Expanding the phenotype of intellectual disability caused by HIVEP2 variants

Parental gonadossomatic mosaicism in HIVEP2-related intellectual disability and impact on genetic counseling-case report

Intellectual development disorder, autosomal dominant 43 (MRD43) is an autosomal dominant disorder caused by heterozygous mutations in the HIVEP2 gene. In this report, we describe a case of a 4-year-old boy with global development delay, hypotonia, and dysmorphic features, in whom the finding of a heterozygous nonsense pathogenic variant in exon 5 of HIVEP2 [c.2827C>T p. (Arg943*)] through WES established a MRD43 diagnosis. Our patient's phenotype overlaps with other MRD43 descriptions in the literature. Unlike previously reported cases, where the condition was almost invariably de novo, the healthy mother in this case presented mosaicism for the pathogenic variant. Thus, the recurrence risk increased significantly from 1% to up to 50%. The description of a variant inherited for MDR43 is singular in the literature and this description highlights the importance of parental studies for accurate genetic counseling, particularly for family planning.

Neurodevelopmental profile of HIVEP2-related disorder

AIM

To characterize the neurodevelopmental profile and systemic features of HIVEP2-related disorder.

METHOD

This study used retrospective medical history and standardized assessment data from Simons Searchlight to describe the clinical characteristics of 12 individuals (eight males, four females; age range 3y 3mo-12y 8mo; mean age [SD] 7y 7mo [2y 11mo]) with pathogenic HIVEP2 variants, focusing on their levels of adaptive functioning, autism symptomology, and emotional and behavioral characteristics.

RESULTS

Common features included neonatal complications, hypotonia, developmental delay, intellectual disability, language impairment, gastroesophageal reflux, and strabismus. A minority of individuals had epilepsy, microcephaly, or a movement disorder. Based on the Vineland Adaptive Behavior Scales, Second Edition, affected individuals showed impairments in adaptive behavior (mean composite standard score [SD] 56.4 [10.2]; n=8). The cohort also had significant impairments in social problems, as measured by the Social Responsiveness Scale, Second Edition (mean total score [SD] 76.4 [11.3]; n=10) and clinically significant emotional and behavioral difficulties, as measured by the Child Behavior Checklist for ages 6-18 (mean total T score [SD] 66.9 [8.2]; n=8).

INTERPRETATION

These results show that individuals with HIVEP2-related disorder have impairments in adaptive and social-related behaviors as well as difficulties in emotional and behavioral symptoms.

Schnurri-2 promotes the expression of excitatory glutamate receptors and contributes to neuropathic pain

Neuropathic pain is a type of chronic pain with complex mechanisms, and current treatments have shown limited success in treating patients suffering from chronic pain. Accumulating evidence has shown that the pathogenesis of neuropathic pain is mediated by the plasticity of excitatory neurons in the dorsal horn of the spinal cord, which provides insights into the treatment of hyperalgesia. In this study, we found that Schnurri-2 (Shn2) was significantly upregulated in the L4-L6 segments of the spinal cord of C57 mice with spared nerve injury, which was accompanied by an increase in GluN2D subunit and glutamate receptor subunit 1 (GluR1) levels. Knocking down the expression of Shn2 using a lentivirus in the spinal cord decreased the GluN2D subunit and GluR1 levels in spared nerve injury mice and eventually alleviated mechanical allodynia. In summary, Shn2 regulates neuropathic pain, promotes the upregulation of GluN2D in glutamatergic neurons and increases the accumulation of GluR1 in excitatory neurons. Taken together, our study provides a new underlying mechanism for the development of neuropathic pain.

New genes involved in Angelman syndrome-like: Expanding the genetic spectrum

Angelman syndrome (AS) is a neurogenetic disorder characterized by severe developmental delay with absence of speech, happy disposition, frequent laughter, hyperactivity, stereotypies, ataxia and seizures with specific EEG abnormalities. There is a 10–15% of patients with an AS phenotype whose genetic cause remains unknown (Angelman-like syndrome, AS-like). Whole-exome sequencing (WES) was performed on a cohort of 14 patients with clinical features of AS and no molecular diagnosis. As a result, we identified 10 de novo and 1 X-linked pathogenic/likely pathogenic variants in 10 neurodevelopmental genes (SYNGAP1, VAMP2, TBL1XR1, ASXL3, SATB2, SMARCE1, SPTAN1, KCNQ3, SLC6A1 and LAS1L) and one deleterious de novo variant in a candidate gene (HSF2). Our results highlight the wide genetic heterogeneity in AS-like patients and expands the differential diagnosis.

Genetic Etiologies in Developmental and/or Epileptic Encephalopathy With Electrical Status Epilepticus During Sleep: Cohort Study

Background

Recently, the electroencephalogram pattern of electrical status epilepticus during sleep (ESES) had been reported in some genetic disorders, and most of them were noted with developmental and epileptic encephalopathy (DEE) or epileptic encephalopathy (EE). This study aimed to determine the genetic etiologies and clinical characteristics of ESES in DEE/EE.

Methods

We performed a cohort study in cases of DEE or EE with ESES. Tio-based genetic testing was performed in 74 cases and was analyzed to identify underlying variants.

Results

Pathogenic or likely pathogenic variants were identified in 17/74 cases, including KCNQ2 (n = 6), KCNA2 (n = 5), GRIN2A (n = 3), SLC9A6 (n = 1), HIVEP2 (n = 1), and RARS2 (n = 1). Eleven were boys. The median age at seizure onset was 6 months. ESES occurred at the mean age of 2.0 ± 1.2 years, predominant in the Rolandic region in 14 years. Twelve of 17 cases had the first stage of different epilepsy preceding ESES: 2/12 were diagnosed as Ohtahara syndrome, 2/12 were diagnosed as infantile spasms, 3/12 were diagnosed as DEE, and 5/12 were diagnosed as EE without the epileptic syndrome.

Conclusion

Monogenic variants explained over 20% of DEE/EE with ESES. ESES could be an age-related feature in genetic disorders and occurred after the first stage of different epilepsy. Both age-related factors and genetic etiology were suggested to play a role in the occurrence of ESES in genetic DEE/EE.

CircHivep2 contributes to microglia activation and inflammation via miR-181a-5p/SOCS2 signalling in mice with kainic acid-induced epileptic seizures

Epilepsy is a chronic brain disease characterized by recurrent seizures. Circular RNA (circRNA) is a novel family of endogenous non‐coding RNAs that have been proposed to regulate gene expression. However, there is a lack of data on the role of circRNA in epilepsy. In this study, the circRNA profiles were evaluated by microarray analysis. In total, 627 circRNAs were up‐regulated, whereas 892 were down‐regulated in the hippocampus in mice with kainic acid (KA)‐induced epileptic seizures compared with control. The expression of circHivep2 was significantly down‐regulated in hippocampus tissues of mice with KA‐induced epileptic seizures and BV‐2 microglia cells upon KA treatment. Bioinformatics analysis predicted that circHivep2 interacts with miR‐181a‐5p to regulate SOCS2 expression, which was validated using a dual‐luciferase reporter assay. Moreover, overexpression of circHivep2 significantly inhibited KA‐induced microglial activation and the expression of inflammatory factors in vitro, which was blocked by miR‐181a‐5p, whereas circHivep2 knockdown further induced microglia cell activation and the release of pro‐inflammatory proteins in BV‐2 microglia cells after KA treatment. The application of circHivep2+ exosomes derived from adipose‐derived stem cells (ADSCs) exerted significant beneficial effects on the behavioural seizure scores of mice with KA‐induced epilepsy compared to control exosomes. The circHivep2+ exosomes also inhibited microglial activation, the expression of inflammatory factors, and the miR‐181a‐5p/SOCS2 axis in vivo. Our results suggest that circHivep2 regulates microglia activation in the progression of epilepsy by interfering with miR‐181a‐5p to promote SOCS2 expression, indicating that circHivep2 may serve as a therapeutic tool to prevent the development of epilepsy.