CC2D1A causes ciliopathy, intellectual disability, heterotaxy, renal dysplasia, and abnormal CSF flow.

Intellectual and developmental disabilities result from abnormal nervous system development. Over a 1,000 genes have been associated with intellectual and developmental disabilities, driving continued efforts toward dissecting variant functionality to enhance our understanding of the disease mechanism. This report identified two novel variants in CC2D1A in a cohort of four patients from two unrelated families. We used multiple model systems for functional analysis, including Xenopus, Drosophila, and patient-derived fibroblasts. Our experiments revealed that cc2d1a is expressed explicitly in a spectrum of ciliated tissues, including the left-right organizer, epidermis, pronephric duct, nephrostomes, and ventricular zone of the brain. In line with this expression pattern, loss of cc2d1a led to cardiac heterotaxy, cystic kidneys, and abnormal CSF circulation via defective ciliogenesis. Interestingly, when we analyzed brain development, mutant tadpoles showed abnormal CSF circulation only in the midbrain region, suggesting abnormal local CSF flow. Furthermore, our analysis of the patient-derived fibroblasts confirmed defective ciliogenesis, further supporting our observations. In summary, we revealed novel insight into the role of CC2D1A by establishing its new critical role in ciliogenesis and CSF circulation.

Anemia and thrombocytopenia due to a novel BRPF1 variant in a family from Çanakkale with intellectual disability and dysmorphic facies: Case report and review of the literature.

Intellectual developmental disorder with dysmorphic facies and ptosis (IDDDFP) (MIM#617333) is an autosomal dominant disorder characterized by delayed psychomotor development, intellectual disability (ID), and dysmorphic facial features due to pathogenic variations in the Bromodomain- and PHD Finger-Containing Protein (BRPF1) (MIM#602410) gene. Herein, we report the first Turkish patients with IDDDFP. Additionally, the patients had hematopoietic disorders such as anemia and thrombocytopenia, which have not been previously described in IDDDFP patients. Genetic testing using Whole Exome Sequencing (WES) revealed a novel heterozygous c.1433G > A; p.W478* (NM_004634.3) pathogenic variant on exon 3 of the BRPF1 gene. The patients demonstrated classical features of IDDDFP such as intellectual disability, developmental delay, ptosis, micro and retrognathia, and dysmorphic facial features, in addition to the anemia and thrombocytopenia. Apart from the variant in BRPF1, no additional genomic changes were detected by WES and chromosomal microarray analysis (CMA). Hopefully, our novel report on the hematopoietic anomalies of our patients due to BRPF1 will expand upon the clinical spectrum of IDDDFP, encourage further studies about BRPF1-hematopoietic system relations, and affect the diagnostic and therapeutic schemes of hematopoietic system disorders.