On April 9, 2026, a groundbreaking study published in Science has unveiled the first-ever dynamic atlas of the brain vasculature's luminal surface proteome, identifying two novel regulators critical for maintaining the integrity of the blood-brain barrier (BBB). The research, led by Dr. Jiefu Li of the Howard Hughes Medical Institute (HHMI), introduces a revolutionary in vivo labeling technology that captures the previously "invisible" protein landscape of the brain's protective wall.

The blood-brain barrier acts as a fortress, shielding the brain from harmful substances. However, the proteins on its luminal surface—the very "locks" and "gatekeepers" controlling molecular traffic—have remained largely inaccessible, a scientific "dark matter." Dr. Li's team overcame this decades-old challenge by developing a Wheat Germ Agglutinin-peroxidase conjugate. Delivered via cardiac perfusion, this biological probe anchors to the vascular surface, enabling precise, in-situ biotin labeling of adjacent proteins without the need for genetic modification.

Using this innovative technique, the team mapped the cerebrovascular protein landscape across the entire mouse lifespan—from development to adulthood to old age. This dynamic map revealed key transitions: a shift from angiogenic factors to waste-exporting transporters during maturation, and a stiffening of the vascular surface coupled with upregulated pro-inflammatory pathways during aging.

From this rich dataset, the team identified two functionally distinct "guardians" of the BBB:

SLC7A1: An amino acid transporter critical in newborns. The study reveals a novel SLC7A1-NOS3 axis, where the protein provides arginine for nitric oxide synthesis, preserving barrier function in early life. Its loss causes severe barrier leakage in neonates but has no effect in adults.

HAL2: A hyaluronidase that acts as a lifelong guardian. Its absence leads to BBB breakdown at any age. The researchers demonstrated that HYAL2 maintains barrier integrity by regulating hyaluronic acid metabolism—a function conserved between mice and humans, highlighting its fundamental importance.

Behind this scientific breakthrough lies a powerful story of mentorship across generations. Dr. Jiefei Li (HHMI Investigator) is an alumnus (Class of 2014) of the Zhiyuan College. The co-first authors, Zijian Zhu (UCSF) and Yuxiang Zhang (Johns Hopkins), are also Zhiyuan alumni (Class of 2024 and 2020, respectively). This intergenerational collaboration, from "Class III" to "Class XIII" of the same college, culminated in this landmark discovery.

This work not only provides a transformative tool for vascular biology but also opens new therapeutic avenues for treating neurological disorders by precisely modulating the blood-brain barrier.

Link to the paper: https://www.science.org/doi/10.1126/science.aea2100