A translocation breakpoint disrupts the ASPM gene in a patient with primary microcephaly.
Primary microcephaly (microcephalia vera) is a developmental abnormality resulting in a small brain, with mental retardation. It is usually transmitted as an autosomal recessive trait, and six loci have been reported to date. We analyzed a translocation breakpoint previously reported in a patient with apparently sporadic primary microcephaly, at 1q31, where locus MCPH5 maps. The patient was lost to follow-up, and we sampled a maternal aunt who carried the familial translocation. FISH analyses showed that the insert of BAC clone RP11-32D17 spanned the breakpoint. The breakpoint was further located within a fragment of this insert corresponding to intron 17 of the ASPM gene, resulting in a predicted transcript truncated of more than half of its coding sequence. It is very likely that the proband carried a second ASPM mutation in trans, but he was not available for sampling and hence we could not confirm this hypothesis. Our observation adds to the mutation spectrum of ASPM in primary microcephaly, and is to our knowledge the second example of a constitutional, reciprocal translocation responsible for a bona fide autosomal recessive phenotype.
Service de Génétique Médicale, Hôpital Erasme, Université Libre de Bruxelles, 808 Route de Lennik, 1070 Bruxelles, Belgium.
Bruno
B
Pichon
Sophie
S
Vankerckhove
Georges
G
Bourrouillou
Laurence
L
Duprez
Marc J
MJ
Abramowicz
D002871:Chromosome Banding; D019457:Chromosome Breakage / Q000235:genetics*; D002878:Chromosomes, Human, Pair 1 / Q000235:genetics; D002894:Chromosomes, Human, Pair 4 / Q000235:genetics; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D008831:Microcephaly / Q000235:genetics* / Q000473:pathology; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics*; D014178:Translocation, Genetic
C467202:ASPM protein, human; D009419:Nerve Tissue Proteins