Mutations in the TSGA14 gene in families with autism spectrum disorders

Abstract

Linkage to 7q has been the most robust genetic finding in familial autism. A previous scan of multiplex families with autism spectrum disorders found a linkage signal of genome-wide significance at D7S530 on 7q32. We searched a candidate imprinted region at this location for genetic variants in families with positive linkage scores. Using exon resequencing, we identified three rare potentially pathogenic variants in the TSGA14 gene, which encodes a centrosomal protein. Two variants were missense mutations (c.664C>G; p.P206A and c.766T>G; p.C240G) that changed conserved residues in the same protein domain; the third variant (c.192+5G>A) altered splicing, which resulted in a protein with an internal deletion of 16 residues and a G33D substitution. These rare TSGA14 variants are enriched in the affected subjects (6/348 patients versus 2/670 controls, Fisher's exact two tailed P = 0.022). This is the first report of a possible link of a gene with a centrosomal function with familial autism.

Fig. 1

LD structure and genes in the 220 kb region at 7q32. LD blocks are indicated by black boxes. Triangles mark recombination hotspots. Long ticks mark approximate locations of 14 SNP from Table I on the physical map (not in scale). SNPs selected for genotyping of the entire set of ASD families are marked by stars. Grey shaded boxes denote protein-coding genes. miR-335 is marked by a short tick. Gene orientation is shown by arrowheads.

Fig. 2

Transmission of TSGA14 variants in families with ASD. (A–D) Families with positive linkage scores, (E) zero linkage scores, (F–G) unknown linkage status. In (B) family, mother is Caucasian and father has more than 2 races, in all other families both parents are Caucasians. Circles indicates females, squares indicates males. White filling indicates unaffected, black filling indicates a diagnosis of autism, gray filling indicates a diagnosis of pervasive developmental disorder, and hatched filling indicates a learning disability. Corresponding TSGA14 variants are shown in parentheses.

Fig. 3

Abnormal TSGA14 splicing detected by ex vivo splicing assay. (A) Minigene construct. Scheme of the human TSGA14 genomic locus with the S isoform (SwissProt ID Q9BYV8-4), the L isoform (SwissProt IDr Q9BYV8-1), and a part of the TSGA14 gene cloned into expression vector pRcRSV. (B) RT-PCR products of spliced TSGA14 transcripts. Neg - untransfected cells, Wt - cells transfected with a minigene construct carrying wild-type allele (c.192+5G), Mut - cells transfected with a minigene construct carrying c.192+5A mutation, brain - RT-PCR product from control human brain mRNA, NTC - no template control PCR. (C) Exon 3 skipping, which results in G33D change and the deletion of 16 amino acids.