Genetic insights into childhood-onset schizophrenia: The yield of clinical exome sequencing.

Childhood-onset schizophrenia (COS) is a rare form of schizophrenia with an onset prior to 13 years of age. Although genetic factors play a role in COS etiology, only a few causal variants have been reported to date. This study presents a diagnostic exome sequencing (ES) in 37 Israeli Jewish families with a proband diagnosed with COS. By implementing a trio/duo ES approach and applying a well-established diagnostic pipeline, we detected clinically significant variants in 7 probands (19 %). These single nucleotide variants and indels were mostly inherited. The implicated genes were ANKRD11, GRIA2, CHD2, CLCN3, CLTC, IGF1R and MICU1. In a secondary analysis that compared COS patients to 4721 healthy controls, we observed that patients had a significant enrichment of rare loss of function (LoF) variants in LoF intolerant genes associated with developmental diseases. Taken together, ES could be considered as a valuable tool in the genetic workup for COS patients.

Expansion of the GRIA2 phenotypic representation: a novel de novo loss of function mutation in a case with childhood onset schizophrenia.

Childhood-onset schizophrenia (COS) is a rare form of schizophrenia with an onset before 13 years of age. There is rising evidence that genetic factors play a major role in COS etiology, yet, only a few single gene mutations have been discovered. Here we present a diagnostic whole-exome sequencing (WES) in an Israeli Jewish female with COS and additional neuropsychiatric conditions such as obsessive-compulsive disorder (OCD), anxiety, and aggressive behavior. Variant analysis revealed a de novo novel stop gained variant in GRIA2 gene (NM_000826.4: c.1522 G > T (p.Glu508Ter)). GRIA2 encodes for a subunit of the AMPA sensitive glutamate receptor (GluA2) that functions as ligand-gated ion channel in the central nervous system and plays an important role in excitatory synaptic transmission. GluA2 subunit mutations are known to cause variable neurodevelopmental phenotypes including intellectual disability, autism spectrum disorder, epilepsy, and OCD. Our findings support the potential diagnostic role of WES in COS, identify GRIA2 as possible cause to a broad psychiatric phenotype that includes COS as a major manifestation and expand the previously reported GRIA2 loss of function phenotypes.