# Columbia: amyloid fibers from semen carried RNA into sperm and mouse embryos in vitro

- Published: 2026-11-08 21:38 UTC
- Section: Life & Health › Biology & biochemistry
- Tags: amyloid fibers, RNA delivery, sperm RNA, seminal fluid, prostatic acid phosphatase, mouse embryos, cryo-electron tomography, Zuckerman Institute, paternal inheritance
- URL: https://realtech.media/news/rt-d531dba4ca73b50ce96b0981_columbia_amyloid_fibers/

**Protein fibers from semen bound RNA, entered sperm and raised its content in two-cell mouse embryos in laboratory fertilization. Natural fibers have not yet been tested.**

![Columbia: amyloid fibers from semen carried RNA into sperm and mouse embryos in vitro](https://realtech.media/media/2026/11/2b132c7f7677acdf.webp)
*sciencealert.com*

Researchers at Columbia University's Zuckerman Institute report that amyloid protein fibers from semen can bind RNA, enter sperm cells and help carry that RNA into mouse embryos after fertilization, according to sciencealert.com. The work was led by structural biologist Anthony Fitzpatrick and physiologist William Mallen and published in Molecular Cell. [1] The embryo experiments used laboratory-made fibers and added RNA, not natural conception. [1]

## How the fibers form and carry RNA

The team studied a fragment of prostatic acid phosphatase (PAP), an enzyme produced by the prostate. The fragment carries a positive charge and RNA a negative one. In the laboratory the two bound together, formed tiny droplets and then fibers containing RNA. [1] PAP fragments alone stayed in solution, while added RNA brought them together and sped up fiber assembly. [1]

These fibers have an amyloid structure but are built from a fragment of a semen protein, different from the proteins that accumulate in Alzheimer's disease. In semen they form outside cells in healthy men and can be taken apart again. [1] In human seminal fluid, the authors also found small RNAs in a fraction containing amyloid fibers; many identifiable sequences were fragments of transfer RNA. [1]

## Uptake by sperm and transfer to embryos

To track the fibers, the researchers attached gold particles to laboratory-made fibers and used bull sperm, whose cells are relatively large. Cryo-electron tomography showed labeled fibers inside the cells. [1] Additional electron microscopy and live-cell imaging supported this, and human and mouse sperm also took up the fibers. [1]

In laboratory fertilization with mouse sperm and eggs, sperm were exposed to fibers made from human PAP fragments. The fragments later appeared in two-cell embryos. [1] RNA labeled with heavier carbon and nitrogen isotopes reached embryos in larger amounts when fibers were present. [1] When the fibers carried RNA encoding a green fluorescent protein, embryos from sperm given RNA with fibers contained at least ten times as much of the protein as those given the same RNA without fibers. [1]

In separate tests, the protein clusterin accelerated RNA release from the fibers. Clusterin was also present in the embryos, but its role in releasing RNA there remains to be confirmed. [1]

## Limits of the study

No human embryos or natural conceptions were tested, and uptake estimates varied between measurement methods. [1] Fitzpatrick said the team has not yet shown whether natural fibers with their usual RNA cargo change anything in an embryo, and the fate of the fibers after delivery is unknown. [1]

## Sources

1. [sciencealert.com](https://www.sciencealert.com/amyloid-fibers-have-an-unexpected-role-in-sperm-scientists-discover)
2. [ua.news](https://ua.news/en/dovkolo-svitu/amiloyidni-volokna-dopomogli-dostaviti-rnk-do-embrioniv-mishei-sciencealert)

---

Source: RealTech, realtech.media — https://realtech.media/news/rt-d531dba4ca73b50ce96b0981_columbia_amyloid_fibers/