Cell influx and contractile actomyosin force drive mammary bud growth and invagination

Ewelina Trela, Qiang Lan, Satu-Marja Myllymäki, Clémentine Villeneuve, Riitta Lindström, Vinod Kumar, Sara A. Wickström, Marja L. Mikkola

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The mammary gland develops from the surface ectoderm during embryogenesis and proceeds through morphological phases defined as placode, hillock, bud, and bulb stages followed by branching morphogenesis. During this early morphogenesis, the mammary bud undergoes an invagination process where the thickened bud initially protrudes above the surface epithelium and then transforms to a bulb and sinks into the underlying mesenchyme. The signaling pathways regulating the early morphogenetic steps have been identified to some extent, but the underlying cellular mechanisms remain ill defined. Here, we use 3D and 4D confocal microscopy to show that the early growth of the mammary rudiment is accomplished by migration-driven cell influx, with minor contributions of cell hypertrophy and proliferation. We delineate a hitherto undescribed invagination mechanism driven by thin, elongated keratinocytes-ring cells-that form a contractile rim around the mammary bud and likely exert force via the actomyosin network. Furthermore, we show that conditional deletion of nonmuscle myosin IIA (NMIIA) impairs invagination, resulting in abnormal mammary bud shape.
Original languageEnglish
Article number202008062
JournalJournal of Cell Biology
Volume220
Issue number8
Number of pages26
ISSN0021-9525
DOIs
Publication statusPublished - 2 Aug 2021
MoE publication typeA1 Journal article-refereed

Bibliographical note

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Fields of Science

  • DIFFERENTIATION
  • LINE
  • MIGRATION
  • MORPHOGENESIS
  • MORPHOLOGY
  • MOUSE
  • POLARITY
  • PROLIFERATION
  • ROLES
  • SONIC-HEDGEHOG
  • 1182 Biochemistry, cell and molecular biology

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