Neurological features of 14q24-q32 interstitial deletion: report of a new case

Copy number variations in autistic children

Autism spectrum disorder (ASD) manifests as a neurodevelopmental condition marked by challenges in social communication, interaction and the performing of repetitive behaviors. The prevalence of autism increases markedly on an annual basis; however, the etiology remains incompletely understood. Cytogenetically visible chromosomal abnormalities, including copy number variations (CNVs), have been shown to contribute to the pathogenesis of ASD. More than 1% of ASD conditions can be explained based on a known genetic locus, whereas CNVs account for 5-10% of cases. However, there are no studies on the Saudi Arabian population for the detection of CNVs linked to ASD, to the best of our knowledge. Therefore, the aim of the present study was to explore the prevalence of CNVs in autistic Saudi Arabian children. Genomic DNA was extracted from the peripheral blood of 14 autistic children along with four healthy control children and then array-based comparative genomic hybridization (aCGH) was used to detect CNVs. Bioinformatics analysis of the aCGH results showed the presence of recurrent and non-recurrent deletion/duplication CNVs in several regions of the genome of autistic children. The most frequent CNVs were 1q21.2, 3p26.3, 4q13.2, 6p25.3, 6q24.2, 7p21.1, 7q34, 7q11.1, 8p23.2, 13q32.3, 14q11.1-q11.2 and 15q11.1-q11.2. In the present study, CNVs in autistic Saudi Arabian children were identified to improve the understanding of the etiology of autism and facilitate its diagnosis. Additionally, the present study identified certain possible pathogenic genes in the CNV region associated with several developmental and neurogenetic diseases.

Fetal MRI Analysis of Corpus Callosal Abnormalities: Classification, and Associated Anomalies

BACKGROUND

Corpus callosal abnormalities (CCA) are midline developmental brain malformations and are usually associated with a wide spectrum of other neurological and non-neurological abnormalities. The study aims to highlight the diagnostic role of fetal MRI to characterize heterogeneous corpus callosal abnormalities using the latest classification system. It also helps to identify associated anomalies, which have prognostic implications for the postnatal outcome.

METHODS

In this study, retrospective data from antenatal women who underwent fetal MRI between January 2014 and July 2023 at Rush University Medical Center were evaluated for CCA and classified based on structural morphology. Patients were further assessed for associated neurological and non-neurological anomalies.

RESULTS

The most frequent class of CCA was complete agenesis (79.1%), followed by hypoplasia (12.5%), dysplasia (4.2%), and hypoplasia with dysplasia (4.2%). Among them, 17% had isolated CCA, while the majority (83%) had complex forms of CCA associated with other CNS and non-CNS anomalies. Out of the complex CCA cases, 58% were associated with other CNS anomalies, while 8% were associated with non-CNS anomalies. 17% of cases had both.

CONCLUSION

The use of fetal MRI is valuable in the classification of abnormalities of the corpus callosum after the confirmation of a suspected diagnosis on prenatal ultrasound. This technique is an invaluable method for distinguishing between isolated and complex forms of CCA, especially in cases of apparent isolated CCA. The use of diffusion-weighted imaging or diffusion tensor imaging in fetal neuroimaging is expected to provide further insights into white matter abnormalities in fetuses diagnosed with CCA in the future.

Case Report-An Inherited Loss-of-Function NRXN3 Variant Potentially Causes a Neurodevelopmental Disorder with Autism Consistent with Previously Described 14q24.3-31.1 Deletions

BACKGROUND

Heterozygous, large-scale deletions at 14q24.3-31.1 affecting the neurexin-3 gene have been associated with neurodevelopmental disorders such as autism. Both "de novo" occurrences and inheritance from a healthy parent suggest incomplete penetrance and expressivity, especially in autism spectrum disorder. NRXN3 encodes neurexin-3, a neuronal cell surface protein involved in cell recognition and adhesion, as well as mediating intracellular signaling. NRXN3 is expressed in two distinct isoforms (alpha and beta) generated by alternative promoters and splicing. MM/Results: Using exome sequencing, we identified a monoallelic frameshift variant c.159_160del (p.Gln54AlafsTer50) in the NRXN3 beta isoform (NM_001272020.2) in a 5-year-old girl with developmental delay, autism spectrum disorder, and behavioral issues. This variant was inherited from her mother, who did not have any medical complaints.

DISCUSSION

This is the first detailed report of a loss-of-function variant in NRXN3 causing an identical phenotype, as reported for heterozygous large-scale deletions in the same genomic region, thereby confirming NRXN3 as a novel gene for neurodevelopmental disorders with autism.

Generation of induced pluripotent stem cell line GZHMCi006-A from amniotic fluid-derived cells with deletion 14q syndrome

The deletions of the long arm of chromosome 14 involving the 14q24-q32 region have been identified as deletion 14q (del 14q) syndrome, but were rarely reported. The patients with del 14q syndrome are observed a peculiar facial appearance and neurological defects, but the molecular mechanisms were not clear. Here we generated a human iPSC line from the patient's amniotic fluid cells with 24 Mb deletion in 14q24.3q32.31 which will serve as useful tools for studying the mechanism of del 14q syndrome and the genes involved, which will provide useful basic theory of prenatal diagnosis.

Chromosome 14 deletions, rings, and epilepsy genes: A riddle wrapped in a mystery inside an enigma

The ring 14 syndrome is a rare condition caused by the rearrangement of one chromosome 14 into a ring-like structure. The formation of the ring requires two breakpoints and loss of material from the short and long arms of the chromosome. Like many other chromosome syndromes, it is characterized by multiple congenital anomalies and developmental delays. Typical of the condition are retinal anomalies and drug-resistant epilepsy. These latter manifestations are not found in individuals who are carriers of comparable 14q deletions without formation of a ring (linear deletions). To find an explanation for this apparent discrepancy and gain insight into the mechanisms leading to seizures, we reviewed and compared literature cases of both ring and linear deletion syndrome with respect to both their clinical manifestations and the role and function of potentially epileptogenic genes. Knowledge of the epilepsy-related genes in chromosome 14 is an important premise for the search of new and effective drugs to combat seizures. Current clinical and molecular evidence is not sufficient to explain the known discrepancies between ring and linear deletions.

A rare exonic NRXN3 deletion segregating with neurodevelopmental and neuropsychiatric conditions in a three-generation Chinese family

Members of the neurexin gene family, neurexin 1 (NRXN1), neurexin 2 (NRXN2), and neurexin 3 (NRXN3) encode important components of synaptic function implicated in autism and other neurodevelopmental/neuropsychiatric disorders. Loss of function variants have been reported predominantly in NRXN1, with fewer such variants detected in NRXN2 and NRXN3. Evidence for segregating NRNX3 variants has particularly been lacking. Here, we report identification by chromosomal microarray analysis of a rare exonic deletion affecting the NRXN3 alpha isoform in a three-generation Chinese family. The proband, a 7-year-old boy, presented with motor and language delay and met the clinical diagnostic criteria for autism. He also presented with moderate intellectual disability, attention-deficit hyperactivity disorder and facial dysmorphic features. The mother and maternal grandfather, both deletion carriers, presented with variable degrees of language and communication difficulties, as well as neuropsychiatric problems such as schizophrenia and temper tantrums. A compilation of sporadic cases with deletions involving part or all of NRXN3 revealed that 9 of 23 individuals (39%) displayed features of autism. The evidence for cosegregation in our family further supports a role for NRXN3 in autism and neurodevelopmental/neuropsychiatric disorders but demonstrates intrafamily variable expressivity due to this NRXN3 deletion, with schizophrenia and facial dysmorphism being potential novel features of NRXN3 haploinsufficiency.

"Minimal" holoprosencephaly in a 14q deletion syndrome patient

We report on a patient with terminal deletion of the long arm of chromosome 14 displaying brain interhemispheric fusion limited to the midline anterior frontal cortex associated with hypoplastic corpus callosum and incomplete rotation of the left hippocampus in a clinical setting of motor and intellectual disability with poor language, and social behavior abnormalities with aggressiveness. Some possible correlations between clinical signs and symptoms and various aspects of the complex brain malformation are briefly discussed and compared with other known abnormalities of chromosome 14. The different neuropathology of the most common forms and the new forms of holoprosencephaly recently described is also discussed and leads us to suggest classifying the interhemispheric fusion of this case as a "minimal" form of holoprosencephaly. This appears to be the first description in a 14q deletion patient.