UASt regulatory sequences drive expression of a cDNA that encodes prepro-Hsap\INS, mutated to carry the 'LB15YB16delinsH' variant identified in patients with permanent neonatal diabetes mellitus. In this variant, residues Leu15 and Tyr16 of the B-chain (which correspond to residues 39 and 40 of the preproinsulin sequence) are replaced by a single His residue.