Linkage and Association of the Mitochondrial Aspartate/Glutamate Carrier SLC25A12 Gene With Autism
ABSTRACT Autism/autistic disorder (MIM number 209850) is a complex, largely genetic psychiatric disorder. The authors recently mapped a susceptibility locus for autism to chromosome region 2q24-q33 (MIM number 606053). In the present study, genes across the 2q24-q33 interval were analyzed to identify an autism susceptibility gene in this region.
Mutation screening of positional candidate genes was performed in two stages. The first stage involved identifying, in unrelated subjects showing linkage to 2q24-q33, genetic variants in exons and flanking sequence within candidate genes and comparing the frequency of the variants between autistic and unrelated nonautistic subjects. Two single nucleotide polymorphisms (SNPs) that showed evidence for divergent distribution between autistic and nonautistic subjects were identified, both within SLC25A12, a gene encoding the mitochondrial aspartate/glutamate carrier (AGC1). In the second stage, the two SNPs in SLC25A12 were further genotyped in 411 autistic families, and linkage and association tests were carried out in the 197 informative families.
Linkage and association were observed between autistic disorder and the two SNPs, rs2056202 and rs2292813, found in SLC25A12. Using either a single affected subject per family or all affected subjects, evidence for excess transmission was found by the Transmission Disequilibrium Test for rs2056202, rs2292813, and a two-locus G*G haplotype. Similar results were observed using TRANSMIT for the analyses. Evidence for linkage was supported by linkage analysis with the two SNPs, with a maximal multipoint nonparametric linkage score of 1.57 and a maximal multipoint heterogeneity lod score of 2.11. Genotype relative risk could be estimated to be between 2.4 and 4.8 for persons homozygous at these loci.
A strong association of autism with SNPs within the SLC25A12 gene was demonstrated. Further studies are needed to confirm this association and to decipher any potential etiological role of AGC1 in autism.
- SourceAvailable from: Varun Warrier
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- "It contains 18 exons, spread over 110 kilobases (kb) . SLC25A12 is expressed primarily as 2.9- and 3.2-kb mRNA species, predominantly in skeletal muscle, heart, and brain [6,9]. It encodes a calcium-binding carrier protein, the mitochondrial aspartate-glutamate carrier isoform 1, which localizes to the mitochondria and is involved in the exchange of the aspartate for glutamate in the inner mitochondrial membrane regulating the cytosolic redox state. "
ABSTRACT: Autism Spectrum Conditions (ASC) are a group of developmental conditions which affect communication, social interactions and behaviour. Mitochondrial oxidative dysfunction has been suggested as a mechanism of autism based on the results of multiple genetic association and expression studies. SLC25A12 is a gene encoding a calcium-binding carrier protein that localizes to the mitochondria and is involved in the exchange of aspartate for glutamate in the inner membrane of the mitochondria regulating the cytosolic redox state. rs2056202 SNP in this gene has previously been associated with ASC. SNPs rs6716901 and rs3765166 analysed in this study have not been previously explored in association with AS. We genotyped three SNPs (rs2056202, rs3765166, and rs6716901) in SLC25A12 in n = 117 individuals with Asperger syndrome (AS) and n = 426 controls, all of Caucasian ancestry. rs6716901 showed significant association with AS (P = 0.008) after correcting for multiple testing. We did not replicate the previously identified association between rs2056202 and AS in our sample. Similarly, rs3765166 (P = 0.11) showed no significant association with AS. The present study, in combination with previous studies, provides evidence for SLC25A12 as involved in the etiology of AS. Further cellular and molecular studies are required to elucidate the role of this gene in ASC.Molecular Autism 03/2014; 5(1):25. DOI:10.1186/2040-2392-5-25 · 5.41 Impact Factor
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- "The variation in metabolic demands of different brain regions could consequently affect the expression of mitochondrial genes. There are also conflicting reports about the association of SLC25A12 with autism [65-67]. The expression of SLC25A24 was reduced in the MC and THL of autism patients. "
ABSTRACT: Background Mitochondrial dysfunction (MtD) has been observed in approximately five percent of children with autism spectrum disorders (ASD). MtD could impair highly energy-dependent processes such as neurodevelopment, thereby contributing to autism. Most of the previous studies of MtD in autism have been restricted to the biomarkers of energy metabolism, while most of the genetic studies have been based on mutations in the mitochondrial DNA (mtDNA). Despite the mtDNA, most of the proteins essential for mitochondrial replication and function are encoded by the genomic DNA; so far, there have been very few studies of those genes. Therefore, we carried out a detailed study involving gene expression and genetic association studies of genes related to diverse mitochondrial functions. Methods For gene expression analysis, postmortem brain tissues (anterior cingulate gyrus (ACG), motor cortex (MC) and thalamus (THL)) from autism patients (n=8) and controls (n=10) were obtained from the Autism Tissue Program (Princeton, NJ, USA). Quantitative real-time PCR arrays were used to quantify the expression of 84 genes related to diverse functions of mitochondria, including biogenesis, transport, translocation and apoptosis. We used the delta delta Ct (∆∆Ct) method for quantification of gene expression. DNA samples from 841 Caucasian and 188 Japanese families were used in the association study of genes selected from the gene expression analysis. FBAT was used to examine genetic association with autism. Results Several genes showed brain region-specific expression alterations in autism patients compared to controls. Metaxin 2 (MTX2), neurofilament, light polypeptide (NEFL) and solute carrier family 25, member 27 (SLC25A27) showed consistently reduced expression in the ACG, MC and THL of autism patients. NEFL (P = 0.038; Z-score 2.066) and SLC25A27 (P = 0.046; Z-score 1.990) showed genetic association with autism in Caucasian and Japanese samples, respectively. The expression of DNAJC19, DNM1L, LRPPRC, SLC25A12, SLC25A14, SLC25A24 and TOMM20 were reduced in at least two of the brain regions of autism patients. Conclusions Our study, though preliminary, brings to light some new genes associated with MtD in autism. If MtD is detected in early stages, treatment strategies aimed at reducing its impact may be adopted.Molecular Autism 11/2012; 3(1):12. DOI:10.1186/2040-2392-3-12 · 5.41 Impact Factor
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- "Oliveira et al. (4) explained observation of the criteria for respiratory chain disorders in 7% of school-age children with ASD. According to the study by Ramoz et al. (5) autism shows a strong association with single nucleotide polymorphisms within the SLC25A12 gene. Moreover, Weissman et al. (6) has reported that the electron transport chain (ETC) complexes I and III deficiencies affect energy metabolism in patients with autism. "
ABSTRACT: Autism results from developmental factors that affect many or all functional brain systems. Brain is one of tissues which are crucially in need of adenosine triphosphate (ATP). Autism is noticeably affected by mitochondrial dysfunction which impairs energy metabolism. Considering mutations within ATPase 6, ATPase 8 and tRNA(Lys) genes, associated with different neural diseases, and the main role of ATPase 6/8 in energy generation, we decided to investigate mutations on these mtDNA-encoded genes to reveal their roles in autism pathogenesis. In this experimental study, mutation analysis for the mentioned genes were performed in a cohort of 24 unrelated patients with idiopathic autism by employing amplicon sequencing of mtDNA fragments. In this study, 12 patients (50%) showed point mutations that represent a significant correlation between autism and mtDNA variations. Most of the identified substitutions (55.55%) were observed on MT-ATP6, altering some conserved amino acids to other ones which could potentially affect ATPase 6 function. Mutations causing amino acid replacement denote involvement of mtDNA genes, especially ATPase 6 in autism pathogenesis. MtDNA mutations in relation with autism could be remarkable to realize an understandable mechanism of pathogenesis in order to achieve therapeutic solutions.Cell Journal 08/2012; 14(2):98-101. · 1.11 Impact Factor