Autism spectrum disorders (ASD) present with a high genetic heterogeneity, and so far no single gene could be directly associated to ASD etiology. Genome wide association studies remained unsuccessful so far. Screening of candidate genes showed that 6-10% of ASD patients carry mutations in genes linked to neurogenesis and synaptic plasticity. However, the pathomechanisms underlying ASD remain unclear. Recently discovered mutations in the ribosomal protein L10 gene (RPL10) provided a new hint towards an altered translational capacity.
Objectives:
To further understand the contribution of an RPL10 mutation at protein level we used 2-dimensional differential-in-gel-electrophoresis (2D-DIGE) on lymphoblastoid cell lines (LCLs). Putative candidates were analyzed using tandem mass-spectrometry.
Methods:
We compared cell lines carrying the RPL10 mutations with non-mutant allele carriers and a set of 10 ASD patients, not harbouring any RPL10 mutation, with 10 random controls. Validation of differentially regulated proteins was performed on mRNA and overall protein expression level applying RT-PCR and Western Blot methods.
Results:
Candidates differentially expressed due to a mutation in the RPL10 gene were associated to the same functional pathways deregulated in cell lines derived from ASD patients. These proteins were mainly related to oxidative phosphorylation and energy metabolism as well as control of mRNA and protein stability. Validation of these results showed that the alteration is mainly taking place at translational levels and suggested also alterations of yet uncharacterized post-translational modifications. Furthermore we observed a variant protein expression level in the ASD samples which in some candidates correlated with a variant mRNA expression level. Overall, the differential protein patterns identified in the LCLs from autistic patients in comparison to LCLs from controls may result from both quantitative (expression level) and qualitative (post-translational modifications) changes in translation.
Conclusions:
The RPL10 mutations contribute to the molecular phenotype observed in the ASD derived cell lines by altering functionally related mechanisms. The identified candidates seem to be altered not only quantitatively, but also by a change in post-translational modifications. A further characterization of these modifications is needed. The association of the identified pathomechanisms to ASD is in agreement with already known candidate pathways. Therefore, we provide evidence that lymphoblastoid cell lines could serve as a tool to characterize the impact of a single mutation in a complex disorder.