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Hypomorphic variants of cationic amino acid transporter 3 in males with autism spectrum disorders.

Nava C, Rupp J, Boissel JP, Mignot C, Rastetter A, Amiet C, Jacquette A, Dupuits C, Bouteiller D, Keren B, Ruberg M, Faudet A, Doummar D, Philippe A, Périsse D, Laurent C, Lebrun N, Guillemot V, Chelly J, Cohen D, Héron D, Brice A, Closs EI, Depienne C - Amino Acids (2015)

Bottom Line: We then sequenced the SLC7A3 coding sequence in 148 male patients with ASD and identified three additional rare missense variants in unrelated patients.Functional analyses of the mutant transporters showed that two of the four identified variants cause severe or moderate loss of CAT-3 function due to altered protein stability or abnormal trafficking to the plasma membrane.This study shows that rare hypomorphic variants of SLC7A3 exist in male individuals and suggest that SLC7A3 variants possibly contribute to the etiology of ASD in male subjects in association with other genetic factors.

View Article: PubMed Central - PubMed

Affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR S 1127, ICM, 75013, Paris, France.

ABSTRACT
Cationic amino acid transporters (CATs) mediate the entry of L-type cationic amino acids (arginine, ornithine and lysine) into the cells including neurons. CAT-3, encoded by the SLC7A3 gene on chromosome X, is one of the three CATs present in the human genome, with selective expression in brain. SLC7A3 is highly intolerant to variation in humans, as attested by the low frequency of deleterious variants in available databases, but the impact on variants in this gene in humans remains undefined. In this study, we identified a missense variant in SLC7A3, encoding the CAT-3 cationic amino acid transporter, on chromosome X by exome sequencing in two brothers with autism spectrum disorder (ASD). We then sequenced the SLC7A3 coding sequence in 148 male patients with ASD and identified three additional rare missense variants in unrelated patients. Functional analyses of the mutant transporters showed that two of the four identified variants cause severe or moderate loss of CAT-3 function due to altered protein stability or abnormal trafficking to the plasma membrane. The patient with the most deleterious SLC7A3 variant had high-functioning autism and epilepsy, and also carries a de novo 16p11.2 duplication possibly contributing to his phenotype. This study shows that rare hypomorphic variants of SLC7A3 exist in male individuals and suggest that SLC7A3 variants possibly contribute to the etiology of ASD in male subjects in association with other genetic factors.

No MeSH data available.


Related in: MedlinePlus

Analysis of WT and mutant CAT-3 transport activity, expression and localization in Xenopus laevis oocytes. a Transport of 100 µM [3H]L-arginine for 15 min into oocytes. b Representative Western Blot of WT and mutant CAT-3-EGFP proteins in whole cell lysates and at the plasma membrane. c Quantification of three independent experiments as shown in b, leftcolumns CAT-3 in total cell lysate, right columns in plasma membrane protein fraction
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Fig3: Analysis of WT and mutant CAT-3 transport activity, expression and localization in Xenopus laevis oocytes. a Transport of 100 µM [3H]L-arginine for 15 min into oocytes. b Representative Western Blot of WT and mutant CAT-3-EGFP proteins in whole cell lysates and at the plasma membrane. c Quantification of three independent experiments as shown in b, leftcolumns CAT-3 in total cell lysate, right columns in plasma membrane protein fraction

Mentions: Further studies in Xenopus laevis oocytes showed that transport activities were reduced in oocytes expressing p.Tyr430Cys and p.Ser589Thr compared to oocytes expressing WT CAT-3 (Fig. 3a). Overall, expression of p.Tyr430Cys and p.Ser589Thr proteins was also reduced. The reduction was more pronounced in the plasma membrane fraction, especially for p.Tyr430Cys (Fig. 3b, c). Altogether, these findings confirmed that two of the four SLC7A3 variants identified had deleterious effects on CAT-3 protein function.Fig. 3


Hypomorphic variants of cationic amino acid transporter 3 in males with autism spectrum disorders.

Nava C, Rupp J, Boissel JP, Mignot C, Rastetter A, Amiet C, Jacquette A, Dupuits C, Bouteiller D, Keren B, Ruberg M, Faudet A, Doummar D, Philippe A, Périsse D, Laurent C, Lebrun N, Guillemot V, Chelly J, Cohen D, Héron D, Brice A, Closs EI, Depienne C - Amino Acids (2015)

Analysis of WT and mutant CAT-3 transport activity, expression and localization in Xenopus laevis oocytes. a Transport of 100 µM [3H]L-arginine for 15 min into oocytes. b Representative Western Blot of WT and mutant CAT-3-EGFP proteins in whole cell lysates and at the plasma membrane. c Quantification of three independent experiments as shown in b, leftcolumns CAT-3 in total cell lysate, right columns in plasma membrane protein fraction
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4633447&req=5

Fig3: Analysis of WT and mutant CAT-3 transport activity, expression and localization in Xenopus laevis oocytes. a Transport of 100 µM [3H]L-arginine for 15 min into oocytes. b Representative Western Blot of WT and mutant CAT-3-EGFP proteins in whole cell lysates and at the plasma membrane. c Quantification of three independent experiments as shown in b, leftcolumns CAT-3 in total cell lysate, right columns in plasma membrane protein fraction
Mentions: Further studies in Xenopus laevis oocytes showed that transport activities were reduced in oocytes expressing p.Tyr430Cys and p.Ser589Thr compared to oocytes expressing WT CAT-3 (Fig. 3a). Overall, expression of p.Tyr430Cys and p.Ser589Thr proteins was also reduced. The reduction was more pronounced in the plasma membrane fraction, especially for p.Tyr430Cys (Fig. 3b, c). Altogether, these findings confirmed that two of the four SLC7A3 variants identified had deleterious effects on CAT-3 protein function.Fig. 3

Bottom Line: We then sequenced the SLC7A3 coding sequence in 148 male patients with ASD and identified three additional rare missense variants in unrelated patients.Functional analyses of the mutant transporters showed that two of the four identified variants cause severe or moderate loss of CAT-3 function due to altered protein stability or abnormal trafficking to the plasma membrane.This study shows that rare hypomorphic variants of SLC7A3 exist in male individuals and suggest that SLC7A3 variants possibly contribute to the etiology of ASD in male subjects in association with other genetic factors.

View Article: PubMed Central - PubMed

Affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR S 1127, ICM, 75013, Paris, France.

ABSTRACT
Cationic amino acid transporters (CATs) mediate the entry of L-type cationic amino acids (arginine, ornithine and lysine) into the cells including neurons. CAT-3, encoded by the SLC7A3 gene on chromosome X, is one of the three CATs present in the human genome, with selective expression in brain. SLC7A3 is highly intolerant to variation in humans, as attested by the low frequency of deleterious variants in available databases, but the impact on variants in this gene in humans remains undefined. In this study, we identified a missense variant in SLC7A3, encoding the CAT-3 cationic amino acid transporter, on chromosome X by exome sequencing in two brothers with autism spectrum disorder (ASD). We then sequenced the SLC7A3 coding sequence in 148 male patients with ASD and identified three additional rare missense variants in unrelated patients. Functional analyses of the mutant transporters showed that two of the four identified variants cause severe or moderate loss of CAT-3 function due to altered protein stability or abnormal trafficking to the plasma membrane. The patient with the most deleterious SLC7A3 variant had high-functioning autism and epilepsy, and also carries a de novo 16p11.2 duplication possibly contributing to his phenotype. This study shows that rare hypomorphic variants of SLC7A3 exist in male individuals and suggest that SLC7A3 variants possibly contribute to the etiology of ASD in male subjects in association with other genetic factors.

No MeSH data available.


Related in: MedlinePlus