CHARACTERIZATION OF THE MOUSE TRANSFORMING GROWTH-FACTOR-ALPHA GENE -ITS EXPRESSION DURING EYELID DEVELOPMENT AND IN WAVED-1 TISSUES

The spontaneous mouse waved 1 (wa1) mutation is allelic with the trans forming growth factor alpha (TGF-alpha) gene and produces phenotypes s imilar to those of TGF-alpha knockout mice, Here, we show that TGF-alp ha mRNA and protein levels are measurable in wa1 tissues but reduced 5 - to 30-fold relative to wild type. Because the wa1-coding sequence is identical to that of the normal mRNA, wa1 is not a null mutation, Nuc lear run-on analyses revealed decreased transcription of the TGF-alpha gene in wa1 tissues, but the sequence of a 3.2-kb 5' flanking fragmen t containing the promoter was unaltered, Moreover, pulsed field gel el ectrophoresis analysis did not reveal alterations within 750 kb upstre am or 350 kb downstream of the gene, and chromosome 6 was karyotypical ly normal, Hence, we speculate that the wa1 mutation may be subtle and /or reside at a greater distance from the TGF-alpha gene. TGF-alpha de ficiency elicits a spectrum of variably penetrant eye anomalies in wa1 and knockout mice that are associated with open eyes at birth, We fou nd that late-gestation wa1 and TGF-alpha-null embryos display a signif icant delay in eyelid closure, although the eyes of most embryos fuse prior to birth, In situ hybridization localized TGF-alpha expression t o the advancing margins of the eyelid epithelium and epidermal growth factor receptor expression throughout the eyelid and corneal epithelia , These results suggest that eye problems observed in TGF-alpha-defici ent adult mice arise from premature exposure and trauma to open eyes d uring or following parturition.