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

Here, by mapping the expression of PIDD genes in transcriptional datasets sampling the human brain across multiple areas and ages, we identified a notable regional enrichment in the cerebellum, which encompasses neuronal and glial subtypes, extending beyond the immune cells. Aiming at elucidating the impact of PIDD genetic alterations on brain development, we focus on WHIM syndrome, caused by CXCR4 mutations. Consistently with clinical reports on WHIM patients, magnetic resonance imaging and histological analysis performed on WHIM mouse model showed distinct cerebellar foliation deficits associated with mild motor impairment and anxiety-like behavior from early development. Despite the restricted expression of CXCR4 in rhombic lip-derived progenitors, single-cell profiling uncovered a pervasive transcriptional alteration across various cerebellar cell types, well beyond the cell-autonomous effects of the mutation on the granule lineage. Significant downregulation of genes involved in dendrite branching and axonal elongation molecularly defined the reduced arborization observed in WHIM Purkinje cells, which is associated with altered lobule-specific frequency patterns by high-density multielectrode array recordings. In utero intraventricular administration of CXCR4 antagonist AMD3100 - currently in clinical trials in patients - successfully rescued both morphological and behavioral defects. This unravels a direct effect of the WHIM-associated Cxcr4-Cxcl12 axis on compromised cerebellar assembly of motor and anxiety-associated circuits. Our findings underscore the contribution of the cerebellum to emotional distress while emphasizing the importance of considering neurological implications in the management of PIDDs.