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Targeted deletion of the PEX2 peroxisome assembly gene in mice provides a model for Zellweger syndrome, a human neuronal migration disorder.

Faust PL, Hatten ME - J. Cell Biol. (1997)

Bottom Line: The mutant animals do not feed and are hypoactive and markedly hypotonic.They display abnormal peroxisomal biochemical parameters, including accumulations of very long chain fatty acids in plasma and deficient erythrocyte plasmalogens.Abnormal lipid storage is evident in the adrenal cortex, with characteristic lamellar-lipid inclusions.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Developmental Neurobiology, The Rockefeller University, New York, New York 10021, USA. plf3@columbia.edu

ABSTRACT
Zellweger syndrome is a peroxisomal biogenesis disorder that results in abnormal neuronal migration in the central nervous system and severe neurologic dysfunction. The pathogenesis of the multiple severe anomalies associated with the disorders of peroxisome biogenesis remains unknown. To study the relationship between lack of peroxisomal function and organ dysfunction, the PEX2 peroxisome assembly gene (formerly peroxisome assembly factor-1) was disrupted by gene targeting. Homozygous PEX2-deficient mice survive in utero but die several hours after birth. The mutant animals do not feed and are hypoactive and markedly hypotonic. The PEX2-deficient mice lack normal peroxisomes but do assemble empty peroxisome membrane ghosts. They display abnormal peroxisomal biochemical parameters, including accumulations of very long chain fatty acids in plasma and deficient erythrocyte plasmalogens. Abnormal lipid storage is evident in the adrenal cortex, with characteristic lamellar-lipid inclusions. In the central nervous system of newborn mutant mice there is disordered lamination in the cerebral cortex and an increased cell density in the underlying white matter, indicating an abnormality of neuronal migration. These findings demonstrate that mice with a PEX2 gene deletion have a peroxisomal disorder and provide an important model to study the role of peroxisomal function in the pathogenesis of this human disease.

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Immunofluorescence staining of wild-type and PEX2  mutant mouse fibroblasts. Wild-type (A, C, and E) and homozygous mutant (B, D, and F) fibroblasts were stained with antibodies against catalase (A and B), peroxisomal 3-ketoacyl-CoA thiolase (C and D), and rat liver peroxisomal integral membrane  proteins (E and F). The mutant fibroblasts assemble peroxisomal  membrane proteins into punctate structures in the cell but are  unable to import the matrix proteins catalase and thiolase into  the peroxisome. Bar, 16 μm.
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Figure 2: Immunofluorescence staining of wild-type and PEX2 mutant mouse fibroblasts. Wild-type (A, C, and E) and homozygous mutant (B, D, and F) fibroblasts were stained with antibodies against catalase (A and B), peroxisomal 3-ketoacyl-CoA thiolase (C and D), and rat liver peroxisomal integral membrane proteins (E and F). The mutant fibroblasts assemble peroxisomal membrane proteins into punctate structures in the cell but are unable to import the matrix proteins catalase and thiolase into the peroxisome. Bar, 16 μm.

Mentions: To determine the cellular localization of peroxisomal matrix and membrane proteins, fibroblast cultures were derived from skin of newborn mice and stained by immunofluorescence using antibodies against catalase, peroxisomal 3-ketoacyl-CoA thiolase, and rat liver peroxisomal integral membrane proteins (PxIMPs). In control fibroblasts, the matrix markers catalase and thiolase show a punctate pattern of immunofluorescence typical of peroxisomes (Fig. 2, A and C). Fibroblasts derived from PEX2-deficient mice show only diffuse cytoplasmic staining with these antibodies (Fig. 2, B and D). Thus, both peroxisomal targeting signal (PTS) pathways for import of peroxisomal matrix proteins, as defined here by catalase (PTS1) and thiolase (PTS2), are disrupted in the mutant fibroblasts. Assembly of peroxisomal membrane proteins into “membrane ghosts” (Santos et al., 1988) can be identified in PEX2-deficient fibroblasts with the anti-PxIMP antibody (Fig. 2 F). As has been described for Zellweger fibroblasts, the membrane ghosts are generally larger in size and fewer in number than normal peroxisomes (compare with Fig. 2 C) and are often found in small clusters. Thus, integral membrane proteins of the peroxisome are assembled in fibroblasts of PEX2-deficient mice, but matrix proteins are not imported into the organelle.


Targeted deletion of the PEX2 peroxisome assembly gene in mice provides a model for Zellweger syndrome, a human neuronal migration disorder.

Faust PL, Hatten ME - J. Cell Biol. (1997)

Immunofluorescence staining of wild-type and PEX2  mutant mouse fibroblasts. Wild-type (A, C, and E) and homozygous mutant (B, D, and F) fibroblasts were stained with antibodies against catalase (A and B), peroxisomal 3-ketoacyl-CoA thiolase (C and D), and rat liver peroxisomal integral membrane  proteins (E and F). The mutant fibroblasts assemble peroxisomal  membrane proteins into punctate structures in the cell but are  unable to import the matrix proteins catalase and thiolase into  the peroxisome. Bar, 16 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2140200&req=5

Figure 2: Immunofluorescence staining of wild-type and PEX2 mutant mouse fibroblasts. Wild-type (A, C, and E) and homozygous mutant (B, D, and F) fibroblasts were stained with antibodies against catalase (A and B), peroxisomal 3-ketoacyl-CoA thiolase (C and D), and rat liver peroxisomal integral membrane proteins (E and F). The mutant fibroblasts assemble peroxisomal membrane proteins into punctate structures in the cell but are unable to import the matrix proteins catalase and thiolase into the peroxisome. Bar, 16 μm.
Mentions: To determine the cellular localization of peroxisomal matrix and membrane proteins, fibroblast cultures were derived from skin of newborn mice and stained by immunofluorescence using antibodies against catalase, peroxisomal 3-ketoacyl-CoA thiolase, and rat liver peroxisomal integral membrane proteins (PxIMPs). In control fibroblasts, the matrix markers catalase and thiolase show a punctate pattern of immunofluorescence typical of peroxisomes (Fig. 2, A and C). Fibroblasts derived from PEX2-deficient mice show only diffuse cytoplasmic staining with these antibodies (Fig. 2, B and D). Thus, both peroxisomal targeting signal (PTS) pathways for import of peroxisomal matrix proteins, as defined here by catalase (PTS1) and thiolase (PTS2), are disrupted in the mutant fibroblasts. Assembly of peroxisomal membrane proteins into “membrane ghosts” (Santos et al., 1988) can be identified in PEX2-deficient fibroblasts with the anti-PxIMP antibody (Fig. 2 F). As has been described for Zellweger fibroblasts, the membrane ghosts are generally larger in size and fewer in number than normal peroxisomes (compare with Fig. 2 C) and are often found in small clusters. Thus, integral membrane proteins of the peroxisome are assembled in fibroblasts of PEX2-deficient mice, but matrix proteins are not imported into the organelle.

Bottom Line: The mutant animals do not feed and are hypoactive and markedly hypotonic.They display abnormal peroxisomal biochemical parameters, including accumulations of very long chain fatty acids in plasma and deficient erythrocyte plasmalogens.Abnormal lipid storage is evident in the adrenal cortex, with characteristic lamellar-lipid inclusions.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Developmental Neurobiology, The Rockefeller University, New York, New York 10021, USA. plf3@columbia.edu

ABSTRACT
Zellweger syndrome is a peroxisomal biogenesis disorder that results in abnormal neuronal migration in the central nervous system and severe neurologic dysfunction. The pathogenesis of the multiple severe anomalies associated with the disorders of peroxisome biogenesis remains unknown. To study the relationship between lack of peroxisomal function and organ dysfunction, the PEX2 peroxisome assembly gene (formerly peroxisome assembly factor-1) was disrupted by gene targeting. Homozygous PEX2-deficient mice survive in utero but die several hours after birth. The mutant animals do not feed and are hypoactive and markedly hypotonic. The PEX2-deficient mice lack normal peroxisomes but do assemble empty peroxisome membrane ghosts. They display abnormal peroxisomal biochemical parameters, including accumulations of very long chain fatty acids in plasma and deficient erythrocyte plasmalogens. Abnormal lipid storage is evident in the adrenal cortex, with characteristic lamellar-lipid inclusions. In the central nervous system of newborn mutant mice there is disordered lamination in the cerebral cortex and an increased cell density in the underlying white matter, indicating an abnormality of neuronal migration. These findings demonstrate that mice with a PEX2 gene deletion have a peroxisomal disorder and provide an important model to study the role of peroxisomal function in the pathogenesis of this human disease.

Show MeSH
Related in: MedlinePlus