A review of morphological techniques for detection of peroxisomal (and mitochondrial) proteins and their corresponding mRNAs during ontogenesis in mice: application to the PEX5-knockout mouse with Zellweger syndrome.

In the era of application of molecular biological gene-targeting technology for the generation of knockout mouse models to study human genetic diseases, the availability of highly sensitive and reliable methods for the morphological characterization of the specific phenotypes of these mice is of great importance. In the first part of this report, the role of morphological techniques for studying the biology and pathology of peroxisomes is reviewed, and the techniques established in our laboratories for the localization of peroxisomal proteins and corresponding mRNAs in fetal and newborn mice are presented and discussed in the context of the international literature. In the second part, the literature on the ontogenetic development of the peroxisomal compartment in mice, with special emphasis on liver and intestine is reviewed and compared with our own data reported recently. In addition, some recent data on the pathological alterations in the liver of the PEX5(-/-) mouse with a peroxisomal biogenesis defect are briefly discussed. Finally, the methods developed during these studies for the localization of mitochondrial proteins (respiratory chain complexes and MnSOD) are presented and their advantages and pitfalls discussed. With the help of these techniques, it is now possible to identify and distinguish unequivocally peroxisomes from mitochondria, two classes of cell organelles giving by light microscopy a punctate staining pattern in microscopical immunohistochemical preparations of paraffin-embedded mouse tissues.