Motor difficulties in 16p11.2 copy number variation

The rare genetic variants 16p11.2 duplication and 16p11.2 deletion have opposing effects on brain structure and function, yet are associated with broadly similar clinical phenotypes that include autism, intellectual impairment, psychiatric illness, and motor difficulties. In recent years, studies have identified subtle distinctions between the phenotypic effects of 16p11.2 duplication and 16p11.2 deletion with respect to patterns of autism, intellectual impairment, and psychiatric illness. However, although divergent phenotypic findings in some motor domains have been reported, no study has yet made a comprehensive comparison of motor difficulties between 16p11.2 deletion and 16p11.2 duplication carriers to elucidate points of convergence and divergence. We sought to make such a comparison in a group of 133 16p11.2 deletion carriers, 122 duplication carriers, and 388 familial controls, hypothesizing that motor impairment would overall be greater in deletion than duplication carriers. In a series of regression models, we found that 16p11.2 deletion status tended to predict greater impairment along indices of gross motor function, but less impairment along indices of fine motor function. These findings point to a potential pattern of performance difficulties that could be investigated in future studies. Elucidating motor differences between 16p11.2 duplication and 16p11.2 deletion carriers may help in understanding the complex effect of 16p11.2 copy number variation and other rare genetic causes of autism.

Association of behavioural and social-communicative profiles in children with 16p11.2 copy number variants: a multi-site study

BACKGROUND

Despite the established knowledge that recurrent copy number variants (CNVs) at the 16p11.2 locus BP4-BP5 confer risk for behavioural and language difficulties, limited research has been conducted on the association between behavioural and social-communicative profiles. The current study aims to further delineate the prevalence, nature and severity of, and the association between, behavioural and social-communicative features of school-aged children with 16p11.2 deletion syndrome (16p11.2DS) and 16p11.2 duplication (16p11.2Dup).

METHODS

A total of 68 individuals (n = 47 16p11.2DS and n = 21 16p11.2Dup) aged 6-17 years participated. Standardised intelligence tests were administered, and behavioural and social-communicative skills were assessed by standardised questionnaires. Scores of both groups were compared with population norms and across CNVs. The influence of confounding factors was investigated, and correlation analyses were performed.

RESULTS

Compared with the normative sample, children with 16p11.2DS showed high rates of social responsiveness (67%) and communicative problems (69%), while approximately half (52%) of the patients displayed behavioural problems. Children with 16p11.2Dup demonstrated even higher rates of social-communicative problems (80-90%) with statistically significantly more externalising and overall behavioural challenges (89%). In both CNV groups, there was a strong positive correlation between behavioural and social-communicative skills.

CONCLUSIONS

School-aged children with 16p11.2 CNVs show high rates of behavioural, social responsiveness and communicative problems compared with the normative sample. These findings point to the high prevalence of autistic traits and diagnoses in these CNV populations. Moreover, there is a high comorbidity between behavioural and social-communicative problems. Patients with difficulties in both domains are vulnerable and need closer clinical follow-up and care.

Fatal cardiac dysfunction in a child with Williams syndrome

Williams syndrome (WS) is a rare genetic disorder caused by a microdeletion of chromosome 7q11.23. Although the mortality rate of patients with WS is not very high, sudden cardiac death can occur, particularly in cases complicated by coronary artery stenosis. A 3-month-old female infant with supravalvular aortic stenosis and peripheral pulmonary stenosis was discovered unconscious in bed by her mother. She was immediately transferred to an emergency hospital but succumbed despite multiple attempts as resuscitation. DNA microarray analysis revealed microdeletions of 7q11.23 and 16p11.2, confirming WS and unexpectedly identifying 16p11.2 deletion syndrome which is known to be associated with neurodevelopmental disorders. Postmortem computed tomography revealed a severely enlarged heart, indicative of cardiac dysfunction. External examination revealed moderate-to-severe developmental delays in height and body weight. The heart, on internal examination, revealed whitish-discolored lesions; histologically severe fibrotic changes and thickening of the intima in the coronary arteries and aorta. In the brain, the dentate gyrus of the hippocampus appeared malformed. Taken together, these findings suggest that the cause of death was cardiac dysfunction due to WS. In addition, it could be possible that 16p11.2 deletion syndrome and dentate gyrus malformation contributed to her death. Future autopsy studies are warranted to clarify the precise role of microdeletion disorders in sudden death to reduce future preventable deaths in children.

Resting Energy Expenditure and Body Composition in Children and Adolescents With Genetic, Hypothalamic, Medication-Induced or Multifactorial Severe Obesity

BACKGROUND

Pediatric obesity is a multifactorial disease which can be caused by underlying medical disorders arising from disruptions in the hypothalamic leptin-melanocortin pathway, which regulates satiety and energy expenditure.

AIM

To investigate and compare resting energy expenditure (REE) and body composition characteristics of children and adolescents with severe obesity with or without underlying medical causes.

METHODS

This prospective observational study included pediatric patients who underwent an extensive diagnostic workup in our academic centre that evaluated endocrine, non-syndromic and syndromic genetic, hypothalamic, and medication-induced causes of obesity. REE was assessed by indirect calorimetry; body composition by air displacement plethysmography. The ratio between measured REE (mREE) and predicted REE (Schofield equations), REE%, was calculated, with decreased mREE defined as REE% ≤90% and elevated mREE ≥110%. Additionally, the influence of fat-free-mass (FFM) on mREE was evaluated using multiple linear regression.

RESULTS

We included 292 patients (146 [50%] with body composition measurements), of which 218 (75%) patients had multifactorial obesity and 74 (25%) an underlying medical cause: non-syndromic and syndromic genetic (n= 29 and 28, respectively), hypothalamic (n= 10), and medication-induced (n= 7) obesity. Mean age was 10.8 ± 4.3 years, 59% were female, mean BMI SDS was 3.8 ± 1.1, indicating severe obesity. Mean REE% was higher in children with non-syndromic genetic obesity (107.4% ± 12.7) and lower in children with hypothalamic obesity (87.6% ± 14.2) compared to multifactorial obesity (100.5% ± 12.6, both p<0.01). In 9 children with pseudohypoparathyroidism type 1a, mean REE% was similar (100.4 ± 5.1). Across all patients, mREE was decreased in 60 (21%) patients and elevated in 69 (24%) patients. After adjustment for FFM, mREE did not differ between patients within each of the subgroups of underlying medical causes compared to multifactorial obesity (all p>0.05).

CONCLUSIONS

In this cohort of children with severe obesity due to various etiologies, large inter-individual differences in mREE were found. Consistent with previous studies, almost half of patients had decreased or elevated mREE. This knowledge is important for patient-tailored treatment, e.g. personalized dietary and physical activity interventions and consideration of pharmacotherapy affecting central energy expenditure regulation in children with decreased mREE.

Distinct Basal Metabolism in Three Mouse Models of Neurodevelopmental Disorders

Prevalence of metabolic disturbances is higher among individuals with neurodevelopmental disorders (NDDs), yet this association has been largely overlooked. Investigation into human disease remains challenging, as a complete pathophysiological understanding relies on accurate modeling and highly controlled variables. Genetically engineered mouse models are widely used to gain insight into the biology of human NDDs, but research focus has been on behavioral and neurophysiological abnormalities. Such models not only allow for evaluating usefulness in reproducing human features, including similarities and discrepancies with rodent phenotypes, but they also represent a unique opportunity to observe and quantify novel anomalies. Here, we present the first characterization and comparison of basal metabolism in three mouse models of NDDs, namely, Down syndrome (DS; Dp(16)Yey/+ mice), 16p11.2 deletion syndrome (16pDel; 16p11.2^df/+ mice), and fragile X syndrome [FXS; Fmr1 knock-out (KO) mice] and their wild-type (WT) counterparts. Using the Comprehensive Lab Animal Monitoring System (CLAMS) coupled to EchoMRI, as well as quantification of key plasma metabolites by liquid chromatography mass spectrometry (LC-MS), our in vivo study reveals that each mouse model expresses a unique metabolic signature that is sex-specific, independent of the amount of food consumed and minimally influenced by physical activity. In particular, we identify striking differences in body composition, respiratory exchange ratio (RER), caloric expenditure (CE), and concentrations of circulating plasma metabolites related to mitochondrial function. Providing novel insight into NDD-associated metabolic alterations is an essential prerequisite for future preclinical and clinical interventions.

Enrichment of rare copy number variation in children with developmental language disorder

Developmental language disorder (DLD) is a common neurodevelopmental disorder with largely unknown etiology. Rare copy number variants (CNVs) have been implicated in the genetic architecture of other neurodevelopmental disorders (NDDs), which have led to clinical genetic testing recommendations for these disorders; however, the evidence is still lacking for DLD. We analyzed rare and de novo CNVs in 58 probands with severe DLD, their 159 family members and 76 Swedish typically developing children using high-resolution microarray. DLD probands had larger rare CNVs as measured by total length (P = .05), and average length (P = .04). In addition, the rate of rare CNVs overlapping coding genes was increased (P = .03 and P = .01) and in average more genes were affected (P = .006 and P = .03) in the probands and their siblings, respectively. De novo CNVs were found in 4.8% DLD probands (2/42) and 2.4% (1/42) siblings. Clinically significant CNVs or chromosomal anomalies were found in 6.9% (4/58) of the probands of which 2 carried 16p11.2 deletions. We provide further evidence that rare CNVs contribute to the etiology of DLD in loci that overlap with other NDDs. Based on our results and earlier literature, families with DLD should be offered molecular genetic testing as a routine in their clinical follow-up.

Prenatally diagnosed distal 16p11.2 microdeletion with a novel association with congenital diaphragmatic hernia: a case report

A prenatal case presenting with congenital diaphragmatic hernia (CDH) and distal 16p11.2 microdeletion suggests two possible causative hypotheses: (1) a functional effect of chromatin loopings between the distal and the proximal 16p11.2 microdeletion traits, associated with CHD; (2) a possible role of ATP2A1, a deleted gene involved in diaphragm development.