High impact information on Barx1

• BMP4 was shown to inhibit expression of the homeobox gene Barx-1 and to restrict expression to the proximal, presumptive molar mesenchyme of mouse embryos at embryonic day 10 [1].
• The inhibition of BMP signaling early in mandible development by the action of exogenous Noggin protein resulted in ectopic Barx-1 expression in the distal, presumptive incisor mesenchyme and a transformation of tooth identity from incisor to molar [1].
• Localization studies showed that expression of Barx1 and Barx2 overlap in the nervous system, particularly in the telencephalon, spinal cord, and dorsal root ganglia [2].
• Ectopic expression of Islet1 in proximal epithelium produces a loss of Barx1 expression in the mesenchyme and resulted in inhibition of molar tooth development [3].
• Using molecular markers of branchial arch neural crest (Barx1) and commitment to chondrogenic differentiation (Sox9), we show that this population alters its fate from odontogenic to become chondrogenic [4].

Biological context of Barx1

• Expression of the transcription factors Otlx2, Barx1 and Sox9 during mouse odontogenesis [5].
• During mouse embryonic development, the Barx1 homeobox gene is expressed in the mesenchymal cells of molar teeth and stomach [6].
• Additionally, Barx1 null mouse embryos show visceral homeosis, with intestinal gene expression within a highly disorganized gastric epithelium [7].

Anatomical context of Barx1

• The recently identified homeodomain transcription factor Barx1 is first expressed in mesenchyme of the first branchial arch, but during advanced developmental stages the gene is exclusively expressed in the mesenchyme of molar primordia [5].
• Finally, we compare Otlx2 expression with that of the recently identified homeodomain transcription factor Barx1 expressed in molar mesenchyme [8].
• At day 16.5, all locations other than the developing molars had become Barx1-negative [9].
• An intriguing feature is the restriction of Barx1 expression to the molars suggesting a role in the differentiation of molars from incisors [9].
• Barx1 already marks the future stomach region of the primitive gut at embryonic day 9.5 and is present in the mesenchymal wall of the stomach up to day 16 [9].

Analytical, diagnostic and therapeutic context of Barx1

• Sequence analysis indicated that human BARX1, mouse Barx1, and chick Barx1 show 100% identity at the amino acid level within their homeodomains [10].

References