Mutation in Parkinson disease-associated, G-protein-coupled receptor 37 (GPR37/PaelR) is related to autism spectrum disorder

Abstract

Little is known about the molecular pathogenesis of Autism spectrum disorder (ASD), a neurodevelopmental disorder. Here we identified two mutations in the G-protein-coupled receptor 37 gene (GPR37) localized on chromosome 7q31-33, called the AUTS1 region, of ASD patients; 1585-1587 ttc del (Del312F) in one Japanese patient and G2324A (R558Q) in one Caucasian patient. The Del312F was located in the conserved transmembrane domain, and the R558Q was located in a conserved region just distal to the last transmembrane domain. In addition, a potential ASD-related GPR37 variant, T589M, was found in 7 affected Caucasian men from five different families. Our results suggested that some alleles in GPR37 were related to the deleterious effect of ASD. GPR37 is associated with the dopamine transporter to modulate dopamine uptake, and regulates behavioral responses to dopaminergic drugs. Thus, dopaminergic neurons may be involved in the ASD. However, we also detected the Del321F mutation in the patient's unaffected father and R558Q in not only an affected brother but also an unaffected mother. The identification of unaffected parents that carried the mutated alleles suggested that the manifestation of ASD was also influenced by factors other than these mutations, including endoplasmic reticulum stress of the mutated proteins or gender. Our study will provide the new insight into the molecular pathogenesis of ASD.

Figure 1. Sequences of mutations detected and family trees of the patients with each base substitution.

(A) Japanese family of MRX214 with Del 312F in GPR37. (B) Caucasian family of AU0654 with mutation R558Q in GPR37. (C) Caucasian family with T589M in GPR37. Closed boxes and circles indicate the individual with ASD, + indicate the individual with mutations.

Figure 2. The location of the GPR37 mutations.

Arrow indicates the position of Del312F, R558Q and M589T.TM, transmembrane domain.

Figure 3. The localization of wild-type and mutated GPR37 in C2C5 cells.

(A) Co-localization of wild-type GPR37-myc with endoplasmic reticulum (ER)-marker (Bip/GRP78). Scale bar: 10 µm. (B) C2C5 cells were transfected with wild-type GPR37-myc, GPR37(R558Q) -myc or GPR37(Del312F)-myc for 28 h after transfection. Cells were fixed, and immunostained with anti-myc (GPR37, red) and Hoechst (blue). Scale bar: 20 µm.

Figure 4. Appearance of apoptotic cells and cell having intracellular accumulation of GPR37(R558Q) and GPR37(Del312F) in time-dependent manner.

(A) Apoptotic cells expressing wild-type GPR37-myc, GPR37(R558Q)-myc or GPR37(Del312F)-myc. Green, GPR37 wild-type or mutants. Blue, Hoechst. Right pictures, high magnification of left pictures. Arrowheads, apoptotic morphology. Scale bars: 40 µm. (B) The percentage of the apoptotic cells in the cells expressing, GPR37(R558Q)-myc or GPR37(Del312F)-myc. Values are mean ± standard error (SEM). All experiments were performed three times. A significant difference of the percentage of cells exhibiting apoptotic morphology was detected in the cells expressing wild-type GPR 37 and mutated GPR37. (Student's t-test; p<0.05). Control, cells expressing vacant vector (GFPC1-vector).