title: Hoxc8 initiates an ectopic mammary program by regulating Fgf10 and Tbx3 expression and Wnt/β-catenin signaling.
abstract: The role of Hox genes in the formation of cutaneous accessory organs such as hair follicles and mammary glands has proved elusive, a likely consequence of overlapping function and expression among various homeobox factors. Lineage and immunohistochemical analysis of Hoxc8 in mice revealed that this midthoracic Hox gene has transient but strong regional expression in ventrolateral surface ectoderm at E10.5, much earlier than previously reported. Targeted mice were generated to conditionally misexpress Hoxc8 from the Rosa locus using select Cre drivers, which significantly expanded the domain of thoracic identity in mutant embryos. Accompanying this expansion was the induction of paired zones of ectopic mammary development in the cervical region, which generated between three and five pairs of mammary placodes anterior to the first wild-type mammary rudiment. These rudiments expressed the mammary placode markers Wnt10b and Tbx3 and were labeled by antibodies to the mammary mesenchyme markers ERα and androgen receptor. Somitic Fgf10 expression, which is required for normal mammary line formation, was upregulated in mutant cervical somites, and conditional ablation of ectodermal Tbx3 expression eliminated all normally positioned and ectopic mammary placodes. We present evidence that Hoxc8 participates in regulating the initiation stages of mammary placode morphogenesis, and suggest that this and other Hox genes are likely to have important roles during regional specification and initiation of these and other cutaneous accessory organs.
authors.affiliation: Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA lsc3@utah.edu.
authors.forename: Lara S
authors.initials: LS
authors.lastname: Carroll
authors.affiliation: Department of Human Genetics and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: Mario R
authors.initials: MR
authors.lastname: Capecchi
mesh_terms: D000818:Animals; D019521:Body Patterning; D019070:Cell Lineage; D004475:Ectoderm / Q000378:metabolism; D005260:Female; D051526:Fibroblast Growth Factor 10 / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D005838:Genotype; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007763:Lac Operon; D008297:Male; D008648:Mesoderm / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D015854:Up-Regulation; D060449:Wnt Signaling Pathway
chemical_list: C496464:Fgf10 protein, mouse; D051526:Fibroblast Growth Factor 10; D018398:Homeodomain Proteins; C489816:Hoxc8 protein, mouse; D020825:T-Box Domain Proteins; C491460:Tbx3 protein, mouse; D049452:Green Fluorescent Proteins
keywords: Fgf10; Hoxc8; Mammary placodes; Mouse; Skin appendages; Tbx3; Vibrissae; Wnt signaling