Tooth-type specific expression of dHAND/Hand2: possible involvement in murine lower incisor morphogenesis

Abstract

dHAND/Hand2 is a basic helix-loop-helix transcription factor required for the development of the heart, pharyngeal arches, and vasculature and is expressed during embryogenesis. However, there are no reports on the involvement of the dHAND gene in tooth development. In the present study, the expression of dHAND was examined in developing tooth germs of mice. The dHAND gene was expressed in the mesenchyme of the presumptive incisor region of the lower jaw at an early stage and in the mesenchyme of the lower incisor tooth germ at a later stage. However, the dHAND gene was not expressed in the upper incisor region or the upper and lower molar regions during jaw development. Treatment of tooth germ explants of lower incisors with antisense oligodeoxinucleotide (ODN) against dHAND prevented the differentiation of tooth germ cells, including ameloblasts and odontoblasts, the formation of dentin and enamel, and the proliferation of tooth germ cells and increased the apoptosis of tooth germ cells, suggesting that dHAND is essential for these cells during development. On the other hand, the treatment of tooth germ explants of upper incisor and upper or lower molars did not induce severe effects on their development. Treatment of the explants with basic fibroblast growth factor in association with antisense ODN partially rescued them from the effects of antisense ODN. The present results suggest that the dHAND gene plays important roles in type-specific development of lower incisors, and that basic fibroblast growth factor is involved downstream of the dHAND pathway in tooth germ cells.

Molars and incisors: show your microarray IDs

“…The top ten genes showing highest expression in incisors were Hpse2 , Alx1 , Hand2 , Sfrp4 , Pax3 , Alx3, Isl1, Mcpt2, Cacna2d3 and Irx4 (Table 1A). Interestingly, among these genes, four were already known to be differentially expressed, with Barx1 and Six2 preferentially expressed in molars [42,43] and Isl1 and Hand2 in incisors [29,44]. …”

Analysis of the Hand1 cell lineage reveals novel contributions to cardiovascular, neural crest, extra‐embryonic, and lateral mesoderm derivatives

“…Hand1 and Hand2 expression is observed within subpopulations of cranial, cardiac, trunk, and vagal/sacral NCCs that contribute to the jaw, cardiac OFT, sympathetic nervous system and enteric nervous system, respectively (Abe et al, 2002; Yanagisawa et al, 2003; Barbosa et al, 2007; Morikawa et al, 2007; Hendershot et al, 2008; Morikawa and Cserjesi, 2008; Holler et al, 2010). This expression can be observed in whole mount Hand1 LacZ expression at E12.5 (Fig.…”

Endothelin-A receptor-dependent and -independent signaling pathways in establishing mandibular identity

“…As Hand2 expression is confined to the lower jaw of developing embryos, (Ruest et al, 2003) and appears crucial for normal incisor development (Abe et al, 2002), this area may reflect one in which mandibular identity is not completely lost in the absence of Ednra signaling. Furthermore, an Ednra-independent signaling pathway leading to limited Hand2 expression in the distal arch could partially explain the presence of lower incisors in the jaw of Dlx5/Dlx6 -/-embryos.…”