Expression patterns of Twist and Fgfr1, -2 and -3 in the developing mouse coronal suture suggest a key role for Twist in suture initiation and biogenesis
D. Johnson et al., Expression patterns of Twist and Fgfr1, -2 and -3 in the developing mouse coronal suture suggest a key role for Twist in suture initiation and biogenesis, MECH DEVEL, 91(1-2), 2000, pp. 341-345
Sutural growth depends on maintenance of a balance between proliferation of
osteogenic stem cells and their differentiation to form new bone, so that
the stem cell population is maintained until growth of the skull is complet
e. The identification of heterozygous mutations in FGFR1, -2 and -3 and TWI
ST as well as microdeletions of TWIST in human craniosynostosis syndromes h
as highlighted these genes as playing important roles in maintaining the su
ture as a growth centre. In contrast to Drosophila, a molecular relationshi
p between human (or other vertebrate) TWIST and FGFR genes has not yet been
established TWIST mutations exert their effect via haploinsufficiency wher
eas FGFR mutations have a gain-of-function mechanism of action. To investig
ate the biological basis of FGFR signalling pathways in the developing calv
arium we compared the expression patterns of Twist with those of Fgfr1, -2
and -3 in the fetal mouse coronal suture over the course of embryonic days
14-18, as the suture is initiated and matures. Our results show that: (1) T
wist expression precedes that of Fgfr genes at the time of initiation of th
e coronal suture; (2) in contrast to Fgfr transcripts, which are localised
within and around the developing bone domains, Twist is expressed by the mi
dsutural mesenchyme cells. Twist expression domains show some overlap with
those of Fgfr2, which is expressed in the most immature (proliferating) ost
eogenic tissue. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.