Neurodevelopmental origins of structural and psychomotor defects in CXCR4-linked primary immunodeficiency

: Inborn errors of immunity (IEI), as congenital chronic disorders, are often associated with neurobehavioral symptoms, traditionally considered secondary to patient burden. Their origin, however, has yet to be addressed. Here, we found that IEI-associated genes are expressed in neural lineages during human brain development, and in the absence of immunological challenges, IEI mutations directly impair neurodevelopmental trajectories, leading to psychomotor defects. Warts hypogammaglobulinemia immunodeficiency myelokathexis (WHIM) mice-bearing a mutation causing Cxcr4 hyperactivation-show developmental foliation defects of the cerebellum correlating with sensorimotor and affective dysfunctions, which recapitulate the alterations described in patients. WHIM cerebella single-cell profiling revealed major transcriptional deregulation in granule cell progenitors, whose aberrant proliferation and migration induce foliation and circuit defects. AMD3100 intracerebroventricular injection rescues both morphological and behavioral defects, demonstrating their brain-specific and Cxcr4-dependent origin. Collectively, our findings highlight the relevance of neurodevelopmental implications underlying psychomotor IEI manifestations, broadening our understanding of these conditions beyond immune dysfunctions.