Deletion of CH25H and LIPA Genes in Human Abolishes Biosynthesis of 25-Hydroxycholesterol but not of 7α,25-Dihydroxysterols and Enhances Non-enzymatic Cholesterol Oxidation: Metabolic Changes are Partially Reversed by Hematopoietic Stem Cell Transplant ^‡

The CH25H ( cholesterol 25-hyroxylase ) and LIPA ( lipase A, lysosomal acid type ) genes are contiguous genes on chromosome 10. CH25H is translated to cholesterol 25-hydroxylase which generates 25- hydroxycholesterol (25-HC) from cholesterol, while LIPA codes for lysosomal acid lipase (LAL) which hydrolyses cholesteryl esters in the endosome – lysosome compartment. Here we report the effect on the oxysterol pattern in plasma of the homozygous deletion of these two genes and their restoration by allogeneic hematopoietic stem cell transplant (HSCT). In the absence of CH25H , 25-HC is not detected in plasma, but surprisingly, 7α,25-dihydroxysterols are present, indicating their formation by a second sterol 25-hydroxylase. As with the isolated deletion of LIPA seen in Wolman disease, patients with the homozygous contiguous deletion show high levels of cholesterol autoxidation products in plasma. HSCT of patients with the contiguous deletion restores both 25-HC and autoxidation products to normal levels following an initial burst in autoxidation soon after transplant.