[Gene localisation in 12q12 in Holt-Oram atrio-digital syndrome]

The Holt-Oram syndrome, first described in 1960, consists of non-cyanotic congenital heart disease, usually an atrial septal defect, arrhythmias and malformations of the upper limbs affecting the radial segment. The transmission of the syndrome is autosomal dominant with almost complete penetrance. The authors report the localisation of a genetic abnormality of the Holt-Oram syndrome on the long arm of chromosome 12 (12q21-q3) by analysis of linkage in 9 multiplex families (Zmax = 8.19 at locus D12S354). Multipoint analysis showed a genetic interval of 7 centimorgans containing a gene of the Holt-Oram syndrome between loci D12S84 and D12S79 (multipoint lod score, 10 g base 10 = 8.96). In situ hybridization of artificial yeast chromosomes containing the surrounding markers showed that a gene of the Holt-Oram syndrome is located in 12q23-q24. The genetic heterogeneity was demonstrated in 3 families of the Holt-Oram syndrome with polydactyly or without cardiac disease (homog-test: chi 2 = 13.28; p = 0.0001). The localisation of a gene of the Holt-Oram syndrome is, to the authors' knowledge, the first chromosomal localisation of a cardiac malformation with septal defects in man. The identification of this gene should open wide perspectives for genetic research of cardiac morphogenesis and clarify the molecular mechanisms which govern cardiac septation during embryogenesis.