Mapping a gene for familial situs abnormalities to human chromosome Xq24-q27.1

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Abstract
Ambiguous abdominal situs, asplenia/polysplenia and severe cardiac malformations characterize heterotaxy in humans. These anomalies result from the inability of the developing embryo to establish normal left–right asymmetry. We have studied an interesting family in which the heterotaxy phenotype segregates as an X–linked recessive trait. In order to map the heterotaxy locus (HTX), we have analysed 39 family members using highly–polymorphic microsatellite markers from the X chromosome. One of these markers, DXS994, shows no recombination with the disease locus in 20 informative meioses. Linkage analysis results in a maximum lod score of 6.37. Current genetic and physical mapping data assign the order of loci in Xq24–q27.1 as cen–DXS1001–(DXS994, HTX)–DXS984–tel. These results establish the first mapping assignment of situs abnormalities in humans.