Abnormal Cell Properties and Down-Regulated FAK-Src Complex Signaling in B Lymphoblasts of Autistic Subjects

Abstract

Recent studies suggest that one of the major pathways to the pathogenesis of autism is reduced cell migration. Focal adhesion kinase (FAK) has an important role in neural migration, dendritic morphological characteristics, axonal branching, and synapse formation. The FAK-Src complex, activated by upstream reelin and integrin ␤1, can initiate a cascade of phosphorylation events to trigger multiple intracellular pathways, including mitogen-activated protein kinaseextracellular signal-regulated kinase and phosphatidylinositol 3-kinase-Akt signaling. In this study, by using B lymphoblasts as a model, we tested whether integrin ␤1 and FAK-Src signaling are abnormally regulated in autism and whether abnormal FAK-Src signaling leads to defects in B-lymphoblast adhesion, migration, proliferation, and IgG production. To our knowledge, for the first time, we show that protein expression levels of both integrin ␤1 and FAK are significantly decreased in autistic lymphoblasts and that Src protein expression and the phosphorylation of an active site (Y416) are also significantly decreased. We also found that lymphoblasts from autistic subjects exhibit significantly decreased migration, increased adhesion properties, and an impaired capacity for IgG production. The overexpression of FAK in autistic lymphoblasts countered the adhesion and migration defects. In addition, we demonstrate that FAK mediates its effect through the activation of Src, phosphatidylinositol 3-kinase-Akt, and mitogen-activated protein kinase signaling cascades and that paxillin is also likely involved in the regulation of adhesion and migration in autistic lymphoblasts. Autism is a severe neurodevelopmental disorder characterized by problems in communication, social skills, and repetitive behavior. Susceptibility to autism is clearly attributable to the interplay of genetic and environmental factors, 1-10 but the etiology of this disorder is unknown and no biomarkers have yet been proved characteristic of autism. Recent research 11 is beginning to depict three major pathways as being potentially involved in the pathogenesis of autism (ie, reduced cell migration, excitatory-inhibitory imbalance, and abnormal synaptogenesis). The reelin protein encoded by the RELN gene plays a pivotal role in neuronal cell migration and the prenatal development of neural connections.12 Reelin has coexpressed with HAR1F, which is a novel RNA gene expressed specifically in Cajal-Retzius neurons in the developing human neocortex from gestational week 7 to 19 (a crucial period for cortical neuron specification and migration). 13 Linkage between RELN and autism is a replicated genetic finding in autism research, and reelin has been reduced in the serum and brain specimens of autistic subjects.14,15 Reelin can act through ␣3␤1 integrins and exert proteolytic activity on extracellular matrix (ECM) proteins, which are crucial for neuronal migration. 16 Most recently, emerging evidence 17 indicates that synaptic cell adhesion pathways are disrupted in some

iTRAQ‐Based Proteomic Analysis Reveals Protein Profile in Plasma from Children with Autism

“…These processes have been reported to be associated with ASD in the previous studies and our results were similar to these studies. For example, expression of FAK (focal adhesion kinase) was diminished in autistic lymphoblasts and overexpression of FAK in these cells restored the adhesion and migration defects . Besides ASDs, change in cytoskeleton proteins expression has been reported in other psychiatric disorders .…”

“…In addition, recent genetic studies demonstrate that alterations in synaptic genes including those encoding cell adhesion molecules and their interaction partners play important roles in the pathogenesis of ASD . Migration defects have also been proposed as one of the major pathways of autism …”

The apoptotic perspective of autism

“…Recently, Sheikh et al (2010a,b) also found that the Bcl‐2 expression was significantly reduced in the frontal cerebral cortex and cerebellum of autistic subjects. Lymphoblast cell lines have been suggested to be a valuable tool for identifying genes associated with autism and provide an alternative approach for understanding the biology and genetics of autism (Baron et al, 2006; Wei et al, 2011). By examining Bcl‐2 protein expression in the lymphoblasts of autistic subjects and compare the results with age‐matched normal controls, Malik et al identified that Bcl‐2 protein expression is also significantly decreased in lymphoblasts of autistic subjects (Malik et al, 2011).…”

The diverse roles and multiple forms of focal adhesion kinase in brain

“…Indeed, FAK expression is diminished in autistic lymphoblasts, and these cells show defects in migration, adhesion and proliferation (Wei et al ., ). Of note, overexpression of FAK in these cells restored the adhesion and migration defects (Wei et al ., ). Further studies link an influence of dysregulated FAK on the appearance of autism and schizophrenia.…”

“…Migration defects have been proposed as one of the major pathways of autism. Indeed, FAK expression is diminished in autistic lymphoblasts, and these cells show defects in migration, adhesion and proliferation (Wei et al, 2011). Of note, overexpression of FAK in these cells restored the adhesion and migration defects (Wei et al, 2011).…”