Phenotypic features of 1q41q42 microdeletion including WDR26 and FBXO28 are clinically recognizable: The first case from Japan

Two Novel Variants of WDR26 in Chinese Patients with Intellectual Disability

Skraban-Deardorff syndrome is a rare autosomal dominant genetic disease caused by variants in the WDR26 gene. Here, we report two Chinese patients diagnosed with Skraban-Deardorff syndrome caused by novel de novo, heterozygous pathogenic WDR26 variants c.977delA (p. 12 N326Ifs*2) and c.1020-2A>G (p. R340Sfs*29). Their clinical features were characterized by intellectual disability (ID), developmental delay, abnormal facial features and the absence of early-onset seizure, which expands the phenotype spectrum associated with Skraban-Deardorff syndrome. By comparing our cases with current reported cases of WDR26-related intellectual disability, we suggest that developmental delay, particularly in speech, and facial features including rounded palpebral fissures, depressed nasal root, full nasal tip and abnormal gums, represent the prominent clinical phenotypes for diagnosis of Skraban-Deardorff syndrome. Together, WDR26 variants and 1q41q42 deletions should feature prominently on the differential diagnosis of ID with distinctive facial features.

Molecular cytogenetic characterization of a de novo chromosome 1q41-q42.11 microdeletion of paternal origin in a 15-year-old boy with mental retardation, developmental delay, autism and congenital heart defects

OBJECTIVE

We present molecular cytogenetic characterization of a de novo chromosome 1q41-q42.11 microdeletion of paternal origin in a mentally retarded child of a family requesting for genetic counseling of the future pregnancy.

CASE REPORT

A 43-year-old, gravida 1, para 1, woman, who had a 15-year-old son with mental retardation, planned to have another normal child and requested for genetic counseling of the future pregnancy. Her husband was 48 years old. The 15-year-old boy had a body height of 148 cm (<3rd centile) and a body weight of 40 Kg (<35th centile). He had facial dysmorphism, mental retardation, scoliosis, abnormal gaits, tetralogy of Fallot, pulmonary stenosis and autism but did not have any history of epilepsy. Cytogenetic analysis of the boy and the parents revealed normal karyotypes. Array comparative genomic hybridization (aCGH) analysis of the family revealed a de novo 2.028-Mb 1q41-q42.11 microdeletion, or arr 1q41q42.11 (222,571,596-224,599,234) × 1.0 [GRCh37 (hg19)], encompassing 13 Online Mendelian Inheritance in Man (OMIM) genes including DISP1, SUSD4, FBXO28, TP53BP2 and WDR26 in the child. Quantitative fluorescent polymerase chain reaction analysis confirmed a paternal origin of the deletion. Fluorescence in situ hybridization analysis confirmed a 1q41 deletion.

CONCLUSION

Genetic counseling of the parents who have a previous child with mental retardation and who wish to have another normal child in the future pregnancy should include genetic studies, and aCGH is useful under such a circumstance.

The Complement Regulator Susd4 Influences Nervous-System Function and Neuronal Morphology in Mice

The SUSD4 (Sushi domain-containing protein 4) gene encodes a complement inhibitor that is frequently deleted in 1q41q42 microdeletion syndrome, a multisystem congenital disorder that includes neurodevelopmental abnormalities. To understand SUSD4's role in the mammalian nervous system, we analyzed Susd4 knockout (KO) mice. Susd4 KO mice exhibited significant defects in motor performance and significantly higher levels of anxiety-like behaviors. Susd4 KO brain had abnormal “hairy” basket cells surrounding Purkinje neurons within the cerebellum and significantly reduced dendritic spine density in hippocampal pyramidal neurons. Neurons and oligodendrocyte lineage cells of wild-type mice were found to express Susd4 mRNA. Protein expression of the complement component C1q was increased in the brains of Susd4 KO mice. Our data indicate that SUSD4 plays an important role in neuronal functions, possibly via the complement pathway, and that SUSD4 deletion may contribute to the nervous system abnormalities in patients with 1q41q42 deletions.

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Susd4 is expressed in neurons and oligodendrocyte lineage cells

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Susd4 knockout mice have abnormal hippocampal and cerebellar neuronal morphologies

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Susd4 knockout mice exhibit anxiety-like behaviors and impaired motor function

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Susd4 knockout mice have elevated brain levels of the complement component C1q