Identification of differentially expressed genes during a wool follicle growth cycle induced by prolactin

The wool follicles of New Zealand Wiltshire sheep can be induced to undergo growth cycles by manipulating circulating prolactin levels. Altered patter ns of gene expression through this cycle were examined using differential d isplay, and nine sequence tags for differentially expressed genes were isol ated. Four of these tags were identified as fragments of known genes, encod ing a wool keratin, KRTAP3.2, a desmosome component, desmoglein 1, an epith elial cell marker, stratifin, and a protein kinase, Clk3. All four genes we re shown to be downregulated in telogen skin compared with anagen, In situ hybridization showed that all had localization patterns which included cell s that are absent in telogen, The stratifin tag was used to clone a cDNA th at incorporated a complete open-reading frame for ovine stratifin. Ovine st ratifin is similar to the human form, showing only six single residue diffe rences in the predicted amino acid sequence. Stratifin probably acts as a r egulator of other proteins involved in trichocyte cell cycling and differen tiation, Clk3 is involved in regulating RNA splicing. KRTAP3.2 and Dsg1 bot h play structural roles in hair follicles, The other five tags, including t wo representing genes that were upregulated during catagen, could not be id entified by homology. Differential display is an effective means of identif ying genes involved in follicle function and, potentially, of genes control ling the growth cycle.