Evolutionary Patterns of Maternal Recognition of Pregnancy and Implantation in Eutherian Mammals

Author(s)

Braz, Henrique Bartolomeu ; Barreto, Rodrigo da Silva Nunes ; Silva-Junior, Leandro Norberto da ; Horvath-Pereira, Bianca de Oliveira ; Silva, Thamires Santos da ; Silva, Monica Duarte da ; Acuna, Francisco ; Miglino, Maria Angelica

• Document type: Journal article
• Source: ANIMALS; v. 14, n. 14, p. 13-pg., 2024-07-01.

Abstract

Simple Summary For a pregnancy to begin, the embryo must "communicate" its presence to the mother's body to prevent rejection. Also, the embryo must attach to the uterine lining (a process called implantation) to form the placenta, the organ that supports embryo growth. This review discusses how mammal embryos achieve these critical steps and how embryonic communication signals and implantation types have changed throughout mammalian history. Embryos release substances, such as proteins and hormones, to signal their presence to the mother's body. These signals are species-specific, indicating that mammals have developed diverse mechanisms for pregnancy recognition. Implantation varies across mammal species. In most mammals, embryos attach to the surface of the uterine lining. This type of implantation has existed since the first mammals appeared on Earth and is widespread today, occurring in elephants, squirrels, horses, cows, whales, and many others. In some species, embryos partially or fully embed within the uterine wall. These implantation types have arisen many times in distantly related mammals, such as bats, rats, and great apes, including humans. Despite recent advancements, there is still much to discover. Future research should prioritize certain rodent and bat species to better understand how pregnancy recognition and implantation have evolved over time.Abstract The implantation of the embryo into the maternal endometrium is a complex process associated with the evolution of viviparity and placentation in mammals. In this review, we provide an overview of maternal recognition of pregnancy signals and implantation modes in eutherians, focusing on their diverse mechanisms and evolutionary patterns. Different pregnancy recognition signals and implantation modes have evolved in eutherian mammals, reflecting the remarkable diversity of specializations in mammals following the evolution of viviparity. Superficial implantation is the ancestral implantation mode in Eutheria and its major clades. The other modes, secondary, partially, and primary interstitial implantation have each independently evolved multiple times in the evolutionary history of eutherians. Although significant progress has been made in understanding pregnancy recognition signals and implantation modes, there is still much to uncover. Rodents and chiropterans (especially Phyllostomidae) offer valuable opportunities for studying the transitions among implantation modes, but data is still scarce for these diverse orders. Further research should focus on unstudied taxa so we can establish robust patterns of evolutionary changes in pregnancy recognition signaling and implantation modes. (AU)

• FAPESP's process: 21/05445-7 - Functionalized tissue factory: bioengineering based on ecm interactions with biopolymers and bioprinting
• Grantee: Maria Angelica Miglino
• Support Opportunities: Research Projects - Thematic Grants