B. Favier et al., Localisation of members of the notch system and the differentiation of vibrissa hair follicles: Receptors, ligands, and fringe modulators, DEV DYNAM, 218(3), 2000, pp. 426-437
Hair vibrissa follicle morphogenesis involves several cell segregation phas
es, in the dermis as well as in the epidermis. The expression of Notch-rela
ted genes, which are well established mediators of multiple cell segregatio
n events in Drosophila development, was studied by in situ hybridisation du
ring embryonic mouse vibrissa follicle morphogenesis and the first adult ha
ir cycle. The results show that two receptors, Notch1 and -2, three ligands
, Delta1, Serrate1, and -2, and the three Fringe regulators, Lunatic, Manic
, and Radical, are expressed in different locations and morphogenetic stage
s. First, the appearance of hair vibrissa primordia involves the expression
of complementary patterns of Notch2, Delta1, and Lunatic Fringe in the der
mis and of Notch1, Serrate2, and Lunatic Fringe in the epidermis. Second, t
his expression pattern is no longer found after stage 3 in the dermis. Mean
while, in the epidermis, the expression of Notch1, Serrate2, and Lunatic Fr
inge before the formation of the placode may be involved in determining two
populations of epidermal cells in the developing follicle. Third, compleme
ntary expression patterns for Notch1, Manic, and Lunatic Fringe, as well as
Serrate1 and -2 as previously shown (Powell et al., 1998), are progressive
ly established from stage 4 of embryonic development both in the outer root
sheath and in the hair matrix. These patterns are consistent with the one
found in the adult anagen phase. During the hair vibrissa cycle, Notch1 and
Manic Fringe display temporal and spatial changes of expression, suggestin
g that they may intervene as modulators of trichocyte activities. (C) 2000
Wiley-Liss, Inc.