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Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in communication, diminished social skills, and restrictive and repetitive behaviors and interests. ASD affects approximately 2.3% of the population and is highly heterogeneous, both phenotypically and genetically. As genomic technologies advance, our understanding of the genetic architecture of ASD is becoming clearer, encompassing spontaneous and inherited alterations throughout the genome, and delineating alterations that are either rare or common in the population. This commentary provides an overview of the genomic strategies and resulting major findings of genetic alterations associated with ASD.

Protein homeostasis is tightly regulated by the ubiquitin proteasome pathway. Disruption of this pathway gives rise to a host of neurological disorders. Through whole exome sequencing (WES) in families with neurodevelopmental disorders, we identified mutations in PSMD12, a core component of the proteasome, underlying a neurodevelopmental disorder with intellectual disability (ID) and features of autism spectrum disorder (ASD). We performed WES on six affected siblings from a multiplex family with ID and autistic features, the affected father, and two unaffected mothers, and a trio from a simplex family with one affected child with ID and periventricular nodular heterotopia. We identified an inherited heterozygous nonsense mutation in PSMD12 (NM_002816: c.367C>T: p.R123X) in the multiplex family and a de novo nonsense mutation in the same gene (NM_002816: c.601C>T: p.R201X) in the simplex family. PSMD12 encodes a non-ATPase regulatory subunit of the 26S proteasome. We confirm the association of PSMD12 with ID, present the first cases of inherited PSMD12 mutation, and demonstrate the heterogeneity of phenotypes associated with PSMD12 mutations.

We report on a six-generation Pakistani consanguineous family with autosomal recessive transmission of a form of hereditary nail dysplasia. Affected individuals presented with onycholysis of fingernails and anonychia of toenails. Associated abnormalities of ectodermal appendages were not observed in any of the affected individuals. Linkage has been established to chromosome 17q. A maximum multipoint analysis logarithm of the odds ratio score of 4.85 was obtained at marker D17S1301. Due to the consanguineous nature of this kindred, the gene for nail dysplasia is probably contained within a 5.0-cM (3 MB on the sequence-based physical map) region of homozygosity flanked by markers D17S1807 and D17S937.