APOB and abetalipoproteinemia: From the study of familial hypobetalipoproteinemia (OMIM +107730) and abetalipoproteinemia (OMIM 200100), it is evident that both apolipoprotein (apo)B and the microsomal triglyceride transfer protein (MTTP)4 are obligatory for the production of chylomicrons and very low density lipoproteins (VLDL) within the endoplasmic reticulum (ER) of enterocytes and hepatocytes, respectively (1, 13, –, 15).