the Rab11 GTPase subfamily that particularly associates with the recycling of endosomes and participates in the regulation of vesicular trafficking. We present the first case described in Spain of psychomotor retardation, intellectual disability due to a mutation in the RAB11B gene (c.64G>A mutation in heterozygosis), clinically characterized by psychomotor retardation, brachycephaly, corpus callosum hypoplasia, epilepsy and intellectual disability. The case is compared with other five cases described worldwide with the same mutation, presenting their similarities and distinctive features(AU)

A Case of Ophthalmoplegia, Hypotonia, and Developmental Delay in the Setting of Corpus Callosum Hypoplasia.

Anomalies of the corpus callosum, including complete agenesis, partial agenesis, and hypoplasia, are some of the most common brain malformations. Corpus callosum abnormalities are potentially syndromic, many of which have identifiable genetic etiologies. Patients affected with either syndromic or non-syndromic corpus callosum anomalies may also have associated ophthalmologic abnormalities. Some of the syndromes with corpus callosum malformations that also involve ophthalmologic findings include Aicardi syndrome, Mowat-Wilson syndrome, and Xia-Gibbs syndrome. This case report describes a patient with hypoplasia and possible dysgenesis of the corpus callosum noted on magnetic resonance imaging (MRI) who had several ophthalmologic findings, including ophthalmoplegia, strabismus, and nystagmus, associated with microcephaly, dysmorphic facial features, global developmental delay, hypotonia, and cryptorchidism. While several previously identified syndromes share similar clinical features with this patient, these findings may also represent an unidentified genetic syndrome, and the patient remains under evaluation for a genetic diagnosis. This report explores the differential for ophthalmologic abnormalities in the setting of corpus callosum hypoplasia.

Hypoplasia of the Corpus Callosum: A Single Center Experience and a Concise Literature Review.

AimCorpus callosum hypoplasia is described as a fully formed corpus callosum with reduced thickness. Our purpose is to evaluate the current knowledge about this anomaly including it's effect on the neurodevelopmental outcome and to report our single center experience. Methods: PubMed, Medline and reference lists were searched using combinations of these terms: "Hypoplasia of corpus callosum and prenatal diagnosis" and "neurodevelopmental outcome". Results: Eleven studies were included, with a final population of 48 patients (45 cases from literature plus 3 of our own cases). Hypoplasia of the corpus callosum was detected by ultrasound scan alone in 77% of cases: magnetic resonance confirmed the ultrasound suspicion in the remaining 23% of cases. Isolated form was detected in 31% cases. Adverse fetal outcomes occurred in 62% of cases, while 38% of cases were born alive. The neurodevelopmental outcome was found to be normal in 33% of cases. Conclusion: Antenatal detection of corpus callosum hypoplasia remains challenging. Counseling is difficult because neurodevelopmental outcomes are variable.

Novel BRPF1 mutation in a boy with intellectual disability, coloboma, facial nerve palsy and hypoplasia of the corpus callosum.

Mutations in the chromatin regulator gene BRPF1 were recently associated with the Intellectual Developmental Disorder With Dysmorphic Facies And Ptosis (IDDDFP). Up till now, clinical data of 22 patients are reported. Besides intellectual disability (ID), ptosis and blepharophimosis are frequent findings, with refraction problems, amblyopia and strabism as other reported ophthalmological features. Animal studies indicate BRPF1 as an important mediator in brain development. However, only 5 of 22 previously reported patients show structural brain abnormalities. We report on an additional patient harboring a novel de novo nonsense mutation p.(Glu219*) in BRPF1. He presented with ID, bilateral iris colobomas, facial nerve palsy and severe hypoplasia of the corpus callosum. Our findings support previous findings of brain abnormalities in BRPF1-mutations and indicates coloboma and facial nerve palsy as possible additional features of IDDDFP syndrome.

The case of pyridoxine dependent epilepsy misdiagnosed as non-ketotic hyperglycinemia.

Gazeteci-Tekin H, Demir M, Aktan G, Tekgül H, Gökben S. The case of pyridoxine dependent epilepsy misdiagnosed as non-ketotic hyperglycinemia. Turk J Pediatr 2019; 61: 599-603. Pyridoxine-dependent epilepsy (PDE) is a rare but an important condition, since early diagnosis and treatment result in normal or near normal psychomotor development. It is caused by mutations in the Antiquitin (ALDH7A1) gene. Different clinical findings may appear in the deficiency of pyridoxine, which is the cofactor of many enzymes. A wide variety of clinical and laboratory findings can cause confusion during diagnosis. We present a male with neonatal convulsions; structural brain anomaly, hyperglycinemia in CSF/plasma, with ALDH7A1 Compound heterozygote mutation.

Mutations in LNPK, Encoding the Endoplasmic Reticulum Junction Stabilizer Lunapark, Cause a Recessive Neurodevelopmental Syndrome.

The dynamic shape of the endoplasmic reticulum (ER) is a reflection of its wide variety of critical cell biological functions. Consequently, perturbation of ER-shaping proteins can cause a range of human phenotypes. Here, we describe three affected children (from two consanguineous families) who carry homozygous loss-of-function mutations in LNPK (previously known as KIAA1715); this gene encodes lunapark, which is proposed to serve as a curvature-stabilizing protein within tubular three-way junctions of the ER. All individuals presented with severe psychomotor delay, intellectual disability, hypotonia, epilepsy, and corpus callosum hypoplasia, and two of three showed mild cerebellar hypoplasia and atrophy. Consistent with a proposed role in neurodevelopmental disease, LNPK was expressed during brain development in humans and mice and was present in neurite-like processes in differentiating human neural progenitor cells. Affected cells showed the absence of full-length lunapark, aberrant ER structures, and increased luminal mass density. Together, our results implicate the ER junction stabilizer lunapark in establishing the corpus callosum.

Novel ABCD1 Gene Mutation in Adrenomyeloneuropathy with Hypoplasia and Agenesis of the Corpus Callosum.

BACKGROUND: Adult adrenomyeloneuropathy (AMN) is caused by mutations in the ABCD1 gene. Some pure AMN patients develop cerebral demyelination late in life. However, hypoplasia and agenesis of the corpus callosum (CC) has never been reported in AMN patients. OBJECTIVE: To describe a new clinical variant of AMN that is possibly caused by a novel ABCD1 gene mutation. METHODS: A total of 10 members in an X-linked inherited family were examined. The age at onset, progression of disability, and clinical manifestations were collected. Blood tests of the index case were conducted in an academic hospital. Cerebral and spinal MRI was performed in 4 affected members using a Siemens 3.0-T or Hitachi 1.0-T MR scanner. Whole-exome sequencing was conducted in the index case, which was subsequently validated by Sanger sequencing in the family. RESULTS: The patients displayed typical degenerative spastic paraparesis and peripheral sensorimotor neuropathy with some intrafamilial variations. In addition to neurological deficits, all male patients displayed alopecia since adolescence. Furthermore, an increase in plasma long-chain fatty acids was observed. Based on these presentations, adult AMN was diagnosed for the patients. Intriguingly, cerebral MRI showed multiple types of hypoplasia and agenesis of the CC including anterior remnant CC agenesis, truncated corpus and splenium, anterior remnant CC agenesis along with thin corpus and splenium. Whole-exome sequencing revealed a nonsense mutation (c.231G>A) which results in a truncated protein product (p.W77X) that might be nonfunctional. No other mutations associated with alopecia or hypoplasia and agenesis of the CC were identified in the exome-sequencing database. CONCLUSION: In addition to the typical symptoms such as spastic myelopathy, cognitive impairment, mixed neuropathy, and alopecia, AMN patients can also display hypoplasia and agenesis of the CC, which was not described in the other AMN patients reported before.

Prevalence and associated factors for agenesis of corpus callosum in Emilia Romagna (1981-2015).

Agenesis and hypoplasia of the corpus callosum (ACC and HCC) are heterogeneous group with a large variation in published prevalence based on few population based studies. The aim of this work is to describe prevalence, associated factors and other malformations present in cases with either agenesis or hypoplasia of the corpus callosum, using a population-based database of all malformations diagnosed in Emilia-Romagna, Italy, (the Emilia-Romagna Registry on Congenital Malformations, IMER). This registry links and integrates hospital discharge records, birth certificates with cases reported by referral clinicians to identify all structural malformations diagnosed within one year of life regarding live birth, fetal death or termination of pregnancy due to fetal malformations (TOPFA). During the study period (1981-2015) the number of cases with ACC or HCC was 255, in a reference population of 1,023,784 live births, giving an overall prevalence of 2.49 per 10,000 (1.47 per 10,000 only live birth). After 1996, with the inclusion of TOPFA in IMER registry, the overall prevalence rate increase significantly from 1.42 to 3.03 cases per 10,000 birth (p-value<0.001). Prenatal diagnosis was made in 192 cases (75.3%), at a median gestational age of 20.7 [IQR: 19.71-22.71]. Termination of pregnancy occurred in 105 of the 255 cases (41,2%). Where a prenatal diagnosis was available, 55% of cases ended in TOPFA (105/192), with higher prevalence of cases associated to central nervous system malformations and multiple birth defects, and median gestational age at diagnosis significantly less than in live birth cases (20.3 vs 29 weeks). Agenesis/hypoplasia ratio was 5.7 (217/38). The most frequently associated malformations were musculoskeletal. Trisomies were the most frequent chromosomal anomalies, in particularly trisomy18 and 13 (respectively 9/32 and 4/32 cases). Our study showed an increased risk for male infants (RR of 1.68, RR 95% CI 1.19-2.37). No differences were detected analyzing maternal age and ethnicity, and the increased risk associated to preterm birth disappeared when compared with other malformed infants. This is one of the few population based studies dealing with prevalence of agenesis and hypoplasia of corpus callosum. Prevalence is still debated, but this study adds comprehensive data, in particular inclusion of TOPFA cases. Early prenatal diagnosis, not always possible, could be crucial for decision making regarding continuation of pregnancy.

A novel 2q37 microdeletion containing human neural progenitors genes including STK25 results in severe developmental delay, epilepsy, and microcephaly.

2q37 microdeletion syndrome is a rare syndrome characterized by neurodevelopmental delay, bone, cardiovascular, and neurological alterations. This syndrome is typically associated with loss of genetic material of approximately 100 genes in the 2q37 band. However, the genes associated with neurodevelopmental phenotype in this syndrome are still unknown. We identified a deleted region of 496 kb by whole genome array CGH in a patient who fulfilled criteria for 2q37 microdeletion syndrome with developmental delay, microcephaly, hypoplasia of the corpus callosum, hand wringing, toe walking, and seizures. The deleted segment contains genes that are highly expressed in the developing human cortical plate and the subventricular zone (SVZ) in vivo and human neural progenitors in vitro, including SEPT2, THAP4, ATG4B, PPP1R7, and STK25. Network analysis revealed that STK25 was the most interacting gene associated with neural development in this deletion. Our report narrows the likely causative genomic region for microcephaly and neurodevelopmental delay in 2q37 microdeletion syndrome to a small genomic region enriched with neural progenitor genes that may represent an important locus for the development of the human cortex and corpus callosum.