Analysis of X-chromosome inactivation in X-linked immunodeficiency with hyper-IgM (HIGM1): evidence for involvement of different hematopoietic cell lineages

The pattern of X-chromosome inactivation was analyzed, by means of two different DNA probes (pSPT-PGK and M27 beta), in several cell lineages derived from females belonging to a pedigree with X-linked immunodeficiency with hyper-IgM (HIGM1). Non-random X-chromosome inactivation was demonstrated in T cells, B cells, and neutrophils, but not in fibroblasts, of obligate carriers, suggesting that different hematopoietic cell lineages are primarily involved in HIGM1. Preferential inactivation of the paternally derived X-chromosome was demonstrated by analysis of segregation of the alleles defined by the pSPT-PGK and M27 beta probes. The possibility that the HIGM1 mutation may confer a proliferative and/or differential advantage to hematopoietic precursors carrying the mutated allele on the active X-chromosome is discussed.