Molecular characterization of Tunisian families with abetalipoproteinemia and identification of a novel mutation in MTTP gene

BACKGROUND: Abetalipoproteinemia (ABL; OMIM 200100) is a rare monogenic disorder of lipid metabolism characterized by reduced plasma levels of total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C) and almost complete absence of apolipoprotein B (apoB). ABL results from genetic deficiency in microsomal triglyceride transfer protein (MTP; OMIM 157147). In the present study we investigated two unrelated Tunisian patients, born from consanguineous marriages, with severe deficiency of plasma low-density lipoprotein (LDL) and apo B. METHODS: Intestinal biopsies were performed and The MTTP gene was amplified by Polymerase chain reaction then directly sequenced in patients presenting chronic diarrhea and retarded growth. RESULTS: First proband was homozygous for a novel nucleotide deletion (c. 2611delC) involving the exon 18 of MTTP gene predicted to cause a non functional protein of 898 amino acids (p.H871I fsX29). Second proband was homozygous for a nonsense mutation in exon 8 (c.923 G > A) predicted to cause a truncated protein of 307 amino acids (p.W308X), previously reported in ABL patients. CONCLUSIONS: We discovered a novel mutation in MTTP gene and we confirmed the diagnosis of abetalipoproteinemia in new Tunisian families. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8134027928652779.