Stanford builds "xenocortical" mice with human organoids taking over ~92% of cortex

On Sept 17, Stanford's Sergiu P. Pașca lab published a landmark Nature study creating "xenocortical" mice: human stem cell-derived cortical organoids transplanted into genetically cortex-deficient (apallial) mice grew to occupy most of the host cortex and achieved long-term, large-scale integration with the mouse brain. Multiple posters called it a milestone for organoid and xenotransplantation research, and BBC covered the story.

Confirmed

• The study came from the Pașca lab; posters mention authors including Kevin Kelley, first author Konstantin Kaganovsky, Karl Deisseroth and Ivan Soltesz; the paper is open access.
• Method: genetically engineered apallial mice (@sterlingcrispin describes them as missing about 50% of the brain) received human neural organoid transplants into the vacated cortical cavity after birth; the study introduces the concept of "developmental xenocortication."
• After three months, 91.9% of cortex volume in measured animals consisted of human neural cells, and human neuron activity was recorded in living mice. Transplanted cells diversified into multiple cell types, forming organized circuits with brain-like activity.
• Per @BorisMPower, the mice could walk, learn and form memories; @NerdyRodent noted human cells connected with other mouse brain regions; @sterlingcrispin added that human cells partially rescued deficits caused by the genetic modification.

Why it matters

• Many psychiatric disorders occur only in humans and never naturally arise in mice; this model aims to fill that gap, as BBC reporting relayed by @NerdyRodent emphasizes.
• Per @zakkohane relaying Kevin Kelley, the goal is a system for causal, multiscale (molecule-to-behavior) study of human neurobiology.
• Per @anilkseth, the authors stress these animals are not "human-mouse hybrid consciousness" beings; the ethical boundaries are being debated in the field.

2026-09-17 ~ 2026-09-18 · 14 related posts

• [source] Stanford creates xenocortical mice with ~92% human-stem-cell cortex — anilkseth · 2026-09-17
• Human organoids fill 91.9% of cortex in engineered mice, Nature paper shows — anilkseth · 2026-09-17
• Human organoids grow to occupy most of mouse cortex in Nature xenocortical study — Dr_Alex_Crimi · 2026-09-17
• Human Organoids Grow to Occupy Most of Mouse Cortex in New Nature Paper — zakkohane · 2026-09-17
• [source] Stanford grows functioning human brain cells inside mice, Nature study targets psychiatric disease — NerdyRodent · 2026-09-17
• [source] Human neurons implanted in mouse skull learn to control the mouse body (Nature) — BorisMPower · 2026-09-17
• Nature study transplants human cortical organoids into mice with large-scale brain integration — adeelrazi · 2026-09-17
• Human brain cells colonize 90% of cortex in engineered mice, raising ethics alarms — sterlingcrispin · 2026-09-17
• Human Organoids Fill 91.9% of Cortex in Engineered Mice, Nature Paper Reports — ctjlewis · 2026-09-18
• Human Brain Tissue Grows Working Circuits Inside Mice in Bold Organoid Experiment — Dr_Singularity · 2026-09-18

4 near-duplicate retellings: adeelrazi · MannyKayy · Dr_Singularity · nathanbenaich