Journal of Mammary Gland Biology and Neoplasia

, Volume 18, Issue 2, pp 105–120

Evo-Devo of the Mammary Gland

Article

DOI: 10.1007/s10911-013-9290-8

Cite this article as:
Oftedal, O.T. & Dhouailly, D. J Mammary Gland Biol Neoplasia (2013) 18: 105. doi:10.1007/s10911-013-9290-8

Abstract

We propose a new scenario for mammary evolution based on comparative review of early mammary development among mammals. Mammary development proceeds through homologous phases across taxa, but evolutionary modifications in early development produce different final morphologies. In monotremes, the mammary placode spreads out to form a plate-like mammary bulb from which more than 100 primary sprouts descend into mesenchyme. At their distal ends, secondary sprouts develop, including pilosebaceous anlagen, resulting in a mature structure in which mammary lobules and sebaceous glands empty into the infundibula of hair follicles; these structural triads (mammolobular-pilo-sebaceous units or MPSUs) represent an ancestral condition. In marsupials a flask-like mammary bulb elongates as a sprout, but then hollows out; its secondary sprouts include hair and sebaceous anlagen (MPSUs), but the hairs are shed during nipple formation. In some eutherians (cat, horse, human) MPSUs form at the distal ends of primary sprouts; pilosebaceous components either regress or develop into mature structures. We propose that a preexisting structural triad (the apocrine-pilo-sebaceous unit) was incorporated into the evolving mammary structure, and coupled to additional developmental processes that form the mammary line, placode, bulb and primary sprout. In this scenario only mammary ductal trees and secretory tissue derive from ancestral apocrine-like glands. The mammary gland appears to have coopted signaling pathways and genes for secretory products from even earlier integumentary structures, such as odontode (tooth-like) or odontode-derived structures. We speculate that modifications in signal use (such as PTHrP and BMP4) may contribute to taxonomic differences in MPSU development.

Keywords

Evolution Mammary gland Lactation Signaling Morphogenesis 

Abbreviations

APSU

Apo-pilo-sebaceous unit

BMP

Bone morphogenic protein

CRL

Crown-rump length

EDA

Ectodysplasin

FGF

Fibroblast growth factor

Ihh

Indian hedgehog

MB

Mammary bulb

MG

Mammary gland

ML

Mammary line

MP

Mammary placode

MPSU

Mammolobular-pilo-sebaceous unit

mya

Million years ago

PS

Primary sprout

PTHrP

Parathyroid hormone-related protein

SG

Sebaceous gland

Shh

Sonic hedgehog

SS

Secondary sprout

Supplementary material

10911_2013_9290_MOESM1_ESM.docx (31 kb)
Supplemental Table 1(DOCX 31.1 kb)

Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.Smithsonian Environmental Research CenterEdgewaterUSA
  2. 2.FRE 3405 CNRS/UJF/EPHE Université Joseph Fourier Site SantéLa TroncheFrance

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