In the stratum granulosum of the skin, keratinocytes are filled with basophilic keratohyaline granules. These granules form as a result of which intracellular process?
a. Accumulation of hyaluronic acid
b. Degeneration of mitochondria
c. Formation of aggregations of profilaggrin
d. Fragmentation of the nucleus during keratinocyte apoptosis
e. Synthesis of hemidesmosomes
ANS: C
The highly phosphorylated protein, profilaggrin, forms aggregates in the stratum granulosum that are basophilic as a result of the negative charge on the protein. When profilaggrin is dephosphorylated and cleaved in the stratum corneum, its basophilia disappear, so that keratohy-aline granules are no longer apparent.
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