 using exome sequencing and a variant prioritisation strategy that focuses on loss - of - function variants , we identified biallelic , loss - of - function cep57 mutations as a cause of constitutional mosaic aneuploidies 
 . cep57 is a centrosomal protein and is involved in nucleating and stabilizing microtubules . 
 our data indicate that these and/or additional functions of cep57 are crucial in maintaining correct chromosomal number during cell division . 
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