Journal of Mammary Gland Biology and Neoplasia

, Volume 11, Issue 3, pp 187–203

The Mammary Bud as a Skin Appendage: Unique and Shared Aspects of Development

Authors

  • Marja L. Mikkola
    • Developmental Biology Program, Institute of BiotechnologyUniversity of Helsinki
    • Departments of Dermatology and Cell and Developmental BiologyUniversity of Pennsylvania School of Medicine
    • Department of DermatologyUniversity of Pennsylvania School of Medicine
Article

DOI: 10.1007/s10911-006-9029-x

Cite this article as:
Mikkola, M.L. & Millar, S.E. J Mammary Gland Biol Neoplasia (2006) 11: 187. doi:10.1007/s10911-006-9029-x

Abstract

Like other skin appendages, the embryonic mammary gland develops via extensive epithelial–mesenchymal interactions. Early stages in embryonic mammary development strikingly resemble analogous steps in the development of hair follicles and teeth. In each case the first morphological sign of development is a localized thickening in the surface epithelium that subsequently invaginates to form a mammary, hair follicle or tooth bud. Similar sets of intersecting signaling pathways are involved in patterning the mammary, hair follicle and dental epithelium, directing placode formation, and controlling bud invagination. Despite these similarities, subsequent events in the formation of these appendages are diverse. The mammary bud extends to form a sprout that begins to branch upon contact with the mammary fat pad. Hair follicles also extend into the underlying mesenchyme, but instead of branching, hair follicle epithelium folds around a condensation of dermal cells. In contrast, teeth undergo a more complex folding morphogenesis. Here, we review what is known of the molecular and cellular mechanisms controlling early steps in the development of these organs, attempt to unravel both common themes and unique aspects that can begin to explain the diversity of appendage formation, and discuss human genetic diseases that affect appendage morphogenesis.

Keywords

Mammary placode Mammary bud Appendage Hair follicle Tooth Ectodermal Epidermis Embryo

Abbreviations

ADULT

acro-dermato-ungual-lacrimal-tooth syndrome

APC

adenomatous Polyposis Coli

AREG

Amphiregulin

AEC

ankyloblepharon-ectodermal dysplasia-clefting syndrome

BCC

basal cell carcinoma

BMP

bone morphogenetic protein

DKK1

Dickkopf 1

EDA

Ectodysplasin

EDAR

edctodysplasin receptor

EEC

ectrodactyly-ectodermal-dysplasia-clefting syndrome

E

embryonic day

FGFR

fibroblast growth factor receptor

LMS

limb-mammary syndrome

NRG3

Neuregulin 3

SHFM

non-syndromic split-hand/split-foot malformation

PTHrP

parathyroid hormone-related protein

SEM

scanning electron microscopy

SHH

Sonic hedgehog

Copyright information

© Springer Science+Business Media, LLC 2006