Defective cytoplasmic granule formation. I. Abnormalities affecting tissue mast cells and pancreatic acinar cells of beige mice

Abstract

Beige mice (C57BL/6-bgJ/bgJ) express the Chediak-Higashi syndrome, a genetically determined constellation of morphologic and functional abnormalities affecting cells that synthesize cytoplasmic granules; a similar disorder also occurs in humans and several other mammalian species. We used a computer-assisted morphometric approach to identify and quantitate the effect of the beige mutation on the structure of mast cell or pancreatic acinar cell cytoplasmic granules. Beige and control mouse mast cell or pancreatic acinar cell granules exhibited periodic, multimodal distributions of equivalent volumes in which the modes fell at volumes that were integral multiples of the volume of the "unit granule," whose volume (the "unit volume" or v1) was defined by the first mode in the granule equivalent volume distribution. But the modal frequency of the C57BL/6-bgJ/bgJ mast cell granule equivalent volume distribution fell at v1, a pattern consistent with a haphazard pattern of "unit granule" fusion, whereas the corresponding modal frequency for the control mast cell granules fell at v3, a pattern consistent with a "unit addition" model of granule fusion. In addition, the unit volume of beige mouse mast cell granules was 18 times that of control mouse mast cell granules. By contrast, the unit volume of beige mouse pancreatic acinar cell granules was only slightly (23%) greater than that of control cells. C57BL/6-bgJ/bgJ and control cells did not differ significantly in total cell or nuclear volume, or in the aggregate volume of their cytoplasmic granules. However, C57BL/6-bgJ/bgJ mast cells or pancreatic acinar cells contained significantly fewer granules than did their normal counterparts. These findings are consistent with the hypothesis that the beige mutation affects the formation of unit granules and also alters the pattern of aggregation and fusion of unit granules. The data also identify quantitative differences in the expression of the beige mutation in mast cells and pancreatic acinar cells.