Investigation on the effects of insulin-like growth factor 1 on hair and fibre growth in mice and sheep and differentially expressed genes from mouse skin at different stages of hair growth cycle

Abstract

Many studies have been undertaken to investigate the effects of growth factors on hair and fibre growth. Insulin-like growth factor 1 (IGF1) has been reported to be a potent stimulator of cellular proliferation and differentiation of skin and hair follicle.

The first study was to investigate the effect of IGF1 on vibrissa growth in IGF treated mice. Further investigation on vibrissa and wool growth was undertaken in IGF1 transgenic mice and sheep, respectively.

Mice treated with IGF1 demonstrated no effect on vibrissa growth at days 6-14 of the first neonatal hair growth cycle, while vibrissa growth at days 11-21 after birth was increased 16% for IGF1 transgenic mice compared to their non-transgenic littermates. IGF1 transgenic sheep showed a 7.1 % increase in clean fleece weight at yearling shearing compared to their non-transgenic half-sibs. Although the clean fleece weight for transgenics was greater than non-transgenics in the second year, the difference between the two groups was not statistically significant.

The rate of hair fibre growth is determined by the proliferation of cells in the follicle bulb and their subsequent growth and migration. The second part of this study was to identify genes that are differentially expressed in mouse skin during different hair growth stages of the first neonatal cycle. This may provide an insight into follicle bulb-specific promoters and the selection of such candidate genes for transgenesis.

Using mRNA differential display techniques, four differentially expressed genes were identified from mouse skin during different developmental stages of the first hair growth cycle. One message corresponding to a G-α protein of mouse S49 cells expressed in both day 2 and day 3 of mouse age. The remaining differentially expressed genes were found both in day 3 and day 4 but not in day 2. DNA sequences for two of the day 2- and day 3-specific messages did not show significant homology with known genes and may be candidates of follicle bulb-specific messages. They may also correspond to the 3' untranslated regions of mRNA.