A Severe Form of Abetalipoproteinemia Caused by New Splicing Mutations of Microsomal Triglyceride Transfer Protein

Abstract

The original article to which this Erratum refers was published in Human Mutation 32: 751–759 (2011). In this published article from Volume 32, Issue 7, Figures 1-5 do not appear clearly. Included in this erratum are high-resolution images for these figures. Diagnosis of abetalipoproteinemia. A: Upper gastrointestinal endoscopy performed in patient AM revealed a white aspect of duodenal villi, characteristic of lipid storage. B: Biopsy was performed in duodenum and processed for hematoxylin/eosin-staining. The arrow points at the presence of lipid droplets within the enterocytes. C, D: Serum from control or patient (AM) was analyzed using FPLC system. Lipoproteins were separated and total cholesterol (C) and triglycerides (D) were measured. Profiles are shown for control (Ctrl) and patient (AM). Proteins were only showed for patient in C. Note the difference of y-axis (lipid content) between control and patient. Sequence analysis of mutant MTTP transcription products. A, C: After mRNA extraction and reverse transcription from control and patient (AM) EBV-immortalized lymphocytes, PCR was performed to amplify exon 6 (A) and exon 10 (C) with 5′ and 3′ flanking regions. PCR products were analyzed by migration on agarose gel. Arrowhead points at the lower band found in patient compared to the control. B, D: Upper bands in the control and lower bands in patients were purified and then cloned into pCR2.1 vector before sequencing. In B, electrophoregrams showed the exon 6 and 5′ and 3′ flanking regions with exon 5 and 7 in the control. In the patient, the exon 6 is deleted, leading to a frameshift and a premature stop codon. In D, similarly, electrophoregrams showed the exon 10 and 5′ and 3′ flanking regions with exon 9 and 11 in the control. In the patient, the exon 10 is deleted. E: The amino acid sequences corresponding to exons 6 and 10 are shown underlined and in blue in the normal MTTP sequence. // determined the deletion of exons 6 or 10 in each mutant. For Δ6-MTTP, the frame-shift mutation results in an abnormal sequence described in red and in italic. MTTP expression and activity in duodenal biopsy. A: Duodenal biopsy from control (Ctrl) or patient (AM) and Caco-2 cell lysate were analyzed by SDS gel electrophoresis and Western blotting with antibodies against MTTP. B: The triglyceride transfer activity of MTTP was measured on duodenal biopsy from control or patient (AM). Values are expressed as the mean of three independent experiments; standard errors are indicated. Interaction of WT and mutant MTTP with PDI. A, B: HeLa cells were transfected or not with WT-MTTP, Δ6-MTTP or Δ10-MTTP tagged with EGFP (A) or 2xMyc (B). Cell lysates (100 µg) were analyzed by SDS gel electrophoresis and Western blotting with antibodies against GFP (A), Myc (B) and Rab5 as loading control. Arrowheads point at WT-MTTP, Δ6-MTTP or Δ10-MTTP and arrows point at nonspecific band (ns). Blots in B were scanned and the quantification is shown in C. Each experiment was repeated at least three times, and (C) shows a representative example. D, E: HeLa cells were transfected with 2xMyc-tagged WT-MTTP, Δ6-MTTP or Δ10-MTTP. Cell lysates (Lys) were subjected to immunoprecipitation with (+) or without (−) the anti-myc antibody (D) or the anti-PDI antibody (E). Analysis was performed by SDS gel electrophoresis and Western blotting with antibodies against Myc or PDI. Arrowheads point at immunoprecipitated WT-MTTP, Δ6-MTTP or Δ10-MTTP (D) or PDI (E) and arrows point at nonspecific band (ns). IgG HC represents heavy chain of anti-PDI antibody used for immunoprecipitation. Localization of WT and mutant MTTP and ER marker. A: HeLa cells were cotransfected with GFP-tagged WT-MTTP, Δ6-MTTP or Δ10-MTTP and a vector encoding DsRed-ER marker. Cells were then processed for fluorescence analysis. B: HeLa cells were transfected with GFP-tagged WT-MTTP, Δ6-MTTP or Δ10-MTTP and were then processed for immunofluorescence using anti-PDI antibody. Bar: 10 µm. The publisher regrets these errors.