Hepatic Expression of the Na+-Taurocholate Cotransporting Polypeptide Is Independent from Genetic Variation.

The hepatic Na+-taurocholate cotransporting polypeptide NTCP/SLC10A1 is important for the uptake of bile salts and selected drugs. Its inhibition results in increased systemic bile salt concentrations. NTCP is also the entry receptor for the hepatitis B/D virus. We investigated interindividual hepatic SLC10A1/NTCP expression using various omics technologies. SLC10A1/NTCP mRNA expression/protein abundance was quantified in well-characterized 143 human livers by real-time PCR and LC-MS/MS-based targeted proteomics. Genome-wide SNP arrays and SLC10A1 next-generation sequencing were used for genomic analyses. SLC10A1 DNA methylation was assessed through MALDI-TOF MS. Transcriptomics and untargeted metabolomics (UHPLC-Q-TOF-MS) were correlated to identify NTCP-related metabolic pathways. SLC10A1 mRNA and NTCP protein levels varied 44-fold and 10.4-fold, respectively. Non-genetic factors (e.g., smoking, alcohol consumption) influenced significantly NTCP expression. Genetic variants in SLC10A1 or other genes do not explain expression variability which was validated in livers (n = 50) from The Cancer Genome Atlas. The identified two missense SLC10A1 variants did not impair transport function in transfectants. Specific CpG sites in SLC10A1 as well as single metabolic alterations and pathways (e.g., peroxisomal and bile acid synthesis) were significantly associated with expression. Inter-individual variability of NTCP expression is multifactorial with the contribution of clinical factors, DNA methylation, transcriptional regulation as well as hepatic metabolism, but not genetic variation.

Sequence variants in ESR1 and OXTR are associated with Mayer-Rokitansky-Küster-Hauser syndrome.

INTRODUCTION: Mayer-Rokitansky-Küster-Hauser syndrome (MRKHS) is characterized by congenital absence of the uterus and the upper two-thirds of the vagina in otherwise phenotypically normal females. It is found isolated or associated with renal, skeletal and other malformations. Despite ongoing research, the etiology is mainly unknown. For a long time, the hypothesis of deficient hormone receptors as the cause for MRKHS has existed, supported by previous findings of our group. The aim of the present study was to identify unknown genetic causes for MRKHS and to compare them with data banks including a review of the literature. MATERIAL AND METHODS: DNA sequence analysis of the oxytocin receptor (OXTR) and estrogen receptor-1 gene (ESR1) was performed in a group of 93 clinically well-defined patients with uterovaginal aplasia (68 with the isolated form and 25 with associated malformations). RESULTS: In total, we detected three OXTR variants in 18 MRKHS patients with one leading to a missense mutation, and six ESR1 variants in 21 MRKHS patients, two of these causing amino acid changes and therefore potentially disease. CONCLUSIONS: The identified variants on DNA level might impair receptor function through different molecular mechanisms. Mutations of ESR1 and OXTR are associated with MRKHS. Thus, we consider these genes potential candidates associated with the manifestation of MRKHS.