Mutation of β-glucosidase 2 causes glycolipid storage disease and impaired male fertility
Yildiz Yildiz, … , Siegfried Matern, David W. Russell
Yildiz Yildiz, … , Siegfried Matern, David W. Russell
Published November 1, 2006
Citation Information: J Clin Invest. 2006;116(11):2985-2994. https://doi.org/10.1172/JCI29224.
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Research Article Reproductive biology

Mutation of β-glucosidase 2 causes glycolipid storage disease and impaired male fertility

Abstract

β-Glucosidase 2 (GBA2) is a resident enzyme of the endoplasmic reticulum thought to play a role in the metabolism of bile acid–glucose conjugates. To gain insight into the biological function of this enzyme and its substrates, we generated mice deficient in GBA2 and found that these animals had normal bile acid metabolism. Knockout males exhibited impaired fertility. Microscopic examination of sperm revealed large round heads (globozoospermia), abnormal acrosomes, and defective mobility. Glycolipids, identified as glucosylceramides by mass spectrometry, accumulated in the testes, brains, and livers of the knockout mice but did not cause obvious neurological symptoms, organomegaly, or a reduction in lifespan. Recombinant GBA2 hydrolyzed glucosylceramide to glucose and ceramide; the same reaction catalyzed by the β-glucosidase acid 1 (GBA1) defective in subjects with the Gaucher’s form of lysosomal storage disease. We conclude that GBA2 is a glucosylceramidase whose loss causes accumulation of glycolipids and an endoplasmic reticulum storage disease.

Authors

Yildiz Yildiz, Heidrun Matern, Bonne Thompson, Jeremy C. Allegood, Rebekkah L. Warren, Denise M.O. Ramirez, Robert E. Hammer, F. Kent Hamra, Siegfried Matern, David W. Russell

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Figure 6

Analysis of glycolipids in Gba2 wild-type and knockout mice.

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Analysis of glycolipids in Gba2 wild-type and knockout mice. ...
(A) Glycolipids were extracted from testes of 6-, 20-, and 24-month-old mice, resolved by 1-dimensional TLC, and visualized by staining with orcinol. The positions of the origin and glucosylceramide standards are indicated at left. A glycolipid that accumulated with age in knockout tissue is marked “X” at right. The positions to which several fucosylated glycolipids migrated to are indicated at left. (B) Structural analysis of glycolipid X shown in A. Glycolipids were extracted from the testes of Gba2–/– mice and resolved by 1-dimensional TLC, and glycolipid X was analyzed by mass spectrometry. An m/z 264 precursor ion scan revealed compounds of molecular masses (700.9 and 728.3) characteristic of monohexosylceramides containing sphingosine (d18:1) and either 16:0 or 18:0 fatty acyl groups. A neutral loss scan for m/z 180 diagnostic for glucose- or galactose-containing monohexosylceramides revealed a major compound of mass 700.9. (C) Expression of mouse and human GBA2 in COS cells and measurement of glucosylceramidase and bile acid glucosidase enzyme activities. Cells were transfected with the indicated plasmid DNA, and lysates were assayed for enzyme activity using fluorescently labeled glucosylceramide or bile acid glucoside substrates. (D) Expression of mouse GBA2 (mGBA2) in human embryonic kidney 293 cells and measurement of glucosylceramidase activity. Cells were transfected and assayed for enzyme activity using [14C]glucosylceramide. The positions of the origin and to which authentic glucosylceramide and ceramide standards migrated to are indicated at left. pCMV-mGBA2, expression plasmid encoding mouse GBA2 enzyme.