The bicoid-related homeoprotein Ptx1 defines the most anterior domain of the embryo and differentiates posterior from anterior lateral mesoderm

Abstract

Ptx1 is a member of the small bicoid family of homeobox-containing genes; it was isolated as a tissue-restricted transcription factor of the pro-opiomelanocortin gene. Its expression during mouse and chick embryogenesis was determined by in situ hybridization in order to delineate its putative role in development. In the head, Ptx1 expression is first detected in the ectoderm-derived stomodeal epithelium at E8.0. Initially, expression is only present in the stomodeum and in a few cells of the rostroventral foregut endoderm. A day later, Ptx1 mRNA is detected in the epithelium and in a streak of mesenchyme of the first branchial arch, but not in other arches. Ptx1 expression is maintained in all derivatives of these structures, including the epithelia of the tongue, palate, teeth and olfactory system, and in Rathke's pouch. Expression of Ptx1 in craniofacial structures is strikingly complementary to the pattern of goosecoid expression. In addition, Ptx1 is expressed early (E6.8) in posterior and extraembryonic mesoderm, and in structures that derive from these. The restriction of expression to the posterior lateral plate is later evidenced by exclusive labelling of the hindlimb but not forelimb mesenchyme. In the anterior domain of expression, the stomodeum was shown by fate mapping to derive from the anterior neural ridge (ANR) which represents the most anterior domain of the embryo. The concordance between these fate maps and the stomodeal pattern of Ptx1 expression supports the hypothesis that Ptx1 defines a stomodeal ectomere, which lies anteriorly to the neuromeres that have been suggested to constitute units of a segmented plan directing head formation.

Ptx1 regulates SF-1 activity by an interaction that mimics the role of the ligand-binding domain

“…To date, three Ptx genes have been cloned from various species (reviewed in Drouin et al, 1998a,b;Gage et al, 1999): Ptx1 (Pitx1) (Lamonerie et al, 1996;Muccielli et al, 1996;Szeto et al, 1996;Shang et al, 1997;Vorbruggen et al, 1997), Ptx2 also known as Pitx2 or Otlx2 (Muccielli et al, 1996;Semina et al, 1996;Gage and Camper, 1997) and Ptx3 (Semina et al, 1997;Smidt et al, 1997). Ptx1, the founding member of this family, was cloned initially as a regulator of pro-opiomelanocortin (POMC) gene expression in pituitary corticotrope cells (Lamonerie et al, 1996), but was later found to be a pan-pituitary regulator of transcription (Tremblay et al, 1998) and to be required for mandible and hindlimb development (Lancto ˆt et al, 1999b;Szeto et al, 1999) in agreement with its expression during development (Lancto ˆt et al, 1997). Ptx2 was first identified as the causative gene for Rieger's syndrome (Semina et al, 1996) and it was recently shown to be an effector for development of left-right asymmetry of lateral mesoderm plate derivatives such as heart and stomach (Logan et al, 1998;Piedra et al, 1998;Ryan et al, 1998;Yoshioka et al, 1998;Campione et al, 1999).…”

“…Ptx2 was first identified as the causative gene for Rieger's syndrome (Semina et al ., 1996) and it was recently shown to be an effector for development of left–right asymmetry of lateral mesoderm plate derivatives such as heart and stomach (Logan et al ., 1998; Piedra et al ., 1998; Ryan et al ., 1998; Yoshioka et al ., 1998; Campione et al ., 1999). Expression of Ptx1 and Ptx2 is detected in the stomodeum at embryonic day 8 (E8) and, subsequently, is maintained in all stomodeal derivatives, including Rathke's pouch, the pituitary anlage (Muccielli et al ., 1996; Lanctôt et al ., 1997; 1999a). Thus, Ptx1 and Ptx2 represent the earliest known markers of pituitary organogenesis and may have redundant activity in this tissue.…”

Making a head: Neural crest and ectodermal placodes in cranial sensory development

“…Indeed, these two structures also share homologues of important otic genes like Pax2/8 that are expressed within the atrium of ascidians [127,250]. Hatschek's pit also shares expression of Pitx with Rathke's pouch, further supporting a potential evolutionary origin of these placodes [25,74,134,265].…”

CellNeighborEX: deciphering neighbor‐dependent gene expression from spatial transcriptomics data

“…We used the seqFISH data pre-processed by Squidpy (Palla et al, 2022a;Data ref: Palla et al, 2022b). After defining immediate neighbors using Delaunay triangulation (Delaunay, 1934) (Lanctôt et al, 1997;Chung et al, 2010;Tran & Kioussi, 2021).…”