Dataset Information

Juvenile cataract-associated mutation of solute carrier SLC16A12 impairs trafficking of the protein to the plasma membrane.

ABSTRACT:

Purpose

SLC16A12 encodes an orphan member of the monocarboxylate transporter family, MCT12. A nonsense mutation in SLC16A12 (c.643C>T; p.Q215X) causes juvenile cataract with a dominant inheritance pattern. In the present study, in vitro and in vivo experimental models were used to gain insight into how the SLC16A12 (c.643C>T) mutation leads to cataract formation.

Methods

MCT12 peptide antibodies were generated and used to examine the expression of MCT12 in the lens using immuno-confocal microscopy. To determine whether loss of Slc16a12 resulted in cataract formation, a Slc16a12 hypomorphic rat generated by transposon insertional mutagenesis was characterized using RT-PCR, slit lamp microscopy and histologic methods. Exogenous expression of MCT12 and MCT12:214?, a mimic of the mutant allele, were used to assess protein expression and trafficking.

Results

MCT12 protein was detected in the lens epithelium and secondary fiber cells at postnatal day 1. In the Slc16a12(TKO) rat, complete loss of MCT12 did not result in any detectable ocular phenotype. Exogenous expression of MCT12-GFP and MCT12:214?-GFP revealed that the full-length protein was trafficked to the plasma membrane (PM), whereas the truncated protein was retained in the endoplasmic reticulum (ER). When both MCT12 and MCT12:214? were coexpressed, to mimic the heterozygous patient genotype, the truncated protein was retained in the ER whereas full-length MCT12 was trafficked to the PM. Furthermore, MCT12 was identified as another MCT isoform that requires CD147 for trafficking to the cell surface.

Conclusions

These data support a model whereby the SLC16A12 (c.643C>T) mutation causes juvenile cataract by a defect in protein trafficking rather than by haploinsufficiency.

SUBMITTER: Castorino JJ

PROVIDER: S-EPMC3176021 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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Publications

Juvenile cataract-associated mutation of solute carrier SLC16A12 impairs trafficking of the protein to the plasma membrane.

Castorino John J JJ Gallagher-Colombo Shannon M SM Levin Alex V AV Fitzgerald Paul G PG Polishook Jessica J Kloeckener-Gruissem Barbara B Ostertag Eric E Philp Nancy J NJ

Investigative ophthalmology & visual science 20110829 9

<h4>Purpose</h4>SLC16A12 encodes an orphan member of the monocarboxylate transporter family, MCT12. A nonsense mutation in SLC16A12 (c.643C>T; p.Q215X) causes juvenile cataract with a dominant inheritance pattern. In the present study, in vitro and in vivo experimental models were used to gain insight into how the SLC16A12 (c.643C>T) mutation leads to cataract formation.<h4>Methods</h4>MCT12 peptide antibodies were generated and used to examine the expression of MCT12 in the lens using immuno-co ...[more]

PMID: 21778275

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Project description:PURPOSE: Identification of causal mutation in the crystallin, connexin, and paired box gene 6 (PAX6) genes associated with childhood cataract in patients from India. METHODS: In this study, forty eight members from seventeen families and 148 sporadic cases of childhood cataract were evaluated. Clinical and ophthalmologic examinations were performed on available affected and unaffected family members. Samples of genomic DNA were PCR amplified to screen for mutations in the candidate genes viz., alpha-A crystallin (CRYAA), beta- B2 crystallin (CRYBB2), gamma-A crystallin (CRYGA), gamma-B crystallin (CRYGB), gamma-C crystallin (CRYGC), gamma-D crystallin (CRYGD), gap junction alpha-3 (GJA3), gap junction alpha-8 (GJA8), and PAX6 based on polymerase chain reaction and single strand conformation polymorphism (PCR-SSCP) analysis. Samples showing any band mobility shift were subjected to bidirectional sequencing to confirm the variation. Co-segregation of the observed change with the disease phenotype was further tested by restriction fragment length polymorphism (RFLP) for the appropriate restriction site. RESULTS: DNA sequencing analysis of CRYAA, CRYBB2, CRYGA-D, GJA3, GJA8, and PAX6 of the affected members of a family (C-35) showed a novel heterozygous missense mutation C>A at position 229 in CRYGD in three affected members of family C-35 with anterior polar coronary cataract. This variation C229A substitution created a novel restriction site for AluI and resulted in a substitution of highly conserved arginine at position 77 by serine (R77S). AluI restriction site analysis confirmed the transversion mutation. Analysis of the available unaffected members of the family (C-35) and 100 unrelated control subjects (200 chromosomes) of the same ethnic background did not show R77S variation. Data generated using ProtScale and PyMOL programs revealed that the mutation altered the stability and solvent-accessibility of the CRYGD protein. CONCLUSIONS: We describe here a family having anterior polar coronary cataract that co-segregates with the novel allele R77S of CRYGD in all the affected members. The same was found to be absent in the ethnically matched controls (n=100) studied. Interestingly the residue Arg has been frequently implicated in four missense (R15C, R15S, R37S, and R59H) and in one truncation mutation (R140X) of CRYGD. In two of the reported mutations Arg residues have been replaced with Serine. This finding further expands the mutation spectrum of CRYGD in association with childhood cataract and demonstrates a possible mechanism of cataractogenesis. Screening of other familial (n=48) and sporadic (n=148) cases of childhood cataract, did not reveal any previously reported or novel mutation in the candidate genes screened.

Project description:Solute carrier family 7 member 2 (SLC7A2, also known as CAT2) is an inducible transporter of the semi-essential amino acid L-arginine (L-Arg), which has been implicated in wound repair. We have reported that both SLC7A2 expression and L-Arg availability are decreased in colonic tissues from inflammatory bowel disease patients and that mice lacking Slc7a2 exhibit a more severe disease course when exposed to dextran sulfate sodium (DSS) compared to wild-type (WT) mice. Here, we present evidence that SLC7A2 plays a role in modulating colon tumorigenesis in the azoxymethane (AOM)-DSS model of colitis-associated carcinogenesis (CAC). SLC7A2 was localized predominantly to colonic epithelial cells in WT mice. Utilizing the AOM-DSS model, Slc7a2-/- mice had significantly increased tumor number, burden, and risk of high-grade dysplasia vs. WT mice. Tumors from Slc7a2-/- mice exhibited significantly increased levels of the proinflammatory cytokines/chemokines IL-1β, CXCL1, CXCL5, IL-3, CXCL2, CCL3, and CCL4, but decreased levels of IL-4, CXCL9, and CXCL10 compared to tumors from WT mice. This was accompanied by a shift toward pro-tumorigenic M2 macrophage activation in Slc7a2-deficient mice, as marked by increased colonic CD11b+F4/80+ARG1+ cells with no alteration in CD11b+F4/80+NOS2+ cells by flow cytometry and immunofluorescence microscopy. The shift toward M2 macrophage activation was confirmed in bone marrow-derived macrophages from Slc7a2-/- mice. In bone marrow chimeras between Slc7a2-/- and WT mice, the recipient genotype drove the CAC phenotype, suggesting the importance of epithelial SLC7A2 in abrogating neoplastic risk. These data reveal that SLC7A2 has a significant role in the protection from CAC in the setting of chronic colitis, and suggest that the decreased SLC7A2 in inflammatory bowel disease (IBD) may contribute to CAC risk. Strategies to enhance L-Arg availability by supplementing L-Arg and/or increasing L-Arg uptake could represent a therapeutic approach in IBD to reduce the substantial long-term risk of colorectal carcinoma.

Dataset Information

Juvenile cataract-associated mutation of solute carrier SLC16A12 impairs trafficking of the protein to the plasma membrane.

Purpose

Methods

Results

Conclusions

Publications

Juvenile cataract-associated mutation of solute carrier SLC16A12 impairs trafficking of the protein to the plasma membrane.

Similar Datasets

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