Unraveling the genetic architecture of the human mammillary bodies

Genome-wide association in 38,064 UK Biobank participants identifies 34 loci linked to mammillary body volume, with 26 novel loci, and meta-analysis yields 44 loci in 42,924 individuals.

• Why it matters: Mammillary bodies are central to hippocampal-diencephalic-cingulate emotion and memory circuitry, but their genetic basis and links to mental disorders were previously unclear.
• What they did: Structural MRI volumes were segmented with FastSurfer-HypVINN, followed by univariate GWAS and replication in the Rhineland Study (N = 4,860), plus multivariate hypothalamic subregion GWAS and cross-omics integration.
• The result: MEI1 and CAPZA1 emerged as key candidates, with genetically regulated MEI1 expression and circulating CAPZA1 protein levels partially mediating effects; genetic correlation and Mendelian randomization indicate a bidirectional relationship with major depressive disorder.

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