De novo start-loss variant in HIRA in patient with DiGeorge-like syndrome

A case of a newborn with tetralogy of Fallot, corpus callosum hypoplasia, and phenotypic features similar to DiGeorge syndrome. Chromosomal microarray analysis did not reveal any alterations. Whole exome sequencing and Sanger sequencing identified a de novo variant in the HIRA gene resulting in the loss of the start codon.

Diagnostic yield of exome sequencing in prenatal agenesis of corpus callosum: systematic review and meta-analysis

OBJECTIVES

To determine the incremental diagnostic yield of exome sequencing (ES) after negative chromosomal microarray analysis (CMA) in cases of prenatally diagnosed agenesis of the corpus callosum (ACC) and to identify the associated genes and variants.

METHODS

A systematic search was performed to identify relevant studies published up until June 2022 using four databases: PubMed, SCOPUS, Web of Science and The Cochrane Library. Studies in English reporting on the diagnostic yield of ES following negative CMA in prenatally diagnosed partial or complete ACC were included. Authors of cohort studies were contacted for individual participant data and extended cohorts were provided for two of them. The increase in diagnostic yield with ES for pathogenic/likely pathogenic (P/LP) variants was assessed in all cases of ACC, isolated ACC, ACC with other cranial anomalies and ACC with extracranial anomalies. To identify all reported genetic variants, the systematic review included all ACC cases; however, for the meta-analysis, only studies with ≥ three ACC cases were included. Meta-analysis of proportions was employed using a random-effects model. Quality assessment of the included studies was performed using modified Standards for Reporting of Diagnostic Accuracy criteria.

RESULTS

A total of 28 studies, encompassing 288 prenatally diagnosed ACC cases that underwent ES following negative CMA, met the inclusion criteria of the systematic review. We classified 116 genetic variants in 83 genes associated with prenatal ACC with a full phenotypic description. There were 15 studies, encompassing 268 cases, that reported on ≥ three ACC cases and were included in the meta-analysis. Of all the included cases, 43% had a P/LP variant on ES. The highest yield was for ACC with extracranial anomalies (55% (95% CI, 35-73%)), followed by ACC with other cranial anomalies (43% (95% CI, 30-57%)) and isolated ACC (32% (95% CI, 18-51%)).

CONCLUSIONS

ES demonstrated an incremental diagnostic yield in cases of prenatally diagnosed ACC following negative CMA. While the greatest diagnostic yield was observed in ACC with extracranial anomalies and ACC with other central nervous system anomalies, ES should also be considered in cases of isolated ACC. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

A de novo pathogenic variant in DHX30 gene in a fetus with isolated dysgenesis of the corpus callosum

A 36 years old woman in her first pregnancy was referred at 24w3d for a dedicated neurosonographic examination due to a suspected short corpus callosum (CC). The examination depicted a dysgenetic CC with asymmetric thickness at the level of the body in coronal views, very thin in the midline and thicker in both sides, suggesting bilateral formation of Probst bundles. The BPD, HC, and transverse cerebellar diameters were in the normal low range without associated growth restriction. Associated anomalies were not detected in the brain or other organs. Following genetic consultation and a normal CMA, trio exome sequencing was performed and a de novo missense pathogenic mutation c.2353 C > T in the DHX30 gene was detected. This variant has been previously reported in children and adults, mostly with a severe phenotype including neurodevelopmental disorder with variable motor and language impairment, but also mild phenotypes have been reported. MRI describes delayed myelination, ventriculomegaly, and cortical and cerebellar atrophy as imaging features in affected patients. This is the first prenatal report of a DHX30-associated neurodevelopmental disorder in which the fetus presents with isolated callosal dysgenesis, stressing the importance of exome sequencing in fetuses with this condition, as far as it is phenotypic presentation of numerous syndromes with different outcomes.

Loss-of-function variants in ZEB1 cause dominant anomalies of the corpus callosum with favourable cognitive prognosis

BACKGROUND

The neurodevelopmental prognosis of anomalies of the corpus callosum (ACC), one of the most frequent brain malformations, varies extremely, ranging from normal development to profound intellectual disability (ID). Numerous genes are known to cause syndromic ACC with ID, whereas the genetics of ACC without ID remains poorly deciphered.

METHODS

Through a collaborative work, we describe here ZEB1, a gene previously involved in an ophthalmological condition called type 3 posterior polymorphous corneal dystrophy, as a new dominant gene of ACC. We report a series of nine individuals with ACC (including three fetuses terminated due to ACC) carrying a ZEB1 heterozygous loss-of-function (LoF) variant, identified by exome sequencing.

RESULTS

In five cases, the variant was inherited from a parent with a normal corpus callosum, which illustrates the incomplete penetrance of ACC in individuals with an LoF in ZEB1. All patients reported normal schooling and none of them had ID. Neuropsychological assessment in six patients showed either normal functioning or heterogeneous cognition. Moreover, two patients had a bicornuate uterus, three had a cardiovascular anomaly and four had macrocephaly at birth, which suggests a larger spectrum of malformations related to ZEB1.

CONCLUSION

This study shows ZEB1 LoF variants cause dominantly inherited ACC without ID and extends the extraocular phenotype related to this gene.

Prenatal Diagnosis of Primrose Syndrome

Primrose syndrome is a very rare congenital malformation. Symptoms of this disorder may appear during childhood, but the diagnosis is identified in adulthood in the majority of cases. The prenatal diagnosis of Primrose syndrome is not developed in the literature. We present herein a case series of 3 cases with characteristic sonographic features. A dysmorphic metopic suture, downslanting palpebral fissures, a wide forehead, and agenesis of corpus callosum are the main signs. A missense mutation in ZBTB20 identified in whole exome sequencing can confirm the prenatal diagnosis of Primrose syndrome.

Further characterisation of ARX-related disorders in females due to inherited or de novo variants

The Aristaless-related homeobox (ARX) gene is located on the X chromosome and encodes a transcription factor that is essential for brain development. While the clinical spectrum of ARX-related disorders is well described in males, from X linked lissencephaly with abnormal genitalia syndrome to syndromic and non-syndromic intellectual disability (ID), its phenotypic delineation in females is incomplete. Carrier females in ARX families are usually asymptomatic, but ID has been reported in some of them, as well as in others with de novo variants. In this study, we collected the clinical and molecular data of 10 unpublished female patients with de novo ARX pathogenic variants and reviewed the data of 63 females from the literature with either de novo variants (n=10), inherited variants (n=33) or variants of unknown inheritance (n=20). Altogether, the clinical spectrum of females with heterozygous pathogenic ARX variants is broad: 42.5% are asymptomatic, 16.4% have isolated agenesis of the corpus callosum (ACC) or mild symptoms (learning disabilities, autism spectrum disorder, drug-responsive epilepsy) without ID, whereas 41% present with a severe phenotype (ie, ID or developmental and epileptic encephalopathy (DEE)). The ID/DEE phenotype was significantly more prevalent in females carrying de novo variants (75%, n=15/20) versus in those carrying inherited variants (27.3%, n=9/33). ACC was observed in 66.7% (n=24/36) of females who underwent a brain MRI. By refining the clinical spectrum of females carrying ARX pathogenic variants, we show that ID is a frequent sign in females with this X linked condition.

Agenesis of the corpus callosum: What to tell expecting parents?

Agenesis of the corpus callosum (ACC) is one of the most common brain malformations, with an incidence estimated to range from 0.5 to 70 in 10,000 among the general population. Prenatal diagnosis is made via ultrasound; however, fetal MRI is useful to confirm or exclude the presence of associated cerebral abnormalities-mostly cortical malformations-that may affect postnatal prognosis. When no additional central nervous system (CNS) or extra CNS anomalies are identified and no genetic cause is found, an isolated ACC is diagnosed. Overall, in cases of ACC, an underlying genetic cause can be identified in up to 12.5% with chromosomal microarray (CMA) and up to 47% with whole exome sequencing (WES). In cases where ACC is the only anomaly detected, the yield of WES is 30%. Postnatal outcomes are variable and depend on whether the condition is isolated or not. In truly isolated ACC, outcomes range from normal in 65% of cases through mild to severe neurodevelopmental impairments in 35% of cases. An interdisciplinary team of medical experts is key in guiding parents toward informed decision-making in pregnancies complicated by ACC. Considering current and expected advancements in genetic testing and imaging technologies in upcoming years, we herein summarize current recommendations for the management and prenatal counseling of expecting parents of fetuses with ACC. Our review pertains primarily to expecting parents of fetuses with complete ACC.

Abnormalities of the corpus callosum. Can prenatal imaging predict the genetic status? Correlations between imaging phenotype and genotype

OBJECTIVE

Recent studies have evaluated prenatal exome sequencing (pES) for abnormalities of the corpus callosum (CC). The objective of this study was to compare imaging phenotype and genotype findings.

METHOD

This multicenter retrospective study included fetuses with abnormalities of the CC between 2018 and 2020 by ultrasound and/or MRI and for which pES was performed. Abnormalities of the CC were classified as complete (cACC) or partial (pACC) agenesis of the CC, short CC (sCC), callosal dysgenesis (CD), interhemispheric cyst (IHC), or pericallosal lipoma (PL), isolated or not. Only pathogenic (class 5) or likely pathogenic (class 4) (P/LP) variants were considered.

RESULTS

113 fetuses were included. pES identified P/LP variants for 3/29 isolated cACC, 3/19 isolated pACC, 0/10 isolated sCC, 5/10 isolated CD, 5/13 non-isolated cACC, 3/6 non-isolated pACC, 8/11 non-isolated CD and 0/12 isolated IHC and PL. Associated cerebellar abnormalities were significantly associated with P/LP variants (OR = 7.312, p = 0.027). No correlation was found between phenotype and genotype, except for fetuses with a tubulinopathy and an MTOR pathogenic variant.

CONCLUSIONS

P/LP variants were more frequent in CD and in non-isolated abnormalities of the CC. No such variants were detected for fetuses with isolated sCC, IHC and PL.

Loss-of-function variants in MYCBP2 cause neurobehavioural phenotypes and corpus callosum defects

The corpus callosum is a bundle of axon fibres that connects the two hemispheres of the brain. Neurodevelopmental disorders that feature dysgenesis of the corpus callosum as a core phenotype offer a valuable window into pathology derived from abnormal axon development. Here, we describe a cohort of eight patients with a neurodevelopmental disorder characterized by a range of deficits including corpus callosum abnormalities, developmental delay, intellectual disability, epilepsy and autistic features. Each patient harboured a distinct de novo variant in MYCBP2, a gene encoding an atypical really interesting new gene (RING) ubiquitin ligase and signalling hub with evolutionarily conserved functions in axon development. We used CRISPR/Cas9 gene editing to introduce disease-associated variants into conserved residues in the Caenorhabditis elegans MYCBP2 orthologue, RPM-1, and evaluated functional outcomes in vivo. Consistent with variable phenotypes in patients with MYCBP2 variants, C. elegans carrying the corresponding human mutations in rpm-1 displayed axonal and behavioural abnormalities including altered habituation. Furthermore, abnormal axonal accumulation of the autophagy marker LGG-1/LC3 occurred in variants that affect RPM-1 ubiquitin ligase activity. Functional genetic outcomes from anatomical, cell biological and behavioural readouts indicate that MYCBP2 variants are likely to result in loss of function. Collectively, our results from multiple human patients and CRISPR gene editing with an in vivo animal model support a direct link between MYCBP2 and a human neurodevelopmental spectrum disorder that we term, MYCBP2-related developmental delay with corpus callosum defects (MDCD).

Long-term outcome of consecutive case series of congenital isolated agenesis of corpus callosum

OBJECTIVE

To describe the long-term outcome of children with prenatally diagnosed isolated complete agenesis of the corpus callosum (cACC).

METHODS

In this single-center case series, we reviewed retrospectively the charts of fetuses referred to our fetal therapy unit from January 2004 to July 2020 for a suspected anomaly of the corpus callosum (CC). Cases with prenatally diagnosed isolated cACC were included. Fetal karyotype and comparative genomic hybridization microarray of amniotic fluid, in addition to fetal magnetic resonance imaging, were offered to all pregnant women with a diagnosis of fetal CC malformation. The surviving children were enrolled in the neurodevelopmental follow-up program at our institution, which included postnatal magnetic resonance imaging, serial neurological examinations and neurodevelopmental evaluations with standardized tests according to age. Families living in remote areas or far from our institution were offered a structured ad-hoc phone interview.

RESULTS

A total of 128 pregnancies with fetal CC malformation were identified (mean gestational age at diagnosis, 24.5 (range, 21-34) weeks), of which 53 cases were diagnosed prenatally with apparently isolated cACC. Of these, 12 cases underwent termination of pregnancy, one resulted in intrauterine demise at 24 weeks of gestation and 13 cases were lost to follow-up. Of the remaining 27 children, one was excluded due to an associated chromosomal anomaly (8p21.3q11.21 mosaic duplication) diagnosed after birth, which could have been detected prenatally if the parents had consented to amniocentesis. In the 26 children included in the analysis, neurodevelopmental follow-up was available for a median of 3 (range, 1-16) years. Three (11.5%) infants had severe neurodevelopmental impairment, two of which were diagnosed postnatally with a genetic syndrome (Mowat-Wilson syndrome and Vici syndrome) that would not have been diagnosed prenatally. Seven (26.9%) children had mild neurodevelopmental impairment and 16 (61.5%) had normal neurodevelopmental outcome. The Full-Scale Intelligence Quotients of the three children with severe neurodevelopmental impairment were 50, 64 and 63, respectively, while that of the remaining children was in the normal range (median, 101; range, 89-119).

CONCLUSIONS

In 88% of the children with cACC included in this study, neurodevelopment was not severely impaired. However, long-term follow-up is recommended in all cases of congenital isolated cACC to recognize subtle neurodevelopmental disorders as early as possible. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Expanding the phenotype of HNRNPU-related neurodevelopmental disorder with emphasis on seizure phenotype and review of literature

Pathogenic variants in heterogeneous nuclear ribonucleoprotein U (HNRNPU) results in a novel neurodevelopmental disorder recently delineated. Here, we report on 17 previously unpublished patients carrying HNRNPU pathogenic variants. All patients were found to harbor de novo loss-of-function variants except for one individual where the inheritance could not be determined, as a parent was unavailable for testing. All patients had seizures which started in early childhood, global developmental delay, intellectual disability, and dysmorphic features. In addition, hypotonia, behavioral abnormalities (such as autistic features, aggression, anxiety, and obsessive-compulsive behaviors), and cardiac (septal defects) and/or brain abnormalities (ventriculomegaly and corpus callosum thinning/agenesis) were frequently observed. We have noted four recurrent variants in the literature (c.1089G>A p.(Trp363*), c.706_707del p.(Glu236Thrfs*6), c.847_857del p.(Phe283Serfs*5), and c.1681dels p.(Gln561Serfs*45)).

Cubilin-, megalin-, and Dab2-dependent transcription revealed by CRISPR/Cas9 knockout in kidney proximal tubule cells

The multiligand receptors megalin (Lrp2) and cubilin (Cubn) and their endocytic adaptor protein Dab2 (Dab2) play essential roles in maintaining the integrity of the apical endocytic pathway of proximal tubule (PT) cells and have complex and poorly understood roles in the development of chronic kidney disease. Here, we used RNA-sequencing and CRISPR/Cas9 knockout (KO) technology in a well-differentiated cell culture model to identify PT-specific transcriptional changes that are directly consequent to the loss of megalin, cubilin, or Dab2 expression. KO of Lrp2 had the greatest transcriptional effect, and nearly all genes whose expression was affected in Cubn KO and Dab2 KO cells were also changed in Lrp2 KO cells. Pathway analysis and more granular inspection of the altered gene profiles suggested changes in pathways with immunomodulatory functions that might trigger the pathological changes observed in KO mice and patients with Donnai-Barrow syndrome. In addition, differences in transcription patterns between Lrp2 and Dab2 KO cells suggested the possibility that altered spatial signaling by aberrantly localized receptors contributes to transcriptional changes upon the disruption of PT endocytic function. A reduction in transcripts encoding sodium-glucose cotransporter isoform 2 was confirmed in Lrp2 KO mouse kidney lysates by quantitative PCR analysis. Our results highlight the role of megalin as a master regulator and coordinator of ion transport, metabolism, and endocytosis in the PT. Compared with the studies in animal models, this approach provides a means to identify PT-specific transcriptional changes that are directly consequent to the loss of these target genes.NEW & NOTEWORTHY Megalin and cubilin receptors together with their adaptor protein Dab2 represent major components of the endocytic machinery responsible for efficient uptake of filtered proteins by the proximal tubule (PT). Dab2 and megalin expression have been implicated as both positive and negative modulators of kidney disease. We used RNA sequencing to knock out CRISPR/Cas9 cubilin, megalin, and Dab2 in highly differentiated PT cells to identify PT-specific changes that are directly consequent to knockout of each component.

C12orf57 pathogenic variants: a unique cause of developmental encephalopathy in a south Indian child

Open reading frame variants which lack stop codons such as C12orf57 variants are known to cause Temtamy syndrome, an extremely rare disorder characterized by intellectual disability, seizures, facial dysmorphism and agenesis of corpus callosum. C12orf57 was initially reported to be required for human corpus callosum development. We report the first child who is of Indian origin with developmental and epileptic encephalopathy (DEE) with a unique phenotypic evolution as focal onset reflex seizures. We performed whole exome sequencing of genomic DNA isolated from peripheral blood samples of proband and his parents. Two pathogenic compound heterozygous variants, a start loss variant (Chr12:7053285:c.1A>G) and a premature stop gain variant (Chr12:7053327:c.43C>T), involving the C12orf57 gene were identified in the proband. Our case report which details genotyping in this rare syndromic developmental encephalopathy, with no prior cases reported from India, expands the ethnic spectrum of patients.

Uncertain, Not Unimportant: Callosal Dysgenesis and Variants of Uncertain Significance in ROBO1

Congenital anomalies affect 3% to 5% of births and remain the leading cause of infant death in the United States. As whole exome and genome sequencing are increasingly used to diagnose underlying genetic disease, the patient's clinical presentation remains the most important context for interpreting sequencing results, including frequently reported variants of uncertain significance (VUS). Classification of a variant as VUS acknowledges limits on evidence to establish whether a variant can be classified as pathogenic or benign according to the American College of Medical Genetics guidelines. Importantly, the VUS designation reflects limits on the breadth of evidence linking the genetic variant to a disease. However, available evidence, although limited, may be surprisingly relevant in an individual patient's case. Accordingly, a VUS result should be approached neither as nondiagnostic genetic result nor as automatically "uncertain" in its potential to guide clinical decision-making. In this article, we discuss a case of an infant born at 29 weeks 4 days without a corpus callosum, whose whole genome sequencing yielded compound heterozygous variants both classified as VUS in ROBO1, a gene encoding for a receptor involved in a canonical signaling mechanism that guides axons across midline. Approaching the VUS result as potentially pathogenic, we found the infant ultimately had pituitary dysfunction and renal anomalies consistent with other reported ROBO1 variants and basic science literature. Accordingly, we highlight resources for variant interpretation available to clinicians to evaluate VUS results, particularly as they inform the diagnosis of individually rare but collectively common rare diseases.

Missense variants in DPYSL5 cause a neurodevelopmental disorder with corpus callosum agenesis and cerebellar abnormalities

The collapsin response mediator protein (CRMP) family proteins are intracellular mediators of neurotrophic factors regulating neurite structure/spine formation and are essential for dendrite patterning and directional axonal pathfinding during brain developmental processes. Among this family, CRMP5/DPYSL5 plays a significant role in neuronal migration, axonal guidance, dendrite outgrowth, and synapse formation by interacting with microtubules. Here, we report the identification of missense mutations in DPYSL5 in nine individuals with brain malformations, including corpus callosum agenesis and/or posterior fossa abnormalities, associated with variable degrees of intellectual disability. A recurrent de novo p.Glu41Lys variant was found in eight unrelated patients, and a p.Gly47Arg variant was identified in one individual from the first family reported with Ritscher-Schinzel syndrome. Functional analyses of the two missense mutations revealed impaired dendritic outgrowth processes in young developing hippocampal primary neuronal cultures. We further demonstrated that these mutations, both located in the same loop on the surface of DPYSL5 monomers and oligomers, reduced the interaction of DPYSL5 with neuronal cytoskeleton-associated proteins MAP2 and βIII-tubulin. Our findings collectively indicate that the p.Glu41Lys and p.Gly47Arg variants impair DPYSL5 function on dendritic outgrowth regulation by preventing the formation of the ternary complex with MAP2 and βIII-tubulin, ultimately leading to abnormal brain development. This study adds DPYSL5 to the list of genes implicated in brain malformation and in neurodevelopmental disorders.

Temporal manipulation of KCC3 expression in juvenile or adult mice suggests irreversible developmental deficit in hereditary motor sensory neuropathy with agenesis of the corpus callosum

Hereditary motor sensory neuropathy (HMSN/ACC) with agenesis of the corpus callosum (ACC) has been documented in the French-derived populations of Charlevoix and Saguenay/Lac St. Jean in Quebec, Canada, as well as a few sporadic families throughout the world. HMSN/ACC occurs because of loss-of-function mutations in the potassium-chloride cotransporter 3 (KCC3). In HMSN/ACC, motor deficits occur early in infancy with rapid and continual deterioration of motor and sensory fibers into juvenile and adulthood. Genetic work in mice has demonstrated that the disease is caused by loss of KCC3 function in neurons and particularly parvalbumin (PV)-expressing neurons. Currently, there are no treatments or cures for HMSN/ACC other than pain management. As genetic counseling in Quebec has increased as a preventative strategy, most individuals with HSMN/ACC are now adults. The onset of the disease is unknown. In particular, it is unknown if the disease starts early during development and whether it can be reversed by restoring KCC3 function. In this study, we used two separate mouse models that when combined to the PV-CreERT2 tamoxifen-inducible system allowed us to 1) disrupt KCC3 expression in adulthood or juvenile periods; and 2) reintroduce KCC3 expression in mice that first develop with a nonfunctional cotransporter. We show that disrupting or reintroducing KCC3 in the adult mouse has no effect on locomotor behavior, indicating that expression of KCC3 is critical during embryonic development and/or the perinatal period and that once the disease has started, reexpressing a functional cotransporter fails to change the course of HMSN/ACC.

MED12-Related (Neuro)Developmental Disorders: A Question of Causality

MED12 is a member of the Mediator complex that is involved in the regulation of transcription. Missense variants in MED12 cause FG syndrome, Lujan-Fryns syndrome, and Ohdo syndrome, as well as non-syndromic intellectual disability (ID) in hemizygous males. Recently, female patients with de novo missense variants and de novo protein truncating variants in MED12 were described, resulting in a clinical spectrum centered around ID and Hardikar syndrome without ID. The missense variants are found throughout MED12, whether they are inherited in hemizygous males or de novo in females. They can result in syndromic or nonsyndromic ID. The de novo nonsense variants resulting in Hardikar syndrome that is characterized by facial clefting, pigmentary retinopathy, biliary anomalies, and intestinal malrotation, are found more N-terminally, whereas the more C-terminally positioned variants are de novo protein truncating variants that cause a severe, syndromic phenotype consisting of ID, facial dysmorphism, short stature, skeletal abnormalities, feeding difficulties, and variable other abnormalities. This broad range of distinct phenotypes calls for a method to distinguish between pathogenic and non-pathogenic variants in MED12. We propose an isogenic iNeuron model to establish the unique gene expression patterns that are associated with the specific MED12 variants. The discovery of these patterns would help in future diagnostics and determine the causality of the MED12 variants.

DCC regulates astroglial development essential for telencephalic morphogenesis and corpus callosum formation

The forebrain hemispheres are predominantly separated during embryogenesis by the interhemispheric fissure (IHF). Radial astroglia remodel the IHF to form a continuous substrate between the hemispheres for midline crossing of the corpus callosum (CC) and hippocampal commissure (HC). Deleted in colorectal carcinoma (DCC) and netrin 1 (NTN1) are molecules that have an evolutionarily conserved function in commissural axon guidance. The CC and HC are absent in Dcc and Ntn1 knockout mice, while other commissures are only partially affected, suggesting an additional aetiology in forebrain commissure formation. Here, we find that these molecules play a critical role in regulating astroglial development and IHF remodelling during CC and HC formation. Human subjects with DCC mutations display disrupted IHF remodelling associated with CC and HC malformations. Thus, axon guidance molecules such as DCC and NTN1 first regulate the formation of a midline substrate for dorsal commissures prior to their role in regulating axonal growth and guidance across it.

Clinical presentation and evolution of Xia-Gibbs syndrome due to p.Gly375ArgfsTer3 variant in a patient from DR Congo (Central Africa)

Xia-Gibbs syndrome (XGS) is a very rare genetic condition. The clinical spectrum is very broad and variable. The phenotype and evolution in a Congolese boy with XGS have been reported. At 6 years he had speech delay, drooling, marked hyperactivity, attention deficit, aggressive behavior, and intellectual disability. Dysmorphological evaluation revealed strabismus, mild unilateral ptosis, uplifted ear lobes, flat philtrum, thin upper lip vermillion, high arched palate, and flat feet. Patient-only whole exome sequencing identified a known pathogenic frameshift variant in the AHDC1 gene [NM_001029882.3(AHDC1):c.1122dupC;(p.Gly375ArgfsTer3)]. The clinical follow-up revealed the deterioration of his fine motor skills and significant cerebellar phenotype including tremor, pes cavus, and gait instability at the age of 12 years. This patient was compared with three previously reported patients with the same variant but did not identify a consistent pattern in the evolution of symptoms with age.

Prenatal diagnosis of partial monosomy 21q (21q22.1→qter) associated with intrauterine growth restriction and corpus callosum dysgenesis

OBJECTIVE

A prenatal diagnosis of partial monosomy 21q(21q22.1→ qter) in fetus with intrauterine growth restriction and corpus callosum dysgenesis but escaped from the detection by cell free DNA testing was reported.

CASE REPORT

A 31-year-old, primigravida women, presented with intrauterine growth restriction and corpus callosum dysgenesis at 23 weeks of gestational age by anatomic ultrasound screening. The interphase fluorescence in situ hybridization (FISH) analysis on amniocytes revealed monosomy 21, while the cytogenetic analysis and array comparative genomic hybridization (CGH) with CytoScan gene chip ascertained a 12.35 Mb deletion at 21q22.1q22.3.

CONCLUSION

Although noninvasive prenatal testing is used extensively and can be applied to certain microdeletion diseases, the application for uncommon deletion disorders such as the present case remains limited. Prenatal examination with detailed ultra-sonography combined with different modalities of invasive prenatal testing can provide a more comprehensive information.

Vici syndrome with pathogenic homozygous EPG5 gene mutation: A case report and literature review

RATIONALE

Vici syndrome (VICIS) is a rare, autosomal recessive neurodevelopmental disorder with multisystem involvement characterized by agenesis of the corpus callosum, congenital cataracts, cardiomyopathy, combined immunodeficiency, significant developmental delay, and hypopigmentation and in some cases loss of hearing. It is caused by mutations in Ectopic P-granules protein 5 gene, which is responsible for regulating autophagy activity.

PATIENT CONCERN

We report a 6-month-old Saudi female patient who was the second-born baby of first cousins. She was born by normal spontaneous vertex vaginal delivery. Parents noticed that she had global developmental delay and recurrent hospital admissions due to chest infections.

DIAGNOSIS

Brain magnetic resonance imaging showed brain atrophy with corpus callosum agenesis. Ophthalmology examination revealed bilateral congenital cataract. Molecular genetic testing identified the pathogenic homozygous variant c.4751T>A p. (Leu1584*) on exon 27 of the EPG5 gene and confirmed the diagnosis of Vici syndrome.

INTERVENTIONS

Supportive multidisciplinary care plan was initiated to this untreatable syndrome.

OUTCOMES

The patient died at the age of 6 months due to sepsis with uncompensated septic shock.

LESSONS

VICIS is a rare untreatable disorder with worldwide distribution. High index of suspicion is needed to diagnose it and family genetic counselling is crucial.

Novel insights into the clinical and molecular spectrum of congenital disorders of autophagy

Autophagy is a fundamental and conserved catabolic pathway that mediates the degradation of macromolecules and organelles in lysosomes. Autophagy is particularly important to postmitotic and metabolically active cells such as neurons. The complex architecture of neurons and their long axons pose additional challenges for efficient recycling of cargo. Not surprisingly autophagy is required for normal central nervous system development and function. Several single-gene disorders of the autophagy pathway have been discovered in recent years giving rise to a novel group of inborn errors of metabolism referred to as congenital disorders of autophagy. While these disorders are heterogeneous, they share several clinical and molecular characteristics including a prominent and progressive involvement of the central nervous system leading to brain malformations, developmental delay, intellectual disability, epilepsy, movement disorders, and cognitive decline. On brain magnetic resonance imaging a predominant involvement of the corpus callosum, the corticospinal tracts and the cerebellum are noted. A storage disease phenotype is present in some diseases, underscoring both clinical and molecular overlaps to lysosomal storage diseases. This review provides an update on the clinical, imaging, and genetic spectrum of congenital disorders of autophagy and highlights the importance of this pathway for neurometabolism and childhood-onset neurological diseases.

The Clinical and Molecular Characteristics of Molybdenum Cofactor Deficiency Due to MOCS2 Mutations

BACKGROUND

We explored the clinical and molecular characteristics of molybdenum cofactor deficiency due to MOCS2 muations.

METHODS

We summarize the genetic and clinical findings of previously reported patients with a MOCS2 mutation. We also present a new patient with novel neuroradiological findings associated with molybdenum cofactor deficiency due to a novel homozygous variant in the 5' untranslated region of the MOCS2 gene.

RESULTS

The study population comprised 35 patients with a MOCS2 gene mutation. All reported children had delayed motor milestones. The major initial symptom was seizures in neonatal period. Facial dysmorphism was present in 61% of the patients. Only one patient had ectopia lentis. Agenesis of the corpus callosum and an associated interhemispheric cyst in our case are novel neuroradiological findings.

CONCLUSIONS

The occurrence of neonatal seizures and feeding difficulties can be the first clinical signs of molybdenum cofactor deficiency. Although there is no effective therapy for this condition, early diagnosis and genetic analysis of these lethal disorders facilitate adequate genetic counseling.

Vici Syndrome with a Novel Mutation in EPG5

BACKGROUND

Vici syndrome is a neurodevelopmental disorder of the autophagy pathway. Almost all cases reported have the cardinal features of agenesis of corpus callosum, cataract, cardiomyopathy, immunodeficiency and hypopigmentation.

CASE CHARACTERISTICS

8-month-old boy with developmental delay, myoclonic jerks, repeated respiratory infections, coarse facial features, cataract and hypopigmented hair. Echocardiography revealed dilated cardiomyopathy and magnetic resonance imaging of brain suggested agenesis of corpus callosum. Exome sequencing detected a novel homozygous nonsense mutation in the EPG5 gene.

OUTCOME

Establishing a definite diagnosis helped in proper prognostication, providing genetic counseling and prenatal diagnosis to the family.

MESSAGE

Though uncommon, presence of the characteristic features makes Vici syndrome a clinically recognizable cause of developmental delay.

Mutations in MAST1 Cause Mega-Corpus-Callosum Syndrome with Cerebellar Hypoplasia and Cortical Malformations

Corpus callosum malformations are associated with a broad range of neurodevelopmental diseases. We report that de novo mutations in MAST1 cause mega-corpus-callosum syndrome with cerebellar hypoplasia and cortical malformations (MCC-CH-CM) in the absence of megalencephaly. We show that MAST1 is a microtubule-associated protein that is predominantly expressed in post-mitotic neurons and is present in both dendritic and axonal compartments. We further show that Mast1 null animals are phenotypically normal, whereas the deletion of a single amino acid (L278del) recapitulates the distinct neurological phenotype observed in patients. In animals harboring Mast1 microdeletions, we find that the PI3K/AKT3/mTOR pathway is unperturbed, whereas Mast2 and Mast3 levels are diminished, indicative of a dominant-negative mode of action. Finally, we report that de novo MAST1 substitutions are present in patients with autism and microcephaly, raising the prospect that mutations in this gene give rise to a spectrum of neurodevelopmental diseases.

Novel compound heterozygous EPG5 mutations consisted with a missense mutation and a microduplication in the exon 1 region identified in a Japanese patient with Vici syndrome

Vici syndrome is a rare, autosomal recessive, multisystem disorder, characterized by agenesis of the corpus callosum, cataracts, psychomotor delay, cardiomyopathy, hypopigmentation, and recurrent infections. Mutations in the ectopic P-granules autophagy protein 5 homolog gene (EPG5), which encodes a key autophagy regulator, are responsible for this syndrome. A 3-year-old Japanese girl manifesting similar symptoms to those found in patients with Vici syndrome showed intractable diarrhea, rather than immunodeficiency. Whole exome sequencing identified only a heterozygous variant in EPG5, NM_020964.2(EPG5):c.3389A > C (p.His1130Pro), which was inherited from her mother. Sequencing analyses of the EPG5 messenger RNA showed only an altered nucleotide "C" at position, c.3389, indicating decreased expression of the wild-type allele. Microarray-based comparative genomic hybridization revealed a de novo microduplication in the exon 1 region. Large exon deletions and duplications of EPG5 have never been reported so far. This was considered the cause of the decreased expression of the wild-type allele. In conclusion, we successfully identified novel compound heterozygous mutations in EPG5 in a patient who was clinically considered to have Vici syndrome.

Low-level expression of EPG5 leads to an attenuated Vici syndrome phenotype

Vici syndrome is a multisystem disorder characterized by agenesis of the corpus callosum, oculocutaneous hypopigmentation, cataracts, cardiomyopathy, combined immunodeficiency, failure to thrive, profound developmental delay, and acquired microcephaly. Most individuals are severely affected and have a markedly reduced life span. Here we describe an 8-year-old boy with a history of developmental delay, agenesis of the corpus callosum, failure to thrive, myopathy, and well-controlled epilepsy. He was initially diagnosed with a mitochondrial disorder, based in part upon nonspecific muscle biopsy findings, but mitochondrial DNA mutation analysis revealed no mutations. Whole exome sequencing revealed compound heterozygosity for two EPG5 variants, inherited in trans. One was a known pathogenic mutation in exon 13 (c.2461C > T, p.Arg821X). The second was reported as a variant of unknown significance found within intron 16, six nucleotides before the exon 17 splice acceptor site (c.3099-6C > G). Reverse transcription-polymerase chain reaction of the EPG5 mRNA showed skipping of exon 17-which maintains an open reading frame-in 77% of the transcript, along with 23% expression of wild-type mRNA suggesting that intronic mutations may affect splicing of the EPG5 gene and result in symptoms. However, the expression of 23% wild-type mRNA may result in a significantly attenuated Vici syndrome phenotype.

Tread carefully: A functional variant in the human NADPH oxidase 4 (NOX4) is not disease causing

In this study, we report a paediatric patient with a lethal phenotype of respiratory distress, failure to thrive, pancreatic insufficiency, liver dysfunction, hypertrophic cardiomyopathy, bone marrow suppression, humoral and cellular immune deficiency. To identify the genetic basis of this unusual clinical phenotype and potentially make available the option of future prenatal testing, whole exome sequencing (WES) was used followed by functional studies in a bid to confirm pathogenicity. The WES we identified a homozygous novel variant, AK298328; c.9_10insGAG; p.[Glu3dup], in NOX4 in the proband, and parental heterozygosity for the variant (confirmed by Sanger sequencing). NADPH Oxidase 4 NOX4 (OMIM 605261) encodes an enzyme that functions as the catalytic subunit of the NADPH oxidase complex. NOX4 acts as an oxygen sensor, catalysing the reduction of molecular oxygen, mainly to hydrogen peroxide (H₂O₂). However, although, our functional data including 60% reduction in NOX4 protein levels and a 75% reduction in the production of H₂O₂ in patient fibroblast extracts compared to controls was initially considered to be the likely cause of the phenotype in our patient, the potential contribution of the NOX4 variant as the primary cause of the disease was clearly excluded based on following pieces of evidence. First, Sanger sequencing of other family members revealed that two of the grandparents were also homozygous for the NOX4 variant, one of who has fibromuscular dysplasia. Second, re-evaluation of more recent variant databases revealed a high allele frequency for this variant. Our case highlights the need to re-interrogate bioinformatics resources as they are constantly evolving, and is reminiscent of the short-chain acyl-CoA dehydrogenase deficiency (SCADD) story, where a functional defect in fatty acid oxidation has doubtful clinical ramifications.

Imaging of Congenital Malformations

PURPOSE OF REVIEW

Intracranial congenital malformations are anomalies of brain development caused by genetic and environmental influences. This article discusses common intracranial congenital malformations, presents the associated neuroimaging findings, and discusses how appropriate identification of intracranial anomalies can impact diagnosis and treatment.

RECENT FINDINGS

Advances in neuroimaging techniques and genetic research have led to a better understanding of the pathogenesis of many congenital malformations, adding insight into their clinical relevance and the intricate relationship between critical periods of development, genetic predisposition, and environmental insults. When one malformation is discovered, a high likelihood of more malformations exists. In some instances, the intracranial anomalies will lead to the diagnosis of a particular neurologic syndrome, which may, in turn, lead to modification of a plan of care.

SUMMARY

Knowledge of congenital malformations and their appearance on imaging sequences is essential to improve clinical outcomes and quality of life for patients.

The Vici syndrome protein EPG5 regulates intracellular nucleic acid trafficking linking autophagy to innate and adaptive immunity

Vici syndrome is a human inherited multi-system disorder caused by recessive mutations in EPG5, encoding the EPG5 protein that mediates the fusion of autophagosomes with lysosomes. Immunodeficiency characterized by lack of memory B cells and increased susceptibility to infection is an integral part of the condition, but the role of EPG5 in the immune system remains unknown. Here we show that EPG5 is indispensable for the transport of the TLR9 ligand CpG to the late endosomal-lysosomal compartment, and for TLR9-initiated signaling, a step essential for the survival of human memory B cells and their ultimate differentiation into plasma cells. Moreover, the predicted structure of EPG5 includes a membrane remodeling domain and a karyopherin-like domain, thus explaining its function as a carrier between separate vesicular compartments. Our findings indicate that EPG5, by controlling nucleic acids intracellular trafficking, links macroautophagy/autophagy to innate and adaptive immunity.

The Incidence of Chromosomal Aberrations in Prenatally Diagnosed Isolated Agenesis of the Corpus Callosum

PURPOSE

 To establish the prevalence of chromosomal aberrations in fetuses with an apparently isolated agenesis of the corpus callosum (ACC) on prenatal ultrasound.

MATERIALS & METHODS

 This was a retrospective study of complete isolated ACC at the time of ultrasound evaluation with respect to karyotype information. Within this group, a subgroup with non-malformation minor abnormalities, such as a single umbilical artery (SUA), polyhydramnios or fetal growth restriction (FGR), was investigated.

RESULTS

 Complete ACC was diagnosed in 343 cases. Of them, 143 (41.6 %) were isolated, with 16 fetuses showing additional minor findings. In 76.2 % (109/143) karyotyping was performed. Additional array CGH analysis was performed in 7.7 % (11/143). Chromosomal aberrations were found in 4.6 % (5/109) overall, in 3.1 % (3/98) of those without any additional sonographic findings (all represented mosaic trisomy 8) and in 18.2 % (2/11) of those with minor abnormalities. The prevalence of pathogenic submicroscopic copy number variant (CNV) was 9 % (1/11).

CONCLUSION

 Fetal karyotyping is recommended in ACC, as trisomy 8 mosaicism should be considered despite otherwise unremarkable ultrasound. The role of novel techniques such as array CGH and its implication has to be explored in prospective studies.

A homozygous PIGO mutation associated with severe infantile epileptic encephalopathy and corpus callosum hypoplasia, but normal alkaline phosphatase levels

We describe two sisters from a consanguineous Arab family with global developmental delay, dystrophy, axial hypotonia, epileptic encephalopathy dominated by intractable complex partial seizures that were resistant to various anti-epileptic treatments. Dysmorphic features comprised low set ears, hypertelorism, upslanting palpebral fissures, a broad nasal bridge, and blue sclera with elongated eyelashes. Brain MRI in both children showed a corpus callosum hypoplasia that was evident already in utero and evolving cortical atrophy. Autozygosity mapping in combination with Whole Exome Sequencing revealed a homozygous missense mutation in the PIGO gene [c.765G > A, NM_032634.3] that affected a highly conserved methionine in the alkaline phosphatase-like core domain of the protein [p.(Met255Ile), NP_116023.2]. PIGO encodes the GPI-ethanolamine phosphate transferase 3, which is crucial for the final synthetic step of the glycosylphosphatidylinositol-anchor that attaches many enzymes to their cell surfaces, such as the alkaline phosphatase and granulocyte surface markers. Interestingly, measurement of serum alkaline phosphatase activities in both children was normal or only slightly elevated. Quantification of granulocyte surface antigens CD16/24/59 yielded reduced levels only for CD59. Phenotype analysis of our and other published patients with PIGO mutations reveals a more severe affectation and predominantly neurological presentation in individuals carrying a mutation in the alkaline phosphatase-like core domain thereby hinting towards a genotype-phenotype relation for PIGO gene mutations.

Autopsy findings in EPG5-related Vici syndrome with antenatal onset

Vici syndrome is one of the most extensive inherited human multisystem disorders and due to recessive mutations in EPG5 encoding a key autophagy regulator with a crucial role in autophagosome-lysosome fusion. The condition presents usually early in life, with features of severe global developmental delay, profound failure to thrive, (acquired) microcephaly, callosal agenesis, cataracts, cardiomyopathy, hypopigmentation, and combined immunodeficiency. Clinical course is variable but usually progressive and associated with high mortality. Here, we present a fetus, offspring of consanguineous parents, in whom callosal agenesis and other developmental brain abnormalities were detected on fetal ultrasound scan (US) and subsequent MRI scan in the second trimester. Postmortem examination performed after medically indicated termination of pregnancy confirmed CNS abnormalities and provided additional evidence for skin hypopigmentation, nascent cataracts, and hypertrophic cardiomyopathy. Genetic testing prompted by a suggestive combination of features revealed a homozygous EPG5 mutation (c.5870-1G>A) predicted to cause aberrant splicing of the EPG5 transcript. Our findings expand the phenotypical spectrum of EPG5-related Vici syndrome and suggest that this severe condition may already present in utero. While callosal agenesis is not an uncommon finding in fetal medicine, additional presence of hypopigmentation, cataracts and cardiomyopathy is rare and should prompt EPG5 testing.

Muscle pathology in Vici syndrome-A case study with a novel mutation in EPG5 and a summary of the literature

Vici syndrome is a disorder characterized by myopathy, cardiomyopathy, agenesis of the corpus callosum, immunodeficiency, cataracts, hypopigmentation, microcephaly, gross developmental delay and failure to thrive. It is caused by mutations in EPG5, which encodes a protein involved in the autophagy pathway. Although myopathy is part of the syndrome, few publications have described the muscle pathology. We present a detailed morphological analysis in a boy with Vici syndrome due to a novel homozygous one-base deletion in EPG5 (c.784delA), and we review the histopathological findings from previous reports. Muscle biopsy was performed at three months of age and demonstrated small vacuolated fibers, frequently with internal nuclei, and expressing developmental and fast myosin isoforms. There was an increase in acid phosphatase activity in the small fibers, which also showed LAMP-2 upregulation, glycogen accumulation and contained numerous p62-positive inclusions and some lipid droplets. Electron microscopy demonstrated hypoplastic fibers with massive glycogen accumulation and extensive disorganization of the myofibrils. This study expands the muscle pathological features of Vici syndrome and demonstrates a pattern of vacuolar myopathy with glycogen storage and immature, hypoplastic and atrophic muscle fibers. Increased lysosomes and accumulation of p62 are in line with a disturbance of the autophagic pathway as an essential part of the pathogenesis.

Defects in autophagosome-lysosome fusion underlie Vici syndrome, a neurodevelopmental disorder with multisystem involvement

Vici syndrome (VICIS) is a rare, autosomal recessive neurodevelopmental disorder with multisystem involvement characterized by agenesis of the corpus callosum, cataracts, cardiomyopathy, combined immunodeficiency, developmental delay, and hypopigmentation. Mutations in EPG5, a gene that encodes a key autophagy regulator, have been shown to cause VICIS, however, the precise pathomechanism underlying VICIS is yet to be clarified. Here, we describe detailed clinical (including brain MRI and muscle biopsy) and genetic features of nine Japanese patients with VICIS. Genetic dissection of these nine patients from seven families identified 14 causative mutations in EPG5. These included five nonsense, two frameshift, three splicing, one missense, and one multi-exon deletion mutations, and two initiation codon variants. Furthermore, cultured skin fibroblasts (SFs) from two affected patients demonstrated partial autophagic dysfunction. To investigate the function of EPG5, siRNA based EPG5 knock-down, and CRISPR/Cas9 mediated EPG5 knock-out HeLa cells were generated. EPG5-depleted cells exhibited a complete block of autophagic flux caused by defective autophagosome-lysosome fusion. Unexpectedly, endocytic degradation was normal in both VICIS SFs and EPG5 depleted cells, suggesting that EPG5 function is limited to the regulation of autophagosome-lysosome fusion.

Copy Number Variations Found in Patients with a Corpus Callosum Abnormality and Intellectual Disability

OBJECTIVE

To evaluate the role that chromosomal micro-rearrangements play in patients with both corpus callosum abnormality and intellectual disability, we analyzed copy number variations (CNVs) in patients with corpus callosum abnormality/intellectual disability STUDY DESIGN: We screened 149 patients with corpus callosum abnormality/intellectual disability using Illumina SNP arrays.

RESULTS

In 20 patients (13%), we have identified at least 1 CNV that likely contributes to corpus callosum abnormality/intellectual disability phenotype. We confirmed that the most common rearrangement in corpus callosum abnormality/intellectual disability is inverted duplication with terminal deletion of the 8p chromosome (3.2%). In addition to the identification of known recurrent CNVs, such as deletions 6qter, 18q21 (including TCF4), 1q43q44, 17p13.3, 14q12, 3q13, 3p26, and 3q26 (including SOX2), our analysis allowed us to refine the 2 known critical regions associated with 8q21.1 deletion and 19p13.1 duplication relevant for corpus callosum abnormality; report a novel 10p12 deletion including ZEB1 recently implicated in corpus callosum abnormality with corneal dystrophy; and) report a novel pathogenic 7q36 duplication encompassing SHH. In addition, 66 variants of unknown significance were identified in 57 patients encompassed candidate genes.

CONCLUSIONS

Our results confirm the relevance of using microarray analysis as first line test in patients with corpus callosum abnormality/intellectual disability.

Heterozygous HNRNPU variants cause early onset epilepsy and severe intellectual disability

Pathogenic variants in genes encoding subunits of the spliceosome are the cause of several human diseases, such as neurodegenerative diseases. The RNA splicing process is facilitated by the spliceosome, a large RNA-protein complex consisting of small nuclear ribonucleoproteins (snRNPs), and many other proteins, such as heterogeneous nuclear ribonucleoproteins (hnRNPs). The HNRNPU gene (OMIM *602869) encodes the heterogeneous nuclear ribonucleoprotein U, which plays a crucial role in mammalian development. HNRNPU is expressed in the fetal brain and adult heart, kidney, liver, brain, and cerebellum. Microdeletions in the 1q44 region encompassing HNRNPU have been described in patients with intellectual disability (ID) and other clinical features, such as seizures, corpus callosum abnormalities (CCA), and microcephaly. Recently, pathogenic HNRNPU variants were identified in large ID and epileptic encephalopathy cohorts. In this study, we provide detailed clinical information of five novels and review two of the previously published individuals with (likely) pathogenic de novo variants in the HNRNPU gene including three non-sense and two missense variants, one small intragenic deletion, and one duplication. The phenotype in individuals with variants in HNRNPU is characterized by early onset seizures (6/7), severe ID (6/6), severe speech impairment (6/6), hypotonia (6/7), and central nervous system (CNS) (5/6), cardiac (4/6), and renal abnormalities (3/4). In this study, we broaden the clinical and mutational HNRNPU-associated spectrum, and demonstrate that heterozygous HNRNPU variants cause epilepsy, severe ID with striking speech impairment and variable CNS, cardiac, and renal anomalies.

Prenatal and postnatal presentations of corpus callosum agenesis with polymicrogyria caused by EGP5 mutation

EPG5-related Vici syndrome is a rare multisystem autosomal recessive disorder characterized by corpus callosum agenesis (ACC), hypopigmentation, cataracts, acquired microcephaly, failure to thrive, cardiomyopathy and profound developmental delay, and immunodeficiency. We report here the first case of prenatally diagnosed Vici syndrome with delayed gyration associated with ACC. Trio based exome sequencing allowed the identification of a compound heterozygous mutation in the EPG5 gene. Our patient subsequently demonstrated severe developmental delay, hypopigmentation, progressive microcephaly, and failure to thrive which led to suspicion of the diagnosis. Her MRI demonstrated ACC with frontoparietal polymicrogyria, severe hypomyelination, and pontocerebellar atrophy. This prenatal presentation of malformations of cortical development in combination with ACC expands the EPG5-related phenotypic spectrum. Our report supports the idea that EPG5-related Vici syndrome is both a neurodevelopmental and neurodegenerative disorder. © 2017 Wiley Periodicals, Inc.

Prenatal Diagnosis of Anomalies of the Corpus Callosum over a 13-Year Period

Purpose: The clinical use of detailed fetal neurosonography has increased over the past decade. This retrospective study explored the spectrum and frequency of different forms of corpus callosum anomalies (CCAs) in a level III center setting. Materials and Methods: Between 1999 and 2012, 48 907 detailed second and third trimester scans were performed. Among them, 140 (0.29 %) cases of CCA were diagnosed. We differentiated between complete and partial agenesis, hypoplastic corpus callosum (CC) and isolated and non-isolated forms. Results: The 140 cases with CCA included 107 with complete agenesis (76 %), 20 with partial agenesis (14 %) and 13 with a hypoplastic CC (9 %). Of them, 29 % (41/140) were isolated and 71 % (99/140) were non-isolated cases. Analysis of three time periods demonstrated an increase in the diagnosis of all types of CCA (1999 - 2004: n = 26; 2005 - 2008: n = 32; 2009 - 2012: n = 82), whereas the ratio between isolated and non-isolated types remained stable. The median gestational age at diagnosis was 25.0 weeks and did not change over the years. Non-isolated forms were associated with additional non-chromosomal cerebral anomalies in 22.2 % (22/99), extracerebral non-chromosomal malformations in 40.4 % (40/99), aneuploidies in 21.2 % (21/99), and syndromes in 16.2 % (16/99). All aneuploid fetuses except one showed cerebral or extracerebral malformations. Conclusion: The rise in prenatal diagnosis of CCA reflects the increased use of systematic fetal neurosonography over the years. Despite an overall increase in diagnosed cases, the relationship between isolated CCAs and complex forms remained stable. Since the percentage of coexisting anomalies is high, a detailed assessment by a specialist is recommended.

The Vici Syndrome Protein EPG5 Is a Rab7 Effector that Determines the Fusion Specificity of Autophagosomes with Late Endosomes/Lysosomes

Mutations in the human autophagy gene EPG5 cause the multisystem disorder Vici syndrome. Here we demonstrated that EPG5 is a Rab7 effector that determines the fusion specificity of autophagosomes with late endosomes/lysosomes. EPG5 is recruited to late endosomes/lysosomes by direct interaction with Rab7 and the late endosomal/lysosomal R-SNARE VAMP7/8. EPG5 also binds to LC3/LGG-1 (mammalian and C. elegans Atg8 homolog, respectively) and to assembled STX17-SNAP29 Qabc SNARE complexes on autophagosomes. EPG5 stabilizes and facilitates the assembly of STX17-SNAP29-VAMP7/8 trans-SNARE complexes, and promotes STX17-SNAP29-VAMP7-mediated fusion of reconstituted proteoliposomes. Loss of EPG5 activity causes abnormal fusion of autophagosomes with various endocytic vesicles, in part due to elevated assembly of STX17-SNAP25-VAMP8 complexes. SNAP25 knockdown partially suppresses the autophagy defect caused by EPG5 depletion. Our study reveals that EPG5 is a Rab7 effector involved in autophagosome maturation, providing insight into the molecular mechanism underlying Vici syndrome.

Depletion of Inositol Polyphosphate 4-Phosphatase II Suppresses Callosal Axon Formation in the Developing Mice

The corpus callosum is a bundle of nerve fibers that connects the two cerebral hemispheres and is essential for coordinated transmission of information between them. Disruption of early stages of callosal development can cause agenesis of the corpus callosum (AgCC), including both complete and partial callosal absence, causing mild to severe cognitive impairment. Despite extensive studies, the etiology of AgCC remains to be clarified due to the complicated mechanism involved in generating AgCC. The biological function of PI3K signaling including phosphatidylinositol-3,4,5-trisphosphate is well established in diverse biochemical processes including axon and dendrite morphogenesis, but the function of the closely related phosphatidylinositol-3,4,-bisphosphate (PI(3,4)P2) signaling, particularly in the nervous system, is largely unknown. Here, we provide the first report on the role of inositol polyphosphate 4-phosphatase II (INPP4B), a PI(3,4)P2 metabolizing 4-phosphatase in the regulation of callosal axon formation. Depleting INPP4B by in utero electroporation suppressed medially directed callosal axon formation. Moreover, depletion of INPP4B significantly attenuated formation of Satb2-positive pyramidal neurons and axon polarization in cortical neurons during cortical development. Taken together, these data suggest that INPP4B plays a role in the regulating callosal axon formation by controlling axon polarization and the Satb2-positive pyramidal neuron population. Dysregulation of INPP4B during cortical development may be implicated in the generation of partial AgCC.

EARS2 mutations cause fatal neonatal lactic acidosis, recurrent hypoglycemia and agenesis of corpus callosum

Mitochondrial aminoacyl tRNA synthetases are essential for organelle protein synthesis. Genetic defects affecting the function of these enzymes may cause pediatric mitochondrial disease. Here, we report on a child with fatal neonatal lactic acidosis and recurrent hypoglycemia caused by mutations in EARS2, encoding mitochondrial glutamyl-tRNA synthetase 2. Brain ultrasound revealed agenesis of corpus callosum. Studies on patient-derived skin fibroblasts showed severely decreased EARS2 protein levels, elevated reactive oxygen species (ROS) production, and altered mitochondrial morphology. Our report further illustrates the clinical spectrum of the severe neonatal-onset form of EARS2 mutations. Moreover, in this case the live-cell parameters appeared to be more sensitive to mitochondrial dysfunction compared to standard diagnostics, which indicates the potential relevance of fibroblast studies in children with mitochondrial diseases.

Two cases of Vici syndrome associated with Idiopathic Thrombocytopenic Purpura (ITP) with a review of the literature

Vici syndrome is a rare congenital disorder first described in 1988. To date, 31 cases have been reported in the literature. The characteristic features of this syndrome include: agenesis of the corpus callosum, albinism, cardiomyopathy, variable immunodeficiency, cataracts, and myopathy. We report two Hispanic sisters with genetically confirmed Vici syndrome who both developed Idiopathic Thrombocytopenic Purpura. To our knowledge, this is an immunologic process that has been previously undescribed within the phenotype of Vici syndrome and should be added to the spectrum of variable immune dysregulation that can be found in these patients.