Homeobox Protein, Hmx3, in Postnatally Developing Rat Submandibular Glands

Abstract

S U M M A R Y Homeobox-containing (Hox) genes play important roles in development, particularly in the development of neurons and sensory organs, and in specification of body plan. The Hmx gene family is a new class of homeobox-containing genes defined by a conserved homeobox region and a characteristic pattern of expression in the central nervous system that is more rostral than that of the Hox genes. To date, three closely related members of the Hmx family, Hmx1, Hmx2, and Hmx3, have been described. All three Hmx genes are expressed in the craniofacial region of developing embryos. Here we show, for the first time, the expression of the transcription factor Hmx3 in postnatally developing salivary glands. Hmx3 protein is expressed in a cell type-specific manner in rat salivary glands. Hmx3 is present in both the nuclei and cytoplasm of specific groups of duct cells of the submandibular, parotid, and sublingual glands. Hmx3 expression increases during postnatal development of the submandibular gland. The duct cells show increasing concentrations of Hmx3 protein with progressive development of the submandibular gland. In contrast, the acinar cells of the three salivary glands do not exhibit detectable levels of Hmx3 protein.

The HMX homeodomain protein MLS-2 regulates cleavage orientation, cell proliferation and cell fate specification in theC. eleganspostembryonic mesoderm

“…This homeodomain is most similar to that of the Nkx5 family of homeodomain proteins, also known as the HMX family. The HMX gene family is present in many organisms from sea urchins to humans (Adamska et al, 2000;Adamska et al, 2001;Bober et al, 1994;Deitcher et al, 1994;Herbrand et al, 1998;Martinez and Davidson, 1997;RinkwitzBrandt et al, 1995;Rinkwitz-Brandt et al, 1996;Shaw et al, 2003;Stadler et al, 1992;Stadler et al, 1995;Stadler and Solursh, 1994;Wang et al, 1990;Wang et al, 2000;Yoshiura et al, 1998). HMX proteins share homology in the Development 132 (18) Research article homeodomain and in two additional regions immediately Cterminal to the homeodomain (Wang et al, 2000;Yoshiura et al, 1998).…”

“…Expression of HMX proteins outside of the nervous system and the sensory organs has been reported, and mice lacking Hmx3 show inner ear defects and maternal reproductive defects (Martinez and Davidson, 1997;Shaw et al, 2003;Stadler and Solursh, 1994;Wang et al, 1998). Therefore, like mls-2, the Hmx genes in other organisms might also be expressed and functioning in additional cell types, especially during postembryonic development.…”

Tlx1 regulates acinar and duct development in mouse salivary glands

“…Several other transcription factors have been localized to salivary gland duct cells or duct cell precursors. These include SGN1/ASCL3 (Bullard et al., 2008; Yoshida et al., 2001), CP2L1 (Yamaguchi et al., 2006), SIX1 (Leclef et al., 2003), IRF6 (Metwalli et al., 2018; Tamasas & Cox, 2017), YAP (Szymaniak et al., 2017), CREB (Amano & Iseki, 1998), RUNX1/RUNX2/CBFβ (Islam et al., 2015; Minagi et al., 2017), NRF2 and FOXA1 (Suzuki et al., 2019), EHF (Song et al., 2022), HMX3 (Shaw et al., 2003), JUND (Hipkaeo et al., 2004), ELF5 (Lapinskas et al., 2004) and CRTC1 (Jaskoll et al., 2011). In some cases, the transcription factors were localized to cells of all duct regions, whereas in others, the transcription factors were restricted to specific duct regions, or subsets of cells within the ducts.…”