Experiences and concerns of parents of children with a 16p11.2 deletion or duplication diagnosis: a reflexive thematic analysis

BACKGROUND

16p11.2 proximal deletion and duplication syndromes (Break points 4-5) (593KB, Chr16; 29.6-30.2mb - HG38) are observed to have highly varied phenotypes, with a known propensity for lifelong psychiatric problems. This study aimed to contribute to a research gap by qualitatively exploring the challenges families with 16p11.2 deletion and duplication face by answering three research questions: (1) What are parents' perceptions of the ongoing support needs of families with children who have 16p11.2 living in the UK?; (2) What are their experiences in trying to access support?; (3) In these regards, do the experiences of parents of children with duplication converge or vary from those of parents of children with 16p11.2 deletion?

METHODS

33 parents with children (aged 7-17 years) with 16p11.2 deletion or duplication participated in structured interviews, including the Autism Diagnostic Interview- Revised (ADI-R). Their answers to the ADI-R question 'what are your current concerns' were transcribed and subsequently analysed using Braun and Clarke's six step reflexive thematic analysis framework.

RESULTS

Three themes were identified: (1) Child is Behind Peers (subthemes: developmentally; academically; socially; emotionally); (2) Metabolism and Eating Patterns and; (3) Support (subthemes: insufficient support available; parent has to fight to access support; COVID-19 was a barrier to accessing support; 16p11.2 diagnosis can be a barrier to support, child is well-supported).

CONCLUSIONS

Parents of children with either 16p11.2 deletion or duplication shared similar experiences. However, metabolism concerns were specific to parents of children with 16p11.2 deletion. The theme Child is Behind Peers echoed concerns raised in previous Neurodevelopmental Copy Number Variant research. However, there were some key subthemes relating to research question (2) which were specific to this study. This included parents' descriptions of diagnostic overshadowing and the impact of a lack of eponymous name and scant awareness of 16p11.2.

Prenatal prevalence and postnatal manifestations of 16p11.2 deletions: A new insights into neurodevelopmental disorders based on clinical investigations combined with multi-omics analysis

BACKGROUND

The 16p11.2 deletion is one of the most common genetic aetiologies of neurodevelopmental disorders (NDDs). The prenatal phenotype of 16p11.2 deletion and the potential mechanism associated with postnatal clinical manifestations were largely unknow. We revealed the developmental trajectories of 16p11.2 deletion from the prenatal to postnatal periods and to identify key signaling pathways and candidate genes contributing to neurodevelopmental abnormalities.

METHODS

In this 5-y retrospective cohort study, women with singleton pregnancies who underwent amniocentesis for chromosomal abnormalities were included. Test of copy-number variations (CNVs) involved single nucleotide polymorphism-array and CNV-seq was performed to detected 16p11.2 deletion. For infants born carrying the 16p11.2 deletion, neurological and intellectual evaluations using the Chinese version of the Gesell Development Scale. For patients observed to have vertebral malformations, Sanger sequencing for T-C-A haplotype of TBX6 was performed. For those infants with clinical manifestations, whole-exome sequencing was consecutively performed in trios to rule out single-gene diseases, and transcriptomics combined with untargeted metabolomics were performed.

RESULTS

The prevalence of 16p11.2 deletion was 0.063% (55/86,035) in the prenatal period. Up to 80% (20/25) of the 16p11.2 deletions were proven de novo by parental confirmation. Approximately half of 16p11.2 deletions (28/55) were detected with prenatal abnormal ultrasound findings. Vertebral malformations were identified as the most distinctive structural malformations and were enriched in fetuses with 16p11.2 deletions compared with controls (90.9‰ [5/55] vs. 8.4‰ [72/85,980]; P < 0.001). All 5 fetuses with vertebral malformations were confirmed to have the TBX6 haplotype of T-C-A. Overall, 47.6% (10/21) infants birthed were diagnosed with NDDs of different degrees. Language impairment was the predominant manifestation (7/10; 70.0%), followed by motor delay (5/10; 50%). Multi-omics analysis indicated that MAPK3 was the central hub of the differentially expressed gene (DEG) network. We firstly reported that histidine-associated metabolism may be the core metabolic pathway related to the 16p11.2 deletion.

CONCLUSION

We demonstrated the prenatal presentation, incomplete penetrance and variable expressivity of the 16p11.2 deletion. We identified vertebral malformations were the most distinctive prenatal phenotypes, and language impairment was the predominant postnatal manifestation. Most of the 16p11.2 deletion was de novo. Meanwhile, we suggested that MAPK3 and histidine-associated metabolism may contribute to neurodevelopmental abnormalities of 16p11.2 deletion.

Recurrent human 16p11.2 microdeletions in type I Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome patients in Chinese Han population

BACKGROUNDS

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome, a severe congenital malformation of the female genital tract, is a highly heterogeneous disease which has no clear etiology. Previous studies have suggested that copy number variations (CNVs) and single-gene mutations might contribute to the development of MRKH syndrome. In particular, deletions in 16p11.2, which are suggested to be involved in several congenital diseases, have been reported in Chinese type II MRKH patients and European MRKH patients. However, few CNVs including 16p11.2 microdeletions were identified in Chinese type I MRKH cases although it accounted for the majority of MRKH patients in China. Thus, we conducted a retrospective study to identify whether CNVs at human chromosome 16p11.2 are risk factors of type I MRKH syndrome in the Chinese Han population.

METHODS

We recruited 143 patients diagnosed with type I MRKH between 2012 and 2014. Five hundred unrelated Chinese without congenital malformation were enrolled in control group, consisting of 197 from the 1000 Genomes Project and 303 from Fudan University. Quantitative PCR, array comparative genomic hybridization, and sanger sequencing were conducted to screen and verify candidate variant.

RESULTS

Our study identified recurrent 16p11.2 microdeletions of approximately 600 kb in two out of the 143 type I MRKH syndrome patients using high-density array-based comparative genomic hybridization (aCGH), while no 16p11.2 deletion was found in the control group. We did not find any mutations in TBX6 gene in our samples.

CONCLUSIONS

The results of the study identify 16p11.2 deletion in Chinese MRKH I patients for the first time, as well as support the contention that 16p11.2 microdeletions are associated with MRKH syndrome in both types across populations. It is suggested that 16p11.2 microdeletions should be included in molecular diagnosis and genetic counseling of female reproductive tract disorders.

Hypertension with hidden causes: the cognitive and behavioral profile of an adult female with chronic stress and 16p11.2 microdeletion

This case report aims to alert physicians to neuropsychological features and chromosomal variants that may underly resistant hypertension. We present a 35-year-old female patient with hypertensive crisis (BP 260/160 mmHg), initially treated with a combination of calcium antagonists, beta blockers, diuretics and angiotensin-converting enzyme (ACE)-inhibitors, though with little improvement. Cushing's syndrome, Conn's syndrome, and glucocorticoid receptor deficiency were ruled out. Multidisciplinary examination of medical history and (hetero)anamneses including psychosocial factors revealed mild dysmorphic body features, developmental delay, early diagnosis of autism spectrum disorder, a history of being bullied at school, little peer contact, learning disabilities, and special education. Neuropsychological assessment demonstrated below average to low average intelligence quotient, cognitive impairments, and psychopathology. Parallel genetic analyses revealed a rare 16p11.2 microdeletion syndrome. These concurrent examinations explained the patient's life-long high stress levels. After psychological treatment, with additional support at home, her blood pressure lowered to normal levels and antihypertensive drugs were no longer needed.

Day-to-day spontaneous social behaviours is quantitatively and qualitatively affected in a 16p11.2 deletion mouse model

Background

Autism spectrum disorders affect more than 1% of the population, impairing social communication and increasing stereotyped behaviours. A micro-deletion of the 16p11.2 BP4-BP5 chromosomic region has been identified in 1% of patients also displaying intellectual disabilities. In mouse models generated to understand the mechanisms of this deletion, learning and memory deficits were pervasive in most genetic backgrounds, while social communication deficits were only detected in some models.

Methods

To complement previous studies, we itemized the social deficits in the mouse model of 16p11.2 deletion on a hybrid C57BL/6N × C3H.Pde6b+ genetic background. We examined whether behavioural deficits were visible over long-term observation periods lasting several days and nights, to parallel everyday-life assessment of patients. We recorded the individual and social behaviours of mice carrying a heterozygous deletion of the homologous 16p11.2 chromosomic region (hereafter Del/+) and their wild-type littermates from both sexes over two or three consecutive nights during social interactions of familiar mixed-genotype quartets of males and of females, and of same-genotype unfamiliar female pairs.

Results

We observed that Del/+ mice of both sexes increased significantly their locomotor activity compared to wild-type littermates. In the social domain, Del/+ mice of both sexes displayed widespread deficits, even more so in males than in females in quartets of familiar individuals. In pairs, significant perturbations of the organisation of the social communication and behaviours appeared in Del/+ females.

Discussion

Altogether, this suggests that, over long recording periods, the phenotype of the 16p11.2 Del/+ mice was differently affected in the locomotor activity and the social domains and between the two sexes. These findings confirm the importance of testing models in long-term conditions to provide a comprehensive view of their phenotype that will refine the study of cellular and molecular mechanisms and complement pre-clinical targeted therapeutic trials.

16p11.2 haploinsufficiency reduces mitochondrial biogenesis in brain endothelial cells and alters brain metabolism in adult mice

Neurovascular abnormalities in mouse models of 16p11.2 deletion autism syndrome are reminiscent of alterations reported in murine models of glucose transporter deficiency, including reduced brain angiogenesis and behavioral alterations. Yet, whether cerebrovascular alterations in 16p11.2^df/+ mice affect brain metabolism is unknown. Here, we report that anesthetized 16p11.2^df/+ mice display elevated brain glucose uptake, a phenomenon recapitulated in mice with endothelial-specific 16p11.2 haplodeficiency. Awake 16p11.2^df/+ mice display attenuated relative fluctuations of extracellular brain glucose following systemic glucose administration. Targeted metabolomics on cerebral cortex extracts reveals enhanced metabolic responses to systemic glucose in 16p11.2^df/+ mice that also display reduced mitochondria number in brain endothelial cells. This is not associated with changes in mitochondria fusion or fission proteins, but 16p11.2^df/+ brain endothelial cells lack the splice variant NT-PGC-1α, suggesting defective mitochondrial biogenesis. We propose that altered brain metabolism in 16p11.2^df/+ mice is compensatory to endothelial dysfunction, shedding light on previously unknown adaptative responses.

16p11.2 deletion accelerates subpallial maturation and increases variability in human iPSC-derived ventral telencephalic organoids

Inhibitory interneurons regulate cortical circuit activity, and their dysfunction has been implicated in autism spectrum disorder (ASD). 16p11.2 microdeletions are genetically linked to 1% of ASD cases. However, few studies investigate the effects of this microdeletion on interneuron development. Using ventral telencephalic organoids derived from human induced pluripotent stem cells, we have investigated the effect of this microdeletion on organoid size, progenitor proliferation and organisation into neural rosettes, ganglionic eminence marker expression at early developmental timepoints, and expression of the neuronal marker NEUN at later stages. At early stages, deletion organoids exhibited greater variations in size with concomitant increases in relative neural rosette area and the expression of the ventral telencephalic marker COUPTFII, with increased variability in these properties. Cell cycle analysis revealed an increase in total cell cycle length caused primarily by an elongated G1 phase, the duration of which also varied more than normal. At later stages, deletion organoids increased their NEUN expression. We propose that 16p11.2 microdeletions increase developmental variability and may contribute to ASD aetiology by lengthening the cell cycle of ventral progenitors, promoting premature differentiation into interneurons.

Prenatally diagnosed 16p11.2 copy number variations by SNP Array: A retrospective case series

OBJECTIVE

The 16p11.2 copy number variations (CNVs) are increasingly recognized as one of the most frequent genomic disorders, with a broad spectrum of phenotypes. The fetal phenotype associated with 16p11.2 CNVs is poorly described. The current study presents prenatal series of 16p11.2 CNVs and provides a better understanding of this submicroscopic imbalance in prenatal diagnosis.

METHOD

Retrospective case series were extracted from a single tertiary referral center performing prenatal single nucleotide polymorphism (SNP) array from April 2017 to December 2021. The maternal demographics, indication for amniocentesis, ultrasound findings, SNP array results, inheritance of the CNVs, and pregnancy outcomes were studied.

RESULTS

We indentified 30 fetuses carrying 16p11.2 CNVs, representing 0.35% (30/8578) of prenatal SNP array results. The series included 17 fetuses with a proximal deletion, 7 with a distal deletion, 4 with a proximal duplication, and 2 with a distal duplication. Prenatal ultrasound anomalies were reported in 80% of these cases. The most common presentation was vertebralanomalies (9/30). Other features noted in more than one fetus were increased nuchal translucency/nuchal fold (NT/NF) (5/30), absent/hypoplastic nasal bone (3/30), polyhydramnios (3/30), ventricular septal defect (VSD) (2/30), unilateral mild ventriculomegaly (2/30), fetal growth restriction (FGR) (2/30), right aortic arch (2/30). All the 9 vertebralanomalies were present in fetuses harboring proximal deletion (9/17). Familial transmission was confirmed in 44% of cases (11/25) and termination of pregnancy was requested in 62.1% (18/29) of cases.

CONCLUSION

The 16p11.2 CNVs can have variable prenatal phenotypes and these CNVs are frequently inherited from parents with a milder or normal phenotype. Our results underline that vertebral deformities were frequent in cases of 16p11.2 proximal deletion, and further demonstrate the incomplete penetrance of the CNVs.

Histone Deacetylase Inhibition Restores Behavioral and Synaptic Function in a Mouse Model of 16p11.2 Deletion

BACKGROUND

Microdeletion of the human 16p11.2 gene locus confers risk for autism spectrum disorders and intellectual disability. How 16p11.2 deletion is linked to these neurodevelopmental disorders and whether there are treatment avenues for the manifested phenotypes remain to be elucidated. Emerging evidence suggests that epigenetic aberrations are strongly implicated in autism.

METHODS

We performed behavioral and electrophysiological experiments to examine the therapeutic effects of epigenetic drugs in transgenic mice carrying 16p11.2 deletion (16p11del/+).

RESULTS

We found that 16p11del/+ mice exhibited a significantly reduced level of histone acetylation in the prefrontal cortex (PFC). A short (3-day) treatment with class I histone deacetylase (HDAC) inhibitor MS-275 or Romidepsin led to the prolonged (3-4 weeks) rescue of social and cognitive deficits in 16p11del/+ mice. Concomitantly, MS-275 treatment reversed the hypoactivity of PFC pyramidal neurons and the hyperactivity of PFC fast-spiking interneurons. Moreover, the diminished N-methyl-D-aspartate (NMDA) receptor-mediated synaptic currents and the elevated GABAA receptor-mediated synaptic currents in PFC pyramidal neurons of 16p11del/+ mice were restored to control levels by MS-275 treatment.

CONCLUSIONS

Our results suggest that HDAC inhibition provides a highly effective therapeutic strategy for behavioral deficits and excitation/inhibition imbalance in 16p11del/+ mice, likely via normalization of synaptic function in the PFC.

Autism NPCs from both idiopathic and CNV 16p11.2 deletion patients exhibit dysregulation of proliferation and mitogenic responses

Neural precursor cell (NPC) dysfunction has been consistently implicated in autism. Induced pluripotent stem cell (iPSC)-derived NPCs from two autism groups (three idiopathic [I-ASD] and two 16p11.2 deletion [16pDel]) were used to investigate if proliferation is commonly disrupted. All five individuals display defects, with all three macrocephalic individuals (two 16pDel, one I-ASD) exhibiting hyperproliferation and the other two I-ASD subjects displaying hypoproliferation. NPCs were challenged with bFGF, and all hyperproliferative NPCs displayed blunted responses, while responses were increased in hypoproliferative cells. mRNA expression studies suggest that different pathways can result in similar proliferation phenotypes. Since 16pDel deletes MAPK3, P-ERK was measured. P-ERK is decreased in hyperproliferative but increased in hypoproliferative NPCs. While these P-ERK changes are not responsible for the phenotypes, P-ERK and bFGF response are inversely correlated with the defects. Finally, we analyzed iPSCs and discovered that 16pDel displays hyperproliferation, while idiopathic iPSCs were normal. These data suggest that NPC proliferation defects are common in ASD.

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NPC proliferation defects are common in idiopathic and 16p11.2 CNV-deletion ASD

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All macrocephalic I-ASD and 16pDel individuals have hyperproliferative NPCs

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NPC proliferative responses to bFGF correlate inversely with P-ERK levels

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Both NPCs and IPSCs derived from 16pDel individuals exhibit hyperproliferation

Effects of glucagon-like peptide-1 analogue treatment in genetic obesity: A case series

Obesity is highly prevalent and comes with serious health burden. In a minority, a genetic cause is present which often results in therapy-resistant obesity. Liraglutide is a glucagon-like peptide-1 (GLP-1) analogue, which has beneficial effects on satiety and weight in common obesity. We present the effects of GLP-1 analogues in adults with a molecularly proven genetic cause of their overweight or obesity. All patients were treated with liraglutide 3.0 mg daily, in addition to intensive supportive lifestyle treatment. Anthropometrics, metabolic parameters, resting energy expenditure (REE), side effects, and subjectively reported satiety and quality of life were assessed. Two patients with 16p11.2 deletion syndrome and two patients with heterozygous pathogenic melanocortin-4 receptor variants were treated. At baseline, their age ranged between 21 and 32 years and body mass index (BMI) ranged between 28.1 and 55.7 kg/m² . At follow-up (ranges 43 weeks-12 years), a mean change in BMI and waist circumference was observed of -5.7 ± 3.8 kg/m² and -15.2 ± 21.1 cm, respectively. All patients achieved ≥5% weight loss, three of them lost ≥10% of their body weight. All patients reported improved quality of life and three of them reported ameliorated satiety. Moreover, improvement of glycaemic control and dyslipidaemia were seen. In two patients, REE before and during treatment was measured, which either increased (+26% of predicted REE) or decreased (-18% of predicted REE). Two patients experienced mild side effects for a brief period. In conclusion, our case series shows beneficial effects of GLP-1 analogues on weight, metabolic parameters and quality of life in all four patients with genetic obesity.

Harnessing rare variants in neuropsychiatric and neurodevelopment disorders-a Keystone Symposia report

Neurodevelopmental neuropsychiatric disorders, such as autism spectrum disorder and schizophrenia, have strong genetic risk components, but the underlying mechanisms have proven difficult to decipher. Rare, high-risk variants may offer an opportunity to delineate the biological mechanisms responsible more clearly for more common idiopathic diseases. Indeed, different rare variants can cause the same behavioral phenotype, demonstrating genetic heterogeneity, while the same rare variant can cause different behavioral phenotypes, demonstrating variable expressivity. These observations suggest convergent underlying biological and neurological mechanisms; identification of these mechanisms may ultimately reveal new therapeutic targets. At the 2021 Keystone eSymposium "Neuropsychiatric and Neurodevelopmental Disorders: Harnessing Rare Variants" a panel of experts in the field described significant progress in genomic discovery and human phenotyping and raised several consistent issues, including the need for detailed natural history studies of rare disorders, the challenges in cohort recruitment, and the importance of viewing phenotypes as quantitative traits that are impacted by rare variants.

Structural and Lipidomic Alterations of Striatal Myelin in 16p11.2 Deletion Mouse Model of Autism Spectrum Disorder

Myelin abnormalities have been observed in autism spectrum disorder (ASD). In this study, we seek to discover myelin-related changes in the striatum, a key brain region responsible for core ASD features, using the 16p11.2 deletion (16p11.2±) mouse model of ASD. We found downregulated expression of multiple myelin genes and decreased myelin thickness in the striatum of 16p11.2± mice versus wild type controls. Moreover, given that myelin is the main reservoir of brain lipids and that increasing evidence has linked dysregulation of lipid metabolism to ASD, we performed lipidomic analysis and discovered decreased levels of certain species of sphingomyelin, hexosyl ceramide and their common precursor, ceramide, in 16p11.2± striatum, all of which are major myelin components. We further identified lack of ceramide synthase 2 as the possible reason behind the decrease in these lipid species. Taken together, our data suggest a role for myelin and myelin lipids in ASD development.

Overexpression of CD47 is associated with brain overgrowth and 16p11.2 deletion syndrome

Copy number variation (CNV) at the 16p11.2 locus is associated with neuropsychiatric disorders, such as autism spectrum disorder and schizophrenia. CNVs of the 16p gene can manifest in opposing head sizes. Carriers of 16p11.2 deletion tend to have macrocephaly (or brain enlargement), while those with 16p11.2 duplication frequently have microcephaly. Increases in both gray and white matter volume have been observed in brain imaging studies in 16p11.2 deletion carriers with macrocephaly. Here, we use human induced pluripotent stem cells (hiPSCs) derived from controls and subjects with 16p11.2 deletion and 16p11.2 duplication to understand the underlying mechanisms regulating brain overgrowth. To model both gray and white matter, we differentiated patient-derived iPSCs into neural progenitor cells (NPCs) and oligodendrocyte progenitor cells (OPCs). In both NPCs and OPCs, we show that CD47 (a "don't eat me" signal) is overexpressed in the 16p11.2 deletion carriers contributing to reduced phagocytosis both in vitro and in vivo. Furthermore, 16p11.2 deletion NPCs and OPCs up-regulate cell surface expression of calreticulin (a prophagocytic "eat me" signal) and its binding sites, indicating that these cells should be phagocytosed but fail to be eliminated due to elevations in CD47. Treatment of 16p11.2 deletion NPCs and OPCs with an anti-CD47 antibody to block CD47 restores phagocytosis to control levels. While the CD47 pathway is commonly implicated in cancer progression, we document a role for CD47 in psychiatric disorders associated with brain overgrowth.

Transcriptome analysis of human neural cells derived from isogenic embryonic stem cells with 16p11.2 deletion

16p11.2 deletion is one of the most influential copy number variations (CNVs) associated with autism spectrum disorder (ASD). Previous studies have investigated the pathophysiology of 16p11.2 deletion both in vitro and in vivo, and have identified features such as NMDAR dysfunction, excitation-inhibition imbalance, transcriptional dysregulation, and impaired cortical development. However, little is known about the transcriptional profiles of human neural cells. Here, we constructed an isogenic human embryonic stem (hES) cell model with 16p11.2 deletion using a CRISPR/Cas9 system and performed transcriptome analyses of hES-derived 2-dimensional neural cells. We identified several characteristics which may correlate with the neuropathology of 16p11.2 deletion: predisposition to differentiate into neural lineages, enhanced neurogenesis, and dysregulation of G protein-coupled receptor signaling and RAF/MAPK pathway. We also found upregulation of fragile X mental retardation protein (FMRP) target genes including GRM5, which is implicated as a common trait between 16p11.2 deletion and fragile X syndrome. Extending our knowledge into other ASD models would help us to understand the molecular pathology of this disorder.

Touch and olfaction/taste differentiate children carrying a 16p11.2 deletion from children with ASD

Background

Sensory processing atypicalities are frequent in Autism Spectrum Disorder (ASD) and neurodevelopmental disorders (NDD). Different domains of sensory processing appear to be differentially altered in these disorders. In this study, we explored the sensory profile of two clinical cohorts, in comparison with a sample of typically developing children.

Methods

Behavioral responses to sensory stimuli were assessed using the Sensory Processing Measure (parent-report questionnaire). We included 121 ASD children, 17 carriers of the 16p11.2 deletion (Del 16p11.2) and 45 typically developing (TD) children. All participants were aged between 2 and 12 years. Additional measures included the Tactile Defensiveness and Discrimination Test-Revised, Wechsler Intelligence Scales and Autism Diagnostic Observation Schedule (ADOS-2). Statistical analyses included MANCOVA and regression analyses.

Results

ASD children score significantly higher on all SPM subscales compared to TD. Del16p11.2 also scored higher than TD on all subscales except for tactile and olfactory/taste processing, in which they score similarly to TD. When assessing sensory modulation patterns (hyper-, hypo-responsiveness and seeking), ASD did not significantly differ from del16p11.2. Both groups had significantly higher scores across all patterns than the TD group. There was no significant association between the SPM Touch subscale and the TDDT-R.

Limitations

Sensory processing was assessed using a parent-report questionnaire. Even though it captures observable behavior, a questionnaire does not assess sensory processing in all its complexity. The sample size of the genetic cohort and the small subset of ASD children with TDDT-R data render some of our results exploratory. Divergence between SPM Touch and TDDT-R raises important questions about the nature of the process that is assessed.

Conclusions

Touch and olfaction/taste seem to be particularly affected in ASD children compared to del16p11.2. These results indicate that parent report measures can provide a useful perspective on behavioral expression. Sensory phenotyping, when combined with neurobiological and psychophysical methods, might have the potential to provide a better understanding of the sensory processing in ASD and in other NDD.

Rare Pathogenic Copy Number Variation in the 16p11.2 (BP4-BP5) Region Associated with Neurodevelopmental and Neuropsychiatric Disorders: A Review of the Literature

Copy number variants (CNVs) play an important role in the genetic underpinnings of neuropsychiatric/neurodevelopmental disorders. The chromosomal region 16p11.2 (BP4–BP5) harbours both deletions and duplications that are associated in carriers with neurodevelopmental and neuropsychiatric conditions as well as several rare disorders including congenital malformation syndromes. The aim of this article is to provide a review of the current knowledge of the diverse neurodevelopmental disorders (NDD) associated with 16p11.2 deletions and duplications reported in published cohorts. A literature review was conducted using the PubMed/MEDLINE electronic database limited to papers published in English between 1 January 2010 and 31 July 2020, describing 16p11.2 deletions and duplications carriers’ cohorts. Twelve articles meeting inclusion criteria were reviewed from the 75 articles identified by the search. Of these twelve papers, eight described both deletions and duplications, three described deletions only and one described duplications only. This study highlights the heterogeneity of NDD descriptions of the selected cohorts and inconsistencies concerning accuracy of data reporting.

Language characterization in 16p11.2 deletion and duplication syndromes

Expressive language impairment is one of the most frequently associated clinical features of 16p11.2 copy number variations (CNV). However, our understanding of the language profiles of individuals with 16p11.2 CNVs is still limited. This study builds upon previous work in the Simons Variation in Individuals Project (VIP, now known as Simons Searchlight), to characterize language abilities in 16p11.2 deletion and duplication carriers using comprehensive assessments. Participants included 110 clinically ascertained children and family members (i.e., siblings and cousins) with 16p11.2 BP4-BP5 deletion and 58 with 16p11.2 BP4-BP5 duplication between the ages of 2-23 years, most of whom were verbal. Regression analyses were performed to quantify variation in language abilities in the presence of the 16p11.2 deletion and duplication, both with and without autism spectrum disorder (ASD) and cognitive deficit. Difficulties in pragmatic skills were equally prevalent in verbal individuals in both deletion and duplication groups. NVIQ had moderate quantifiable effects on language scores in syntax and semantics/pragmatics (a decrease of less than 1 SD) for both groups. Overall, language impairments persisted even after controlling for ASD diagnosis and cognitive deficit. Language impairment is one of the core clinical features of individuals with 16p11.2 CNVs even in the absence of ASD and cognitive deficit. Results highlight the need for more comprehensive and rigorous assessment of language impairments to maximize outcomes in carriers of 16p11.2 CNVs.

Male-specific alterations in structure of isolation call sequences of mouse pups with 16p11.2 deletion

16p11.2 deletion is one of the most common gene copy variations that increases the susceptibility to autism and other neurodevelopmental disorders. This syndrome leads to developmental delays, including speech impairment and delays in expressive language and communication skills. To study developmental impairment of vocal communication associated with 16p11.2 deletion syndrome, we used the 16p11.2del mouse model and performed an analysis of pup isolation calls (PICs). The earliest PICs at postnatal day 5 from 16p11.2del pups were found altered in a male‐specific fashion relative to wild‐type (WT) pups. Analysis of sequences of ultrasonic vocalizations (USVs) emitted by pups using mutual information between syllables at different positions in the USV spectrograms showed that dependencies exist between syllables in WT mice of both sexes. The order of syllables was not random; syllables were emitted in an ordered fashion. The structure observed in the WT pups was identified and the pattern of syllable sequences was considered typical for the mouse line. However, typical patterns were totally absent in the 16p11.2del male pups, showing on average random syllable sequences, while the 16p11.2del female pups had dependencies similar to the WT pups. Thus, we found that PICs were reduced in number in male 16p11.2 pups and their vocalizations lack the syllable sequence order emitted by WT males and females and 16p11.2 females. Therefore, our study is the first to reveal sex‐specific perinatal communication impairment in a mouse model of 16p11.2 deletion and applies a novel, more granular method of analysing the structure of USVs.

Evaluating heterogeneity in ASD symptomatology, cognitive ability, and adaptive functioning among 16p11.2 CNV carriers

Individuals with 16p11.2 copy number variant (CNV) show considerable phenotypic heterogeneity. Although autism spectrum disorder (ASD) is reported in approximately 20-23% of individuals with 16p11.2 CNVs, ASD-associated symptoms are observed in those without a clinical ASD diagnosis. Previous work has shown that genetic variation and prenatal and perinatal birth complications influence ASD risk and symptom severity. This study examined the impact of genetic and environmental risk factors on phenotypic heterogeneity among 16p11.2 CNV carriers. Participants included individuals with a 16p11.2 deletion (N = 96) or duplication (N = 77) with exome sequencing from the Simons VIP study. The presence of prenatal factors, perinatal events, additional genetic events, and gender was studied. Regression analyses examined the contribution of each risk factor on ASD symptomatology, cognitive functioning, and adaptive abilities. For deletion carriers, perinatal and additional genetic events were associated with increased ASD symptomatology and decrements in cognitive and adaptive functioning. For duplication carriers, secondary genetic events were associated with greater cognitive impairments. Being female sex was a protective factor for both deletion and duplication carriers. Our findings suggest that ASD-associated risk factors contribute to the variability in symptom presentation in individuals with 16p11.2 CNVs. LAY SUMMARY: There are a wide range of autism spectrum disorder (ASD) symptoms and abilities observed for individuals with genetic changes of the 16p11.2 region. Here, we found perinatal complications contributed to more severe ASD symptoms (deletion carriers) and additional genetic mutations contributed to decreased cognitive abilities (deletion and duplication carriers). A potential protective factor was also observed for females with 16p11.2 variations. Autism Res 2020, 13: 1300-1310. © 2020 International Society for Autism Research, Wiley Periodicals, Inc.

Human and mouse studies establish TBX6 in Mendelian CAKUT and as a potential driver of kidney defects associated with the 16p11.2 microdeletion syndrome

Congenital anomalies of the kidney and urinary tract (CAKUTs) are the most common cause of chronic kidney disease in children. Human 16p11.2 deletions have been associated with CAKUT, but the responsible molecular mechanism remains to be illuminated. To explore this, we investigated 102 carriers of 16p11.2 deletion from multi-center cohorts, among which we retrospectively ascertained kidney morphologic and functional data from 37 individuals (12 Chinese and 25 Caucasian/Hispanic). Significantly higher CAKUT rates were observed in 16p11.2 deletion carriers (about 25% in Chinese and 16% in Caucasian/Hispanic) than those found in the non-clinically ascertained general populations (about 1/1000 found at autopsy). Furthermore, we identified seven additional individuals with heterozygous loss-of-function variants in TBX6, a gene that maps to the 16p11.2 region. Four of these seven cases showed obvious CAKUT. To further investigate the role of TBX6 in kidney development, we engineered mice with mutated Tbx6 alleles. The Tbx6 heterozygous null (i.e., loss-of-function) mutant (Tbx6^+/‒) resulted in 13% solitary kidneys. Remarkably, this incidence increased to 29% in a compound heterozygous model (Tbx6^mh/‒) that reduced Tbx6 gene dosage to below haploinsufficiency, by combining the null allele with a novel mild hypomorphic allele (mh). Renal hypoplasia was also frequently observed in these Tbx6-mutated mouse models. Thus, our findings in patients and mice establish TBX6 as a novel gene involved in CAKUT and its gene dosage insufficiency as a potential driver for kidney defects observed in the 16p11.2 microdeletion syndrome.

Novel and de novo point and large microdeletion mutation in PRRT2-related epilepsy

BACKGROUND

Point and copy number variant mutations in the PRRT2 gene have been identified in a variety of paroxysmal disorders and different types of epilepsy. In this study, we analyzed the phenotypes and PRRT2-related mutations in Chinese epilepsy children.

METHODS

A total of 492 children with epilepsy were analyzed by whole exome sequencing (WES) and low-coverage massively parallel CNV sequencing (CNV-seq) to find the single nucleotide variants and copy number variations (CNVs). And quantitative polymerase chain reaction was utilized to verify the CNVs. Their clinical information was followed up.

RESULTS

We found PRRT2-related mutations in 19 patients (10 males and nine females, six sporadic cases and 13 family cases). Twelve point mutations, four whole gene deletion, and three 16p11.2 deletions were detected. The clinical features of 39 patients in 19 families included one early childhood myoclonic epilepsy (ECME), one febrile seizure (FS), two infantile convulsions with paroxysmal choreoathetosis (ICCA), six paroxysmal kinesigenic dyskinesias (PKD), 12 benign infantile epilepsy (BIE), and 17 benign familial infantile epilepsy (BFIE). All patients had normal brain MRI. Interictal EEG showed only one patient had generalized polyspike wave and five patients had focal transient discharges. Focal seizures originating in the frontal region were recorded in one patient, two from the temporal region, and two from the occipital region. Most patients were treated effectively with VPA or OXC, and the child with myoclonic seizures was not sensitive to antiepileptic drugs.

CONCLUSION

PRRT2 mutations can be inherited or de novo, mainly inherited. The clinical spectrum of PRRT2 mutation includes BIE, BFIE, ICCA, PKD, FS, and ECME. The PRRT2-related mutations contained point mutation, whole gene deletion and 16p11.2 deletions, and large microdeletion mutations mostly de novo. It is the first report of PRRT2 mutation found in ECME. Our report expands the mutation and clinical spectrum of PRRT2-related epilepsy.

Abnormal Auditory Mismatch Fields in Children and Adolescents With 16p11.2 Deletion and 16p11.2 Duplication

BACKGROUND

Individuals with either deletion or duplication of the BP4-BP5 segment of chromosome 16p11.2 have varied behavioral phenotypes that may include autistic features, mild to moderate intellectual disability, and/or language impairment. However, the neurophysiological correlates of auditory language discrimination processing in individuals with 16p11.2 deletion and 16p11.2 duplication have not been investigated.

METHODS

Magnetoencephalography was used to measure magnetic mismatch fields (MMFs) arising from the left and right superior temporal gyrus during an auditory oddball paradigm with vowel stimuli (/a/ and /u/) in children and adolescents with 16p11.2 deletion or 16p11.2 duplication and in typically developing peers. One hundred twenty-eight participants ranging from 7 to 17 years of age were included in the final analysis (typically developing: n = 61, 12.08 ± 2.50 years of age; 16p11.2 deletion: n = 45, 11.28 ± 2.51 years of age; and 16p11.2 duplication: n = 22, 10.73 ± 2.49 years of age).

RESULTS

Delayed MMF latencies were found in both 16p11.2 deletion and 16p11.2 duplication groups compared with typically developing subjects. In addition, these delayed MMF latencies were associated with language and cognitive ability, with prolonged latency predicting greater impairment.

CONCLUSIONS

Our findings suggest that auditory MMF response delays are associated with clinical severity of language and cognitive impairment in individuals with either 16p11.2 deletion or 16p11.2 duplication, indicating a correlate of their shared/overlapping behavioral phenotype (and not a correlate of gene dosage).

Altered structural brain connectivity involving the dorsal and ventral language pathways in 16p11.2 deletion syndrome

Copy number variants at the chromosomal locus 16p11.2 contribute to neurodevelopmental disorders such as autism spectrum disorders, epilepsy, schizophrenia, and language and articulation disorders. Here, we provide detailed findings on the disrupted structural brain connectivity in 16p11.2 deletion syndrome (patients: N = 21, age range: 8-16 years; typically developing (TD) controls: 18, 9-16 years) using structural and diffusion MRI. We performed global short-, middle-, long-range, and interhemispheric connectivity analysis in the whole brain using gyral topology-based cortical parcellation. Using region of interest analysis, we studied bilateral dorsal (3 segments of arcuate fasciculus (AF)) and ventral (inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), uncinate fasciculus (UF)) language pathways. Our results showed significantly increased axial (AD) and radial (RD) diffusivities in bilateral anterior AF, decreased volume for left long AF, increased mean diffusivity (MD) and RD for right long AF, and increased AD for bilateral UF in the 16p11.2 deletion group in the absence of significant abnormalities in the whole-brain gyral and interhemispheric connectivity. The selective involvement of the language networks may aid in understanding effects of altered white matter connectivity on neurodevelopmental outcomes in 16p11.2 deletion.

16p11.2 deletion in patients with paroxysmal kinesigenic dyskinesia but without intellectual disability

INTRODUCTION

Mutations of the PRRT2 gene are the most common cause for paroxysmal kinesigenic dyskinesia. However, patients with negative PRRT2 mutations are not rare. The aim of this study is to determine whether copy number variant of PRRT2 gene is another potential pathogenic mechanism in the patients with paroxysmal kinesigenic dyskinesia with negative PRRT2 point and frameshift mutations.

METHODS

We screened PRRT2 copy number variants using the AccuCopy™ method in 29 patients with paroxysmal kinesigenic dyskinesia with negative PRRT2 point and frameshift mutations. Next-generation sequencing was used to determine the chromosomal deletion sites in patients with PRRT2 copy number variants, and to exclude mutations in other known causative genes for paroxysmal kinesigenic dyskinesia.

RESULTS

Two sporadic patients with negative PRRT2 point and frameshift mutations (6.9%) were identified to have de novo PRRT2 copy number deletions (591 and 832 Kb deletions located in 16p11.2). The two patients presented with pure paroxysmal kinesigenic dyskinesia and paroxysmal kinesigenic dyskinesia and benign infantile convulsions, respectively. They had normal intelligence and neuropsychiatric development, in contrast to those previously reported with 16p11.2 deletions complicated with neuropsychiatric disorders. No correlation between the deletion ranges and phenotypic variations was found.

CONCLUSION

16p11.2 deletions play causative roles in paroxysmal kinesigenic dyskinesia, especially for sporadic cases. Our findings extend the phenotype of 16p11.2 deletions to pure paroxysmal kinesigenic dyskinesia. Screening for 16p11.2 deletions should thus be included in genetic evaluations for patients with paroxysmal kinesigenic dyskinesia.

Rare variants in the genetic background modulate cognitive and developmental phenotypes in individuals carrying disease-associated variants

Purpose

To assess the contribution of rare variants in the genetic background toward variability of neurodevelopmental phenotypes in individuals with rare copy-number variants (CNVs) and gene-disruptive variants.

Methods

We analyzed quantitative clinical information, exome sequencing, and microarray data from 757 probands and 233 parents and siblings who carry disease-associated variants.

Results

The number of rare likely deleterious variants in functionally intolerant genes (“other hits”) correlated with expression of neurodevelopmental phenotypes in probands with 16p12.1 deletion (n=23, p=0.004) and in autism probands carrying gene-disruptive variants (n=184, p=0.03) compared with their carrier family members. Probands with 16p12.1 deletion and a strong family history presented more severe clinical features (p=0.04) and higher burden of other hits compared with those with mild/no family history (p=0.001). The number of other hits also correlated with severity of cognitive impairment in probands carrying pathogenic CNVs (n=53) or de novo pathogenic variants in disease genes (n=290), and negatively correlated with head size among 80 probands with 16p11.2 deletion. These co-occurring hits involved known disease-associated genes such as SETD5, AUTS2, and NRXN1, and were enriched for cellular and developmental processes.

Conclusion

Accurate genetic diagnosis of complex disorders will require complete evaluation of the genetic background even after a candidate disease-associated variant is identified.

Chemogenetic Activation of Prefrontal Cortex Rescues Synaptic and Behavioral Deficits in a Mouse Model of 16p11.2 Deletion Syndrome

Microdeletion of the human 16p11.2 gene locus has been linked to autism spectrum disorder (ASD) and intellectual disability and confers risk for a number of other neurodevelopmental deficits. Transgenic mice carrying 16p11.2 deletion (16p11^+/-) display phenotypes reminiscent of those in human patients with 16p11.2 deletion syndrome, but the molecular mechanisms and treatment strategies for these phenotypes remain unknown. In this study, we have found that both male and female 16p11^+/- mice exhibit deficient NMDA receptor (NMDAR) function in the medial prefrontal cortex (mPFC), a brain region critical for high-level "executive" functions. Elevating the activity of mPFC pyramidal neurons with a CaMKII-driven Gq-DREADD (Gq-coupled designer receptors exclusively activated by designer drugs) led to the significant increase of NR2B subunit phosphorylation and the restoration of NMDAR function, as well as the amelioration of cognitive and social impairments in 16p11^+/- mice. These results suggest that NMDAR hypofunction in PFC may contribute to the pathophysiology of 16p11.2 deletion syndrome and that restoring PFC activity is sufficient to rescue the behavioral deficits.SIGNIFICANCE STATEMENT The 16p11.2 deletion syndrome is strongly associated with autism spectrum disorder and intellectual disability. Using a mouse model carrying the 16p11.2 deletion, 16p11^+/-, we identified NMDA receptor hypofunction in the prefrontal cortex (PFC). Elevating the activity of PFC pyramidal neurons with a chemogenetic tool, Gq-DREADD, led to the restoration of NMDA receptor function and the amelioration of cognitive and social impairments in 16p11^+/- mice. These results have revealed a novel route for potential therapeutic intervention of 16p11.2 deletion syndrome.

Benign infantile seizures followed by autistic regression in a boy with 16p11.2 deletion

Benign infantile seizures (BIS) are usually a self-limiting condition, which may be associated with heterozygous mutations in the PRRT2 gene at chromosome 16p11.2. Here, we report a boy with a deletion in 16p11.2, presenting with BIS and typical neurodevelopment in the first year of life, unexpectedly followed by severe autistic regression. 16p11.2 deletions are typically associated with intellectual disability, autism, and language disorders, and only rarely with BIS. This clinical report shows that the neurodevelopmental prognosis in BIS patients may not always be benign, and suggests that array CGH screening should be considered for affected infants in order to rule out deletions at 16p11.2 and long-term clinical follow-up.

Longitudinal report of child with de novo 16p11.2 triplication

16p11.2 deletions and duplications are commonly associated with autism spectrum disorder and linked to mirrored phenotypes of physical characteristics and higher penetrance for deletions. A male with a rare 16p11.2 triplication demonstrated a similar phenotypic presentation to deletion carriers with neurocognitive and adaptive skill deficits and above‐average physical growth.

Developmental trajectories for young children with 16p11.2 copy number variation

Copy number variation at 16p11.2 is associated with diverse phenotypes but little is known about the early developmental trajectories and emergence of the phenotype. This longitudinal study followed 56 children with the 16p11.2 BP4-BP5 deletion or duplication between the ages of 6 months and 8 years with diagnostic characterization and dimensional assessment across cognitive, adaptive, and behavioral domains. Linear mixed modeling revealed distinct developmental trajectories with deletions showing VIQ gains but declines in motor and social abilities while duplications showed VIQ gains and steady development across other domains. Nonparametric analyses suggest distinct trajectories and early cognitive abilities for deletion carriers who are ultimately diagnosed with intellectual disability and developmental coordination disorder as well as distinct trajectories and early social communication and cognitive abilities for duplication carriers diagnosed with ASD and intellectual disability. Findings provide predictions for patient developmental trajectories, insight into mean functioning of individuals with 16p11.2 at early ages, and highlight the need for ongoing monitoring of social and motor functioning and behavioral symptomatology to improve treatment planning. © 2017 Wiley Periodicals, Inc.

Compound Heterozygosity for Null Mutations and a Common Hypomorphic Risk Haplotype in TBX6 Causes Congenital Scoliosis

Congenital scoliosis (CS) occurs as a result of vertebral malformations and has an incidence of 0.5-1/1,000 births. Recently, TBX6 on chromosome 16p11.2 was reported as a disease gene for CS; about 10% of Chinese CS patients were compound heterozygotes for rare null mutations and a common haplotype defined by three SNPs in TBX6. All patients had hemivertebrae. We recruited 94 Japanese CS patients, investigated the TBX6 locus for both mutations and the risk haplotype, examined transcriptional activities of mutant TBX6 in vitro, and evaluated clinical and radiographic features. We identified TBX6 null mutations in nine patients, including a missense mutation that had a loss of function in vitro. All had the risk haplotype in the opposite allele. One of the mutations showed dominant negative effect. Although all Chinese patients had one or more hemivertebrae, two Japanese patients did not have hemivertebra. The compound heterozygosity of null mutations and the common risk haplotype in TBX6 also causes CS in Japanese patients with similar incidence. Hemivertebra was not a specific type of spinal malformation in TBX6-associated CS (TACS). A heterozygous TBX6 loss-of-function mutation has been reported in a family with autosomal-dominant spondylocostal dysostosis, but it may represent a spectrum of the same disease with TACS.

Hyperactivity and male-specific sleep deficits in the 16p11.2 deletion mouse model of autism

Sleep disturbances and hyperactivity are prevalent in several neurodevelopmental disorders, including autism spectrum disorders (ASDs) and attention deficit-hyperactivity disorder (ADHD). Evidence from genome-wide association studies indicates that chromosomal copy number variations (CNVs) are associated with increased prevalence of these neurodevelopmental disorders. In particular, CNVs in chromosomal region 16p11.2 profoundly increase the risk for ASD and ADHD, disorders that are more common in males than females. We hypothesized that mice hemizygous for the 16p11.2 deletion (16p11.2 del/+) would exhibit sex-specific sleep and activity alterations. To test this hypothesis, we recorded activity patterns using infrared beam breaks in the home-cage of adult male and female 16p11.2 del/+ and wildtype (WT) littermates. In comparison to controls, we found that both male and female 16p11.2 del/+ mice exhibited robust home-cage hyperactivity. In additional experiments, sleep was assessed by polysomnography over a 24-hr period. 16p11.2 del/+ male, but not female mice, exhibited significantly more time awake and significantly less time in non-rapid-eye-movement (NREM) sleep during the 24-hr period than wildtype littermates. Analysis of bouts of sleep and wakefulness revealed that 16p11.2 del/+ males, but not females, spent a significantly greater proportion of wake time in long bouts of consolidated wakefulness (greater than 42 min in duration) compared to controls. These changes in hyperactivity, wake time, and wake time distribution in the males resemble sleep disturbances observed in human ASD and ADHD patients, suggesting that the 16p11.2 del/+ mouse model may be a useful genetic model for studying sleep and activity problems in human neurodevelopmental disorders. Autism Res 2016. © 2016 International Society for Autism Research, Wiley Periodicals, Inc. Autism Res 2017, 10: 572-584. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

Abnormal auditory and language pathways in children with 16p11.2 deletion

Copy number variations at chromosome 16p11.2 contribute to neurodevelopmental disorders, including autism spectrum disorder (ASD). This study seeks to improve our understanding of the biological basis of behavioral phenotypes common in ASD, in particular the prominent and prevalent disruption of spoken language seen in children with the 16p11.2 BP4–BP5 deletion. We examined the auditory and language white matter pathways with diffusion MRI in a cohort of 36 pediatric deletion carriers and 45 age-matched controls. Diffusion MR tractography of the auditory radiations and the arcuate fasciculus was performed to generate tract specific measures of white matter microstructure. In both tracts, deletion carriers exhibited significantly higher diffusivity than that of controls. Cross-sectional diffusion parameters in these tracts changed with age with no group difference in the rate of maturation. Within deletion carriers, the left-hemisphere arcuate fasciculus mean and radial diffusivities were significantly negatively correlated with clinical language ability, but not non-verbal cognitive ability. Diffusion metrics in the right-hemisphere arcuate fasciculus were not predictive of language ability. These results provide insight into the link between the 16p11.2 deletion, abnormal auditory and language pathway structures, and the specific behavioral deficits that may contribute to neurodevelopmental disorders such as ASD.

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We examined auditory and language white matter tracts in children with the 16p11.2 BP4–BP5 deletion.

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Diffusivity was enhanced in auditory radiation and arcuate fasciculus.

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Arcuate fasciculus microstructure was correlated with language ability in deletion carriers.

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There are correlations in the brain structure and behavioral phenotype in the 16p11.2 deletion carriers.

Inherited 1q21.1q21.2 duplication and 16p11.2 deletion: a two-hit case with more severe clinical manifestations

We report paternally inherited duplication of 1q12q21.2 of 5.8 Mb associated with maternally inherited deletion of 16p11.2 of 545 Kb, this latter first identified in a fetus exhibiting an absent nasal bone detected during pregnancy. During the neonatal period, the young boy presented developmental delay, epilepsy, congenital anomalies and overweight. The clinical features of the proband with two rearrangements were more severe than in either of the parents carrying only one or the other mutation. Thus our data support a two-hit model in which the concomitant presence of these two copy-number variations exacerbates the neurodevelopmental phenotype.

16p11.2 Deletion Syndrome Mice Display Sensory and Ultrasonic Vocalization Deficits During Social Interactions

Recurrent deletions and duplications at chromosomal region 16p11.2 are variably associated with speech delay, autism spectrum disorder, developmental delay, schizophrenia, and cognitive impairments. Social communication deficits are a primary diagnostic symptom of autism. Here we investigated ultrasonic vocalizations (USVs) in young adult male 16p11.2 deletion mice during a novel three-phase male-female social interaction test that detects vocalizations emitted by a male in the presence of an estrous female, how the male changes its calling when the female is suddenly absent, and the extent to which calls resume when the female returns. Strikingly fewer vocalizations were detected in two independent cohorts of 16p11.2 heterozygous deletion males (+/-) during the first exposure to an unfamiliar estrous female, as compared to wildtype littermates (+/+). When the female was removed, +/+ emitted calls, but at a much lower level, whereas +/- males called minimally. Sensory and motor abnormalities were detected in +/-, including higher nociceptive thresholds, a complete absence of acoustic startle responses, and hearing loss in all +/- as confirmed by lack of auditory brainstem responses to frequencies between 8 and 100 kHz. Stereotyped circling and backflipping appeared in a small percentage of individuals, as previously reported. However, these sensory and motor phenotypes could not directly explain the low vocalizations in 16p11.2 deletion mice, since (a) +/- males displayed normal abilities to emit vocalizations when the female was subsequently reintroduced, and (b) +/- vocalized less than +/+ to social odor cues delivered on an inanimate cotton swab. Our findings support the concept that mouse USVs in social settings represent a response to social cues, and that 16p11.2 deletion mice are deficient in their initial USVs responses to novel social cues.

An overview of mongenic and syndromic obesities in humans

Obesity is increasing in prevalence in the United States with over 65% of adults considered overweight and 16% of children with BMI > 95 percentile. The heritability of obesity is estimated between 40% and 70%, but the genetics of obesity for most individuals are complex and involve the interaction of multiple genes and environment. There are however several syndromic and non-syndromic forms of obesity that are monogenic and oligogenic that provide insight into the underlying molecular control of food intake and the neural networks that control ingestive behavior and satiety to regulate body weight and which may interact with treatment exposures to produce or exacerbate obesity in childhood cancer survivors.