human immunodeficiency with microcephaly

Physiopathology

DNA double-strand breaks (DSBs) occur at random upon genotoxic stresses and represent obligatory intermediates during physiological DNA rearrangement events such as the V(D)J recombination in the immune system.

DSBs, which are among the most toxic DNA lesions, are preferentially repaired by the nonhomologous end-joining (NHEJ) pathway in higher eukaryotes.

Failure to properly repair DSBs results in genetic instability, developmental delay, and various forms of immunodeficiency. Here we describe five patients with growth retardation, microcephaly, and immunodeficiency characterized by a profound T+B lymphocytopenia.

An increased cellular sensitivity to ionizing radiation, a defective V(D)J recombination, and an impaired DNA-end ligation process both in vivo and in vitro are indicative of a general DNA repair defect in these patients.

Etiology

 germline mutations in the Cernunnos gene. Cernunnos/XLF represents a novel DNA repair factor essential for the NHEJ pathway. (16439204)

References

 Buck D, Malivert L, de Chasseval R, Barraud A, Fondaneche MC, Sanal O, Plebani A, Stephan JL, Hufnagel M, le Deist F, Fischer A, Durandy A, de Villartay JP, Revy P. Cernunnos, a novel nonhomologous end-joining factor, is mutated in human immunodeficiency with microcephaly. Cell. 2006 Jan 27;124(2):287-99. PMID: 16439204

 Buck D, Moshous D, de Chasseval R, Ma Y, le Deist F, Cavazzana-Calvo M, Fischer A, Casanova JL, Lieber MR, de Villartay JP. Severe combined immunodeficiency and microcephaly in siblings with hypomorphic mutations in DNA ligase IV. Eur J Immunol. 2006 Jan;36(1):224-35. PMID: 16358361