Biology subjects

Bergman, A. J.

Publications and source records attributed to Bergman, A. J..

3 recordsLinked to original sources

bioRxiv2025

Endogenous retrovirus IAP forms virus-like particles and traffics across the maternal-fetal barrier

For 50 years, virus-like particles (VLPs) have been observed in the placentas of many species, but their source and function remain unexplored. Here, we identify intracisternal a-type particle (IAP) elements, specifically the IAPEz-int family, as the likely source of VLPs in the mouse placenta. IAPEz-int instances are expressed throughout placentation and contain intact gag and env sequences critical for the formation of immature and mature particles, respectively. To elucidate a role for IAPEz-int derived VLPs in the mouse placenta, we generated a knock-in mouse containing a full-length element tagged with HA/FLAG. Using this line, we demonstrate that fetal IAPEz-int traffics into and across the maternal decidua. In total, we suggest that placental VLPs derive from IAPEz-int, and demonstrate their potential to traffic into maternal tissues, suggesting a role for these structures in maternal-fetal communication at the placental interface.

developmental biology↗

bioRxiv2023

Recent evolution of large offspring size and post-fertilization nutrient provisioning in swordtails

Organisms have evolved diverse reproductive strategies that impact the probability that their offspring survive to adulthood. Here, we describe divergence in reproductive strategy between two closely related species of swordtail fish (Xiphophorus). Swordtail fish and their relatives have evolved viviparity: they have internal fertilization and give birth to fully developed fry. We find that one species, X. malinche, which lives in high-elevation environments, has evolved larger offspring than its closest relative X. birchmanni and dwarfs the offspring size of other species in the genus. The larger fry of X. malinche are more resilient to starvation than their X. birchmanni relatives, hinting that the evolution of large offspring size may be an adaptation to the particularly challenging environments in which X. malinche are born. We find evidence that X. malinche achieves larger offspring size in part by continuing to provision their offspring over the course of embryonic development after fertilization, the first time this process has been documented in the Xiphophorus genus. Moreover, we observe differential regulation in the ovary of genes associated with maternal nutrient provisioning in other species that use this reproductive strategy. Intriguingly, these reproductive differences may drive an asymmetric hybrid incompatibility, since X. birchmanni mothers pregnant with F1 embryos give birth to premature and stillborn fry at an exceptionally high rate.

evolutionary biology↗

bioRxiv2019

Telophase correction refines division orientation in stratified epithelia

During organogenesis, precise control of spindle orientation ensures a proper balance of proliferation and differentiation. In the developing murine epidermis, planar and perpendicular divisions yield symmetric and asymmetric fate outcomes, respectively. Classically, division axis specification involves centrosome migration and spindle rotation, events that occur early in mitosis. Here, we identify a previously uncharacterized orientation mechanism that occurs during telophase, correcting erroneous oblique orientations that unexpectedly persist into anaphase. The directionality of reorientation--towards either planar or perpendicular--correlates with the maintenance or loss of basal contact by the apical daughter. While the conserved scaffolding protein Pins/LGN is believed to function primarily through initial spindle positioning, we now show it also functions actively during telophase to reorient oblique divisions toward perpendicular. The ability to undergo telophase correction is also critically dependent upon an LGN-independent pathway involving the tension-sensitive adherens junction proteins vinculin, a-catenin and afadin, and correction directionality is influenced by local cell density. Failure of this reorientation mechanism impacts tissue architecture, as excessive oblique divisions induce precocious differentiation. The division orientation plasticity provided by telophase correction may provide a means for progenitors to dynamically respond to extrinsic cues provided by neighboring cells in order to adapt to local tissue needs.

cell biology↗