Ultrarare Variants in DNA Damage Repair and Mitochondrial Genes in Pediatric Acute-Onset Neuropsychiatric Syndrome and Acute Behavioral Regression in Neurodevelopmental Disorders.

We recently identified variants in 10 genes that are members of either the p53 pathway or Fanconi Anemia Complex (FAC), regulators of DNA repair (DNA damage response [DDR]) in 17 cases with pediatric acute-onset neuropsychiatric syndrome (PANS) or regression in autism spectrum disorder and other neurodevelopmental disorders (NDD). We aimed to identify additional cases with genetic vulnerabilities in DDR and related pathways. Whole-exome sequencing (WES) and whole-genome sequencing (WGS) data from 32 individuals were filtered and analyzed to identify ultrarare pathogenic or likely pathogenic variants. Variants affecting DDR were found in 14 cases diagnosed with PANS or regression (CUX1, USP45, PARP14, UVSSA, EP300, TREX1, SAMHD1, STK19, MYTl1, TEP1, PIDD1, ADNP, FANCD2, and RAD54L). The CUX1 variant is de novo, as are two cases that had mutations in genes that affect mitochondrial functions that are connected directly or indirectly to mitophagy (PRKN and POLG), which can trigger the same innate immune pathways when disrupted as abnormal DDR. We also found pathogenic or likely pathogenic secondary mutations in several genes that are primarily expressed in the gut that have been implicated in gut microbiome homeostasis (e.g., LGALS4, DUOX2, CCR9). These findings align with previous genetic findings and strengthen the hypothesis that abnormal DDR and mitochondrial dysfunction underlie pathogenic processes in at least some cases of neuropsychiatric decompensation. The potential involvement of genetic variants in gut microbiome homeostasis is a novel aspect of our study. Functional characterization of the downstream impact of DDR deficits may point to novel treatment strategies.