Analysis of ASPM in an ethnically diverse cohort of 400 patient samples: perspectives of the molecular diagnostic laboratory

Primary Autosomal Recessive Microcephaly (MCPH) is characterized by congenital microcephaly usually without additional clinical findings. The most common gene implicated in MCPH is ASPM and a large percentage of mutations described have been homozygous and in consanguineous families primarily of East Asian and Middle Eastern origin. ASPM sequencing was performed on 400 patients between the years 2009 and 2012. Seventy of the patient samples were also analyzed for copy number changes in the ASPM gene. Forty protein truncating mutations, including 29 novel mutations, were identified in 39 patients with MCPH. Approximately one third of patients were compound heterozygotes, indicative of non-consanguinity in these patients. In addition, 46 non-synonymous variants were identified and interpreted as variants of uncertain significance. No deletion/duplication in ASPM was identified in the patients analyzed. A wide ethnic distribution was observed, including the first reported patients with ASPM-related MCPH of Hispanic descent. Clinical information was collected for 26 of the ASPM-positive patients and 41 of the ASPM-negative patients. As more individuals are identified with MCPH, we anticipate that we will continue to identify ASPM mutation-positive patients from all ethnic origins supporting the occurrence of this genetic condition beyond that of consanguineous families of certain ethnic populations.