A new mutation involving the sublingual gland in NFS/N mice. Partially arrested mucous cell differentiation.

A new mutation in mice affecting the mucous cell differentiation of the sublingual glands is described. The normal mouse sublingual glands are mucus-secreting and virtually all the acinar cells differentiate to mucus-rich cells by the day of birth. In contrast, all endpieces of newborn mutant mice consisted of acini of immature cuboidal cells. However, normal mucous cells, staining intensively with mucin-specific stains such as Alcian blue at pH 2.5 or mucicarmine, appeared in the mutant mice from an early age singly or in groups in a small number of acini, and their number apparently increased with age to occupy over 30% of the total acinar cells. Ultrastructurally, irregular secretion granules of varying electron-density, distinct from ordinary sublingual mucin granules, were frequently observed in the cytoplasm of the immature acinar cells in the mutant phenotype. The genetic analysis showed that a single autosomal recessive gene determined the observed abnormality. This is the first salivary gland mutation and will provide a critical model for the study of salivary mucous cell differentiation.