Impact on the Risk and Severity of Childhood Onset Schizophrenia of Schizophrenia Risk Genetic Variants at the DRD2 and ZNF804A Loci.

The study explored whether schizophrenia risk alleles of the DRD2 rs2514218 and ZNF804A rs1344706 polymorphisms also influenced the risk and severity of childhood-onset schizophrenia (COS) and differentiated it from autism spectrum disorders (ASD). We compared 75 children with COS to 75 children with ASD, 150 patients with adult-onset schizophrenia and 150 healthy individuals. Frequency of the DRD2 T-allele, assumed to be protective against schizophrenia overall, was higher in COS compared to adult-onset schizophrenia and healthy controls. The risk allele A of ZNF804A was associated with greater severity of negative symptoms in COS. The latter result is consistent with the involvement of ZNF804A in the development of severe forms of schizophrenia. The findings regarding DRD2 suggest that the same genetic variants may play different roles in schizophrenia with childhood and adult onset. This warrants further research, since D2 receptor blockade is a general pharmacodynamic property of antipsychotics.

Ribosomal DNA Abundance in the Patient's Genome as a Feasible Marker in Differential Diagnostics of Autism and Childhood-Onset Schizophrenia.

Introduction: Differential diagnostics of early-onset schizophrenia and autism spectrum disorders (ASD) are a problem of child psychiatry. The prognosis and relevant treatment are to a large degree determined by the correctness of diagnosis. We found earlier that leucocyte DNA of adult schizophrenia patients contained significantly larger copy numbers of ribosomal repeats (rDNA) coding for rRNA, than DNA of mentally healthy controls. Aim: To compare the contents of ribosomal repeats in the leucocyte DNA of children with schizophrenia, children with ASD, and healthy age-matched controls to estimate the possibility of using this genetic trait in the differential diagnostics of the two types of disorders. Patients and methods: Blood samples of patients with infantile autism (A­F84.0 according to ICD-10, N = 75) and with childhood-onset schizophrenia (SZ­F20.8 according to ICD-10, N = 43) were obtained from the Child Psychiatry Department of the Mental Health Research Center. The healthy control blood samples (HC, N = 86) were taken from the Research Centre for Medical Genetics collection. The recruitment of cases was based on the clinical psychopathologic approach. DNA was extracted from blood leukocytes with organic solvents. Nonradioactive quantitative hybridization technique was applied for determining the abundance of ribosomal repeats in the genomes. Statistical processing was performed using StatPlus, Statgraphics and MedCalc. Findings: DNA derived from SZ cases contained 565 ± 163 rDNA copies, which is significantly (p < 10−6) higher than the rDNA content in ASD cases (405 ± 109 copies) and controls (403 ± 86 copies). The HC and A groups did not differ by rDNA copy number (p > 0.4). The genetic trait "rDNA copy number in patient's genome" can potentially be applied as an additional marker in differential diagnostics of childhood-onset schizophrenia and autism spectrum disorders.