Investigating the child with intellectual disability

Exploring Proteomic Alterations in Intellectual Disability: Insights from Hyperlipidemia and Hyperphosphatasia Subgroups

A significant increase of neurodevelopment disorders (NDDs) among children presents growing healthcare challenge worldwide. Owing to heterogenic, multifactorial nature of NDDs, understanding pathophysiology of disease, finding effective methods for the early detection and intervention of NDDs has become extremely complex. This study aims to investigate the molecular mechanisms of NDDs, focusing on the associations between hyperphosphatasia (HPP) and hyperlipidemia (HLD) in patients with intellectual disability (ID). Blood samples from 800 study participants (ID patients and healthy individuals, HC) were analyzed for the biochemical differences. Among them, 105 ID patients with uniquely altered biochemical profiles (ID-HPP, n = 28; ID-HLD, n = 77) and 65 HC samples were further investigated for nLC-MS/MS-based proteomic analysis. A total of 354 proteins were identified in label-free quantitative proteomic analysis of the all groups (ID-HPP, ID-HLD, and HC). The ID-HPP and ID-HLD groups each had distinct protein profiles compared to HC, with 28 and 85 differentially expressed proteins, respectively. The ID-HLD group had 66 unique proteins, whereas ID-HPP had 9 unique proteins, with 19 proteins common among the subgroups of ID. Pathway analysis of common proteins revealed shared pathways as the complement system and lipoprotein metabolism disruptions, but distinct pathway disturbances: toll-like receptor and integrin signaling in ID-HPP, and hemostatic pathway dysregulation in ID-HLD. These findings elucidate systemic pathway abnormalities in NDDs, including ID.

Brain volumes in genetic syndromes associated with mTOR dysregulation: a systematic review and meta-analysis

BACKGROUND/OBJECTIVES

Dysregulation of molecular pathways associated with mechanistic target of rapamycin (mTOR) and elevated rates of neurodevelopmental disorders are implicated in the genetic syndromes neurofibromatosis type 1 (NF1), tuberous sclerosis complex (TSC), fragile X syndrome (FXS), and Noonan syndrome (NS). Given shared molecular and clinical features, understanding convergent and divergent implications of these syndromes on brain development may offer unique insights into disease mechanisms. While an increasing number of studies have examined brain volumes in these syndromes, the effects of each syndrome on global and subcortical brain volumes are unclear. Therefore, the aim of the current study was to conduct a systematic review and meta-analysis to synthesize existing literature on volumetric brain changes across TSC, FXS, NF1, and NS. Study outcomes were the effect sizes of the genetic syndromes on whole brain, gray and white matter, and subcortical volumes compared to typically developing controls.

SUBJECTS/METHODS

We performed a series of meta-analyses synthesizing data from 23 studies in NF1, TSC, FXS, and NS (pooled N = 1556) reporting whole brain volume, gray and white matter volumes, and volumes of subcortical structures compared to controls.

RESULTS

Meta-analyses revealed significantly larger whole brain volume, gray and white matter volumes, and subcortical volumes in NF1 compared to controls. FXS was associated with increased whole brain, and gray and white matter volumes relative to controls, but effect sizes were smaller than those seen in NF1. In contrast, studies in NS indicated smaller whole brain and gray matter volumes, and reduced subcortical volumes compared to controls. For individuals with TSC, there were no significant differences in whole brain, gray matter, and white volumes compared to controls. Volumetric effect sizes were not moderated by age, sex, or full-scale IQ.

CONCLUSIONS

This meta-analysis revealed that dysregulation of mTOR signaling across pre- and post-natal periods of development can result in convergent and divergent consequences for brain volume among genetic syndromes. Further research employing advanced disease modeling techniques with human pluripotent stem cell-derived in vitro models is needed to further refine our understanding of between and within syndrome variability on early brain development and identify shared molecular mechanisms for the development of pharmaceutical interventions.

A novel DLG4 variant causes DLG4-related synaptopathy with intellectual regression

DLG4-related synaptopathy is a neurodevelopmental disorder caused by a DLG4 variant. We identified a novel de novo heterozygous frameshift variant, NM_001321075.3(DLG4):c.554_563del, in a Japanese girl. Intellectual regression without motor delay was observed at 2 years of age, and she was diagnosed with autism spectrum disorder and attention-deficit/hyperactivity disorder. Recognizing the possibility of DLG4-related synaptopathy in patients with intellectual regression is important for ensuring an accurate diagnosis.

What matters to parents? A scoping review of parents' service experiences and needs regarding genetic testing for rare diseases

Patient care experiences are key to promoting better outcomes and are an essential consideration for successful implementation of genomics in paediatric care. To understand parents' service experiences and needs regarding testing of their child for rare diseases, we conducted a scoping review. Five databases were searched (2000-2022), with 29 studies meeting the inclusion criteria. Experiences of care wholly delivered by genetic services were most commonly reported (n = 11). Results were synthesised by mapping extracted data to adapted Picker principles of person-centred care. Parents especially valued and emphasised the importance of feeling 'cared for', continuous relationships with clinicians, empathic communication, being kept informed while awaiting genetic test results, linkage with informational and psychosocial resources following results disclosure, and follow-up. Strategies were often proposed by authors to address long-standing unmet needs but evidence from the literature regarding their potential effectiveness was rarely provided. We conclude that 'what matters' to parents regarding genetic testing is not dissimilar to other aspects of care. Paediatric medical specialists have existing skill sets, trusted relationships and can apply familiar principles of 'good' care to enhance experiences of genetic testing. The lack of evidence for service improvement strategies highlights the pressing need to undertake rigorous design and testing of interventions alongside mainstreaming of genomics into paediatric care.

Screening Children's Intellectual Disabilities with Phonetic Features, Facial Phenotype and Craniofacial Variability Index

BACKGROUND

Intellectual Disability (ID) is a kind of developmental deficiency syndrome caused by congenital diseases or postnatal events. This syndrome could be intervened as soon as possible if its early screening was efficient, which may improve the condition of patients and enhance their self-care ability. The early screening of ID is always achieved by clinical interview, which needs in-depth participation of medical professionals and related medical resources.

METHODS

A new method for screening ID has been proposed by analyzing the facial phenotype and phonetic characteristic of young subjects. First, the geometric features of subjects' faces and phonetic features of subjects' voice are extracted from interview videos, then craniofacial variability index (CVI) is calculated with the geometric features and the risk of ID is given with the measure of CVI. Furthermore, machine learning algorithms are utilized to establish a method for further screening ID based on facial features and phonetic features.

RESULTS

The proposed method using three feature sets, including geometric features, CVI features and phonetic features was evaluated. The best performance of accuracy was closer to 80%.

CONCLUSIONS

The results using the three feature sets revealed that the proposed method may be applied in a clinical setting in the future after continuous improvement.

The exploration of genetic aetiology and diagnostic strategy for 321 Chinese individuals with intellectual disability

BACKGROUND

Intellectual disability is a heterogeneous neurodevelopmental disorder with complex genetic architectures. Different sequential methodologies are usually applied to identify the genetic aetiologies of ID patients.

METHODS

We collected 321 consecutive ID patients. All patients underwent karyotyping, while 293 and 164 cases further received copy number variation sequencing (CNV-seq) and whole-exome sequencing (WES). The updated WES technology can detect CNVs simultaneously. The diagnostic data from 137 patients who received WES and CNV-seq were used to define the approach that could be recommended as the first-tier test.

RESULTS

WES obtains the highest diagnostic yield of 50% (82/164), compared with karyotyping (7.79%, 25/321) and CNV-seq (19.80%, 58/293). Among the variants detected by WES, 66.67% (44/66) de novo and 57.58% (38/66) novel pathogenic/likely pathogenic (P/LP) variants were identified in patients with ID. Besides, 24 out of 25P/LP CNVs discovered by CNV-seq can also be accurately identified using WES in 137 patients who received WES and CNV-seq. Thus, genetic abnormalities found through karyotyping, CNV-seq, and WES can be completely detected by combined karyotyping and WES.

CONCLUSIONS

This study illustrates the genetic aberrations of a Chinese ID cohort and expands the mutation spectrum of ID-related genes. Compared with the conventional diagnostic strategy, a combination of karyotype analysis and WES could be recommended as the first-tier diagnostic strategy for ID patients.

Trio-based exome sequencing reveals a high rate of the de novo variants in intellectual disability

Intellectual disability (ID), a neurodevelopmental disorder affecting 1-3% of the general population, is characterized by limitations in both intellectual function and adaptive skills. The high number of conditions associated with ID underlines its heterogeneous origin and reveals the difficulty of obtaining a rapid and accurate genetic diagnosis. However, the Next Generation Sequencing, and the whole exome sequencing (WES) in particular, has boosted the diagnosis rate associated with ID. In this study, WES performed on 244 trios of patients clinically diagnosed with isolated or syndromic ID and their respective unaffected parents has allowed the identification of the underlying genetic basis of ID in 64 patients, yielding a diagnosis rate of 25.2%. Our results suggest that trio-based WES facilitates ID's genetic diagnosis, particularly in patients who have been extensively waiting for a definitive molecular diagnosis. Moreover, genotypic information from parents provided by trio-based WES enabled the detection of a high percentage (61.5%) of de novo variants inside our cohort. Establishing a quick genetic diagnosis of ID would allow early intervention and better clinical management, thus improving the quality of life of these patients and their families.

Paediatric genomic testing: Navigating medicare rebatable genomic testing

Genomic testing for a genetic diagnosis is becoming standard of care for many children, especially those with a syndromal intellectual disability. While previously this type of specialised testing was performed mainly by clinical genetics teams, it is increasingly being 'mainstreamed' into standard paediatric care. With the introduction of a new Medicare rebate for genomic testing in May 2020, this type of testing is now available for paediatricians to order, in consultation with clinical genetics. Children must be aged less than 10 years with facial dysmorphism and multiple congenital abnormalities or have global developmental delay or moderate to severe intellectual disability. This rebate should increase the likelihood of a genetic diagnosis, with accompanying benefits for patient management, reproductive planning and diagnostic certainty. Similar to the introduction of chromosomal microarray into mainstream paediatrics, this genomic testing will increase the number of genetic diagnoses, however, will also yield more variants of uncertain significance, incidental findings, and negative results. This paper aims to guide paediatricians through the process of genomic testing, and represents the combined expertise of educators, clinical geneticists, paediatricians and genomic pathologists around Australia. Its purpose is to help paediatricians navigate choosing the right genomic test, consenting patients and understanding the possible outcomes of testing.

Aberrant Structural and Functional Developmental Trajectories in Children With Intellectual Disability

Intellectual disability (ID) is associated with aberrant structural and functional development of the brain, yet how the dynamical developmental changes of the structure and function of ID from childhood to around puberty remains unknown. To explore the abnormal developmental trajectories of structure and function, 40 children with ID aged 6-13 years and 30 sex-, age-, and educational level-matched healthy controls (HC) with age range from 6 to 13 were recruited. The automatic voxel-based morphometry (VBM) and resting-state functional connectivity (FC) analyses were adopted to delineate the structural and functional differences. Significantly decreased total gray matter volume (GMV) and white matter volume (WMV) in children with ID were found, and the developmental trajectories of GMV and WMV in children with ID showed an opposite direction as compared with HC. The voxel-wise VMB analysis further revealed significantly increased GMV in the dorsal medial prefrontal cortex (dmPFC), bilateral orbital part of the inferior frontal gyrus (orb_IFG.L, orb_IFG.R), right cuneus (cuneus.R), and bilateral middle frontal gyrus (MFG.L, MFG.R) in children with ID. The following seed-based whole-brain functional connectivity analyses of the brain areas with changed GMV found decreased FCs between the cuneus.R and left intraparietal sulcus (IPS.L) and between the MFG.R and anterior cingulate cortex (ACC) in children with ID. Moreover, negative correlations between GMV values in the dmPFC, orb_IFG.L, cuneus.R, and intelligence quotient (IQ) scores and positive correlations between the FCs of the cuneus.R with IPS.L and MFG.R with ACC and IQ scores were found in children with ID and HC. Our findings provide evidence for the abnormal structural and functional development in children with ID and highlight the important role of frontoparietal network in the typical development. The abnormal development of GMV and functional couplings found in this study may be the neuropathological bases of children with ID.

Adverse childhood experiences-household stressors and children's mental health: a single centre retrospective review

OBJECTIVE

To determine the prevalence of reported 'household stressor' adverse childhood experiences (ACEs) in families of children presenting with neurodevelopmental, behavioural or emotional difficulties and to determine whether family vulnerabilities, individually or cumulatively, were associated with particular clinical symptomatology.

DESIGN

Retrospective chart review followed by statistical analysis of family stressors and clinical symptomatology.

SETTING

A community paediatric clinic in Australia.

PARTICIPANTS

All 267 children who attended an initial paediatric appointment during 2018.

RESULTS

162 (60.7%) children had been exposed to one or more household stressor ACEs, including 116 (43.4%) children exposed to parental mental illness. Behavioural disturbance occurred in 144 (53.9%) children and externalising behaviours (other than attention deficit hyperactivity disorder) were more frequent than internalising behaviours. Externalising and internalising behaviours were associated with individual and cumulative household stressor ACEs. Most other symptomatology apart from genetic/neurological conditions, autistic symptoms and some developmental delays appeared to be partially associated with ACEs.

CONCLUSION

Household stressor ACEs were common, frequently occurred concurrently, and were associated with much of the symptomatology, in this cohort. Parental mental illness was the most prevalent stressor and behavioural disturbance the most prevalent symptomatology. These findings may have implications for clinical practice and service provision.

A missense mutation in the catalytic domain of O-GlcNAc transferase links perturbations in protein O-GlcNAcylation to X-linked intellectual disability

X-linked intellectual disabilities (XLID) are common developmental disorders. The enzyme O-GlcNAc transferase encoded by OGT, a recently discovered XLID gene, attaches O-GlcNAc to nuclear and cytoplasmic proteins. As few missense mutations have been described, it is unclear what the aetiology of the patient phenotypes is. Here, we report the discovery of a missense mutation in the catalytic domain of OGT in an XLID patient. X-ray crystallography reveals that this variant leads to structural rearrangements in the catalytic domain. The mutation reduces in vitro OGT activity on substrate peptides/protein. Mouse embryonic stem cells carrying the mutation reveal reduced O-GlcNAcase (OGA) and global O-GlcNAc levels. These data suggest a direct link between changes in the O-GlcNAcome and intellectual disability observed in patients carrying OGT mutations.