Abstract
Natural mutations in the LIPH gene were shown to be responsible for hair growth defects in humans and for the rex short hair phenotype in rabbits. In this species, we identified a single nucleotide deletion in LIPH (1362delA) introducing a stop codon in the C-terminal region of the protein. We investigated the expression of LIPH between normal coat and rex rabbits during critical fetal stages of hair follicle genesis, in adults and during hair follicle cycles. Transcripts were three times less expressed in both fetal and adult stages of the rex rabbits than in normal rabbits. In addition, the hair growth cycle phases affected the regulation of the transcription level in the normal and mutant phenotypes differently. LIPH mRNA and protein levels were higher in the outer root sheath (ORS) than in the inner root sheath (IRS), with a very weak signal in the IRS of rex rabbits. In vitro transfection shows that the mutant protein has a reduced lipase activity compared to the wild type form. Our results contribute to the characterization of the LIPH mode of action and confirm the crucial role of LIPH in hair production.
Highlights
In rabbits, hair follicles are structured into groups, usually constituted of one central primary hair follicle surrounded by 2–4 lateral primary hair follicles and by 20–50 secondary down hair follicles (Figure 1)
Normal rabbit fur is composed of three different types of hairs: guard hairs produced by central primary hair follicles (3– 4 cm long for a diameter of 50–60 mm), awn hairs produced by lateral primary hair follicles (3–3.5 cm/25–30 mm) which both constitute the physical ‘‘outer coat’’ protection, and down hairs produced by secondary hair follicles (2.5–3 cm/15 mm), and the inner coat for thermal protection
LIPH expression during fetal hair follicle development The organization of the cell structures observed after Roan staining of the skin sections validated the expected timing of the formation of the different types of hair follicles (HF) in normal rabbits (Figure 1, row B2)
Summary
Hair follicles are structured into groups, usually constituted of one central primary hair follicle surrounded by 2–4 lateral primary hair follicles and by 20–50 secondary down hair follicles (Figure 1). A deletion of a single nucleotide in exon 9 of the LIPH gene (1362delA) was identified in rex rabbits [3]. This mutation results in a frameshift and introduces a premature stop codon shortening the predicted protein by 19 aminoacids. In 2006, a deletion in the LIPH gene was identified as being responsible for Hypotrichosis Simplex (HS) in 50 families of Russian people [6] Hairs of these patients are abnormally short, dystrophic and fragile due to retarded or arrested hair growth. The activity of both normal and mutant proteins was estimated in vitro using transfected mammalian cell cultures
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