Association between the g.296596G > A genetic variant of RELN gene and susceptibility to autism in a Chinese Han population

The Pathophysiological Link Between Reelin and Autism: Overview and New Insights

Reelin is a secreted extracellular matrix protein playing pivotal roles in neuronal migration and cortical stratification during embryonal brain development. In the adult brain, its activity is crucial for synaptic plasticity, memory processing, and cognition. Genetic alterations in RELN have been variably reported as possible contributors to the pathogenesis of autism spectrum disorders (ASD). In particular, GCCs repeats in the 5′UTR, and single nucleotide polymorphysms (SNPs) in RELN have been suggested to affect brain development and predispose to autism. We reviewed pertinent literature on RELN expression and haplotypes transmission in children with ASD, critically analyzing available evidence in support of the pathophysiological association between Reelin deficiency and ASD.

Two single-nucleotide polymorphisms of the RELN gene and symptom-based and developmental deficits among children and adolescents with autistic spectrum disorders in the Tianjin, China

Increasing evidence has revealed that genetic variants in Reelin (RELN) gene, especially single-nucleotide polymorphisms (SNPs), correlate with autistic spectrum disorders (ASD) risk; however, no consensus have been reached. This study aimed to provide additional evidence for the association between two SNPs of RELN (i.e., rs736707, rs2229864) and ASD risk, as well as the relationship between RELN gene and symptom-based and developmental deficits of ASD patients in Chinese Han children and adolescents. 157 ASD subjects and 256 typical development (TD) controls were genotyped by TaqMan® genotyping assay. ASD patients were assessed by Childhood Autism Rating Scale (CARS), Autism Behavior Checklist (ABC), and Early Childhood Development Questionnaire (ECDQ). We found that SNP rs2229864 was associated with the genetic predisposition of ASD, whereas a negative association between SNP rs2229864 and symptom-based and developmental features was detected. In contrast, RELN rs736707 correlated with the sensory subscale of the ABC, the relating subscale of the ABC and the total score of ABC, although we did not detect a significant association between SNP rs736707 and ASD risk. Furthermore, a significant rs736707-rs2229864 haplotype was detected. Individuals with a CC haplotype were more likely to have ASD, but individuals with a CT haplotype had more chance be TD controls. Further studies using more samples and including more gene variants in RELN are warranted to confirm our results.

Mapping pathological phenotypes in reelin mutant mice

Autism Spectrum Disorders (ASD) are neurodevelopmental disorders with multifactorial origin characterized by social communication deficits and the presence of repetitive behaviors/interests. Several studies showed an association between the reelin gene mutation and increased risk of ASD and a reduced reelin expression in some brain regions of ASD subjects, suggesting a role for reelin deficiency in ASD etiology. Reelin is a large extracellular matrix glycoprotein playing important roles during development of the central nervous system. To deeply investigate the role of reelin dysfunction as vulnerability factor in ASD, we assessed the behavioral, neurochemical, and brain morphological features of reeler male mice. We recently reported a genotype-dependent deviation in the ultrasonic vocal repertoire and a general delay in motor development of reeler pups. We now report that adult male heterozygous (Het) reeler mice did not show social behavior and communication deficits during male-female social interactions. Wildtype and Het mice showed a typical light/dark locomotor activity profile, with a peak during the central interval of the dark phase. However, when faced with a mild stressful stimulus (a saline injection) only Het mice showed an over response to stress. In addition to the behavioral studies, we conducted high performance liquid chromatography and magnetic resonance imaging and spectroscopy to investigate whether reelin mutation influences brain monoamine and metabolites levels in regions involved in ASD. Low levels of dopamine in cortex and high levels of glutamate and taurine in hippocampus were detected in Het mice, in line with clinical data collected on ASD children. Altogether, our data detected subtle but relevant neurochemical abnormalities in reeler mice supporting this mutant line, particularly male subjects, as a valid experimental model to estimate the contribution played by reelin deficiency in the global ASD neurobehavioral phenotype.