Postnatal downregulation of Fmr1 in microglia promotes microglial reactivity and causes behavioural alterations in female mice.
Mehdi Hooshmandi, David Ho-Tieng, Kevin C Lister and 10 others
PMID 40055803WHAT IT FOUND
Early postnatal downregulation of Fmr1 in mouse microglia caused female mice to groom more, bury more marbles, and show novelty-seeking deficits.
Males were unaffected.
Key findings
01Downregulating Fmr1 in microglia during early postnatal development increased self-grooming and marble burying and impaired novelty seeking in female mice.
02The same early downregulation made female mouse microglia less branched and increased a phagocytic marker.
03Male mice showed no significant behavioural or microglial changes after early downregulation, and late downregulation only impaired novelty seeking in females without changing microglial reactivity.
STILL TO COME
How it was doneWhat they found
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What it does not show
This was a mouse genetic study, not a human therapy trial, so it cannot tell therapists whether any treatment works. Effects were seen mainly in female mice, and male mice showed no significant deficits in the tested behaviours. The authors confirmed microglial FMRP loss in the corpus callosum but not in other brain areas. Microglial morphology and phagocytic signal were assessed only in the cortex and hippocampus. The marble burying test cannot distinguish direct burying from walking or sitting on the marbles. The behavioural battery did not cover sensory function, memory, or novelty detection needed to fully characterise neurodevelopmental disorder-like behaviours.
Declared interests
Funded by Canadian Institutes of Health Research. No other conflicts of interest are stated.
The easy way to misread this
Do not read these mouse findings as evidence that a therapy for fragile X syndrome or autism works in patients. The study changed a gene in mouse microglia and tested mouse behaviours, not human treatment.