Gli Activity Is Critical at Multiple Stages of Embryonic Mammary and Nipple Development

Abstract

Gli3 is a transcriptional regulator of Hedgehog (Hh) signaling that functions as a repressor (Gli3R) or activator (Gli3A) depending upon cellular context. Previously, we have shown that Gli3R is required for the formation of mammary placodes #3 and #5. Here, we report that this early loss of Gli3 results in abnormal patterning of two critical regulators: Bmp4 and Tbx3, within the presumptive mammary rudiment (MR) #3 zone. We also show that Gli3 loss leads to failure to maintain mammary mesenchyme specification and loss of epithelial Wnt signaling, which impairs the later development of remaining MRs: MR#2 showed profound evagination and ectopic hairs formed within the presumptive areola; MR#4 showed mild invagination defects and males showed inappropriate retention of mammary buds in Gli3xt/xt mice. Importantly, mice genetically manipulated to misactivate Hh signaling displayed the same phenotypic spectrum demonstrating that the repressor function of Gli3R is essential during multiple stages of mammary development. In contrast, positive Hh signaling occurs during nipple development in a mesenchymal cuff around the lactiferous duct and in muscle cells of the nipple sphincter. Collectively, these data show that repression of Hh signaling by Gli3R is critical for early placodal patterning and later mammary mesenchyme specification whereas positive Hh signaling occurs during nipple development.

Whole-genome resequencing of wild and domestic sheep identifies genes associated with morphological and agronomic traits

“…In particular, we detected seven novel genes (PHGDH, KDM3A, GLIS3, FSHR, CSN2, CSN1S1, and ROBO2; Supplementary Fig. 22b), which were reported to be associated with mammary and nipple development in mice 31,32 .…”

HOXC8 initiates an ectopic mammary program by regulating Fgf10 and Tbx3 expression, and Wnt/β-catenin signaling

“…Deletion of Gli3 causes inappropriate encroachment of hair follicles close to MR2, which itself protrudes abnormally from Gli3 mutant ectoderm, similar to cervical mammary placodes in W6cre/CAGC8 mutants. Interestingly, deletion of Gli3 also prevents the normal regression of mammary buds in male mice, comparable to the persistence of male MRs within the anterior ectopic zone of W6cre/CAGC8 mice (Chandramouli et al, 2013;Hatsell and Cowin, 2006;Lee et al, 2011Lee et al, , 2013Ulloa et al, 2007).…”

Microcephaly, dysmorphic features, corneal dystrophy, hairy nipples, underdeveloped labioscrotal folds, and small cerebellum in four patients

“…Tufts of hair extruding from the lactiferous ducts is a previously unreported finding in malformation syndromes, whereas it is known that mice with overexpression of the secreted Bmp antagonist Noggin show ectopic hair follicles extruding from the nipples [Mayer et al, ]. Gli3 loss or disturbed Hedgehog signaling also produce a similar nipple phenotype with ectopic hair follicles within the abnormally evaginated epithelial bud, and loss of sexual dimorphism [Chandramouli et al, ]. In addition to hairy nipples, Patient 2 had no breast development and axillary hair even after 3 years of menstruation, and Patient 1 had sparse, thin axillary hair in the postpubertal period, while he normally developed secondary sex characteristics.…”