Truncation of NHEJ1 in a patient with polymicrogyria.
Polymicrogyria (PMG) is a common malformation of the human cerebral cortex for which both acquired and genetic causes are known. Although genetic heterogeneity is documented, only one gene is currently known to cause isolated PMG. To clone new genes involved in this type of cerebral malformation, we studied a fetus presenting a defect of cortical organization consisting of a polymicrogyric cortex and neuronal heterotopia within the white matter. Karyotype analysis revealed that the fetus was carrier of a balanced, de novo, chromosomal translocation t(2;7)(q35;p22). Cloning and sequencing of the two translocation breakpoints reveals that the chromosomal rearrangement disrupts the coding region of a single gene, called NHEJ1, Cernunnos, or XLF, in 2q35. The NHEJ1 gene was recently identified as being responsible for autosomal recessive immunodeficiency with microcephaly. Using quantitative PCR experiments, we show that a truncated transcript is expressed in the polymicrogyric patient cells, suggesting a potential dominant negative effect possibly leading to a different phenotype. We performed in situ hybridization on human embryos and showed that the NHEJ1 transcript is preferentially expressed in the telencephalic ventricular and subventricular zones, consistent with the phenotype of the affected individual. In the human adult central nervous system (CNS), NHEJ1 is mainly expressed in the cerebral cortex and in the cerebellum. The association of PMG with the disruption of its transcript suggests that, in addition to its recently uncovered function in the immune system, the NHEJ1 protein may also play a role during development of the human cerebral cortex.
Cantagrel
Vincent
V
INSERM, U491, Faculté de Médecine La Timone, Marseille, France.
Lossi
Anne-Marie
AM
Lisgo
Steven
S
Missirian
Chantal
C
Borges
Ana
A
Philip
Nicole
N
Fernandez
Carla
C
Cardoso
Carlos
C
Figarella-Branger
Dominique
D
Moncla
Anne
A
Lindsay
Susan
S
Dobyns
William B
WB
Villard
Laurent
L
D000818:Animals; D002540:Cerebral Cortex / Q000002:abnormalities*; D002828:Choristoma / Q000235:genetics / Q000378:metabolism; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005333:Fetus / Q000002:abnormalities; D006801:Humans; D017403:In Situ Hybridization; D017404:In Situ Hybridization, Fluorescence; D051379:Mice; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D014178:Translocation, Genetic
D004268:DNA-Binding Proteins; C508551:NHEJ1 protein, human; D012333:RNA, Messenger; D045643:DNA Repair Enzymes