Prospective and detailed behavioral phenotyping in DDX3X syndrome

Abstract Background DDX3X syndrome is a recently identified genetic disorder that accounts for 1–3% of cases of unexplained developmental delay and/or intellectual disability (ID) in females, and is associated with motor and language delays, and autism spectrum disorder (ASD). To date, the published phenotypic characterization of this syndrome has primarily relied on medical record review; in addition, the behavioral dimensions of the syndrome have not been fully explored. Methods We carried out multi-day, prospective, detailed phenotyping of DDX3X syndrome in 14 females and 1 male, focusing on behavioral, psychological, and neurological measures. Three participants in this cohort were previously reported with limited phenotype information and were re-evaluated for this study. We compared results against population norms and contrasted phenotypes between individuals harboring either (1) protein-truncating variants or (2) missense variants or in-frame deletions. Results Eighty percent (80%) of individuals met criteria for ID, 60% for ASD and 53% for attention-deficit/hyperactivity disorder (ADHD). Motor and language delays were common as were sensory processing abnormalities. The cohort included 5 missense, 3 intronic/splice-site, 2 nonsense, 2 frameshift, 2 in-frame deletions, and one initiation codon variant. Genotype–phenotype correlations indicated that, on average, missense variants/in-frame deletions were associated with more severe language, motor, and adaptive deficits in comparison to protein-truncating variants. Limitations Sample size is modest, however, DDX3X syndrome is a rare and underdiagnosed disorder. Conclusion This study, representing a first, prospective, detailed characterization of DDX3X syndrome, extends our understanding of the neurobehavioral phenotype. Gold-standard diagnostic approaches demonstrated high rates of ID, ASD, and ADHD. In addition, sensory deficits were observed to be a key part of the syndrome. Even with a modest sample, we observe evidence for genotype–phenotype correlations with missense variants/in-frame deletions generally associated with more severe phenotypes.

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Prospective and detailed behavioral phenotyping in DDX3X syndrome

10.1101/2021.01.26.21250125 ◽

2021 ◽

Author(s):

Lara Tang ◽

Tess Levy ◽

Sylvia Guillory ◽

Danielle Halpern ◽

Jessica Zweifach ◽

...

Keyword(s):

Genetic Disorder ◽

Autism Spectrum ◽

Phenotypic Characterization ◽

Language Delays ◽

Missense Variants ◽

Variant Genotype ◽

Diagnostic Approaches ◽

Intronic Splice Site ◽

Record Review

ABSTRACTBackgroundDDX3X syndrome is a recently identified genetic disorder that accounts for 1-3% of cases of unexplained developmental delay (DD) and/or intellectual disability (ID) in females and is associated with motor and language delays, and autism spectrum disorder (ASD). To date, the published phenotypic characterization of this syndrome has primarily relied on medical record review; in addition, the behavioral dimensions of the syndrome have not been fully explored.MethodsWe carried out multi-day, prospective, detailed phenotyping of DDX3X syndrome in 14 females and 1 male, focusing on behavioral, psychological, and neurological measures; three participants in this cohort have been previously reported. We compared results against population norms and contrasted phenotypes between individuals harboring either (i) protein-truncating variants or (ii) missense variants and in-frame deletions.ResultsEighty percent of individuals met criteria for ID, 60% for ASD and 53% for attention-deficit/hyperactivity disorder (ADHD). Motor and language delays were common as were sensory processing abnormalities. The cohort included 5 missense, 3 intronic/splice-site, 2 nonsense, 2 frameshift, 2 in-frame deletions, and one initiation codon variant. Genotype-phenotype correlations indicated that missense variants/in-frame deletions were associated with more severe language, motor, and adaptive deficits in comparison to protein-truncating variants.LimitationsSample size is modest, however, DDX3X is a rare and underdiagnosed disorder.ConclusionThis study, representing a first, prospective, detailed characterization of DDX3X syndrome, extends our understanding of the neurobehavioral phenotype. Gold-standard diagnostic approaches demonstrated high rates of ID, ASD, and ADHD. In addition, sensory deficits were observed to be a key part of the syndrome. Even with a modest sample, we observe evidence for genotype-phenotype correlations with missense variants/in-frame deletions yielding a more severe phenotype.

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Generation and characterization of Ccdc28b mutant mice links the Bardet-Biedl associated gene with social behavioral phenotypes

10.1101/2021.10.21.465251 ◽

2021 ◽

Author(s):

Matías Fabregat ◽

Sofía Niño ◽

Sabrina Pose ◽

Magdalena Cárdenas-Rodríguez ◽

Corrine Smolen ◽

...

Keyword(s):

Coiled Coil ◽

Causal Link ◽

Autism Spectrum ◽

Phenotypic Characterization ◽

Murine Models ◽

Phenotypic Analysis ◽

Behavioral Phenotypes ◽

Mild Phenotype ◽

Bardet Biedl Syndrome

CCDC28B (coiled-coil domain-containing protein 28B) was identified as a modifier in the ciliopathy Bardet-Biedl syndrome (BBS). Our previous work in cells and zebrafish showed that CCDC28B plays a role regulating cilia length in a mechanism that is not completely understood. Here we report the generation of a Ccdc28b mutant mouse using CRISPR/Cas9 (Ccdc28b mut). After confirming the depletion of Ccdc28b ;we performed a phenotypic characterization showing that Ccdc28b mut animals present a mild phenotype: i) do not present clear structural cilia affectation, although we did observe mild defects in cilia density and cilia length in some tissues, ii) reproduce normally, and iii) do not develop retinal degeneration or obesity, two hallmark features of reported BBS murine models. In contrast, Ccdc28b mut mice did show clear social interaction defects as well as stereotypical behaviors suggestive of autism spectrum disorder (ASD). This finding is indeed relevant regarding CCDC28B as a modifier of BBS since behavioral phenotypes have been documented in BBS. Importantly however, our data suggests a possible causal link between CCDC28B and ASD-like phenotypes that exceeds the context of BBS: filtering for rare deleterious variants, we found CCDC28B mutations in eight probands from the Simmons Simplex Collection cohort. Furthermore, a phenotypic analysis showed that CCDC28B mutation carriers present lower BMI and mild communication defects compared to a randomly selected sample of SSC probands. Thus, our results suggest that mutations in CCDC28B lead to mild autism-like features in mice and humans. Overall, this work reports a novel mouse model that will be key to continue evaluating genetic interactions in BBS, deciphering the contribution of CCDC28B to modulate the presentation of BBS phenotypes. In addition, our data underscores a novel link between CCDC28B and ASD-like phenotypes, providing a novel opportunity to further our understanding of the genetic, cellular, and molecular basis of ASD.

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