PROLINE-RICH-PROTEIN PROMOTERS DIRECT LACZ EXPRESSION TO THE GRANULARCONVOLUTED TUBULAR CELLS OF THE SUBMANDIBULAR-GLAND IN ADULT TRANSGENIC MICE

The ability of two mouse PRP gene promoters to direct the expression o f the bacterial lacZ reporter gene was tested in transgenic mice. Tran sgenes A1-lacZ and C1-lacZ consisted of 8.2 kb A1 and 7.8 kb C1 PRP pr omoters respectively fused to the lacZ coding sequence. A1 and C1 are two A-type PRP genes isolated from the inbred SWR mice, which show the same gene structure and similar sequence to the closely related MP2 a nd M14 PRP genes previously cloned from outbred CD-1 mice. We here sho w that both A1-lacZ and C1-lacZ transgenes have very similar expressio n patterns: (1) they expressed the lacZ gene in all 14 established tra nsgenic lines under normal (non-stimulated) conditions; (2) the expres sion was restricted to the granular convoluted tubular cells of the su bmandibular glands; (3) the expression was developmentally regulated b eginning at sexual maturation and lasting to at least 1.5 years of age ; and (4) expression in some lines was probably influenced by sex horm ones, since higher expression was found in males than in females. A1-l acZ and C1-lacZ are the first transgenes derived from the PRP/GRP (glu tamine/glutamic acid-rich protein) gene superfamily to be expressed in the granular convoluted tubular cells (with known endocrine functions ), rather than in the acinar cells (with mainly exocrine functions) of the submandibular glands.