Search

KIRREL3 is a gene important for the central nervous system development—in particular for the process of neuronal migration, axonal fasciculation, and synaptogenesis—and colocalizes and cooperates in neurons with CASK gene. Alterations of KIRREL3 have been linked to neurodevelopmental disorders, ranging from developmental delay, to autism spectrum disorder, to attention deficit/hyperactivity disorder. The underlying mechanism is not yet fully understood, as it has been hypothesized a fully dominant effect, a risk factor role of KIRREL3 partially penetrating variants, and a recessive inheritance pattern. We report a novel and de novo KIRREL3 mutation in a child affected by severe neurodevelopmental disorder and with brain magnetic resonance imaging evidence of mega cisterna magna and mild cerebellar hypoplasia. This case strengthens the hypothesis that dominant KIRREL3 variants may lead to neurodevelopmental disruption; furthermore, given the strong interaction between KIRREL3 and CASK , we discuss as posterior fossa anomalies may also be part of the phenotype of KIRREL3 -related syndrome. [ABSTRACT FROM AUTHOR]

Featured Application: The study summarizes the clinical and neuropsychological evaluation in children with cerebellar disorder, highlighting the specific characteristics of the child age useful to define a diagnostic pathway. Cerebellar disorders are characterised clinically by specific signs and symptoms, often associated with neurodevelopmental disorder. While the clinical signs of cerebellar disorders are clearly recognisable in adults and have a precise anatomo-functional correlation, in children the semiotics are less clear and vary with age because of the particular nature of the cerebellum's maturation. Unlike other structures of the central nervous system, this begins at a later stage of foetal development and extends over a longer period of time, even after birth. As a result, the typical signs of cerebellar dysfunction will only become evident when the cerebellar functions have become integrated into the complex circuits of the central nervous system. This means that poor motor coordination in the very early years of life may not necessarily correlate with cerebellar dysfunction, and this may also be encountered in healthy children. The cerebellum's role in cognitive and emotional functions relies on its structure and the complexity of its connections. Cognitive and behavioral impairment in cerebellar disorders can be the results of acquired lesions or the action of genetic and environmental risk factors, to which the cerebellum is particularly vulnerable considering its pattern of development. In the pathological setting, early evidence of cerebellar damage may be very vague, due, partly, to spontaneous compensation phenomena and the vicarious role of the connecting structures (an expression of the brain's plasticity). Careful clinical assessment will nonetheless enable appropriate instrumental procedures to be arranged. It is common knowledge that the contribution of neuroimaging is crucial for diagnosis of cerebellar conditions, and neurophysiological investigations can also have a significant role. The ultimate goal of clinicians is to combine clinical data and instrumental findings to formulate a precise diagnostic hypothesis, and thus request a specific genetic test in order to confirm their findings, wherever possible. [ABSTRACT FROM AUTHOR]

Microarray-based comparative genomic hybridization is a method of molecular analysis that identifies chromosomal anomalies (or copy number variants) that correlate with clinical phenotypes. The aim of the present study was to apply a clinical score previously designated by de Vries to 329 patients with intellectual disability/developmental disorder (intellectual disability/developmental delay) referred to our tertiary center and to see whether the clinical factors are associated with a positive outcome of aCGH analyses. Another goal was to test the association between a positive microarray-based comparative genomic hybridization result and the severity of intellectual disability/developmental delay. Microarray-based comparative genomic hybridization identified structural chromosomal alterations responsible for the intellectual disability/developmental delay phenotype in 16% of our sample. Our study showed that causative copy number variants are frequently found even in cases of mild intellectual disability (30.77%). We want to emphasize the need to conduct microarray-based comparative genomic hybridization on all individuals with intellectual disability/developmental delay, regardless of the severity, because the degree of intellectual disability/developmental delay does not predict the diagnostic yield of microarray-based comparative genomic hybridization. [ABSTRACT FROM AUTHOR]

Pontocerebellar hypoplasias represent a group of neurodegenerative autosomal recessive disorders characterized by hypoplasia/atrophy of the cerebellum, hypoplastic ventral pons, and microcephaly and associated with various clinical features. Pontocerebellar hypolasia type 2 is the most common form, and different mutations in genes encoding subunits of the transfer ribonucleic acid (RNA)–splicing endonuclease (TSEN) complex were identified in patients. The authors report clinical, imaging, and molecular studies in 2 unrelated patients with different clinical pictures of the pontocerebellar hypoplasia type 2 spectrum and novel mutations in TSEN54, aiming to further define the clinical spectrum of the disease and possible indicators of more favorable progression. They identified a novel missense mutation c.355T>G/p.Y119D in compound heterozygosity with the “common” c.919G>T/p.A307S (patient 1) and a novel homozygous c.7ins6(CCGGAG)/p.E2-P3insPE variant (patient 2). An expanded array of mutations might contribute in defining possible differences in severity and phenotype-genotype correlations. [ABSTRACT FROM PUBLISHER]

Genome-wide high-resolution array analysis is rapidly becoming a reliable method of diagnostic investigation in individuals with mental retardation and congenital anomalies, leading to the identification of several novel microdeletion and microduplication syndromes. We have identified seven individuals with duplication on chromosome 14q11.2q13.1, who exhibited idiopathic developmental delay and cognitive impairment, severe speech delay, and developmental epilepsy. Among these cases, the minimal common duplicated region on chromosome 14q11.2q13.1 includes only three genes, FOXG1, C14orf23, and PRKD1. We propose that increased dosage of Forkhead Box G1 (FOXG1) is the best candidate to explain the abnormal neurodevelopmental phenotypes observed in our patients. Deletions and inactivating mutations of FOXG1 have been associated with a Rett-like syndrome characterized by hypotonia, irritability, developmental delay, hand stereotypies, and deceleration of head growth. FOXG1, encoding a brain-specific transcription factor, has an important role in the developing brain. In fact, in vivo studies in chicken brain demonstrated that overexpression of FOXG1 results in thickening of the neuroepithelium and outgrowth of the telencephalon and mesencephalum, secondary to a reduction in neuroepithelial cell apoptosis. [ABSTRACT FROM AUTHOR]

Objective: To establish and broaden the phenotypic spectrum of secretory carrier membrane protein (SCAMP5) associated with epilepsy and neurodevelopmental delay. Methods: A Chinese patient was identified at the First Hospital of Peking University, and the three unrelated patients were recruited from two different countries (Italy and United States) through GeneMatcher. SCAMP5 pathogenic variants were identified by whole exome sequencing; clinical data of the patients were retrospectively collected and analyzed. Result: The onset age of seizures was ranged from 6 to 15 months. Patients had different types of seizures, including focal seizures, generalized tonic-clonic seizures and tonic seizure. One patient showed typical autism spectrum disorder (ASD) symptoms. Electroencephalogram (EEG) findings presented as focal or multifocal discharges, sometimes spreading to generalization. Brain magnetic resonance imaging (MRI) abnormalities were present in each patient. Severe intellectual disability and language and motor developmental disorders were found in our patients, with all patients having poor language development and were nonverbal at last follow-up. All but one of the patients could walk independently in childhood, but the ability to walk independently in one patient had deteriorated with age. All patients had abnormal neurological exam findings, mostly signs of extrapyramidal system involvement. Dysmorphic features were found in 2/4 patients, mainly in the face and trunk. All four unrelated patients were found to have the same heterozygous pathogenic SCAMP5 de novo variant (p. Gly180Trp). Conclusion: Epilepsy, severe developmental delay, abnormal neurological exam findings, with or without ASD or variably dysmorphic features and were common in patients with SCAMP5 variant. The onset time and type of seizure varied greatly. The EEG and brain MRI findings were not consistent, but diverse and nonspecific. The motor ability of patients with heterozygous SCAMP5 variant might have a regressive course; language development was more severely affected. [ABSTRACT FROM AUTHOR]

Abstract: Chromosome 5p13 duplication syndrome (OMIM #613174), a contiguous gene syndrome involving duplication of several genes on chromosome 5p13 including NIPBL (OMIM 608667), has been described in rare patients with developmental delay and learning disability, behavioral problems and peculiar facial dysmorphisms. 5p13 duplications described so far present with variable sizes, from 0.25 to 13.6 Mb, and contain a variable number of genes. Here we report another patient with 5p13 duplication syndrome including NIPBL gene only. Proband''s phenotype overlapped that reported in patients with 5p13 microduplication syndrome and especially that of subjects with smaller duplications. Moreover, we better define genotype–phenotype relationship associated with this duplication and confirmed that NIPBL was likely the major dosage sensitive gene for the 5p13 microduplication phenotype. [Copyright &y& Elsevier]

Biallelic loss of function of TELO2 gene cause a severe syndromic disease mainly characterized by global developmental delay with poor motor and language acquisitions, microcephaly, short stature, minor facial and limbs anomalies, sleep disorder, spasticity, and balance impairment up to ataxia. TELO2 -related syndrome, also known as You-Hoover-Fong Syndrome, is extremely rare and since its first description in 2016 only 8 individuals have been reported, all showing a severe disability. The causative gene is member of the big molecular family of genes responsible for cells proliferation and DNA stability. We describe the case of two sisters, carrying the homozygous p. Arg609His variant of the gene, who present a milder phenotype of TELO2 -related syndrome. Such variant has been reported once in a more severely affected patient, in compound heterozygous state associated with the p. Pro260Leu variant, suggesting a possible role of the p. Arg609His variant in determining milder phenotypes. Comparing the siblings with all previously reported cases, we offer an overview on the condition and discuss TELO2 genetic interactions, in order to further explore the molecular bases of this recently described disorder. [ABSTRACT FROM AUTHOR]